To the Editor.
—Given their widespread use, it is important to elucidate the possible side effects of medications used in the treatment of glaucoma. The study by Coleman et al in the September 1990 issue of the Archives1 does not reveal any evidence that topical timolol maleate decreases plasma HDL cholesterol levels.This study fails to adhere to the two basic tenets of a clinical trial: randomization of a treatment and control group, and masking the subjects and observers.2 While it is not possible to follow these criteria in every trial, certainly they are the minimum that should be met in a study that was designed to determine if topical timolol changes plasma lipid levels, which can be influenced by external factors such as diet, exercise, and inadvertent counseling by investigators. We agree with Coleman et al that some subjects may consciously or unconsciously modify their diet or
Shaw BR, Weinreb RN. Topical Timolol and Serum Lipoproteins. Arch Ophthalmol. 1991;109(10):1341-1342. doi:10.1001/archopht.1991.01080100021005