ABSTRACT
Normal tension glaucoma (NTG) may be defined as a subcategory of primary open-angle glaucoma. However, disagreement exists as to whether it should be regarded as a separate disease entity from its higher tension counterpart. Although there is no consensus on a precise definition, the following criteria are in general use:
• IOP<21 mmHg; • open drainage angle; • optic disc and visual field changes characteristic of glaucoma; • the absence of a secondary cause of glaucoma.
