Glossary of Terms
Bowman's layer is a transparent sheet of tissue that lies beneath the epithelium. It is made of strong layered protein fibers called collagen. If it is injured, the tissue in Bowman's layer forms a scar as it heals. If these scars are large and centrally located, they can interfere with vision.
This is a clouded area in the eye's lens. While many people get cataracts as they age, they happen at an earlier age in people with diabetes.
A corneal dystrophy is a condition in which one or more parts of the cornea lose their normal clarity due to a buildup of cloudy material. There are over 20 corneal dystrophies that affect all parts of the cornea. Many of them are inherited and not the result of other health or lifestyle factors.
damage to the cornea from injury or bacteria can cause painful inflammation and corneal infections. Another name for a corneal infection is keratitis. Corneal infections can be a rare but serious complication of contact lens wear. They can reduce clarity of vision, cause corneal discharges, and even erode the cornea. They can also lead to corneal scarring, which can harm vision and might require a corneal transplant.
This is a thin but strong sheet of tissue that protects the eye from infection and injuries. It also holds a part of the cornea called the corneal endothelium. Descemet's membrane heals quickly after injury.
DSEK is another option for people who need a cornea transplant for cornea swelling. DSEK is also called the "sutureless corneal transplant," since it does not require stitches. DSEK has some advantages over traditional corneal transplant. These include faster vision recovery, a stronger eye, lower risk of rejection, and lower risk of conditions that can be caused by stiches, such as astigmatism and infections.
- Synonyms: DSEK
Diabetic retinopathy is the most common diabetic eye disease and a leading cause of blindness in adults in the U.S. It is caused by changes in the blood vessels of the retina. The retina is the light-sensitive tissue at the back of the eye. A healthy retina is necessary for good vision.
In people with dry eye, the eye produces fewer or lower quality tears and is unable to keep itself moist and comfortable. The main symptom of dry eye is a scratchy or sandy feeling as if something is in the eye.
This is the outermost layer of the cornea that blocks foreign material, such as dust, water, and bacteria, from entering the eye and provides a smooth surface that allows the cornea to get nutrients from tears. The epithelium is filled with thousands of tiny nerve endings that make the cornea very sensitive to pain.
- Synonyms: floater, Floater
This is damage of the optic nerve and loss of vision. It is usually associated with an increase in fluid pressure inside the eye. A person with diabetes is nearly twice as likely to get glaucoma.
Granular dystrophy causes "crumb-shaped" lesions to form on the inside of the eye. Over time, these lesions can grow and affect vision. In some people, the condition also causes eye pain or discomfort.
This is an infection that is caused by the varicella-zoster virus. This is the same virus that causes chickenpox. In most cases, once a person recovers from chickenpox, the virus remains inactive in his or her body. But in some people, the virus becomes active again later in life. When this happens, the virus travels down nerve fibers and can infect any part of the body. The infection causes a blistering rash (called shingles), fever, painful inflammations of the affected nerve fibers, and a general feeling of sluggishness. In many people who have a varicella-zoster infection in their head or neck, the virus also affects the cornea.
- Synonyms: shingles
This condition involves changes in the iris (the colored part of the eye), swelling of the cornea, and the development of glaucoma. Glaucoma is a disease in which normal fluid inside the eye cannot drain properly. Glaucoma can cause severe vision loss. ICE is most common in women and usually diagnosed between ages 30 to 50. It usually only happens in one eye.
- Synonyms: ICE
This is the most common corneal dystrophy in the U.S, and is most prevalent in teenagers and adults in their 20s. It happens when the middle of the cornea thins and gradually bulges outward, forming a cone shape. This bulging changes the how the cornea refracts (bends) light, and can cause refractive errors such as nearsightedness and astigmatism. It can also cause swelling and scarring of the cornea, which can harm vision. Keratoconus usually affects both eyes.
Lattice dystrophy causes abnormal protein fibers (called amyloid deposits) to collect in the stroma. Over time, these groups of fibers converge and take up more of the stroma. This causes cloudiness in the cornea and can also harm vision. Although lattice dystrophy can occur at any time in life, the condition usually happens in children between the ages of two and seven.
- Synonyms: normal-tension glaucoma
This is when fluid leaks into the center of the macula, the part of the eye that allows for central vision. Central vision is the sharp, straight-ahead vision needed to see fine detail. When fluid leaks into the macula, it causes swelling and blurs vision. Macular edema can happen at any stage of diabetic retinopathy, although it is more likely to happen as the disease worsens. About half of the people with proliferative retinopathy also have macular edema.
This dystrophy happens when part of the epithelium does not develop normally, and epithelial cells cannot properly adhere to it. This causes the erosion of the epithelium. This condition is also called "epithelial basement membrane dystrophy," since it affects the area of the epithelium called the basement membrane.
This is the earliest stage. People in this stage have small areas of balloon-like swelling in the retina's tiny blood vessels. These are called microaneurysms.
In this second stage, blood vessels that nourish the retina become blocked.
This condition is caused by recurrent viral infections from the herpes simplex virus. It is the most common infectious cause of corneal blindness in the U.S. It causes a painful sore on the eyelid or surface of the eye and inflammation of the cornea.
Phototherapeutic keratectomy (PTK) can treat superficial corneal dystrophies, corneal scars, and certain corneal infections. Only a short time ago, people with these disorders would most likely have needed a corneal transplant.
- Synonyms: PTK
At this advanced stage, the signals sent by the retina in the third stage trigger the growth of new blood vessels. These new blood vessels are fragile and break easily. They grow along the retina and along the surface of the clear, vitreous gel that fills the inside of the eye. On their own, these blood vessels do not cause symptoms or vision loss. But if they break and leak blood, they can cause severe vision loss and even blindness.
A pterygium is a pinkish, triangular-shaped growth of tissue on the cornea. Pterygia are more common in sunny climates and in people aged 20 to 40. Some pterygia grow slowly throughout a person's life, while others stop growing after a certain point. A pterygium rarely grows so large that it begins to cover the pupil of the eye.
This is a kind of laser surgery for people with proliferative retinopathy. Scatter laser treatment helps to shrink the abnormal blood vessels. For this treatment, the doctor places 1000 to 2000 laser burns in the areas of the retina away from the macula. This causes the abnormal blood vessels to shrink. Because a high number of laser burns are necessary, a person who gets this treatment usually needs two or more sessions. Scatter laser treatment can cause some loss of peripheral (side) vision, but it can preserve and save the rest of the person's vision, especially critical central vision. It might also slightly reduce color vision and night vision.
In this third stage, many more blood vessels are blocked. This keeps several areas of the retina from receiving the blood supply they need. These areas of the retina send signals to the body to grow new blood vessels for nourishment.
Beneath Bowman's layer is the stroma, which accounts for about 90 percent of the cornea's thickness. It is mostly made of water and collagen. The collagen's unique shape, arrangement, and spacing are important in allowing light to pass through the cornea. The stromal layer is is the part of the cornea that is reshaped in laser vision correction, such as PRK and LASIK procedures.
This is a surgical procedure for people with severe bleeding. During a vitrectomy, the doctor removes blood from the center of the eye. If you have this treatment, you will probably also have scatter laser treatment at the same time.