Background: Individuals with acute zonal occult outer retinopathy (AZOOR) present with initially progressive scotomata and photopsia. Characteristically, the extent of the visual field defect is unexplained by fundal examination, but there is marked retinal dysfunction evident electrophysiologically. It is the authors' experience that a group of patients exhibit characteristic clinical and electrophysiological abnormalities, which serve as criteria for a working diagnosis. Methods: A retrospective observational case series of 28 patients were identified with the clinical diagnosis of AZOOR who shared similar abnormal electrophysiology. Details of the history and ophthalmic findings were obtained from the case notes. Results: Electrophysiology demonstrated a consistent pattern of dysfunction both at the photoreceptor/ retinal pigment epithelial complex but also at inner retinal levels, essentially comprising a delayed 30 Hz flicker ERG and a reduction in the EOG light rise. Conclusion: This study determines diagnostic criteria applicable to a group of patients with AZOOR, typically those with classic symptomatology. Electrophysiological testing can help avoid lengthy, costly, and potentially invasive investigations, and the unnecessary use of immunosuppressive therapy.
Community (QLG2-CT-1999-00988) (to FM), CAICYT of Spanish Ministerio de Ciencia y Tecnología (SAF99-0025) (to FM), and Fondo de Investigaciones Sanitarias (FIS 00/0244) (to IdC).
Aims: To characterise the detailed phenotype of ''cone dystrophy with supernormal rod ERG'' in a case series of 10 patients. Methods: 10 affected patients were examined clinically and underwent colour fundus photography, with nine undergoing detailed electrophysiological testing. Five patients were assessed further with fundus autofluorescence (AF) imaging, automated photopic and dark adapted perimetry, and dark adaptometry. Detailed colour vision assessment was performed in six subjects. Blood samples were taken from four patients for DNA extraction and mutation screening of NR2E3 was undertaken. Results: The onset of symptoms was in the first and second decades of life. Subjects presented with reduced central vision and marked photophobia. All individuals were myopic and colour vision testing revealed severely reduced colour discrimination predominantly along the red-green axes; tritan colour vision was relatively well preserved. Nyctalopia is a later feature of the disorder. Funduscopy and AF imaging revealed a range of macular appearances. There was electrophysiological evidence of marked macular dysfunction, reduced and delayed cone responses, and supernormal and delayed rod responses. Photopic and dark adapted perimetry revealed central scotomata with widespread peripheral sensitivity loss. No disease causing sequence variants in NR2E3 were identified. Conclusions: The largest case series to date has been described of the clinical, psychophysical and electrophysiological characteristics of this unusual cone dystrophy with supernormal rod responses. Electrophysiological data were consistent with a post-phototransduction, but pre-inner nuclear layer, site of dysfunction. While the definitive diagnosis can only be made with electrophysiological testing, several characteristics that may increase suspicion of this diagnosis are presented.T he cone and cone-rod dystrophies are a clinically and genetically heterogeneous group of retinal disorders. 1 2 A range of different phenotypes have been described including an unusual cone disorder associated with supernormal and delayed rod ERG b-waves. [3][4][5][6][7][8] This retinal dystrophy was first described by Gouras et al in two siblings with generalised loss of cone vision, clinical evidence of progression, and nyctalopia.3 Cone ERGs were markedly reduced while the rod b-wave was supernormal in amplitude in response to intense flashes, but smaller than normal and delayed over the lower intensity series. Alexander and Fishman reported two similar cases with supernormal rod ERGs without nyctalopia, suggestive of good rod function despite an abnormal scotopic ERG.
The pattern electroretinogram is a retinal response that can be evoked by viewing an alternating grating or checkerboard. It is receiving increasing clinical and research attention because it can provide information about inner retinal cells and the macula. However, clinicians may have trouble choosing between different techniques for recording the Pattern electroretinogram that have been described in the literature. The International Society for Clinical Electrophysiology of Vision has prepared guidelines for a basic pattern electroretinogram recording procedure to aid new users in obtaining reliable responses and to encourage more uniformity among existing users.
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