779 
by a contraction of the m. obliquus superior. There exists however 
hardly any suitable method exactly to ascertain the position of the 
eyes. We shall at all events best succeed, if binocular vision exists 
(whieh will, as a rule, be the case for a paralysis or paresis) and 
we can make use of the position of the double-images for the 
purpose we have in view. 
In the “Zeitschrift für Augenheilkunde” Vol. XXXV, N°. 4 Hess 
indicates a method, based on the subjective localisation of the double- 
images. For clinical purposes this method is as a rule sufficient and 
highly to be recommended, for physiological investigation it can 
however not satisfy all the requirements that may be wanted. 
I have tried to find a method that is more suitable to a similar purpose 
of which | intend to give here a description. Binocular vision 
and good correspondence of the retina is for this method likewise 
required. 
The purpose of the investigation will consequently be exactly to 
ascertain the position of one of the two eyes, whilst the other eye 
has obtained a determined direction of regard by looking at an 
indicated point of fixation. 
For this purpose the patient is placed directly opposite a vertical 
wall, at a distance of at least 3m. Directly in front of the patient, 
at a level with his eyes, a point © is marked on the wall. Now 
we suppose, that the distance from © to the point of rotation of 
the eye is =a and that when the head is erect and at binocular 
fixation of ©, both the eyes, are in the primary position, conse- 
quently in the position from which the normal eye moves according 
to the law of LasrinG. 
As second point we apply to the wall the point Q which must 
serve as point of fixation. In some cases we can make the points 
O and (Q coincide as Fig. 1 indicates. 
| 
= ( a 
Sse 7 
