title: Higher-order aberrations in young refractive surgery candidates in India: establishment of normal values and comparison with white and Chinese Asian populations.
abstract: OBJECTIVE
  To establish normal values of higher-order aberrations (HOAs) in young candidates in an Indian population and compare them with results in white and Asian (Chinese) populations.
  
  
  METHODS
  Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India.
  
  
  METHODS
  This prospective trial comprised 206 consecutive candidates (412 eyes) for customized laser in situ keratomileusis. Exclusion criteria were previous ocular surgery, corneal ectasia, rigid gas-permeable contact lens use, corneal scar, or cataract. Higher-order aberrations were analyzed on a Zywave workstation (Bausch & Lomb Surgical).
  
  
  RESULTS
  The mean age was 23.63 years +/- 1.99 (SD); the mean refractive error, -2.97 +/- 4.0 diopters (D) sphere and -1.73 +/- 3.6 D cylinder; and the mean 6.0 mm HOA root mean square (RMS), 0.36 +/- 0.26 microm. The most predominant HOAs were 3rd order (coma, trefoil). The summated RMS of the 3rd order was the most predominant (mean 0.23 +/- 0.15 microm), followed by the 4th and 5th orders (P<.0001). The ratio between summated RMS means was 1:0.7:0.3, similar to that in white populations (1:0.7:0.3) and different than in Asian (Chinese) populations (1: ~ 0.8:0.002). Third- and 4th-order aberrations were between 60% and 70% higher in Asian (Chinese) eyes. The difference between data in this study and those in others was less than 10% in 3rd and 4th order.
  
  
  CONCLUSIONS
  The normative data for HOA in Indian eyes closely matched that in white populations but was different from that in Asian (Chinese) populations, which may provide help in nomogram modifications.
authors.affiliation: Cornea and Refractive Surgery Services, Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India. drgauravprakash@gmail.com <drgauravprakash@gmail.com>
authors.forename: Gaurav
authors.initials: G
authors.lastname: Prakash
authors.forename: Namrata
authors.initials: N
authors.lastname: Sharma
authors.forename: Vandana
authors.initials: V
authors.lastname: Choudhary
authors.forename: Jeewan S
authors.initials: JS
authors.lastname: Titiyal
mesh_terms: D000293:Adolescent; D000328:Adult; D044466:Asian People / Q000208:ethnology*; D001251:Astigmatism / Q000208:ethnology* / Q000503:physiopathology / Q000601:surgery; D003315:Cornea / Q000503:physiopathology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006956:Hyperopia / Q000208:ethnology* / Q000503:physiopathology / Q000601:surgery; D007194:India / Q000453:epidemiology; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer; D008297:Male; D009216:Myopia / Q000208:ethnology* / Q000503:physiopathology / Q000601:surgery; D011446:Prospective Studies; D012016:Reference Values; D012029:Refraction, Ocular; D012846:Singapore / Q000453:epidemiology; D044465:White People / Q000208:ethnology*