Photophobia and corneal crystal density in nephropathic cystinosis: an in vivo confocal microscopy and anterior-segment optical coherence tomography study

Abstract

Purpose: To analyze the correlation between photophobia and corneal crystal density in nephropathic cystinosis using in vivo confocal microscopy (IVCM) and anterior-segment optical coherence tomography (AS-OCT).

Methods: Forty eyes of 20 patients with nephropathic cystinosis aged 7 to 37 years were included in this study. Ophthalmologic investigations included clinician-assessed and self-assessed evaluations of photophobia, slit-lamp biomicroscopy analysis, the depth of crystal deposition (DCD) and the central corneal thickness (CCT) in the central cornea measured with AS-OCT, and IVCM analysis of the crystal density score (IVCM-CysS), inflammatory cell density (IVCM-inf), and nerve damage (IVCM-N). Age, sex, intraleukocyte cystine concentrations (ICC), and the need for renal transplantation were also recorded.

Results: The average subjective and objective photophobia scores were 2.10 ± 1.28 and 1.70 ± 1.41, respectively. Using AS-OCT, the average percentage of crystal infiltration (OCT-CysP) and was 49.56 ± 27.31% (range, 11.45%-95.81%). The mean IVCM-CysS was 8.84 ± 4.34, the mean density of inflammatory cells (IVCM-inf) was 178.28 ± 173.00 cells/mm2, and the mean IVCM-N score was 3.11 ± 2.11. Clinician- and self-assessed estimations of photophobia were correlated (R2 = 0.61). No significant correlation was observed between clinician- and self-assessed photophobia scores and ICC or sex. There were significant correlations between clinician- and self-assessed photophobia scores and age, OCT-CysP, IVCM-CysS, IVCM-inf, and IVCM-N. The IVCM-CysS was also correlated with OCT-CysP (R2 = 0.27), IVCM-inf (R2 = 0.37), and IVCM-N (R2 = 0.56).

Conclusions: In vivo confocal microscopy and AS-OCT are reliable tools to quantify cystinosis corneal crystals. In patients with nephropathic cystinosis, the intensity of photophobia is associated with the density of crystals, infiltration of inflammatory cells, and nerve damage within the cornea.