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The effect of riboflavin–ultraviolet A-induced collagen cross-linking on intraocular pressure measurement: an experimental study
  1. Eitan Livny1,2,
  2. Igor Kaiserman3,
  3. Naama Hammel1,2,
  4. Tami Livnat1,2,
  5. David Zadok4,
  6. Kremer Israel1,2,
  7. Irit Bahar1,2
  1. 1Department of Ophthalmology, Rabin Medical Center, Petah-Tiqva, Israel
  2. 2Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
  3. 3Department of Ophthalmology, Barzilai Medical Center, Ashkelon, Israel
  4. 4Department of Ophthalmology, Asaf Harofe Medical Center, Zrifin, Israel
  1. Correspondence to Dr Irit Bahar, Department of Ophthalmology, Rabin Medical Center, 39 Zabutinski Street, Petah-Tiqva 49100, Israel; iritbahar{at}


Purpose 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.

  • Collagen cross-linking
  • cornea
  • imaging
  • intraocular pressure
  • lens and zonules
  • neovascularisation
  • riboflavin
  • UVA

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  • Funding EL is a recipient of a Rabin Medical Center grant for young researchers (Kornovski fund) and Martie fund, Tel Aviv University.

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.