ABCA4 Gene

Stargardt macular degeneration is a genetic eye disorder that causes progressive vision loss. This disorder affects the retina, the specialized light-sensitive tissue that lines the back of the eye. Specifically, Stargardt macular degeneration affects a small area near the center of the retina called the macula. The macula is responsible for sharp central vision, which is needed for detailed tasks such as reading, driving, and recognizing faces. In most people with Stargardt macular degeneration, a fatty yellow pigment (lipofuscin) builds up in cells underlying the macula. Over time, the abnormal accumulation of this substance can damage cells that are critical for clear central vision. In addition to central vision loss, people with Stargardt macular degeneration have problems with night vision that can make it difficult to navigate in low light. Some affected individuals also have impaired color vision. The signs and symptoms of Stargardt macular degeneration typically appear in late childhood to early adulthood and worsen over time.

Age-related macular degeneration is an eye disease that is a leading cause of vision loss in older people in developed countries. Subtle abnormalities indicating changes in vision may occur in a person's forties or fifties. Distorted vision and vision loss usually become noticeable in a person's sixties or seventies and tend to worsen over time.

Age-related macular degeneration mainly affects central vision, which is needed for detailed tasks such as reading, driving, and recognizing faces. The vision loss in this condition results from a gradual deterioration of light-sensing cells in the tissue at the back of the eye that detects light and color (the retina). Specifically, age-related macular degeneration affects a small area near the center of the retina, called the macula, which is responsible for central vision. Side (peripheral) vision and night vision are generally not affected, but slow adjustment of vision to darkness (dark adaptation) and reduced dim light (scotopic) vision often occur in the early stages of the disease.

Researchers have described two major types of age-related macular degeneration, known as the dry form and the wet form. The dry form is much more common, accounting for 85 to 90 percent of all cases of age-related macular degeneration. It is characterized by a buildup of yellowish deposits called drusen beneath the retina and vision loss that worsens slowly over time. The most advanced stage of dry age-related macular degeneration is known as geographic atrophy, in which areas of the macula waste away (atrophy), resulting in severe vision loss. Dry age-related macular degeneration typically affects vision in both eyes, although vision loss often occurs in one eye before the other.

In 10 to 15 percent of affected individuals, the dry form progresses to the wet form of age-related macular degeneration. The wet form is characterized by the growth of abnormal, fragile blood vessels underneath the macula. These vessels leak blood and fluid, which damages the macula and makes central vision appear blurry and distorted. The wet form of age-related macular degeneration is associated with severe vision loss that can worsen rapidly.

Cone-rod dystrophy is a group of related eye disorders that causes vision loss, which becomes more severe over time. These disorders affect the retina, which is the layer of light-sensitive tissue at the back of the eye. In people with cone-rod dystrophy, vision loss occurs as the light-sensing cells of the retina gradually deteriorate.

The first signs and symptoms of cone-rod dystrophy, which often occur in childhood, are usually decreased sharpness of vision (visual acuity) and increased sensitivity to light (photophobia). These features are typically followed by impaired color vision (dyschromatopsia), blind spots (scotomas) in the center of the visual field, and partial side (peripheral) vision loss. Over time, affected individuals develop night blindness and a worsening of their peripheral vision, which can limit independent mobility. Decreasing visual acuity makes reading increasingly difficult and most affected individuals are legally blind by mid-adulthood. As the condition progresses, individuals may develop involuntary eye movements (nystagmus).

There are more than 30 types of cone-rod dystrophy, which are distinguished by their genetic cause and their pattern of inheritance: autosomal recessive, autosomal dominant, and X-linked. Additionally, cone-rod dystrophy can occur alone without any other signs and symptoms or it can occur as part of a syndrome that affects multiple parts of the body.

Retinitis pigmentosa is a group of related eye disorders that cause progressive vision loss. These disorders affect the retina, which is the layer of light-sensitive tissue at the back of the eye. In people with retinitis pigmentosa, vision loss occurs as the light-sensing cells of the retina gradually deteriorate.

The first sign of retinitis pigmentosa is usually a loss of night vision, which becomes apparent in childhood. Problems with night vision can make it difficult to navigate in low light. Later, the disease causes blind spots to develop in the side (peripheral) vision. Over time, these blind spots merge to produce tunnel vision. The disease progresses over years or decades to affect central vision, which is needed for detailed tasks such as reading, driving, and recognizing faces. In adulthood, many people with retinitis pigmentosa become legally blind.

The signs and symptoms of retinitis pigmentosa are most often limited to vision loss. When the disorder occurs by itself, it is described as nonsyndromic. Researchers have identified several major types of nonsyndromic retinitis pigmentosa, which are usually distinguished by their pattern of inheritance: autosomal dominant, autosomal recessive, or X-linked.

Less commonly, retinitis pigmentosa occurs as part of syndromes that affect other organs and tissues in the body. These forms of the disease are described as syndromic. The most common form of syndromic retinitis pigmentosa is Usher syndrome, which is characterized by the combination of vision loss and hearing loss beginning early in life. Retinitis pigmentosa is also a feature of several other genetic syndromes, including Bardet-Biedl syndrome; Refsum disease; and neuropathy, ataxia, and retinitis pigmentosa (NARP).

Age-related macular degeneration is an eye disease that is a leading cause of vision loss in older people in developed countries. Subtle abnormalities indicating changes in vision may occur in a person's forties or fifties. Distorted vision and vision loss usually become noticeable in a person's sixties or seventies and tend to worsen over time.

Age-related macular degeneration mainly affects central vision, which is needed for detailed tasks such as reading, driving, and recognizing faces. The vision loss in this condition results from a gradual deterioration of light-sensing cells in the tissue at the back of the eye that detects light and color (the retina). Specifically, age-related macular degeneration affects a small area near the center of the retina, called the macula, which is responsible for central vision. Side (peripheral) vision and night vision are generally not affected, but slow adjustment of vision to darkness (dark adaptation) and reduced dim light (scotopic) vision often occur in the early stages of the disease.

Researchers have described two major types of age-related macular degeneration, known as the dry form and the wet form. The dry form is much more common, accounting for 85 to 90 percent of all cases of age-related macular degeneration. It is characterized by a buildup of yellowish deposits called drusen beneath the retina and vision loss that worsens slowly over time. The most advanced stage of dry age-related macular degeneration is known as geographic atrophy, in which areas of the macula waste away (atrophy), resulting in severe vision loss. Dry age-related macular degeneration typically affects vision in both eyes, although vision loss often occurs in one eye before the other.

In 10 to 15 percent of affected individuals, the dry form progresses to the wet form of age-related macular degeneration. The wet form is characterized by the growth of abnormal, fragile blood vessels underneath the macula. These vessels leak blood and fluid, which damages the macula and makes central vision appear blurry and distorted. The wet form of age-related macular degeneration is associated with severe vision loss that can worsen rapidly.