The Effect of Near Addition Lenses on Accommodative Response

Purpose. Progressive addition lenses (PAL) have been shown to be effective in slowing down myopia progression in some patients. It has been proposed that the near lenses work by reducing the patient’s lag of accommodation. In this study, we investigate the difference in accommodative responses in subjects with and without near addition lenses under both monocular and binocular viewing conditions. Methods. Eight optometry students (average age of 25.3 ± 3.5 years) participated in this study. The averages of refractive errors of these subjects were -2.53 ± 1.40 D (OD) and -2.66 ± 1.51 D (OS), respectively. The accommodative responses with and without +2.00 D addition lens were measured with a Canon R-1 optometer. Under monocular viewing conditions, the subject\u27s right eye viewed a target through a Badal optical system and the left eye was occluded. Accommodative responses were measured from 0 D to 8 D in 1 D intervals. Under binocular viewing conditions, the target was placed at 40 cm from the subject and the accommodative responses were measured from the subject\u27s right eye. Discussion. The accommodative response with +2.00 D lens under monocular viewing condition did not follow the predicted effect, that the accommodative response would be shifted up 2 D. This result could be explained by the accommodative system being a negative feedback system. This theory states that a certain amount of accommodative response error is necessary for maintaining a steady state accommodative response. Studies on PALs slowing myopia progression have been based on the belief that the blur image on the retina might cause an elongation of the axis of the eye and that near addition lens might help reduce retinal blur at near. However, our results suggest that the near addition lens may not improve retinal defocus. More importantly, for some subjects, it may even increase the retinal blur, having a negative impact on refractive error development. Grants. This study is supported by NSU grant PSFA#335338 and a grant from CIBA Vision