ASCRS News: ASCRS/EyeWorld Journal Club
December 2021
by Thomas Meirick, MD, and Parisa Taravati, MD
Cataract surgery is one of the most commonly performed surgeries in the U.S. and around the world. As such, researchers and innovators have provided an ever-increasing number of technological advancements such as new surgical instruments and intraocular lenses. In addition, large, retrospective database studies have allowed cataract surgeons to predict the outcomes of their procedures more accurately.1 However, some debate has remained in the literature regarding astigmatism management in postoperative pseudophakic patients.2–4 Namely, there is no consensus on what amount of astigmatism is visually significant for patients after cataract surgery.2–4 In this retrospective database study, Schallhorn et al. analyzed both visual acuity and subjective postoperative survey results, stratified by the amount of residual astigmatism, to determine the effect of residual astigmatism on postoperative outcomes.
Design and methods
Residency Program Director
Department of Ophthalmology
University of Washington
Seattle, Washington
The authors utilized a retrospective database from Optical Express, a private practice in the U.K. All patients who underwent cataract or refractive lens exchange between July 2014 and June 2019 and attended their 3-month postoperative visit with full refraction were included. Patients with any prior ocular surgery were excluded from the study. Because a large percentage of patients targeted monovision or mini-monovision, only dominant eyes (target emmetropia) were enrolled in the study.
The authors extracted demographic data, preoperative and postoperative corrected distance visual acuity, uncorrected distance and near visual acuity, final refraction, intraocular lens data, and patient subjective postoperative questionnaire data. The question used from the postoperative survey was, “Thinking about your vision during the last week, how satisfied are you with your vision (without the use of spectacles or contact lenses)?” The response was scored on a 5-point scale with 1 being very satisfied and 5 being very dissatisfied.
Surgeries were completed by 24 surgeons in 17 sites; all surgeries were completed with assistance of a femtosecond laser. No formal treatment guideline was followed, but astigmatism was typically managed with the following algorithm. Patients with between 0–0.75 D of astigmatism were managed by placing the clear corneal incision at the steepest meridian; patients with 0.75–1.50 D of astigmatism were typically corrected with femto laser astigmatic keratotomy. Patients with more than 1.50 D of astigmatism were considered for a toric intraocular lens.
Ophthalmology Resident
University of Washington
Seattle, Washington
The authors utilized multivariate regression to analyze the association of residual astigmatism with both uncorrected distance visual acuity (UDVA) and patient satisfaction. They used correlation analysis to identity other potential contributing variables to be included in the multivariate analysis. Patients with multifocal IOLs and patients with monofocal IOLs were analyzed separately. The authors do not mention whether p-values were corrected for multiple comparators.
Results
In this cohort, the mean patient age was 58.99 years. A large majority (71.7%) of patients received a multifocal non-toric lens. Monofocal non-toric (18.4%) was the second most common lens type, followed by multifocal toric (5.8%) and monofocal toric (4.1%). Among patients who received a multifocal lens (13,267 eyes), residual astigmatism of 0.25–0.50 D increased the odds of not achieving 20/20 UDVA, with an odds ratio (OR) of 1.7 and p-value of <0.0001. However, the same amount of residual astigmatism was not associated with decreased odds of “not being satisfied” (defined as a score of 3 or higher on the survey), OR 1.1, p-value 0.1911. If the amount of residual astigmatism rose to 0.75–1.00 D, the odds ratio of not achieving 20/20 UDVA increased to 6.5 (p-value <0.0001), while the odds ratio of “not being satisfied” increased to 1.5 and gained statistical significance (<0.0001). The trend continued with higher levels of residual astigmatism, and there were nearly identical results within the monofocal IOL cohort.
The authors also analyzed the association of residual hyperopic and myopic sphere with UDVA and patient satisfaction. Among patients with multifocal IOLs, residual hyperopic sphere of 0.25–0.50 D was tolerated without an increase in OR of not achieving 20/20 vision (OR 1.1, p-value 0.0647) or of “not being satisfied” (OR 0.9, p-value 0.4308). The same amount of residual postoperative myopic sphere (0.25–0.50 D) was associated with an OR of 5.0 (p-value <0.0001) of not achieving 20/20 UDVA, and an OR of 1.4 (p-value of 0.0012) of “not being satisfied.” This trend remained valid at higher levels of postoperative sphere; for a given diopter, patients with myopic sphere had higher odds ratios of not achieving 20/20 UDVA and “not being satisfied.” As with astigmatism, there were nearly identical results within the monofocal IOL cohort.
Axis of astigmatism was analyzed to determine if it was an independent predictor of UDVA; however, in a multivariate analysis, axis of astigmatism did not independently predict UDVA.
During the ASCRS Journal Club discussion of this study, the panelists discussed the importance of “raising the bar” with regard to astigmatism management.
Discussion
The authors’ data led to several important conclusions. First, patients were less likely to be “satisfied” with their refractive outcomes and less likely to achieve 20/20 UDVA if their residual astigmatism was greater than 0.50 D. Second, for a given level of postoperative residual sphere, patients who were hyperopic were more likely to be satisfied with their vision and more likely to achieve 20/20 UDVA than patients who were myopic. Third, axis of astigmatism did not independently predict UDVA; with-the-rule, against-the-rule, and oblique astigmatism of the same magnitude resulted in the same UDVA.
During the ASCRS Journal Club discussion of this study, the panelists discussed the importance of “raising the bar” with regard to astigmatism management. This study suggested that there is a need to improve our preoperative measurements, lens calculations, and intraoperative management options to optimize patient outcomes. Prior literature has been somewhat mixed, with some authors suggesting up to 1.0 D of astigmatism can be observed with good visual acuity outcomes,2 while others suggest treating anything more than 0.50 D.2,3 The results presented here suggest any amount of astigmatism decreases the odds of achieving 20/20 UDVA, however, only residual astigmatism more than 0.50 D was associated with less patient satisfaction.
The panelists also discussed their surprise at the results suggesting that patients with hyperopic refractive misses were more satisfied and more likely to achieve 20/20 UDVA than their myopic counterparts. While the traditional teaching is to leave patients slightly myopic, these data would suggest just the opposite. While the effects of multifocal lenses could explain some of the patient satisfaction with residual hyperopia, the same results were noted in the monofocal cohort. A previous study suggested that even slight hyperopic refractive misses degrade visual outcomes in patients with trifocal lenses,5 however, this study used extraocular lenses to simulate a refractive surprise.
Additional analyses would have been valuable in this study. For instance, stratifying patients based on preoperative refractive error as a predictor of level of satisfaction postoperatively would have been advantageous. Would previously myopic patients have the same level of satisfaction with a hyperopic refractive outcome compared to other subgroups? Secondly, though the axis of astigmatism did not affect the UDVA, it would have been beneficial to determine if the axis played a role in the level of patient satisfaction postoperatively. Do patients with the same level of with-the-rule astigmatism have a higher level of satisfaction than patients with against-the-rule or oblique astigmatism?
This study is limited by its retrospective nature and lack of a standardized treatment protocol for different levels of astigmatism. In addition, subjective assessments of vision likely vary between different populations, limiting the external validity of those results. Finally, only dominant eyes were included in the study, but the patient questionnaire was completed after both eyes underwent surgery. It is therefore difficult to exclude the binocular impact of monovision on the level of patient satisfaction postoperatively.
Conclusions
In this large, retrospective database study, Schallhorn et al. suggested residual astigmatism of more than 0.50 D in pseudophakic patients is associated with less patient satisfaction and decreased visual acuity. These associations become larger and more significant with each 0.25 D of residual astigmatism. In addition, patients with hyperopic refractive misses of a given magnitude were more likely to be satisfied with their vision and to achieve 20/20 uncorrected distance visual acuity than those with equivalent myopic refractive misses.
Effect of residual astigmatism on uncorrected visual acuity and patient satisfaction in pseudophakic patients
Steven Schallhorn, MD, Keith Hettinger, MS, Martina Pelouskova, MSc, David Teenan, MD, Jan Venter, MD, Stephen Hannan, OD, Julie Schallhorn, MD
J Cataract Refract Surg. 2021;47(8):991–998.
- Purpose: To evaluate the effect of residual astigmatism on postoperative visual acuity and satisfaction after intraocular lens surgery.
- Setting: Private practice, U.K.
- Design: Retrospective case series
- Methods: Postoperative data of patients who had previously undergone refractive lens exchange/cataract surgery were used in a multivariate regression model to assess the effect of residual astigmatism on 3 months postoperative monocular UDVA and patient satisfaction. The analysis was based on residual refraction in the dominant eye of each patient (17,152 eyes). Odds ratios were calculated to demonstrate the effect of increasing residual astigmatism on UDVA and satisfaction with separate calculations for monofocal and multifocal IOLs.
- Results: Compared to eyes with 0.0 D residual astigmatism, the odds of not achieving 20/20 vision in eyes with 0.25–0.50 D residual astigmatism increased by a factor of 1.7 and 1.9 (p<0.0001) in monofocal and multifocal IOLs, respectively. For the residual astigmatism 0.75–1.00 D, the odds ratio for not achieving 20/20 vision compared to eyes with no astigmatism was 6.1 for monofocal and 6.5 for multifocal IOLs (p<0.0001). The effect of residual astigmatism on satisfaction was more evident at the 0.75–1.00 D level, where the odds of not being satisfied with vision increased by a factor of 2.0 and 1.5 in patients with monofocal and multifocal IOLs, respectively (p<0.0001). The orientation of astigmatism was not a significant predictor in multivariate analysis.
- Conclusions: Multivariate analysis in a large population of patients demonstrated that low levels of residual astigmatism can degrade visual acuity. Corneal astigmatism of ≥0.50 D should be included in surgical planning.
article sidebar
The ASCRS Journal Club is a virtual, complimentary CME offering exclusive to ASCRS members that brings the experience of a lively discussion of two current articles from the Journal of Cataract & Refractive Surgery to the viewer. Co-moderated by Nick Mamalis, MD, and Leela Raju, MD, the August session was recorded live during the 2021 ASCRS Annual Meeting in Las Vegas, Nevada, and featured a presentation by William Wiley, MD, author of “Comparative study of phacoemulsification parameters with and without nitinol filament nuclear disassembly.” The second manuscript, “Effect of residual astigmatism on uncorrected visual acuity and patient satisfaction in pseudophakic patients,” was presented by Thomas Meirick, MD, ophthalmology resident, University of Washington. To view the August Journal Club session, go to ascrs.org/clinical-education/journal-club/schedule/august-2021.
References
- Melles RB, et al. Accuracy of intraocular lens calculation formulas. Ophthalmology. 2018;125:169–178.
- Hayashi K, et al. Influence of astigmatism on multifocal and monofocal intraocular lenses. Am J Ophthalmol. 2000;130:477–482.
- Villegas EA, et al. Minimum amount of astigmatism that should be corrected. J Cataract Refract Surg. 2014;40:13–19.
- Sigireddi RR, Weikert MP. How much astigmatism to treat in cataract surgery. Curr Opin Ophthalmol. 2020;31:10–14.
- Hayashi K, et al. Effect of spherical equivalent error on visual acuity at various distances in eyes with a trifocal intraocular lens. J Refract Surg. 2019;35:274–279.
Contact
Meirick: tmeirick@uw.edu
Taravati: taravati@uw.edu
