Levodopa and childhood amblyopia

A pilot study was undertaken to address the tolerance and efficacy of levodopa/carbidopa treatment for amblyopia in older amblyopic children who failed to respond to conventional occlusion therapy. Five amblyopic children, between the ages of 7 and 12 years, and two normal adults were given between 100 mg/25 mg and 400 mg/100 mg of levodopa/carbidopa, respectively, depending on body weight. A symptoms questionnaire was completed, with temperature, respiration, heart rate, and blood pressure taken periodically to assess tolerance. Blood samples were taken, via a heparin well, to assess the pharmacokinetics of levodopa, dopamine, noradrenaline, and DOPAC. Snellen visual acuity, contrast sensitivity, stereo acuity, and pattern VERs were measured periodically to assess efficacy. The results revealed a high prevalence of side effects including emesis and nausea (four of seven subjects). Pharmacokinetics revealed that maximum serum levels of levodopa occurred 30 minutes to 1 hour after drug ingestion and decreased by 50% after 2 to 4 hours. One hour after drug ingestion, Snellen visual acuity temporarily improved from an average of 20/159 to 20/83 in the amblyopic eyes. Contrast sensitivity and pattern VERs (10-minute checks) temporarily improved in both dominant and amblyopic eyes, whereas visual function remained stable in normal eyes. The improvements in visual function started to decrease 5 hours after drug ingestion. The results are discussed in the context of developing a therapeutic trial of levodopa/carbidopa for childhood amblyopia.