Overview of Eye Diseases

		Overview of Eye Diseases

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	Glaucoma
	What is glaucoma? Glaucoma is a disease of the nerve fiber layer of the eye. The nerve fibers fan out over the back of the eye (retina) and travel to the brain through the optic nerve. Damage to nerve fibers results in blind spots in the visual field. Early damage is not detected by the patient, but can be detected by special tests done at the ophthalmologist’s office. Early detection is important in order to stop or slow down damage. Untreated glaucoma can result in blindness.
	Pictured here is the optic nerve head, where the nerve enters the back of the eye. Retinal blood vessels also enter at the optic nerve head.
	Who is at risk for glaucoma? Glaucoma is usually a disease of advancing age. Those with a family history of glaucoma, and those with African or Spanish ancestry have a higher risk. A history of past eye injury, elevated eye pressure, and a history of systemic disease such as diabetes are additional risk factors.

	What causes glaucoma? The normal eye maintains its shape partially because of the pressure within the eye, in the same manner that a tire does. Pressure is maintained in a normal range by the production of aqueous fluid within the eye, and the constant drainage of the fluid out of the eye. If this system becomes out of balance, then the pressure within the eye may go abnormally high. High pressure damages the nerve fibers, potentially leading to blindness.

	Types of glaucoma Chronic open angle glaucoma is the most common type of glaucoma. The risk of developing this type of glaucoma increases with age. This type of glaucoma is sometimes called “the sneak thief of sight”, because the changes are gradual and are not noticed by the patient until there is significant vision loss. Gradual changes decrease the outflow of aqueous fluid from the eye, causing a gradual increase in eye pressure. If untreated, the increasing pressure slowly kills the nerve fibers, leading to blind areas in the visual field and eventual loss of all vision. Early detection and treatment by the eye doctor are key to preventing loss of vision.

	Closed angle glaucoma is caused by the iris blocking the fluid outflow channels of the eye. Eyes that are relatively small and farsighted are at risk for this type of glaucoma. The aqueous fluid cannot exit the eye, causing an acute attack of high pressure that can cause blindness if not treated quickly. Symptoms include severe eye pain, blurry vision, halos around lights, and nausea and vomiting due to the severe pain. This is a true emergency situation.

	How is glaucoma detected? The only way to be sure to detect glaucoma is with a complete eye exam by an eye doctor. There are glaucoma screening services that check the intraocular pressure, but this test will not detect every eye that has glaucoma. A complete eye exam will include the following tests, which when combined, give the eye doctor sufficient information to make a diagnosis of glaucoma: Intra-ocular pressure (tonometry) Inspection of the drainage system of the eye (gonioscopy) Evaluation of the health of the nerve fibers and the optic nerve head (ophthalmoscopy)

	If needed, the eye doctor can perform more sophisticated testing: Automated perimetry (pictured), to map the visual field for blind spots Optic nerve head photography, to document the condition of the optic nerve Retinal nerve fiber layer analysis, to measure the thickness of the nerve fiber layer
	If the eye doctor diagnosis or suspects glaucoma, the patient may need to have this testing repeated at specific intervals (typically 6 months or 1 year) in order to detect changes over time.

	How is glaucoma treated? Most cases of glaucoma are treated with eyedrops. Some cases may require oral medication, laser treatment, or surgical treatment. The eye doctor will start with the most conservative treatment first. It is important for the patient to keep all scheduled appointments in order to effectively manage the disease. Eyedrops are prescribed to lower the eye pressure. It is very important for the patient to use the drops as scheduled and to avoid running out of the drops. Eyedrops, as with all medications, can produce side effects. The eye doctor will inform the patient of common side effects associated with any drops prescribed. It is important for the patient to report side effects to the doctor. If needed the doctor can use a laser to open up the drainage (trabeculoplasty) when treating open angle glaucoma. A laser can be used to create a hole in the iris (iridotomy) when treating closed-angle glaucoma. The hole improves the flow of aqueous fluid to the drain. In some cases, surgery is needed to create a new drainage channel for the eye (shunt). The surgery is an outpatient procedure.

	Torn Retina and Detached Retina, Floaters and Flashes What is the retina? The retina is a thin nerve layer at the back, inner surface of the eye. It is like the film in a camera. The cornea and lens of the eye focus an image on the retina and the retina sends the image to the brain.

	What is the vitreous? The vitreous is a clear, jelly like substance that fills the rear chamber of the eye. The vitreous makes contact with retina. The vitreous helps to keep the shape of the eye and it allows light to pass through to the retina. In a younger person, the vitreous is thick, like a gel. As we age, the gel becomes more like a liquid.

	What are floaters and flashes? As the vitreous ages and becomes more like a liquid, the vitreous gel tends to shrink away from the retina. In some places the gel may adhere to the retina and pull on it. This can cause the patient to see light flashes. During the pulling process, cells or blood may be released into the vitreous, appearing as “floaters” or small specks, blobs, or cobwebs in the field of vision. Small floaters or strands of vitreous occur during the normal aging process of the vitreous, particularly for nearsighted people. These floaters are annoying at times, but they don’t change much in appearance over the years. Floaters associated with the vitreous pulling on the retina appear as new objects in the field of vision and they are usually more numerous than “normal” floaters. The image below was taken with a spectral domain OCT. Here you can see the line that represents the posterior vitreous face still adherent to and pulling on the surface of the retina.


	What is a retinal tear? A retinal tear is a hole in the retina, usually caused by the vitreous gel pulling hard enough on the retina to cause the tear. When a retinal tear occurs, the associated symptoms are usually floaters and flashes as previously described. If a tear occurs, it must usually be treated in order to prevent the tear from become a detached retina.

	How is a retinal tear treated? Most retinal tears can be treated with a laser. The laser seals the edges of the tear so that the area will not detach. If the tear is in a peripheral area of the retinal that cannot be reached by the laser, then cyrotherapy (freezing) can be used to seal the tear. Laser and cryotherapy are procedures that can be performed in the eye doctor’s office.

	What is a retina detachment? If the retina pulls away from the normal position at the back of the eye, the retina is said to be detached. The retina does not function when detached, so this is a serious condition that can result in blindness. A retinal detachment usually results from fluid passing through a retinal tear and lifting the retina off. The arrow in the image below point to the edge of a retinal detachment.



	Those who have one or more of the following are more at risk of a retinal detachment: Nearsightedness Previous intra-ocular surgery, such as cataract surgery History of significant injury to the eye Family history of retina detachment Detached retina in the other eye A retinal detachment can have the same symptoms associated with a retinal tear: floaters and flashes. In addition, a retina detachment may appear as a shadow or curtain over part of the field of vision. A retinal detachment can be detected by a dilated eye examination by the eye doctor.

	What is the treatment for a retinal detachment? The treatment will depend upon the extent and the position of the detachment, as determined by the eye examination. A gas bubble is sometimes injected into the eye to push the retina back into place. This is called a pneumatic retinopexy. The patient may need to hold the head in a certain position for several days to aid the process. The gas bubble slowly dissolves. The patient with a gas bubble is restricted from flying or traveling to high altitudes until the gas bubble has dissipated. In some situations, a band is placed around the eye to move the retina back into place. This is called a scleral buckle. The fluid under the retina is drained to aid in the process. In most situations, surgery for retinal detachment is successful. There can be complications associated with the surgery and vision cannot be completely restored in every case. The smaller the area of detachment, the greater the chances are for successful surgery. The longer a detachment goes untreated, the more likely there will be a greater area of the retina detached. Therefore, it is important that a retinal tear or retinal detachment be diagnosed and treated quickly.
	Cataract What is a cataract? A cataract is a clouding of the lens of the eye. The lens of the eye and the cornea, which is the “window” of the eye, serve to focus light on the retina, which is similar to the film in a camera. The lens is normally clear, to allow light to pass through. If the lens becomes cloudy, then the quality of vision is affected. The drawing on the left/below shows the anatomical position of the lens. The image on the right is a view of a cataract through a dilated pupil.



	Symptoms of a cataract include: Blurry vision Glare from bright light Light sensitivity Fading or yellowing of colors A double image when looking with one eye Needing a brighter light in order to read Cataract formation is primarily due to aging of the lens. Injury to the eye, some medications, radiation, exposure to sunlight, family history, and other factors can speed the formation of cataracts. Some cataracts form within months, while others take years to significantly affect a person’s vision.

	How is a cataract detected? Many different eye diseases, including a cataract, can cause decreased vision. A complete examination is necessary to help the eye doctor determine if a cataract is the primary cause of decreased vision, and to recommend if and when a cataract should be removed. What is the treatment for a cataract? The only treatment for a cataract is surgical removal. There are no medications, dietary supplements, or treatments that have been proven to prevent or to cure cataracts. Protection from sunlight (UV blocking sunglasses) may slow the formation of cataracts. Cataract surgery is “elective” surgery. This means that cataract surgery is not recommended until decreased vision due to the cataract interferes with daily activity. The patient decides with the doctor when it is time for surgery. Cataract surgery is a very common procedure that is performed on an outpatient basis under topical or local anesthetic. The cataractous lens is removed with micro-surgical instruments under a microscope.

	The natural lens is replaced with an acrylic or silicone lens implant (image to the right). The power of the new lens is usually adjusted to provide the best distance vision. Some lens implants are designed to give both distance and near vision, but most people have to wear reading glasses after the surgery. Although complications are possible, more than 95% of cataract surgeries are performed without complication.

	It is a common misconception that a cataract can be removed with a laser. This is not true. There is a laser treatment that is sometimes needed after cataract surgery. The cataractous lens is in a capsule that is left in the eye after cataract surgery. Sometimes this capsule becomes cloudy after cataract surgery. The cloudy capsule can be removed on an outpatient basis with a YAG laser.

	Macular Degeneration What is the macula? The retina is on the back wall of the inside of the eyeball. The retina is like the film in a camera. Light falls on the retina and it sends signals to the brain that are perceived as vision.
	The macula is the small, central area of the retina where light is sharply focused.

	What is macular degeneration? Macular degeneration is deterioration of the cells and structure of the macula. This deterioration causes a loss of sharp detail in the center of the field of vision. Vision loss can be in the form of blurriness, distortion, or a complete blackout of central vision, depending upon the severity of the deterioration. Macular degeneration does not result in total blindness. Even in the most advanced stages of macular degeneration, the eye still has peripheral vision, allowing patients to navigate and care for themselves. The patient with advanced macular degeneration in both eyes typically cannot read, has difficulty recognizing faces, and may not be able to see the picture on the TV set. The image below shows a scar from macular degeneration in the center of the macula.


	What causes macular degeneration? Some forms of macular degeneration are genetic, but most are part of the normal aging process. There are two basics types of macular degeneration: dry and wet. Dry macular degeneration is the most common. The retinal tissue thins over time and there is a gradual decrease in vision. Only about 10% of macular degeneration is the wet type. It is called “wet” because there is a buildup of fluid within or underneath the retina. It is caused by a network of new blood vessels that leak fluid. The onset can be sudden and there can be a dramatic decrease in vision. Another common symptom is distorted vision.

	How is macular degeneration diagnosed? The eye doctor can diagnose macular degeneration by looking into your eye (ophthalmoscopy) as part of a complete eye exam. If macular degeneration is suspected, optical coherence tomography (OCT) and/or fluorescein angiography (a dye test) can be performed to determine if it is the wet type. The image below/right is a fluorescein angiogram showing the "wet" area, which is the white area centrally. The image below/left is an OCT cross-section of the same area (arrow).


	What is the treatment for macular degeneration? Nutritional supplements with antioxidants and other vitamins and minerals have been shown to help decrease the risk of vision threatening macular degeneration by about 25%. These supplements do not cure macular degeneration, they just slow down the process in some people. Research continues on new treatments for macular degeneration. Laser treatment has helped some cases of macular degeneration. The primary treatment at present for macular degeneration is called anti-VEGF therapy. This type of drug, which is injected into the vitreous, targets a chemical that causes the new blood vessel growth in wet macular degeneration. Although this treatment has proven to be beneficial in slowing the disease, many patients still experience vision loss. Visual aids to help the patient with vision loss due to macular degeneration The majority of people with loss of central vision can maintain a relatively independent life style. Peripheral vision is not affected, so most tasks of daily living can be accomplished. Large print books, magnifying devices, and closed-circuit television help the patient make the most of the sight that remains.

	The Amsler Grid The Amsler grid is an “early warning” device that can give an indication that the central vision is changing. This is a printed grid of lines making small squares within a larger square. There is a small dot in the center for fixation.

	The idea is to look at the dot in the center of the grid once a day and to notice if any lines are distorted or if any squares are grayed out or missing. If changes are noticed, then there may be a deterioration of the macula and the patient should make an appointment to see the eye doctor. The grid should be viewed with one eye at a time (cover the other eye) at a normal reading distance. Reading glasses or bifocals should be worn if needed for near vision.

	Diabetic Retinopathy What is diabetic retinopathy? Diabetes is disease that adversely affects the blood vessels all over the body, including the blood vessels in the retina of the eye. The retina is the light sensitive layer at the back of the eye that is similar to the film in a camera. Light focuses on the retina, and the retina sends signals to the brain that are perceived as vision. Damage to the retina due to diabetes is called diabetic retinopathy. There are two types of diabetic retinopathy: non-proliferative (NPDR) and proliferative (PDR). NPDR is also called background diabetic retinopathy. NPDR is characterized by blood and fluid leaking from the very small blood vessels (capillaries). This type of retinopathy does not affect vision unless there is an accumulation of fluid within the central zone of the retina called the macula. This is called macular edema. Damaged blood vessels may also cease circulating blood to areas of the macula. This is called macular ischemia. PDR occurs when new blood vessels (neovascularization) grow on the surface of the retina or at the head of the optic nerve. The new blood vessels growth is a response to the lack of circulation caused by damaged blood vessels. The new blood vessels are ineffective and they cause more harm than good by forming scar tissue and by bleeding. Below are fluorescein angiogram images of PDR. Neovascular bleeding can go into the vitreous (vitreous hemorrhage) and block vision. The scar tissue can wrinkle and pull on the retina, possibly causing a retinal detachment (traction retinal detachment).



	In some diabetic eyes, new blood vessels can form on the iris of the eye. This neovascularization can block the outflow of aqueous fluid and cause a buildup of pressure within the eye. This is a potentially blinding disease called neovascular glaucoma.

	How is diabetic retinopathy diagnosed? The eye doctor can diagnose diabetic retinopathy by looking into your eye (ophthalmoscopy) as part of a complete eye exam. If diabetic retinopathy is suspected, optical coherence tomography (OCT) and/or fluorescein angiography (a dye test) can be performed to determine if there is fluid (edema) or new blood vessel growth (neovascularization). How is diabetic retinopathy treated? The best treatment for diabetic retinopathy is prevention. Good blood sugar control is a key to reducing the risk of vision loss. Early diagnosis and treatment is another key. Yearly vision exams are very important for the diabetic. Vision loss due to diabetic retinopathy ranges from mild loss to total blindness. Diabetic macular edema can be treated with injections of medication into the vitreous of the eye or with laser treatment to leaking blood vessels. Proliferative diabetic retinopathy is treated with panretinal photocoagulation, which is an extensive laser treatment to the peripheral areas of the retina. Treatments for diabetic retinopathy are considered to be successful if vision does not get worse. If there is bleeding into the vitreous, a surgical procedure to remove the blood may need to be done (vitrectomy). The doctor may advise waiting to see if the blood will clear on its own before surgery. In some situations removal of new blood vessels and/or retinal detachment repair is part of the vitrectomy procedure.

	Dry eye What causes dry eye? Dry eye can be due to the natural aging process, it can be associated with other health problems, and it can be caused or made worse by certain mediations. Sjogren’s sydrome is a health problem that is manifested by dry eyes, dry mouth, and arthritis. Common types of medications that may dry the eyes are diuretics, antihistamines, birth control pills, beta-blockers, sleeping medications, and some pain relievers. The package insert will tell you if dry eye is a side effect of the medication. Many of these medications are necessary and stopping them may not be a good option. How is dry eye diagnosed? An eye doctor can diagnose dry eye during an examination of the eyes. He can observe the status of the tear layer under magnification. Special tests such as “tear breakup time” and the Schirmer tear test give the doctor additional information about the condition of the tears, tear production, and the tear drainage system. How can dry eye be treated? There are lubricating eye drops called “artificial tears” that will give temporary relief of dry eye symptoms. These are over-the-counter drops that can be used as often as needed for relief. If you use artificial tears very often, you may become hypersensitive to the preservative used in the drop. Because of this problem, manufacturers make some brands that are preservative free. Artificial tears come in different thicknesses or “viscosity”. To determine which gives you the best relief, try several different brands. Your eye doctor may recommend a specific type of artificial tear drop. Your eye doctor may recommend that a plug be inserted into the hole in the eyelid that drains tears from the eye. The “punctum plug” blocks drainage so that the tears that you do produce are conserved. There are other measures that you can take to reduce dry eye symptoms: - Use a humidifier in winter. - Avoid wind, smoke, and direct sunlight. - When outdoors, wear glasses to shield your eyes from wind and sun. - Do not wear contact lenses. - If you wake up with dry eye symptoms, use a lubricating ointment before you go to - sleep.

	Blepharitis What is blepharitis? Blepharitis is an inflammation of the eyelids that can be associated with a bacterial infection, dry eyes, or with a skin condition called rosacea. There are two basic types of blepharitis. It is possible to have both types at the same time. Anterior blepharitis affects the front part of the eyelids, where the lashes are. It can be caused by bacteria, viruses, dermatitis, and even mites. Posterior blepharitis is caused by a dysfunction of the meibomian glands, which are oil secreting glands within the lid tissue. The glands may decrease secretions or produce abnormally oily secretions. This type is associated with dry eyes because the secretion is a component of the tears.
	What are the symptoms of blepharitis? Flaking, crusting, and redness at the eyelid margin Moderate swelling of the tissue at the eyelid margin Burning, itching, and irritation of the eyelids Foreign body sensation How is blepharitis diagnosed and treated? An eye doctor can examine your eyelids and determine if you have blepharitis and what type it is. Blepharits is a chronic disease, meaning there is no cure for it and it rarely goes away completely. However, blepharitis can be managed effectively. The doctor may prescribe eye drops and/or ointment, and in some cases a systemic medication to get blepharitis under control. Eyelid hygiene is the key to long term control of blepharitis. Eyelid hygiene consists of cleansing of the eyelid margins, warm soaks of the eyelids, and massaging the eyelids. A warm compress to the eyelids will loosen the crusting and flaking on the eyelid margins. It will also soften the secretions inside the meibomian glands. Wash your hands. Moisten a washcloth with very warm water. The water should not be hot enough to burn our skin. Apply the washcloth to your outer eyelids for several minutes. Re-soak the washcloth in very warm water after is cools off. Re-apply to the lids. After apply the compress, gently rub the lid with your finder in a circular fashion. Do not press on hard on your eyeball. After using warm compresses, clean the eyelid margins. Use an over-the-counter solution made the purpose, or make your own soap solution with baby shampoo diluted with water. Dip a washcloth or cotton ball in the solution. Gently rub the eyelid margin and the eyelashes back and forth a few times. Rinse your eyelids in cool water. Repeat the process for the other eye, but do not use the same washcloth or cotton ball. Lid hygiene must be used several times a day to get blepharitis under control. Once under control, the hygiene can be performed once a day, or once every other day.



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Overview of Eye Diseases

Overview of Eye Diseases

Glaucoma

Torn Retina and Detached Retina, Floaters and Flashes

Cataract

Macular Degeneration

Diabetic Retinopathy

Dry eye

Blepharitis