Comparison of Von Graefe and Maddox Rod Techniques in Measurement of Lateral Phoria

Phoria is a phenomenon in binocular vision and commonly assessed during eye examinations. This study observed the outcomes of lateral phoria testing performed using the two common phoria testing methods (Von Graefe and Maddox rod) and compared to each other in order to determine the influences of the different techniques on the lateral phoria status results with respect to the phoria type detected, phoria magnitude and the testing distance. A sample size of 100 participants aged 16 to 30 years old (21.90+2.60), were randomly selected and their lateral phoria assessed using both the Von Graefe method and the Maddox rod method. The results showed that the two phoria assessment methods, Von Graefe and Maddox rod, are both reliable in the assessment of lateral phoria at far and at near distances, there was no significant difference in the phoria results obtained from the two methods in terms of the type of phoria detected and the test distance. However, in magnitude of lateral phoria detected, Von Graefe results were slightly higher than the results derived from the Maddox rod method. After scatter plot of regression analysis, a positive correlational relationship (p < 0.05) was established between the Von Graefe method and the Maddox rod method of phoria assessment at far and at near as well. The authors conclude that there is a significant difference between Maddox rod method and the Von Graefe method only in magnitude of lateral phoria results, with the Von Graefe phoria results slightly higher than Maddox rod results. Key words: phoria assessment, lateral phoria, von Graefe, Maddox rod, test distance, Heterophoria