Changes in corneal parameter 18 months following Collagen cross linkage treatment (CXL) for keratoconus , cohort study. (Preprint)

BACKGROUND Keratoconus (KC) is a progressive, bilateral, asymmetric corneal degeneration. KC is as a common disease in the general population, with prevalence ranging up to 200 per 100 000. Twenty percent of keratoconus patients present with irregular astigmatism leading to severe visual deterioration (1) . The inciting mechanism for keratoconus remains unknown, however genetic and environmental factors have been implicated. Environmental factors include excessive eye rubbing, allergy and sun exposure which can lead to greater expression of reactive oxygen species (2). Collagen cross linkage (CXL) is now an established treatment in isolation and in conjunction with other modalities of manging keratoconus (3, 4) . Keratoconus is highly prevalent in Saudi Arabia (5). CXL is also an established procedure in different eye institutions of the Kingdom with promising outcomes (6, 7). The earlier publications from central, eastern and western cities of the Kingdom had one year follow up. To the best of our knowledge, outcome of intervention from Macca city of western Saudi Arabia with a long term follow up is not available that could add to literature. We present outcomes of collagen cross linkage treatment and its determinants after 18 months in eyes with keratoconus at Macca, Saudi Arabia. OBJECTIVE To evaluate impact of 18 months after collagen cross linkage treatment and its determinants in eyes with keratoconus in Western Saudi Arabia. METHODS This was a one armed cohort study. Cases of keratoconus treated by Collagen cross linkage treatment (CXL) at our institute between 2015 and 2016 were included. Demographic data and grade of keratoconus (Amsler - Krumiech classification) at presentation were correlated to change in corneal parameters 18 months after CXL compared to that at presentation. RESULTS Our cohort had 45 eyes with keratoconus. Stage I, II, III and IV keratoconus were 13,14,2 and 16 eyes respectively. The K max significantly declined (Wilcoxon P = 0.05). The success of stabilizing corneal ectasia was achieved in 29/39 = 74.4%. Spherical equivalent refractive status changed from median -1.5D to -2.5D (WP =0.002). Central corneal thickness significantly reduced from median 471 to 460 ((WP =0.001). The Best corrected Visual acuity remained same 0.6 at 18 months follow up. Kmax based stabilization of cornea was not associated to the grade of keratoconus. (c2 = 2.2, P = 0.1). Stabilization of keratoconus was not associated to gender (P = 0.9) and laterality (P = 0.3). CONCLUSIONS The steepening of cornea stabilized 18 months after collagen cross linkage treatment. But vision remained same and cornea thinned out. There was a myopic shift for refractive status. Stabilization of corneal parameters did not vary significantly by grades of keratoconus. CLINICALTRIAL Keratoconus; corneal dystrophies; corneal ectasia; collagen cross linkage; CXL.