ATANGENT screen for charting visual fields is difficult to make and, if purchased, is expensive. Plotting the measurements on a surface and painting or sewing them on requires skill in mathematics as well as manual dexterity. When completed, the marks of the measurements are usually for one distance only—1,000, 2,000 or 3,000 mm.—and are set at one height. As it is often desirable to take fields with the tangent screen at more than one distance, it is an advantage to have available the measurements for 1,000, 2,000 and 3,000 mm. Tangent screens can be made so that they may be elevated or lowered to suit the height of the individual patient, but this adds to an already complicated and expensive procedure. These difficulties and shortcomings may be responsible for neglect in utilizing the valuable diagnostic and prognostic aid which tangent screens offer.
In order to obtain a ready method of
GUY LP. A RULER FOR MEASUREMENT OF VISUAL FIELDS ON THE TANGENT SCREEN. Arch Ophthalmol. 1946;36(5):617-619. doi:10.1001/archopht.1946.00890210627006