THE LUCKIESH-BERENS tangent screen illuminator previously demonstrated1 was developed to provide for the lighting requirements necessary in the study of central visual fields with white and colored test objects. The illumination formerly proposed2 was found to be lacking in some essentials for scientific work and for the comfort of the examiner. The general specifications established for the unit were as follows:
The illuminator should provide continuously variable illumination of from 1 to 100 foot candles.
It should contain a means for quickly checking and adjusting the level of illumination.
The level of illumination in the 25 degree zone of a tangent screen located 75 cm. in front of the illuminator should not vary more than 10 per cent.
The quality of the light should approximate that of daylight in order to minimize distortion of color.
The color or spectral character of the light must not change as the
BERENS C, LUCKIESH M. A TANGENT SCREEN ILLUMINATORConstruction, Use and Advantages. Arch Ophthalmol. 1948;39(2):176-182. doi:10.1001/archopht.1948.00900020181004