Assessment of amblyopic children undergoing occlusion therapy by pattern visual evoked potentials and contrast sensitivity tests

Background: Amblyopia is a case where one or less commonly, both eyes have impaired visual performance, even with the best optical correction and no visible disease of the visual system. Objectives: To assess contrast sensitivity tests (CST) and pattern visual evoked potentials (PVEP) results in amblyopic children who have already started occlusion therapy for durations ranging from 6 to 12 months. Methods: This cross-sectional study was conducted on 200 eyes of 50 patients with monocular amblyopia and 50 age and sex matched controls. Both patients and controls underwent ophthalmological assessment, PVEP, and CST. Results: There was no statistically significant difference in the results of P100 latencies of qualitative PVEP in amblyopic eyes compared to non-amblyopic eyes and control eyes, while the qualitative CST showed a highly statistically significant difference, being affected in 98% of amblyopic eyes compared to unaffected eyes (4%) and control eyes (4%). The maximum contrast level and minimal contrast level of quantitative CST were significantly lower in amblyopic eyes compared to non-amblyopic and control eyes. The cutoff value of maximal contrast level at mean frequencies of 2.5 +/- 0.9 Hz, and a range of (1.1-4.1) for amblyopic eyes is <= 21 dB, while the cutoff value of minimal contrast level at mean frequencies of 13.4 +/- 2.6 Hz, and a range of (6.7-18) for amblyopic eyes is <= 12 dB. Conclusion: Detection of amblyopia by CST is a noninvasive and easy procedure, which represents a promising tool to support the diagnosis of amblyopia.