The use of autorefractors using the image-size principle in determining on-axis and off-axis refraction. Part 3: Theoretical effect of pupil misalignment on peripheral refraction for the Grand-Seiko Autorefractor.

Purpose: To determine, through simulations, the effect of lateral misalignment of the Grand-Seiko WR-5100K autorefractor on peripheral refraction.

Methods: Using a Navarro schematic eye, into- and out-of-the eye raytracing was done for a Grand-Seiko autorefractor simulation. For comparison, conventional out-of-the eye raytracing simulated the use of a Hartman-Shack aberrometer. Peripheral refractions were determined out to ±40° along the horizontal visual field with lateral misalignments up to ±1 mm.

Results: The effects are high, and greater when misalignment and the visual field are in opposite directions than when they are in the same direction. For example, 1 mm nasal misalignment causes mean sphere errors of -2.7 D and +1.3 D at 30° temporal field and 30° nasal field, respectively. These effects are approximately twice those occurring in a previous experimental study. Effects are small with the Hartmann-Shack simulation, with mean sphere errors not exceeding 0.03 D with 1 mm instrument misalignment.

Conclusion: Misalignment of the Grand-Seiko WR-5100K autorefractor is predicted to cause considerable errors in peripheral refraction. The simulation produces about twice the errors found in an experimental study, and the reason for this is unknown.