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Salar Rafieetary, Joshua Barnett, Natalie Kerr, Alessandro Iannaccone; Retinal Changes and Nerve Fiber Layer Loss in Pediatric Patients on Vigabatrin: An Electroretinogram and Imaging Study. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5317. doi: https://doi.org/.
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Vigabatrin (VGB) is used to treat drug-resistant seizures and seizure disorders such as infantile spasms and complex partial seizures. Vision impairment, especially bilateral visual field constriction, is well-documented in adults on VGB. Visual function monitoring is required for dispensing VGB. No single diagnostic test has yet emerged as the optimal one to screen children on VGB for visual system abnormalities. Our aim was to better characterize the spectrum of clinical and functional signs of VGB-mediated toxicity in pediatric patients via serial dilated fundus exams, spectral domain optical coherence tomography (SD-OCT), and flash electroretinograms (ERG).
We performed a retrospective, longitudinal, 3-year observational study of nine patients with various epileptic disorders (age 0.5-17 years old) treated with therapeutic levels of VGB for an average of 1.4 years. Outcome measures included changes in retinal nerve fiber layer (RNFL) thickness and macular microanatomy by SD-OCT, clinically visible funduscopic changes, and retinal function changes by flash ERG criteria, all assessed under anesthesia (propofol) in a pediatric hospital setting. After baseline evaluations, patients were reevaluated every 6 months until VGB was discontinued.
All patients had abnormalities either in funduscopic exam, SD-OCT and/or ERG at initial evaluation. During follow-up, three of the nine patients exhibited changes in either RNFL thickness, ERG, or both, which were interpreted as possible signs of VGB-related toxicity. Two of these 3 patients also demonstrated funduscopic changes, including peri-vascular sheathing and retinal pigment epithelium (RPE) discoloration. ERG changes were localized to the photoreceptor and post-receptor level under both dark adapted and light adapted conditions. We did not observe any consistent areas of RNFL thinning in our case series.
Our findings show that children treated with VGB are at risk of suffering heterogeneous adverse effects to their visual system. A combination of flash ERG, SD-OCT and fundus photographs can be used to monitor these patients for signs of VGB toxicity. The identification of baseline abnormalities emphasizes the importance of obtaining baseline measurements in a VGB toxicity screening protocol and the consideration of other medical comorbidities that may contribute to visual system dysfunction.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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