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John P. Kelly, Sarah Leary, Avery H. Weiss; Changes In Visual Function Before And After Chemotherapy For Optic Pathway Gliomas. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4546.
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Examine the presenting features and long-term changes in visual acuity, visual evoked potentials (VEP), optic nerve appearance, and tumor volume before and after chemotherapy/radiotherapy treatment in children with optic pathway gliomas (OPG) involving the chiasm alone or with anterior / posterior extension.
Twenty-one patients were examined; 16 underwent treatment with vincristine/carboplatin for 18 months (12 cycles) and 5 underwent radiotherapy. Twelve patients required further treatment. Ages at the time of treatment ranged from 9 months to 9 years age. Six had neurofibromatosis type I. All had serial MRI scans, visual acuity measurements (Teller Cards in preverbal infants and Allen or Snellen optotypes in older children), VEPs (supra-threshold check reversal stimuli or grating pattern-onset; 80% contrast), and dilated fundus examination of the optic nerve. Visual acuity was corrected for age (log difference from age matched norms).
Prior to treatment, 35% had subnormal acuity in both eyes, 57% had bilateral optic nerve pallor, and 90% had subnormal VEP amplitude in both eyes. Average and median follow-up time was 9 years (range 0.9-16 years). After treatment, 10 patients had a reduction (>=50%) in tumor volume whilethe remainder had stable volume. On average, acuity was reduced 0.5 logMAR at the end of follow-up. Five patients showed > 0.2 logMAR improvement in acuity (up to 0.5) after treatment and 14 patients had a decline > 0.2 logMAR (up to 2.48). There was a small trend for greater decline in visual acuity with larger tumor volume (r2 = 0.22). All but 3 eyes (93%) had progressive or longstanding optic atrophy. Average VEP amplitude remained stable during treatment, and 1 year after, treatment.
A small minority (33%) of children with OPT involving the chiasm had long-term improvement or stable acuity following chemotherapy. Since the majority of patients had abnormal VEPs prior to treatment, the data suggest pre-existing damage and progressive vision loss limit the effect of chemotheraphy. VEP testing is more sensitive than acuity and optic nerve appearance in the detection of pre-existing optic pathway damage.
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