Accuracy of an objective binocular automated phoropter for providing spectacle prescriptions

Currently eye examinations are usually based on autorefraction followed by subjective refraction (SR) with a phoropter. An automated phoropter that can also perform autorefraction may facilitate the optometric workflow.

The efficiency and feasibility of an objective autorefraction and correction system are assessed by comparing objective refractive measurements with SR on the same subjects and evaluating the visual acuity (VA) values obtained after the objective refractive measurement and correction.

Objective autorefraction and correction was performed on 41 subjects using an automated binocular phoropter system. The auto-phoropter performs autorefraction by wavefront measurement and corrects the spherical and cylindrical errors with tunable fluidic lenses while the patient looks at a visual display inside the instrument. The instrument outputs are optometric constants of spherical and cylindrical aberrations. After measurement and automated correction of the refractive errors, the VA values were assessed by having the subjects look at an integrated Snellen chart. The objective measurement results were statistically compared with their SR.

The correlations between SR and objective autorefraction and correction spherical equivalents (M) were 0.98 (0.97-0.99) and 0.96 (0.93-0.98), the vertical Jackson cross cylinder (J₀) were 0.96 (0.92-0.98) and 0.95 (0.91-0.97), and the oblique Jackson cross cylinder (J₄₅) were 0.73 (0.55-0.85) and 0.82 (0.69-0.90), for the right and left eyes, respectively, with the 95% confidence interval (CI) values in parentheses. 89.0% of the 82 eyes had at least 6/7.5 VA.

A significant agreement between the SR and objective autorefraction and correction was observed. An all-objective refractive assessment with instantaneous verification may improve the precision of eye prescriptions and possibly reduce the procedure time.