Myopia is a common problem in the ophthalmic clinic that affects visual acuity. The present protocol demonstrates a convenient method to examine dynamic visual acuity in myopia patients with eyeglasses correction. The present protocol is standard and efficient in examining dynamic visual acuity in myopia appear patients with a short learning curve, therefore it can be easily promoted in the ophthalmic clinic.
The dynamic visual acuity test can be applied in various diseases and situations including cataract and refractive surgery. Compared with static visual acuity it might reflect real life visual function better. To begin, perform automatic computer optometry as the primary data for subjective refraction, and measure the pupil distance.
Examine one eye at a time and occlude the other eye. Achieve the maximum plus to maximum visual acuity fogging with plus 0.75 to plus 1.0 diopter lens inducing a visual acuity of 0.3 to 0.5. Then gradually decrease the positive lens or increase the negative lens by 0.25 diopter per step.
Use a Lancaster red-green test to tune the accurate spherical diopter. Add more negative and positive lenses if the patients report that the letter seen against the red or green background is clearer. Refine the cylindrical axis by placing the Jackson cross cylinder device in the axis position so that the thumb wheels connecting line is parallel to the axis of astigmatism.
Rotate the thumb wheel, and ask the subject to compare the clearness between both sides. Turn the cylindrical axis toward the red dots on the cross cylinder in the side with clearer vision. Repeat the binary comparison until the end point.
Refine the cylindrical power by turning the Jackson cross cylinder device such that the thumb wheel's connecting line is at 45 degrees to the astigmatism axis. Rotate the thumb wheel and ask the subject to compare the clearness between both sides. Add a negative or positive lens if the patient reports better placement of the cross cylinder red or white dots connecting line along the cylinder axis.
Repeat the binary comparison until the end point. Repeat the Lancaster red-green test to tune the accurate spherical diopter for the second maximum plus to maximum visual acuity. For binocular balance, apply a vertical prism of six prism degree before one eye to dissociate the binocular vision.
Balance the clarity of the opto types between both eyes. Adjust the test distance according to the requirements. Adjust the seat to make the subject see the screen's midpoint level.
Ensure the subject wears the distance vision corrected eyeglasses binocularly. Test the parameter configurations by setting the opto type moving velocity in the initial opto type size. For the pre-test, display five opto types with a randomized opening direction to guide the subject's understanding of the test mode.
Start the test at a size three to four lines bigger than the best corrected DVA. Display the opto type with randomized opening directions. Tell the subject to identify the opening direction of the moving opto type.
Present the next opto type after the subject's response. Present eight opto types for each size, so that each identified opto type gains 1/8 of 0.1 logmar visual acuity. If five out of eight opto types are identified correctly, adjust the opto type to one size smaller.
Repeat the above procedures until the size for which the subject can identify less than five opto types is obtained. Record the minimum size that subjects can recognize no less than five out of eight opto types, and the number of opto types recognized for one size smaller. Calculate DVA according to the algorithm of logarithmic visual acuity as described in the text manuscript.
The cumulative results demonstrated that 75%of subjects possessed better than 0.2 logmar DVA for 40 degrees per second, and 62%for 80 degrees per second DVA. The percentage of the subjects with better than 0.1 logmar 40 degrees per second binocular DVA was 22%And for 80 degrees per second, the percentage was 12%Significant results were obtained from curve estimation fitting an age DVA of 40 degrees per second with a quadratic and cubic curve, but not a linear model. For 80 degrees per second DVA, all the linear quadratic and cubic curves were able to fit the age DVA scatter plot appropriately.
The effect of each potential influential factor for 40 and 80 degrees per second DVA in single factor linear mixed models, and the statistical results were documented. When 40 degrees per second DVA was used to measure variability, higher monocular and mean binocular sphere and spherical equivalent were significant negative influential factors. Similarly, larger monocular and mean binocular sphere and spherical equivalent were significant negative influential factors for 80 degrees per second DVA.
The effect of factors and covariates for the multifactor linear mixed model demonstrated that a larger binocular means spherical equivalent was a significant negative influential factor 40 and 80 degrees per second DVA. Older age was a significant negative influential factor for 80 degrees per second. The most important thing is to ask the subject to focus on the moving opto type to identify the opening direction, and present the next opto type after the subject's response.
