SECTION V 



THE OPTICAL SYSTEM OF THE EYE 



THE optical system of the eye consists of those structures which together 

 focus an image of external objects on the retina. In the mammalian 

 eye there are four concerned : the cornea, the aqueous humour, the crystalline 

 lens and the vitreous humour. The histology of the cornea has already been 

 considered. The aqueous humour is a structureless liquid. The vitreous 

 humour consists of anastomosing trabeculaB of collaginous material, the 

 interstices of which are filled by a slowly circulating fluid similar to aqueous 

 humour. The vitreous is enclosed in the hyalcid membrane, and through 

 the middle of it runs the hyaloid artery during foetal life, which goes from 

 the central artery of the retina to the posterior surface of the lens. 



THE CRYSTALLINE LENS is a biconvex transparent elastic 

 body, enclosed in an elastic membrane called the capsule. To the 

 periphery of the capsule are attached the suspensory ligaments 

 of the lens, which are formed by the anterior radial fibres of the 

 thickened portion of the hyaloid membrane (the zonula of Zinn). Between 



Cornea 



Sinus venosus 



Conjunctiva 



Corpus Zonula 

 ciliare cil-aris 



Retina 



FIG. 260. Section through anterior part of eyeball to show mode of suspension 

 of lens. (After MERKEL and KALLIUS.) 



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