Thursday, September 23, 2010

5.8 Eyes and Vision

Physician's Notebooks 5 - See Homepage
Chapter 8 - The Eyes and Vision
This chapter can protect your vision into old age. It is pointed to youth who can start the program to keep perfect vision and to oldster who has problem with lens cataracts, cornea cell deficiency or retina. But also, to the reader seeking pure knowledge and understanding of systems. Read slowly, carefully and in small segments, and use search & find for your interest. Latest Update: 6 December 2018

Descending Column of Contents in Order of Appearance
Prevent/Protect Program to Preserve Vision
Structure of the Eye
Too Widely Set Eyes
Bulging Eyes
Sunken eyes
Eyebrow hair 
Bell's Palsy Eye
Sclera & Conjunctiva; Surface Cover of Eyeball
Cough Hemorrhage of Sclera
Foreign Body in Eye
 Cornea Transplants - A Personal Experience with DSAEK
Iris; Inflammation and Rim Color Change
Eye Color

The Iris, Pupil Size & the Eye Muscles
Testing Light Reflexes
Eye Pupils Description
Notes On Vision
newborn's eyes and vision are crucial
Myopia (Nearsightedness)

The Cornea in Vision
Preventive Advice on Use of Vision
About The Retina and the Start of the Visual Process
Eyeglasses and Use of Contacts
Testing Vision
Blindness and Very Poor Vision - Prevention
Age-Related Maculopathy
Eye Drops - use, types and reasons for
Eye Pressure Glaucoma
Eye Lens Cataract - a personal experience includes complications
Preventing cataract or slowing its progression
Brain Tumor Visual Loss
Visual Fields Test
Computer Replaces Eyes for Reading

Prevent/Protect Program to Preserve Vision: Poor vision verging into blindness is a result of, over a lifetime, exposing bare eyes to sun and other UV and to X-Rays; from smoking cigarettes or marijuana; from local trauma of banging, punches and pokes; from too much close up reading that is unrelieved by breaks for eye muscles relaxation; from an aging body tissue that is losing its ascorbate (vitamin C) anti-oxidant protective function against toxic oxidation; from the high glucose, in diabetics, and the high cholesterol body state due to over- and bad-eating; from use of eye-damaging medications like chlorpromazine tranquilizers, the tetracycline antibiotics, unnecessary systemic use of corticosteroid or even high dose aspirin; and, not least; from the tissue damaging effects of unrelieved body dehydration or local tissue overhydration. The program starts with awareness of the damaging factors and commonsense reversal or avoidance; and the practices are lifelong to prevent or slow cataracts, corneal edema, glaucoma, lens hardening, retinal detachment, and macular degeneration. The program is: 1) Anti-oxidant, accomplished by vitamin C, 1 to 2 grams with meal, 3 to 6 grams a day; 2) Strive for and then keep Body Mass Index 18 to 20 by healthy eating; 3) Avoid the damaging medications or excess dose; 4) Protect from sun by use of UV blocking sunglasses in areas and at times of high glare, by avoidance of unnecessary exposure, avoidance of tanning machines or salons and by daily use of long-visor cap; 5) Avoid x-ray in areas of eyes and, if x-ray is a must, request shield for eyes; and prefer MRI to CT for body slice imaging; 6) Keep body well hydrated by drinking at least one extra liter of water each morning and for older persons keep eye tissues moist by use of artificial tears daily; and 7) eat fresh fruits and vegetables, especially colored and unflavored grain cereals. I shall refer to the program as the "prevent/protect program".
Structure of the Eye
Except for its front 1/6th surface area, the eyeball is protected from trauma by the bones of the orbital cavity. It is a nearly perfect sphere except the front cornea curvature. In horizontal mid-plane cut, its front-to-rear, or anterior-posterior (A-P) length in adult is 24 millimeters (mm). One kind of myopia, or nearsightedness, is due to a too long A-P eyeball that prevents the light rays from a far object getting focused on the retina with the exactness needed for a clear image. In a newborn, the A-P is 17 to 18 mm, too short to allow a well-focused close-up vision. By puberty, the A-P is 20 mm and 7 years later it is the 24 mm adult size. 
The figure of an eyeball below is used often in the text.
(Best to use your magnifying glass for the inspection)

The figure is a drawing of a human left eyeball cut in its horizontal mid plane. It is as if the artist were looking down on a human head whose top had been sliced off horizontally exactly at mid level of the eyeballs. Note that the one part of the slice that does not coincide with a perfect circle is the front (top here) which curves forward as the cornea. If you look at your eyes in a mirror, you do not actually see the cornea because it is transparent. But you can estimate its periphery edges and size from the outer line of your eye color. Contact lenses are worn over the corneas to correct a cornea or lens curvature for incoming light image.
  The cornea is accessible surgically. By laser-ray cutting, it can be shaped to improve vision. When corneas become diseased they develop edema and vision gets misty. Cornea transplant from healthy donor is now frequently done and will be discussed & described.
   Look now at the iris. (In the figure, red) In this view you see it in only 1 plane so it appears like side-shades for the eye lens. But it is a circular membrane with central opening that outlines the dark eye-pupil. Note in the figure that the iris is anchored to eyeball sheath by the ciliary body on the periphery. Concentrate now on the ciliary body. (Name and pointer only on your right) It is connective tissue with muscle fibers (A few shown in the zonular space on right side of figure). The muscle fibers (in the zonular space) are attached at angles to the elastic connective tissue that supports the lens in place. At rest, these zonular fibers are elastically stretched and this pulls the soft lens of youth into a flatter shape so that it does not much deflect light rays. But when the zonular muscle fibers contract, it loosens the zonular tissue allowing the elastic lens to assume a more spherical shape and to focus incoming light to a shorter focal length and allows a person, while young to read and see images that need to be focused from close up for fine work. Later in life the lens loses its elasticity and does not become more spherical, or convex when one tries to read or focus on close-up image and this is the cause of need for reading glasses.
   The ciliary body and the iris muscle fibers are controlled by reflex effects of light and movement to make vision better. The iris has involuntary circular muscle fibers. Each fiber forms a circle running around the iris and when these fibers contract, the iris opening constricts and in the extreme it makes pinpoint narrow pupil like you see in an opium addict. This pupil narrowing assists one's fine, close up vision by cutting off peripheral light that causes achromatic error. The lengthwise, or radial iris fibers widen, or open up eye pupils. The pupil size is reflexly controlled by light (bright light narrows a pupil and dark widens it). Pupil size also reacts to neurotransmitter of sympathetic or parasympathetic nerve. The sympathetic nerve output floods body with epinephrine in fight or flight situation, and causes widened pupil. Oppositely, the parasympathetic neurotransmitter acetylcholine makes the narrow pupil seen in sleep or in other resting state. These effects also occur from drugs. (Morphine narrows pupils, cocaine widens; so the size of pupils may tell type of addiction or overdose) The iris constriction and dilation is important for sharpness of near visual image and the wideness of field of far off images. Pupil size also reacts to attempts to focus on near or far image. The pupils enlarge when we focus on far object and constrict for near object with equal light.
   The iris is pigmented by inheritance. A “pure” double-dose of pigment gives black eyes, a mixed dose of pigment gives brown eyes and sparse pigment gives blue eyes. No pigment at all gives colorless to very light yellow eyes seen in the albino mutation
   Now, in the figure, look at the lens. It must be transparent for vision; it is like a glass lens with front and back curvature. The rather rounded shape lens, the lens of near vision shown above - concentrates incoming light ray onto a point a short distance behind it – the image focus. In sharply focused vision the focal point should focus the image ray on the neuro-imaging cells in rear layer of eye – the retina, which is like photograph film in camera.
   In front, the cornea, iris and lens are contained in a fluid-filled space (in the figure, white space) between cornea in front and lens in rear with the iris dividing the space into anterior and posterior chambers. Within this space, clear fluid circulates, its flow running from posterior chamber to anterior chamber where it is absorbed back into the blood. When absorption in front is blocked or production of fluid filtrate in rear is excessive, the fluid in the space increases causing the high pressure disease called glaucoma, with blindness if not reversed.
   Note, behind the eye lens the large vitreous (glass-like) twin bodies. You are seeing only one plane but in the eyeball it is a globular clear jelly material and its function is to transmit light rays without distortion from lens to retina. If it goes cloudy, you go blind.
   Continuing backward and into rear eyeball, note the retina as the thin light-gray layer at rear rim of eyeball. The image light rays get focused on it and, in the pigmented rod and cone cells the photons of light get chemically converted to electrical signals and the signals are transmitted in optic nerve fibers that run on the surface of the retina (Not shown in the figure) and the combined fibers exit from rear pole of eye as the (in the figure) optic nerve. Note the optic nerve cup, or optic disc, at bottom of the diagram  These nerve fibers carry the visual image from many parts of the retina to the brain for processing.  The optic disc contains no retinal visual cells so it is a blind spot which gives important information to an examiner.
   “Sclera” is the whites of eyes. From the figure you can see it is actually the outer cover of the eyeball and continuous with the cornea in front and enveloping & backing up the retina in the rear. The choroid is the thin pigmented layer (shown in black in figure above) between retina in front and sclera behind. It stops all light rays like a black backing. Overlying the sclera, in its visible front portion, is a normally transparent thin membrane with tiny blood vessels. It is the “conjunctiva” and when its blood vessels get inflamed due to irritation or infection we see the red or bloodshot eye of conjunctivitis. 
(Note: for the neurology and neuroanatomy of the eye and vision, click 9.12 The Cranial Nerves - Smell/Vision/Eye/Face/Vi..., and scroll to, II. Optic Nerve)  
Get in front of well-lit mirror and inspect your eyes. Note their apart-distance: Too widely set eyes is hypertelorism, a sign of underlying genetic abnormality.

 Note eye prominence. Bulging eyes suggest hyperthyroidism while one bulging eye means tumor behind it. Sunken eyes mean dehydration. One sunken eye means damage to sympathetic nerve on same side (from tumor, infection, trauma).

Eyebrow hair normally varies with gender, ethnicity and age, but losing it in outer third of eyebrow may be clue to diagnose hypothyroidism (low thyroid function, opposite of hyperthyroid). Thickening of eyebrow (not from the bone but from skin & underlying soft tissue) is a sign of leprosy.

One droopy lid is a sign of damaged nerve. Droopy lids at end of day may give early hint of weakness from myasthenia gravis.
The Upper Eyelids are sexiest to women. The late Hollywood movie actor Robert Mitchum made a successful career from his heavy-lidded look.

   Upper eyelid has combined muscle that lifts lid as part of the voluntary eye opening or as reflex in eye closing that is part of a wink. Its voluntary muscle part is innervated by the oculomotor (Cranial Nerve III) nerve whose center is in the midbrain. The involuntary part is innervated by the sympathetic nervous system via nerve branch from superior cervical ganglia on same side of neck, with nucleus in lowest part of the brain. A condition whereby one upper lid becomes paralyzed resulting in one eye remaining wholly or partly covered by paralyzed upper lid while the other eye opens normally is caused by damage along the oculomotor nerve or else along the sympathetic nerve to the same side upper lid. If the disease is in the sympathetic nerve, the droopy lid will be associated with sunken eye, pinpoint pupil, and loss of sweating over same-side brow (Horner's syndrome). Paralysis of one upper eyelid without other symptom is of interest to neurologist because it serves to locate brain tumor in midbrain.
Now, concentrate on eyelid skin. Small, pale yellowish flat elevation means dangerously high cholesterol or high neutral fat in blood from genetic condition. Get blood test.
   Eyelids swellings may be sign of kidney disease that may end in dialysis. If sudden, after medicine or unusual food, it is due to hypersensitivity/allergy (lips and mouth). If you develop black and blue about eye after bang on head, it is sign of fracture and bleeding inside skull.
   Shut eyes tight. If one eye cannot be shut completely, it reveals damaged peripheral facial nerve from infection or surgery or else a brain tumor affecting central facial muscle (Cranial Nerve VII) control. The most common cause, Bell’s palsy, is part of complete paralysis of one side of the face (droopy half of face) due to damage of that side’s facial nerve.
   Blinking is a reflex that is important for keeping surface of eye moist and clean. Also, it rests internal eye muscles. But excessive blinking (>30 blinks per min.) seen in hyper-irritable sleepless state can be cause of car accident because it cuts vision time and interferes with reaction time to visual cue. Infrequent blinking (<6/minute) is seen in Parkinson disease and in prominent hyperthyroid eyes. The cornea blink reflex (touching cornea with cotton tip elicits blink) is used to test sensory Cranial Nerve V, its part that serves the external eye area. Eye blink conditioning is done by pairing an unconditioned stimulus that causes an eye blink (a puff of air in the eye) with the conditioned stimulus (could be a soft sound or any stimulus that does not naturally elicit an eye blink). After several sessions of the pairing, the conditioned stimulus alone will cause the eye to blink exactly like an unconditioned stimulus for eye blink.
   Also to mention is sty, the small infectious swelling treated almost since time began by mothers with warm soak.
Sclera & Conjunctiva; Surface Cover of Eyeball
Open your eyes wide and keep in mind you are looking at one sixth surface of an eyeball that continues curving back behind the eye socket and is attached by a stalk (optic nerve and blood vessels) to front of brain. When you look at eyeball surface between the eyelids, you see the eye-white surrounding the colored circular iris, which in turn surrounds a central black pupil. A yellowing of eye-white means impending or actual jaundice from liver disease, and is a useful early sign of hepatitis because it precedes skin yellow by a day. The eye-white yellowing means (yellow) jaundice impends. Certain chemical poisonings (silver salts make dull lead color) discolor the eye-whites to a dull gray.
   Put a finger to your cheek and pull down lower eyelid till you can see the red moist membrane on its underside which continues as transparent membrane over the eye-white and is called the conjunctiva. There are tiny blood vessels in it you cannot see, except when irritated by foreign body or infection; then the eye appears bloodshot, itchy and teary, and a doctor would say “conjunctivitis”. If one or both eyes redden and you do not have a cold, suspect irritation from a chemical, an eyewash, or a contact lens. If it happens just after or during catching cold, it is from the cold germ. Infectious conjunctivitis may start in 1 eye but will rapidly spread to the other; it is more fiery and called pinkeye. One type occurs in children during summer and comes from unclean swimming pool. Most conjunctivitis is minor and due to virus or allergy or irritant foreign body but a few cases are caused by bacteria (You will see yellow, irritating discharge) and these need medical eye examination and antibiotic. Any sexual connection resulting in conjunctivitis may be gonorrhea or herpes or Chlamydia infections.
Cough Hemorrhage of Sclera
Eye-white sclera hemorrhage can be seen as single flame-like red spot after a coughing fit. Alarming and not charming, it will go away after a week no matter what you do and only needs dark glasses to protect you from worried friends. But a spot-hemorrhage in eye-white not due to cough may be from infection on your heart valve.
Foreign Body in Eye
is from piece of dust under upper eyelid. Suspect it if one eye gets red and irritated. With help of friend, one thumb and index pulls on eyelash; with the other, make gentle downward pressure on upper eyelid skin and flip the lid. Then, using moist cotton tip and standing before a mirror, you or a friend can pick the dark speck off inner eyelid by touch. Foreign body on a cornea should be seen by eye specialist MD.
Cornea Transplants - a Personal Experience with DSAEK
The Cornea is the front window of vision. It is most important because it is exposed to, as first line receiver, trauma and damage from sunlight and other radiation. It must remain perfectly clear for potential 100 years of life. Also as outer convex, inner concave lens cap of vision, it provides much refractive power; and, although it cannot change shape, it can be altered by laser surgery as treatment of many types of visual defects. The cornea also consists of a periphery tissue that attaches it to the ciliary body at the base of the iris and has cells that nourish it and keep its state of hydration normal for maximal transparency. When the front cornea gets damaged - by burn or trauma or infection - it may become opaque and the eye is blinded. In that case, a full cornea transplant is possible thanks to dying donors and surgical technique and skill. Or when cornea endothelial cells are destroyed after a long life with too much exposure to sun or tanning salon, the cornea may become waterlogged by edema causing bad misty vision. Then, a special kind of cornea transplant, endothelial keratoplasty also known as EK, or in its more advanced form DSAEK (Descemet Stripping Automated Endothelial Keratoplasty) can restore clear vision.
  I learned the hard way that one's corneas must be protected during a long life. Recently I had cataract surgery and, it turned out, because of my lifelong poor treatment of my eyes I had lost the endothelial cells that water the cornea and because of that I got the cataract surgery complication, cornea edema. The whole affair may be entertainingly read by clicking 17.1a A Complication of Aging .
Iris; Inflammation and Rim Color Change
 Look at your iris in mirror and you will see its thin black outer rim within which is your distinctive eye color. In looking at an iris you are looking through your cornea and the fluid in the anterior chamber of the eye. The dark outer rim of iris sometimes becomes grayish in old age and then, if only an arc is involved, is called arcus senilis but if the whole periphery is involved it is annulus senilis. It is thought to be a sign of high blood cholesterol and minor risk-factor of heart disease. In poisoning by excess copper in blood, the rim becomes greenish yellow, an important sign of Wilson disease. A reddening of eye-white limited to a halo around the iris, with pain in eye is sign of iritis, of corneal injury, or of acute glaucoma – all serious.
The iris acts as the eye lens's front cover shade; its central opening is like a target bull’s eye and creates the black pupils we see looking at ourselves in mirror.
Eye Color
Iris pigment gives your eye its distinctive color. Dark (black to dark brown) eye has high melanin in iris; lighter brown to green eye has less, and blue eye least, excepting the very light yellow to colorless eye of an albino person, which lacks pigment altogether. Inheritance of dark eye color is dominant and not gender linked. Either a dark-eyed mom or a dark-eyed dad alone may give dark eyes to child; also a blue eyed child may be born of 2 dark eyed parents, but if both apparent parents of a dark eyed child are blue-eyed, it means at least one of the apparent parents of the dark eyed child is not the DNA parent. Albino eyes (colorless iris) are a mutation that if inherited is recessive. (One albino parent alone may not give albino eyes to child; it needs both parents albinos ) Albino eyes give high risk of skin cancer melanoma.
   Blue-eyed child has higher risk of birth defects because of defect in metabolism of the amino acid, phenylalanine. (So blue-eyed is medically inferior to black-eyed despite black-eyed Adolph Hitler’s Nazi idea)
The Iris, Pupil Size & the Eye Muscles
The iris functions like camera diaphragm; its circular muscle fibers contract in bright light to make pinpoint pupil, and its radial lengthwise fibers contract in low or absent light, dilating the iris and causing big pupil (wide-eye look). Degree of constriction or dilation is a reflex response to brightness or lack of light and it assists focusing on the visual image because, for high central focus on retina, a narrow image light ray (narrowed pupil) is best and, for dark, wide-depth vision, a wide field of incoming rays is needed. Narrowed pupils also limit light aberration's bad effects on vision.  The widened pupil gives greater depth focus explaining why a 3-D effect on video screen is best appreciated when watched in low light and low brightness. The reflex also protects against light damage.
   The pupil size is affected by the sympathetic nervous system and its hormone epinephrine (and drugs like cocaine). For pupil constriction the opposing parasympathetic nervous system and its hormone acetylcholine (and drugs like morphine) give the effect. A body state where sympathetic or parasympathetic dominates causes varying resting pupil size. For example, any stress gives a wide-eye look, and, oppositely, in deep sleep when the parasympathetic dominates, eye pupils are small diameter.
   In low light, attempting to focus on a near object will constrict your eye pupils. (Right & left pupils converge and constrict in focusing on finger being moved from far distance to tip of nose) Oppositely, in attempting to focus on a far object the eye pupils dilate. In latter case the pupils reverse convergence, diverge and dilate.
   The reaction of the pupils to focusing is called accommodation in contrast to direct light reaction to brightness of light in eye.
      Checking your own or someone’s pupils for direct light and accommodation is best done in dimly lit room big enough for focusing on an object 20 feet (c.6 meters) away. For observing yourself, use a mirror.  A thin-ray penlight is for testing reaction to bright direct light in 1 eye at a time.
   Testing pupil light reflex is a test of eye and brain because the pupil reactions are controlled from nerve nuclei in midbrain.
   First check your resting pupil in slightly darkened room (Just lighted enough to see pupil size). Right and left pupils in a normal adult should be equal size diameters and; in low light, 3 or 4 mm (1 mm is 0.04 inch, or 1/25th inch so 4 mm is c.1/6th inch). Unequal size pupils are abnormal and need neurology checkup. (But 20% of normal persons have an inequality of 0.3 to 0.5 mm) Right and left equally constricted pupils (3 mm to pinpoint) especially in low light may mean the person is taking a drug that narrows the pupils, probably an opioid. Oppositely, dilated pupils (>5 mm, wide-eyed) may mean a pupil-widening drug like cocaine but it may also be seen normally without drug when one is frightened or otherwise emotionally aroused.
   Normal age and other affect: If you could take a healthy person and look at his pupils in the same darkened room at intervals as he ages you would note, all other factors being equal, his pupils are big and wide in childhood and become smaller in old age. In coma, the finding of wide pupils that do not react to light is a sign of near death. If you find a person who seems to be asleep and you can gently lift one eyelid, the pupil ought to be narrowed compared to awake. A wide pupil in someone seeming to sleep means the person is faking sleep or has taken a drug like cocaine that dilates pupils, or has had brain stroke or other neurological disease affecting the pupils. Women tend to have slightly wider pupils than men under same conditions.
   Blindness or near blindness due to damage or disease in eye or its optic nerve will cause a dilated pupil in the blind eye. A person claiming to be blind whose pupil reacts directly to light may be faking or may have blindness that is coming from brain above the optic nerve. 
Testing Light Reflexes
An eye pupil exposed to a penlight in dark room should constrict quickly and strongly. This is the direct light reflex. The consensual light reflex is tested by shining the penlight into the right or left eye and, while cupping the other eye to shield it from the light, you observe the unexposed-to-light eye for pupil constriction, which normally should occur with intact crossover of the neural network. If one pupil reacts directly to the light while its opposite pupil does not give indirect reaction, there is a tumor or other lesion disconnecting the neural network in the brainstem between left and right eye-pupil nerves.
   Next, the person being tested should focus on an imagined object beyond the tip of his nose. As the object is brought toward the nose the eyes should converge and in low light, the pupils should narrow. This is the accommodation reflex. When the reflex fails (no pupil narrowing on convergence) yet the pupils narrow in response to bright direct light, it is sign of brain syphilis or other inflammation or damage of affected neural networks. (Brain syphilis can occur without any other symptoms so this could discover it)
   Each of the various pupil reflexes tests a different area of brain and its neural network, and a normal response is reassuring of good brainstem function.
   Anything that dilates a pupil, will raise internal eye pressure and be bad for glaucoma, while anything that makes pinpoint pupils will lower the pressure. Eye-drop medication that constricts pupils is treatment against the bad high-pressure eye effects of glaucoma.  
Eye Pupils Description
Now, in front of mirror, focus on your pupils. They are the black centers of eyes seen through the rim of the iris opening. Actually, what you see when you view these black circles is the dark surface, the retina at the rear far end of the cup of eyeball produced by room light that has passed through the transparent front part of the eye and been mostly absorbed by the retina pigment. Normal retina does not reflect much light so pupils appear nearly black. A change in one or both pupils to yellow-orange (cat-eye sign) or almost white indicates malignant tumor in eye, usually in infant with retinoblastoma. Also with severe cataract involving all of lens the pupil may appear gray or whitish.
Notes On Vision
Vision involves 1) the eye globe retina and its local bodies; 2) Cranial Nerve II (Optic Nerve) and connecting midbrain structures (Thalamus, Superior Colliculus, optokinetic nuclei); and 3) the cerebral cortex and its subcortical connections. Visual imaging should be described in serial order - from incoming image light waves to finished perceptual view. In this chapter we deal with the retina and its local connections, which includes the start of the optic nerve. The post-retina optic nerve and midbrain connection is dealt with in 9.12 The Cranial Nerves - Smell/Vision/Eye/Face/Vi..., and the visual function is in the Neurology of Sensation.
First, parental and pediatric attention to a newborn's eyes and vision are crucial because defects in newborn eye vision will have a permanent effect on the brain's processing of visual input and the potentially permanent bad effect, for example, of an infant cataract or severe cross-eye condition, on its later adult vision can be prevented or reversed only if it is promptly treated. (And see about this in the chapters on Child Raising in Notebooks 8 and Cranial Nerves in Notebooks 9)
For good vision the eye media for light transmission must be  transparent to image light waves. The light waves must pass through the cornea, the anterior chamber fluid, the lens, the vitreous jelly and, lastly, between nerve fibers and the cell layers of retina before striking the image-recording rod and cone cells in the outer retinal layer. A block to light-waves, such as clouding of cornea or opacity of lens from a cataract, will cause misty vision or, in worst case, blindness.
   Start, with thinking about every-day vision: reading and close up work, people's faces you see on the street and far vision. Also the printed letters on this page and the light that helps you to read. Page print must be large enough for one’s vision to focus on and contrasted enough with background page or bright screen to be clear. It may be brought to your eyes by reflected light, which may be sunlight or by artificial lighting in reading a book, or it may be transmitted by direct artificial light as when you read in the dark off a screen.
   If one has control over the image, one tries to make it large enough, contrasted enough and brightly lit enough for clarity. Much of every-day near vision is for imaging a printed page or video screen, where these conditions can be controlled. From that, keep in mind (as your visual function worsens with aging) that poor vision will be improved, and clarity too, especially when reading from a desk at night, by a good close-up 15- to 25-watt lamp and by good contrast, and by increased image size. Of these factors, lighting is most controllable in reading from a page, and contrast most controllable when reading off a screen. Proper lighting and contrast alone can improve reading much. If you are older than 65, try reading without usual reading glass using close-up adjustable 15- to 25-watt lamp (A too bright bulb, 40-watt or more will cause glare in a person with cataracts and make reading worse) with clouded white bulb light directed onto page. (Not bare bulb but one with reflector shield) You may see you can read that way without your reading glasses.
That, for practical simple factors! Now consider refraction of a visual image. It affects such reading, video watching or viewing the beautiful scenery of life.
   An image source like the print you now read is made of tiny points. Consider the curvature of your cornea and the curvatures of your eye globe's lens in refracting a visual image onto a focal point on your retina from distances in front of you. For best vision, the lens must be able to rapidly change its curvature when focusing on distant and then on near object, and its iris must be capable of constriction and widening (dilation) in response to changing light intensity and visual distance focus. Poor reading vision of old age is due to lens hardening and the lens's inability to change shape and is worsened by a cataract in the lens and by degeneration in the retina. The prevent/protect program at start of this chapter will prevent or slow lens hardening, and retina degeneration.
Simplified visual image focusing.

The “focal distance” in the above figure is the distance from the lens refraction of the visual image light rays to the point where all the refracted image rays come together. (In the figure, its length is much exaggerated; actually in an eye it is much shorter than the image distance) It is focused on a point in the retina for a clear image.
Note from the above figure the 3 elements: 1) a point visual image, 2) a biconvex curvature-changing refracting lens and 3) a receiving retina like a photographic plate. The biconvex lens is necessary because for clear image on retina, the diverging rays from the image's point-source close to the eye must be brought together to form the focused point on your retina, and, given the 24 millimeter front-to-rear diameter of the adult eyeball, it needs a lens of great enough convexity to angle-focus the image light ray so that the ray's projection forms an image point on the retina. The necessary distance between lens and retina in an adult human eye (“focal distance”) must accommodate the anatomic A-P length of the eyeball. (The above Figure ignores the fixed focusing power of the cornea. Actually the cornea adds much to our near vision and ability to read)
   What you see above is for close-up vision, as in reading from hand-held book or viewing a postage stamp.
   The system you see above would be unworkable for an actual person because everything is fixed. In such a system, the image would need to be transported to a set distance in front of lens or the lens to a set distance from the image so there would be no far or near vision; just single image to lens distance vision – quite inconvenient in the real world.
   Each pair of eyes, naturally, depends on change of its lens convexity to focus on images at varying distances in front of the eyes.
Myopia (Nearsightedness)
   In the previous section's last sentence lies the importance of the anterior-posterior eyeball length in common youthful myopia (nearsightedness, an inability to focus except on very near visual image). Childhood myopia should improve when the final adult eyeball length ends up 24 mm.
   Close-up vision is like the figure of the point image source with diverging light rays. Think of the image source as a new penny coin you hold in hand several inches before your eyes in order to read its inscription. First consider the affect of changing coin-to-eye distance at such close-up vision. The closer the coin approaches your eyes, the wider apart the image rays diverge from the coin and therefore the greater the image focal distance needed behind your lenses in order to refract the diverging rays from the image source. Without a lens that can change to greater convexity this means a loss of focus inside a possibly inconvenient near point. But the human lens before middle age can change. As you bring the coin closer to your eyes and you concentrate on keeping it in focus, a reflex mechanism causes the near-focus muscle fibers to contract allowing your malleable plastic-like lens to assume its naturally more spherical shape, better focusing the more coming-apart rays of a near image. But a point is reached where nearer, clearer vision is impossible because the lens has its limit of changeability into high convexity. You can test your limit right now by taking a coin or other small inscribed object, holding it at first 10 inches (25cm) in front of you, at which distance you (if younger than age 40) should make out its inscription and then bringing it slowly closer to your eyes. At 4 or 5 inches the inscription will be blurred because it has passed the focal near point limit of your vision. With age, the eyeball lenses become less changeable and by age 60 in all eyes the lenses have hardened and become fixed. Result is that an older lens cannot become more convex to accommodate near vision and an old person, bare eyed, becomes unable to read a book or to read similar small print off a video monitor at normally comfortable handhold or seating close-up distances and needs magnifying glass, eyeglasses, artificial implant lenses, corneal contact lenses or refractive cornea surgery to restore his youthful state.
Look again at the previous figure of the point image source. At the source the rays are very divergent but as one backs away they become progressively less divergent, and at a very far distance they are almost parallel. Such very distantly sourced far vision parallel rays obviously require less refraction than close-up divergent rays and our lenses accordingly shift to less convex (a flatter lens) shape as we shift gaze from near object to far. Also note that the “shift” to a flatter lens is the relaxed state where no muscles need to contract. So exercising far vision is mentally and physically relaxing. 
The Cornea in Vision
Consider the cornea. It and the lens are convex in front and therefore bring light rays more shortly together to focal point. But the eye lens naturally can change its convexity and refracting power, an ability that allows the shift from the relaxed far vision to focused near vision. The cornea cannot do that, and can only change when a surgeon operates on it or a technician shaves it with a laser. Some persons are born with abnormal cornea shape but more frequently the cornea becomes important as a way of correction for limiting the defects in an eye’s refracting power that are caused by a lens. Recently, corneal-shaving-and-shaping surgery has been perfected that allows for super-vision – to see clearly at 20 feet what normal vision persons can only see clearly at 8 feet or less. 
Preventive advice on use of vision: Your vision needs to be relaxed at intervals; a constant close-up vision is not only tiring, it fixes the visual muscles into a state of myopia. This is seen much in children. The visual relaxation is got in a low light setting with eyes relaxed, looking into the distance (not focused on a near object). Therefore if you are studying, take breaks and relax your eyes under low light and do an unfocused gaze into the distance. Children should be taught this as part of study routine.
Is a condition where small local irregularities in a cornea or lens prevent perfect focus in a wide visual field. Most astigmatism is mild and is either tolerated or corrected by special prescription glasses. With severe astigmatism one finds it hard to achieve clear vision in the full field in all directions. At night the simplest way to improve close up vision due to astigmatism is a directed light from clamp-on desk lamp for reading. The directed light works to improve astigmatic vision because it stimulates iris to constrict and narrows pupil opening making for narrower ray of image transmitting through cornea and lens. Since astigmatism is due to small area(s) of imperfection inside cornea or lens, a narrower image ray will tend to miss an imperfection or to go between it while a wider image ray can’t miss it and gets scattered. For far vision, special astigmatism contact lenses will correct it. In worst cases, corneal surgery may be needed. If you are told that astigmatism is the cause of your imperfect vision and may require contacts or surgery, always get a 2nd expert opinion at a University-HMO.
About The Retina and the Start of the Visual Process
The Retina is on the surface of the pigmented, neuron-connected rear cup of the eyeball. It is composed of cell layers, the outermost ("outer" here is furthest from the center of the eye globe) containing  - most outermost - the actual photo-receptor cells – called rods or cones. When excited by light, the photo-receptor cell passes the signal to the next inner cell in the light-signal transmission chain - the bipolar - which passes its signal to the next inner layer ganglion cell. From the ganglion cell the signal is transmitted via a fiber up to top surface of the retina where it right angles towards center of retina and joins millions of other ganglion-cell fibers to form the optic nerve aka Cranial Nerve II.
Figure shows a blown up micro of retina structure with black Rods and hollow white Cones shown in lowest (outermost) level and fibers that make the optic nerve at highest (innermost) level. Light waves penetrate from the outside down to the Rods and Cones.
  The Rods are super sensitive to low levels of light down to a single photon. They are mostly out towards the periphery, away from the retinal central cup, which contains only Cones. Rods effect  vision at night and only black & white vision. That is why astronomers have long noted a night time blind spot for direct focusing. And because Rods image black & white only and no color, all cats (no matter the colors) look gray at night. Cones are less sensitive to low light but more important in exact visual acuity. They are mostly located at the center of the retina in a depression called fovea. Three types of cone cells mediate color vision: short-wave, or S-type which transmits blue hues, medium-wave, or M-type which transmits green hues and long-wave, or L-type which transmits red hues.  

The Retinal Connections to the Optic Nerve and the Nature of Light & Dark Effects:
Referring to the above Figure, the light signal starts when light waves penetrate to the bottom of the retinal cup where there are 2 types of light-sensitive cells called Rods (A) and Cones (B) . The signal then passes back to bipolar cells (Red in the Figure) and then passes further back to the ganglion cells (Black and yellow in the above) which begin the optic nerve composed of millions of ganglion cell fibers that, as can be seen above, do a right angle and travel parallel over the surface of the retinal cup to the optic disc where the fibers gather together as the left and right optic nerves. (The optic nerve, or Cranial Nerve II, is further described in 9.12 The Cranial Nerves - Smell/Vision/Eye/Face/Vi...)
   The signal that light gives to the Rod and Cone cells is on or off depending on whether the Rod or Cone is an on or off type and also depending on whether the signal is effecting the center or off-center of the Rod or Cone receptive field. The on signal excites the cell and the off signal inhibits the cell and this excitation or inhibition is passed to the bipolar cell as more or less of the neurotransmitter glutamine. This arrangement of on and off light effect is important for delineating edges and shades of the image. Without it edges or shades would be lost from the image.
  It is important to understand that the light-sensitive cells are, in the absence of light-stimulation, in a state of constant excitement (constantly releasing an excess of glutamine) and that for an on cell, the light wave actually turns the glutamine release off and this turn-off starts the light signal on its way to the optic nerve. This state of tonic excitation is the default state of light-sensitive cells in the absence of any stimulation by light. It serves an important purpose. Without it, if the cell needed to have its engine turned on before light produced a signal it would take too much time for the visual process to be useful for our survival. As it is, it is like having an engine already turned on and warmed up at the start of a race. This is effected at the price of using-up energy; therefore, the retinal cells need a constant high supply of oxygen and nutrients to function properly.
The fibers run along the top retinal surface and come together as the optic disc in the rear pole of each eyeball and the disc is the origin of the optic nerve which carries the signals to midbrain thalamus relay, called the lateral geniculate nucleus, and then to the cerebral cortex and we see the image. (The posterior occipital cortex is responsible for creating the image in our mind and the other cerebral cortex lobes are important in thinking and reading and writing about images we see and reacting to them)
   Of the 2 types of photoreceptor cells, the rod is important in seeing low-lit object and depends on vitamin A. In vitamin A deficiency, an early sign is night blindness, also called evening or low-light blindness. The cone cell is responsible for sharpness of central vision in bright light and for color and is concentrated in a small circular area on the near central visual axis retina for high-definition vision, called the fovea. The fovea gives high clarity and color-discernment. In contrast to the other elements of clear vision - the cornea, the lens, the vitreous - which serve for transmission and refraction of light from the image, the retina imprints the image and sends it to the brain. It can be damaged by the same oxidizing toxins and sunlight but it also is subject to damage from blood supply and mechanical separation known as detached retina. A lifetime of careless vision, bad nutrition and exposure to environmental toxins or trauma leads to retinal disease such as detachment and the feared age-related macular degeneration. My left retina is worsened by epiretinal membrane, a degenerative cell secretion that prevents perfect visual acuity and was caused by a lifetime of exposure to sun and toxins.
           The retina also has light receptor cells that are not cones or rods and that are not involved in vision but rather send signals of light and dark, signaling the passage of time of day up into the brain's hypothalamus and pineal gland and are used to make the brain an internal clock and to control sleep and wake times. This subject is dealt with in the final chapter of Notebooks 9.
 (For more explanation of retina microstructure and optic nerve click 9.12 The Cranial Nerves - Smell/Vision/Eye/Face/Vi..., and scroll to, CN (Roman numeral) II, the Optic Nerve)
Eyeglasses and Use of Contacts
First, to separate reading glasses from distance glasses. The need for reading glasses should be your answer to: Is it hard to read normal print in good light at comfortable eye-to-page distance? A reader with aging eyes will find the use of low-watt, close-up desk lamp and a magnifying glass improves reading vision immensely. Also note ‘comfortable distance’ is a range. Arm's length is useful. Once you are forced to exceed that, reading glasses must be used. Eyeglasses for reading are lowest price from a 99-cent (equiv. low price outside USA) store using trial and error test before buying.  But if you read off a computer screen just adjusting size of print, type of font and contrast will work wonders for aging vision.
For distance or mid vision, if you drive a car or do work that requires well-focused mid- to far-vision, then for any defect you need prescription eyeglasses. First, get a vision test. Then shop around for lowest price eyeglasses. The “progressive” lenses, ie, a multifocal lens that ranges from far distance, at top of the lens, to close-up for reading, low in the lens looking downward, are too high price. Best buy are prescription glasses focused on your particular need.
            Contact Lenses: My assistant has had experience with contact lenses, which means a plastic or silicon lens that the user applies directly onto the cornea. Contacts come as either hard plastic or soft plastic. In general, soft plastic is less irritating so all things being equal, choose soft plastic. Reasons to use contact lenses; firstly, certain types of eye conditions where it is a must like severe astigmatism. Women in particular get contacts as alternative to the usual eye glasses for cosmetic reasons. An interesting reason is persons who are getting photographed especially models and movie actors choose contacts for the photography sessions because the eye glasses may give a bad reflection.
   Recently I had the experience of wearing a soft contact lens for 6 weeks and I did not experience any discomfort and at times forgot I had it on my eye. Severe astigmatism and other special visual conditions may require it, and a reader should check with eye doctor on that.
   About diopter-plus correction for reading. The plus number of the convex-concave reading lenses is the reciprocal of the meter distance in front of the lens from which light rays get refracted to a point on the retina. The +1 diopter lens gives a near focus 1 meter, or 100 cm and has no correction to an aging eye lens, a +2 D gives near focal distance 50 cm and a +3 diopter lens has strong correction bringing the near point reading focus to 33 cm. Myopic eyes have negative diopter correction, bringing the near focal point out from its too near natural condition.
Once more about close-up vision: Good light gives good sight!  And for reader: use magnifying glass for small print. And reading off a computer does wonders for aging vision.
Testing Vision
To test reading vision, try to read a page of normal size print. With aging, as the years pass the near-image focal point will be moving away from your eyes and time will come when you have to hold the book beyond arm length to read in natural light. This can be remedied in early stage by reading under closely directed low-watt cloudy bulb lamp.

Snellen chart test of far vision. The number 20 before the slash refers to the 20-foot (6 meter) testing distance, the number after the slash is max distance in feet at which the size letter should be correctly made out by someone with normal vision. Normal for distance visions should make out letter down to 20/20 line at 20 feet.
Snellen chart expresses visual acuity score in USA using foot distances (1 meter = 3.28 feet). This test is done with subject standing 20 feet (c.6 meters) from the chart in normal room lighting. Each eye is tested separately by covering untested eye. If you can read down to 20/20 level, you are normal for distance vision. 20/40 is good enough not to correct, depending on your work and play needs.
   If you already have corrective lenses, test first without and then with. If cause of poor vision is purely inability of lens proper convexity-curvature, it ought to be corrected by your corrective specs or pinhole vision. (Pinhole can be made by punching and slightly enlarging a pinhole in your calling card and using it to cover eye in test looking through it) But if cause is bad astigmatism or opacity before retina (cataracts, corneal edema or vitreous opacity) or retinal or neurological problem, correction may not be perfect. 
Blindness and Very Poor Vision - Prevention
Most of us when young take our good vision for granted. But take your vision away, and life is ruined. To keep good vision, start the prevent/protect program early before vision gets damaged.           Temporary blindness in one or both eyes with eye pain, if not part of migraine, may be from a transient ischemic attack (TIA) of a soon-to-come brain stroke or, in younger person, it is a 1st sign of multiple sclerosis.
   Blindness is so serious that all victims seek immediate medical care, but certain visual loss may be so transient (seconds) it may be either missed or ignored, especially when in one eye. Many strokes are preceded by brief visual blurring or loss interpreted as dizziness and not taken seriously by unaware person. 
   One remarkable, remedial cause of sudden blindness that signals by preliminary attack is retinal detachment. Here, victim will note sudden worsening of vision, flashing light and floating spots and it won't be transient. Risk factor is poorly treated diabetes or hypertension, also recent minor trauma to eye. Immediate eye surgeon consultation can prevent permanent visual loss.
Age-Related Maculopathy (Macular Degeneration)
Important in lost vision is age-related maculopathy, ARM (ARMD). Its symptom is loss of high-focus central vision. It is partly inherited so if your parent or sibling develops it you should consider yourself at high risk of getting it after the age of 50 and should take precautions. Its causes are one or a combination of the risk factors - smoking cigarettes, too much sunlight and UV rays in tanning, too high cholesterol, too high BP, bad nutrition that lacks anti-oxidants, especially not enough vitamin C, and a high blood sugar like in diabetes. What a person who will get it first notices is that when he glances at his Venetian blinds, especially the mini type, a part of them seems to be wavy or even missing. Then it gets worse and the outcome is often blindness. In ARM, there is degeneration of the visual cone cells. The victim notices inability to bring central image into fine focus. Its coincidence with aging, and the fact that the macula part of retina is served by only a single small end artery suggests its final common pathway to be narrowing of the small artery that serves the macula or the central visual part of the optic cup retina. Recent treatment is aflibercept (Eyelea) a monoclonal antibody but it is expensive ($1850 a dose in 2014), problematic (average 4 injections into eyeball every 3 months) treatment with irregular result. A better approach is to test for and prevent progression of ARM by a many-year policy of avoiding the risk factors and improving anti-oxidant nutrition. The following is the very useful description by a victim of ARM who has benefited by his very expensive, painful and inconvenient treatment by preserving good vision which otherwise would have ended with blindness.

"My Mother also suffered from MD and died of a stroke. My sister unfortunately was part of an early experimental drug treatment involving laser, It did not work and eventually did not get FDA Approval, she is now 95% blind and can only see shadows.  I was luckier because I got wet MD two years after hers and by that time Evastin had been approved and I was one of the first patients able to get it. After a few years I graduated to a superior product called Eyelea. I still have a leak from a vein in my left eye that we have a hard time to control. At the moment, I have to have shots every four weeks although eylea promises a six week effective treatment. The cost of these shots is terrible. Shots in NY cost an uninsured person $4800. each. Blue Cross and large health insurers pays the clinic $2200. and the patient pays his copay which usually runs to $50.00 for the same service. Since I travel extensively I have had to get that shot in different countries and have been charged $2200. in Canada, 2100 pounds in London, 1230 Euros in Paris and finally 2000 Euros in Spain. The shot itself cost around $1000 for the material.  Evastin was the result of the division of the original injection used to block the veins feeding tumors in internal organs; a bright ophthalmologist in Miami started dividing that material in 10 portions and successfully use it to block leaky veins in the eye lobe.The cost was then very reasonable at less than $500; that is Eyelea. However there were chances of contamination when the division of the material took place in the clinic's lab, and after an incident the FDA stopped allowing the private division and Eyelea was produced with skyrocketed prices. This injection can be very painful depending on the methodology followed by the practitioner and his innate care and ability. In that order pf minimal pain comes the Montreal surgeon followed by New York and then London. The worst painful injections I ever received  were in Paris where I wanted to tear my eye out of its socket half an hour after the 2 injections I got there. I never smoked nor did my sister or my mother. My cholesterol was always high but I cannot recall the number, I now take statins so it is under control. My mother and I suffered from High Blood pressure. It is now under control with help of pillEdits. My daughter does not have High Blood pressure."
    Here is the latest (Previous report about 2 years previous, age 88) from 27 Dec. 2017 at age 90: My macular degeneration requires an Eyelea injection every 5 weeks. It is very effective. His vision stabilized on the Eyelea injections.
Since ARM can be found by simple examination, start yearly eye specialist exam by age 50 because early diagnosis may spark strong preventive efforts, may slow the development and may prevent the very difficult treatment you read about here.
A high intake of fresh fruits and vegetables, which supplies vitamins A, C, E, and the minerals Zn and Cu, will help prevent or slow ARM. And see the prevent/protect program at start of chapter. For anti-oxidant ARM protection 2 grams vitamin C with meals is my advice.
Warning: The touted laser treatment of developed ARM has caused worse complications and not improved the condition. If you choose to experiment  by having a specialist do the laser, be sure to limit it to one eye at a time so you can see the bad result without going totally blind or else see a good result and then have the other eye done.
Eye Drops are good to discuss here. First, how to put a drop in your eye? Before anything wash hands and pull down lower eyelid to give max access to eye. Lie flat or sit or stand with eyes toward ceiling. Invert the eye dropper bottle and using your upper eyelashes as locator deliver the drop of fluid.  Eye drops are 6 types: Corticosteroid against inflammation or edema, the NSAID's anti-inflammatory, the eye pupil wideners used for improving vision in astigmatism, the eye pupil constrictors used to reduce internal eye pressure in glaucoma, the antibiotics against infection, and the artificial tears against dry eyes. Keep aware that corticosteroid and pupil-widener eye drops may worsen glaucoma because they may raise internal eye pressure. 

Eye Pressure Glaucoma
is high fluid pressure in anterior and posterior chambers of the eye leading to blindness from pressure on retina and cornea. Glaucoma is important to discover before damage is done to vision. Key to early discovery is getting eye-pressure measured yearly. It is easy and painless so start getting it done with yearly eye exam. And keep in mind: eye drops that dilate the eye pupil are bad for glaucoma. Corticosteroid eye drops are less problematic but used for long may have delayed effect in raising eye pressure. (Note I have been using 0.1% betamethasone c-steroid, a drop in eye 2 to 3 times a day every day 5 years now and regular checks show no increased pressure in the eye) 
Eye Lens Cataract
The eye's lens loses transparency with age. The localized loss of transparency is a cataract. It starts as a micro opacity in age 40's in each lens and slowly grows. Almost persons who pass age 80 will have had vision dimmed by cataracts. At age 78, I had been aware of cataracts in each eye for 11 years. My reading vision was not bad for age. I had moderate outward shift of near-focus point and got by with 2+ reading glasses using good light and helped by magnifying glass. The affect of the cataracts in the previous 3 years had become noticeable: increasing mistiness and glare in sunlight like seeing through a light mist, not so bad as to limit me but enough to worry me.
   When to get the cataract surgery? Cataract surgery today is easy. The technique is to remove the cataract leaving the capsule in place (the lens is in front of eye, just behind iris, biconvex and clear in youth inside a thin-wall capsule) and to implant an artificial lens with focal distance that allows comfortable reading and good intermediate distance vision. The results are good and give a bonus in restoring normal youthful visual acuity. Complications are infrequent but when one does occur it can lead to blindness. 
In June 2011, I decided to get the cataract surgery. I was stimulated by fear my misty vision might become worse. First I got expert opinion by an eye surgeonIt showed I had a complicating eye condition - my corneas had very low endothelial cell counts (Normally the count should be 500 to 1000; mine was zero). It meant a high risk of cornea edema (Water swelling of cornea that can cause worse misty vision than a cataract). I got a 2nd opinion by a top eye surgeon and decided to go ahead with the cataract surgery because my vision seemed to be worsening and because the surgeon said if I developed the post-surgery cornea edema he could do a second surgery, a DSAEK (Descemet's membrane Stripping Automated Endothelial Keratoplasty) to relieve the cornea edema. He advised the cataract surgery be done on one eye at a time so that in case I developed the complication I would not have complete visual loss in both eyes. On 16 Aug. 2011, I had my left eye cataract lens removed and an artificial lens implanted under local eye-drop anesthesia. It was painless with me awake, sitting and took 17 minutes. When the bandage was removed next day, I had clear vision in the left eye and could read and see perfect without eyeglasses. Also I noticed that the removal of the cataract and replacement of the lens by an IOL (implanted ophthalmic lens) had restored my appreciation of perfect colors especially blues and white background and the IOL gave a magnification to image objects 10%. But 36 hours after the surgery, my vision in the operated left eye became misty, worse than before the cataract surgery. I had got the predicted complication - cornea edema. Although disappointed I was not very disturbed as I had been told of the high risk. My surgeon advised me to wait a month, treating with corticosteroid eye drops and, if the cornea edema did not clear, to go ahead with a DSAEK. In September 2011, I went on the waiting list for a donor. The DSAEK needs a cornea with cells from a donor's eye; it requires a healthy, young donor - a person who dies by accident or non infectious, non-eye-related illness. 
I waited through 2 false alarms. (In Nov 2011. & March 2012, I was called but shortly after it was cancelled) Then, 8 June 2012, Friday, 10 months after getting on the list, I told to come in hospital 11 June, Monday, and I had the DSAEK transplant, 6PM that day.
The surgery was done lying flat on my back on operating table with me awake and using only eye-drop local anesthesia. I felt no pain. I did have a mild feeling of claustrophobia under the head drapes and near the end of the operation a feeling to urinate which became quite uncomfortable. So I advise anyone who will have this operation to be sure to empty bladder just before getting on the operation table. The operation took one hour. This is a cornea endothelial cell transplant so one's own cornea - the front visual window  - is not cut out but left in place. Only a small window incision is made in the periphery where the cornea attaches to the white of the eye, and the transplanted tissue with endothelial cells from the donor is inserted into the front chamber of the eye behind and applied to the native cornea rim. This part takes about 45 minutes of careful surgery. The final and very important part is the injection of a lighter-than-air bubble that with the patient positioned flat on back is put in the front chamber and rises so that it fits right in the inside concave curvature of the cornea and pushes up against the cornea keeping the transplanted tissue firmly against the cornea rim. Just after the surgery, it is very important for the operated patient to lie quietly flat on back, looking at a point on the ceiling 180 degrees up for at least 3 hours and even for the next 2 or 3 days it is important to be still although the patient is allowed to go to bathroom or sit up briefly to eat. If the head is not kept in that position, the air bubble may move off center and cause tissue disruption. In my case, they allowed a late supper 3 hours after the surgery and I ate heartily. But the next morning my surgeon checked and saw a small dislocation and it was necessary for him to inject a new air bubble in the treatment room nearby. He did that in a 10-minute procedure without pain. The rest of my hospital course was uncomplicated and I was discharged one week later and by 3 months after the surgery I could see clearly in left eye and read usual print without eye glasses but helped by a magnifying glass. 
On 4 December 2012, I had my right eye cataract removed and its lens replaced by IOL.  Again the initial result was good for the right eye but after several days its vision misted due to post surgery cornea edema. On 25 December 2012, I had DSAEK into cornea in right eye; however, this surgery had technical difficulties because of a nursing mistake that resulted in my not getting pre-operative Diamox (carbonic anhydrase inhibitor that lowers intraocular pressure and helps surgical success) and by 4 months after the surgery my surgeon said the surgery had been a failure. That was early April 2013 and I was put back on the list for another DSAEK, this time to be under general anesthesia (GA) because GA gives lowest intra-ocular pressure. On 4 June 2013, I got the call that a donor would be available and reported to the hospital in the morning 5 June and had the 2nd DSAEK on right eye under general anesthesia at 5:30 PM, awaking from the anesthesia at 8:30 PM. Post operative course was rapid (3 weeks), successful, and I was discharged 15 June and now, 2017, I have near 20/20 vision and no misty vision and read perfectly close up without eyeglasses.
  Lessons from my experience having cataract surgery with a high risk of post-op complication prompts the following below advice to readers who develop eye cataracts and are contemplating surgery. 
  •  Eye cataract surgery most of the time is easy, uncomplicated and good result but you should say to self: "What if I have complication and lose vision?" There should not be a feeling of rush to get the surgery or getting it just because you discover you have cataracts. The obvious symptom of cataract is misty vision, not noticeable for several years after cataract is discovered and it remains tolerable for many years. Less obvious but important to anyone who depends on appreciation of colors for livelihood or enjoyment is that cataracts make one's color sense go bad: Blues become less crisp and tend to fade into dull white; while crisp white turns yellowish. Looking up at a white cloud-flecked sunny blue sky, cataracts make the whole sky a dull white-yellow. Also keep in mind, you do not really risk blindness by waiting even years to get the surgery. Of course, persons who depend on perfect, clear vision because they drive cars or operate machines or for other aspects of work may benefit by having cataracts removed and replaced by IOL as soon as the cataract visual symptoms are noted. But others may wait to have the surgery. Also keep in mind, if you have the surgery when you do not really need it and it doesn't work, (as with my right eye) you have gone from a not very unpleasant pan into a much too warm fire. 
As soon as you learn of your cataract, get an independent 2nd opinion that checks your cornea endothelial cell count and a careful examination of your retinas to be sure you do not have cornea or retinal diseases that may complicate the result of your cataract surgery. If you have such conditions, go slow and get expert opinion, as I did, in your decision for cataract surgery. 
  Once you decide for surgery, do not allow both eyes to be done at one sitting or within days of the other eye's surgery. Allow at least several weeks recovery to be sure you have a good result in the one eye before going ahead with the second eye. 
  Leave the choice of the IOL to your cataract eye surgeon (Do not be swayed by recent hype for latest implantable lenses), who should be an experienced certified eye surgeon operating in a major medical institution.
Preventing cataract or slowing its progression: We have much practical preventive data about Why a cataract? First, the gradual inside-lens loss of anti-oxidant vitamin C (ascorbate) and the increase in sorbitol, a product of failed glucose metabolism that goes very high in diabetics.
Also toxic causes: exposure to UV in sunlight and skin tanning lamps, to x-ray; the physical trauma to the eye from blows and bangs, high iron in blood (too many iron pills, too much tonic), high LDL cholesterol, high blood sugar (poorly controlled diabetes, overweight).
   Under the medicines that cause or worsen cataracts in order of toxicity are the anti-psychotic chlorpromazine and its family of drugs, the tetracycline antibiotics like Achromycin, Doxycycline, et al., the corticosteroid family of drugs (eye drops no problem), and even too much aspirin.
   Considering these factors and that cataracts start in the age 40's and that, physically, cataract is the precipitation of concentrated protein out of solution in the partly hydrated lens, you the reader should be able to formulate your own prevent or slow cataract regimen of living. My good eye health advice - the protect/prevent program - that starts off this chapter ought to be followed as early as possible for life. 
Brain Tumor Visual Loss
is often not obvious. Its symptom is enlarging blind spot in one visual field. Eventually this becomes so large it is noticed because it harms good vision but it can be picked up early by neurologist testing visual field. Here is place to give simple self-test.

Visual Field Test
Get cotton-tip (Q-tip). Sit in well-lit room and fix gaze on a point 2 feet (0.7 meter) in front of tip of your nose. Start with left visual field and then do right side. Holding Q-tip at handle with white tip at eye level and starting at a point far to your left, outside the lateral limit of your left visual field, slowly move the white tip across left visual field from extreme left to right until it exits field of vision. (This may be repeated as many times as necessary to check test) Do not shift eyes while testing; keep them fixed on far spot in line at tip of nose. The normal blind spot is noticed as a wink-out of the Q-tip in your temporal visual field about 150 off central vision midpoint. In detecting an abnormal blind spot, look for difference between left and right blind spot. A grossly enlarged blind spot on one side makes obvious impression. This easily repeatable test can be useful if done regularly with. It does not rule out tumor but may pick it up at curable stage.

Computer Replaces Eyes for Reading: My pal Lou reads like a professor since he went blind because he is outfitted with a voice-over reading computer. Check it out on Internet or email me and I'll get your needed info direct from Lou.
End of Chapter. To read on next, now, click 5.(9-10) About Ears, Hearing, Balance

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