Systoiiatic Inspection of the Eye. 325 



nation it may be determined whether these are on the conjunctival 

 surface, in the superficial or deeper layers of the cornea or in the 

 the membrane of Descemet. Similarly cloudiness or floating ob- 

 jects in the aqueous, reflect the luminous rays, and so with opaci- 

 itiesinthe lens or its capsule, or in the vitreous. In the same way 

 the surface of the iris and corpora nigra may be carefully scrutin- 

 ized. For satisfactor\' examination of the media, back of the iris, 

 the pupil should be first dilated, by instillation under the lid of a 

 drop or two of a 3 per cent, solution of atropia, and the ex- 

 amination proceeded with twenty minutes later. Homatropin is 

 preferable to atropin as being less i)ersistent in its action, and less 

 liable to produce conjunctivitis. If it fails to produce the requi- 

 site dilatation, it may be followed b}' a drop of a 4 per cent, 

 solution of hydrochloride of cocaine, which will secure a free 

 dilatation, lasting onlj' for one day in place of seven days as with 

 atropin. The cocaine furtlier removes pain and favors the full 

 eversion of the eyelids. 



The instruments required for focal illumination are a biconvex 

 lens of 15 to 20 diopters, and a good oil lamp or movable gas jet. 

 The light of the sun is not satisfactory. The examination ought 

 to be conducted iu a dark room, or less satisfactorily in semi- 

 darkne.ss. Tlie lamp is held b}'- an assistant at the level of the 

 eye to be examined, eitlier in front or behind, or first one and 

 then the other, so that the rays of light may fall upon the eye 

 obliquely. If the lids are kept closed it may be necessary to ex- 

 pose the cornea by pressing on the lids with the finger and thumb. 

 The light is held 8 or 10 inches from the eye and the lens is in- 

 terposed between it and the eye and moved nearer and more dis- 

 tant until the clearest illumination has been obtained of the point 

 to be examined. In tliis way ever\' accessible part of the eye 

 may be examined in turn. The examiner may make his results 

 more satisfactory by observing the illuminated surface through 

 a lens magnifying three or four diameters. It is important to 

 observe that the eye of the operator must be in the direct line of 

 reflection of the pencil of light. 



Cornea. B}- focusing the light in .succession over the different 

 parts of the surface of the cornea, all inflammations, vascularities, 

 opacities, ulcers, and cicatrices will be shown and their outlines 

 clearly defined. By illuminating the deeper layers of the cornea 



