Abstract
Binocular fixation preference testing is commonly used to predict strabismic amblyopia in preverbal children. However, false positives can occur and can lead to unnecessary patching treatment. We explored potential causes for this phenomenon.
In this prospective cohort study (2013-2014) of consecutive verbal strabismic patients without incomitance or decreased vision other than strabismic amblyopia, binocular fixation preference testing was graded from 1 (strong preference) to 4 (free alteration), with grade 1 or 2 considered predictive of amblyopia and the examiner masked to visual acuity. These results were compared to the presence/absence of true strabismic amblyopia. Ocular dominance and hand dominance were assessed, and previous patching history was documented.
Of 114 enrolled subjects (mean age, 7.9 years; range, 3.4-22.4; 63 males), 98 (86%) had esotropia and 16 (14%) had exotropia (mean primary position horizontal strabismus, 27.9(Δ); range, 8(Δ)-70(Δ), with only one <10(Δ)). For the 39 false positives (34%), the fixating eye correlated with ipsilateral ocular dominance (79.5%; P < 0.0001 [χ(2)]) but not with hand dominance or recent patching history. Positive predictive value was poor (45.8%; 95% CI, 34.0%-58.0%), but negative predictive value was high (97.6%; 95% CI, 87.4%-99.6%). Subgroup analysis revealed no significant correlations with degree or type of strabismus.
False positives during binocular fixation preference testing of strabismic patients are common and likely due to contralateral ocular dominance. The test is more useful for predicting the absence rather than the presence of strabismic amblyopia.