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Accommodation: Change in the shape of the lens to compensate for changes in focal length. The term is also used more generally to mean the adjustment of the eye in general to compensate for focusing on objects at different distances.

Amblyopia: Poor, uncorrectable monocular (and rarely binocular) vision that is cortical in nature and not attributable to a structural abnormality of the eye or visual pathway. This may be a result of strabismus, high uncorrected refractive error, or visual deprivation during the critical period of cortical visual development during childhood.

Esotropia: Deviation of the eyes inward when compared with normal alignment.

Exotropia: Deviation of the eyes outward when compared with normal alignment.

Relative afferent pupillary defect (RAPD): The "swinging flashlight test" in a darkened room is used to test for a RAPD. The pupillary response should be equal in both eyes. A RAPD is detected when there is a relative difference in the pupillary response to a direct and consensual light stimulus between the two eyes. An eye with a RAPD will (abnormally) dilate with direct light to the eye but constrict normally in response to light shined in the fellow eye. A RAPD is seen when there is optic nerve damage or significant retinal disease (e.g., large retinal detachment, retinal artery occlusion, optic neuritis). One will not get a RAPD in refractive errors, vitreous bleeds, etc.

Strabismus: A general term that refers to a misalignment of the eyes. Esotropia, exotropia, and hypertropia (one eye deviated upward) are all examples of strabismus. The term strabismus says nothing about etiology, which can be congenital, neurologic, or muscular.

CASE 19.1

A mother presents with her healthy, 2-month-old male infant. She reports that for the past week his eyes have been noticeably crossed. He appears to fixate with either the right or left eye. She feels that aside from being cross-eyed, he seems to see well. On examination, his eyes are very crossed. When either eye is covered, he fixes and follows with the fellow eye and appears to have normal motility.

Question 19.1.1 The most likely diagnosis in this patient is:

A) Pseudoesotropia

B) Congenital esotropia

C) Accommodative esotropia

D) Sixth nerve palsy

Answer 19.1.1 The correct answer is "B." Esotropia is more common than exotropia. Congenital esotropia is generally found in children younger than 6 months. "C," accommodative esotropia, is the most common cause of esotropia in childhood and develops between age 6 months and 7 years. It is rare for accommodative esotropia to develop before 4 months or after 8 years of age. Pseudoesotropia is common in ...

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