Comparison of corneoscleral topographic consistency in eyes with low-to-moderate and high astigmatism

This study aimed to compare the corneoscleral topographic consistency between eyes with low-to-moderate and high refractive astigmatism (RA).

A total of 131 eyes of 69 participants with astigmatism (51 females and 18 males) and no ocular diseases or history of ocular surgery were included in this study. Participants were divided into a low-to-moderate astigmatism (LMA) group (|RA| ≤ 2.50 D; mean 1.57 ± 0.71 DC; n = 94 eyes) and a high astigmatism (HA) group (|RA| > 2.50 D; mean 3.72 ± 1.08 DC; n = 37 eyes). Corneoscleral topography was acquired via Anterior Segment Analyzer (Scansys TA517). The measurement repeatability at 8-mm and 14-mm chord lengths was examined using Bland-Altman approach. Intraclass correlation coefficient (ICC) between the corneal and scleral shapes was used to calculate corneoscleral topographic consistency. Inter-eye ICC of corneoscleral shape were compared in participants exhibiting a marked interocular astigmatic asymmetry (≥ 1.50 DC).

The 8-mm chord lengths demonstrated superior repeatability, with narrower limits of agreement (LoA: 0.356 ± 0.029 mm; range 0.312 to 0.406 mm) compared to the 14-mm chord (LoA: 0.541 ± 0.058 mm; range 0.429 to 0.648 mm). The eyes with HA showed stronger corneoscleral topographic consistency (mean ICC = 0.54 ± 0.19) than those with LMA (mean ICC = 0.34 ± 0.37, t = -3.96, p < 0.001). In participants with interocular astigmatic asymmetry, the eye with greater astigmatic power exhibited a significantly higher corneoscleral topographic consistency (mean ICC = 0.67 ± 0.20) than the contralateral eye (mean ICC = 0.32 ± 0.24, t = 3.09, p = 0.01).

Eyes with HA exhibited greater corneoscleral topographic consistency than those with LMA. This finding may help with scleral lens fitting in participants with corneal and refractive astigmatism in the absence of scleral shape data.