Why preoperative acuity predicts postoperative acuity in wavefront-guided LASIK

Area of Science:

• Ophthalmology
• Refractive Surgery
• Visual Optics

Background:

• Custom laser in situ keratomileusis (LASIK) is a refractive surgical procedure.
• Clinical observation suggests patients with better-than-average preoperative visual acuity may risk losing acuity post-LASIK.
• This study investigates the validity of this clinical wisdom.

Purpose of the Study:

• To critically evaluate the clinical notion that better-than-average preoperative best-corrected visual acuity (BCVA) increases the risk of BCVA loss after custom LASIK.
• To differentiate between surgical outcomes and statistical phenomena in refractive surgery results.

Main Methods:

• Measured high-contrast BCVA before and 3 months after custom LASIK in 79 eyes.
• Divided subjects into groups with better-than-average and average-to-worse preoperative BCVA.
• Controlled for retinal magnification and regression to the mean.

Main Results:

• Custom LASIK resulted in a statistically significant average gain in visual acuity.
• After correcting for statistical effects, both groups showed similar small gains in visual acuity.
• The perceived acuity loss in better-than-average pre-LASIK eyes was primarily attributed to regression to the mean.

Conclusions:

• Custom LASIK provides a statistically significant improvement in visual acuity.
• The tendency for eyes with better preoperative acuity to remain stable or lose acuity post-surgery is largely a statistical artifact (regression to the mean).
• This phenomenon is not attributable to the surgical procedure itself when accounting for statistical variations.