Longitudinal monitoring by computerized flicker comparison of photographs
J. Funk, G. Pawlowski
Background: Numerous ocular diseases require a longitudinal monitoring to establish the correct diagnosis or the efficacy of treatment. In many of these cases consecutive photographs are taken and then compared to each other. Comparing of consecutive slides can be done by superimposing the images and watching them alternatingly so that changes between two images appear as "flickering" motion. This kind of flicker comparison can now be performed by a commercially available computerized system.
Method: The flicker module is made of three components: 1) a slide scanner, 2) a software routine for the alignment of the images and 3) a software routine to display the aligned images alternatingly.
Results: The total flicker comparison procedure takes about 5 minutes (including the scanning of two slides) or 3 minutes (without slide scanning). In our clinic it is routinely used in monitoring the optic discs of glaucoma patients or glaucoma suspects. In addition, it is also used in monitoring choroidal melanoma, iris nevi or inflammatory retinal disorders. In nearly all cases it led to a precise detection of subtle changes over time.
Conclusion: In our experience, the computerized flicker comparison system allows an easy, quick and reliable evaluation of consecutive photographs. It may be used in routine practice as well as in scientific studies.
University eye hospital, Killianstr. 5, D-79106 Freiburg