Age-Related Macular Degeneration (AMD)

Introduction

AMD is a common eye condition and a leading cause of vision loss among people age 50 and older. It causes damage to the macula, a small spot near the center of the retina and the part of the eye needed for sharp, central vision, which lets us see objects that are straight ahead

The Macula

The macula is made up of millions of light-sensing cells that provide sharp, central vision. It is the most sensitive part of the retina, which is located at the back of the eye. The retina turns light into electrical signals and then sends these electrical signals through the optic nerve to the brain, where they are translated into the images we see. When the macula is damaged, the center of your field of view may appear blurry, distorted, or dark.

Signs and symptoms

Early or intermediate AMD may be asymptomatic, or it may present with blurred or decreased vision in one or both eyes. This may manifest initially as difficulty with reading or driving (especially in poorly lit areas). Other symptoms of AMD include distortion of vision and blind spots (especially in and around the central visual field).

Diagnosis

Diagnosis of dry (or early stage) AMD may include the following clinical examinations as well as procedures and tests:

• The transition from dry to wet AMD can happen rapidly, and if it is left untreated can lead to legal blindness in as little as six months. To prevent this from occurring and to initiate preventive strategies earlier in the disease process, dark adaptation testing may be performed. A dark adaptometer can detect subclinical AMD at least three years earlier than it is clinically evident.
• There is a loss of contrast sensitivity, so that contours, shadows, and color vision are less vivid. The loss in contrast sensitivity can be quickly and easily measured by a contrast sensitivity test like Pelli Robson performed either at home or by an eye specialist.
• When viewing an Amsler grid, some straight lines appear wavy and some patches appear blank
• When viewing a Snellen chart, at least 2 lines decline
• In dry macular degeneration, which occurs in 85–90 percent of AMD cases, drusen spots can be seen in Fundus photography
• Using an electroretinogram, points in the macula with a weak or absent response compared to a normal eye may be found
• Farnsworth-Munsell 100 hue test and Maximum Color Contrast Sensitivity test (MCCS) for assessing color acuity and color contrast sensitivity
• Optical coherence tomography is now used by most ophthalmologists in the diagnosis and the follow-up evaluation of the response to treatment with antiangiogenic drugs.Diagnosis of wet (or late stage) AMD may include the following in addition to the above tests:
• Preferential hyperacuity perimetry changes (for wet AMD). Preferential hyperacuity perimetry is a test that detects drastic changes in vision and involves the macula being stimulated with distorted patterns of dots and the patient identification of where in the visual field this occurs.
• In wet macular degeneration, angiography can visualize the leakage of bloodstream behind the macula. Fluorescein angiography allows for the identification and localization of abnormal vascular processes.

Management

Treatment of AMD varies depending on the category of the disease at the time of diagnosis. In general, treatment is aimed at slowing down the progression of AMD.

Vitamin and mineral supplementation

The age-related eye disease studies showed that those with bilateral early or intermediate AMD, or intermediate AMD in one eye and advanced AMD in the other eye may benefit from specific vitamin and mineral supplementation. The specific vitamins and minerals are vitamin C (500 mg), zinc (80 mg), vitamin E (400 IU), copper (2 mg) and beta-carotene (15 mg).

Dry AMD

There is no cure for dry AMD. While there is increasing academic and pharmaceutical interest in developing complement inhibitors to treat ophthalmic inflammation, with several clinical trials underway for dry AMD, the first such agent to complete Phase 3 trials in AMD (the anti-factor D agent, lampalizumab) did not significantly improve the rate of disease progression.

Wet AMD

Ranibizumab, aflibercept, brolucizumab and faricimab are approved VEGF inhibitors for the treatment of CNV in wet AMD. All three drugs are administered via intravitreal injection, meaning they are injected directly into the eye.AMD can also be treated with laser coagulation therapy.