Sir,

We have read the article with the title ‘Surgical outcomes of intermittent exotropia associated with concomitant hypertropia including simulated superior oblique palsy after horizontal muscles surgery only’ by YA Cho and S-H Kim.

We have a few questions about the article.

The Bielschowsky test is one of the adaptation tests to get rid of diplopia because of superior oblique paralysis. According to the Bielschowsky head tilt test, it is known that hyperdeviation increases when the head deviates towards the side of SO paralysis and hyperdeviation decreases or disappears when the head deviates towards the other side of SO paralysis. Therefore, hyperdeviation should be the highest when the head deviates towards the side of SO paralysis, the least when the head deviates towards the other side of SO paralysis, and in between in primary position. It was written in this article that the mean amount of hypertropia was 3.5–1.60 (2–14) PD in primary position, average hypertropia on the hypertropic side was 8.8–4.63 (3–18) PD, and on the nonhyperdeviating side 4.0–4.77 (0–16) PD. How do the authors explain that mean hyperdeviation in primary position is lower than the deviation on the nonparalytic side?

According to our experience, we also observed that hyperdeviation disappears when exodeviation is corrected surgically, as written in this article. But in some of our cases without fusion and with low visual acuity, the deviation recurred a few years after the operation. On the other hand, both horizontal and vertical deviations were controlled with strong fusional convergences in some of our patients.

What were the sensory states of the patients in this article who were tested with Titmus Fly stereotest, Randot stereotest, etc. as mentioned in the Materials and methods section? Have the authors observed any effect of fusional status on the correction of deviation for long-term results? Therefore, can the disappearance of vertical deviation spontaneously after correction of horizontal deviation only be explained by an anatomical or mechanical point of view?