A Quantitative Study of Inter-Ocular Suppression in Children with Amblyopia

Objective: To assess the reliability and relevance of a new test of inter-ocular suppression for children with amblyopia, as well as its sensitivity and specificity for clinical use. Methods: In this prospective study, inter-ocular suppression was measured quantitatively with polarized and neutral density filter lenses with visual targets both for near and distance, and then compared to the standard tests for suppression (Worth 4 dot, stereoacuity) in 29 amblyopic children (8.7±2.4 years) with strabismus, anisometropia, or a combination of both and 20 age-matched normal controls (8.0±1.9 years), from May 2014 to September 2017 in the Eye Hospital, Wenzhou Medical University. To evaluate the correlation between measurement results and clinical characteristics of children in the amblyopia group, a Wilcoxon signed-rank sum test was used for analysis. A receiver operating characteristic curve was adopted to assess its reliability, sensitivity and specificity. Results: There was no statistically significant difference between the performance of normal and amblyopic patients (Z=1.830, P=0.067; Z=0.653, P=0.514). Inter-ocular suppression with the Worth 4-dot test was used as the diagnostic criteria. The results showed that stronger inter-ocular suppression was found in amblyopes than in controls at both near (Z=2.974, P=0.003) and far distances (Z= 3.580, P<0.001). Using TNO and Optec 3500 as the diagnostic criteria, the results showed that stronger inter-ocular suppression was found in amblyopes than in controls at both near (Z=2.142, P=0.032) and far distances (Z=2.031, P=0.042). Inter-ocular suppression using the new test for diagnosis to distinguish between inhibition and non-inhibition showed the results were statistically significant for the diagnosis of differential inhibition and no inhibition. The results for the diagnostic criteria for the Worth 4-dot detection were: Near: AUC=0.824, 95%CI: 0.672-0.975, P=0.003; Far: AUC=0.911, 95%CI: 0.798-1.000, P<0.001; Diagnosis criteria for the TNO and Optec 3500 were: Near: AUC=0.878, 95%CI: 0.724-1.000, P=0.035; Far: AUC=0.926, 95%CI: 0.819-1.000, P=0.048). Conclusions: Good reliability and agreement is suggested for the new quantitative measurement of suppression in children with amblyopia. The measured inter-ocular suppression is in agreement with other clinical measures. Key words: amblyopia; inter-ocular suppression; quantitative detection; children