Sir,

We congratulate Mariotti et al1 for their very interesting article ‘Long-term outcomes and risk factors for failure with the EX-press glaucoma drainage device’ in which they report the long-term outcomes and risk factors for failure with the EX-PRESS shunt implanted under a scleral flap.

We would like to point out some issues that we believe need further clarification.

First, in their article the authors report that ‘Two hundred and forty-eight eyes of 211 patients with uncontrolled glaucoma underwent EX-PRESS implantation (with or without cataract extraction) between September 2000 and September 2009’; however, it is not clear whether the authors excluded patients who had previously undergone cataract surgery and intraocular lens (IOL) implantation? More importantly, did they exclude patients with complicated cataract surgery?

Second, in the 112 eyes that underwent combined surgery, what was the exact technique?

Did they perform the cataract surgery and then the modified trabeculectomy with the EX-PRESS valve or vice versa? Was the cataract surgery in all the eyes uncomplicated? And if not, did they continue the procedure of the EX-PRESS implantation? Did the authors have any cases where an anterior chamber IOL (ACIOL) or an Artisan type had to be inserted? It would be very interesting to know whether the EX-PRESS valve works efficiently in the eyes with complicated cataract surgery and whether the EX-PRESS success rates are different in these eyes.