Comparison of the Visual Acuity and Refractive Error Using OPDIII and Subjective Findings in Visually Normal Subjects

To compare the visual acuity and refractive error using OPDIII and subjective findings in visually normal subjects.

This study was performed on 75 participants (134 eyes) with an age range of 18 to 35 years. Visual acuity was evaluated using both subjective Snellen chart and OPDIII devices. Also, OPDIII objective refraction was compared with subjective refraction. Paired t test was used to compare mean visual acuity and refractive error. The 95% limits of agreement (LOAs) were reported to evaluate the agreement between subjective and objective methods.

The mean Snellen visual acuity was 0.705±0.243 logMAR in group with myopia and 0.375±0.207 logMAR in group with hyperopia. Visual acuity obtained using OPDIII was 0.632±0.270 and 0.054±0.084 logMAR in groups with myopia and hyperopia, respectively. There was a significant difference in the mean visual acuity between OPDIII and Snellen chart. The correlation of the Snellen chart with OPDIII was 0.862 and -0.172 in myopic and hyperopic groups, respectively. The 95% LOAs of the OPDIII with Snellen chart were -0.33 to 0.18 and -0.14 to 0.79 logMAR in myopic and hyperopic patients, respectively. The mean spherical power obtained by OPDIII was more negative than that of subjective refraction (OPDIII mean difference -0.272±0.335 and 0.163±0.302 DS in myopic and hyperopic groups respectively), while the cylinder power was less than that of the subjective refraction (OPDIII mean difference 0.488±0.566 and 0.030±0.255 DC in groups with myopia and hyperopia, respectively). The correlation of OPDIII with subjective refraction was 0.905, 0.920 in measurement of the spherical power and 0.908, 0.928 in measurement of the cylinder power in groups with myopia and hyperopia, respectively.

Visual acuity scores were significantly better using OPDIII compared with Snellen chart in group with myopia, whereas the Snellen chart provided the better visual acuity scores in hyperopic patients. Although the correlation of OPDIII with subjective refraction in measuring the refractive error was high, OPDIII showed a significant difference with subjective refraction.