Introducing the University of California, Irvine Corneal Cystine Crystal Score: A Novel Tool for Assessing Corneal Crystal Deposition in Cystinosis Patients

This study aimed to develop and validate the University of California Irvine Corneal Cystine Crystal Score (UCI CCCS), a novel grading system for objectively assessing corneal crystal deposition in cystinosis patients using a slit lamp biomicroscope. This tool provides a standardized method for monitoring disease progression and evaluating treatment efficacy. This retrospective study analyzed clinical records from 36 cystinosis patients examined at the Day of Hope conference, all with the infantile nephropathic form. The records included evaluations from slit-lamp examinations and Best Corrected Visual Acuity (BCVA). After evaluation, the UCI CCCS was developed by experts in pediatric ophthalmology and cornea specialty; this system differentiates cystine crystal density, iris visibility, and corneal haze on a scale from 0 to 5. For validation, 107 slit-lamp images were assessed by masked graders. Statistical analysis using Intraclass Correlation Coefficient (ICC) and Cohen's kappa was performed to confirm the tool's ability to produce consistent, reproducible results across and within graders. The cohort included 23 males and 13 females (mean age: 15.64 years, range: 0-60). A total of 72 eyes were evaluated. In the validation phase, the UCI CCCS demonstrated high inter-rater agreement (κ = 0.869, P < 0.001) and excellent intra-rater reliability (ICC = 0.922, P < 0.001). The UCI CCCS is a validated, reliable, and reproducible tool for assessing corneal crystal involvement in cystinosis, supporting its clinical and research applications.