Aim. To study a possible relationship between dimensions of the optic chiasm and extent of visual field impairment in patients with pituitary adenoma. Methods. Pre-operative magnetic resonance (MR) scans and Goldmann perimetry charts of patients having undergone resection of a pituitary adenoma were retrieved. Area of the chiasm (A (chiasm)), central height of the chiasm (H (chiasm)), and perpendicular height of tumour (H (tumour)) were measured on coronal images using standard software. Visual fields were quantified by subdividing the central 30 degrees of vision into 72 subunits each bounded by 15 degree meridians and 10 degree isoptres. Results. Nineteen patients were included in this study. There was a strong statistically significant linear correlation between H (chiasm) and bitemporal (Pearson’s coefficient r = -0.69, p = 0.001), binocular (r = -0.63, p = 0.004) and binasal (r = -0.52, p = 0.01) central field loss. A similar relationship was observed between H (tumour) and bitemporal (r = 0.55, p = 0.015) and binocular (r = 0.46, p = 0.05) central field loss. Conclusion. Height of the chiasm and height of the tumour can be used to predict extent of central visual impairment.