Central Toxic Keratopathy Post Corneal Collagen Cross Linking - A Case Series

Central toxic keratopathy (CTK) have been reported earlier post LASIK and post photorefractive keratectomy (PRK). There is no association reported of CTK post corneal collagen cross linking (CXL). We would like to report a case series comprising of 10 cases of CTK post CXL We would also like to propose the clinical features of CTK and how it differs from corneal scarring post CXL.

Cataract and Refractive Surgery Services, LV Prasad Eye Institute, Hyderabad, India.

We retrospectively evaluated the patients who developed CTK post CXL. Accelerated protocol was performed in all patients where the riboflavin solution was used along with the ultra-violet A (UVA) light. The uniformity of light source used in the CXL equipment is calibrated using digital handheld optical power and energy meter (console: PM100D and sensor: SC120, M/s. THORLABS, New Jersey, USA). A wavelength of 400nm is typically used for measuring the energy as the CXL equipment uses a UVA source of wavelength between 315 - 400nm. Post CXL a bandage contact lens was applied for 1 week and patients were kept on topical antibiotic for 1 week along with topical low potent steroids and topical tear substitutes for 1 month.

There was no any gender preference for CTK. All patients who developed CTK, presented to the clinic within a weeks time post CXL. The CTK had a very characterisitc feature of disciform shaped corneal haze in the central cornea with a very distinct border. There were striae present within this localized haze along with stromal thinning  which can be very well appreciated in anterior segment OCT image. The haze disappeared without any intervention. There was no any overlying epithelial defect, surrounding cornea was quiet. With time there was flattening in the cornea in the area of haze and there was a hyperopic shift which was reduced at 3 months. All patients were managed conservatively.

There is subtle difference between CTK and corneal scarring post CXL. The clinical examination along with diagnostic evaluation (Oculyzer and anterior segment OCT) helps differentiate between the two. All the patients were managed conservatively without any intervention and there is no role of topical steroids in these patients as the condition is non-inflammatory. Through these 10 cases we have attempted to throw some light on a distinct clinical entity which has similar clinical features compared to CTK post refractive surgery and how to differentiate between the two.