Transdermal Scopolamine: Effects of Single and Repeated Patches upon Aspects of Vision

Transdermal scopolamine and transdermal placebo patches were administered on alternating days to 12 normal volunteer subjects. Visual near-point values and self-reports of blurred vision were systematically assessed 24 hours following each transdermal patch. Blurred vision was not reported following the first scopolamine patch, but became increasingly frequent following successive scopolamine patches. Six of the 12 subjects reported blurred vision by their fourth scopolamine patch. Subjects reporting blurred vision had long initial visual near-points (i.e. were comparatively hypermetropic), whereas subjects not reporting blurred vision had short initial visual near-points (i.e. were comparatively myopic). The visual near-point values of the (hypermetropic) subjects who developed blurred vision became longer following each successive scopolamine patch, whereas the visual near-point values of the (myopic) subjects not reporting blurred vision remained basically unchanged. Visual changes following scopolamine have been previously shown to be slow to develop and slow to dissipate; this slow time course probably produced the cumulative visual problems reported here.