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E.P. Herlihy, P.N. Youssef, J.P. Kelly, A.H. Weiss; Structural and Functional Abnormalities of the Macula in Knobloch Syndrome . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4484.
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To describe the structural and electrophysiologic macular abnormalities of two siblings with Knobloch’s Syndrome, a rare genetic mutation of collagen XVIII.
Case series of two siblings evaluated in the ophthalmology clinic and examined under anesthesia with dilated fundus exam, fundus photography, and multifocal electroretinogram.
Clinical evaluation demonstrated the classic findings of Knobloch syndrome in both siblings, including high myopia, vitreoretinal degeneration, macular pigmentary changes, and occipital encephaloceole. Teller acuity testing of sibling A, age 3, revealed visual acuity of 20/260 OD and 20/380 OS. Sibling B, age 7, demonstrated Snellen acuity of 20/200 OU. Cyclopleged refraction was –9.50 +0.50 x 005 OU in sibling A, and –14.50 +0.50 x 100 OD, –14.50 +0.50 x 080 OS in sibling B. Gaze holding was unsteady in both patients. Horizontal jerk nystagmus, with amplitude less than 5 degrees and frequency 2–3 Hertz, was appreciated. Both siblings demonstrated large angle esotropia of greater than 50 diopters. Anterior segment examination was otherwise within nornal limits. Dilated fundus examination performed under anesthesia revealed normal appearing optic nerves, marked vitreous syneresis, generalized chorioretinal thinning with pigmentary mottling, macular geographic atrophy, and blunted foveal reflex in all four eyes. Multifocal ERG was performed during examination under anesthesia. Data were grouped into five annular rings of 3, 5, 7, 10, and 15 degrees centered on the macula, producing similar waveforms and low background noise. The central 10 degrees of each macula showed marked amplitude reduction and increased latency relative to the periphery and to age–matched normative data. The attached ERG data from sibling B are representative of both cases.
Knobloch Syndrome is a rare autosomal recessive genetic disorder that has profound effect on the structure and function of the retina. To our knowledge this is the first report correlating the clinical syndrome with objective multifocal ERG and VEP data.
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