Do hyperopic eyes have narrower iridocorneal angles than myopic eyes at the same anterior chamber depth? A matched study

PURPOSE: To compare iridocorneal angle (ICA) and other anterior segment anatomical parameters between hyperopic and myopic eyes with the same anterior chamber depth (ACD), which could have important implications for hyperopic posterior chamber phakic intraocular lens (PC-pIOL) implantation. SETTING: Private eye hospital. DESIGN: Retrospective observational study. METHODS: ACD, ICA, anterior chamber volume (ACV), white-to-white (WTW), and spherical equivalent were obtained from records of patients aged 21-55 and analysed using paired and regression approaches. Hyperopic and myopic eyes were matched 1:1 by ACD and compared with paired t-tests. Analysis of covariance was performed with ICA as the dependent variable, refractive group as the fixed factor and ACD as a covariate. An ICA ≥ 35 degrees was defined as a sufficiently wide angle. RESULTS: Forty-four hyperopic and 72 myopic eyes were included. In the paired analysis, ICA and ACV did not differ significantly between groups (p = 0.356 and 0.446 respectively). In the regression analysis, refractive group was not a significant predictor of ICA after adjustment for ACD (p = 0.193). The proportion of eyes with wide ICA increased with ACD but did not differ between groups. CONCLUSION: We found no statistically significant anatomical difference in Scheimpflug-measured ICA and ACV between hyperopic and myopic eyes with the same ACD in this population. Nevertheless, the current thicker hyperopic lens design without a central hole remains an important reason for exercising greater caution with hyperopic PC-pIOL implantation.