Axial intensity distribution analysis of the human retina with a confocal scanning laser tomograph.

We have analysed the change of reflected light intensity along the optical axis or axial intensity distribution in images acquired with a confocal scanning laser tomographic system in human fundus examination. We hypothesized that confocal light detection units used in scanning laser tomographs register light originating from multiple layers within the human macula and that intraretinal structures might also be observable. To test this hypothesis we examined the axial intensity distribution in human maculas of normal volunteers, patients with cystic and other macular abnormalities and in an artificial retina in a plastic eye model. A total of over 140 patients and volunteers were examined. We analysed this distribution in 20 normal healthy volunteer eyes found the origin of the artifacts that cause retinal vessels to appear elevated. We examined four patients with cystic maculas and were able to detect the presence of two structures in axial direction contributing to the axial intensity distribution. A plastic eye model with a cellophane sheet covering a fluid pocket was developed to mimic the appearance of a large macular cyst. The axial intensity distribution analysis showed the presence of two distinct gaussian profiles. The results of this study show that confocal scanning laser tomographic imaging of the human fundus allows extraction of information regarding the axial position of intraretinal layers and that correction for the deeper retinal reflections may allow more precision in imaging of the retinal surface.