Depth of tissue sampling in the optic nerve head using laser Doppler flowmetry

Abstract

Laser Doppler flowmetry (LDF) was performed on a simulated blood vessel in a model eye through optic nerve tissue sections in order to ascertain the ability to detect flow through them. LDF was performed using either near-infra-red or green laser light. Tissue section thickness ranged from 50 μm to 1000 μm. As expected, we found that our ability to detect flow with LDF decreased as we increased the thickness of optic nerve sections interposed between the LDF apparatus and the simulated blood vessel. We also found that the sampled depth of LDF increased with increasing separation of the optical detection fibre from the centre of the illuminated tissue volume. With adequate separation, we were able to detect flow with LDF through tissue sections of 1000 μm thickness using either near-infra-red or green laser light.