Refractive changes with post-rotatory nystagmus in healthy individuals.

PURPOSE Post-rotatory nystagmus has been used to detect autism spectrum disorders in clinical settings. Although previous studies have focused on eye movements, they did not evaluate the change in ocular refraction during post-rotatory nystagmus. This study aimed to evaluate the changes in ocular refraction during post-rotatory nystagmus in healthy individuals. METHODS A total of 34 healthy volunteers (mean age ± standard deviation, 20.9 ± 0.6 years) participated in this study. The ocular refraction during post-rotatory nystagmus was measured using MR-6000 (Tomey Inc.) on quick mode with a sampling rate of 30 Hz under noncycloplegic and cycloplegic conditions. The amplitude of post-rotatory nystagmus was calculated on the basis of the anterior eye images, while the ocular refraction measurements were simultaneously recorded. The accommodative convergence per accommodation ratio was calculated using the heterophoria method. Video oculography was performed to measure the angle of convergence during post-rotatory nystagmus. RESULTS The changes in ocular refraction during post-rotatory nystagmus were significantly greater under the noncycloplegic condition than under the cycloplegic condition. The changes in ocular refraction during the post-rotatory nystagmus were significantly and positively correlated with the amplitude of post-rotatory nystagmus under the noncycloplegic condition. The angle of convergence during post-rotatory nystagmus was significantly higher under the noncycloplegic condition than under the cycloplegic condition. The changes in the angle of convergence were significantly and positively correlated with the predicted accommodative convergence. CONCLUSIONS These findings suggest that the accommodation was functional during the post-rotatory nystagmus to compensate for the retinal image slip, and the accommodative convergence can help weaken the nystagmus.