Influence of Light Wavelength and Optotype Size on Accommodative Response and Aberrometric Changes Across the Adult...

To analyse the effects of chromatic light (white, blue, red and green) and stimulus size (6/6 and 6/12) on pupil constriction, Zernike coefficients and the accommodative response curve using wavefront aberrometry across a wide age range of healthy subjects.

One hundred and sixty-four right eyes from participants aged 20-75 years were evaluated. All subjects showed normal near visual function for their age. Wavefront aberrations were measured under scotopic conditions using the IRX3 aberrometer. Accommodation was induced from 0 to 10 D in the younger group and from 0 to 5 D in the full sample. Stimuli varied in colour and size. Pupil diameter and Zernike coefficients were analysed, rescaling all maps to a 3.00 and a 3.65 mm pupil, respectively.

Mean pupil diameter ± standard deviation decreased progressively with increasing accommodative demand by 0.51 ± 0.06 mm in the full sample (0-5 D) and by 2.09 ± 0.11 mm in the younger group (0-10 D). The greatest changes were observed under white light and larger stimuli. The Zernike component C(2,0) varied significantly across all filters, optotype sizes and in both the total (p < 0.003) and the younger (p < 0.0009) groups. However, C(4,0) showed significant changes in all conditions for the younger group (p < 0.0009), particularly at higher demands. An initial overaccommodation of approximately 1 D at baseline was followed by a progressive lag beyond 5 D, being more pronounced under red light, where the accommodative response was lowest, while white light consistently elicited the strongest response. Larger stimuli induced greater responses than smaller ones, especially at high demands.

Accommodation efficiency varies with wavelength and stimulus size: white and blue lights triggered greater pupil constriction and accommodation than red and green, with corresponding changes in defocus and spherical aberration. Small stimuli improved low-demand responses, while larger ones were more effective at higher demands.