Objectives: To quantify the effect of long-term reduction of plasma ornithine levels through adherence to an arginine-restricted diet on visual function in patients of all ages with gyrate atrophy of the retina and choroid. Methods: A long-term observational study was conducted on 27 patients with gyrate atrophy, 17 of whom elected to comply with the arginine-restricted diet and 10 who were unable to comply. The mean rates of change in the electroretinogram combined response, electroretinogram flicker response, and kinetic and static perimetry were determined. Results: After mean follow-up of 13.9 years for the patients on the diet and 14.1 years for those not on the diet, the mean rates of change for the diet group compared with those of the no-diet group were statistically significantly slower for all outcome measures (age-adjusted P<.05) except for static perimetry (P=.06). Conclusions: Adhering to an arginine-restricted diet so as to lower the plasma ornithine level below an average of 5.29 to 6.61 mg/dL (400-500 μmol/L) will slow the loss of function as measured by sequential electroretinography and visual field examinations.
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