Abstract

We have used a confocal scanning laser ophthalmoscope (cSLO) to measure human photopigment density as a function of retinal location. The cSLO produces 20 × 17° video images of the fundus, which are digitized (8 bits) for subsequent analysis. In each session, one laser was selected as the bleaching and test beam, while another (790 nm) was used to image the fundus during dark adaptation or pigment regeneration. To obtain two-way densities, fundus images were stored at 10-s intervals following exposure to the bleaching beam. Image realignment is easily attained at the two-pixel level. Measurement artifacts were primarily due to reflections from retinal structures, such as the fovea, the internal limiting membrane, and the nerve fibers. External reflectance standards were digitized in each image to control for dark current and temporal changes in the detector or laser. We investigated internal reflectance standards also, such as vessel contrast and reflections from the scleral crescent, if present. Infrared images do not afford a suitable reference for changes over the retina, since these images exhibit contrasts and reflections different from images taken at visible wavelengths. A 2-mm confocal collection aperture typically gives lower two-way density estimates than the 12.5-mm confocal aperture. This is consistent with findings that the tightly confocal arrangement is selective for retinal surface features. Two-way optical densities referred to 555 nm were 0.27-0.45 for the central 0.4°.

© 1988 Optical Society of America