LIV. Skiascopy, 



Gould defines skiascopy as " a method of estimating 

 the refraction of the eye by observation, through the 

 ophthalmoscopic mirror, of the movements of the retinal 

 images and shadows" Synonyms: Fundus reflex test; 

 umbrascopy; pupiloscopy; koroscopy; keratoscopy; ret- 

 inoscopy, etc. 



1. Appliances. A simple retinoscope or an ophthalmos- 

 cope with a plane mirror; Thorington's skiascopic eye 

 or an equivalent; dark room; lamp; etc. 



2. Operation. The observed eye and lamp are to have 

 the same relative position as in ophthalmoscopy. Let 

 the observer sit directly in front with the eye in the 

 same horizontal plane with the lamp and observed eye, 

 and somewhat more than 1 m. distant from the observed 

 eye. Throw the light reflected by the mirror into the 

 observed eye; rotate the mirror slowly and a shadow will 

 be seen in the pupil of the observed eye. 



j. Observations. 



a. Observation of the emmetropic eye. Adjust the model 

 to represent emmetropia. 



( 1 ) Does the shadow move in the same direction as the 

 mirror rotates or in the opposite direction, i. e., does 

 the shadow move "with the mirror" or "opposite?"" 



(2) Is the movement of the shadow quick or slow. 



b. Observation of the myopic eye. 



(I) Adjust the model to represent less than 1 D. of 

 myopia. 

 (3) Note that the shadow movement is with the 



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