Outcomes of visual disturbances after methanol poisoning

Methanol poisoning and toxic optic neuropathy is still seen worldwide. Little attention has been paid to the persistent visual disturbances following methanol poisoning. We aimed to evaluate the outcomes of visual disturbances in methanol-poisoned patients referred to us with visual disturbances.

This retrospective observational case series evaluated the outcomes of visual disturbances in patients with methanol poisoning hospitalized in Loghman Hakim and Hazrat Rasoul Akram hospitals between March 2003 and October 2009. Medical charts were evaluated for age, gender, time between consumption and hospital presentation, gastrointestinal symptoms, abnormal neurological findings at presentation and during hospital admission, arterial blood gas results, treatment modalities, history of chronic diseases, and status of vision at presentation and discharge from the hospital. The patients or their relatives were contacted 1 year after the admission date of the last patient and questioned about the status of the patients' vision at the time of hospital discharge, after discharge, and at the time of phone contacts.

A total of 50 patients with methanol poisoning and visual disturbances at presentation survived. Thirty-seven cases were followed; 16 showed visual disturbance improvement before hospital discharge, and 21 had visual disturbance after discharge. Visual disturbances were classified into two groups: severe to total blindness and blurred/snowfield vision. Patients were also grouped into one of four categories: group I: patients whose blurred or snowfield vision completely recovered within up to a maximum of 2 weeks after discharge (n=7); group II, the patients who were blind at the time of discharge (n=5) and partially recovered within a maximum of 3-4 weeks; group III, the patients who were blind at the time of discharge and gained no improvement in their vision (n=5); group IV, who were blind at the time of discharge, partially recovered within few days to approximately 1 month and experienced reduced vision and blindness after about a maximum of 9 months (n=4). Patients whose visual disturbances improved with treatment and the patients in group I were considered as transient (n=23) and groups II, III, and IV as permanent visual disturbance cases (n=14). Significant difference was not seen in age, sex, elapsed time to presentation, gastrointestinal symptoms, abnormal neurological and CT findings, and arterial blood gas results at presentation between the transient and permanent visual disturbance groups. No association existed between the visual disturbance and abnormal neurological and CT findings.

Blurred or snowfield vision in methanol poisoning resolved. However, outcomes of the blindness cannot be predicted. Insome patients, blindness improves but these patients eventually experience reduced vision afterwards.