Evidence at last that treatment works

Two important randomised controlled trials—one from the United States, the other from Sweden—were published last year in the Archives of Ophthalmology, and their findings were a cause for celebration for ophthalmologists and subspecialists in glaucoma. 1 2 Intraocular pressure has traditionally been lowered pharmacologically or surgically in an attempt to prevent the disease destroying sight long before randomised controlled trials were conceived. The rationale was based on indirect evidence. However persuasive this might have been, it did not protect against lingering doubts caused by observing patients progress relentlessly towards blindness despite apparently successful control of intraocular pressure or the fact that a substantial proportion of people with glaucoma have pressure that is always within the normal range. Some even proposed that raised pressure was effect not cause—a failure of autoregulation because of interruption of biofeedback.

These doubts hindered advocates of population screening because evidence of effectiveness of treatment, a fundamental requirement, was not there. Eddy, in examining the economics of population screening in the United States, was one of the first to draw our attention to these deficiencies.3 For a while we were locked into an ethical dilemma. Evidence was lacking that lowering pressure was effective, yet it …