Healthy term infants who are not breast-fed may need long-chain polyunsaturated fatty acids (LCPUFA) in their feeding, based on the changes in plasma and tissue fatty composition. However, consistent functional effects across different studies conducted over the past two decades has been more difficult to document. The interpretation of these data has scientific and public interest with the introduction of LCPUFA supplemented formula. There are 14 controlled trials in term infants that have included formula feeding with or without LCPUFA and functional assessment of visual and other measures of neural development; in addition, 7 have evaluated specific measures related to cognitive development. We chose to examine the effect of DHA dose provided daily on the development of visual acuity to explain the differences in visual acuity responses across randomized studies. A "meta-regression" was performed with the use of a DHA effective dose as the independent variable and visual acuity at 4 months as the dependent variable. Since the two main dietary determinants of DHA status are the LNA provided and the preformed DHA consumed, we defined DHA equivalent dose across studies by assuming a 1%, 5%, and 10% conversion of LNA to DHA. Results indicate a strong and significant effect of DHA equivalent dose on magnitude of the visual acuity response at all conversions tested; greatest significance was found when using a 10% bioequivalency (r(2)=0.68, and P=.001). We conclude that there is a significant relation between the total DHA equivalents provided and effectiveness as defined by visual acuity measurements at 4 months of age.