Longitudinal changes in retinal structure and visual function after mild methanol inhalation poisoning

To characterizes the retinal structural and functional changes in patients with mild methanol poisoning.

This study enrolled 17 patients (34 eyes) with methanol poisoning. All patients received comprehensive treatment based on disease severity. Participants were classified as Group 1 if either eye exhibited a best-corrected visual acuity (BCVA) worse than 0.1 logMAR at initial presentation. Group 2 contained those with BCVA of 20/25 or better. Ophthalmic evaluations were conducted at initial presentation and at 2 weeks, 1, 2, 3, and 4 months after exposure. The longitudinal changes in macular ganglion cell-inner plexiform layer (GCIPL) thickness, peripapillary retinal nerve fiber layer (RNFL) thickness, cup-to-disc ratio (C/D), visual field index (VFI) and mean deviation (MD) were analyzed.

Group 1 experienced significant BCVA recovery (p < 0.001) while Group 2 maintained consistently normal vision throughout the study (p = 0.234). Group 1 showed marked improvement in VFI and MD (both p < 0.001). Group 2 maintained high baseline VFI with slight but significant improvement (p < 0.001) and modest MD gains (p = 0.001). The VFI in Group 1 remained lower than Group 2 at all visits (all p < 0.01). Structurally, both groups exhibited progressive RNFL and GCIPL thinning (p < 0.001), though more severe in Group 1. Group 1 also showed sharper GCIPL reduction, particularly within the first two weeks.

Mild methanol poisoning can cause progressive structural and functional damage even in patients with normal vision. This dissociation between functional improvement and structural deterioration underscores the necessity for long-term monitoring and the development of neuroprotective strategies.