243 LABORATORY GUIDE IN PHYSIOLOGY. 



and the model to about 2 or 3 cm. The skiascopic 

 eye will then be illuminated and the fundus with its 

 structures will be clearly defined. 

 ^. Observations. 



a. Adjust the model to represent the emmetropic eye. 



(1) Determine, with the ophthalmoscope, the color of 

 the fundus. Enumerate the structures seen. 



(2) Describe the papilla, or entrance of the optic 

 nerve. Is the papilla in the visual axis or to one 

 side of it? Describe its position with respect to 

 the visual axis of the eye and determine the most 

 advantageous position of observer, model and in- 

 strument to get a direct view of the papilla in the 

 right eye; in the left eye. 



(3) Describe the location of the arteria and vena 

 centralis retina! with reference to the papilla. 



(4) The ring formed by the border of the papilla is 

 sometimes called the scleral ring or the choroidal ring. 

 Can this ring be distinctly seen ? 



(5) The macula lutea and the fovea centralis are the 

 most sensitive portions of the retina and are in a 

 direct line with the visual axis of the eye. 



What is the most advantageous position of model, 

 observer and instrument in order to get a direct il 

 lumination of this part of the fundus? Describe 

 the appearance of the structures in question. 



(6) Describe the retinal blood vessels minutely; 

 drawing a map of their distribution. 



b. The observation of the retina in t'he hyperopic eye. 



Adjust the model for three dioptrics of hyperopia. 



(7) Are the retinal blood vessels distinct when the 

 above described method of observation is used? 



(8) Place in the rack, before the model eye, the follow 



