Late Excessive Corneal Flattening, Corneal Thinning And Hyperopic Shift At 14-15 Years Following Epithelium Off Corneal Crosslinking (Cxl) For Keratoconus.

To report on  two patients with late excessive corneal flattening, corneal thinning and hyperopic shift at 14-15 years following epithelium off corneal crosslinking (CXL) for Keratoconus.

University Hospital, London United Kingdom

Patient A underwent CXL to his right eye (Dresden protocol) in 2006 at age 25 following  a 1 diopter (D) increase in refractive cylinder in his better eye, with his left eye having grade II-III keratoconus. Pre-op: SEQ was plano, K2 was 43.8D, and CCT was 493µm. Eight years post-op, his acuity was 20/15 with +0.75D sphere and -0.75D cylinder at 30°, K2 was 41.75D, and CCT was 486µm.

Patient B underwent Right eye CXL in 2009 at age 25 as over  2 years refractive cylinder increased by 0.75D to 2.50D (SEQ -1.25D), and acuity dropped to 20/30. At 5 years post-op, acuity remained 20/30 with +0.25D sphere and -2.00D cylinder at 60°, K2 was 41.5D, and CCT was 527µm. Both patients missed follow-ups for 9 years.

Patient A presented 17 years after CXL with increasing hyperopia over 2 years. Acuity was 20/25 with +4.50D sphere and -1.25D cylinder at 30°, CCT 497µm, and K2 37.1D. Stromal haze was present. Twelve months later, acuity was 20/30 with +4.50D sphere and -3.50D cylinder at 2°, CCT 495µm, and K2 36.5D.

Patient B presented 15 years post-CXL with reduced vision for 6-12 months. Acuity was 20/30 with +4.50D sphere and -1.5D cylinder at 50°, CCT 497µm, and K2 38.4D. Stromal haze was present. Twelve months later, acuity worsened to 20/40-2 with +6.00D sphere and -1.50D cylinder at 35°, CCT 519µm, and K2 38.2D. Both patients had left CXL with good refractive/keratometric stability (an intrastromal ring segment in patient A’s left eye was removed).

Two patients presented with hyperopic shift, corneal flattening and corneal thinning at 17 and 15 years respectively following CXL grade I Keratoconus. This highlights the need for long-term to follow-up of any novel medical procedure to ascertain possible long-term complications and that refractive and keratometric stability cannot be guaranteed following CXL. The pathophysiology of such changes is uncertain.