Abstract
Purpose:
The Tecnis® multifocal intraocular lens (IOL) has 2 focal points for distance (6m) and near (33cm) vision. Visual acuity is typically poorer at intermediate distances between these focal planes. This study will determine: 1) the effect of distance refractive outcome on near, intermediate, and distance vision with the Tecnis multifocal IOL, and 2) whether intermediate vision with a multifocal IOL is derived from the distance or near focus.
Methods:
78 eyes from 40 patients were divided into 3 groups by spherical equivalent distance refraction: myopic (MY) = -0.13D to -0.75D (n=21), emmetropic (EM) = plano (n=28), and hyperopic (HY) = +0.13D to +0.63D (n=29). At ≥6 months postoperative, uncorrected visual acuity (VA) was measured at 40cm, 63cm, 1m, and 6m. VA was also measured with +0.5D and -0.5D trial lens over-refraction at 63cm and 1m to determine if near or distance focus was used for intermediate vision. If +0.5D improved and -0.5D worsened VA then distance focus was responsible for intermediate acuity. If the opposite occurred then intermediate vision was derived from the near focus.
Results:
Mean refraction was -0.40±0.20D for MY group and +0.31±0.17D for HY group. No significant difference in LogMAR VA between study groups was found at 40cm (MY=0.15±0.09, EM=0.08±0.13, HY=0.14±0.11, p=0.06) or 63cm (MY=0.34±0.10, EM=0.34±0.15, HY=0.34±0.17, p=0.97). At 6m there was a borderline trend for inferior VA in the HY group (MY=0.08±0.07, EM=0.07±0.09, HY=0.12±0.09, p=0.05). At 1m the MY group had superior VA (MY=0.20±0.14, EM=0.33±0.13, HY=0.43±0.13, p<0.001). Trial lens testing at 1m showed that intermediate VA was from the distance focus for all three groups. At 63cm, MY intermediate vision was more commonly derived from distance focus while EM and HY intermediate vision was more commonly derived from near focus.
Conclusions:
Intermediate vision at 1m is superior in patients with mild myopia (-0.4D) relative to emmetropia or mild hyperopia, without significantly compromising distance or near vision. Intermediate vision at 1m is mostly derived from distance focus, not near focus as previously presumed. Overall visual function with a multifocal IOL is objectively greater with mild postoperative myopia.
Keywords: 445 cataract •
567 intraocular lens