Ophthalmic Glossary

A type of incomitant strabismus characterized by a difference in the horizontal deviation between upgaze and downgaze of at least 10 prism diopters. In A pattern exotropia, the outward deviation is greater in downgaze than in upgaze. In A pattern esotropia, the inward deviation is greater in upgaze than in downgaze. Etiologies may include superior oblique overaction, orbital pulley abnormalities, or ocular torsion.

Cranial Nerve VI is a somatic efferent nerve that innervates the lateral rectus muscle of the eye. It originates from the abducens nucleus in the pons and emerges at the pontomedullary junction. The nerve travels through the subarachnoid space, cavernous sinus, and superior orbital fissure to reach the lateral rectus muscle, enabling abduction of the eye. Damage to the abducens nerve results in impaired lateral eye movement and esotropia.

Abduction is the outward movement of the eye towards the temple. It is controlled by the lateral rectus muscle, which is innervated by the abducens nerve (cranial nerve VI).

Aberrant regeneration is a possible sequela of an oculomotor nerve palsy, resulting in abnormal lid, pupillary, and ocular motility. It occurs when regenerating axons are misdirected to anomalous connections within the oculomotor nerve. Common signs include lid elevation on adduction (pseudo-Graefe’s sign) or infraduction, and pupillary constriction on adduction. The most frequent causes are trauma, tumors, and aneurysms. Onset typically appears within 6-12 months after the initial injury.

The eye’s ability to adjust its refractive power by changing the shape of the crystalline lens, allowing objects at various distances to be focused on the retina. This process is mediated by the ciliary muscle and zonular fibers, which control lens curvature. Accommodation is a dynamic response to blurred retinal images, with the goal of maximizing image sharpness. The accommodative range decreases with age due to lens stiffening, resulting in presbyopia.

The inward movement of the eyes that occurs in conjunction with the accommodation reflex when viewing near objects. As the crystalline lens changes shape to focus on a closer target, a neurological link triggers the medial rectus muscles to converge the eyes. This convergence response is proportional to the amount of accommodation and helps maintain binocular fusion and clear single vision at near distances.

The convergence response of an individual to a unit stimulus of accommodation, expressed as the quotient of accommodative convergence in prism diopters divided by the accommodative stimulus in diopters.

Adduction is the inward movement of the eye towards the nose. It is controlled by the medial rectus muscle, which is innervated by the oculomotor nerve (cranial nerve III).

A technique used in strabismus surgery where the extraocular muscle is reattached to the sclera using sutures with temporary knots. After the patient recovers from anesthesia, the knots can be adjusted to modify the final muscle position and eye alignment.