Autorefraction as an Objective Method to Evaluate Accuracy of Intraocular Lens Calculation Formulas

Refractive outcomes of immediately sequential bilateral cataract surgery in eyes with long and short axial lengths

PURPOSE

To report the refractive outcomes of long (≥25.00 mm) and short (≤22.00 mm) axial length (AL) eyes undergoing immediately sequential bilateral cataract surgery (ISBCS).

METHODS

In this retrospective cohort study, patients who underwent ISBCS were identified and eyes of patients with bilateral long and short ALs were included. Pre- and postoperative biometry, autorefraction, and ocular comorbidities or complications were recorded. The primary outcome was the mean refractive prediction error.

RESULTS

Thirty-seven patients (74 eyes) with long ALs and 18 patients (36 eyes) with short ALs were included. The means ± standard deviations of the ALs were 26.40 ± 1.38 mm and 21.44 ± 0.46 mm in the long and short AL groups, respectively. In long AL eyes, the mean absolute error from the biometry-predicted refraction was - 0.16 ± 0.46 D, corresponding to 74% of eyes achieving a refraction within ±0.50 D of the predicted value. In short AL eyes, the mean absolute error was - 0.63 ± 0.73 D, corresponding to 44% of eyes achieving a refraction within ±0.50 D of the predicted value. Eight (44.4%) patients with short AL eyes had a myopic deviation greater than ±0.50 D from the predicted result in both eyes.

CONCLUSIONS

Compared to patients with long AL eyes, ISBCS in patients with short ALs had a wider variance in refractive outcome and a lower rate of achieving a postoperative refraction within ±0.50 D of the predicted target.

Comparison of toric intraocular lens calculation with the integrated K method and three single biometric devices

PURPOSE

To compare astigmatic outcomes using the Integrated K method and anterior surface keratometry from 3 different biometric devices.

SETTING

Lions Eye Institute, Perth, Australia.

DESIGN

Retrospective case series.

METHODS

Eyes of patients who underwent uneventful cataract surgery were analyzed. Predicted postoperative astigmatism was calculated for Integrated K method, IOLMaster 700, Lenstar and Pentacam. The mean centroid error in predicted postoperative refractive astigmatism (PE), mean absolute PE and percentage of eyes within 0.5 diopter (D), 0.75 D and 1 D of absolute magnitude of PE were compared. A subset analysis was done where the difference in cylinder magnitude between the 2 methods was more than 0.25 D. Spherical prediction outcomes were also analyzed.

RESULTS

241 eyes of 139 patients were included in the study. The mean centroid PE of Integrated K method (-0.07 @ 69) was significantly different from IOLMaster and Pentacam. The mean absolute PE with Integrated K method (0.33 ± 0.17) was significantly lower than all 3 devices. The percentage of eyes within 0.5 D and 0.75 D of absolute magnitude of PE was 82% and 99% for Integrated K method, 76% and 95% for IOLMaster and Lenstar, and 60% and 86% for Pentacam. In the subset analysis, the improvement in accuracy of the Integrated K method compared with a single device was greater in terms of the percentage of eyes predicted within 0.5 D. The Integrated K method did not impact the spherical prediction outcomes.

CONCLUSIONS

The integrated K method is more accurate and precise than anterior surface keratometry from a single biometric device.

Automated and subjective refraction with monofocal, multifocal, and EDOF intraocular lenses: review

Automated refraction (Scheiner principle) is universally used to start a visual examination. Although the results are reliable in eyes implanted with monofocal intraocular lenses (IOLs), they may be less precise with multifocal (mIOL) or extended depth-of-focus (EDOF) IOLs and can even indicate a refractive error that does not clinically exist. Autorefractor results with monofocal, multifocal, and EDOF IOLs were investigated through literature search analyzing the papers reporting the difference between automated and clinical refraction. The average difference ranged between -0.50 diopter (D) and -1.00 D with most mIOL and EDOF IOLs. The differences in astigmatism were generally much lower. Autorefractors using infrared light cannot measure eyes with high technology IOLs precisely because of the influence of the refractive or of the diffractive near add. The systematic error induced with some IOLs should be mentioned in the IOL label to prevent possible inappropriate refractive procedures to treat apparent myopia.