|Year : 1981 | Volume
| Issue : 4 | Page : 381-383
Limbal insertion distance and width of the Horizontal recti tendon in cases of concomitant squint
JN Rohatgi, BK Prasad, HK Singh, Alok Kumar
Deptt. of Ophthalmology, Patna Medical College, Patna, India
J N Rohatgi
Deptt. of Ophthalmology, Patna Medical College, Patna
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Rohatgi J N, Prasad B K, Singh H K, Kumar A. Limbal insertion distance and width of the Horizontal recti tendon in cases of concomitant squint. Indian J Ophthalmol 1981;29:381-3
|How to cite this URL:|
Rohatgi J N, Prasad B K, Singh H K, Kumar A. Limbal insertion distance and width of the Horizontal recti tendon in cases of concomitant squint. Indian J Ophthalmol [serial online] 1981 [cited 2020 May 30];29:381-3. Available from: http://www.ijo.in/text.asp?1981/29/4/381/30936
In the etiology of esotropia or exotropia four group of factors are implicated; innervational, accommodative, paretic and anatomical or mechanical. What is their respective role and in what combinations do they play their role, is nowhere clearly defined except for the mention that of these, the innervational and accommodational factors together or alone play a more significant role in the causation of these squints.
Very little is understood of the anatomical or mechanical factors which may be (1) The limbal insertion distance of the medical rectus (MR) and the lateral rectus (LR) is more or less the standard figure of 5.5 mm and 6.9 mm respectively, (2) The width of these tendinous insertions is normal width-10.3 mm (MR) and 8.8 mm (LR), (3) The check ligaments of MR and LR are unusually thick and have some anomalous character, (4) Existence of abnormal muscle slip or unusual attachment of muscle.
All of us who have operated on these two recti have felt at one time or the other, that despite recession or resection of equal length in millimetre, in same age group of children, with similar history of onset and duration; the deviation corrected in degrees is not exactly the same. Obviously some factors or factor do play a significant part in causing this difference.
| Materials and methods|| |
With this end in view, it was thought that the two factors (i) limbal-insertion distance and (2) the width of the tendon of MR and LR be examined and measured in a series of one hundred concomitant convergent and divergent squint cases. These also included cases of alternating eso and exotropia. Such children were of the following age group at the time of surgery.
3- 5 years= 10 cases
6-15 years=60 cases
I1-15 years=30 cases
The age at onset of deviation as per history was from birth to five years-and thus the treatment was sought from a couple of years to eight or ten years after the onset of deviation.
There were more cases of esotropia (65) than exotropia (35 cases).
The measurements were taken at the operation table and under general anaesthesia.
(a) Limbal-insertion distance
After the muscle M R or LR was cut at its insertion and the insertion area cleaned-one arm of the measuring caliper was placed at the base of the insertion of the muscle and the=: distance to the limbus measured on a line perpendicular to the insertion.
(b) Width : After cleaning the linear insertion of MR and LR-the caliper was used to measure the linear distance from one end to the other end of the insertion line.
Both the measurements were taken by two observers and a Vernier scale was used to note down the measurements up to the second decimal place of a mm. The mean of the two measurements by two observers was taken as the correct measurement.
These cases could be further grouped according to size of deviation into small and large angle deviation. Small-angle-deviation were those in whom the angle of deviation was less than 20 degrees and those with angle of deviation 20 degrees or more were taken as largeangle deviation. The cases with alternating eso or extropia had generally a larger angle of deviation.
| Discussion|| |
Scobee asserted that 90 percent of all cases of heterotropia have some underlying anatomical basis. Goldstein from his study of the MR and LR muscle-Limbal-insertion distance in a total of 64 patients concluded that the limbal-insertion distance of the medial rectus muscle was significantly smaller in patients with esotropia compared to those with exotropia. On the other hand he found no significant difference in the lateral rectus muscle measurements both in esotropia and exotropia.
In a series of 100 cases of concomitant squint with such measurements, our findings have also been more or less similar viz-the medial rectus muscle was significantly closer to the limbus (5.00 mm) than the normal figure of 5.50 mm in cases of concomitant convergent squint, whereas with lateral rectus-the limbal insertion distance both in esotropia and exotropia was not significantly different from the normal figure of 6.90 mm
How far this anatomical finding has played a part in the causation of esotropia is rather difficult to say. May be other eliological factors like accommodational and innervational have tended to superimpose themselves on this basic anatomical difference. And that may also explain the varying response of recession and resection or buckling in those cases where even the correction was to the same extent in millimetre.
So far the second hypothesis of width of tendinous insertion of MR and LR is concerned-the presumption that a wider than normal insertion of the MR muscle in the sclera would lead to esotropia and a wider insertion of LR muscle would cause exotropia have not been borne out in our series-consistently and significantly. In a couple of cases, however, of both esotroipa and exotropia-a figure of 11 mm for MR tendinous insertion and 9.50 to 9.70 mm for LR tendinous insertion have been found respectively. These figures are significant no doubt but as pointed out these figures are only for a couple of cases and not the consistent findings in other cases. No reference is available on this aspect of the MR & LR insertion.
Thus at surgery when these recti (MR & LR) are being exposed for recession, resection or buckling, it is desirable that a consideration of tendinous width be kept in mind at least for locating any abnormal muscular slip or facial sheath, removal of which is important for a full correction of the deviation.
| References|| |
Scobee, R.G., 1952, -The oculorotary muscles, St. Louis 6. V. Mosby.
Goldstein, J. H., 1969, Amer, J. Ophthalmol 68,: 695.
[Table - 1], [Table - 2], [Table - 3]