Long-term results of combined transepithelial phototherapeutic keratectomy and corneal collagen crosslinking for keratoconus: Cretan protocol

J Cataract Refract Surg. 2014 Sep;40(9):1439-45. doi: 10.1016/j.jcrs.2014.01.040.


Purpose: To present the long-term results of combined transepithelial phototherapeutic keratectomy (PTK) and corneal collagen crosslinking (CXL) for keratoconus.

Setting: Vardinoyiannion Eye Institute of Crete, University of Crete, Heraklion, Crete, Greece.

Design: Prospective case series.

Methods: Patients with progressive keratoconus had combined transepithelial PTK and CXL (Cretan protocol). Visual and refractive outcomes and the endothelial cell density (ECD) were evaluated preoperatively and postoperatively.

Results: Twenty patients (23 eyes) were enrolled; postoperatively 23 eyes were evaluated at 1 and 2 years, 11 at 3 years, and 7 at 4 years. The mean follow-up was 33.83 months±10.82 (SD) (range 24 to 56 months). No intraoperative or postoperative complications occurred. The mean uncorrected distance visual acuity improved significantly from 0.99±0.57 logMAR preoperatively to 0.61±0.36 logMAR at the last follow-up (P<.001) and the mean corrected distance visual acuity, from 0.27±0.24 logMAR to 0.17±0.14 logMAR (P=.018), respectively. The mean steep and mean flat keratometry readings decreased significantly from 53.39±7.14 diopters (D) and 47.17±4.87 D, respectively, preoperatively to 49.99±4.36 D (P<.001) and 45.47±2.95 D (P=.002), respectively, at the last follow-up. The mean corneal astigmatism improved significantly from -6.27±4.19 D preoperatively to -4.52±2.80 D (P<.001) at the last follow-up. No significant ECD alterations occurred (P>.05).

Conclusion: Combined transepithelial PTK and CXL was effective and safe in keratoconic patients over a long-term follow-up.

Financial disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Collagen / metabolism*
  • Combined Modality Therapy
  • Corneal Stroma / metabolism*
  • Cross-Linking Reagents*
  • Epithelium, Corneal / surgery
  • Female
  • Follow-Up Studies
  • Humans
  • Keratoconus / drug therapy
  • Keratoconus / metabolism
  • Keratoconus / surgery
  • Keratoconus / therapy*
  • Lasers, Excimer / therapeutic use
  • Male
  • Photochemotherapy / methods*
  • Photorefractive Keratectomy / methods*
  • Photosensitizing Agents / therapeutic use
  • Prospective Studies
  • Refraction, Ocular / physiology
  • Riboflavin / therapeutic use
  • Ultraviolet Rays
  • Visual Acuity / physiology
  • Young Adult


  • Cross-Linking Reagents
  • Photosensitizing Agents
  • Collagen
  • Riboflavin