Validation of a Portable Tool for Conjunctival Ultraviolet Autofluorescence Imaging

Conjunctival ultraviolet autofluorescence (CUVAF) is an objective biomarker of ocular sun exposure, aiding in the assessment of ophthalmohelioses and other UV-related eye conditions. However, conventional CUVAF imaging requires a bulky and costly benchtop digital single-lens reflex (DSLR) camera system. This study evaluates the validity of a smartphone-based clip-on tool as a portable, affordable alternative for CUVAF imaging.

95 participants were recruited from an ophthalmology clinic in Sydney, Australia. Nasal and temporal conjunctival images were captured using both DSLR-based and smartphone-based systems. CUVAF was quantified using two parameters: area ratio (CUVAF area relative to visible sclera) and intensity ratio (CUVAF mean intensity relative to adjacent background). Agreement between systems were assessed using Bland-Altman analysis.

The mean age of participants was 58 ± 14 years, with 42% identifying as male. CUVAF area ratios were slightly higher in smartphone images (0.037 ± 0.03) compared to DSLR (0.022 ± 0.02, p < 0.01). Intensity ratios showed no significant difference between systems (smartphone: 1.35 ± 0.24, DSLR: 1.37 ± 0.28, p = 0.43). Bland-Altman plots demonstrated good agreement, with mean differences of - 0.014 for area and 0.041 for intensity.

The smartphone-based CUVAF imaging tool demonstrates strong agreement with the gold-standard DSLR system, supporting its potential for clinical and field-based assessment of ocular UV exposure. Slight differences in measured CUVAF area are likely attributable to inherent differences in optical geometry and magnification between the two devices, not underlying biological variation.