Eye Diseases - What you should know?

A cataract is a clouding of the eye's naturally clear lens. The lens focuses light rays on the retina , the layer of light-sensing cells lining the back of the eye , to produce a sharp image of what we see. When the lens becomes cloudy, light rays cannot pass through it easily, and vision is blurred.



Light rays entering an eye with a normal lens.



Light rays entering an eye with a cataract. When a cataract forms, the lens of your eye is cloudy, light cannot pass through it easily.



Mature cataract

What causes cataracts?

Cataract development is a normal process of aging, but cataracts also develop from eye injuries, certain diseases or medications. Your genes may also play a role in cataract development.

How can a cataract be treated?

A cataract may not need to be treated if your vision is only slightly blurry. Simply changing your eyeglass prescription may help to improve your vision for a while. There are no medications, eye drops, exercises or glasses that will cause cataracts to disappear once they have formed. Surgery is the only way to remove a cataract. When you are no longer able to see well enough to do the things you like to do, cataract surgery should be considered.

Cataract Surgery

In cataract surgery, the cloudy lens is removed from the eye through a surgical incision. In most cases, the natural lens is replaced with a permanent intraocular lens (IOL) implant.

What can I expect if I decide to have cataract surgery?

Before Surgery
To determine if your cataract should be removed, your ophthalmologist will perform a thorough eye examination. It is advisable to not wait for the cataract to mature i.e. become total as was previously believed because once mature, the cataract can raise the pressure of the eye resulting in lens induced glaucoma which can cause a permanent damage to the optic nerve. Before surgery, your eye will be measured to determine the proper power of the intraocular lens that will be placed in your eye.

The Day of Surgery
Surgery is usually done on an outpatient basis (day care surgery) in the hospital. When you arrive for surgery, you will be given eye drops and perhaps a mild sedative to help you relax. A local anesthetic will numb your eye. The skin around your eye will be thoroughly cleansed, and sterile coverings will be placed around your head. Your eye will be kept open by an eyelid speculum. You may see light and movement, but you will not be able to see the surgery while it is happening.

Under an operating microscope, a small incision is made in the eye. In most cataract surgeries, tiny surgical instruments like a probe (PHACOEMULSIFICATION PROBE) can break apart and remove the cloudy lens from the eye. The back membrane of the lens (called the posterior capsule) is left in place. This procedure is called phacoemulsification (Stichless cataract surgery). The term laser cataract surgery is a misnomer. The cataract is broken into small pieces using ultrasonic energy.

During cataract surgery, tiny instruments are used to break apart and remove the cloudy lens from the eye.

After removing the cataractous lens, an artificial lens called intraocular lens (IOL) is implanted inside the eye. The intraocular lens may be nonfoldable (requires an incision of 5.25 mm), foldable (requires an incision of 2.8 -3.2 mm) or rollable (requires an incision of 1-2 mm only). When a lens is implanted inside the eye, either no glasses or glasses of minor power are required after surgery. However glasses for near vision are usually required.

With the recent advancements in accommodative and multifocal lenses, the requirement of near glasses is also being minimized and it may be possible to do most of our daily routine activity without the aid of glasses.

                                           An intraocular lens (IOL) implant.

In cataract surgery, the intraocular lens replaces the eye's natural lens.

After surgery is completed, your doctor may place a shield over your eye. After a short stay in the outpatient recovery area, you will be ready to go home.

Following Surgery

You will need to:
* Use the eye drops as prescribed
* Be careful not to rub or press on your eye
* Avoid strenuous activities until your eye specialist tells you to resume them
* Ask your doctor when you can begin driving
* Wear eyeglasses or an eye shield, as advised by your doctor

You can continue most normal daily activities. Over-the-counter pain medicine may be used, if necessary.

Is a laser used during cataract surgery?
Laser surgery is not used in cataract removal surgery. However, the lens capsule (the part of the eye that holds the lens in place) sometimes becomes cloudy months or years after the original cataract operation in 20 % of cases. If the cloudy capsule blurs your vision, your ophthalmologist can perform a second procedure using a laser. No surgery is usually required. During the second procedure, called a posterior capsulotomy, a laser is used to make an opening in the cloudy lens capsule, restoring normal vision.

Posterior capsulotomy: a laser is used to make an opening in the cloudy lens capsule.

Will cataract surgery improve vision?
The success rate of cataract surgery is excellent. Improved vision is achieved in the majority of patients. Only a small number of patients continue to have problems following cataract surgery.

Complications after Cataract Surgery
Though they rarely occur, serious complications of cataract surgery are:

* Infection
* Bleeding
* Swelling
* Detachment of the retina

Call your ophthalmologist immediately if you have any of the following symptoms after surgery:

* Pain not relieved by nonprescription pain medication
* Loss of vision
* Nausea, vomiting, or excessive coughing
* Injury to the eye

Even if cataract surgery is successful, some patients may not see as well as they would like to. Other eye problems such as macular degeneration (aging of the retina), glaucoma or diabetic retinopathy may limit vision after surgery. Even with these problems, cataract surgery may still be worthwhile as visual loss attributable to cataract can be restored.

Diabetic eye disease is a group of eye disorders affecting the eyes of those with Diabetes .Retina is the most crucial part which gets affected by Diabetes. Retina is the delicate, light sensitive lining of the back of the eye. Diabetic retinopathy is one of the foremost causes of blindness due to any Systemic (Bodily) Disease.

Who gets Diabetic Retinopathy?
With the increase in the duration of diabetes, risk of developing diabetic retinopathy also increases. It is observed that about 80% of the people suffering from diabetes for more than fifteen years do have some damage present in the blood vessels of the retina. Severe and uncontrolled diabetes, fluctuating blood sugar levels, high blood pressure (Hypertension), high blood cholesterol and diabetic kidney are all conditions which predispose a diabetic to develop changes in the retina.

Pregnancy and high blood pressure may aggravate Diabetic retinopathy.

It is very important to know that the retina gets affected adversely when the blood sugar level comes down quickly. It is extremely important that diabetics do not panic when their blood sugar level goes up.

Blood sugar level should be allowed to come down slowly.

What are the stages of Diabetic Retinopathy? 
There are two main stages of Diabetic retinopathy. In the early stages, it is called Background Diabetic Retinopathy . In this stage, retinal blood vessels start leaking causing the retina to swell. In some cases, the leaking fluid collects in the central part of the retina. This condition is called Diabetic Maculopathy . This can lead to difficulty in reading, distortion in vision and other activities involving close concentration.

The advanced stage is called Proliferative Retinopathy . This is the most serious stage of
Diabetic retinopathy. In this condition, new branch like blood vessels start growing on the surface of the retina. These abnormal blood vessels can lead to various complications like bleeding in the eye, detachment of retina or glaucoma .

Proliferative Retinopathy affects upto 20% of all diabetics and can lead to very severe loss of sight resulting in blindness.

How does one detection Diabetic retinopathy?
RRegular eye check-up for Diabetic Retinopathy is a must for all diabetic patients. Fundus Fluorescein Angiography or FFA, which is a specialized technique, is also used to get finer details of the retinal blood vessels. In FFA, a fluorescent dye is injected through a vein in the arm. As this dye travels through the bloodstream to reach the retinal blood vessels, photographs are taken in quick succession. These photographs capture the details of the dye leaking from the abnormal blood vessels. This helps in diagnosing the stage of diabetes and the subsequent managment.

What is the importance of early detection and treatment in Diabetic retinopathy?
Most of the visual loss from Diabetic Retinopathy can be prevented, provided it is diagnosed early. But once the damage has occurred, the effects are usually irreversible. Early warning symptoms threatening and damaging the eyesight are rare in Diabetic retinopathy. It is quite common for a diabetic patient to have good vision without any realization of the changes happening in the retina. These changes if left untreated could lead to sudden blindness due to bleeding. It is recommended that all diabetics should get their retina checked once every 6 months just after diagnosis and then subsequently once every year.

What is the treatment for Diabetic retinopathy?
LLaser treatment or Laser Photocoagulation is the most common line of treatment in most sight threatening diabetic problems. It is very important to realize that laser treatment aims to save the existing sight level and not to make it better. Laser treatment is recommended to the patients who have swelling of the retina in the macular area or new blood vessel formation. Laser photocoagulation is used to seal the microanurysms that are leaking fluid into the retina. If new blood vessels are growing then more extensive laser treatment has to be carried out which is called the Pan Retinal Photocoagulation (PRP). PRP is carried out over two to three sittings spread over a few weeks. In most cases, laser treatment causes the new blood vessels to regress and the swelling to subside.

What is itrectomy and Vitreo Retinal Surgery?
Sometimes the new blood vessels bleed into the gel like centre (vitreous) of the eye. This condition called vitreous hemorrhage can lead to sudden loss of vision. If the vitreous hemorrhage is persistent, then a procedure called Vitrectomy is recommended. This is undertaken to remove the blood and scar tissue from the centre of the eye . Some Complicated diabetic retinal condition may require extensive surgeries known as Vitreoretinal surgery.

Some facts about laser treatment:
* It is an outpatient procedure and does not involve stay in the hospital.
* It does not require an incision.
* It usually does not cause much discomfort.
* It can be repeated, if required.
* It prevents further loss of vision but does not restore the already lost vision.

Macular degeneration is a deterioration or breakdown of the macula. The macula is a small area in the retina at the back of the eye that allows you to see fine details clearly and perform activities such as reading and driving. When the macula does not function correctly, your central vision can be affected by blurriness, dark areas or distortion. Macular degeneration affects your ability to see near and far, and can make some activities — like threading a needle or reading — difficult or impossible.

Although macular degeneration reduces vision in the central part of the retina, it usually does not affect the eye's side, or peripheral, vision. For example, you could see the outline of a clock but not be able to tell what time it is.

Macular degeneration alone does not result in total blindness. Even in more advanced cases, people continue to have some useful vision and are often able to take care of themselves. In many cases, macular degeneration's impact on your vision can be minimal.

What causes macular degeneration?
Many older people develop macular degeneration as part of the body's natural aging process. There are different kinds of macular problems, but the most common is age-related macular degeneration (AMD). Exactly why it develops is not known, and no treatment has been uniformly effective.

The two most common types of AMD are "dry" (atrophic) and "wet" (exudative):

"Dry" macular degeneration (atrophic). Most people have the "dry" form of AMD. It is caused by aging and thinning of the tissues of the macula. Vision loss is usually gradual.

"Wet" macular degeneration (exudative). The "wet" form of macular degeneration accounts for about 10 percent of all AMD cases. It results when abnormal blood vessels form underneath the retina grow either behind or into the retina. These new blood vessels leak fluid or blood and blur central vision. Vision loss may be rapid and severe.

Deposits under the retina called drusen are a common feature of macular degeneration. Drusen alone usually do not cause vision loss, but when they increase in size or number, this generally indicates an increased risk of developing advanced AMD. People at risk for developing advanced wet AMD in the eye have significant drusen, prominent dry AMD, or abnormal blood vessels under the macula in one eye ("wet" form).

                                                       DRY AMD WET AMD

What are the symptoms of macular degeneration?
Macular degeneration can cause different symptoms in different people. The condition may be hardly noticeable in its early stages. Sometimes only one eye loses vision while the other eye continues to see well for many years. But when both eyes are affected, the loss of central vision may be noticed more quickly.

Following are some common ways vision loss is detected:

* Words on a page look blurred
* A dark or empty area appears in the center of vision
* Straight lines look distorted, as in the following diagram

                                      

                                                Amsler grid with wavy lines

How is macular degeneration diagnosed?
Many people do not realize that they have a macular problem until blurred vision becomes obvious. Your ophthalmologist can detect early stages of AMD during a medical eye examination that includes the following:

* A simple vision test in which you look at a chart that resembles graph paper (Amsler grid)

* Viewing the macula with an ophthalmoscope

* Taking special photographs of the eye called fluorescein angiography to find abnormal    blood vessels under the retina

How is macular degeneration treated?

Nutritional Supplements
Though the exact causes of macular degeneration are not fully understood, antioxidant vitamins and zinc may reduce the impact of AMD in some people.

A large scientific study found that people at risk for developing advanced stages of AMD lowered their risk by about 25 percent when treated with a high-dose combination of vitamin C, vitamin E, beta carotene and zinc. It is very important to remember that vitamin supplements are not a cure for AMD, nor will they restore vision that you may have already lost from the disease. However, specific amounts of these supplements do play a key role in helping some people at high risk for advanced AMD to maintain their vision. You should speak with your ophthalmologist to determine if you are at risk for developing advanced AMD, and to learn if supplements are recommended for you.

Laser Therapy, PDT and Anti-VEGF Treatments
Certain types of "wet" macular degeneration can be treated with laser procedure (Focal Photocoagulation) a brief outpatient procedure that uses a focused beam of light to seal the leaking blood vessels that damage the macula.

For blood vessels which lay at the centre of the retina the fovea a treatment called photodynamic therapy (PDT) uses a combination of a special drug and special laser called dye laser to destroy the leaking blood vessels. This special procedure selectively damages the abnormal blood vessels without damaging the photoreceptor (Sensors) on the retina (fovea).

A newer treatment modality is giving excellent result in management of WET AMD. It targets a specific chemical in your body that is critical in causing abnormal blood vessels to grow under the retina. This chemical is called vascular endothelial growth factor (VEGF).

Anti-VEGF drugs block the trouble-causing VEGF, reducing the growth of abnormal blood vessels and slowing their leakage. This is probably the only treatment for WET AMD which actually improves the vision.

These procedures may preserve more sight overall, though they are not cures that restore vision to normal. Despite advanced medical treatment, many people with macular degeneration may still experience some vision loss.

Adapting to Low Vision
To help you adapt to lower vision levels, your ophthalmologist can prescribe optical devices or refer you to a low-vision specialist or center. A wide range of support services and rehabilitation programs are also available to help people with macular degeneration maintain a satisfying lifestyle. Because side vision is usually not affected, a person's remaining sight is very useful. Often, people can continue with many of their favorite activities by using low-vision optical devices such as magnifying devices, closed-circuit television, large-print reading materials, and talking or computerized devices.

Testing Your Vision with the Amsler Grid
You can check your vision daily by using an Amsler grid like the one pictured here. You may find changes in your vision that you wouldn't notice otherwise. Putting the grid on the front of your refrigerator is a good way to remember to look at it each day.

Amsler Grid

To use the grid:
* Wear your reading glasses and hold this grid 12 to 15 inches away from your face in good    light
* Cover one eye
* Look directly at the center dot with the uncovered eye
* While looking directly at the center dot, note whether all lines of the grid are straight or if    any areas are distorted, blurred or dark
* Repeat this procedure with the other eye
* If any area of the grid looks wavy, blurred or dark, contact your ophthalmologist    immediately

You may sometimes see small specks or clouds moving in your field of vision. They are called floaters. You can often see them when looking at a plain background, like a blank wall or blue sky.

Floaters are actually tiny clumps of gel or cells inside the vitreous , the clear jelly-like fluid that fills the inside of your eye.

                           
Although the floaters appear to be in front of the eye, they are actually floating in the vitreous fluid inside the eye.

While these objects look like they are in front of your eye, they are actually floating inside. What you see are the shadows they cast on the retina , the nerve layer at the back of the eye that senses light and allows you to see.

Floaters can have different shapes: little dots, circles, lines, clouds or cobwebs.

What causes floaters?
When people reach middle age, the vitreous gel may start to thicken or shrink, forming clumps or strands inside the eye. The vitreous gel pulls away from the back wall of the eye, causing a posterior vitreous detachment . It is a common cause of floaters. Other causes could be trauma, inflammation and myopia.

Posterior vitreous detachment is more common for people who:

* Are nearsighted;
* Have undergone cataract operations;
* Have had YAG laser surgery of the eye;
* Have had inflammation inside the eye

The appearance of floaters may be alarming, especially if they develop suddenly. You should also see an ophthalmologist immediately if you suddenly develop new floaters.

Are floaters ever serious?
The retina can tear if the shrinking vitreous gel pulls away from the wall of the eye. This sometimes causes a small amount of bleeding in the eye that may appear as new floaters.

A torn retina is always a serious problem, since it can lead to a retinal detachment. You should see your ophthalmologist as soon as possible if:

* even one new floater appears suddenly;
* you see sudden flashes of light.

If you notice other symptoms, like the loss of side vision like a curtain or shadow, you should see your ophthalmologist immediately as this suggests a retinal detachment. This is a serious condition which causes sudden loss of vision which is at times not fully retrievable even with surgical Management.

Retinal tears can result in a retinal detachment Retinal detachment in the upper part of retina

                    Laser barrage around the tear can prevent a retinal detachment

What can be done about floaters?
Because you need to know if your retina is torn, get yourself examined by your ophthalmologist if a new floater appears suddenly.

Floaters can get in the way of clear vision, which may be quite annoying, especially if you are trying to read. You can try moving your eyes, looking up and then down to move the floaters out of the way.

While some floaters may remain in your vision, many of them will fade over time and become less bothersome. Even if you have had some floaters for years, you should have an eye examination immediately if you notice new ones.

What causes flashes of lights?
When the vitreous gel rubs or pulls on the retina, you may see what look like flashing lights or lightning streaks. You may have experienced this same sensation if you have ever been hit in the eye and seen "stars."

When the vitreous rubs or pulls on the retina, it creates a sensation of flashing lights.

The flashes of light can appear off and on for several weeks or months. As we grow older, it is more common to experience flashes. If you notice the sudden appearance of light flashes, you should visit your ophthalmologist immediately to see if the retina has been torn.

How are your eyes examined?
When an ophthalmologist examines your eyes, your pupils will be dilated with eye drops. During this painless examination, your ophthalmologist will carefully observe your retina and vitreous.

Floaters and flashes of light become more common as we grow older. While not all floaters and flashes are serious, you should always have an eye examination by an ophthalmologist to make sure there has been no damage to your retina.

Glaucoma is a disease of the optic nerve — the part of the eye that carries the images we see to the brain. The optic nerve is made up of many nerve fibers, like an electric cable containing numerous wires. When damage to the optic nerve fibers occurs, blind spots develop. These blind spots usually go undetected until the optic nerve is significantly damaged. When the entire nerve gets destroyed the person would go blind.

Early detection and treatment by your ophthalmologist are the keys to preventing optic nerve damage and blindness from glaucoma. Loss of sight from glaucoma can often be prevented with early treatment.

What causes glaucoma?
Clear liquid called aqueous humor circulates inside the front portion of the eye. To maintain a healthy level of pressure within the eye, a small amount of this fluid is produced constantly while an equal amount flows out of the eye through a microscopic drainage system. (This liquid is not part of the tears on the outer surface of the eye.)

Because the eye is a closed structure, if the drainage area for the aqueous humor — called the drainage angle — is blocked, the excess fluid cannot flow out of the eye. Fluid pressure within the eye increases, pushing against the optic nerve and causing damage.

Clear liquid called aqueous humor is constantly being produced within the eye (left). If the drainage angle of the eye is blocked, fluid cannot flow out of the eye (right).

What are the different types of glaucoma?

Chronic open-angle glaucoma:
This is the most common form of glaucoma. The risk of developing chronic open-angle glaucoma increases with age. The drainage angle of the eye becomes less efficient over time, and pressure within the eye gradually increases, which can damage the optic nerve. In some patients, the optic nerve is sensitive even to normal eye pressure and is at risk for damage. Treatment is necessary to prevent further vision loss.

Typically, open-angle glaucoma may have no symptoms or vague symptoms like headache or frequent change of power of glasses, etc in its early stages and vision remains normal. As the optic nerve becomes more damaged, blank spots begin to appear in the field of vision. You typically won't notice these blank spots in your day-to-day activities until the optic nerve is significantly damaged and these spots become large. When the entire nerve gets destroyed the person would go blind.

Closed-angle glaucoma:
Some eyes are formed with the iris (the colored part of the eye) too close to the drainage angle. In these eyes, which are often small and farsighted, the iris can be pushed into the drainage angle and block it completely. Since the fluid cannot exit the eye, pressure inside the eye builds rapidly and causes an acute closed-angle attack.

Symptoms may include:

* Blurred vision;
* Severe eye pain;
* Headache;
* Rainbow-colored halos around lights
* Nausea and vomiting

This is a true eye emergency. If you have any of these symptoms, go to your ophthalmologist immediately. Unless this type of glaucoma is treated quickly, blindness can result.

Though some patients may show some less severe symptoms suggestive of this condition most with closed-angle glaucoma, unfortunately, develop it slowly without any symptoms prior to an attack.

Who is at risk for glaucoma?
Your ophthalmologist considers many kinds of information to determine your risk for developing the disease.

The most important risk factors include:

* Age;
* Elevated eye pressure;
* Changes in the optic nerve head suggestive of glaucoma;
* Changes in the field of vision;
* Family history of glaucoma;
* Farsightedness or nearsightedness;
* Past eye injuries;
* Thinner central corneal thickness;
* Systemic health problems, including diabetes and poor circulation.

Your ophthalmologist will weigh all of these factors before deciding whether you need treatment for glaucoma, or whether you should be monitored closely as a glaucoma suspect. This means your risk of developing glaucoma is higher than normal, and you need to have regular examinations to detect the early signs of damage to the optic nerve.

                                                     Normal optic nerve

                                          

Glaucomatous optic nerve - large central white cup signifies damaged peripheral nerve fibres

How is glaucoma detected?
Regular eye examinations by your ophthalmologist are the best way to detect glaucoma. A glaucoma screening that checks only the pressure of the eye is not sufficient to determine if you have glaucoma. The only sure way to detect glaucoma is to have a complete eye examination.

During your glaucoma evaluation, your ophthalmologist will:

* Measure your intraocular pressure (tonometry);
* Inspect the drainage angle of your eye (gonioscopy);
* Evaluate whether or not there is any optic nerve damage (ophthalmoscopy);
* Check the peripheral vision of each eye (visual field testing, or perimetry).

Automated Perimeter-an automated instrument used to test peripheral field of vision

                                       Decreased field or vision in glaucoma
                                   

                                        Field chart of perimetry showing defects

Photography of the optic nerve or other computerized imaging may be recommended. Some of these tests may not be necessary for everyone. These tests may need to be repeated on a regular basis to monitor any changes in your condition.

How is glaucoma treated?
As a rule, damage caused by glaucoma cannot be reversed. Eye drops, laser and surgery in the operating room are used to help prevent further damage. In some cases, oral medications also may be prescribed. With any type of glaucoma, periodic examinations are very important to prevent vision loss. Because glaucoma can progress without your knowledge, adjustments to your treatment may be necessary from time to time.

Medications
Glaucoma is usually controlled with eye drops taken daily. These medications lower eye pressure.

Never change or stop taking your medications without consulting your ophthalmologist. If you are about to run out of your medication, ask your ophthalmologist if you should continue with the same. Glaucoma medications can preserve your vision, but they also may produce side effects. You should notify your ophthalmologist if you think you may be experiencing side effects.

Some eye drops may rarely cause:

* A stinging or itching sensation;
* Red eyes or redness of the skin surrounding the eyes;
* Changes in pulse and heartbeat;
* Changes in energy level;
* Changes in breathing (especially with asthma or emphysema);
* Dry mouth;
* Changes in sense of taste;
* Headaches;
* Blurred vision;

All medications can have side effects or can interact with other medications. Therefore, it is important that you make a list of the medications you regularly take and share this list with each doctor you see.

Laser Surgery
Laser surgery treatments may be recommended for different types of glaucoma. In open-angle glaucoma, the drain itself is treated. The laser is used to modify the drain (trabeculoplasty) to help control eye pressure. In closed-angle glaucoma, the laser creates a hole in the iris (iridotomy) to improve the flow of aqueous fluid to the drain.

Surgery in the Operating Room
When surgery in the operating room is needed to treat glaucoma, your ophthalmologist uses fine, microsurgical instruments to create a new drainage channel for the aqueous fluid to leave the eye. Surgery is recommended if your ophthalmologist feels it is necessary to prevent further damage to the optic nerve. Nowadays special valves are also available which when implanted in the eye during surgery are giving good control over the intraocular pressure.

What is your part in treatment?
Treatment for glaucoma requires teamwork between you and your doctor. Your ophthalmologist can prescribe treatment for glaucoma, but only you can make sure that you follow your doctor's instructions and take your eye drops. Once you are taking medications for glaucoma, your ophthalmologist will want to see you more frequently. Typically, you can expect to visit your ophthalmologist every three to four months. This will vary depending on your treatment needs.

Loss of vision can be prevented
Regular medical eye exams may help prevent unnecessary vision loss. Recommended intervals for eye exams are:

* Age 20-29: Individuals with a family history of glaucoma should have an eye examination    every three to five years. Others should have an eye exam at least once during this    period.

* Age 30 -39: Individuals with a family history of glaucoma should have an eye examination    every two to four years. Others should have an eye exam at least twice during this period.

* Age 40-64: Every two years.

* Age 65 or older: Every year.

If we think of the eye as a hollow, fluid-filled, 3-layered ball, then the outer layer is the sclera, a tough coat, the innermost is the retina, the thin light-gathering layer, and the middle layer is the Uvea. The Uvea is made up of the iris, the ciliary body and the choroid (see diagram). When any part of the uvea becomes inflamed then it is called Uveitis.

A big problem, when trying to understand Uveitis, for patients and doctors alike, is that there are many different types of Uveitis. This is because:

* The Uvea is made up of different parts. So if the iris is affected, the condition and its    treatment could be totally different to when the choroid is affected.

* The inflammation in the Uvea very often affects other parts of the eye such as the retina    and so a variety of other problems can be present to complicate the picture.

* Next there are a large number of medical conditions where Uveitis is a feature amongst    the other symptoms of the disease. e.g. Behcet's Disease, Sarcoidosis and Toxoplasmosis,    to name just three of them.

* There are many different types of causes of Uveitis.

The term intraocular inflammation is often used to cover the spectrum of uveitis conditions. As there is this wide variety of different conditions and complications, it follows that there are numerous ways that it presents itself. The degree and type of sight loss and the type of treatment may vary considerably from patient to patient. Although the potential for confusion sounds high, as long as it is remembered that Uveitis is actually a number of different conditions, then it is possible to find out about your own particular case. It is, of course, very important, for both patients and doctors, to establish the exact type of Uveitis that exists, as far as it is possible, early on.

What causes Uveitis?
As just suggested, there are a number of quite different types of causes of Uveitis. It may result from an infection such as a virus (e.g. herpes) or fungus (e.g. histoplasmosis). It may be due to a parasite such as toxoplasmosis. It may be related to Autoimmune Disease (with or without involvement of other parts of the body). This, essentially, is when our immune system recognises a part of our own body as foreign (albeit a small part, like one type of protein). Trauma to the eye, or even the other eye in the past, can lead to Uveitis. In many cases the cause is said to be unknown. This may well mean that the Uveitis is of the autoimmune type. The word "idiopathic" may often be used to describe this group. Another important way of classifying the different types of Uveitis is by describing the part of the eye that is affected. Very simply, there may be:

Anterior Uveitis
This affects the front of the eye, normally the iris (iritis) or the ciliary body (iridocyclitis). Iritis, strictly speaking is an older term for Anterior Uveitis but is still used frequently. Iritis is by far the most common type of Uveitis and also the most readily treated. Having said that, iritis is something that needs quite close monitoring because complications such as raised eye pressure and cataracts can occur.

Intermediate Uveitis
This affects the area just behind the ciliary body (pars plana) and also the most forward edge of the retina (see the diagram above). This is the next most common type of uveitis.

Posterior Uveitis
This is when the inflammation affects the part of the uvea at the back of the eye, the choroid. Often the retina is affected much more in this group. The choroid is basically a layer rich in small blood vessels which supplies the retina.

Tests and examinations
Because of the quite diverse types of causes of Uveitis and also due to the many other medical conditions associated with it, then you can expect to receive a number of tests and thorough questioning. All these are straightforward and painless enough but may seem far removed from your eye problem, e.g. back X-rays, but as said before, it is important to establish the correct type of Uveitis so that the best treatment can be planned.

How is Uveitis treated?
The treatment of Uveitis aims to achieve the following:

* Relief of pain and discomfort (where present).
* To prevent sight loss due to the disease or its complications.
* To treat the cause of the disease where possible.

Like the varied nature of uveitis, the treatment of it may differ from case to case quite considerably. Corticosteroids are often the mainstay of treatment but now are, importantly, being joined by some other newer drugs, usually used along with the steroids. Various eye-drops are used, particularly to treat anterior uveitis.