The Precision of Ophthalmic Calipers: A Potential Reason for Clinical and Surgical Errors

Purpose The study aimed to determine the precision of different ophthalmic calipers used in our tertiary eye care center. Methods All Castroviejo calipers available in the operating room, minor treatment room, and intravitreal injection clinic were included in the study. All calipers were evaluated at four screening points (1, 5, 10, and 15 mm) on a standard ruler and compared to their expected corresponding readings on the caliper scale. If any caliper showed a discrepancy of ≥0.5 mm at any of the screening points, the caliper underwent further analysis on 10 measurement points. Results Forty-one calipers were evaluated, of which 16 (39%) showed at least one point of ≥0.5 mm discrepancy on the caliper reading scale. Six calipers had errors >0.5 mm and two calipers had measurement errors of 1 mm in at least one point between 1-15-mm ruler measurement points. The majority of calipers (15/16) overestimated lengths. Conclusion Calipers are prone to damage with prolonged use that may affect their precision. Thus, calipers should be calibrated against a standard ruler prior to use even if they look grossly intact. Regular screening of calipers is recommended to identify any discrepancy and prevent avoidable complications.