OPEN Contact lens & anterior eye : the journal of the British Contact Lens Association | 14 Nov 2012
P Gifford, T Cannon, C Lee, D Lee, HF Lee and HA Swarbrick
PURPOSE: To investigate differences in ocular aberrations induced by centre-near multifocal soft contact lenses (SCL) relative to single vision SCLs and their effect on contrast sensitivity function (CSF). METHODS: Ocular aberrometry was measured in 18 cyclopleged subjects (19-24 years) while wearing Ciba Air Optix low (AOlow) and high (AOhigh) add, Bausch & Lomb PureVision low (PVlow) and high (PVhigh) add multifocals, and a Bausch & Lomb PureVision single vision (PVsv) control with the same -3.00D distance back vertex power. Zernike polynomials were scaled to 4, 5 and 6mm pupils. CSF was measured at equivalent distances of 6m, 1m and 40cm while fully corrected with spherical trial lenses at 6m. RESULTS: AOlow, AOhigh and PVhigh induced a negative shift in primary spherical aberration (Z12) from PVsv and all multifocal SCLs induced a positive shift in secondary spherical aberration (Z24) (all p<0.01), without significantly increasing coma. Area under the CSF (AUCSF) reduced at 40cm for all multifocals relative to PVsv (p<0.05), but was not significantly different at 6m or 1m. A moderate correlation (r=-0.80, p<0.005) was found between changes in Z12 and AUCSF at 40cm for AOhigh, with an increase in negative Z12 reducing multifocal-induced loss of CSF. CONCLUSIONS: Centre-near multifocal SCLs induced a negative shift in Z12 and a positive shift in Z24. Although CSF was unaffected at 6m and 1m it was reduced at 40cm, possibly because changes in Z12 and Z24 were not great enough to induce a significant shift in centre of focus and increase in depth of field.
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