Genetic diseases are those that are passed on from parent to child through genes that carry the codes for each specific trait. Many of the diseases and disorders that affect the eyes have genetic factors. Some diseases are linked to a single gene and is either dominant, meaning it only requires one gene copy to express the trait, or recessive, which requires two copies of the gene. Other diseases are known to run in families but are affected by a number of genetic factors.
Congenital Cataracts
Congenital cataracts are responsible for more than 60 percent of all cases of blindness among infants, according to the Cleveland Clinic. A cataract is a condition that occurs when the lens of the eye becomes foggy, inhibiting vision. Although cataracts commonly occur as a result of aging, defective genes can cause cataract formation in the fetus and in early childhood.
A study published in the Journal of Medical Genetics reveals that some inherited cataracts are linked to dominant genes, while others may be linked to recessive genes. Because several genes and mutations may be responsible, how the genes affect each person and the progression of the cataracts may differ among family members.
Retinitis Pigmentosa
Retinitis pigmentosa is the name for a group of genetic diseases that cause degeneration of the retina. The retina is the light-sensitive membrane that covers the back of the eye and is responsible for capturing images. The retina contains two types of photo-receptor cells: rods and cones. Conditions of retinitis pigmentosa involve the destruction of the rods and cones, which causes a decline in vision.
There are several different diseases classified as retinitis pigmentosa, including Usher Syndrome, Leber's congenital amaurosis, rod-cone disease, Bardet-Biedl syndrome and Refsum disease. These diseases are caused by mutations in genes, usually more than one gene, that signal the body to produce too little or too much of a protein, which interferes with normal retinal function. The foundation Fighting Blindness estimates that 100,000 people in the United States suffer from some form of retinitis pigmentosa.
Strabismus
Strabismus is a condition that occurs when both eyes cannot be aligned together. This is often referred to as cross-eye or lazy eye and can cause double vision. There are several different types of strabismus and several factors that cause this condition. Genetics is one factor, as the UIC Department of Ophthalmolgy and Visual Sciences reports that if one child has strabismus, there is a 15 percent chance that a sibling will also have it.
Glaucoma
Glaucoma is a group of diseases that causes a gradual loss of vision due to damage to the optic nerve. The optic nerve is what connects the eyes to the brain and is responsible for carrying images to the brain. Many types of glaucoma, including the most common form of primary open-angle glaucoma, are known to run in families.
