Comparison of the effectiveness of visual acuity measurements for amblyopia screening at the age of 36 and 45 months and difference in severity of amblyopia detected

Purpose: Efficiency of visual screening using visual acuity measurement (VAM) in children screened at 45 months of age (45 m) and screened at both 36 months of age (36 m) and 45 m was investigated by determining failure, repeat and referral rates and amblyopia detection. Methods: Data from Dutch screening records and treating orthoptists of 10 811 children born July 2011–June 2012 were analysed. Based on the national vision screening guideline, the screening outcome was identified as: sufficient/insufficient/non-cooperative VAM, repeat examination or referral. Data analysis consisted of determining (1) non-cooperative and insufficient VAM rates at 45 m, (2) 45 m referral policy after insufficient and non-cooperative VAM, (3) 45 m outcome for non-cooperative or insufficient VAM without referral at 36 m, (4) efficiency of amblyopia detection at 36 or 45 m and (5) amblyopia severity and type. Results: Overall, at 45 m, 8.3% were non-cooperative and 15.6% had insufficient VAM. Regarding efficiency, at 45 m, 1.47 VAMs were needed to detect one case of amblyopia (N = 86), as compared to 1.80 at 36 m (N = 131). The median [IQR] logMAR visual acuity of amblyopic eyes detected at 36 m (0.58 [0.30]) was lower as compared to 45 m (0.52 [0.26]) (p = 0.01) and the interocular difference was larger (p = 0.05). At 45 m, 86 amblyopes were detected; 77 of these had had a VAM at 36 m but had not been referred: 38 passed VAM at 36 m, and referral of 39 was not realized. Conclusion: Visual acuity measurement at 45 m was more efficient as compared to 36 m. The non-cooperative rate at 45 m (8.3%) was lower than previously reported for 36 m (16.6%). Half the amblyopes detected at 45 m had had a sufficient VAM at 36 m.