Toric Intraocular Lens Calculation Considering Anterior Surgically Induced Astigmatism and Posterior Corneal Astigmatism.

PURPOSE: To evaluate the prediction error (PE) after applying the Abulafia-Koch formula in an online calculator with and without consideration of anterior corneal surgically induced astigmatism (SIACornea). METHODS: SIACornea models were calculated with a historical database of 204 right eyes (REs) from a single surgeon, either for manual (2.2 mm) or femtosecond (2.5 mm) temporal clear corneal incisions. PE was assessed in 58 REs operated by the same surgeon with a monofocal toric IOL and calculated, considering the PCA estimation in an online calculator with the combination of each one of the following SIACornea calculation approaches: (A) considering only significant centroids after stratification, (B) all centroids after stratification and (C) a single centroid without stratification. RESULTS: The consideration of all centroids resulted in an underestimation of SIACornea in cases of preoperative against-the-rule astigmatism (ATR-A) and an overestimation in with-the-rule astigmatism (WTR-A). After stratification, SIACornea was only significant in preoperative ATR and oblique astigmatism cases for femtosecond incisions. PE considering PCA only was 0.03@160º. The combination with SIACornea resulted in a WTR-A surprise in preoperative ATR-A and WTR-A, however only being significant for preoperative ATR-A in calculation approaches B (0.29@84º) and C (0.21@80º). SIACornea addition to PCA estimation only reduced the centroid for oblique preoperative astigmatism. CONCLUSIONS: Surgeons should consider the calculation of the SIACornea after stratification by astigmatism type when using the same incision location (i.e. temporal). However, SIACornea derived from the anterior corneal surface should not be combined with PCA estimation for IOL power calculations.

Confounding sizing in posterior chamber phakic lens selection due to white-to-white measurement bias.

PURPOSE: To assess the agreement in the white-to-white (WTW) measurement with two different devices, the reproducibility and the probability of confusing sizing (PCS) in selecting a different implantable collamer lens (ICL). STUDY DESIGN: Retrospective observational case series. METHODS: Images of 192 eyes were captured with both devices. The WTW was measured automatically (OA) and manually (OM) with the Orbscan and Keratograph (KA and KM) by one examiner who repeated a total of four measures. A second examiner conducted a single manual measure for each device over the same image. The ICL sizing was computed for each measure of WTW and the PCS was calculated as the percentage of cases for which the confronted or repeated measure resulted in a different size of the ICL. The critical WTWs with highest PCS were identified. RESULTS: KM overestimated the WTW versus OM in 0.13 ± 0.18 mm (P < 0.001) but not in the automated method comparison, 0.01 ± 0.19 mm (P = 0.58). Inter-examiner reproducibility (R) was higher with OM than with KM, and the intra-examiner R decreased with the average of two measures in both cases. The PCS was higher with the increase of mean differences, the limits of agreement (LoAs), and R. WTWs from 11.1 to 11.2 mm, 11.6 to 11.7 mm, and 12.3 to 12.4 mm resulted in higher PCS. CONCLUSION: The mean difference is not enough to apply conversions between devices and the LoAs and R should be considered. Special attention should be taken for WTWs with higher PCS.