|Year : 1970 | Volume
| Issue : 1 | Page : 10-14
Morphological studies of extraocular muscles in cases of microcornea
K Nath, R Gogi, BS Goel
Muslim University Institute of Ophthalmology, Aligarh, India
Muslim University Institute of Ophthalmology, Aligarh
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Nath K, Gogi R, Goel B S. Morphological studies of extraocular muscles in cases of microcornea. Indian J Ophthalmol 1970;18:10-4
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Nath K, Gogi R, Goel B S. Morphological studies of extraocular muscles in cases of microcornea. Indian J Ophthalmol [serial online] 1970 [cited 2021 Feb 27];18:10-4. Available from: https://www.ijo.in/text.asp?1970/18/1/10/35052
Association of congenital cataract, coloboma of iris and choroid and increase in intra-ocular tension, with microcornea are well known. Presence of abnormal insertion of various recti in such cases was discussed by Nath and Gogi  in four eyes of two cases of microcornea. It was observed that the distance between the limbus and the centre of insertion of the medial rectus was found uniformly increased in both the eyes of a boy and his sister. The distance between the limbus and the centre of insertion of inferior recti was decreased in one. The values for superior recti were decreased in two eyes, increased in one and was normal in the fourth.
A further study on eight eyes has further elucidated the morphological trends of the muscles and hence necessitated the publication of results and trends observed in all the twelve eyes of six subjects in two families. An attempt has been made to explain this variation on the basis of developmental defect.
The four cases examined were:
CASE I: [Figure - 1] H. A., male, aged 40 years who came to the out-patient department of the Gandhi Eye Hospital, Aligarh, on 12th February '68, with complaints of defective vision in both eyes and small eyes since birth.
CASE 2: S. B., female, aged 2 years, the youngest child of case 1. She was brought with the complaints of involuntary movements of both eyes for the last one year.
She had cataracts and glaucoma for which curette evacuation with iridoencleisis were planned for both eyes in separate sittings.
CASE 3: S. U., a male child, aged 7 years, the second son of case 1, was brought with the complaints of low vision and involuntary movements in both eyes since childhood.
He too had cataracts and squint, for which curette evacuation and cosmetic correction of squint in separate sittings were proposed.
CASE 4: S. M., a ten years old male child, the eldest son of case 1, was having low vision since childhood. [Figure - 2]
Curette evacuation of the lamellar cataracts and cosmetic correction of squint were planned for both the eyes.
Detailed history of the family was enquired into. There was history of small size of the eye in the mother and the elder sister of Case 1, the latter was also examined subsequently. None of his step brothers or the sisters had any such trouble in the eye. One of them was checked and examined. Patient had two sons and one daughter and all of them were found to be cases of microcornea with congenital cataract. All these children are reported in this publication.
The clinical findings of the four cases are tabulated in [Table - 1], which affords comparison between them. To study the morphology of extraocular muscles, each muscle was exposed at its insertion. Breadth of the tendon of all the recti at their insertions and distance between the centre of the tendon and the limbus were measured with a pair of callipers in both the eyes.
Besides the points of comparison shown in the table below all the cases showed the following similar features.
All of them had
(a) Horizontal nystagmus.
(b) Corneas smaller than normal. The respective measurements are given in [Table - 2].
(c) Shallow anterior chambers.
(d) Lack of lustre in the iris, which appeared thickened, with smooth surface and absence of pattern.
(e) Sluggish reaction to light and accomodation.
(f) Lamellar type of cataracts in both eyes.
(g) Ocular movements restricted.
(h) No other ocular or general congenital anomaly was present.
As regards treatment, the problems presented were those of lamellar cataract in all the eyes, glaucoma in case 2, and squint in cases 1, 3 and 4. Separate operative procedures were planned for the conditions simultaneously present.
Observations and Comments
In the absence of local normal standard values of the width of the tendons and the distance between the centre of insertion of the recti and limbus, they have been compared with the normal standard international values as is shown in [Table - 1].[Table - 2], wherein the studies on previous four eyes of microcornea have also been included (Nath and Gogi)  . A deviation of less than 1.0 mm in the width from the normal has been excluded as of no significance.
[Table - 2] shows that out of forty eight recti the breadth of the tendons of all the recti is significantly decreased except in the case of seven lateral recti, three medial recti and two inferior recti and one superior rectus.
Considering all the forty eight recti, the limbus muscle distance was decreased in twenty six (54.1%), increased in thirteen (27.0%) and unchanged (normal) in nine (18.9%) recti. No significance was given to a variation of less than 0.5 mm. The maximum decrease is evident in superior rectus (nine eyes), closely followed by lateral rectus (seven eyes) and inferior rectus (six eyes). The least decrease in the limbus to muscle distance is seen in the case of the medial rectus (four eyes).
During the early developmental stage, the extraocular muscles are inserted into the sclera and the limbus is at first situated farther back over the ciliary body but it shifts forward gradually (Last)  as the mesoderm around the anterior edge of the optic cup consolidates. Underdevelopment of the mesoderm in the region of ciliary ring will result in microcornea (Nath, Nema and Shukia)  and decrease in the distance between the limbus and insertion of the muscles (Mann)  . Out of forty eight muscles (in twelve eyes) examined in the present study, only twenty six muscles (54.1%) are anteriorly inserted.
If we consider the failure of expansion of ciliary ring alone to be responsible for the narrow circumference of limbus and anterior part of sclera, it is not possible to explain the normal or posterior placement of the recti. On the other hand it is suggestive of an unequal and independent development of the limbus and anterior part of sclera, which in itself may be anomalous and variable resulting into an increase or decrease of the distance between the limbus and muscles simultaneously. The other causes may be in the normal variation of the insertion of the muscles or their defective post natal. consolidation due to low vision leading to lack of functional training.
Decrease n the width of tendons of recti is suggestive of weak muscles in cases of microcornea and muscular imbalance.
| Summary|| |
- Morphology in forty eight recti muscles in twelve eyes of microcornea has been studied.
- Distance between the recti and the limbus, as compared to normal, was decreased in 26, increased in 13 and was normal in 9 muscles.
- Mode of development of this variation has been discussed. Failure of expansion of the ciliary ring appears independent of the development of the anteria selera.
| References|| |
Last, R. J.: Eugene Wolf's anatomy of the eye and orbit, p. 414. H. K. Lewis & Co. Ltd., London (1961).
Mann, 1. : Developmental abnormalities of the eyes p. 353, J. B. Lippincott Company, Philadelphia (1957).
NATH, K.; and GOGI, R.: Morphological studies of extraocular muscles in cases of micro and megalocornea. Proc. All Ind. Ophth. Soc., (1967).
NATH, K.; NEMA, H. V.; and SIIUKLA, B. R. : Histopathology in a case of unilateral microcornea plana. Acta Ophthalmologica 42, 609-613, (1964).
[Figure - 1], [Figure - 2]
[Table - 1], [Table - 2], [Table - 3]