Astigmatism Prediction Error Of Two Oct Biometry Devices And Two Calculation Methods

This was a retrospective study of successful cataract surgery or refractive lens exchange. Preoperative biometry was performed with two different biometers: One SS-OCT biometer (Anterion, Heidelberg Engineering) and one combined reflection and SS-OCT biometer, (Eyestar 900, Haag-Streit). Calculations were performed with both devices using the built-in Barrett Toric calculator using both predicted (PPA) and measured posterior corneal astigmatism (MPA). The astigmatism prediction error (APE) was calculated as the magnitude of the vector differences between the achieved and the predicted refractive astigmatism. For patients with toric IOLs, the predicted astigmatism was recalculated using the actual postoperative toric alignments.

The study included 95 eyes of 95 patients. The mean age was 61 years and 41% were female. Toric IOL´s were implanted in 40% of the eyes. Mean Follow-up time was 92 days (62 - 140). The mean uncorrected VA was -0,02 on the logMAR scale. The mean postoperative refractive spherical equivalent and astigmatism was 0.07 and -0,32, respectively. The mean APE varied from 0,35 to 0.36 for both calculations and both devices. The percentages of eyes with APE within 0.5 D was 81 and 82 for PPA and MPA, respectively with the Eyestar 900, and 77 and 79  for PPA and MPA, respectively with the Anterion. No statistically significant differences of means (p<0,4) or percentages of eyes within 0.5, 0.75 or 1 D of APE (p<0,1) were observed Conclusions