We thank Dr Razeghinejad for his interest in our article on 3-year follow-up of the Tube Versus Trabeculectomy Study. The study found a progressive increase in the use of glaucoma medications by the trabeculectomy group during the first 3 years of follow-up, whereas medical therapy remained relatively stable in the tube group. The mean number of glaucoma medications was significantly greater in the tube group compared with the trabeculectomy group at 1 year, but no significant difference in use of glaucoma medical therapy was observed between treatment groups at 3 years.

The number and class of each glaucoma medication were provided by the investigator at study visits. Fixed combination agents, including timolol-dorzolamide (Cosopt; Merck & Co., Inc., Whitehouse Station, New Jersey, USA) and brimonidine-timolol (Combigan; Allergan, Inc., Irvine, California, USA), consist of 2 glaucoma medications from separate classes. Therefore, we counted these combination agents as 2 medications, as recommended by Drs Razeghinejad and Metclaf. It is known that different classes of glaucoma medications, and even agents within a class, vary in their effectiveness in reducing intraocular pressure. We did not attempt to weight glaucoma medications based on relative efficacy, but rather reported the actual number of medications used. Oral carbonic anhydrase inhibitors such as acetazolamide (Diamox; Duramed Pharmaceuticals, Inc., Pomona, New York, USA) were counted as only 1 medication. It is noteworthy that 14 patients in the tube group and 16 patients in the trabeculectomy were using an oral carbonic anhydrase at baseline, and only 3 patients in each treatment group were using these medications at the 3-year follow-up visit. The number of glaucoma medications (mean ± standard deviation) was 1.3 ± 1.4 in the tube group and 1.1 ± 1.7 in the trabeculectomy group ( P = .44, t test) when oral carbonic anhydrase inhibitors were assigned a value of 2 medications, and the study results did not change significantly.

We appreciate the letter from Dr Razeghinejad which has provided us with an opportunity to clarify the reporting of supplemental glaucoma medical therapy in the Tube Versus Trabeculectomy Study.