Power distribution of collimated coherent radiation at 1061 nm over the corneal thickness

This study examines the local transmission of normal and pathological corneal tissues when exposed to coherent collimated near-infrared (NIR) radiation with a wavelength of 1061 nm, highlighting its potential advantages over ultraviolet (UV) radiation for antimicrobial photodynamic therapy (PDT). The proposed measurement method, which employs an original experimental setup with a collimated NIR laser source and a probe fiber for direct layer-by-layer depth profiling, allows for determining the transmission values at specific depths within the cornea. Considering that the affected areas are localized within 1/3 to 1/2 of the corneal thickness, the residual power of the NIR radiation in the posterior part of the affected zone (at a depth of 250-400 µm) does not exceed 20%. However, the residual power of the NIR radiation at the posterior epithelium of the affected cornea, after passing through its entire thickness, does not exceed 10%. Current UV-based antimicrobial corneal PDT suffers from limited depth penetration and low specificity, hindering effective treatment and requiring photoprotectors to shield the non-regenerating posterior epithelium. NIR-based PDT, using selective photosensitizers, offers a promising alternative. The results of our NIR corneal transmittance measurements are crucial for the development of more targeted, effective, and safer therapies.