Macular Degeneration: Vonthein R

Scholl HP, Schuster AM, Vonthein R, Zrenner E. · Department of Pathophysiology of Vision and Neuro-Ophthalmology, University Eye Hospital, Schleichstrasse 12-16, 72076 Tübingen, Germany. · Vision Res. · Pubmed #11934455 No free full text.

Abstract: In order to evaluate the function of the retina in Best macular dystrophy (BMD) 18 patients were examined by means of the multifocal electroretinogram (mfERG). The mfERG peak amplitudes of the central and pericentral responses were significantly reduced in the BMD patients (p<0.001). The ERG amplitude decrease of the central response was significantly correlated with visual acuity loss and with the funduscopic staging. The implicit times in more eccentric groups were slightly but significantly increased. The markedly reduced mfERG amplitudes with only slightly increased implicit times may indicate cone photoreceptor cell loss or damage to the cone outer segments.

Scholl HP, Besch D, Vonthein R, Weber BH, Apfelstedt-Sylla E. · Department of Pathophysiology of Vision and Neuroophthalmology, University Eye Hospital Tübingen, Tübingen, Germany. · Invest Ophthalmol Vis Sci. · Pubmed #11923272 links to  free full text

Abstract: PURPOSE: To investigate the slow and fast rod signals of the scotopic 15-Hz flicker ERG in patients with molecularly confirmed Stargardt disease type I (STGD1). There is evidence that these slow and the fast rod ERG signals can be attributed to the rod bipolar-AII cell pathway and the rod-cone coupling pathway, respectively. METHODS: Twenty-seven patients with STGD1 with mutations in both alleles of the ABCA4 gene were included. Scotopic ERG response amplitudes and phases to flicker intensities ranging from -3.37 to -0.57 log scotopic troland x sec (log scot td x sec) were measured at a flicker frequency of 15 Hz. In addition, scotopic standard ERGs were obtained. Twenty-two normal subjects served as controls. RESULTS: The amplitudes of both the slow and fast rod ERG signals were significantly reduced in the STGD1 group. The phases of the slow rod signals lagged significantly, whereas those of the fast rod signals did not. The standard scotopic ERG did not reveal significant alterations. CONCLUSIONS: The results provide evidence that a defective ABCA4 transporter can functionally affect both the rod bipolar-AII cell pathway and the rod-cone coupling pathway. In STGD1, the scotopic 15-Hz flicker ERG may reveal subtle abnormalities at different sites within the rod system that remain undetected by standard ERG techniques.

Scholl HP, Kremers J, Vonthein R, White K, Weber BH. · Department of Experimental Ophthalmology, University Eye Hospital, Röntgenweg 11, 72076 Tübingen, Germany. · Invest Ophthalmol Vis Sci. · Pubmed #11328755 links to  free full text

Abstract: PURPOSE. To study the dynamics of the long (L)- and middle (M)-wavelength-sensitive cone-driven pathways and their interactions in patients with Stargardt's macular dystrophy-fundus flavimaculatus (SMD-FF) and to correlate them with other clinical parameters and individual genotypes. METHODS. Forty-seven patients with SMD-FF participated in the study. In addition to standard 30-Hz flicker electroretinograms (30-Hz fERG), ERG responses were measured to stimuli that modulated exclusively the L or the M cones (L/M cones) or the two simultaneously. Blood samples were screened for mutations in the 50 exons of the ABCA4 gene. RESULTS. Patients with SMD-FF did not show a decrease in the mean L/M-cone-driven ERG sensitivity, but there was a significant increase in the interindividual variability. The mean L-/M-cone weighting ratio was normal. However, the L-cone-driven ERG was significantly phase delayed, whereas the M-cone-driven ERG was significantly phase advanced. These phase changes were significantly correlated with disease duration. The amplitude and implicit time of the standard 30-Hz fERG both correlated significantly with the L/M-cone-driven ERG sensitivity and with the phase difference between the L/M-cone-driven ERGs, indicating the complex origin of the standard 30-Hz fERG. Probable disease-associated mutations in the ABCA4 gene were found in 40 of 45 patients, suggesting that they form a genetically fairly uniform SMD-FF study group. There was no correlation between the genotype and the L/M-cone-driven ERGS: CONCLUSIONS. The changes in L/M-cone-driven ERG sensitivity and phase possibly represent two independent disease processes. The phase changes are similar to those found in patients with retinitis pigmentosa and possibly are a general feature of retinal dystrophies.