Imaging the optic nerve and ganglion cell layer

New imaging techniques have extended the limitations of visualisation of th e structures of the optic nerve and fundus in the living human eye. Quantit ative reconstruction of depth of the optic nerve head is becoming widely av ailable through the use of the confocal scanning laser ophthalmoscope (cSLO ). A separate method of quantitative depth reconstruction is possible using stereo pairs which is not subject to the same artefacts as the tomographic reconstruction We are investigating the use of these techniques both with conventional stereo imaging and using stereo pairs derived from cSLO images . In these we find that there is additional structural detail evident in th e base of the optic nerve head. Further studies made with an instrument opt imised to image this region show that this corresponds to the lamina cribro sa. Current work is aimed at further extending the limits of imaging using techniques based on optical coherence tomography, which provides additional depth resolution. Results to date with a prototype device show an improvem ent of approximately a factor of 10 in depth resolution and that some separ ate layers of the retina may be visualised including the photoreceptor laye r. The goal is to extend these limits to allow visualisation of the ganglio n cell layer.