Comparison of zero position prisms on two cross-test variants

Purpose. This study compares two cross-test variants for determining the zero position prism of associated heterophoria. The aim is to achieve a zero position in the cross-test using the measurement and correction method according to Haase (MKH), which involves the use of measurement glasses with prismatic lenses. In the digital cross-test, the zero position is achieved by synchronous displacement of the polarized cross-test bars and the polarized frames.

Material and Methods. 40 test subjects aged between 19 and 53 with associated heterophoria are examined in the optometry laboratory of the Berlin University of Applied Sciences. The study uses, the MKH cross-test (prismatic lenses) and a digital cross-test (digital movement of testbars) on the “Eye-Office 3Dplus” vision testing device from the manufacturer “software & vision Sarrazin GmbH & Co. KG” in version 192.168.173.1 with a screen size of 43 inches. The measurement results are based on the zero position of the crossbars on both methods. The starting test is selected alternately, and each test subject undergoes both methods twice.

Results. The measurements can be categorized as reproducible based on the analysis of the repeat measurement. The results show that the horizontal zero position prisms (N = 37) on the MKH cross-test (prismatic lenses) are larger by a factor of 1.56 than on the digital cross-test (digital movement of testbars). The vertical zero position prisms (N = 37) on the MKH cross-test (prismatic lenses) are 1.50 times larger than those of the digital variant (digital movement of testbars). Through repeated measurements, a high level of agreement is observed within each cross-test variant, allowing the results to be used for comparing the compensatory prisms.

Conclusion. The two variants of the cross-test do not provide identical results. The research question of this study focusses exclusively on the comparison of the measurement results. The compatibility of the measured compensatory prisms was not checked using either method.