AMD is a disorder of the retina that occurs in persons over 50 years old. AMD has characteristic lesions. By lesions we mean abnormal changes in the appearance and structure of retina. These lesions are not caused by other eye conditions, but are a unique feature of AMD.

To help you understand what AMD looks like when your ophthalmologist looks at the back of your eye, we refer you to the photographs below showing fundus photos of the retina. The top left (A) is from an older person who does not have AMD. Top right (B) is a person with early AMD. Lower left (C) is late non-exudative AMD (also called geographic atrophy), and finally lower right (D) is someone who has late exudative AMD ("wet" AMD). We will explain what we mean by these different types of AMD below.

A		B
(Click each image for larger version.)
C		D

The characteristic lesions in AMD are drusen and changes in pigmentation. A person does not have to have all these lesions to have AMD, but can have only one or just a few.

Drusen are well-defined lumps of fatty debris under the retinal pigment epithelium. They can be seen as yellow or white spots in the fundus, shown in panel B above. Most older persons have at least a few hard (discrete) drusen, as in panel A.

Similar debris also forms a thin layer under the retinal pigment epithelium and cannot be seen in the fundus.

The pigment content of individual retinal pigment epithelium cells increases or decreases, creating dark or light areas in the macula. Blood vessels grow in from the choriocapillaris under the retina (choroidal neovascularization). The consequences of abnormal vessel growth are hemorrhage and scar formation.

A person does not have to have all these lesions to have AMD, but can have only one or just a few.

AMD is known by several names, the most popular names being dry and wet.

Dry AMD consists of drusen and changes in the pigmentation of the retinal pigment epithelium that can be seen in the back of the eye. Some individuals with drusen and pigment changes may advance to extensive loss of the retinal pigment epithelium in the macula. This is often referred to as geographic atrophy (Panel C above).

Wet AMD is a complication of dry AMD in which blood vessels from the choriocapillaris break through Bruch’s membrane and spread under either the retinal pigment epithelium, the retina, or both. This process is called choroidal neovascularization (new vessels), and the result is a delicate tissue called a neovascular membrane. Vessels in neovascular membranes may leak or bleed, detaching the retina from the retinal pigment epithelium. See Panel D above for an eye with wet AMD. A scar may eventually form. Fluorescein angiography is a method to reveal blood vessels in the retina using a dye injected into the bloodstream and a special camera. This technique is used to diagnose neovascularization.

Neovascular membranes that are well defined in fluorescein angiography are described as classic, and those that are poorly defined are described as occult.

These are examples of the technical terms that your ophthalmologist or optometrist will use to characterize your condition from a medical standpoint. AMD itself is not physically painful to patients. What is most noticeable to the patient is decreased vision. This impaired vision in either dry or wet AMD is due to the degeneration and/or death of photoreceptors. Recall that photoreceptors capture light rays reflecting off the objects you look at. Photoreceptors convert the light to electrical energy so that information about your visual world can be transmitted to the brain. Without healthy photoreceptors, vision will be degraded.

One other thing we should mention is that age-related macular degeneration can be referred as ARM, ARMD, and AMD. These terms are interchangeable, and should not be a cause for confusion in your reading about this disease. An international panel of experts agreed to call early disease "ARM" and late disease (geographic atrophy or choroidal neovascularization) "AMD," but use of this terminology is by no means universal.