The Optic Nerve

The optic nerve (also known as cranial nerve II) is a continuation of the axons of the ganglion cells in the retina. There are approximately 1.1 million nerve cells in each optic nerve. The optic nerve, which acts like a cable connecting the eye with the brain, actually is more like brain tissue than it is nerve tissue.
visual pathway

As the optic nerve leaves the back of the eye, it travels to the optic chiasm, located just below and in front of the pituitary gland (which is why a tumor on the pituitary gland, pressing on the optic chiasm, can cause vision problems). In the optic chiasm, the optic nerve fibers emanating from the nasal half of each retina cross over to the other side; but the nerve fibers originating in the temporal retina do not cross over.

From there, the nerve fibers become the optic tract, passing through the thalamus and turning into the optic radiation until they reach the visual cortex in the occipital lobe at the back of the brain. This is where the visual center of the brain is located.

The visual cortex ultimately interprets the electrical signals produced by light stimulation of the retina, via the optic nerve, as visual images. A representation of parasympathetic pathways in the pupillary light reflex can be seen here: parasympathetic response.
blind spot

The beginning of the optic nerve in the retina is called the optic nerve head or optic disc. Since there are no photoreceptors (cones and rods) in the optic nerve head, this area of the retina cannot respond to light stimulation. As a result, it is known as the “blind spot,” and everybody has one in each eye.

The reason we normally do not notice our blind spots is because, when both eyes are open, the blind spot of one eye corresponds to retina that is seeing properly in the other eye. Here is a way for you to see just how absolutely blind your blind spot is. Below, you will observe a dot and a plus.




Follow these viewing instructions:

1. Sit about arm’s length away from your computer monitor/screen.
2. Completely cover your left eye (without closing or pressing on it), using your hand or other flat object.
3. With your right eye, stare directly at the above. In your periphery, you will notice the to the right.
4. Slowly move closer to the screen, continuing to stare at the .
5. At about 16-18 inches from the screen, the should disappear completely, because it has been imaged onto the blind spot of your right eye. (Resist the temptation to move your right eye while the is gone, or else it will reappear. Keep staring at the .)
6. As you continue to look at the , keep moving forward a few more inches, and the will come back into view.
7. There will be an interval where you will be able to move a few inches backward and forward, and the will be gone. This will demonstrate to you the extent of your blind spot.
8. You can try the same thing again, except this time with your right eye covered stare at the with your left eye, move in closer, and the will disappear.

If you really want to be amazed at the total sightlessness of your blind spot, do a similar test outside at night when there is a full moon. Cover your left eye, looking at the full moon with your right eye. Gradually move your right eye to the left (and maybe slightly up or down). Before long, all you will be able to see is the large halo around the full moon; the entire moon itself will seem to have disappeared.

Like any other ocular structure, certain pathologies can have an adverse affect on the optic disc and optic nerve. Although there are too many to list completely, a few will be included here.
optic atrophy

“Optic atrophy” of the optic disc (visible to an eye doctor looking inside the eye) is the result of degeneration of the nerve fibers of the optic nerve and optic tract. It can be congenital (usually hereditary) or acquired.

If acquired, it can be due to vascular disturbances (occlusions of the central retinal vein or artery or arteriosclerotic changes within the optic nerve itself), may be secondary to degenerative retinal disease (e.g., optic neuritis or papilledema), may be a result of pressure against the optic nerve, or may be related to metabolic diseases (e.g., diabetes), trauma, glaucoma, or toxicity (to alcohol, tobacco, or other poisons).

Loss of vision is the only symptom. A pale optic disc and loss of pupillary reaction are usually proportional to the visual loss. Degeneration and atrophy of optic nerve fibers is irreversible, although in some cases, intravenous steroid injections have been seen to slow down the process.
optic neuritis

“Optic neuritis” is an inflammation of the optic nerve. It may affect the part of the nerve and disc within the eyeball (papillitis) or the portion behind the eyeball (retrobulbar optic neuritis, causing pain with eye movement). It also includes degeneration or demyelinization of the optic nerve. There will be no visible changes in the optic nerve head (disc) unless some optic atrophy has occurred.

This condition can be caused by any of the following:

* demyelinating diseases (e.g., multiple sclerosis, postinfectious encephalomyelitis);
* systemic infections (viral or bacterial);
* nutritional and metabolic diseases (e.g., diabetes, pernicious anemia, hyperthyroidism);
* Leber’s Hereditary Optic Neuropathy (a rare form of inherited optic neuropathy which mainly affects young men, causing them to lose central vision);
* secondary complications of inflammatory diseases (e.g., sinusitis, meningitis, tuberculosis, syphilis, chorioretinitis, orbital inflammation);
* toxic reactions (to tobacco, methanol, quinine, arsenic, salicylates, lead); and
* trauma.

The condition is unilateral rather than bilateral. If the nerve head is involved, it is slightly elevated, and pupillary response in that eye is sluggish. There usually is a marked but temporary decrease in vision for several days or weeks, and there is pain in the eye when it is moved. Single episodes generally do not result in optic atrophy nor in permanent vision loss; however, multiple episodes can result in both.
papilledema

“Papilledema” is edema or swelling of the optic disc (papilla), most commonly due to an increase in intracranial pressure (often from a tumor), malignant hypertension, or thrombosis of the central retinal vein. The condition usually is bilateral, the nerve head is very elevated and swollen, and pupil response typically is normal.

Vision is not affected initially (although there is an enlargement of the blind spot), and there is no pain upon eye movement. Secondary optic atrophy and permanent vision loss can occur if the primary cause of the papilledema is left untreated.
ischemic optic neuropathy

“Ischemic optic neuropathy” is a severely blinding disease resulting from loss of the arterial blood supply to the optic nerve (usually in one eye), as a result of occlusive disorders of the nutrient arteries. Optic neuropathy is divided into anterior, which causes a pale edema of the optic disc, and posterior, in which the optic disc is not swollen and the abnormality occurs between the eyeball and the optic chiasm.

Ischemic anterior optic neuropathy usually causes a loss of vision that may be sudden or occur over several days. Ischemic posterior optic neuropathy is uncommon, and the diagnosis depends largely upon exclusion of other causes, chiefly stroke and brain tumor.
glaucoma

“Glaucoma” is an insidious disease which damages the optic nerve, typically because the “intraocular pressure” (IOP) is higher than the retinal ganglion cells can tolerate. This eventually results in the death of the ganglion cells and their axons, which comprise the optic nerve. Thus, less visual impulses are able to reach the brain.

In advanced glaucoma, the visual field in the peripheral retina is decreased or lost, leaving vision in the central retina (macular area) intact. This results in “tunnel vision.” Elevated eye pressure occurs when too much aqueous fluid enters the eye and not enough of the aqueous fluid is leaving the eye. Eye pressure can be measured by performing a “tonometry” test.

Normally, fluid enters the eye by seeping out of the blood vessels in the ciliary body. This fluid eventually makes its way past the crystalline lens, through the pupil (the central opening in the iris), and into the irido-corneal angle, the anatomical angle formed where the iris and the cornea come together. Then the fluid passes through the trabecular meshwork in the angle and leaves the eye, via the canal of Schlemm.

If the rate of aqueous fluid is entering the eye is too great, or if the trabecular meshwork “drain” gets clogged (for instance, with debris or cells) so that the fluid is not leaving the eye quickly enough, the pressure builds up in what is known as “open angle glaucoma.” It is more common with increasing age.

Open angle glaucoma, which tends to be a chronic and painless condition, also can be caused when the posterior portion of the iris, surrounding the pupil, somehow adheres to the anterior surface of the lens (creating a “pupillary block”). This can prevent intraocular fluid from passing through the pupil into the anterior chamber.

On the other hand, if the angle between and iris and the cornea is too narrow, or is even closed, then the fluid backs up because it cannot flow out of the eye properly. This causes an increased intraocular pressure in what is known as “closed angle glaucoma.” Typically, there is an acute (sudden), painful onset. It can be accompanied by the appearance of rainbow-colored rings around white lights.

An internal pressure more than that which the eye can tolerate can deform the lamina cribrosa, the small cartilaginous section of the sclera at the back of the eye through which the optic nerve passes. A deformed lamina cribrosa seems to “pinch” nerve fibers passing though it, eventually causing axon death. Untreated glaucoma eventually leads to optic atrophy and blindness.

Eye pressure is measured by using a “tonometer” (with the test being called “tonometry”), and the standard tonometer generally is considered to be the “Goldmann tonometer.” The normal range of intraocular pressure (IOP) is 10 mm Hg to 21 mm Hg, with an average of about 16 mm Hg. Typically, eyes with intraocular pressure measurements of 21 mm Hg or higher, using a Goldmann tonometer, are considered to be “ocular hypertensive” and are suspect for glaucoma.

However, although glaucoma typically is associated with elevated IOP, the amount of pressure which will cause glaucoma varies from eye to eye and person to person. Many people with glaucoma actually have IOP’s in the normal range (“low tension” glaucoma), possibly indicating that their lamina cribrosas are too weak to withstand even normal amounts of pressure. Conversely, many people with IOP’s which would be considered high have no evidence of glaucomatous damage.

Glaucomatous changes in the optic disk (optic nerve head) usually can be detected over time. If the optic cup within the optic disk increases in size over a period of months or years, if notching is observed anywhere around the nerve head rim, and/or if an asymmetry is observed between the optic cups of the two eyes, then that person may be considered to be a “glaucoma suspect.” In glaucoma, optic nerve rim atrophy and/or notching, with a corresponding visual field decrease, usually will occur in this order:

Optic Nerve Quadrant	Visual Field Loss
1.  Inferior Quadrant	Superior Field
2.  Superior Quadrant	Inferior Field
3.  Temporal Quadrant	Nasal Field
4.  Nasal Quadrant	Temporal Field

Visual field loss, caused by optic nerve damage, is measured by using a “visual field analyzer” or “perimeter,” especially by measuring and comparing changes over time. The procedure is known as “perimetry.” Most field loss due to glaucoma usually is not even measurable until 25% to 40% of the optic nerve’s axons have been destroyed.

Studies seem to show that the first fibers to die are the larger fibers, which primarily carry form and motion information, rather than the smaller fibers, which primarily detect light. Therefore, pattern discrimination perimetry (PDP), which requires detection of both form and motion, may be a better test for early glaucoma than conventional perimetry, which requires detection of spots of light.

In PDP, various locations of the retina are stimulated with a checkerboard pattern on a background of randomly moving dots. The more random the dot movements, the more difficult it is to continue to perceive the checkerboard pattern. Even a normal eye eventually will not be able to see the checkerboard when the dot movement is random enough.

The more advanced the stage of glaucomatous nerve damage, the less “noisy” the dots need to be for the checkerboard pattern to be indistinguishable from the background of moving dots. In effect, the PDP seems to be more sensitive than a standard perimeter in detecting early glaucomatous visual field losses.

Typically, the elevated pressure in open angle glaucoma can be controlled using glaucoma medications, which either decrease the production of aqueous fluid or else increase its outflow from the eye. However, closed angle glaucoma often requires surgical intervention to be controlled.


source link: http://www.tedmontgomery.com/the_eye/optcnrve.html

Retinal Detachment

What is Retinal Detachment?

Retinal Detachment is a serious condition where the retina detaches and is moved from its original position. If left without treatment, permanent vision loss will occur.

Symptoms of Retinal Detachment

Symptoms of retinal detachment may include the presence of increased eye floaters, light flashes, watery vision, a veil or curtain blocking your vision, or a sudden dramatic decrease of vision. Patients with these symptoms should contact their eye doctor immediately and be seen for an exam the same day if possible The sooner a retinal detachment is diagnosed, the better the chances of saving vision.

Retinal Detachment Treatment and Prevention

Pneumatic retinopexy is a treatment where a small gas bubble is injected into the eye. The gas bubble pushes the retina back into place. The bubble eventually dissolves and the retina has to be held in place by either cryotherapy, the use of nitrous oxide to freeze the retina in place, or laser to weld the retina back in normal position.In cases where these treatments do not work, another treatment using silicone oil to replace the vitreous gel can be performed. This process has many different results and more information can be found about the NEI supported clinical trials at http://www.nei.nih.gov/neitrials/static/study39.htm.

For more information on retinal detachment visit your eye care doctor or visit http://www.nei.nih.gov for more research. Materials on this page have been researched from the national Eye Institute.

Eye Cataracts

What is a Cataract?

A Cataract is the clouding of the eye's lens. The exact cause of cataracts is still uncertain but cataracts seem to form as we age. Besides age, other factors might include exposure to ultraviolet light, cigarette smoking, alcohol, and eating habits. According to the National Eye Institutes, "By age 80, more than half of all Americans either have a cataract or have had cataract surgery."

Types of eye cataracts

• Age Related Cataracts - occurs when protein clusters up in the lens and causes cloudiness or from the discoloration of the lens from aging
• Secondary cataract - forms after surgery from other eye disease like glaucoma or diabetic retinopathy
• Traumatic cataract - forms after eye injury
• Congenital cataract - present at birth due to birth defects, diseases, or other problems
• Radiation cataract - forms after major exposure to radiation

Symptoms and detection of cataracts

Warning signs of cataracts may include blurry vision or glare from car headlights especially at night. Sunlight or indoor overhead lighting may seem to be seem too bright or cause glare. You may notice that bright colors may appear dulled. Sometime cataracts can cause double vision, and you may actually find that you are frequently changing contact or eyeglasses prescriptions. These symptoms might also be signs of other eye related problems so it is best to get checked by your eye doctor if you are having any of these problems.The eye doctor will place drops in your eyes to dilate your pupils and perform a thorough eye exam and study the crystaline lens of your eye as well as to check the optic nerves and retina for changes that might be contributing to your vision complaints.The eye doctor will also perform a test called tonometry in order to measure the pressure inside your eye as one of the diagnostic tools for glaucoma.

Cataract Eye Surgery

The only effective treatment for cataracts is to have them surgically removed. Modern cataract surgery is one of the most frequently performed surgical procedures in the United States.When performed by an experienced cataract and lens implantation surgeon, it is also one of the most successful surgeries that you can have. Cataract surgery usually requires the replacement of the natural lens with an intraocular lens (IOL). The IOL replaces the natural lens that has been removed because it was cloudy and thus gives you better vision. Today, Ophthalmologists can actually replace the cloudy lens with an advanced technology intraocular lens such as Crystalens or ReSTOR which will correct not only your distance vision but your near and arms length vision as well. They can hardly be distinguished from your natural lens and can give you back the focusing ability you lost in your 40's when you became presbyopic. There are two main types of cataract surgery that are used today. They are called phacoemulsification and extracapsular surgery. In Phacoemulsification or "Phaco" , a tiny incision is made into the cornea and a computer assisted device emits ultrasound waves to breakup the lens. The cloudy natural lens is then removed and replaced with an IOL. In extracapsular surgery, a longer incision is made and the cloudy core of the lens is removed as a whole piece while any left over areas of the lens are sucked up. Complications of cataract surgery are unusual but may include infection, bleeding, pain, swelling, and sometimes even something called an "after-cataract".This is a condition where tissue surrounding the IOL becomes cloudy. Fortunately, an eye surgeon can easily eliminate the "after cataract" by using a laser and without any additional surgery. This procedure, called a YAG Laser Capsulotomy may be required to remove the after-cataract and is extremely effective and relatively quick and simple. In the vast majority of cases cataract surgery and lens implantation is performed in an outpatient setting and you will be able to have your cataract removed and a new lens implanted and be able to go home within a few hours. Most of the time you will be able to resume your normal work and recreational activities within just a few days.

Lowering the risk of cataracts or at least slowing down the formation of cataracts is something you can do as first step to your overall health. It is a good idea to get annual eye exams. Since people with diabetes are more likely to also form cataracts, they should get checkups more frequently. Wearing sunglasses or eyeglasses that block ultraviolet light is a good idea. Some research, although not conclusive, has suggested that smoking and use of some drugs like steroids increases formation of cataracts. Stopping smoking or at least decreasing the amount you smoke could help slow the formation of cataracts. Cataract formation can also be slowed by eating healthy foods. Eating green leafy vegetables and fruits high in Vitamins A, C, and E can slow the growth of cataracts.It is important to learn more about cataracts and their prevention. According to Vision Problems in the U.S., an article by the NEI and Prevent Blindness America, "...the federal government spends more than $3.4 billion each year treating cataract through the Medicare program." As you can see, cataracts are also a huge financial burden for all of us. For more information on cataracts visit your eye care doctor or visit http://www.nei.nih.gov for more research. Materials on this page have been researched from the National Eye Institute.

After Cataract Surgery

Almost immediately after surgery patients are able to see and go about their everyday activities. Your doctor will setup a few appointments to see you the next day after cataract surgery and schedule times after that to check up on your healing process. During this time the patient should be care not to bring upon any pressure to the eye especially during cleansing and little things you may be unaware of such as rubbing your eyes. You should receive eye drops that will help the pressure around your eye, your doctor should let you know how long to use it. Because of the surgery and eye drops you may find that you will have fluid discharge. Some people may experience pain, discomfort or itchy eyes. Your doctor may give you medication to help relive these symptoms.

Macular Degeneration

What is Macular Degeneration?

Age related macular degeneration (AMD) is a disease that affects the macula, a part of the retina that allows you to see straight ahead and in fine detail. AMD is the most common cause of blindness because its main risk factor is age. Other risk factors include people who smoke, people who have bad eating habits and are obese, people of white race, family history of AMD, and women have greater risk of developing AMD.

Forms of Age Related Macular Degeneration, including Drusens

Dry AMD, the most common type, occurs when light-sensitive cells in the macula degrade and central vision begins to slowly fade. Dry AMD has three stages. Early AMD, the first stage, has a presence of drusens, yellow deposits under the retina, but usually no vision loss or problem is detected. In Intermediate AMD, there are many medium sized drusens or large sized drusens present. In this stage, blurry areas may be present and it is more difficult to do regular task. In Advanced Dry AMD, the light-sensitive cells begin to degrade dramatically and a blurred spot may appear in the central of your vision. Atrophy may also be a factor in advanced stages. This spot may appear larger and become darker and it becomes almost impossible to see with clarity and detail. Dry AMD can evolve into Wet AMD.

Wet AMD is more severe and vision loss occurs more rapidly. In wet AMD, small, abnormal blood vessels form. These new blood vessels are very thin and fragile and will begin to break and leak. The blood and fluids eventually causes damage to the macula and causes rapid loss in vision. Although Wet AMD is less common, loss of vision occurs faster so it is essential to get it diagnosed as quickly as possible.

Macular Degeneration - Symptoms and Detection

Symptoms of Dry AMD include the presence of drusens that begin to enlarge. Another symptom is blurry areas in central vision. A symptom of Wet AMD is seeing straight lines as wavy ones.

A visual acuity test can help an eye care professional determine if any central vision is lost. An Amsler grid may also be used to detect AMD. In this test you cover one eye and stare at a black dot that has patterns of straight lines. If these lines appear wavy or are missing then AMD could be present.

Also view the video below

Treatment and Prevention of Macular Degeneration

There is no treatment to restore vision once AMD has reached its advanced stage. However there are methods to prevent the advancement of AMD from immediate stage to advanced stage. Taking a high-dose formulation of antioxidants and zinc slows progression of AMD significantly. According to the research done by the NEI "The specific daily amounts of antioxidants and zinc used by the study researchers were 500 milligrams of vitamin C, 400 International Units of vitamin E, 15 milligrams of beta-carotene (often labeled as equivalent to 25,000 International Units of vitamin A), 80 milligrams of zinc as zinc oxide, and two milligrams of copper as cupric oxide. Copper was added to the AREDS formulation containing zinc to prevent copper deficiency anemia, a condition associated with high levels of zinc intake." This high level of antioxidants is virtually impossible to achieve with daily diets or multi-vitamins.

Wet AMD is treated with laser surgery to destroy the new blood vessels before they cause any more damage. This process can also cause more vision loss as it damages nearby tissue. New blood vessels may for and more treatments may be needed. Another process called Photodynamic Therapy (PDT), which was approved by the FDA in April 2000, uses a special drug that is injected into the body. This drug attaches itself to the new blood vessels in the eye. A special laser is then focused on the eye which activates the drug and destroys the abnormal blood vessels in a painless manor. There maybe some after surgery precautions with this method so it is best to ask your eye care doctor about specific details.

Prevention of AMD includes lowering risk factors and eating healthy diets of antioxidants and zinc. Quit smoking and eating foods with Vitamins A, C and E could help reduce chances of developing AMD. Exercising and keeping healthy are always good preventive methods for all diseases. For more information on nutrition and eye care visit our eye care nutrition pages.

For more information on Age related Macular Degeneration (AMD) visit your eye care doctor or visit http://www.amdalliance.org/ or http://www.nei.nih.gov for more research. Materials on this page have been researched from the national Eye Institute.

Glaucoma

Glaucoma is a disease that damages the eyes' optic nerves. Damage does not become noticeable until significant damage has occurred and if not treated could lead to severe vision loss or even blindness. Glaucoma is usually present with high intraocular pressure, pressure in the eyes, and results in a loss of peripheral vision. Early detection through eye exams will greatly help slowing down the disease.

Forms of Glaucoma

• Normal-tension Glaucoma - occurs when there is optic nerve damage and loss of vision even with intraocular pressure within a normal range
• Angle-closure Glaucoma - Increase in eye intraocular pressure due either to too much fluid being produced in the eye or to fluid not being able to exit the eye due to a blockage of the meshwork inside the eye. This can cause pain, headaches, nausea, red eyes, blurred eyes and vision loss. According to the NEI, "This is a medical emergency. If your doctor is unavailable, go to the nearest hospital or clinic. Without treatment to improve the flow of fluid, the eye can become blind in as few as one or two days."
• Secondary Glaucoma - can form after eye surgeries or from certain medical conditions like diabetes
• Congenital Glaucoma - present at birth due to birth defects that hinders the flow of fluid out of the eye that causes cloudy, white eyes and sensitivity to lights
• Open-Angle glaucoma - the most common type of glaucoma, occurs when fluid drainage from the eye is hindered, causing intraocular pressure to increase above normal, thus damaging optic nerves and eventually leading to vision loss. Usually peripheral (side) vision is damaged first leading to tunnel vision and in time to blindness if not properly treated and monitored

Glaucoma Symptoms and Detection

Warning signs of glaucoma are different for each form. Glaucoma is usually not noticeable until significant damage has been done to the optic nerves. With open-angle glaucoma, the most common form, an increase in intraocular pressure and loss in peripheral vision are key signs. A tonometer is an instrument that measures pressure inside the eye. It can show abnormal pressure that causes damage to optic nerves. A dilated eye exam uses drops to widen the pupils to allow an eye care professional to check optic nerves for changes. A visual field test helps an eye doctor tell if any peripheral vision loss has occurred, which is a sign of glaucoma. A nerve fiber analyzer is an instrument that very precisely examines the nerve fibers of the optic nerve for damage.

Glaucoma Treatment and Prevention

he most conventional treatment for glaucoma is medicine that is taken as a pill or as eye drops. The medicine has one goal and that is to decrease eye pressure. These medications either decrease the amount of fluid produced or help the eye remove fluid easier. Glaucoma medication might interfere with other medication so it is a good idea to consult your doctor and let them know about all of the medications you are taking. There are several different types of glaucoma medication so your doctor may want to try another one if it conflicts with medication you are currently taking or causes unwanted side effects. For most people medicine is enough to control glaucoma. For others, surgery is the better option. Laser trabeculoplasty is another option for decreasing pressure in the eyes. In this option, an Ophthalmologist sends a laser beam into the meshwork where fluid drainage occurs,called the trabecular meshwork. The process increases the drainage area and lowers pressure. With Argon Laser Trabeculoplasty (ALT), the surrounding tissue in the meshwork is damaged and usually requires another session after a few years. Sometimes medication must also still be taken. With Selective Laser Trabeculoplasty (SLT), a specially designed laser emits a low-energy laser light that targets only melanin-containing cells in the trabecular meshwork. The laser is heated only enough to affect the opening of the meshwork and adjacent areas are not damaged. This allows for multiple re-treatments. Endoscopic CycloPhotocoagulation (ECP) is another process to help alleviate eye pressure if medication and laser trabeculoplasty are not effective. Unlike laser trabeculoplasty, ECP uses lasers to target the ciliary body that produce fluid. This causes less fluid to be produced and in effect lowers pressure. Lowering the risk of glaucoma or at least slowing down the progressive damage to optic nerves is the best preventive measure. It is important to get routine check ups because glaucoma is unnoticeable at first. Certain risk factors to watch out for include race, medical disorders, and family medical history. Glaucoma is more common in African Americans and Hispanic patients, especially with increasing age. People with diabetes or who have had eye surgery are also more likely to have glaucoma. A family history of glaucoma increases the risk that you could have glaucoma. If any of these factors relate to you, then you should definitely go for more frequent eye exams.

For more information on glaucoma visit your eye care doctor or visit http://www.glaucoma.com/ or http://www.nei.nih.gov for more research. Materials on this page have been researched from the national Eye Institute.

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