Evaluation of Ahmed glaucoma valve implantation through a needle-generated scleral tunnel in Mexican children with glaucoma.

Dear Editor,

We have read the whole article with great interest. We would like to congratulate Albis-Donado et al.[1] for such a large series of cases evaluating success rate of Ahmed glaucoma valve (AGV) in refractory cases of glaucoma very sincerely. We have few comments to make on the study and those are as follows:

There had been changes in the technique of AGV implantation over a period of time (e.g. making scleral flap for the tunnel of entry or direct entry with needle), the success rate would be biased by the technique variations as described in your study.

Those cases which were not included in the study because of short follow-up period could add to failure rates in your case series. So it is difficult to draw a conclusion from the success rates in three different categories shown in the study.

In the case which underwent endophthalmitis, you have described the site of infection as the previous site of surgery and not the intervention site done for AGV. If the eye was quite before AGV intervention, it is difficult to determine the site of infection.[2]

There are no definite data on failure rates because of fibrosis or bleb failures of previous surgeries done.

There is no control group to show the comparison of your technique and its success rate. There may be bias based on cases selection in your series.

Preoperative data previous to first surgery on the eye could matter a lot to decide how beneficial was the first surgery to achieve target pressure and how long it served the purpose. Considering complete success group, e.g., even you have achieved a pressure of 20 mm Hg, it may not serve the purpose if the previous target pressure was 15 mm Hg. So, the higher IOP would have a role to play on optic nerve even though you have kept that eye in complete success group without medication.