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Intraoperative aberrometry reduces residual refractive astigmatism
Patients were 2.4 times more likely to have less than 0.5 D of residual refractive astigmatism with aberrometry than with standard methods.
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Cataract surgery and toric IOL implantation yielded significantly less residual refractive astigmatism with intraoperative aberrometry than with standard methods, according to a study.
In addition, preoperative keratometric cylinder was reduced, as measured by residual postoperative refractive cylinder, 57% and 75% of the time with the non-aberrometry and aberrometry groups, respectively.
“What we found was that the use of aberrometry improved our residual refractive astigmatism results,” Kathryn M. Hatch, MD, the corresponding author, told Ocular Surgery News. “Our residual refractive astigmatism results were better with use of intraoperative aberrometry than without. … We were finding that, basically, you don’t always get it right with standard biometry and standard calculations. So, using aberrometry improved our results.”
Kathryn M. Hatch
Methods and measures
The retrospective, non-randomized comparative trial, published in the Journal of Refractive Surgery, included 37 eyes that underwent cataract extraction and toric IOL implantation. Toric IOL power and alignment were determined preoperatively with automated keratometry, standard optical biometry and an online calculator, and refined using intraoperative aberrometry (ORA, Alcon).
A control group of 27 eyes underwent toric IOL selection, with automated keratometry, standard optical biometry and an online calculator, and positioning without intraoperative aberrometry.
Hatch said that ORA was used to rotate toric lenses into position and change the spherical power and toric power.
Spherical and toric IOL power were changed 35% and 24% of the time, respectively, guided by the ORA.
When evaluating the number of rotations made guided by ORA, two-thirds of cases required no additional rotations, while 92% of eyes required less than or equal to three rotations. Only 8% of eyes required more than three rotations.
The lens was rotated three times or less in 92% of patients in the aberrometry group.
The primary outcome measure was mean postoperative residual refractive astigmatism (RRA). Secondary metrics included manifest cylinder refraction, reduction in astigmatism and uncorrected distance visual acuity.
Mean follow-up was 58 days in the aberrometry group and 60 days in the non-aberrometry group.
Mean preoperative keratometric astigmatism was 1.83 D in the aberrometry group and 1.59 D in the non-aberrometry group.
Results and observations
After surgery, mean RRA was 0.46 D in the aberrometry group and 0.68 D in the non-aberrometry group. The between-group difference was statistically significant (P = .0153).
Reduction in cylinder between preoperative keratometric astigmatism and postoperative RRA was 75% in the intraoperative aberrometry group and 57% in the toric calculator group (P = .0027).
Intraoperative aberrometry also delivered better results compared with the toric calculator in manifest cylinder reduction (P = .0330) and percent change in manifest cylinder (P = .0023).
In the aberrometry group, RRA was 0.25 D or less in 38% of patients, 0.5 D or less in 78%, 0.75 D or less in 86% and 1 D or less in 95%. In the non-aberrometry group, RRA was 0.25 D or less in 22% of patients, 0.5 D or less in 33%, 0.75 D or less in 74% and 1 D or less in 89%.
“Patients were [2.4 times] more likely to have less than 0.5 D of residual refractive astigmatism with the use of the aberrometry,” Hatch said.
Mean uncorrected distance logMAR visual acuity was 0.16 (range: –0.12 to 0.4) in the toric calculator group and 0.11 (range: –0.12 to 0.7) in the intraoperative aberrometry group.
Uncorrected distance visual acuity was 20/20 or better in 48% of eyes in the aberrometry group and 26% of eyes in the non-aberrometry group.
“I think there is a significant role [for ORA]. Now I’m using it for all my toric IOLs because I think that it adds a benefit,” Hatch said. “Disadvantages to the technology include cost and time. Given our results, I believe it’s worth the extra time.”
ORA is also useful in determining IOL placement and power in patients with previous refractive surgery and takes posterior corneal astigmatism into account, Hatch said.
“If you aren’t taking the posterior cornea into consideration, you are relying on averages and odds. For this reason, you may not get accurate results as not all individuals have an overall against-the-rule contribution,” she said. “That’s why I think the ORA really is important if you’re trying to nail the astigmatism correction. ORA gives you aberrometry of the whole eye.” – by Matt Hasson
Reference:
Hatch KM, et al. J Refract Surg. 2015;doi:10.3928/1081597X-20150319-03.For more information:
Kathryn M. Hatch, MD, can be reached at Massachusetts Eye and Ear Infirmary, 1601 Trapelo Road, Suite 184, Waltham, MA 02451; email: kathryn_hatch@meei.harvard.edu.Disclosure: Hatch reports no relevant financial disclosures.
Perspective
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Mark Packer, MD, FACS, CPI
Hatch and colleagues demonstrate the superiority of supplementary intraoperative aberrometry in the correction of pre-existing corneal astigmatism with toric IOL implantation compared with the standard use of an online toric IOL calculator alone. The only surprising feature of their article is the relatively poor showing of the toric calculator vis-à-vis earlier published studies. In fact, data from Alcon’s contralateral eye study demonstrated 77% of eyes achieved 0.5 D or less of residual refractive astigmatism with the toric calculator, while Hatch found only 33% of eyes achieved 0.5 D or less of residual refractive astigmatism with the toric calculator. Apparently, results can vary depending on multiple factors, including patient selection, diagnostic accuracy and surgical technique.Click Here to Manage Email Alerts