Optical Quality and Visual Performance after Relex SMILE, LASIK or PRK Refractive Surgery Procedures for Myopia

Abstract

Purpose : To compare the optical quality [sphero-cylindrical refraction and higher-order wavefront aberrations (HOA’s)] and visual performance (uncorrected high- and low-contrast logMAR acuity and random dot stereoacuity) following three routine refractive surgery procedures – Relex SMILE, LASIK or Photorefractive Keratectomy (PRK) – performed bilaterally for the correction of myopia.

Methods : 106 subjects with myopia (and astigmatism ≤1.5D) underwent either Relex SMILE (n=40), femtosecond LASIK (n=40) or PRK (n=26) refractive surgery procedures on the Technolas 217z® excimer laser platform (for LASIK and PRK) or on the Visumax® femtosecond laser system (for SMILE). All outcome variables were measured in both eyes (only right eye data reported here; stereoacuity was binocular) pre-operatively and 1 week, 1 month, 3 months and 6 months post-operatively.

Results : Median (25^th to 75^th IQR) spherical equivalent of refraction decreased from pre-operative myopia [SMILE: −5.5D (−6.5 to −4.3D); LASIK: −6.4D (−8.0 to −4.2D); PRK: −4.3D (−5.0 to −3.5D)] to within ±0.5D of emmetropia in all groups upto 6 months after surgery (p<0.001). RMS deviation of HOA’s (HORMS) increased after PRK [6mths: 0.68µ (0.57 to 0.77µ)], LASIK [6mths: 0.59µ (0.54 to 0.71µ)] and SMILE [6mths: 0.28µ (0.24 to 0.32µ)] at all times after surgery, relative to pre-operative values [0.22 to 0.26µ for all] (p<0.001). Uncorrected high-contrast and low-contrast logMAR acuities were all within ±0.1 and ±0.2 logMAR units, respectively, of each other before and at all times after surgery (p≥0.01 for all). Stereoacuity improved after SMILE [6mths: 20arc sec (15 to 27.5arc sec)] while it worsened after LASIK [6mths: 73arc sec (51.2 to 79.5arc sec)] and PRK [6mths: 73arc sec (60 to 80arc sec)] at all times after surgery, relative to pre-operative values [36 to 41arc sec] (p<0.001). The inter-ocular average and difference in HORMS were well correlated with post-operative stereoacuity in all groups (r≥0.6 for both).

Conclusions : SMILE, LASIK and PRK refractive surgeries correct myopia with similar accuracy and result in comparable values of uncorrected high- and low-contrast logMAR acuity. Stereoacuity is better following SMILE than LASIK and PRK surgeries and this appears to be correlated with magnitude of HOA’s induced post-operatively.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.