Fusional divergence amplitude was measured with basein prisms of increasing power starting from the base-in prism totally correcting the exodeviation. Break point and recovery point of fusional divergence amplitude were recorded.
In terms of level of control of the deviation, exodeviations may be distinguished into exophoria (XPH), intermittent exotropia (IXT), and exotropia (XT).
These concepts have proved to be misleading, because at present no scientific evidence exists for excessive tonic divergence innervation in XT and convergence insufficiency pattern exodeviations not necessarily have a distant near point of convergence (NPC).
Very often large intermittent exodeviations go along with wide convergence fusional amplitudes, and these latter seem to chase the deviation, in the sense that the larger the deviation, the wider the convergence fusional amplitude.
Intermittent exotropia, which sometimes begins as exophoria, is the most common fotm of exodeviation. Many researchers consider it a progressive disease that can transform into constant exotropia (1-4) and report that 75% of patients require surgical correction within 20 years of its diagnosis.
reported that during a mean 1-year follow-up of 100 intermittent exotropia cases, the success rate was 45.7% for all consecutive esotropia cases in the unsuccessful surgery group without taking into consideration the postoperative level of deviation; (19) however, many researchers agree that in the early post surgery period exodeviation is a desired result, because of the tendency for exodeviation after surgery.
(11,16,24-26) Moreover, at the 6-month post-surgery follow-up, we observed that there were 2 measures that predicted success orthophoric and residual exodeviation [less than or equal to] 10 PD.
Exodeviations: their classification, diagnosis and treatment.