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M.–B. Jeong, M. Seeliger, L. Galle, K.–M. Seo, K. Narfström; The Efficacy for Functional Evaluation of Feline Hereditary Rod Cone Degeneration Using a Portable Mini–Ganzfeld Electroretinography Unit . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1058.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the efficacy for obtaining the diagnosis of feline hereditary retinal degeneration using a portable mini–Ganzfeld electroretinography (ERG) unit. Previous studies using an extended protocol for study of rod and cone function in Abyssinian cat hereditary retinal degeneration on a tabletop, conventional full–field ERG has shown a reduction in scotopic high intensity a–wave amplitude with corresponding increase in b/a wave ratio to be diagnostic for early stage disease.
Eleven affected cats in different stages of disease and four normal controls were anesthetized and studied using a protocol for differentiation of rod and cone function with (a) a conventional full–field ERG equipment (Tor, Global Eye Program, Rejmyre, Sweden), and (b) a new portable ERG unit (HMsERG, RetVetCorp Inc, Columbia, MO, USA). A– and b–wave amplitudes and implicit times were evaluated along with waveform shape, b/a–wave ratios and oscillatory potentials (OPs). The latter were obtained from responses to high intensity stimuli under scotopic conditions through digital filtering.
The ERGs obtained using the portable unit were similar to those of the conventional tabletop unit. In affected animals, the mean amplitude of the a–wave was significantly lower already in early disease ((a) 116 +/– 44 µV and (b) 197 +/–82 µV) compared to results of controls ((a) 307 +/– 65 µV and (b) 559 +/–115 µV). B/a–wave ratios of affected cats were significantly increased in early disease compared to those of normal cats. The reduction of OPs in affected cats, seen with both instruments, appeared to be one of the causative factors for the differences in ERG waveform shape between affected and normal cats.
The portable ERG gave results that were remarkably similar to the conventional full–field ERG equipment in both normal and affected animals. Although subject to further evaluation, this study shows the efficacy of the portable unit in the diagnosis of generalized photoreceptor disorders. Additional work is underway to establish reference ranges using the portable mini–Ganzfeld ERG for research and in the clinical practice.
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