Sir,

We appreciate the authors’ interest in our article. We’re pleased to hear that a disposable ruler could be a possible alternative to depth measurers made of PMMA. It would be useful to see validation of the measurements taken with this disposable ruler, by interobserver and intraobserver reliability data. Confirming repeatability and reproducibility of the measurements with each device is essential, before recommending the device as an accurate alternative.

One advantage of PMMA fornix depth measurers1, 2 is that they are rigid, therefore reproducibility and repeatability are high. With a flexible plastic ruler, reliably measuring upper fornix depth may be less easy, as one wonders if the ruler may bend to a variable degree over the globe and under the eyelid, potentially giving slightly different measurements depending on the technique and the user.