Bauhaus-Universität Weimar

Titel:
Photography of the fundus of the human eye
Person:
Salomonson, I. K. A. Wertheim
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit22833/3/
328 
by slight movements of the ophthalmoscope lens can always be 
removed from any part of the real image of the fundus. 
But their presence is an absolute hindrance to .photography. They 
cause the appearance on the negative of one or two large spots, 
covering its central part and having a diameter of nearly 1/i of the 
whole negative. The brightness of these reflexes is several hundred 
times larger than that of the image of the fundus. I have tried in 
many different ways to eliminate these reflexes and have found that 
they could be reduced so as to be almost invisible by means of two 
small screens. 
In accordance with this principle I constructed a new photographic 
ophthalmoscope. The diameter of the negative is 40 mm. The retina 
is photographed with a magnification of 4.7 times, over an angle 
of 33 degrees, giving an image with a diameter of about 51/, times 
as large as the norm'al optic disc. The small arclamp of 4 to 5 
Amperes with which the instrument is fitted allows of exposures of 
l/l4 of a second, though this may be reduced to 7,0 of a second in 
some cases. However as the reflex time for the orbicular muscle 
reflex is much longer there is no advantage in further reduction of 
the time of exposure. The exposures are short enough to give sharp 
negatives even in a case of nystagmus. 
The quality of the negatives is generally sufficient. They are 
sharply defined. Generally the middle part is more strongly impressed 
than the marginal parts, as was to be expected. Yet direct enlarge¬ 
ments or prints can nearly always be made without any retouching. 
The whole apparatus, which will be fully described elsewhere can 
be used for both eyes without any alteration except the ordinary 
focussing. The dimensions are only slightly larger than those of the 
Gullstrand-Zeiss demonstration-instrument. Its use is not much more 
difficult than the making of an ordinary photograph with a studio- 
camera.
        

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