Objective To assess if optical coherence tomography (OCT) can provide objective measurements of the thickness of the retinal nerve fiber layer (RNFL) in patients with pituitary adenomas, offering a dependable prediction of visual function. Methods Thirty-two eyes of 16 consecutive patients who visited our hospital between January 2007 and December 2008 and were diagnosed with pituitary adenomas compressing the chiasma as determined by magnetic resonance imaging (MRI) were included in the study. All patients underwent transsphenoidal resection of pathologically proven pituitary adenomas by the same surgeon. The patient group consisted of 7 males and 9 females, and the mean age of the patients was (44.4±14.7)years (range 23-67 years). Visual acuity, automated visual fields (VF) and OCT (fast-RNFL program) were assessed before treatment, and 1 week and 3 months after treatment. RNFL thickness was measured with the Stratus OCT Ⅲ and mean deviation (MD) visual field (VF) with the automated Humphrey Field Analyzer (both from Carl Zeiss Meditec, Dublin, CA). Eyes were divided into 3 groups based on the initial VF defect and its evolution. The presence of an initial VF defect in group A either without improvement or had worsened 3 months after treatment, the presence of an initial VF defect in group B with improvement 3 months after treatment, and group C without VF defect either initially or after treatment. Covariance analysis was applied to analyze the data for the mean RNFL measurements and the initial VF defect in the groups. A logistic regression model was used to evaluate the prognostic value of the initial VF defect and the RNFL thickness on the final visual outcome. A paired samples t-test was used to compare preoperative visual acuity and mean RNFL thickness with postoperative visual acuity and thickness. Results For all patients (32 eyes), there are 10 eyes in group A, 11 eyes in group B and 11 eyes in group C. In the eyes with a VF defect before treatment, a greater mean RNFL thickness increased the probabil