Intraoperative Biometry Versus Conventional Methods in Toric IOL Implantation
Purpose
To compare intraoperative biometry (IRB) to conventional methods for intraocular lens (IOL) power calculation in patients receiving toric lenses.
Methods
This series compared two separate cohorts of patients undergoing primary cataract extraction and toric IOL implantation. In 52 patients, ORA was used to guide IOL power determination with real-time axis adjustment. A second cohort of 52 patients was only assessed using conventional methods of IOL power and axis (i.e. Holladay 1/2, Haigis, and SRK-T, Alcon Toric calculator and HicSoapro software). Prediction error was calculated (mean absolute error = actual spherical equivalent (SE) – predicted SE). The percentage of eyes within ± 0.50 diopters (D) and ± 1.00 D of the refractive target was calculated in each group. Residual cylinder and deviation from the intended axis were also compared.
Results
Patients in the ORA cohort achieved statistically significant better postoperative results than those in the conventional subgroup (MAE 0.34±0.29 (conventional) vs 0.25±0.22 (ORA), p=0.05) (Table 1). Patients undergoing IRB also were more likely to be within 0.5D of the targeted refraction (87% vs 79%) (Table 2). With the help of IRB, surgeons were able to reduce astigmatism to less than 1D in 87% of patients compared to only 69% of patients who only underwent conventional planning. In the ORA group, 29% fell within 10 degrees of the intended axis compared to 12% of the conventional group.
Conclusion
In a previous study by the same group, the power estimation in eyes undergoing toric IOLs was more accurately predicted by ORA than conventional methods. However this was biased because all Toric IOLs were adjusted intraoperatively based on the ORA guidance. The current study shows that ORA improves upon surgical planning in toric patients.