Intraoperative aberrometry-based aphakia refraction in patients with cataract: status and options

Prediction accuracy of intraoperative aberrometry compared with preoperative biometry formulae for intraocular lens power selection

OBJECTIVE

To compare the accuracy of intraoperative wavefront aberrometry to preoperative biometry formulae for predicting intraocular lens power.

DESIGN

Retrospective, consecutive case series.

PARTICIPANTS

Eyes undergoing cataract extraction with at least 1 month of follow-up after surgery at an ambulatory surgical centre in Toronto.

METHODS

Consecutive sample of 228 cataract extractions with monofocal, trifocal, or toric intraocular lens implantation from November 1, 2017, to December 31, 2019. The spherical equivalent was predicted preoperatively with Barrett Universal II, Hill-Radial Basis Function (RBF), SRK/T, Holladay I, Holladay II, Haigis, and HofferQ using biometry measurements and intraoperatively with wavefront aberrometry. The primary outcomes were mean prediction error and proportion of eyes with a spherical equivalent within 0.5 D of the refractive target at postoperative month 1.

RESULTS

The analysis included 159 eyes with 52% females and a mean age of 69.4 years. Formulae with the lowest mean prediction error were Hill-RBF (0.32 D ± 0.02 D), Barrett Universal II (0.32 D ± 0.02 D), intraoperative aberrometry (0.32 D ± 0.02 D), SRK/T (0.33 D ± 0.02 D), Holladay II (0.34 D ± 0.03 D), Holladay I (0.35 D ± 0.02 D), Haigis (0.37 D ± 0.02 D), and HofferQ (0.42 D ± 0.02 D). There were no statistically significant differences between intraoperative aberrometry and the preoperative formulae. Formulae with the highest proportion of eyes within 0.5 D of the refractive target were intraoperative aberrometry (82%), Barrett Universal II (81%), Hill-RBF (80%), SRK/T (77%), Holladay II (76%), Holladay I (75%), Haigis (71%), and HofferQ (70%).

CONCLUSIONS

Intraoperative aberrometry and modern preoperative biometry formulae are equally effective at reaching the refractive target. In normal eyes, intraoperative aberrometry does not appear to provide any additional benefit to modern prediction formulae.

Intraoperative aberrometry: an update on applications and outcomes

PURPOSE OF REVIEW

There is now a large body of experience with intraoperative aberrometry. This review aims to synthesize available data regarding intraoperative aberrometry applications and outcomes.

RECENT FINDINGS

The Optiwave Refractive Analysis (ORA) System utilizes Talbot-moiré interferometry and is the only commercially available intraoperative aberrometry device. There are few studies that include all-comers undergoing intraoperative aberrometry-assisted cataract surgery, as most studies examine routine patients only or atypical eyes only. In non-post-refractive cases, studies have consistently shown a small but statistically significant benefit in spherical equivalent refractive outcome for intraoperative aberrometry versus preoperative calculations. In studies examining axial length extremes, most studies have shown intraoperative aberrometry to perform similarly to preoperative calculations. Amongst post-refractive cases, post-myopic ablation cases appear to benefit the most from intraoperative aberrometry. For toric intraocular lenses (IOLs), intraoperative aberrometry may be used for refining IOL power (toricity and spherical equivalent) and alignment, and most studies show intraoperative aberrometry to achieve low postoperative residual astigmatism.

SUMMARY

Intraoperative aberrometry can be utilized as an adjunct to preoperative planning and surgeon's judgment to optimize cataract surgery refractive outcomes. Non-post-refractive cases, post-myopic ablation eyes, and toric intraocular lenses may have the greatest demonstrated benefit in intraoperative aberrometry studies to date, but other eyes may also benefit from intraoperative aberrometry use.

Intraoperative aberrometry compared to preoperative Barrett True-K formula for intraocular lens power selection in eyes with prior refractive surgery

To compare the predictive refractive accuracy of intraoperative aberrometry (ORA) to the preoperative Barrett True-K formula in the calculation of intraocular lens (IOL) power in eyes with prior refractive surgery undergoing cataract surgery at the Loma Linda University Eye Institute, Loma Linda, California, USA. We conducted a retrospective chart review of patients with a history of post-myopic or hyperopic LASIK/PRK who underwent uncomplicated cataract surgery between October 2016 and March 2020. Pre-operative measurements were performed utilizing the Barrett True-K formula. Intraoperative aberrometry (ORA) was used for aphakic refraction and IOL power calculation during surgery. Predictive refractive accuracy of the two methods was compared based on the difference between achieved and intended target spherical equivalent. A total of 97 eyes (69 patients) were included in the study. Of these, 81 eyes (83.5%) had previous myopic LASIK/PRK and 16 eyes (16.5%) had previous hyperopic LASIK/PRK. Median (MedAE)/mean (MAE) absolute prediction errors for preoperative as compared to intraoperative methods were 0.49 D/0.58 D compared to 0.42 D/0.51 D, respectively (P = 0.001/0.002). Over all, ORA led to a statistically significant lower median and mean absolute error compared to the Barrett True-K formula in post-refractive eyes. Percentage of eyes within ± 1.00 D of intended target refraction as predicted by the preoperative versus the intraoperative method was 82.3% and 89.6%, respectively (P = 0.04). Although ORA led to a statistically significant lower median absolute error compared to the Barrett True-K formula, the two methods are clinically comparable in predictive refractive accuracy in patients with prior refractive surgery.

Combined anterior segment OCT and wavefront-based autorefractor using a shared beam

We have combined an anterior segment (AS) optical coherence tomography (OCT) system and a wavefront-based aberrometer with an approach that senses ocular wavefront aberrations using the OCT beam. Temporal interlacing of the OCT and aberrometer channels allows for OCT images and refractive error measurements to be acquired continuously and in real-time. The system measures refractive error with accuracy and precision comparable to that of clinical autorefractors. The proposed approach provides a compact modular design that is suitable for integrating OCT and wavefront-based autorefraction within the optical head of the ophthalmic surgical microscope for guiding cataract surgery or table-top devices for simultaneous autorefraction and ocular biometry.

Repeatability of intraoperative Hartmann-Shack wavefront sensing in cataract surgery

PURPOSE

To evaluate the repeatability of aphakic intraoperative wavefront aberrometry and compare it with preoperative and postoperative aberrometry.

SETTING

Department of Ophthalmology, Hanusch Hospital, Vienna, Austria.

DESIGN

Prospective case series.

METHODS

Patients scheduled for cataract surgery were each measured 3 consecutive times using Hartmann-Shack wavefront sensing (HS-WFS) preoperatively, intraoperatively in aphakia, and 2 months postoperatively after intraocular lens implantation by a single examiner. Intraclass correlation coefficients (ICCs) of spherical equivalent (SE) values were evaluated for each timepoint. Intrasubject standard deviation (Sw) as repeatability (Sr) with corresponding repeatability limit () and mean SE differences with corresponding limits of agreement (LoA) were calculated for comparison.

RESULTS

A high consistency of repeated measurements was found with ICCs above 0.9 for each of the 3 timepoints. Intraobserver repeatability (Sr) and repeatability limit (r) of intraoperative aberrometry SE measurements (30 eyes of 30 patients) were 0.34 diopters (D) and 0.95 D, respectively. The LoA for intraoperative aphakic SE across 3 consecutive measurements were -0.71 to +0.85 D. For comparison, Sr and r for phakic preoperative measurements in the cataractous state (30 eyes of 30 patients) and postoperative measurements in the pseudophakic state (24 eyes of 24 patients) were 0.33 D and 0.93 D and 0.23 D and 0.64 D, respectively. Similarly, the LoA for preoperative and postoperative SE measurements were -0.66 to +0.60 D and -0.27 to +0.45 D, respectively.

CONCLUSIONS

HS-WFS test-retest reliability was high for all 3 timepoints, but the intraoperative setting resulted in a lower repeatability and broadened the agreement range.

Intraocular Lens Power Formulas, Biometry, and Intraoperative Aberrometry: A Review

The refractive outcome of cataract surgery is influenced by the choice of intraocular lens (IOL) power formula and the accuracy of the various devices used to measure the eye (including intraoperative aberrometry [IA]). This review aimed to cover the breadth of literature over the previous 10 years, focusing on 3 main questions: (1) What IOL power formulas currently are available and which is the most accurate? (2) What biometry devices are available, do the measurements they obtain differ from one another, and will this cause a clinically significant change in IOL power selection? and (3) Does IA improve refractive outcomes? A literature review was performed by searching the PubMed database for articles on each of these topics that identified 1313 articles, of which 166 were included in the review. For IOL power formulas, the Kane formula was the most accurate formula over the entire axial length (AL) spectrum and in both the short eye (AL, ≤22.0 mm) and long eye (AL, ≥26.0 mm) subgroups. Other formulas that performed well in the short-eye subgroup were the Olsen (4-factor), Haigis, and Hill-radial basis function (RBF) 1.0. In the long-eye group, the other formulas that performed well included the Barrett Universal II (BUII), Olsen (4-factor), or Holladay 1 with Wang-Koch adjustment. All biometry devices delivered highly reproducible measurements, and most comparative studies showed little difference in the average measures for all the biometric variables between devices. The differences seen resulted in minimal clinically significant effects on IOL power selection. The main difference found between devices was the ability to measure successfully through dense cataracts, with swept-source OCT-based machines performing better than partial coherence interferometry and optical low-coherence reflectometry devices. Intraoperative aberrometry generally improved outcomes for spherical and toric IOLs in eyes both with and without prior refractive surgery when the BUII and Hill-RBF, Barrett toric calculator, or Barrett True-K formulas were not used. When they were used, IA did not result in better outcomes.

Preoperative measurement vs intraoperative aberrometry for the selection of intraocular lens sphere power in normal eyes

Purpose

This study aimed to assess the value of intraoperative aberrometry (IA) in determining the intraocular lens (IOL) sphere power in eyes with no previous ocular surgery.

Patients and methods

We conducted a retrospective review of patients who underwent uncomplicated cataract surgery where standard preoperative (Preop) measurements and IA were performed. Calculated IOL sphere powers and postoperative refractions, both actual and theoretical, were compared based on the measurement method and lens type; lens types included multifocal, toric and aspheric single-vision non-toric IOLs.

Results

A total of 160 eyes of 112 patients were analyzed. The Preop lens power calculated was the same as the IA lens power 46% of the time, though this percentage was lower for multifocal IOLs. Across all lens types, there was a statistically significant bias (chi-square test, P<0.01) toward the IA method suggesting a lower powered lens. Actual postoperative refractive errors were not statistically significantly different when categorized by measurement method. Calculated errors by measurement method showed no statistically significant differences in expected outcomes. There were 63 cases where the Preop calculation and the intraoperative aberrometer calculation differed by 0.5 D. In 56% (35/63) of these cases, the IA result was a better option, and in 44% (28/63) of cases, the Preop calculation was better; this was not statistically significantly different from random expectation (50/50, P=0.53). In the three cases where calculated powers differed by 1.5 D, there appeared to be a positive effect of adjusting the Preop power toward the IA power.

Conclusion

The use of IA for the determination of sphere power in eyes with no previous ocular surgery does not appear to improve overall expected clinical outcomes, but it may be helpful in cases where the difference between IA and Preop calculations is high.

Emerging Technology in Refractive Cataract Surgery

Technology in cataract surgery is constantly evolving to meet the goals of both surgeons and patients. Recent major advances in refractive cataract surgery include innovations in preoperative and intraoperative diagnostics, femtosecond laser-assisted cataract surgery (FLACS), and a new generation of intraocular lenses (IOLs). This paper presents the latest technologies in each of these major categories and discusses how these contributions serve to improve cataract surgery outcomes in a safe, effective, and predictable manner.