This retrospective study aimed to report the incidence, characteristics, clinical presentations, risk factors, and the available treatment modalities of sterile peripheral ulcerative keratitis (PUK) post-corneal collagen crosslinking (CXL). In total 771 eyes of 474 patients operated for keratoconus or ectasia after LASIK were included. The average follow-up period was 4.2 years with a minimum of one year post-CXL. Patients were followed up every six months post-CXL, and those diagnosed with ulcerative keratitis were followed up weekly until resolution. Intrastromal corneal ring segments (ICRS) were implanted in 383 eyes four weeks before CXL and simultaneous photorefractive keratectomy (PRK) was performed on the same operative day on 74 eyes. Cross-linking involved using a mixed Riboflavin 0.1% dextran solution (isotonic) for 30 minutes followed by ultraviolet B (UVB) exposure at 3.0±0.3 mW/cm2 for a total of 30 minutes and less UVB exposure time in relatively older patients with less advanced keratoconus. Eleven (1.4%) eyes of eight patients developed late-onset sterile PUK between three months and six years post-CXL (average 3±2.26 years). PUK was associated with exposure to UVB light at an older age, and this was found to be statistically significant. Sex, thinnest corneal pachymetry, mean keratometry, and the presence of ICRS were not related to the development of late PUK. Three general immunologic diseases (allergy, Crohn’s disease, and uveitis) were identified in four of the affected patients. The authors hypothesised that the imbalance between the metalloproteinases and their tissue inhibitors in patients with keratoconus is exacerbated by CXL and that the presence of inflammatory or autoimmune diseases may have led to the development of sterile PUK. Management of the affected patients was successful using topical steroid eye drops with resolution of symptoms within one to two weeks. Only one patient who was known to have allergic conjunctivitis had multiple recurrences in both eyes over a one-year period, but eventually responded to Cyclosporine 1% eye drops. 

Late-onset sterile peripheral ulcerative keratitis post-corneal collagen crosslinking.
Chanbour W, Mokdad I, Mouhajer A, Jarade E.
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Bushra Thajudeen

Singleton Hospital, Swansea, UK.

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