Prospective one year study of corneal biomechanical changes following high intensity, accelerated cornea cross-linking in patients with keratoconus using a non-contact tonometer

Purpose To characterize corneal biomechanical properties utilizing a dynamic ultra-high-speed Scheimpflug camera equipped with a non-contact tonometer (CorVis ST, CST) in keratoconic corneas following continuous high intensity, high irradiance corneal cross-linking. Design Prospective longitudinal single-centre study at a tertiary referral center. Methods Corneal biomechanical properties were measured in patients with progressive keratoconus undergoing high intensity (30 mW/cm(2)), high irradiance (5.4 J/cm(2)), accelerated corneal cross-linking with continuous exposure to ultraviolet-A for 4 min. CST was used to assess corneal biomechanical properties pre-operatively and at 1, 3, 6 and 12 months post-operatively. CST output videos were further analyzed using several previously reported algorithms. Results A total of 25 eyes of 25 participants were examined. The mean age of participants was 20.9 +/- 5.3 years; 56% were male and 80% were of Maori or Pacific Island origin. Energy absorbed area (mN mm), was the only significantly changed parameter compared to baseline at all time points measuring 3.61 +/- 1.19 preoperatively, 2.81 +/- 1.15 at 1 month (p = 0.037), 2.79 +/- 0.81 (p = 0.033) at 3 months, 2.76 +/- 0.95 (p = 0.028) at 6 months and 2.71 +/- 1.18 (p = 0.016) at 12 months. Conclusions The significant difference between the pre and post-operative energy absorbed area appears to reflect changes in corneal viscous properties that occur following corneal cross-linking.