Near Infrared Autofluorescence Lifetime Imaging of Human Retinal Pigment Epithelium Using Adaptive Optics Scanning...

Area of Science:

• Ophthalmology
• Biomedical Optics
• Retinal Imaging

Background:

• The human retinal pigment epithelium (RPE) cellular mosaic plays a crucial role in retinal health.
• Non-invasive imaging techniques are needed to assess RPE structure and function in vivo.
• Fluorescence lifetime imaging ophthalmoscopy (FLIO) offers potential for functional retinal assessment.

Purpose of the Study:

• To demonstrate the first in vivo near-infrared adaptive optics fluorescence lifetime imaging ophthalmoscopy (NIR-AOFLIO) measurements of the human RPE cellular mosaic.
• To visualize RPE lifetime changes at different retinal eccentricities.
• To investigate the origin of the NIR fluorescence signal.

Main Methods:

• NIR reflectance and autofluorescence were captured using a custom adaptive optics scanning light ophthalmoscope in 10 healthy subjects at seven eccentricities.
• Repeatability was assessed across two visits up to 8 weeks apart.
• Retinal extracts from Abca4-/- mice were imaged to probe fluorescence origin.

Main Results:

• The RPE mosaic was resolved in younger subjects (<35 years old) across all locations.
• Mean fluorescence lifetime was longer in near-peripheral regions (8° and 12°) compared to near-foveal regions (0° and 2°).
• Repeatability showed moderate to excellent correlation; mean lifetime was longer in drusen-containing eyes than in healthy eyes. Fluorescence was observed only in pigmented mouse extracts.

Conclusions:

• NIR-AOFLIO is a repeatable technique for in vivo visualization of the RPE cellular mosaic.
• The observed fluorescence signal likely originates predominantly from melanin.
• Observed variations suggest NIR-AOFLIO may serve as a functional biomarker for monitoring early retinal alterations, particularly in conditions like age-related macular degeneration.