To determine whether laboratory markers of methanol ingestion and subsequent toxicity can serve as predictors of visual outcomes in patients.
Retrospective medical record review of 122 patients in a cluster outbreak of methanol poisoning. Data collected included history, complete ocular and systemic examination details, time to presentation, amount of alcohol ingested, and results of laboratory investigations, such as hemogram, glucose levels, hematocrit level, arterial pH, methanol levels, potassium and bicarbonate levels, and anion and osmolar gap determination, as well as hepatic and renal function tests. Therapy administered consisted of ethyl alcohol, sodium bicarbonate, and nutritional supplements, with hemodialysis in severe cases. Visual acuity (VA), pupillary reaction, and optic disc findings were assessed at presentation and 3 months after discharge. Patients were classified according to their visual disturbance: transient (group 1) or permanent (group 2). Appropriate statistical analysis was performed. Outcome measures included determining the association between biochemical markers of methanol poisoning and final VA.
A total of 122 patients (1 female and 121 male) were admitted for treatment; of these, 10 died. Only 1 patient showed a 2-line drop in VA. pH was the strongest predictor of final VA and improvement in VA among all markers. The odds that a patient with an initial pH greater than 7.2 would have only transient visual disturbances were high (odds ratio, 31; 95% CI, 6-149).
The degree of acidosis at presentation appears to determine final VA; early presentation and treatment did not seem to significantly alter the visual outcome, especially in severe poisoning.