Background Patterns of ganglion cell complex (GCC) loss detected by optical coherence tomography provide an objective measure of optic nerve injury. These patterns aid in early diagnosis and localization of chiasmal lesions. Methods Twenty-three patients with chiasmal compression seen between 2010 and 2015 were imaged with the Cirrus high-definition optical coherence tomography macular cube 512 × 128, retinal nerve fiber layer (RNFL) scan protocols and automated (30-2 Humphrey) visual fields (VFs). Age-matched controls were included for comparison. Generalized estimating equations were performed comparing RNFL and GCC thicknesses between patients and their controls. Effect size (d) was calculated to assess the magnitude of difference between patients and controls. The average GCC and RNFL thicknesses also were correlated with VF mean deviation (MD). Pre operative average GCC thickness was correlated to post operative VF MD. Results Patterns of GCC thinning corresponded to VF defects. The average GCC thickness was 67 ± 9 μm in patients and 86 ± 5 μm in controls (P < 0.001). The effect size was the greatest for GCC thickness (d = 2.72). The mean deviation was better correlated with GCC thickness (r2 =0.25) than RNFL thicknesses (r2 =0.15). Postoperatively, VF MD improved in 7 of 8 patients with persistent nasal GCC thinning. Six patients had no VF defect and showed statistically significant loss of GCC compared with controls (P = 0.001). Conclusions Distinct patterns of GCC loss were identified in patients with chiasmal compression. Binasal GCC loss was typical and could be seen with minimal or no detectable VF loss. Thinning of the GCC may be detected before loss of the RNFL in some patients. After decompression, the majority of patients showed improvement in VF despite persistent GCC loss. Patients with less GCC loss before decompression had better postoperative VFs. Therefore, GCC analysis may be an objective method to diagnose and follow patients with chiasmal lesions.