Short-Term Residual Myopic Bias Measured by Open-Field Autorefraction After 10-Second Myopic Overcorrection in Young Myopic Adults

The magnitude and short-term recovery of residual objective myopic bias after a brief, clinically plausible over-minus exposure during distance refraction remain insufficiently quantified. This study quantified the short-term residual objective myopic shift following 10 s of transient myopic overcorrection of 0.50 D or 1.00 D in young adults with myopia. Twenty healthy young adults with myopia and low astigmatism underwent open-field automated objective over-refraction (OR) while viewing a high-contrast 5 m target. After trial lenses induced a moderate myopic state, each participant completed three randomized 10 s lens conditions: 0.50 D undercorrection, 0.50 D overcorrection, and 1.00 D overcorrection. The primary endpoint was OR at 5 s after restoration of the objective neutral correction. Both overcorrection conditions produced significantly more negative OR than undercorrection at 5 s; exploratory analyses showed the same pattern at 10 s. The shift was evident at 5 and 10 s after restoration of the objective neutral correction and, by 30 s, was no longer statistically significant and appeared clinically negligible. This bias should be considered when OR measurements obtained shortly after over-minus lens exposure are used to inform subsequent subjective refinement.