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J. P. Kelly, A. H. Weiss; The Time-Course of Changes in Visual Function Before and After Chemotherapy for Optic Pathway Gliomas. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5274.
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Examine the time course of changes in visual acuity, visual evoked potentials (VEP), optic nerve appearance, and tumor volume before and after chemotherapy treatment in children with optic pathway gliomas (OPG) involving the chiasm alone or with anterior / posterior extension.
Twelve patients with OPG underwent treatment with vincristine/carboplatin for 18 months (12 cycles). Ages at the time of treatment ranged from 9 months to 8 years age. Four (33%) 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 (163 and 84’ check reversal stimuli; 80% contrast), and dilated fundus examination of the optic nerve. Visual acuity was corrected for age (log difference from the average of age matched controls).
Prior to treatment, 12 of 23 eyes had normal acuity, 10 of 24 eyes had normal appearing optic nerve, and 3 of 20 eyes had normal VEP amplitude. VEP latency delay was not consistently observed. After treatment 6 patients had a decrease in tumor volume, 3 had stable volume, and 3 showed slightly increased volume. A significant change in acuity was defined as an improvement / decrement more than 0.3 log units (as described by test variation on Teller Acuity Cards) from the pre-treatment acuity. Seven eyes (29%) showed significant improvement in acuity after treatment but only 3 of these remained improved after 1 year. Nine eyes (38%) showed significant decrease in acuity after treatment that lasted more than 1 year. Using a moving average, visual acuity dropped 0.4, 0.45, 0.35, and 0.3 log units at 0.5, 1, 2, and 4 years post-treatment. All eyes with normal pre-treatment VEP amplitude showed a decrease in amplitude 1 year after treatment; the remaining eyes with abnormal VEPs did not significantly change. Nineteen of 24 eyes (79%) showed progressive optic nerve atrophy.
A small minority (13%) of children with OPT involving the chiasm had a long-term improvement in acuity following chemotherapy. Within 6 months after treatment, acuity dropped on average 0.4 log units. Since the majority of patients had abnormal VEPs prior to treatment, the data suggest pre-existing damage and progressive vision loss play a role in 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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