title: Photorefractive keratectomy in the cat eye: biological and optical outcomes.
abstract: OBJECTIVE
  To quantify optical and biomechanical properties of the feline cornea before and after photorefractive keratectomy (PRK) and assess the relative contribution of different biological factors to refractive outcome.
  
  
  METHODS
  Department of Ophthalmology, University of Rochester, Rochester, New York, USA.
  
  
  METHODS
  Adult cats had 6.0 diopter (D) myopic or 4.0 D hyperopic PRK over 6.0 or 8.0 mm optical zones (OZ). Preoperative and postoperative wavefront aberrations were measured, as were intraocular pressure (IOP), corneal hysteresis, the corneal resistance factor, axial length, corneal thickness, and radii of curvature. Finally, postmortem immunohistochemistry for vimentin and alpha-smooth muscle actin was performed.
  
  
  RESULTS
  Photorefractive keratectomy changed ocular defocus, increased higher-order aberrations, and induced myofibroblast differentiation in cats. However, the intended defocus corrections were only achieved with 8.0 mm OZs. Long-term flattening of the epithelial and stromal surfaces was noted after myopic, but not after hyperopic, PRK. The IOP was unaltered by PRK; however, corneal hysteresis and the corneal resistance factor decreased. Over the ensuing 6 months, ocular aberrations and the IOP remained stable, while central corneal thickness, corneal hysteresis, and the corneal resistance factor increased toward normal levels.
  
  
  CONCLUSIONS
  Cat corneas exhibited optical, histological, and biomechanical reactions to PRK that resembled those previously described in humans, especially when the OZ size was normalized to the total corneal area. However, cats exhibited significant stromal regeneration, causing a return to preoperative corneal thickness, corneal hysteresis and the corneal resistance factor without significant regression of optical changes induced by the surgery. Thus, the principal effects of laser refractive surgery on ocular wavefront aberrations can be achieved despite clear interspecies differences in corneal biology.
authors.affiliation: Department of Ophthalmology, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, USA.
authors.forename: Lana J
authors.initials: LJ
authors.lastname: Nagy
authors.forename: Scott
authors.initials: S
authors.lastname: MacRae
authors.forename: Geunyoung
authors.initials: G
authors.lastname: Yoon
authors.forename: Matthew
authors.initials: M
authors.lastname: Wyble
authors.forename: Jianhua
authors.initials: J
authors.lastname: Wang
authors.forename: Ian
authors.initials: I
authors.lastname: Cox
authors.forename: Krystel R
authors.initials: KR
authors.lastname: Huxlin
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001699:Biometry; D002415:Cats; D003315:Cornea / Q000503:physiopathology* / Q000601:surgery*; D019781:Corneal Topography; D006956:Hyperopia / Q000503:physiopathology / Q000601:surgery; D007429:Intraocular Pressure / Q000502:physiology; D054018:Lasers, Excimer; D008297:Male; D009216:Myopia / Q000503:physiopathology / Q000601:surgery; D018903:Photorefractive Keratectomy; D012029:Refraction, Ocular / Q000502:physiology; D041623:Tomography, Optical Coherence; D014945:Wound Healing / Q000502:physiology