The worldwide prevalence of glaucoma is increasing

Early diagnosis of glaucoma is essential to prevent irreversible visual impairment, according to a Seminar in this week's issue of The Lancet.

Glaucoma is a group of disorders that progressively damage the optic nerve in the eye and without treatment can cause visual disability and eventual blindness. Glaucoma affects more than 66 million people worldwide and is the second leading cause of blindness. In the USA, health costs from glaucoma-related blindness have been estimated to be in excess of US $1.5billion a year, and the magnitude of the problem will increase as the population ages.

Robert N. Weinreb from the University of California San Diego, USA, and Peng Tee Khaw from the Moorfields Eye Hospital and Institute of Ophthalmology, London, UK, address primary open-angle glaucoma, an age-related and insidious form of the disease.

Loss of vision from glaucoma can be limited by currently available therapies if the disease is identified in its early stages. However, most cases are not discovered until vision has already been permanently affected, because clinical signs of early glaucoma may be subtle, even to an eye specialist. Although the risk of developing glaucoma increases substantially with the level of pressure in the eye and increasing age, the authors note that measurement of this pressure alone is not an effective method for diagnosis. Assessments of the optic disc, retinal nerve fibre layer, and visual function provide complementary information and new imaging and psychophysical tests can improve both detection and monitoring of the progression of the disease.

Weinreb and Khaw conclude that examination of the optic nerve is an essential component of the adult eye assessment and is the most effective way to identify individuals with glaucoma. The authors stress "the importance of early diagnosis to initiate pressure-lowering treatment and early detection of progression to advance this treatment."