Comparison of scanning laser tomography and polarimetry in nerve fiber measurements
S. Kremmer, F. Fanihagh, J. M. Selbach
Purpose: Recently, different scanning laser techniques (scanning laser tomography SLT and polarimetry SLP).have been introduced to measure nerve fibers in glaucoma. A main problem to compare the results of these different devices was to find a proper allignement and to compare measurements exactly at the same locations. Therefore, we developed a new computersoftware.
Methods: We examined 100 eyes of five different examination groups (20 normal young patients, 20 normal old patients, 20 normal tension glaucoma (NTG), 20 beginning primary open angle glaucoma (POAG), 20 advanced POAG ). Beside standard ophthalmological examinations, SLP (GDx 1.0.14, LDT USA) and SLT (ToppSS 3.0.16, LDT USA) were performed. We developed a new computer software which allowed to import/export tomographic data into the polarimetry device followed by allignment procedures enabling evaluations at the same locations. We compared SLP and SLT measurements along peripapillary circles at four different distances of the optic disc margin. For statistical analyses, Wilcoxon signed ranks test was used.
Results: There was a significant statistical difference (p<0.0001) in the SLT and SLP data of all five groups.
Discussion: The reason for these differences may be due to the fact that in SLT not only nerve fibers but also all other tissues (e.g. blood vessels, glial tissue, etc.) are measured whereas in SLP nerve fibers are assessed. Therefore, SLT and SLP measurements should not be equaled especially at pathological conditions e.g. glaucoma.
University Eye Hospital, Hufelandstr. 55, D-45122 Essen