New perspectives on glaucoma screening.

Glaucoma is defined as elevated intraocular pressure resulting in visual field defects. Elevated intraocular pressure without visual field defects is referred to as ocular hypertension. The prevalence of open-angle glaucoma in the population above the age of 40 years is less than one percent. Approximately one out of ten people with elevated ocular pressure has glaucoma. The concept of variable sensitivity explains why high ocular pressures do not always result in glaucoma. Glaucoma screening by tonometry can be justified only if used in conjunction with visual field testing.