|Year : 1978 | Volume
| Issue : 2 | Page : 25-28
The third eyelid in the albino rats (A histological study)
KK Bisaria1, Shanno Devi Bisaria2
1 Department of Anatomy, King George's Medical College, Lucknow, India
2 Dept. of Ophthalmology Vivekananda Polyclinic, Lucknow, India
K K Bisaria
Department of Anatomy, King George's Medical College, Lucknow
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Bisaria K K, Bisaria SD. The third eyelid in the albino rats (A histological study). Indian J Ophthalmol 1978;26:25-8
The third eyelid or the nictitating membrane of the albino rats is sparingly described in the literature. Wolf commented that it is best developed in mammals especially in herbivore. In man it is present in a rudimentary form known as semilunar fold. It has in many mammals a plate of hyaline cartilage but in man more especially in the dark races only vestige of this cartilage is observed. Low and Anelli described that in lower forms like Rodentia it is most rudimentary.
The present work is undertaken with the view that in rodent there has been lot of discrepancies in the description of structure of the third eyelid in the past.
| Materials & Methods|| |
In all 20 adult albino rats of either sexes were taken for this study. They were sacrificed under deep ether anaesthesia by cutting the carotid arteries. The eyeballs with both the external eyelids in the form of rectangular pieces were dissected and were kept in Bouin's fluid for 24 hours. These specimens were then washed in running water and the anterior half of the eyeball with eyelids were cut coronally by the sharp knife. These were then subjected to graded alcohols for dehydration and paraffin blocks were prepared. Sections were cut sagittally at 5 microns thickness with Spencer microtome and were stained with haematoxylin and Von-Gieson methods.
| Observations|| |
In 8 eyeballs out of total of 40, the third eyelids were wedge shaped with broad base [Figure - 1]. The surface epithelium was stratified and deeper rows were made up of cuboidal cells. The basis of the whole structure was cellular parenchyma. Out of 8 of these eyeballs in 6 the goblet cells were absent in the conjunctiva but in the rest 2 a few goblets cells were observed. In 6 eyeballs out of 40, the third eyelids were large in size but did not show the cartilagenous tissue at all [Figure - 2]. In 12 eyeballs out of 40, the third eyelids were quite large in size and they were reinforced by a plate of hyaline cartilage [Figure - 3]. In 4 eyeballs out of 40, the third eyelids were somewhat cylindrical in shape with expanded distal edge [Figure - 5]. In 8 eyeballs out of 40, the third eyelids were cylindrical in outline with the distal and proximal ends measuring nearly equally [Figure - 6]. The surface epithelium in all these showed number of collections of goblet cells [Figure - 7]. There was no trace of hyaline cartilagenous plate. In 2 eyeballs of a rat the free edge of the lid was bifid [Figure - 8].
| Discussion|| |
The third eyelid in placentals is rudimentary but occasionally as in the bear and rhinoceros, it covers the cornea when the animal sleeps. The specific musculature is lacking although it is present in lower vertebrates. The basis of third eyelid is hyaline cartilage in most of placentals (horse, ox, dog, pig, goat, cat, hare etc.). Naglieri commented that in rabbits the basis is mere cellular parenchymatous tissue but Prince et a] stated that in the same rodent there is a long slender cartilage nous shaft. They also stated that there are numerous goblet cells in the conjunctiva. The present study on a smaller rode _t, the albino rats has revealed that there is marked variations in the size shape and constitution of the third eyelid. Some were having a sharp free edge and others a blunt edge. The basis of third eyelid in some rats was of hyaline cartilage and in others only cellular parenchyma. It appears from the study that the presence of hyaline cartilagenous plate was not an essential feature even though the size of the third eyelid may be significantly large. The presence of goblet cells in the covering conjunctiva was also not a constant feature in all the rats. A small bifid eyelid has been an interesting finding.
| Summary|| |
A histological study on the third eyelid or nictitating membrane of albino rats has been carried out. There were marked variations in size, shape and the structure of this eyelid. A rare finding of a bifid third eyelid is reported.
| Acknowledgement|| |
I am indebted to late Prof. D. Narayan, M.S., F.A.M.S., for his able guidance in the examination of microslides.
| References|| |
Anelli, D., 1935, Boll, occul.,
Low, 1905, Ophthal. Rec.,
14,431 quoted by Duke-Elder, 1958, System of Ophthalmology,
1,492. Henry Kimpton, London.
Naglieri, 1932, Monit. Zool. Ital.,
43,17 quoted by Duke-Elder 1958 The eye in evolution.,
492, Henry Kimpton, London.
Prince, J. H., Diesem, C. D., Eglitis, I, and Ruskell, G.L., 1960, Anatomy and histology of the eye and orbit in domestic animal,
280. Charles C. Thomas, Springfield, Illions, U.S.A.
Wolff, E., 1958, The Anatomy of the eye and orbit,
457, Henry Kimpton, London.
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7], [Figure - 8]