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August 21, 2025Open Access

Emmetropia deviation in autorefraction compared to subjective refraction result in patients after corneal refractive surgery

Key Points

After corneal refractive surgery, autorefraction results deviate from emmetropia more than subjective refraction, impacting patient assessment.
In a study of 2180 eyes, hyperopic patients showed a 0.33 D difference favoring autorefraction, while myopic patients showed a 0.49 D difference favoring subjective refraction.
Subgroup analysis revealed significant relationships between refractive error types and the differences observed in sphere measurements between the two methods.
Results imply that autorefraction may not reliably assess postoperative refractive errors, especially in patients with severe refractive issues.

Abstract

Automatic refraction is commonly applied as a substitute for subjective refraction to evaluate residue refractive error after corneal refractive surgery. Previous research pooled the data from patients of different subgroups to calculate the difference between automatic and subjective refraction, which lacks clinical implications. The present research aims to investigate the difference between subjective and automatic refraction by subgroups in a large population to guide the proper use of autorefraction after corneal refractive surgery. Patients between 18 and 50 years who underwent corneal refractive surgery to correct myopia and astigmatism, including photorefractive keratectomy (PRK), femtosecond laser-assisted in situ keratomileusis (FS-LASIK), or small incision lenticule extraction (SMILE), were retrospectively enrolled. The automatic and subjective refractions examined three months postoperatively were compared in subgroups by demographics, surgical procedure, and refractive error. Of the 2180 eyes enrolled, the mean age was 27.2 ± 6.1 years. In subgroup analysis, postoperative refractive error type significantly influenced the difference between automatic and subjective refraction sphere (P <.001) and cylinder (P <.001). Postoperative hyperopic patients measured 0.33 ± 0.26 D more hyperopia in automatic than subjective refraction. In contrast, automatic refraction measured 0.49 ± 0.48 D more myopic than subjective refraction in postoperative myopic patients. Linear regression demonstrated that the sphere difference is positively associated with automatic refraction sphere in hyperopic (P <.001) and myopic (P <.001) patients. For surgical subgroups, subjective refraction measured more emmetropic than automatic refraction in postoperative hyperopic and myopic patients (P <.001, respectively). After corneal refractive surgery, the automatic refraction results deviate from emmetropia greater than subjective refraction, regardless of postoperative residue hyperopia or myopia. The difference between automatic and subjective refraction was greater in patients with more severe postoperative refractive error.

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