Retina is the light sensitive layer lining the inside of eye. It receives images of objects and transmits them to brain via optic nerves. The macula is a very small central part of retina which is responsible for sharp central vision. All the fine details such as recognizing a face, reading, watching television, appreciation of colors etc. are functions of macula.

Definition

ARMD is a chronic progressive disease due to damage in layers of retina at macula wherein the visual cells-retinal pigment epithelium, rods and cones are degenerated. It is a major cause of severe loss of vision in age group above 50 years of age. Initially it is a silent disease and can affect one eye to begin with. Gradually vision loss increases mainly in the center allowing better vision at sides, but makes reading or close work difficult without the use of special low vision aids. The early stages of ARMD typically start with appearance of Drusen spots beneath the retina. These do not affect vision very much by themselves and most people with Drusen will never have a serious loss of vision. However, certain changes may occur that lead to the late stage of ARMD which leads to marked visual loss.

Cause & Risk Factors

The exact cause of macular degeneration is not known though following risk factors have been identified: age, heredity, sex (women more affected then men), light ocular pigmentation, hypertension, cardiovascular diseases, diabetes, photo toxicity and cigarette smoking.

Types: There are 2 types of ARMD: “Dry” and “Wet”

Dry ARMD is the most common form accounting 80-90% of all cases and is associated with ageing. It is caused by degeneration in visual cells leading to yellow-white deposits in layers of retina called drusen or may form areas of atrophy in macula. Overtime dry ARMD may develop into wet type.

Wet or Exudative ARMD   is the more severe variety where blood vessels break or leak into the retinal layers to form a scar tissue or vascular membrane. Fragile abnormal blood vessels grow which leak causing further scarring at macula leading to severe loss of central vision.

Symptoms

If only one eye is affected to begin with, the symptoms are not noticeable in early stages.  Gradually as disease progresses or if both eyes are involved, reading or close work may become difficult. There can be distortions in objects which are looked at directly, for eg-bulges or curved appearance of a straight door, distorted print lines in book, a dark or blank spot in the center of vision, or fading of colors specially blue.

Detection

As initially it is a silent disease, mostly it is picked up in a routine examination by an ophthalmologist .The retinal examination done by an ophthalmoscope will show the findings of this disease process. To assess the condition in detail, certain other test are done:

• Amsler Grid: It is a test paper with graphic picture to be used at reading distance with near glasses on. This is used to check for extent of sight loss-dark spot, distortion or missing of straight lines and also is given to the patient to take home so that he can monitor his symptoms at home and report immediately if there is worsening.
• Color vision test
• Fluorescin Angiography / ICG: the photographs of macula are taken after injecting a dye in patient’s arm. The dye reaching the eye helps to clarify the type and extent of disease, including detail of abnormal vessels, leaks and membrane formations.

Prevention

There is no prevention of ARMD. Early detection is the key to prevent severe loss of vision. All individuals above 50,especially if there is a family history of ARMD, history of cardiovascular disease, light ocular pigmentation, should get yearly retinal check up for the same. Anyone experiencing following symptoms should consult an ophthalmologist immediately:

• Straight lines appearing distorted-specially in the center of vision
• Dark blurry or white patch in the center of vision
• Color perception changes

Smoking is a risk factor and should be avoided at all costs if any of the risk factor is present.

Treatment

There is no permanent cure for most type of ARMD. In some cases ARMD may be active and then slow down or even stop progressing for many years. The aim is to keep a vigilant check on progression of disease and take measures to improve functional capability of the patient.

• Nutrition: Eat fresh fruits, dark green leafy vegetables. The role of antioxidants/zinc in retarding the progression is not very clear but supplementation with Vitamins C and E, zinc and selenium may have a positive effect..
• Sunlight: Blue rays of the spectrum seem to accelerate macular degeneration. Sunglasses with good UV filters for outdoor activities are recommended.
• Smoking: quit smoking as this accelerates the process of wet ARMD
• Early detection: Daily monitoring of vision by Amsler grid-report immediately to eye surgeon if any change noticed (the development of wet type may need urgent laser treatment)
• Laser treatment-This procedure uses a high-energy laser beam to destroy the fragile leaking blood vessels. Fluorescin Angiography is done to detect the area and extent of involvement and blood vessels away from fovea are treated. This will not improve vision but may reduce further progressive vision loss. However, laser treatment also may destroy some healthy tissue in that region and some vision also.
• Photodynamic therapy - A drug called Verteprofin is injected into the arm and reaches the eye blood circulation. Here it tends to stick to the surface of new abnormal blood vessels, which is then exposed to a bright light shining in the eye. The drug gets activated and destroys the new blood vessels leading to slower decline in vision. This drug does not destroy the surrounding normal tissue and hence is better then laser treatment. However, treatment results often are temporary and may require re-treatment.
• Low vision aids and lighting –These are devices, which can improve quality of living by improving vision for day-to-day activities, specially reading. Special optical devices like magnifiers (hand held, desktops or in spectacles) can be used in various ways. Adequate lighting will make reading more comfortable with 50-watt indoor bulb in metal shade then fluorescent light.

 

Author - Dr. Sanjay Dhawan

Last Updated - 1 April 2005

 New Delhi, India