Comparison of four different binocular balancing techniques

Several techniques of balancing have been proposed for the equalisation of the accommodative state between the two eyes. This study was designed to compare the results of different balancing techniques.

In this study, 60 subjects participated. Refractive errors were determined using retinoscopy and results were refined with monocular subjective refraction to determine the ametropia with the most plus lens and this was used as the starting point for balancing. The monocular refractive values before the balance were the same for all balancing procedures. Four balancing techniques, three dissociated and one associated, (alternate occlusion, prism-dissociated blur balance, prism-dissociated red-green balance and Humphriss immediate contrast method) were used for the final refinement of findings. Results were analysed as the interocular spherical difference (IOSD) after the completion of each balance procedure. The interocular spherical difference was defined as the right eye sphere minus the left eye sphere. Data were analysed in SPSS.17 software using the paired samples t-test, the Pearson correlation, repeated measures ANOVA and 'intraclass correlation coefficient' (ICC) tests.

The lowest mean difference was related to the alternate occlusion with the prism-dissociated blur balance techniques. The lowest 95% limits of agreement were related to the prism-dissociated red-green balance with the Humphriss immediate contrast methods. The highest correlation and intraclass correlation coefficient were related to the prism-dissociated red-green balance with the Humphriss immediate contrast methods.

The four balancing methods yield very similar results. The balance findings with red-green dissociated method and the Humphriss immediate contrast technique can be considered interchangeable and the other pairs of comparisons very nearly so.