The retina is a very thin, but complex tissue that lines the back of the eye. It is composed of millions of cells, including photoreceptor cells that sense light and send images to the brain.
There are many conditions that can impair the retina’s ability to receive and transmit images. The most common retinal diseases are diabetic retinopathy, age-related macular degeneration, and retinal detachments. These conditions are all very serious and if not treated, can lead to loss of vision.
A retinal examination is the only way to properly diagnose retinal problems. Serious retinal diseases can often be treated before the patient begins to experience vision problems. During the exam the ophthalmologist first dilates the pupil using drops and then looks inside the eye with an ophthalmoscope, a device that allows the physician to clearly see the retina.
In some cases, additional testing is required. One test is a fluorescein angiogram, which can help the doctor evaluate the retina more easily. In this test, a small amount of dye is injected into a vein in the hand or arm. As the dye circulates through the blood vessels of the retina, photographs of the retina are taken.
Another effective test is the Optical Coherence Tomography (OCT), a new technology we are pleased to offer at The Rhode Island Eye Institute. This rapid imaging device bounces light rays off the retina and the reflections are transmitted to a computer. The result is a detailed 3-D cross-section of the retina.
Treatment of Retinal Diseases
Many retinal diseases can be treated with various forms of laser light. These very powerful light beams can help destroy abnormal blood vessels in the retina or act to seal off retinal tears. Laser therapy is usually done in our office with anesthetic drops or anesthetic injection around the eye to ease any discomfort.
Other retinal diseases require surgery. Most retinal surgery involves first removing the vitreous gel (the clear fluid inside the eye), and then using delicate instruments to remove any abnormal tissue from the surface of the retina. Retinal surgery is usually done in a hospital operating room with a local anesthetic.
Diabetic Retinopathy Treatment
Diabetic retinopathy results when blood vessels in the retina are damaged due to high blood-sugar levels in people with diabetes.
Prevention through strict control of blood sugar levels is the best way to reduce the long-term risk of vision loss from diabetic retinopathy. For more advanced diabetic retinopathy, laser treatment is often recommended. Sometimes retinal surgery is required.
Age-Related Macular Degeneration
Age-related macular degeneration (AMD) is the leading cause of legal blindness in the United States. In fact, 2.2% of people 65 years or older have severe vision problems from the disease.
AMD is a disease that affects the macula, the small area in the center of the retina that allows fine details to be seen clearly. Despite the fact that the macula takes up only 3% of the retinal surface area, it is responsible for all detailed vision, such as reading, artwork, seeing the face of a clock, etc. An eye affected by macular degeneration will not be able to perceive details or colors as well as a healthy eye.
The first sign of macular degeneration may be the need for more light when you do close –up work. Fine print may become harder to read and street signs more difficult to recognize. The condition usually develops gradually, but may sometimes progress more quickly, leading to severe vision loss in one or both eyes.
The condition tends to develop as you get older, hence the term,”age-related”. Macular degeneration is the leading cause of severe vision loss in people age 60 or older.
There are two forms of macular degeneration: “dry” macular degeneration and “wet” macular degeneration. The dry form is more common and is caused by aging and thinning of the cells in the macula. Vision loss is slow and gradual.
The “wet” form occurs in only 10% of patients with AMD and causes much more rapid, and usually more serious, loss of vision. This loss of vision is due to the growth of abnormal fragile blood vessels in or near the macula. These blood vessels leak blood or fluid and blur central vision quickly. Untreated wet AMD can lead to scarring of the macular area and permanent vision loss.
Treatment of Age-Related Macular Degeneration
There is no cure for dry AMD, though various combinations of vitamins and anti-oxidant pills have been shown to help slow down the progress of the disease.
Some treatment options are available for wet macular degeneration, including Photocoaguation (Argon Laser Therapy), Photodynamic Therapy (PDT), Visudyne®, Macugen®, Avasin and Transpupillary Thermotherapy (TTT).
Photocoagulation: Argon Laser Therapy
In photocoagulation, the doctor uses a high-energy laser beam to create small burns in areas with abnormal blood vessels. It can prevent further damage to the macula and halt continued vision loss.
Photodynamic therapy (PDT)
This therapy is for treatment CNV or abnormal blood vessels that is located directly under the fovea. The fovea lies at the center of your macular and in healthy eyes provides your sharpest vision. PDT increases your chances of preserving some of that vision. It won’t bring back vision you have lost, but it may halt the loss of your vision or at least slow down the rate of vision loss.
TTT are a technique that uses a state-of-the-art diode laser to slowly deliver heat through the pupil to the abnormal blood vessels in the retina. The heat from the laser destroys the abnormal vessels to stop or slow the effects of macular degeneration.
Approved by the Food and Drug Administration in December 2004, pegaptanib, (Macugen) is a drug used for treatment of wet macular degeneration. The drug stops the formation of new blood vessels and decreases leakage from existing blood vessels. Macugen, given as a series of injections into the vitreous fluid in the eye, may prevent further loss of vision.
Like Macugen, ranibizumab (Lucentis) is another drug to treat wet macular degeneration by impeding new growth of abnormal blood vessels. Lucentis shows promise in reversing the effects of macular degeneration, not just preventing further vision loss. Lucentis is currently available only in clinical trials; however, it is being prescribed using a closely related drug, bevacizumab (Avastin).
Visudyne is a light-activated drug that is injected into the blood stream and travels to the abnormal blood vessels in the macula where it collects. A “cold” PDT laser activates the medication and closes the abnormal blood vessels without causing damage to the healthy retina. The therapy may be reapplied at three-month intervals as needed.
Transpupillary Thermotherapy (TTT )
Transpupillary Thermotherapy (TTT) is a technique that uses a state-of-the-art diode laser to slowly deliver heat through the pupil to the abnormal blood vessels in the retina. The heat from the laser destroys the abnormal vessels to stop or slow the effects of macular degeneration.
Almost all retinal detachments start with a small tear in the retina, which allows fluid to go behind the retina and push it out of its normal position in the back of the eye. Detachments are very serious and almost always lead to blindness if not treated promptly.
Most retinal tears (the early stage of retinal detachment) are treated with laser surgery or cryotherapy (freezing), both of which reattach the retina to the back wall of the eye. This treatment usually prevents retinal detachment and is performed in the doctor’s office with little to no discomfort.
A retinal detachment requires surgery to first seal the tear and then reattach the retina back in its proper position. There are several types of surgery used, and the decision of which type depends upon the characteristics of the detachment. Some retinal detachments can be treated in the doctor’s office, using an injection of air inside the eye to push the retina back into position. However, most detachments require surgery in a hospital operation room.