The Use of a Viscous Cysteamine Eyedrop in a Belgian Cohort: Early 3-Year Results

With the life expectancy of patients with cystinosis increasing (ORPHA213), the corneal burden and the objective assessment of corneal crystal deposition have become increasingly important. Previous research highlights the disadvantages of hospital-prepared cysteamine solutions (HPCS), including limited efficacy, which can lead to visual decline. Cystadrops^® is a viscous topical treatment in cystinosis care that counteracts these disadvantages.

A total of 14 patients with cystinosis and corneal involvement are being followed in the multidisciplinary cystinosis clinic of the University Hospital of Leuven. Data retrieved between September 2014 and March 2023 were analyzed. All patients were initially treated with HPCS before switching to Cystadrops^®. Patients were assessed yearly according to the standard clinical ophthalmological examination for patients with cystinosis developed by Pinxten et al. Photophobia, corneal crystal deposition, and corneal crystal deposition depth were measured by the Liang cystinosis photophobia score, Gahl score, and anterior segment optical coherence tomography (OCT) respectively. Corneal densitometry was assessed with Scheimpflug imaging.

OCT mean crystal depth was 83% of total corneal thickness. The mean corneal density was 28.9 grayscale units. We found a positive trend (F = 0.20, p = 0.65) in corneal densitometry despite the use of HPCS, with a decreasing trend (F = 3.30, p = 0.08) after switching to Cystadrops^®. Photophobia scores significantly reduced after switching treatments (p = 0.008). In total, seven patients developed anterior segment complications while using HPCS. No new anterior segment complications developed while using Cystadrops^®.

This study underscores previous research, demonstrating HPCS' limited effectiveness in reducing corneal crystal deposition due to unachievable dosing frequencies and poor stability. Our data highlights the effectiveness of Cystadrops^® in treating the ocular symptoms of cystinosis. The data demonstrates the difficulty of reversing high levels of corneal crystal deposition and anterior segment complications. Starting Cystadrops^® early in the disease course may prevent high rates of crystal deposition, thus reducing complications and their impact on vision and quality of life.