In vivo retinal melanin detection with the calibrated depolarization index in polarization-sensitive optical coherence tomography

• Published in: Journal of biomedical optics Vol. 29; no. 12; p. 126001
• Main Authors: Ke, Mengyuan, Jiang, Liqin, Barathi, Veluchamy A., Cheong, Jocelyn, Chua, Jacqueline, Schmetterer, Leopold, Leitgeb, Rainer A., Liu, Xinyu
• Format: Journal Article
• Language: English
• Published: United States Society of Photo-Optical Instrumentation Engineers 01.12.2024
• Subjects: Adult; Animals; Calibration; Female; Guinea Pigs; Humans; Imaging; Male; Melanins - analysis; Melanins - metabolism; Retina - chemistry; Retina - diagnostic imaging; Signal-To-Noise Ratio; Tomography, Optical Coherence - methods; melanin; polarization-sensitive optical coherence tomography; depolarization
• ISSN: 1083-3668; 1560-2281; 1560-2281
• DOI: 10.1117/1.JBO.29.12.126001

A data-based calibration method with enhanced depolarization contrast in polarization-sensitive optical coherence tomography (PS-OCT) was developed and demonstrated effective for detecting melanin content in the eye. We aim to mitigate the dependence between the measured depolarization metric and the intensity signal-to-noise ratio (SNR) for improved visualization of depolarizing tissues, especially in low SNR regions, and to demonstrate the enhanced depolarization contrast to evaluate melanin presence. A function for calibrating the depolarization metric was experimentally derived from the young albino guinea pig, assuming depolarization free in the retina. A longitudinal study of guinea pigs (9 weeks) was conducted to assess the accumulation of melanin during early eye growth. Furthermore, the melanin content of the sub-macular choroid was compared in eyes with light and dark irides involving 14 human subjects in early middle adulthood. We observed an increase in the improved depolarization contrast, which indicates potential melanin accumulation in the early eye development with age in the pigmented guinea pig eyes. We found a significant difference in melanin content between human eyes with light and dark colors. Our proposed calibration method enhanced the visualization of depolarizing structures in PS-OCT, which can be generalized to all kinds of polarization-sensitive imaging and can potentially monitor melanin in healthy and pathological eyes.