The Importance of ACD, LT, and WTW in Predicting Postoperative Refraction Using the Barrett Universal II, Kane, and Hill-RBF 3.0 Formulas.

Purpose: To evaluate the importance of the anterior chamber depth (ACD), lens thickness (LT), and white-to-white distance (WTW) in predicting the final postoperative refraction using modern formulas.

Methods: This was a retrospective study of 140 consecutive eyes that underwent cataract surgery at the Department of Ophthalmology, Edith Wolfson Medical Centre, Holon, Israel. The Barrett Universal II (BUII), Kane, and Hill-RBF 3.0 formulas were calculated for each eye with all combinations of omitting ACD, LT, and WTW, as possible by each formula. Lens constant optimizations were executed. The results were compared to the postoperative refraction.

Results: For the BUII formula, the ACD only variation exhibited a statistically significant increase in mean absolute deviation (MAD) (0.024 diopters [D], P = .010) and standard deviation of prediction error (SD-PE) (0.022, P = .002) compared with BUII using all parameters, whereas no other variations showed statistically significant differences in MAD or SD-PE. For the Hill-RBF 3.0 formula, both the ACD only (0.012 D, P < .001) and ACD+WTW (0.009 D, P = .016) variations demonstrated a statistically significant increase in MAD, although no statistically significant differences were observed in SD-PE. For the Kane formula, excluding the LT parameter resulted in a statistically significant increase in MAD (0.020 D, P = .034), whereas the increase in SD-PE (0.020, P = .266) was not statistically significant.

Conclusions: The BUII, Kane, and Hill-RBF 3.0 formulas demonstrated statistically significant, but not clinically meaningful, differences in SD-PE and MAD when ACD, LT, and WTW were excluded in normal biometric eyes. Further research involving eyes with atypical biometric characteristics is warranted to enhance refractive accuracy and minimize outliers. [J Refract Surg. 2025;41(7):e662-e666.].