Longitudinal Measures of Visual Function, Tumor Volume, and Prediction of Visual Outcomes after Treatment of Optic Pathway Gliomas

Abstract

To examine longitudinal changes in visual acuity, tumor volume, and visual evoked potentials (VEP) before and after treatment in children with optic pathway gliomas. Retrospective cohort study. Twenty-one patients (0.7-9 years of age). Patients initially were treated either by chemotherapy (n = 18) or radiotherapy (n = 3). Patients were followed up with serial magnetic resonance imaging, age-corrected visual acuity measurements in logarithm of the minimum angle of resolution (logMAR) units, and pattern VEP. Longitudinal visual outcome data were obtained on average for 9 years (range, 4-16 years). Tumor volumes before and after treatment were estimated in 15 patients. Multivariate regression was used to predict visual outcomes. Visual acuity, relative tumor volumes, and VEP. Before treatment, 81% of patients had reduced visual acuity and 81% had optic nerve pallor, whereas all had a reduced VEP in 1 or both eyes. After initial treatment, tumor volume decreased in 53%, stabilized in 27%, and progressively increased in 20%. Treatment arrested the rapid decline in visual acuity loss and stabilized visual acuity for 4 to 5 years. The rate of visual acuity decline was not correlated with tumor shrinkage. Sixty-two percent of patients required additional treatment with either chemotherapy or radiation because of tumor growth or progressive loss of visual function. Visual acuity at last examination was stable or improved in 33% of patients, but on average declined 0.4 logMAR units. Visual acuity was 20/200 or better in 1 eye of 62% of patients. The rate of visual acuity decline was predicted weakly by tumor volume at presentation (R(2) = 0.19; P<0.009). Visual acuity at last examination was predicted best by visual acuity and tumor volume at presentation (R(2) = 0.66; P<0.001). Systemic chemotherapy arrested the decline in visual acuity and stabilized vision on average for 5 years. At presentation, VEPs were a more sensitive indicator of optic pathway damage than visual acuity or optic nerve appearance. Although tumor reduction or stabilization was achieved in 80% of patients, pre-existing visual damage, indexed by objective measures of tumor volume and visual function, limited visual outcomes. The author(s) have no proprietary or commercial interest in any materials discussed in this article.