Refractive error is a problem with the focusing of light on the retina, while heterophoria is a hidden deviation in the position of the eyes that only becomes apparent when image fusion is disrupted (e.g., when one eye is covered). Although these two causalities may seem unrelated, they may nevertheless influence each other. For example, a strong refractive error may require more effort to focus, which may be associated with greater strain on the eye muscles and potentially worsen the symptoms of heterophoria. Correction of the refractive error can not only improve overall visual acuity, but also alleviate symptoms, such as eye fatigue, resulting from the presence of heterophoria (Wajuihian SO, 2018).

Results

Aims: The aim of our study was to demonstrate a statistically significant correlation between refractive error and heterophoria at distance and near and to find statistically significant differences in refraction in probands with heterophoria at near.
Material and Methods: The basic set included 38 probands and 76 eyes (n = 38) with an average age of 22.1 ± 4.5 years. There were 4 men and 34 women in the set. They were mainly young and generally healthy individuals. Serious eye pathologies were not diagnosed by the ophthalmologist. To prove hypothesis B, we divided the basic set of 38 probands into 3 sets according to the size of the detected heterophoria at near. Objective refraction was measured on a standard TRK-1P instrument refractometer (Topcon Corp., Tokyo, Japan). Heterophoria at distance and near was measured using the von Graefe technique and at near with a Howell card.
Results: The values of Spearman's correlation coefficient for the right eyes r = -0.03 for distance heterophoria and r = 0.03 for near heterophoria and for the left eyes r = -0.06 for distance heterophoria and r = -0.002 for near heterophoria showed a very low correlation. All results were valid at the statistical level of p > 0.05. Furthermore, the Wilcoxon test was used to determine the mutual agreement of two variables. The results of this test at the statistically significant level of p = 0.05 showed that there is no difference in the refractive states of probands with exophoria and esophoria for near.
Conclusion: The results of the correlation tests show that the spherical equivalent of refraction at a statistically significant level according to our study does not correlate with the size of distance and near heterophoria. We also did not detect a statistically significant difference in the refractive states of probands with exophoria and esophoria at a near distance.
Key words: refractive error, refractometer, Von Graefe, prism, Howell card, heterophoria.

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