84 



MICROSCOPY OF THE LIVING EYE 



of the posterior part of the interior of the eye, inchiding the fundus, 

 by the appHcation of corneal contact glasses, much practised in 

 the first instance mainly by Kceppe, will not be dealt with here ; 

 it has too many practical difficulties to be of material use in general 

 clinical work ; the hand ophthalmoscope and the binocular 

 Gullstrand ophthalmoscope provide more appropriate means of 



studying the eye fun- 

 dus of living persons. 

 Passing reference may 

 be made to the study 

 of the angle of the 

 anterior chamber — 

 normally inaccessible 

 to observation 

 — through a corneal 

 CO ntact glass by 

 means of Troncoso's 

 " Gonioscope " ; this 

 portable hand instru- 

 ment is a variety of 

 self-illuminating 

 periscope allowing 

 of observation of a 

 chamber-angle under 

 magnification of low 

 degree. The binocular 



Fig. 2.— Diffuse reflection, specular reflection, microscope of Czapski 

 and transmission with refraction. has existed for many 



years ; it has been put to but little clinical use by ophthalmologists 

 mainly because the visibility of features deep within the trans- 

 parent tissues of the eye is relatively poor when the area of tissue 

 through which the observation is made is also the path of entry of 

 the illuminating rays ; this is unavoidable when beams of light of 

 wide diameter are used. 



If an incident beam of light (lY, Fig. 2) strike a polished surface 

 of a block, PD, of a transparent substance like glass, in say, air, 

 some of the light — a high proportion if the surface is highly 



