Application Study Of Fixation Disparity In The Analysis Of Binocular Visual Function

ObjectiveTo get different types of fixation disparity curves by measuring the prism-induced fixation disparity. Find the relationship between fixation disparity and stereo-acuity. Find out the relationship between the slope of fixation disparity curve and eyestrain. To find the possible relationship between fixation disparity and phoria. Analyze fixation disparity and convergence. To study the role of fixation disparity in analyzing binocular visual function and find a better exam method to value visual function. Provide information in clinical diagnosis and treatment.Methods80 college volunteer students, aged 20-25years old, were recruited in this study. Their spherical refractive error were less 6.00D, and astigmatism were less 1.00D.1. The refraction was made sure by objective and subjective methods.2. Fixation disparity was measured by Wesson fixation disparity card.3. Stereo-acuity was measured by digital stereoscopic test charts.4. The phoria in 40cm was measured by phoropter.5. The ability of convergence was measured by phoropter.6. Questionnaires asking about their level of ocular discomfort were taken after thirty minutes reading.7. The data was analyzed by the signed-rank test, chi-square test, Z Test. Analyze the relationship between parameters of fixation disparity and binocular visual function.Results1. We got four types of fixation disparity curve. Different type of fixation disparity curve had different percentage. Among them, type I and type II were present in 46.25%% and 8.75%% of the population respectively. TypeⅢ and typeⅣ were present in 26.25% and 18.75%.2. Different stereo-acuity has different percentage:stereo-acuity 40"presented 48.75%, stereo-acuity60"presented 31.25%, stereo-acuity 100"presented 11.25%, stereo-acuity 200"presented 7.5%, stereo-acuity 400"presented 1.25%.3. Fxation disparity was correlated with stereo-acuity (rs=-0.350, P=0.004).4. Different stereo-acuity (40"、60"、100"、200"、400") was divided into groups, the difference were statistically significant by chi-square test.5. Comparison between groups by using Z Test. The results were as following:The difference of stereo-acuity 40" and 100" were statistically significant (z=-2.912, P=0.004). The difference of stereo-acuity 60"and 100" were statistically significant (z=-2.205, P=0.027). The difference of stereo-acuity 40"and 60" (z=-1.277, P=0.202), stereo-acuity 40"and 200"(z=-1.134,P=0.257) stereo-acuity 40" and 400" (z=0.257, P=0.414), stereo-acuity 60"and 200" (z=-0.570, P=0.569), stereo-acuity 60"and 400" (z=-0.665, P=0.506), stereo-acuity 100"and 200" (z=-1.560, P=0.119), stereo-acuity 100"and 400" (z=-0.707, P=0.480), stereo-acuity 200"and 400" (z=-0.725, P=0.468) were not statistically significant.6. The slope of fixation disparity curve was made sure by 3△BI-3△BO. The slope was correlated with eyestrain (rs=0.857, P=0.000). Use SPSS 18.0 to find the linear regression equation. Y=-0.347+0.205X, rL=0.792.7. Fixation disparity was correlated with phoria (rs=0.255 P=0.040)ConclusionsWe find fixation disparity was correlated with stereo-acuity because of the same theoretical basis.By measuring fixation disparity, we find the slope of fixation disparity curve could reveal the degree of eyestrain. Fixation disparity was also correlated with phoria and convergence.Fixation disparity curve is a vital and effective way to value certain binocular visual function. It can support the diagnosis of abnormal binocular visual function. Combining analysis of abnormal binocular visual graphics and the Morgan standard value method, we can have a more comprehensive analysis of binocular visual function.