Impact of Pupil Aperture on Agreement Between Objective and Subjective Refraction

Wavefront-based objective refraction may vary with analysis aperture because larger pupils increase the contribution of higher-order aberrations. The objective of this study was to assess the agreement between objective refraction derived at simulated 3-mm and 5-mm analysis apertures and subjective refraction using the Zeiss i.Profiler Plus. This observational study included 200 adults aged 18-50 years. Objective refractive values for simulated 3-mm and 5-mm analysis apertures were derived from the same i.Profiler acquisition and did not represent physiologically measured pupil sizes after light adaptation. Subjective refraction was performed using the Zeiss Visuphor 500. Agreement was evaluated using Bland-Altman analysis. Results showed that the mean spherical equivalent refraction (SER) was -0.82 ± 1.70 D at 3 mm, -0.98 ± 1.68 D at 5 mm, and -0.67 ± 1.49 D subjectively. For SER, the 3-mm aperture showed slightly narrower limits of agreement (-0.92 to +0.62 D) than the 5-mm aperture (-1.05 to +0.43 D). For cylinder, the 5-mm aperture showed marginally narrower limits of agreement (-0.67 to +0.18 D) than the 3-mm aperture (0.72 to +0.19 D). In conclusion, the 3-mm analysis aperture showed slightly closer agreement for spherical measurements, whereas the 5-mm aperture showed marginally closer agreement for cylindrical power. These differences were small and unlikely to be clinically meaningful.