Cluster analysis reveals patterns of age-related change in anterior chamber depth for gender and ethnicity: clinical implications.

To identify patterns of age-, gender- and refractive- related changes in Scheimpflug-based anterior chamber depth across the central 8 mm of chamber width, to derive normative models, potentially useful for angle closure disease diagnosis. This was a retrospective, cross-sectional study. Scheimpflug photography was used to obtain anterior chamber depth measurements at 57 points across the central 8 mm of the chamber width from one eye of each healthy subject (male Caucasians (n = 189), female Caucasians (n = 186), male Asians (n = 165) and female Asians (n = 181)). Sliding window and nonlinear regression analysis was used to identify the age-related changes in chamber depth. Hierarchical cluster analysis was used to identify test locations with statistically identical age-related shifts, which were used to perform age-correction for all subjects, resulting in normative distributions of chamber depth across the chamber width. The model was examined with and without the contribution of spherical equivalent refractive error. Distinct clusters, demonstrating statistically indistinguishable age-related changes of chamber depth over time, were identified. These age-related changes followed a nonlinear regression (fifth or sixth order polynomial). Females tended to have a greater rate of chamber depth shallowing. Incorporating refractive error into the model produced minimal changes to the fit relative to the ground truth. Comparisons with cut-offs for angle closure from the literature showed that ageing alone was insufficient for identifying angle closure disease. Age-, ethnicity- and gender-related differences need to be acknowledged in order to utilise anterior chamber depth data for angle closure disease diagnosis correctly. Ageing alone does not adequately account for the angle closure disease process.

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