Fixation of the patient's gaze during fundus photography is essential if satis- factory results are to be obtained. The fixation devices supplied on current fundus cameras, however, do not permit fixation of the patient's gaze while photographing areas temporal to the macula.
While the temporal fundus is being photographed, the fellow eye must fix in the nasal direction. This direction of gaze is impossible to control with the present fixation devices because the lens tube of the camera
prevents the travel of the fixation device in
the nasal direction (Fig 1A).
When a 60 Δ prism is placed, base out, infront of the fellow eye, the fixation light is apparently moved beyond the lens tube, permitting the photographer to control accurately the gaze of the patient while photographing the fundus temporal to the macula (Fig 1B).
The prism is mounted on the camera in the same fashion as the Hruby
STENSTROM WJ. An Aid to Accurate Fixation During Fundus Photography. Arch Ophthalmol. 1963;70(3):389-390. doi:10.1001/archopht.1963.00960050391023