Sir,

We read with interest the recent article by Jutley et al1 describing a method of objective assessment of conjunctival fornix depth using a custom-made re-usable instrument created by the authors.

We agree wholeheartedly with the authors regarding the value of measuring the fornix depth in cases of cicatrising eye disease, both for assessing the degree of scarring and measuring progression in order to optimize management. Measurements compared to ethnically equivalent normal values (as described in this study) could also facilitate the diagnosis of giant fornix syndrome.2

We note that the results with this study’s custom device are comparable to previous studies using different devices, and that the authors feel that the type of device used is less important than the familiarity of the user with the technique.

We suggest an alternative measuring technique using a piece of equipment that is already readily available, cheap and disposable: Medline’s 6′′/15 cm flexible plastic ruler that accompanies surgical skin markers in sterile, single-use packs. We advocate instilling local anaesthetic and trimming the ruler at the 0 mm gradation and alongside the length markings before guiding the device into the centre of the apex of the fornix (Figure 1), with the patient in down-gaze for the superior fornix and up-gaze for the inferior fornix, as per the methods described in the authors’ study. The flexible nature of the ruler ensures it conforms to the curvature of the globe, providing comfortable, safe and accurate measurement.

Figure 1
figure 1

Superior fornix measurement using sterile flexible plastic ruler.

The patient in Figure 1 has symptoms and signs consistent with giant fornix syndrome affecting his left eye. The image demonstrates that the superior fornix is 4 mm deeper on the left side compared with the right side, confirming the diagnosis.

Speed of reading is discussed in the study, with 2 mm gradations embedded within the authors’ custom device with red marks at 10 and 20 mm. Similarly, this ruler is quick to read, with individual marks at each millimetre and longer marks at each 5 and 10 mm increment.

In summary, we propose that the fornix can be accurately and safely measured using an inexpensive, easily available, convenient, sterile, and disposable device.