SECTION VI 



OEGANS OF SPECIAL SENSE 



{ 



THE EYE 



By R. MARCUS GUNN, M.A., F.R.C.S. 



SURGEON TO THE ROYAL LONDON OPHTHALMIC HOSPITAL, MOORFIELDS ; OPHTHALMIC SURGEON TO THE 



NATIONAL HOSPITAL 



THE EYEBALL AND ITS SURROUNDINGS 



General Surface View 



Tliis examination is to be made i)rior to anj' disturbance of the parts, and is, indeed, best 

 ct»nducted on the Uving body. A pocket magnifying lens should be at hand for use when 

 required. 



THE two eyes are situated nearly in the line where the upper and middle thirds 

 of the face meet; they lie rijjht and left of the root of the nose, the most 

 prominent part of the front of each globe being about an inch and a quarter 

 from the middle line of the face. Each eye is overshadowed b}' the corresponding 

 eyebrow, and is capable of being concealed by its eyelids, upper and lower. 



The orbital margin may be traced all round with the finger. At the junction of 

 the inner and middle thirds of the upper margin, the supraorbital notch can usually 

 be felt, and the supraorbital nerve passing through it can sometimes be made to roll 

 from side to side under the finger. The inner margin is the most difficult to trace 

 in this way, partly because it is more rounded of? than tlic others, partly because 

 it is l)ridged over by a firm fibrous V)and (tendo oculi, or inner palpebral liga- 

 ment), passing inwards from the eyelids; l»elow this band, however, a sliarp l>ony 

 crest is felt, which lies in front of the lachrymal sac. Note how the eye is pro- 

 tected by the rim of the orbit, above and V)elow; if we lay a hard flat body over 

 the orbital opening, it will rest upon the upper and lower bony prominences, and 

 will not touch the surface of the globe. Inwards, the eye is protected from injury 

 mainly by the Vjridge of the nose; outwards it is most readily vulnerable, as here 

 the orbital rim is comparatively low. With one finger ])laced over the closed upper 

 lid, now press the eyeball gently backwards into the orbit, and ol»serve the elastic 

 resistance met with, due to the fact that the glol)e rests j)Osteriorly on a pad of fat. 



Till- space between the free edges of the up])er and lower lids is known as the 

 palpebral aperture : it is a mere slit when the lids are clo.ssed; but when they are 

 open its sliape is. roughly, that of an almond lying with its long axis horizontal, 

 and aViout thirty millimetres in length. 



When the eyes are directed to an object .straight in front of them, this aperture 

 is about twelve millimetres wide, but its width varies with upward and downward 



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