Strabismus

Strabismus is a condition that interferes with binocular vision because it prevents a person from directing both eyes simultaneously towards the same fixation point; the eyes do not properly align with each other. Heterotropia is a medical synonym for the condition. Colloquial terms for strabismus include "cross-eye", "wall-eye", and a "cast of the eye".

Strabismus typically involves a lack of coordination between the extraocular muscles, which prevents directing the gaze of both eyes at once to the same point in space; it thus hampers proper binocular vision, and may affect depth perception adversely. Strabismus is primarily managed by ophthalmologists, optometrists, and orthoptists. Strabismus is present in about 4% of children. Treatment should be started as early as possible to ensure the development of the best possible visual acuity and stereopsis. It is from the Greek strabismós.

Signs and symptoms

When observing a patient with strabismus, the misalignment of the eyes may be quite apparent. A patient with a constant eye turn of significant magnitude is very easy to notice. However, a small magnitude or intermittent strabismus can easily be missed upon casual observation. In any case, an eye care professional can conduct various tests, such as cover testing, to determine the full extent of the strabismus.

Strabismus (protein)

Strabismus was originally identified as a Drosophila protein involved in planar cell polarity. Flies with mutated strabismus genes have altered development of omatidia in their eyes. Vertebrates have two Strabismus-related proteins, VANGL1 and VANGL2 (an alternate name for the Drosophila "Strabismus" protein is "Van Gogh").

The amino acid sequence and localization studies for Strabismus indicate that it is a membrane protein. Prickle is another protein in the planar cell polarity signaling pathway. Prickle is recruited to the cell surface membrane by strabismus. In cells of the developing Drosophila wing, Prickle and Strabismus are concentrated at the cell surface membrane on the most proximal side of cells.

Vertebrate cell movement

VANGL2 is involved in the migration of groups of cells during vertebrate embryogenesis.

Humans

In humans, mutations in VANGL1 have been associated with neural tube defects including spina bifida, and with some forms of cancer including hepatocellular carcinoma.