We congratulate Mezad-Koursh et al1 for their article published in the January 2020 issue. The authors used ultrasound biomicroscopy to image a large number of extraocular muscles in primary surgeries and reoperations. However, this was not the first study using the bag/balloon technique. We used the ClearsScan (ClearScan Ultrasound Cover CS200, ESI Inc) technique for imaging horizontal extraocular muscles.2
It is important to understand that even with wide field ultrasound biomicroscopy, the cup limits the field of the oscillating probe, which is overcome by using a bag/balloon. As Mezad-Koursh et al state, for patients with strabismus, the limbus must be visualized in the same view as the muscle insertion. Thus, even if the wide field of the ultrasound biomicroscopy goes up to 14 mm, it is pointless if the limbus is not visualized in the same scan. The greatest advantage of the bag/balloon technique is patient comfort. It ensures patient cooperation and ease in moving the probe directly over the conjunctiva without the need for the cup. Hence, we can capture increasing distances from the limbus in the same scan.
Second, Mezad-Koursh et al performed postoperative ultrasound biomicroscopy as long as 365 days after strabismus surgery. The longer the time after surgery, the higher the chances of pseudotendon, stretched scar, or muscle creep. The fact that previously operated muscles have more standard deviations in the ultrasound biomicroscopy measurements needs to be re-stressed. The advantage of the newest generation anterior segment optical coherence tomography machines in comparison to ultrasound biomicroscopy should not be underestimated.
Savleen Kaur, MD
Jaspreet Sukhija, MD
Editor's Note: The authors declined to comment on this letter.
- Mezad-Koursh D, Rosenblatt A, Cohen S, et al. Accuracy of the ultrasound biomicroscopy bag/balloon technique in locating horizontal extraocular muscle insertions before and after strabismus surgery. J Pediatr Ophthalmol Strabismus. 2020;57(1):12–20. doi:10.3928/01913913-20191115-01 [CrossRef]
- Sukhija J, Kaur S. Comparison of plication and resection in large-angle exotropia. J AAPOS. 2018;22(5):348–351. doi:10.1016/j.jaapos.2018.05.017 [CrossRef]