Changing the paradigm of soft contact lens fitting: A sagittal height-based approach

Abstract

Objective: The present study evaluated the correlation between ocular sagittal height and lens sagittal depth, specifically focusing on the sagittal difference (δsag) that defines an optimal lens fit. Methods: The ocular sagittal height (spanning a 14.2-mm chord in the ocular surface flattest meridian) of 30 subjects was measured using the Oculus Pentacam HR. Participants were fitted with eight different standard daily disposable soft contact lenses, each having a known sagittal depth. To evaluate the fit, both objective methods (using ImageJ software) and subjective assessments (by two experienced eye care professionals [ECPs]) were employed. Descriptive statistics were obtained for different δ-sag, and correlations and a regression model were applied to determine the δ-sag range indicative of a satisfactory lens fit, based on the objective and subjective evaluations. Results: The δ-sag achieved in most cases ranged between 200 and 600μm. Participants reported high comfort levels independently of δ-sag (H=8.99; p=0.25) and type of contact lens (χ 2=1.47; p=0.98). Significant correlations were found between δ-sag and objective assessments of lens centration (inferior, nasal and temporal) and movement (nasal lag). The regression model, based on the subjective assessment conducted by the ECPs, yielded a δ-sag of between 120 and 280μm for a score considered as good. Conclusions: Objective and subjective assessments showed significant associations with δ-sag. A standard cast-moulded disposable soft contact lens whose sagittal depth exceeded the ocular sagitta corresponding to the chord equivalent to the total contact lens diameter by 120–280μm would most likely result in an optimal fit. These findings could help improve fitting accuracy and reduce dropout rates, thereby enhancing patient experience and ocular health.