Afferent visual function after single dose application of -vinyl GABA

Abstract

The authors studied the short term effects of a transient increase in global GABA on retinal functions. GABA is an inhibitory transmitter in the central nervous system and in the retina as well, γ-Vinyl GABA (GVG) irreversibly inhibits the GABA degrading enzyme GABA transaminase. It is known to reverse visual dysfunction induced by various conventional antiepileptic drugs. The authors performed a double-blind, placebo controlled cross-over study of visual functions on 24 healthy volunteers 24 hours after a single dose of 3 g GVG. The investigation included visual acuity, slit-lamp examination, fundoscopy, intraocular pressure, kinetic and static perimetry, spatial contrast sensitivity and color discrimination with pseu-doisochromatic plates and Farnsworth-Munsell 100 hue test. Clinical ophthalmologic examination did not show any significant abnormalities, both after placebo and GVG. Similarly, visual fields, color discrimination and contrast sensitivity were unaffected. In six subjects minor color discrimination abnormalities in the blue-yellow range during placebo were functionally reversed by GVG.

Key Words:

• Vigabatrin
• γ-vinyl GABA
• GABA
• afferent visual function
• perimetry; contrast sensitivity
• color vision