Abstract
BACKGROUND: Amblyopia is associated with structural differences in ocular biometrics, but existing studies often lack long-term follow-ups. This study compares three-year changes in ocular biometric components in amblyopic and non-amblyopic eyes. METHODS: In this prospective cohort, study data were collected in 2015 and 2018 in Shahroud, northeast Iran. The sample comprised 4968 primary students (9935 eyes), including 4931 non-amblyopic students (9893 eyes) and 37 students with amblyopia (42 eyes). Axial length, keratometry, central corneal thickness, lens thickness, pupil diameter, anterior chamber depth, lens power and vitreous chamber depth were measured using Lenstar LS900. Multilevel mixed-effects regression models were used to determine any association between variables. RESULTS: The mean age of children without and with amblyopia at baseline were 9.7 ± 1.7 and 9.9 ± 1.5 years, respectively. The mean axial elongation in amblyopic and non-amblyopic groups over three years was 0.37 (95% CI: 0.34-0.40) and 0.33 mm (95% CI: 0.31-0.34), respectively (p < 0.001). Amblyopic eyes showed greater axial elongation than non-amblyopic eyes (p < 0.001). Anterior chamber depth was constant in amblyopic eyes while it decreased in non-amblyopic eyes by 0.13 mm. Vitreous chamber depth increased significantly in both groups, with a greater increase observed in the amblyopic eyes (0.36 vs. 0.28 mm) (p < 0.001). Flat and steep keratometry increased significantly in amblyopic eyes (p < 0.001), while it was constant in non-amblyopic eyes. Lens power decreased significantly in both groups (p < 0.001). The increase in the axial length and vitreous chamber depth in the amblyopic eye was greater than in the non-amblyopic eyes (p < 0.001). The spherical equivalent change in both groups was - 0.31 D. CONCLUSIONS: Amblyopia was associated with significant changes in key biometric parameters, offering valuable insight into the structural alterations underlying the condition.