Abstract
The available evidence suggests that the progression of visual field changes in chronic simple glaucoma is dependent on many complex factors. A raised intraocular pressure is certainly one of the factors involved but its effects will depend on many others, among which are the level of the systemicblood pressure, the degree of oxygenation of theblood, the length of time during which the "normative" intraocular pressure for the particular eye is overstepped, and probably many other effects which are as yet quite unknown. Most authors subscribe to the belief that the height of the intraocular pressure has an effect on the integrity of the visual function in chronic simple glaucoma but though the normal intraocular pressure is statistically ascertainable the "normative" pressure will vary in the individual eye according to the factors enumerated. It has also been stated that if the intraocular pressure can be maintained consistently below 20 mm Hg