ITEM 50. DISTANT VISION
Third-Class: 14 CFR 67.303(a)
(a) Distant visual acuity of 20/40 or better in each eye separately, with or without corrective lenses. If corrective lenses (spectacles or contact lenses) are necessary for 20/40 vision, the person may be eligible only on the condition that corrective lenses are worn while exercising the privileges of an airman certificate.
Third-Class: 14 CFR 67.303(b)
(b) Near vision of 20/40 or better, Snellen equivalent, at 16 inches in each eye separately, with or without corrective lenses.
Requirements for distant and near vision as per the above.
Chapter and verse for anything else:
http://www.faa.gov/about/office_org/...t_download.pdf
Any questions, drop me a line.