Hegner Tables

HEGNER TABLES (Hegner), are used for precise determination of visual acuity at close distances in cases of severe visual impairment. They are constructed on the principle of international test typefaces, i.e., they consist of 12 rows of rings with breaks and of the numbers 1, 4, 7 and 0 in various combinations and of different sizes. The Hegner Tables are calculated for a distance of 25 cm. The subject is fitted with telescopic glasses for distance, seated at the mentioned distance in front of the table, and spherical lenses are placed in front of the glasses. Depending on the degree of magnification of the telescopic glasses and the power of the lens placed in front of them, visual acuity is increased, which is then determined by the Hegner Tables. Thus, e.g., if during a regular examination visual acuity was determined as 0.12, then with telescopic glasses having a magnification of 1.8 times and a spherical lens of +8 D, giving a magnification of 2 times, a total magnification of 3.8 times is obtained, and visual acuity reaches 0.45. In the appropriate manuals there are graphical tables calculated for a book distance of 25 and 30 cm from the eye, from which the power of the magnifying system (telescopic or magnifying glasses + additional lens) is read off, which increases a certain decrease in visual acuity to the desired limits.