Purpose To assess the prevalence of astigmatism and its relationship with biometric optic components in preterm school children with diode laser-treated threshold retinopathy of prematurity (ROP). Methods A prospective, cross-sectional study in which cycloplegic keratometry, refraction, and ultrasound biometric measurement of optic components were performed on 24 consecutive preterm children with diode laser-treated threshold ROP at the age of 9 years. The study results were compared with data on 1021 agematched full-term control children from a national survey. Results The laser-treated eyes had a mean astigmatism of 3.47 D, with a mean spherical equivalent of À 4.49 D. Of the 46 eyes studied, 98% of eyes showed astigmatism Z0.5 D and 50% had high astigmatism (43.0 D). Most astigmatic eyes (97.7%) showed with-the-rule astigmatism, with the mean plus cylinder axis at 89.30 o . Further correlation analysis showed the astigmatism in refraction was highly correlated with the corneal astigmatism (r ¼ 0.921, Po0.001) and the vertical corneal curvature (r ¼ 0.405, P ¼ 0.005). There was significantly steeper vertical corneal curvature (P ¼ 0.003) and flatter horizontal corneal curvature (P ¼ 0.031) in eyes with laser-treated ROP when compared with age-matched full-term controls. The eyes with laser-treated ROP also show significantly thicker lens (3.93 mm) and shallower anterior chamber depth (ACD; 2.92 mm) than full-term controls (Po0.001). Conclusions There is significantly higher prevalence and greater magnitude of astigmatism in eyes with laser-treated threshold ROP compared with full-term controls. The steeper vertical corneal curvature component contributes to the increased astigmatism in eyes with laser-treated ROP.

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