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Visual Electrophysiology Unit

Research activities

Translational research from cellular elements to neuro-visual functioning in children

The focus of research is the interface between disease or toxicity inducing cellular changes and neuro-retinal function in childhood.

Retinal toxicity attributed to vigabatrin

The VEU is conducting a prospective cohort study assessing neuro-visual functions in children with a paediatric seizure disorder (infantile spasms) who were treated with the anti-epileptic drug vigabatrin. Approximately 30 per cent of adult patients treated with this drug develop vigabatrin attributed visual field defect. Using the electroretinogram as a surrogate marker for visual field defect we found that approximately 35 per cent of children with Infantile Spasms develop vigabatrin attributed retinal toxicity. Findings from this investigation resulted in a change in vigabatrin prescribing practice; the length of vigabatrin treatment was reduced to minimize the occurrence of toxicity. The data on vigabatrin toxicity in a paediatric cohort were presented in the Ovation Pharmaceuticals new drug application (NDA) submission to the Food and Drug Administration (FDA), presented at the FDA advisory Committee Meeting for vigabatrin, Washington DC January 2009 and are published (Invest Ophthalmol Vis Sci. 2009, and J Child Neurol 2012.)

Neuro-visual structure and function in children and adolescents with early Type 1 Diabetes

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The VEU is conducting studies of visual dysfunction in Type 1 Diabetes to define the earliest neuro-marker of disease. Chromatic mechanisms are disrupted at puberty (Invest Ophthalmol Vis Sci. 2005) and short-wavelength retinal processing disrupted in adolescence (Invest Ophthalmol Vis Sci. 2011). Multifocal electroretinography in adolescents show deficits in localized retinal processing (Invest Ophthalmol Vis Sci. 2010). We are the first to report on multi-model adaptive optics imaging to study the effect of localized functional disturbance on the integrity of cone photoreceptors in children with Type 1 Diabetes (Tan, W., et al., Functional and Structural Cone Abnormalities in Adolescents with Type 1 Diabetes, IOVS 2012; 53: ARVO E-Abstract 371.)  These studies allow us to identify the earliest signs of diabetic eye disease.

Phenotypic Characteristics in Cone Dystrophies

High resolution imaging animation
High resolution imaging of the human eye shows the cone photoreceptor mosaic

For the past two years, in collaboration with Dr. Elise Héon, we characterized retinal phenotype in diseases with known mutations. Data are published in Retina (2012), Ophthalmic Genetics (2011) and Molecular Vision (2011). Recently we published data from In vivo imaging of the Cone Photoreceptor Mosaic in children with cone dystrophy and the KCNV2 mutation (Investigative Ophthalmology (2013). This is the first study of Ultra-high resolution retinal imaging in this population and the first report of retinal imaging of the cone mosaic in children.

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