It is unknown whether myopia development or progression could trigger IXT, or whether the reverse is true.
(18) Similarly for Ajay, shifting from a spectacle correction where an IXT, which was nearly constant, could lead to decompensation into a constant exotropia.
The sensory status in IXT is double as normal binocular vision alternates with suppression of the deviated eye.
Recently, a study regarding a wide number of IXT patients found no strong associations between stereopsis, amount of strabismus, and control of the deviation .
It is generally believed that in IXT patients, tonic convergence and accommodation through accommodative convergence contribute to maintain ocular alignment at near fixation .
Instead, in IXT patients, the so-called phoria-myopia response occurs at near fixation [6, 7].
In patients with IXT, a greater effort to converge is required to fixate a near target binocularly compared with patients with orthophoria.
IXT patients are reported to have high convergence fusional amplitudes that they use to compensate the deviation .
The control of the deviation is commonly indirectly deduced during the follow-up from signs like degraded stereopsis, onset of amblyopia, increased deviation, or symptoms like asthenopia, visual discomfort, and diplopia, even if in IXT suppression usually protects from diplopia.
To investigate the relationships between angle of deviation, fusional convergence and divergence amplitudes, AC/A ratio, NPC, and myopia-phoria in IXT, we studied a series of patients referred to our department in the last five years.
Ninety-three patients with IXT were recruited in the study.