Background: Addition lenses (adds) are frequently used to increase the accuracy of the near-vision focusing response, and may also play a role in the prevention or retardation of refractive error development. However, following the introduction of such a lens, if the accommodative response is reduced by an amount equal to the magnitude of the near add, then the resulting accommodative error (and degree of retinal defocus) would remain unchanged.
Methods: This study measured the accommodative response in 28 subjects while they viewed a near target binocularly, either through their distance refractive correction alone or this correction combined with a +0.75 D, +1.50 D, +2.00 D, or +2.50 D near add.
Results: The mean findings demonstrated a small (0.03 D) lead of accommodation to the near target through the distance correction, and monotonically increasing leads of accommodation with larger adds. Further, the additional lens power required to reduce the accommodative error to zero correlated significantly with the initial accommodative error.
Conclusions: Near addition lenses may actually increase the degree of retinai defocus for individuals who manifest small accommodative errors.