Landmark-driven fundus perimetry using the scanning laser ophthalmoscope

To present a new method of performing scanning laser ophthalmoscope perimetry that compensates for eye movements so that the correct retinal location is tested even if fixation changes. This allows for accurate testing of patients with central scotomas and for repeating testing longitudinally at the same retinal locations even if central fixation is lost.

The operator views the retina and selects a retinal landmark, such as a vessel bifurcation, that can be identified easily. A testing strategy is preselected, and the computer saves the landmark and stimulus coordinates. To present each stimulus, the operator positions a cursor over the retinal landmark, and the computer adjusts the site of presentation of the stimulus for any change in landmark position caused by an eye movement. At the conclusion of the testing, the results are displayed in the proper retinal location on a fundus image.

Sixty-seven eyes with macular disease were tested with the landmark-driven method, using the same preplanned strategy for each eye for both a bright and a dim stimulus. There was a low rate of inconsistent points (seen with dim but not bright stimuli), and virtually all of these bordered a dense scotoma. Those eyes with more inconsistent points had a significantly greater percentage of dense scotoma points and significantly lower visual acuity. The technique significantly corrected error in retinal localization resulting from large eye movement. There is no significant rotation or magnification change during the procedure, so specifying the change in location of one landmark is sufficient to describe movement of the retina. The technique is rapid and easy to administer to elderly patients and to children.

This technique allows for accurate and repeatable measures of retinal sensitivity in specific locations. It is useful in following change over time. It can be developed further to allow for fully automated, retinally correct testing.