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Distance corrected near VA gains with aspheric monofocal IOL linked to HOAs
Improved distance corrected near visual acuity was associated with higher-order aberrations in eyes implanted with an aspheric monofocal IOL, according to a study.
The prospective study included 37 eyes of 36 patients who underwent phacoemulsification and implantation of a one-piece Tecnis ZCB00 IOL (Abbott Medical Optics) with negative spherical aberration of –0.27 µm for a 6-mm optical zone.
Researchers examined logMAR distance corrected near visual acuity, corrected near visual acuity, uncorrected near visual acuity, corrected distance visual acuity, uncorrected distance visual acuity, defocus curve and ocular and corneal higher-order aberrations (HOAs) 1 month after surgery.
Eyes were divided into two groups: distance corrected near visual acuity of 0.4 (20/50 Snellen) or better and distance corrected near visual acuity of 0.4 or worse. The researchers compared HOAs for a 4-mm pupil between groups.
Results showed that over a 4-mm pupil, mean ocular vertical coma was statistically significantly different between the two groups, at –0.038 µm in the 0.4 logMAR or better group and 0.015 µm in the 0.4 logMAR or worse group, according to the researchers.
Over a 5-mm pupil, mean ocular vertical coma was –0.083 µm in the 0.4 logMAR or better group and 0.043 µm in the 0.4 logMAR or worse group. This between-group difference in corneal vertical coma was also considered significant.
Between-group differences in other ocular HOAs and corneal HOAs were statistically insignificant, according to the researchers.
Disclosure:The authors have no relevant financial disclosures.
Perspective
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From the perspective of physiologic optics, some aberrations – especially those to which a particular subject may have already adapted neurologically – may offer a benefit, or at least a reasonable trade-off. Song, et al, have shown that increased depth of focus represents a benefit of vertical coma; other authors have shown even greater effects on the defocus curve by manipulating spherical aberration. In general, however, contrast performance peaks when all aberrations – including chromatic aberration – are eliminated. Such an artificially perfect optical system may prove impractical for humans outside of an adaptive optics laboratory.
Our goal, rather, should be versatile, comfortable and, ultimately, functional vision that allows us to navigate our world, appreciate its beauty and maximize our freedom. It’s nice if a little bit of vertical coma helps us read without fishing around for glasses. In the meantime, however, we shouldn’t lose sight of the quality of vision for the sake of convenience.