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A clinical trial to measure effectivity of oral levodopa/carbidopa on visual sensory functioning in subjects with amblyopia and/or anomalous correspondence: Protocols and case report

1 May 2002


BACKGROUND: Recent research has suggested that levodopa!carbidopa (L-dopa), an oral medication that is prescribed for Parkinson's disease, may be effective alternative to treating amblyopia. The goal of this study is to provide clinical protocols to determine whether oral L-dopa can be used to augment standard occlusion therapy to improve sensory function for amblyopic patients with or without strabismus and anomalous correspondence (AC). The study design is a single-masked and pseudo-randomized with control subjects. It was designed to have a 13 week duration period. Visual sensory function will be evaluated in terms of visual acuities, contrast sensitivity, level of stereopsis, and suppression behavior. Amblyopic patients will then be screened through a battery of tests to assess the presence and depth of anomalous correspondence. Patients were excluded if screening tests indicate a poor prognosis for binocular integration after occlusion therapy, and if subjects have any contraindication to L-dopa use. Although this study was originally designed with the intension of enrolling 30 amblyopic subjects, it was modified to be a study design and case report.

CASE REPORT: A 67 year-old man came to Pacific University to improve the alignment of a longstanding Left exotropia and left hypotropia. Two months after strabismus surgery the patient began taking the combination drug L-dopa/ C-dopa to improve the sensory function of his visual system with the ultimate goal to sustain the improved ocular alignment achieved from the strabismus surgery. At the end of the 18 week L-dopa trial the patient's acuities were relatively unchanged from pre-study levels. Minimal changes were also noted in contrast sensitivity as well as objective and subjective ocular alignment measurements. The subject didn't note any subjective improvement in vision.

CONCLUSIONS: Patients that suffer from amblyopia, strabismus, and anamomalous correspondence often are challenging cases to manage for clinicians in terms of meeting patient goals or expectations. Our study focuses on an adjunctive therapy that may lead the way to provide a more beneficial outcome for these patients than standard occlusion therapy alone. It could allow for less aggressive approaches in vision therapy while reducing treatment time. It may also increase success rates in strabismus surgery and reduce the overall number of surgeries required to obtain ocular alignment. At the end of our clinical trial there was little change noted in the Pilot subject's visual acuity, contrast sensitivity and measured angle of strabismus.


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