Abstract

The superior oblique (SO) insertion is the most variable of the extraocular muscles, rendering surgery difficult and unpredictable. This study aims to improve the ability of surgeons to identify and operate successfully on the SO, by characterising the variability in the size, position, angle and shape of its insertion. A secondary aim was to define clinical guidelines for steroid injections into the trochlear area to treat SO pathology. Dissection was performed on eight paired cadaveric orbits. Donors had provided written consent before decease for the use of their bodies for anatomical research in compliance with the Human Tissue Act 2004. Morphological measurements of the SO and its insertion were made, with scale diagrams constructed based on these measurements. Accessory insertions were present in both eyes from one donor. While multiple insertions are common for the inferior oblique, this has not previously been reported for the SO. Regarding trochlear injections, the medial canthus was thought to provide a good surface landmark. To test this hypothesis, multiple injections were made in each specimen and the position of the injection site relative to the medial canthus was measured. This confirmed the suitability of the medial canthus as a good landmark for trochlear injection.