Effect of Pupil Dilation on Ocular Biometric Measurements in High Myopes

Abstract

Purpose: To determine the effect of pupil dilation on different biometric measurements of eye in high myopes. Study Design: Descriptive observational study. Place and Duration of Study: The study was carried out eye out-patient department of Mayo Hospital, Lahore from August 2018 to December 2018. Methods: We recruited 72 (144 eyes) young, non-cataractous myopes of -6 diopters or more (mean spherical equivalent -7.41 ± 1.35) and age above 15 years (range 15 – 38 years). Sampling was based on non-probability convenient sampling whereas those with any ocular pathology and history of surgery were excluded. Biometric measurements were taken with non-contact biometer Len Star (LS900) with Haigis formula used for IOL power calculation, before and after pupil dilation Data was analyzed on SPSS (v25) and P < .001 was taken as significant. Results: Mean axial length (AL) difference between pre- and post-dilation was -0.006 ± 0.17 (p = 0.66), mean central corneal thickness (CCT) difference was -1.70 ± 8.95 (p = 0.024), mean anterior chamber depth (ACD) difference was -0.018 ± 0.04 (p = 0.001), mean lens thickness (LT) difference was 0.001 ± 0.53 (p = 0.81), mean Keratometry difference was 0.0013 ± 0.14 (p = 0.91), mean white to white (WTW) difference was 0.003 ± 0.01(p = 0.67) and mean IOL power difference was 0.000 ± 0.22 (p = 1.00). Bland Altman plots were drawn to indicate the 95% limits of agreement between pre- and post-dilation measurements. Conclusion: There was a statistically significant difference between pre and post dilation measurements of ACD but no clinically significant change was noted in IOL power calculations indicating that pupil dilation does not affect the biometric measurements. Key Words: Biometry, Len Star, Myopia, Axial length, Anterior chamber depth.