ERRORS OF REFRACTION 199 



hours; while, if atropin is used, the effect will last several 

 days. 



To do good work requires a great deal of time, ex- 

 perience, and patience. In man, the subjective method of 

 examination usually follows retinoscopy, as the patient 

 will not always accept his full correction. By the sub- 

 jective method is meant placing the patient at a distance 

 of 20 feet from the Snellen test-types, and requiring him 

 to read the normal line for that distance, either with the 

 exact correction by the retinoscope test or by a modifica- 

 tion of that correction. 



Of course, it is unnecessary to state that, with the Hght 

 near the head of the animal, it will be necessary to have 

 the animal in a darkened room. With much experience 

 one can become quite proficient with the use of the 

 retinoscope. 



