In an initial discussion of asthenopia the examiner must determine whether a patient has a specific reading problem or a more generalized learning disorder. The patient with a typical reading disorder shows a disproportionate defect in reading ability while performing adequately or, at times superiorly, in other academic subjects.

 Uncorrected hypermetropia or astigmatism may contribute to poor reading performance. In such cases, the appropriate correction should be prescribed.

 A rare cause of reading difficulties is premature presbyopia. The near point of accommodation is reduced  and prescription of reading glasses or bifocals remedy this problem.

Convergence insufficiency  causes asthenopia at near vision and may contribute to poor reading performance. Orthoptic exercises are indicated.

Another cause of reading difficulties is heterophoria . Efforts to maintain fusion in the presence of a large heterophoria may decrease reading performance; this may require surgery or orthoptic exercises.

An A pattern exotropia or exophoria or a V pattern esotropia ( as in our case ) or esophoria  may cause diplopia or asthenopia in downward gaze and must be ruled out as a cause for poor reading performance. 

In a case like this the rule of up/down shifting  of the horizontal recti must be added to the corrective surgery of the horizontal deviation to also solve the problem of A/V pattern that causing the reading difficulties