Scanning laser ophthalmoscopy

Scanning laser ophthalmoscopy (SLO) is a method of examination of the eye. It uses the technique of confocal laser scanning microscopy for diagnostic imaging of retina or cornea of the human eye.

As a method used to image the retina with a high degree of spatial sensitivity, it is helpful in the diagnosis of glaucoma, macular degeneration, and other retinal disorders. It has further been combined with adaptive optics technology to provide sharper images of the retina.

SLO utilizes horizontal and vertical scanning mirrors to scan a specific region of the retina and create raster images viewable on a television monitor. While it is able to image the retina in real time, it has issues with reflections from eye astigmatism and the cornea. Eye movements additionally can confound the data from SLO.

Adaptive Optics Scanning Laser Ophthalmoscopy (AOSLO) is a technique used to measure living retinal cells. It utilizes adaptive optics to remove optical aberrations from images obtained from scanning laser ophthalmoscopy of the retina.

Scanning Laser Ophthalmoscopy developed as a method to view a distinct layer of the living eye at the microscopic level. The use of confocal methods to diminish extra light by focusing detected light through a small pinhole made possible the imaging of individual layers of the retina with greater distinction than ever before. However, using SLO for monitoring of individual retinal cells proved problematic because of optical aberrations created from the tissues of the anterior eye (specifically the cornea and lens). These aberrations (caused additionally by astigmatism and other factors affecting eye position) diminished lateral resolution and proved difficult to remove.

AO was first attempted for SLO in the 1980s. This first attempt did not use wavefront-detecting technology with its deformable mirror and estimated aberrations through pre-measured factors such as astigmatism. However, this did not diffuse the small monochromatic aberrations resulting from light traveling through the anterior eye both into and out of the pupil during scanning. The invention and adaptation of the Shack-Hartmann wave-front detector for the apparatus produced images of the retina with much higher lateral resolution. The addition of microelectricalmechanical (MEMs) mirrors instead of larger, more expensive mirror deformable mirror systems to the apparatus made AOSLO further usable for a wider range of studies and for use in patients.

...
Wikipedia