title: The effect of riboflavin-ultraviolet A-induced collagen cross-linking on intraocular pressure measurement: an experimental study.
abstract: OBJECTIVE
  To investigate the effect of corneal collagen cross-linking (CCL) on tonopen measurements of intraocular pressure (IOP).
  
  
  METHODS
  CCL with 0.1% riboflavin solution and 30 min of ultraviolet A radiation was performed on the right eye of 15 New Zealand albino adult rabbits (1.8-2.4 kg) (15 eyes). The left eye served as control. IOP was measured by a pressure transducer system (true IOP) and by the tonopen hand-held device (corneal applanation tonometer) before treatment, at 1 week, 1 month and 3 months following CCL. Reference pressure in the globe was increased by increments of 10 mm Hg from 10 to 40 mm Hg, using an anterior chamber infusion on a stand with variable height, and tonopen IOP measurements were recorded for each reference pressure in both eyes.
  
  
  RESULTS
  Before CCL, tonopen readings were similar between the two eyes (p>0.05). Tonopen underestimated the true IOP in all cases. Following CCL treatment, IOP measurements were significantly higher in the treated eye, at all time intervals (0.005<p<0.03). The most significant difference between true and measured IOP was noted at a reference pressure of 20 mm Hg.
  
  
  CONCLUSIONS
  IOP measurements following CCL are overestimated by the tonopen, probably due to increased stiffness of the treated cornea.
authors.affiliation: Department of Ophthalmology, Rabin Medical Center, Petah-Tiqva, Israel.
authors.forename: Eitan
authors.initials: E
authors.lastname: Livny
authors.forename: Igor
authors.initials: I
authors.lastname: Kaiserman
authors.forename: Naama
authors.initials: N
authors.lastname: Hammel
authors.forename: Tami
authors.initials: T
authors.lastname: Livnat
authors.forename: David
authors.initials: D
authors.lastname: Zadok
authors.forename: Kremer
authors.initials: K
authors.lastname: Israel
authors.forename: Irit
authors.initials: I
authors.lastname: Bahar
mesh_terms: D000818:Animals; D003094:Collagen / Q000378:metabolism*; D003319:Corneal Stroma / Q000187:drug effects / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000378:metabolism*; D004548:Elasticity; D007429:Intraocular Pressure / Q000502:physiology*; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011817:Rabbits; D012256:Riboflavin / Q000494:pharmacology*; D014065:Tonometry, Ocular; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin