Visual Functions in Locally Advanced Nasopharyngeal Carcinoma Patients after External Beam Radiation

Abstract

Purpose: To evaluate the effects of radiation to the anterior visual pathway in locally advanced nasopharyngeal carcinoma (NPC) patients after low energy photon external beam radiation. Design: A cross-sectional, observational case series. Methods: Fifty- one patients treated with the same radiotherapy were assessed in visual acuity (VA), color vision, visual field (VF), and contrast sensitivity. The patients with post radiation interval of ≤ 3 years were defined as group 1, of > 3 years as group 2, and healthy volunteers as control group 3. The visual functions were analyzed between the three groups. Results: One patient in group 1 developed radiation-induced optic neuropathy (RION) with decreased VA, color vision defect, decreased contrast sensitivity, and VF defect. No RION was detected in group 2. There was no statistical significance in color vision defect (P = 0.303) or mean contrast sensitivity (P = 0.235) between the three groups. There was statistical significance in mean contrast sensitivity value (P = 0.044) between the irradiated and non-irradiated group. Conclusions: This study reported the acceptable incidence of RION in 1.96% of locally advanced NPC patients after external beam radiotherapy. Significant decrease in contrast sensitivity was the subclinical anterior visual pathway abnormality, observed among the irradiated group. Monitoring subjective and objective visual changes is helpful for irradiated patients in detecting and assessing treatment for minimizing long term devastating results on the visual conditions.