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  Vision Deterioration in Dry AMD

Vision loss in dry AMD is caused by atrophy or weakening of the retinal pigment epithelium (RPE) layer just outside the retina and the overlying photoreceptor cells. Vision loss with dry AMD is usually slow and gradual. A patient may begin to notice blank areas in their central vision. Over time, dry AMD can cause a large loss of detail vision; however, vision loss is generally not as severe compared to the wet form.

Development of Wet AMD

As previously discussed, dry AMD will often begin to convert to wet AMD, with the appearance of abnormal choroidal blood vessels - angiogenesis. The reason why angiogenesis occurs is unknown, however, it is believed that there is a link between angiogenesis and damage to Bruch's membrane, which lies directly under the RPE, caused by the deposit of drusen. The drusen allows an angiogenic stimulant to promote the growth of underlying choroidal blood vessels into the subretinal space and retina. These tufts of blood vessels are fragile and have a propensity to leak and bleed, eventually forming scar tissue and resulting in irreversible vision loss.

An article recently published in Graduate Medicine discussed a possible genetic component (ABCR gene). The study stated that first-degree relatives of patients with wet macular degeneration have three times the risk of developing the wet AMD. Thus, macular degeneration can be considered a consequence of aging in genetically predisposed persons. Learn about other risk factors for AMD.

Vision Deterioration in Wet AMD

Visual deterioration associated with the wet form is generally severe and can be rapid. Unlike dry AMD the patient may begin to notice reduced vision and distortions due to the effect neovascularization or abnormal vessel growth has on the overlying retina.

Dry AMD

There are currently no treatments or preventative measures for dry AMD. Low vision aids and rehabilitation are available to assist patients in coping with vision loss associated with dry AMD.

Wet AMD

There are only two clinically proven treatments for wet AMD. The first treatment is laser photocoagulation, a surgical procedure involving the application of a hot laser to seal and halt or slow the progression of abnormal blood vessels. The second treatment is photodynamic therapy (PDT), a therapy which uses cold lasers. The therapy was recently approved in a number of countries including regulatory approval by the Food and Drug Administration (FDA) in the United States. Click here to find status of regulatory approval in a specific country. However, early diagnosis of AMD is key, because once vision is lost due to of the growth of abnormal blood vessels, it cannot be reclaimed by either treatment.

Laser Photocoagulation

The laser provides a concentrated beam of high-energy light that turns to heat when it hits the parts of the retina to be treated. This heat destroys the choroidal neovascularization (CNV) and stops it from growing, leaking, and bleeding. A scar forms as a result of the treatment and this scar creates a permanent blind spot in the field of vision. Vision does not usually improve after laser treatment and in some cases, may even be somewhat worse. Loss of vision following laser, though immediate, is usually less severe than the eventual loss of vision that usually occurs if laser treatment is not done. In many cases, the visual distortion will disappear after laser treatment.

Laser Photocoagulation Success Rate

Laser treatment only works about half the time and is currently the only means of temporarily preventing further loss of vision, or lessening the amount of visual loss that usually occurs if no laser is done. In spite of laser treatment, vision may continue to worsen. But if laser is indicated, the chances are that there will be less visual loss with laser than with no laser treatment. Without laser, loss of central vision will usually continue.

Laser Photocoagulation Vision Changes

 Before laser treatment, people with CNV symptomatic of wet macular degeneration often notice that they have a dark or gray spot in or near their central vision. The laser treatment will cause that spot to become completely and permanently blank, empty, or black. That area of the macula is sacrificed to save the remaining portions of the macula. Even when laser treatment is considered successful, and the CNV has been destroyed, new or additional CNV (abnormal blood vessels) can appear months or years later and further damage vision.

Macular Degeneration