HUMAN EYE. 295 



LESSON LXIY. 

 THE OPHTHALMOSCOPE. 



The Ophthalmoscope. Two methods are employed, and the 

 student must familiarise himself with both. 



1. Direct giving an upright image. 



2. Indirect giving an inverted image. 



The observer must practise both methods on another person, 

 or use a rabbit for the purpose, or use an artificial eye. 



A. Human Eye. 1. The Direct Method. 



(a.) About twenty minutes before the examination is 

 commenced, instil a drop of solution of sulphate of atropia 

 (2 grains to the ounce of water in a drop-bottle), or hom- 

 atropin into, say, the right eye of a person with normal vision. 

 The pupil is dilated and accommodation for near objects is 

 paralysed, owing to the paralysis of the ciliary muscle. The 

 patient is seated in a darkened room, and the observer seats 

 himself in front of him, and on a slightly higher level. 

 Place a brilliant light obscured everywhere except in front, 

 on a level with the left eye of the patient. 



(b.) The observer takes the ophthalmoscope mirror in the 

 right hand, resting its upper edge upon his eyebrow, holds 

 it in front of his own eye, looking through the central hole 

 in it, and directs a beam of light into the observed eye, 

 when a red glare the reflex is observed. The patient is 

 told to look upwards and inwards, which is conveniently 

 accomplished by telling him to look to the little finger of the 

 operator's right hand. The operator then moves the mirror, 

 with his eye still behind it, and looks through the hole 

 until the mirror is within two to three inches from the 

 observed eye, taking care all the time that the beam of light 

 is kept steadily thrown into the eye. If the eyes of the 

 observer and patient be normal, the observed has simply to 



