Colobomas are missing pieces of tissue in the eye structures that form before birth as a result of abnormal eye development. They usually look like notches or gaps in one of several parts of the eye, including the eyelids, the iris (the colored part of the eye); the lens; the retina (the specialized light-sensitive tissue that lines the back of the eye); the choroid ( the blood vessel layer under the retina); or the optic nerves, which carry information from the eyes to the brain.
Colobomas may be present in one or both eyes and, depending on their size and location, can affect a person's vision. They may isolated defects, or associated with defects in other organs (e.g., CHARGE syndrome, which includes coloboma of the eye, heart defects, atresia of the nasal choanae (special nasal bones that are too narrow or absent), retardation of growth and/or development, genital and/or urinary abnormalities, and ear abnormalities and deafness).
Most often, isolated coloboma is not inherited, but the affected individual may still pass it on to his or her own children. In cases when it is passed down in families, there different inheritance patterns: 1- autosomal dominant, which means one copy of an altered gene in each cell is sufficient to cause the disorder; 2- autosomal recessive, which means both copies of a gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of a mutated gene, but they typically do not show signs and symptoms of the condition; 3- Less commonly, X-linked dominant or X-linked recessive patterns, which means that the affected gene is located on the X chromosome (one of the two sex chromosomes). In X-linked inheritance, fathers cannot pass X-linked traits to their sons (sons take the X from their mothers and the Y from their fathers).
Colobomas may be present in one or both eyes and, depending on their size and location, can affect a person's vision. They may isolated defects, or associated with defects in other organs (e.g., CHARGE syndrome, which includes coloboma of the eye, heart defects, atresia of the nasal choanae (special nasal bones that are too narrow or absent), retardation of growth and/or development, genital and/or urinary abnormalities, and ear abnormalities and deafness).
Most often, isolated coloboma is not inherited, but the affected individual may still pass it on to his or her own children. In cases when it is passed down in families, there different inheritance patterns: 1- autosomal dominant, which means one copy of an altered gene in each cell is sufficient to cause the disorder; 2- autosomal recessive, which means both copies of a gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of a mutated gene, but they typically do not show signs and symptoms of the condition; 3- Less commonly, X-linked dominant or X-linked recessive patterns, which means that the affected gene is located on the X chromosome (one of the two sex chromosomes). In X-linked inheritance, fathers cannot pass X-linked traits to their sons (sons take the X from their mothers and the Y from their fathers).
•
