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E.S. Schnitzler, F. Horn, M. Korth; Blue-on-yellow Evoked Potentialsunder Cold-water Provocation Separate between Low-tension Glaucomas and Primary Open-angle Glaucomas . Invest. Ophthalmol. Vis. Sci. 2003;44(13):29.
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Purpose: Vasospasm after a cold-water test is a risk factor in the pathogenesis of low-tension glaucoma (Gasser (1)).Investigations of the blue-sensitive pathway in glaucoma showed differences between normal subjects and patients with primary open-angle glaucoma (Horn et al.(2)). The aim of our study was to investigate changes of the blue-yellow VEP in different types of glaucoma due to cold-water provocation. Methods: Subjects: 17 patients with ocular hypertension (OHT), 19 patients with preperimetric open-angle glaucoma (PPOAG), 22 patients with open-angle glaucoma (POAG), 18 patients with low-tension glaucoma (LTG) and 22 controls. VEP was measured before and after cold-water provocation. A two-channel Maxwellian view system was used to present blue stripe pattern (0,88 c/deg; 460-nm,luminance 330 Td) on bright yellow adaption light (570-nm, luminance 13000 Td).The pattern was presented in the onset-offset mode (offset 500ms, onset 200ms). The area of the field was 30°. Cross hairs provided a central fixation mark. VEP was performed before cold-water provocation as well as two minutes and four minutes after the beginning of the cold-water provocation. Both eyes were tested. Only the results of the first eye were included in the analysis. The amplitude and the peak time of the VEP onset were evaluated. Results: The mean amplitudes of the patients with LTG decreased from 4,35µV before cold-water test to 3,61 µV after 4 minutes cold-water test. This difference was statistically significant (t-test: p=0,034). In addition, there was a significant difference between the mean amplitude of patients with LTG (before: 4,35µV; two minutes: 3,8µV; four minutes: 3,61µV) and normals (before: 6,45µV; two minutes: 6,27 µV; four minutes: 6,53 µV) before and after cold-water provocation (t-test: p<0,05).The other groups showed no decreases in amplitudes with cold-water provocation. Peak times of all glaucoma groups were significantly prolonged in comparism to controls. Cold-water provocation showed no influence on peak times in normals and patients. Conclusions: Only the amplitude of LTG showed a significant reduction due to the cold-water provocation. Thus, the blue on yellow VEP with cold-water provocation can be used as an additional tool in the differentiation of LTG's and POAG's. 1.Gasser P, Ocular vasospasm: arisk factor in the pathogenesis of low-tension glaucoma, Int Ophthalmol, 1989;13(4):281-90 2.Horn FK, Jonas JB, Budde WM, Jünemann AM, Mardin CY, Korth M, Monitoring Glaucoma Progression with Visual Evoked Potentials of the Blue-Sensitive Pathway, IOVS,2002;43(6):1828-1834
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