Fifty-nine low-tension glaucoma patients were reviewed with respect to asymmetry of intraocular pressure (IOP) and visual field defects. In the presence of unequal IOP the visual field damage is almost always greater on the side with higher mean IOP. However, only 13 of 47 patients with asymmetric visual field defects had a mean IOP difference between the two eyes of greater than or equal to 1 mmHg. Although in the case of IOP asymmetry visual field damage is greater in the eye with higher mean IOP, other factors must also play an important role in the development of visual field defects in low-tension glaucoma.