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Manual capsulorrhexis poorly correlates with refractive outcomes
Circularity and centration profiles had no significant impact on spherical equivalent refraction or corneal astigmatism at 1 month postop.
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CHICAGO — Manual capsulorrhexis profiles correlated poorly with refractive outcomes, according to a study presented here.
“In recent years, there’s been a growing shift in patients’ expectations following cataract surgery, from visual rehabilitation to, increasingly, expectations of refractive results,” Mali Okada, MBBS, said at the joint meeting of the American Academy of Ophthalmology and Asia-Pacific Academy of Ophthalmology. “The introduction of femtosecond laser technology in particular has prompted renewed scrutiny of the traditional methods of manual continuous curvilinear capsulorrhexis.”
The study is believed to be the first to explore the effect of manual capsulorrhexis parameters on refractive outcomes, Okada said.
Okada and colleagues analyzed a range of manual capsulorrhexis profiles in size, shape and centration and determined if the refractive result was influenced by the profiles. The primary outcome measures were postoperative spherical equivalent, refractive astigmatism and deviation from predicted refraction, Okada said.
Study design and methods
The prospective observational study included 113 eyes of 108 patients who underwent conventional cataract surgery. A sample of at least 100 patients was needed to generate sufficiently powered results, Okada said.
Slit lamp anterior segment photography was performed 4 weeks after surgery.
Computer software was used to generate circularity and decentration indices. A score of 1 denoted a theoretically perfect circle, Okada said.
Keratometry was used to measure preoperative astigmatism, and the SRKT formula was used to generate lens power calculations.
Fifty percent of patients had preoperative corneal astigmatism of less than 0.75 D, Okada said.
Outcomes and associations
Study results showed that mean postoperative visual acuity was 20/27.7; 90% of eyes attained visual acuity of 20/40 or better. All but one patient had best corrected visual acuity of 20/30 or better.
After surgery, 70% of patients had refraction within 0.5 D of the targeted value; 91% were within 1 D. Mean postop spherical equivalent refraction was 0.5 D.
Data showed that the mean circularity index of the capsulorrhexis was 0.83 mm and mean decentration was 0.25 mm. No capsulorrhexis was decentered by more than 0.71 mm. Mean capsulorrhexis diameter was 4.41 mm.
Results showed an incomplete 360° capsular agreement with optic overlap in 12% of patients. Correlations between circularity, decentration and deviation from targeted spherical equivalent refraction were statistically insignificant, Okada said.
“Overall, there was no correlation between capsulorrhexis parameters with any of the refractive outcome measures,” she said.
Quartile analysis showed no significant differences between the most and least circular capsulorrhexes or between the most and least centered capsulorrhexes.
Additionally, a subanalysis of the 56 patients with baseline corneal astigmatism of less than 0.75 D showed no association between non-circularity or decentration and postoperative astigmatism.
The study had some limitations in terms of parameters and design, Okada said.
“We recognize that there are limitations to our study,” she said. “Some factors related to capsulorrhexis and refractive outcomes, for example, capsule elasticity and zonule integrity, are difficult to quantify, and we did not measure the lens position. There was also a relatively short follow-up period, merely 4 weeks.” – by Matt Hasson