Interocular optical biometry differences as predictors of postoperative cataract surgery refractive outcomes: A retrospective cohort study

INTRODUCTION: Few studies have reported the impact of preoperative interocular discrepancy in optical biometry (axial length, corneal power, white-to-white, central corneal thickness) on postoperative refractive outcomes. This study aims to investigate any predictive value of preoperative optical biometry differences between eyes on postoperative refractive outcomes.

MATERIALS AND METHODS: A retrospective cohort study of patients who have undergone optical biometry measurement before unilateral phacoemulsification in the Queen Elizabeth Hospital, Sabah, Malaysia from 2018 to 2020. Biometry data of interest includes axial length (AL), keratometry(K), white-to-white (WTW) and central corneal thickness (CCT). The postoperative outcomes of interest were the patient's preoperative refractive target, postoperative best-corrected visual acuity (BCVA), postoperative refractive outcomes, and optical biometry prediction error.

RESULTS: The interocular biometry discrepancies which were associated with higher odds of prediction error >0.5D from the refractive target were Interocular Corneal Power Difference (IKD)-average≥0.8 D (Odds Ratio, OR=1.97; 95% Confidence Intervals, 95%CI: 1.06, 3.67) and Interocular WTW Difference ≥1.5 mm (OR=2.77; 95%CI: 1.11, 6.92). In cases with prediction error >1.0D, the measurements were Interocular AL Difference ≥0.4 mm (OR=2.99; 95%CI: 1.11, 8.06), IKD flat≥0.4D (OR=2.76; 95%CI: 1.31, 5.82) and Interocular CCT Difference ≥15μm (OR=3.53; 95%CI: 1.29, 9.64).

CONCLUSION: Interocular axial length difference ≥0.4mm and interocular central corneal thickness difference ≥15μm are associated with refractive error >1.0D from the pre-operative target. Interocular average corneal power difference ≥0.8D and interocular white-to-white difference ≥1.5mm have higher odds of refractive drift >0.5D from the refractive aim. The above cutoff values help clinicians to identify which patients have a higher risk of refractive shift post-cataract surgery and counsel the patient before cataract operation.