THE SENSE ORGANS 



195 



rect his error in refraction by placing a suitable lens behind the opening 

 in the mirror. 



7. Ophthalmoscopic Examination of the Ametropic Artificial Eye by 

 the Direct Method. Render the artificial eye ametropic by pushing 

 its two parts closer together or by separating them more widely. Ex- 

 amine its retina with the ophthalmoscope held at a distance of from 

 30 to 50 cm. in front of it. When the details of the fundus have be- 

 come visible, move your head together with the ophthalmoscope from 

 side to side. In the hypermetropic eye the retinal vessels will appear 



FIG. 114. LORING'S OPHTHALMOSCOPE, WITH TILTING MIRROR, COMPLETE DISK OF 

 LENSES FROM 1 TO 8 AND TO + 7, AND SUPPLEMENTAL QUADRANT CONTAINING 

 0.5 AND 16 D. THIS AFFORDS 66 GLASSES OR COMBINATIONS FROM + 23 TO 24 D. 



to move in the same direction, and, in the myopic eye, in the opposite 

 direction. Having in this way determined whether the eye is myopic 

 or hypermetropic, measure the degree of this ametropia in the following 

 manner: 



Place the ophthalmoscope in the anterior focal plane of the artificial 

 eye, i. e., 5 cm. in front of its cornea. Illuminate the pupil and accom- 

 modate your own eye for a distant point. If the artificial eye is myopic, 

 place behind the opening in the mirror concave lenses of different 

 strengths, until the lens has been found which renders a certain part 

 of the optic disk for example, a peripheral blood-vessel perfectly 



