The function and testing of the superior oblique muscle
EDITOR- It was with a considerable sense of déjà vu that I read and
enjoyed the article "a case of mistaken muscles" (BMJ 20th April 2002 page
962) by two Oxford Medical students. Amongst students and teaching staff
in our department at the other place we have argued this amongst ourselves
on numerous occasions.
Our final conclusions, and what is now our policy for instruction on
this muscle, is as follows: The superior oblique, acting in isolation,
turns the eye down and out. However, if was tested clinically by asking
the patient to look down and out its action could be mimicked by the
combined action of inferior and lateral recti. This is particularly so as
the inferior rectus acts most effectively when the eye is abducted
(looking laterally). Therefore by asking the patient to look down and in
these muscles are excluded and the problem is solved. Essentially we are
testing the ability of the superior oblique to look downwards.
The confusion, which I hope the above clarifies, is compounded by
some ophthalmologists to whom I have spoken, being so used to testing the
muscle by asking the patient to look down and in, that they have forgotten
that the isolated action is down and out.
Competing interests: No competing interests