THE NUMEROUS devices for the taking of perimetric fields indicate that manufacturers are always endeavoring to devise a machine which will least divert the patient and thus enlist his cooperation in this subjective test.
Perimeters are usually constructed so that the isopter recordings are out of view of the patient, usually at the back of the instrument. This is a distinct advantage so far as the results obtained are concerned. On the other hand, the ophthalmologist does not get the complete picture until the entire field is plotted.
When the tangent screen is used, the recording is clearly seen on the board, and the observer can note very early in the examination at which portion within the 30 degree area there is evidence of scotoma or sector defect. The ophthalmologist can then carefully analyze this location without fatigue to the patient. In the examination of patients with the tangent screen,
FELDMAN JB, ABRAHAMS HJ. FLUORESCENT COLORS IN TANGENT SCREEN EXAMINATIONS. Arch Ophthalmol. 1946;36(5):537-539. doi:10.1001/archopht.1946.00890210547002