|Year : 1983 | Volume
| Issue : 1 | Page : 21-22
Abnormal insertion of inferior oblique
Prem Prakash, BK Nayak, V Menon
Dr. R.P. Centre for Ophthalmic Sciences, A.I.I.M.S, New Delhi, India
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, AIIMS New Delhi
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Prakash P, Nayak B K, Menon V. Abnormal insertion of inferior oblique. Indian J Ophthalmol 1983;31:21-2
Slight abnormalities of the extrinsic ocular muscle are not rare. They are due to developmental errors in cleavage as the muscle differentiates from the common embryologic mesoblastic tissue. The insertion of the inferior oblique, though variable, is more uniform than that of the superior oblique. The variation consists chiefly in the degree of obliquity and convexity of the curves. The insertion often shows gross irregularities such as angular serrations or dehiscerces. Even an absence of the scleral insertion of the inferior oblique which shared a common tendon of attachment with the overlying lateral rectus muscle has been noted. A case of an unusual abnormal insertion of the inferior oblique muscle is reported.
| Case report|| |
A 6 years old female child having alternating divergent squint was admitted for squint surgery. On examination there was 45° extropia for distance and 50° Extropia for near without any associated `A' or `V' phenomenon. There was no underaction or overaction of any muscle including the inferior oblique. Vision in B/E was 6/6 with normal anterior segment and fundus. Systemic examination revealed no abnormality. While dissecting the lateral rectus muscle, a fleshy mass was noted at the superior border of lateral rectus muscle.
On further dissection it was realized that the fleshy mass was a part of the inferior oblique muscle, getting inserted 5 mm above the upperborder of the lateral rectus. The anterior end of the insertion was 10 mm [Figure - 1][Figure - 2][Figure - 3] behind the insertion of lateral rectus muscle. However, no other abnormal slip of muscle was noted.
| Discussion|| |
An abnormal insertion of the extrinsic muscles of the eye is a frequent cause of minor deviations associated with or without clinical symptoms. Variations in insertions are a common cause of muscular imbalance evident clinically as a heterophoria or may develop later into a frank strabismus, while a more marked degree of the same condition will produce a limitation of movement.
The extrinsic ocular muscles in man are developed essentially as condensation in the paraxial mosoderm surrounding in optic vesiele. From the ventrocaudal portion of the premandibular condensation, at 8.5 mm stage there arises a process which later develops into medial rectus, inferior rectus and inferior oblique muscles. By 12.5 mm, the inferior rectus and inferior oblique are entirely separated and from the point of junction with inferior rectus the inferior oblique grows in two directions. The cranioventrally directed extremity reaches its point of attachment to the orbital surface of maxilla and the caudodorsal extremity is inserted adjacent and medial to the insertion of the lateral rectus. Later the insertion of inferior oblique shifts backwards to its normal position.
Normally the insertion of inferior oblique is situated under cover of inferior border of lateral rectus muscle, the anterior most end being 2.2 mm underneath the lateral rectus muscle and 9.00 mm behind the insertion of lateral rectus muscle. In this case it was traversing the whole width of lateral rectus and getting attached 5 mm superior to the superior border of lateral rectus muscle. This shift may be due to excessive shift of insertion during the developmental process. Such an abnormal insertion of the inferior oblique is prone to get injured while operating as the lateral rectus especially on cutting the inter muscular membrane at the upper border of the lateral rectus. Surprisingly no abnormal function of the muscle was associated with this anamoly.
| Summary|| |
An unusual case of an abnormal oblique muscle above the upper border of the lateral rectus is described.
| References|| |
Banerjee, 1950 Brit. J. Ophthalmol. 34, 756.
Fink, W.H. 1962, Surgery of the vertical Muscles of eye P. 195 2nd ED, Charles C, Thomas Springfield U.S.A.
Fink, W.H. 1958, Strabismus ophthalmic symposium II P. 20 ED James H. Alten st. Louis, The C.V. Mosby company.
Duke Elder, S; 1974, System of Ophthalmolcgy Vol III Part 2, P. 979, edited Duke Elder Henry Kimpton London.
[Figure - 1], [Figure - 2], [Figure - 3]