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Statistical model predicts myopic regression risk for LASIK flap creation methods
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LASIK flap creation with a femtosecond laser posed a lower risk of myopic regression than flaps created with a mechanical microkeratome, according to a study.
“Information obtained from the predictive model enables clinicians to identify which patient has a higher risk for myopia regression and to more precisely estimate the probability within the follow-up time frame,” the study authors said.
The retrospective, comparative study included 377 patients with a mean age of 29.89 years who underwent bilateral LASIK with a mechanical microkeratome; 409 patients with a mean age of 32.35 years underwent bilateral LASIK with a femtosecond laser.
Flaps were created with a Moria M2 mechanical microkeratome or IntraLase femtosecond (Abbott Medical Optics) laser. Ablation was performed with a Star S4 excimer laser (Visx).
Investigators used a Cox proportional hazards model to evaluate the influence of flap creation methods and other factors on the risk of postoperative myopic regression.
Study results showed insignificant between-group differences in mean spherical equivalent 1 week postoperatively. However, at 12 months, myopic regression was significantly greater in the microkeratome group (P = .0058).
Data adjusted for other contributing factors showed that the cumulative risk for myopic regression was significantly higher with a mechanical microkeratome than with a femtosecond laser (P = .0002).
Based on a definition of myopic regression as a myopic shift of 0.5 D or more and residual myopia of 0.5 D or less, the mechanical microkeratome group had a 66.9% risk of regression and the femtosecond laser group had a 43.6% risk at 12 months, the authors said.
Perspective
Back to TopJason P. Brinton, MD
This study illustrates the utility of multivariate analysis and highlights the value of the femtosecond laser in achieving improved refractive stability following LASIK. In an era when clinical recommendations are often made based on small data sets, this study involves 786 eyes.
The data reaffirm that both microkeratome and femtosecond laser technologies lead to good results in terms of visual acuity and refractive stability. The usual suspects — thinner corneas and larger dioptric corrections — increase the likelihood that an enhancement procedure will need to be performed and make lenticular refractive approaches look more favorable, particularly in highly myopic eyes, when options are weighed in the balance.
In our practice, we have used the femtosecond laser for 100% of our LASIK procedures for 10 years. With improvements in laser technology since this study was conducted, newer-generation lasers have brought an even greater level of visual outcomes, faster visual recovery and refractive stability associated with predictable, customizable, high-quality planar flaps.
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J Cataract Refract Surg. 2012;38(6):992-999.
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