I would like to congratulate the authors for this wonderful effort, which throws some light on some of the time trends in the therapeutic area. However, while interpreting long term observational studies, some of the potential sources of bias should be kept in mind. One such potential confounding factor, is the observation of the end- points for Latanoprost, in the two distinct time-periods. The results for both the end-points were somewhat different in these two time-periods. It was apparently superior in the period of 1997-2001, than in the period of 2002 onwards. This could be attributed to the availability of newer PG analogs in the period after 2002, which could be a confounding factor for treatment discontinuation or treatment change for latanoprost. Persistence itself is a surrogate end-point for the tolerability profile of the anti-glaucoma drugs. This surrogate end-point may be a subject of confounding factors, if measured in different time-periods, and hance, may give a false impression about the tolerability profile of different medications.

Conflict of Interest:

I am a medical advisor, working at Pfizer India. I declare that the response posted here is my personal opinion on the topic, and does not endorse the views of my institution.