title: Induced Higher-order aberrations after Laser In Situ Keratomileusis (LASIK) Performed with Wavefront-Guided IntraLase Femtosecond Laser in moderate to high Astigmatism.
abstract: BACKGROUND
  Wavefront-guided Laser-assisted in situ keratomileusis (LASIK) is a widespread and effective surgical treatment for myopia and astigmatic correction but whether it induces higher-order aberrations remains controversial. The study was designed to evaluate the changes in higher-order aberrations after wavefront-guided ablation with IntraLase femtosecond laser in moderate to high astigmatism.
  
  
  METHODS
  Twenty-three eyes of 15 patients with moderate to high astigmatism (mean cylinder, -3.22 ± 0.59 dioptres) aged between 19 and 35 years (mean age, 25.6 ± 4.9 years) were included in this prospective study. Subjects with cylinder ≥ 1.5 and ≤2.75 D were classified as moderate astigmatism while high astigmatism was ≥3.00 D. All patients underwent a femtosecond laser-enabled (150-kHz IntraLase iFS; Abbott Medical Optics Inc) wavefront-guided ablation. Uncorrected (UDVA), corrected (CDVA) distance visual acuity in logMAR, keratometry, central corneal thickness (CCT) and higher-order aberrations (HOAs) over a 6 mm pupil, were assessed before and 6 months, postoperatively. The relationship between postoperative change in HOA and preoperative mean spherical equivalent refraction, mean astigmatism, and postoperative CCT were tested.
  
  
  RESULTS
  At the last follow-up, the mean UDVA was increased (P < 0.0001) but CDVA remained unchanged (P = 0.48) and no eyes lost ≥2 lines of CDVA. Mean spherical equivalent refraction was reduced (P < 0.0001) and was within ±0.50 D range in 61% of eyes. The average corneal curvature was flatter by 4 D and CCT was reduced by 83 μm (P < 0.0001, for all), postoperatively. Coma aberrations remained unchanged (P = 0.07) while the change in trefoil (P = 0.047) postoperatively, was not clinically significant. The 4th order HOAs (spherical aberration and secondary astigmatism) and the HOA root mean square (RMS) increased from -0.18 ± 0.07 μm, 0.04 ± 0.03 μm and 0.47 ± 0.11 μm, preoperatively, to 0.33 ± 0.19 μm (P = 0.004), 0.21 ± 0.09 μm (P < 0.0001) and 0.77 ± 0.27 μm (P < 0.0001), six months postoperatively. The change in spherical aberration after the procedure increased with an increase in the degree of preoperative myopia.
  
  
  CONCLUSIONS
  Wavefront-guided IntraLASIK offers a safe and effective option for vision and visual function improvement in astigmatism. Although, reduction of HOA is possible in a few eyes, spherical-like aberrations are increased in majority of the treated eyes.
authors.affiliation: Department of Optometry & Vision Sciences, College of Applied Medical Sciences, King Saud University, Riyadh, P.O Box 10219, Riyadh, 11433, Saudi Arabia.
authors.forename: Ferial M
authors.initials: FM
authors.lastname: Al-Zeraid
authors.affiliation: Department of Optometry & Vision Sciences, Faculty of Health, Ophthalmic and Visual Optics Laboratory Group (Chronic Disease & Ageing), Institute of Health and Biomedical Innovation, Q Block, Room 5WS36 60 Musk Avenue Kelvin Grove, Brisbane, QLD, 4059, Australia. osuagoul@aston.ac.uk.
authors.forename: Uchechukwu L
authors.identifier: http://orcid.org/0000-0002-1727-6914
authors.initials: UL
authors.lastname: Osuagwu
mesh_terms: D057128:Aberrometry; D000328:Adult; D001251:Astigmatism / Q000145:classification / Q000601:surgery*; D057108:Corneal Wavefront Aberration / Q000209:etiology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects*; D054018:Lasers, Excimer; D008297:Male; D009216:Myopia / Q000601:surgery; D011183:Postoperative Complications; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult
keywords: Astigmatism; Coma; Distance visual acuity; Femtosecond laser; Higher-order aberration; Intralase; Laser-assisted in situ keratomileusis; Myopia; Spherical aberration; Wavefront-guided