Confirmation of visual field abnormalities in the ocular hypertension treatment study

Objective: To determine the frequency with which visual field abnormalities observed on follow-up visual fields for patients in the Ocular Hypertensio n Treatment Study were confirmed on retest. Methods: Between April 1, 1994, and March 1, 1999, 21603 visual fields were obtained from 1637 patients in the Ocular Hypertension Treatment Study. Wh en follow-up visual fields are outside the normal limits on the Glaucoma He mifield Test, the Corrected Pattern Standard Deviation (P<.05), or both, su bsequent follow-up visual fields are monitored to confirm the abnormality. Abnormalities are confirmed if they are again abnormal on the Glaucoma Hemi field Test, the Corrected Pattern Standard Deviation, or both; if the defec t is not artifactual; and if the same index and location are involved. Reli ability criteria used by the study consisted of a limit of 33% for false po sitives, false negatives, and fixation losses. Results: Of the 21603 regular follow-up visual fields, 1006 were follow-up retests performed because of an abnormality (n=748) or unreliability (n=258 ). We found that 703 (94%) of the 748 visual fields were abnormal and relia ble, and 45 (6%) were abnormal and unreliable. On retesting, abnormalities were not confirmed for 604 (85.9%) of the 703 originally abnormal and relia ble visual fields. Conclusions: Most visual field abnormalities in patients in the Ocular Hype rtension Treatment Study were not verified on retest. Confirmation of visua l field abnormalities is essential for distinguishing reproducible Visual f ield loss from long-term variability.