Correspondence

The Medical Treatment of Open-Angle Glaucoma

N Engl J Med 1993; 329:735-736September 2, 1993

Article

To the Editor:

In his review of open-angle glaucoma (April 15 issue),1 Dr. Quigley concluded that “the available data from clinical studies suggest that there is a significant reduction in the rate of initial injury when eyedrops are used to lower pressure.” We recently completed an overview of all published randomized controlled trials of the medical treatment of open-angle glaucoma,2 and we disagree with this conclusion. Although a large number of such trials (n=102) have been carried out, only a few (8 of 102) have focused on the question of medical treatment for glaucoma with an appropriate study design and the use of visual-field changes (as opposed to intraocular pressure) as an end point.

Indeed, pooling of the data from six placebo-controlled trials with a minimal follow-up of three months suggested a moderate but statistically significant reduction in mean intraocular pressure (-4.9; 95 percent confidence interval, -7.3 to -2.5)2. Data on the more clinically relevant end point of long-term visual-field changes were, however, available in only three randomized controlled trials, and statistical analysis of their combined data failed to provide convincing evidence of a beneficial effect of treatment (odds ratio, 0.75; 95 percent confidence interval, 0.42 to 1.35). Moreover, the exceedingly short follow-up in these trials (only 10 percent measured intraocular pressure for one year or more) does not allow the assessment of the still unclear relation between pressure reduction and progression of visual dysfunction. Taken together, the evidence from these trials indicates that medical treatment can indeed reduce intraocular pressure; however, the data are not informative with regard to the efficacy of treatment over the long term on a more clinically relevant end point.

Luca Rossetti, M.D.
University of Maryland, Baltimore, MD 21201

Nicola Orzalesi, M.D.
Ospedale S. Paolo, 20100 Milan, Italy

Alessandro Liberati, M.D.
Istituto Mario Negri, 20157 Milan, Italy

2 References

1. 1

   Quigley HA. Open-angle glaucoma. N Engl J Med 1993;328:1097-1106
   Full Text | Web of Science | Medline

2. 2

   Rossetti L, Marchetti I, Orzalesi N, Scorpiglione N, Torri V, Liberati A. Randomized clinical trials on medical treatment of glaucoma: are they appropriate to guide clinical practice? Arch Ophthalmol 1993;111:96-103
   Web of Science | Medline

Author/Editor Response

Dr. Quigley replies:

To the Editor: In their quotation from my article, Rossetti et al. omitted the following sentence: “The protective effect [of lowering the intraocular pressure] is not absolute, however, and not all trials show a significant effect.” Three clinical trials have been performed with visual-field testing as the outcome variable. In two, the incidence of initial field loss was reduced by 50 percent in the treated groups. The third study found no statistically significant result of treatment. Rossetti et al. found in their meta-analysis of these three studies1 that “overall, data suggest a 25 percent reduction in the occurrence of visual field changes.” I believe that my summary of these data is accurate and consistent with the level of detail that was possible in a brief review of the entire subject of glaucoma.

Rossetti et al. also fail to note my acknowledgment that “randomized clinical trials are in progress to answer these important questions.” This year, the National Eye Institute funded a multicenter clinical trial with more than 1500 patients to study the magnitude of the effect of lowering intraocular pressure on the incidence of initial visual-field loss in open-angle glaucoma. Those of us who will devote five to eight years to this study agree that we need to know more about the efficacy of glaucoma treatment.

Harry A. Quigley, M.D.
Wilmer Institute, Johns Hopkins University, Baltimore, MD 21205

1 References

1. 1

   Rossetti L, Marchetti I, Orzalesi N, Scorpiglione N, Torri V, Liberati A. Randomized clinical trials on medical treatment of glaucoma: are they appropriate to guide clinical practice? Arch Ophthalmol 1993;111:96-103
   Web of Science | Medline

Citing Articles (2)

Citing Articles

1. 1

   James F Kirwan, Christina Rennie, Jennifer R Evans, James F Kirwan. 2009. Beta radiation for glaucoma surgery. .
   CrossRef

2. 2

   Alessandro Liberati. (1995) “Meta-analysis: Statistical alchemy for the 21st century”: Discussion. A plea for a more balanced view of meta-analysis and systematic overviews of the effect of health care interventions. Journal of Clinical Epidemiology 48:1, 81-86
   CrossRef