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ARTICLES
Year : 1973  |  Volume : 21  |  Issue : 4  |  Page : 178-181

The lamina cribrosa in some mammals - (a histological study)


Department of Anatomy, King George's Medical College, Lucknow, India

Correspondence Address:
K K Bisaria
Department of Anatomy, King George's Medical College, Lucknow
India
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Source of Support: None, Conflict of Interest: None


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How to cite this article:
Bisaria K K, Narayan D. The lamina cribrosa in some mammals - (a histological study). Indian J Ophthalmol 1973;21:178-81

How to cite this URL:
Bisaria K K, Narayan D. The lamina cribrosa in some mammals - (a histological study). Indian J Ophthalmol [serial online] 1973 [cited 2019 Dec 5];21:178-81. Available from: http://www.ijo.in/text.asp?1973/21/4/178/34625

The structure of lamina cribrosa and its existence in some mammals has not been described in detail. TANSLEY [3] had worked on the lamina cribrosa in animals like mouse, rabbits, grey squirrel, cat and monkey. Finding the detailed description of this structure missing in other animals, a few more animals have been included in this work.


  Materials and Methods Top


For this work albino rats, guinea pigs, rabbits, dogs, monkeys and humans selected. All animals were killed under deep ether anaesthesia. Human eyeballs were enucleated from fresh dead bodies. All animals were male adults and normal except the humans whose eyes were enucleated from fresh bodies from any source brought to our anatomy department. Five animals from each mammal were studied.

Rat = 100-120 gms.

G. Pigs = 600-800 gms.

Rabbits = 1.25-1.5 kgms.

Dogs = 8-10 kgms.

Monkeys = 6-8 kgms.

Humans = could not be weighed.

Parrafin blocks of Bouin-fixed tissue of optic nerve with scleral rim only were cut at 5 microns thickness by a Spencer microtome and were stained with haematoxylin-eosin as well as with von-Gieson-Orcein methods.


  Observations Top


In the albino rats, guinea pigs and rabbits, oval nuclei of fibroblast cells arranged transversly at the level of sclera were observed [Figure - 1],[Figure - 2],[Figure - 3],[Figure - 4],[Figure - 5],[Figure - 6]. These nuclei were more prominent and larger in the albino rats, least in rabbits.

In the dogs haematoxylin-eosin and von-Gieson-Orcein stains gave positive results for the tissue forming lamina cribrosa. In some sections uveal tissue was observed to be entangled in the connective tissue of lamina cribrosa. [Figure - 7],[Figure - 8],[Figure - 9].

In the monkeys there was definite network of collagen and elastic tissue.

Parallel fibres of the optic nerve were seen piercing the transversly placed lamina cribrosal fibres. [Figure - 10].

In humans the lamina cribrosal fibres were clearly seen giving way to backward running optic nerve fibres and thus presenting a pattern of network [Figure 11].


  Discussion Top


The lamina cribrosa is made of collagen and elastic fibres. It is continuous with the sclera at the periphery and through it the optic nerve fibres from the retina run backwards. PRINCE et al [2] has stated that in the scleral region, the trabeculae of lamina cribrosa are formed of both glial and connective tissue and small blood vessels from the circle of Zinn. They also commented that in rabbits, a rodent, the lamina cribrosa is weak and have not commented on what is probably a unique finding of this work in dog, -- the presence of uveal tissue in this region. The presence of a network actually makes this spot stronger so as to withstand the intraocular pressure.

It was noticed that in rodents like rats, rabbits and guinea pigs, the lamina cribrosa was very poorly developed and in some instances absent. NICHOLLS AND TANSLEY [1] too have reported that it is absent in the rats. In the higher vertebrates like dogs, monkeys and human beings it is more developed. The lamina cribrosa in dogs does not present a well defined picture of criss-cross arrange­ments of fibres but show collections of transverse fibres of narrow width at some intervals. In monkeys and humans it is difficult to differentiate between the pattern of arrangement of fibres. In humans however the optic nerve bundles were passing through the lamina cribrosa in a more defined way. The presence of oval nuclei in the region of lamina cribrosa in rodents suggested that these are probably the precursors of what makes lamina cribrosa in higher animals.


  Summary Top


In this study the region of lamina cribrosa in mammals, albino rats, guinea pigs, rabbits, dogs, monkeys and humans was investigated. In rodents the region of lamina cribrosa presents only nuclei and no transverse fibres but in higher mammals, well defined lamina cribrosal fibres are discernable.

 
  References Top

1.
Nicholls, J. V. V. and Tansley, K.: Brit. J. Ophth. 22: 165-168, 1938.  Back to cited text no. 1
    
2.
Prince, J. H., Diesem, C. D., Eglitis. I., and Ruskell, G. L.: Anatomy and histology of the Eye and orbit in domestic animals. p. 40-278. Charles C. Thomas, Publisher., Springfie'id. Illinois. U.S.A. (1960).  Back to cited text no. 2
    
3.
Tansley, K.: Brit. J. Ophth. 40: 178-182, (1956).  Back to cited text no. 3
    


    Figures

  [Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7], [Figure - 8], [Figure - 9], [Figure - 10]



 

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