Etiology and Symptoms/Signs

What is macular degeneration

Macular degeneration is one of the major diseases caused blindness and visual impairment in the older persons, especially in their 50 to 60 years of age.  Therefore, macular degeneration was also known as age-related macular degeneration (AMD). The retina is a thin lining of light-sensitive cells that line the inside of the eye. It receives and processes images and sends these images to the brain via the optic nerve. The macula is a small, but very important part of the retina capable of perceiving the sharpest of images. It is here that our central vision, our reading vision and our color vision are received. Without the macula, we would be legally blind with only peripheral vision to guide us. The center of the macula is called the fovea. This is our point of visual function.

Types of AMD

Age-related maculopathy can be grouped into two categories: a dry form and a wet form.

Dry AMD

This form of AMD consists of a slow deterioration of the retina. Deposits form under the retina called drusen. Drusen may block nutrition from reaching the retina from a highly vascular layer under the retina, the choroid. The choroid nourishes the outer layers of the retina, while the retinal blood circulation supplies the inner layers. Over time, the retina atrophies, or degenerates, over these areas of drusen and a spotty loss of vision occurs. If more and more of these atrophic areas form and merge together, the macula can take on a moth-eaten appearance, with progressive loss of vision. This usually occurs over a period of many years.

Wet AMD

This is a more severe and rapidly progressive form of AMD. In some cases, the dry form will lead to the wet form, but in other cases this form occurs without warning. Between the vascular choroid layer under the retina and the retina itself is a dividing membrane called the retinal pigment epithelium (RPE). If a break occurs in the RPE, it becomes possible that an abnormal blood vessel could grow from the choroid to directly underneath the retina in the macula. Such a break could occur in an area of drusen, especially drusen that have pigmentation and appear diffuse or fuzzy. When a new blood vessel grows under the retina, it is termed subretinal neovascularization.

Risk factors

Age-related macular degeneration can lead to the deterioration of the macula, and possible loss of vision. Risk factors for this condition include:

• Advancing age, over 50 years of age, and especially over 65
• A history of visual loss related to macular degeneration in the other eye
• A family history of AMD
• Certain types of retinal deposits, called drusen
• Arteriosclerosis and increased cholesterol, possibly hypertension
• A diet deficient in anti-oxidant vitamins and minerals
• Tobacco smoking

Diagnosis and Treatment

Diagnosis

• A careful history is taken as to possible risk factors and symptoms of AMD.
• A careful retinal examination to look for evidence of AMD or for any precursors of drusen.
• Additional tests such as fluorescein angiography and Amsler grid testing.
• Scheduling appropriate follow-up visits, and self-monitoring of vision by the patient.
• The Amsler grid is a small graph-like chart with a central dot. It is useful for testing for distortion of vision. This is a way for patients with risk factors for AMD, or with previously treated AMD to monitor their vision for development of subretinal neovascularization.

Treatment of dry AMD

• There is no cure for this form of the disease.
• Vision should be monitored with the Amsler grid regularly for early detection of the wet form of AMD.
• Follow-up appointments should be kept as directed.
• Nutritional supplements can be considered.

Treatment of wet AMD

• Once diagnosed with wet AMD, it is implied that subretinal neovascularization is present. If this finding meets certain criteria on the fluorescein angiogram, laser treatment may be able to eliminate the abnormal blood vessel
• If treated with laser, a blind spot will result in the vision.
• The purpose of the laser treatment is to prevent severe loss of vision. Sometimes some loss of vision may occur with the laser treatment in order to prevent further loss of vision.
• After successful laser treatment, the situation needs to be closely monitored for signs of recurrence. This includes follow up examinations and possibly more fluorescein angiograms.
• The Amsler grid should be closely monitored by the patient in both the affected and unaffected eye for a change in vision.
• Nutritional supplements can be considered.