title: Effect of vitreous length and trephine size disparity on post-DALK refractive status.
abstract: OBJECTIVE
  To evaluate the effect of vitreous length (distance between posterior lens surface and vitreoretinal interface) and donor-recipient disparity on the refraction and keratometric astigmatism after deep anterior lamellar keratoplasty (DALK).
  
  
  METHODS
  In this retrospective comparative study, 85 eyes of 83 patients with keratoconus underwent DALK using the big-bubble technique. A 0.25-mm oversize donor was used for a vitreous length of ≥ 16.0 mm, and a 0.50-mm oversize donor for a vitreous length of <16.0 mm. At least 3 months after complete suture removal, spherical equivalent refractive error (SE), keratometric astigmatism, and mean keratometry were compared between the 2 groups. Multiple regression analysis was performed in group 1 to investigate the correlation between vitreous length and SE, between vitreous length and keratometric astigmatism, and between mean keratometry and SE.
  
  
  RESULTS
  Mean patient age was 26.5 ± 7.7 years, and they were followed for 22 ± 10 months postoperatively. Seventy-five eyes received a 0.25-mm oversize donor (group 1), and 10 had a donor oversized by 0.50 mm (group 2). Compared with group 1, the patients of group 2 had a significantly steeper cornea (46.83 ± 2.0 vs. 48.29 ± 1.9 diopters, respectively; P = 0.01). SE and keratometric astigmatism in group 1 did not significantly differ from those in group 2. In group 1, there was a significant association between vitreous length and SE and between mean keratometry and SE but not between vitreous length and keratometric astigmatism.
  
  
  CONCLUSIONS
  In DALK, a donor oversized by 0.25 mm is advisable for elongated keratoconic eyes, whereas a 0.50-mm oversize donor is advocated for small ones.
authors.affiliation: Department of Ophthalmology, Labbafinejad Medical Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad Ali
authors.initials: MA
authors.lastname: Javadi
authors.forename: Sepehr
authors.initials: S
authors.lastname: Feizi
authors.forename: Ali
authors.initials: A
authors.lastname: Rastegarpour
mesh_terms: D000293:Adolescent; D000328:Adult; D001251:Astigmatism / Q000503:physiopathology; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography; D016039:Corneal Transplantation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007640:Keratoconus / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D012029:Refraction, Ocular / Q000502:physiology*; D012189:Retrospective Studies; D014019:Tissue Donors; D014792:Visual Acuity / Q000502:physiology; D014822:Vitreous Body / Q000473:pathology*