Relationship of Fixation Preference to Amblyopia in Preschool Children: The Multi-Ethnic Pediatric Eye Disease Study

Abstract

 

Purpose:

 

To compare the clinical assessment of fixation preference (FP) testing to amblyopia status in preschool children.

 

Methods:

 

3048 children aged 30-72 months from the population-based Multi-Ethnic Pediatric Eye Disease Study were testable both on FP testing and subsequent visual acuity (VA) testing (Amblyopia Treatment Study HOTV protocol) during a comprehensive eye examination. VA was re-tested with refractive correction in those with abnormal VA. Unilateral amblyopia was defined as a 2-line final interocular (IOD) VA difference with 20/32 or worse vision in the worse-seeing eye in the presence of a unilateral amblyogenic risk factor (strabismus, anisometropia, or form deprivation). In children with apparent strabismus, FP was assessed by observation of the fixating eye and in those with no manifest or small-angle deviations (<=10 pd), it was assessed with the induced-tropia test (12pd BD prism). A standardized protocol was used to grade the length of time the non-preferred eye held fixation (A=spontaneous alternation, B=holds well, C=holds momentarily, and D=will not hold). FP grade was compared with the diagnosis of amblyopia.

 

Results:

 

FP grade and amblyopia status for 3048 children were:Of children with unilateral amblyopia, 70% (38/54) had grade A/B and 30% (16/54) had grade C/D. FP grade A was seen both in mild amblyopia (66% of 41 cases with 2-3 line IOD) and more severe amblyopia (54% of 13 cases with >=4 line IOD). 69% (27/39) of children with isolated anisometropic amblyopia and 30% (3/10) with isolated strabismic amblyopia had FP grade A. 72% (18/25) of non-amblyopes with a 0-1 line IOD and FP grade C/D had strabismus.  

 

Conclusions:

 

FP testing is not highly predictive of amblyopia. Strong FP (grade C/D) is often seen in strabismic children without amblyopia. The majority of children with anisometropic amblyopia do not show a FP (grade A/B). Therefore, clinicians should be cautious when using FP as a surrogate measure of visual acuity for diagnosis and follow up of preverbal children with amblyopia risk factors.

 

Keywords: amblyopia • detection • visual acuity