Customised Topography-Guided Corneal Cross-Linking (Cxl) For Progressive Keratoconus: 24 Month Results

CXL is the gold-standard treatment to halt disease progression in keratoconus and prevent further deterioration of vision. Two-thirds of patients undergoing CXL already have impaired vision due to irregular astigmatism. Customised CXL is a new iteration of CXL in which a bespoke treatment pattern based on pre-operative tomography is applied to the cornea. This aims to reduce surface shape irregularities, thereby improving corrected vision. The primary objective of this study is to investigate visual outcome in patients with progressive keratoconus treated with customised CXL. 

Cornea and External Diseases Department, Moorfields Eye Hospital, United Kingdom

Patients with progressive stage I-III keratoconus and CDVA < 0.00 logMAR were eligible for the study. Manifest refraction, logMAR visual acuity and tomography were collected at baseline, 6, 12 and 24 months. Following mechanical removal of the corneal epithelium, 0.1% riboflavin drops were instilled every 2 minutes for 10 minutes. UVA irradiation was applied in three concentric circles at an irradiance of 30 mW/cm², pulsed every 1.5 seconds. The largest (9 mm diameter, 5.4 J/cm²) was centered on the pupil, with two smaller zones (4 mm, 10.5 J/cm² & 6mm, 8.5 J/cm²) centered on the maximum anterior tangential curvature. 

65 eyes of 56 patients were analysed, 71% were male. Mean age was 27.6 (± 8.4) years. CDVA improved from 0.15 ± 0.15 logMAR preoperatively to 0.08 ± 0.16 logMAR at 24 months (p=0.15). 56% of eyes gained 1 line or more of CDVA. There was an overall flattening of Kmax from 55.6 ± 5.5 D at baseline to 54.3 ± 4.1 D at 24 months (p<0.001). No eye showed progression of keratoconus at 24 months. The higher total UVA irradiation did not have an adverse effect on endothelial cell counts or corneal clarity. No cases of infective keratitis were recorded.

CXL irradiation patterns can be customised based on corneal tomography to selectively improve corneal shape and CDVA in keratoconic eyes. There were no cases of keratoconus progression or adverse effects. However, there appear to be minimal gains from the customised irradiation patterns; with a modest flattening of Kmax and a non-significant CDVA gain of approximately 3 logMAR letters.