title: Corneal collagen cross-linking combined with simulation of femtosecond laser-assisted refractive lens extraction: an ex vivo biomechanical effect evaluation.
abstract: OBJECTIVE
  To evaluate biomechanical changes induced by in situ corneal cross-linking (CXL) with stromal pocket delivered enhanced concentration riboflavin and high-fluence, high-energy UV-A irradiation.
  
  
  METHODS
  Eight human donor corneas were subjected to intrastromal lamellar corneal tissue removal of anterior 140-μm deep, 80-μm thick × 5-mm diameter central stromal buttons, extracted through a 3.5-mm width tunnel, surfacing in the superior cornea periphery. Enhanced concentration riboflavin solution (0.25%) was instilled in the pocket. In study group A (CXL), superficial high-fluence UV-A irradiation was applied, whereas in control group B (no CXL), none. To comparatively assess changes in corneal rigidity, corneal specimens were subjected to transverse biaxial resistance measurements by application of a unidirectional tangential shear force. Biomechanical differences were evaluated through stress and Young shear modulus.
  
  
  RESULTS
  Stress at 10% strain was 305 ± 24 kPa in study group A versus 157 ± 11 kPa in control group B (relative difference Δ = 107%, P = 0.021). Stress at 20% strain was 1284 ± 34 kPa in study group A versus 874 ± 29 kPa in control group B (Δ = 47%, P = 0.043). Average shear modulus in study group A at 10% strain was 6.98 ± 1.12 MPa versus 4.04 ± 0.85 MPa in control group B (Δ = 73%, P = 0.036). Average shear modulus in study group A at 20% strain was 11.46 ± 0.75 MPa versus 8.80 ± 0.72 MPa in group B (Δ = 30%, P = 0.047).
  
  
  CONCLUSIONS
  Adjunct CXL in this ex vivo simulation refractive lens extraction procedure seems to provide significant increase in corneal rigidity, up to +107%. These findings also support our previous reported work on laser in situ keratomileusis combined with CXL.
authors: *Laservision.gr Clinical and Research Eye Institute, Eye Institute, Athens, Greece; †New York University Medical School, New York, NY; ‡Empire Eye Physicians, Spokane, WA; and §Affiliated Eye Hospital of Wenzhou Medical University, Zhejiang, China.
authors: Anastasios J
authors: AJ
authors: Kanellopoulos
authors: Mark A
authors: MA
authors: Kontos
authors: Shihao
authors: S
authors: Chen
authors: George
authors: G
authors: Asimellis
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D002387:Cataract Extraction; D003094:Collagen / Q000378:metabolism*; D003315:Cornea / Q000187:drug effects* / Q000502:physiology*; D063171:Corneal Pachymetry; D003319:Corneal Stroma / Q000378:metabolism; D003432:Cross-Linking Reagents; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D012256:Riboflavin / Q000627:therapeutic use*; D014019:Tissue Donors; D041623:Tomography, Optical Coherence; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin