Abstract
Purpose: All forms of presbyopic vision correction entail some compromise in either depth of focus, field of view, binocular vision or image quality. Multifocal contact lenses with aspheric surfaces alter local power resulting in formation of simultaneous images. Aspheric optics increase depth of focus but induce aberrations and alter image quality. The relationship between induced aberrations and visual performance was compared between centre-distance and centre-near multifocal lenses and a single vision lens.
Method: Single vision, centre-near and centre-distance lenses with +2.50 nominal add in Comfilcon material were worn in sequence by 10 participants following cycloplegia. Aberrations were measured with the COAS aberrometer with lens on-eye and for bare eye and scaled to a 6 mm pupil. Mean spherical aberration (Z4,0) for the bare eye was +0.17 μm. High contrast visual acuity (VA) at 3 m and 40 cm was measured with an ETDRS chart scored on a letter by letter basis. The change in vision at distance and near compared to the single vision control lens was calculated.
Results: Centre-near design induced a negative shift in Z4,0 of −0.27 μm and centre-distance a positive shift of +0.24 μm. On-eye Z4,0 was significantly different between lens types (p < 0.001). Compared to the single vision lens, VA for near dropped 0.11 logMAR for centre-near and 0.24 logMAR for the centre-distance lens. Vision reduction at near was significantly correlated to the RMS of horizontal and vertical coma (r = 0.827; p = 0.03). At 3 m vision was reduced by 0.28 logMAR for centre-near and 0.18 logMAR for the centre-distance lenses but there was no significant relationship between distance vision drop and either spherical aberration or coma.
Conclusions: Individual variation in vision with multifocal CLs can be explained in part by resultant on-eye aberrations. Although all lens fits appeared clinically acceptable, decentration of inherent spherical aberration in the lens designs can induce coma which related to poorer visual performance.
Method: Single vision, centre-near and centre-distance lenses with +2.50 nominal add in Comfilcon material were worn in sequence by 10 participants following cycloplegia. Aberrations were measured with the COAS aberrometer with lens on-eye and for bare eye and scaled to a 6 mm pupil. Mean spherical aberration (Z4,0) for the bare eye was +0.17 μm. High contrast visual acuity (VA) at 3 m and 40 cm was measured with an ETDRS chart scored on a letter by letter basis. The change in vision at distance and near compared to the single vision control lens was calculated.
Results: Centre-near design induced a negative shift in Z4,0 of −0.27 μm and centre-distance a positive shift of +0.24 μm. On-eye Z4,0 was significantly different between lens types (p < 0.001). Compared to the single vision lens, VA for near dropped 0.11 logMAR for centre-near and 0.24 logMAR for the centre-distance lens. Vision reduction at near was significantly correlated to the RMS of horizontal and vertical coma (r = 0.827; p = 0.03). At 3 m vision was reduced by 0.28 logMAR for centre-near and 0.18 logMAR for the centre-distance lenses but there was no significant relationship between distance vision drop and either spherical aberration or coma.
Conclusions: Individual variation in vision with multifocal CLs can be explained in part by resultant on-eye aberrations. Although all lens fits appeared clinically acceptable, decentration of inherent spherical aberration in the lens designs can induce coma which related to poorer visual performance.
| Original language | English |
|---|---|
| Title of host publication | Contact Lens and Anterior Eye |
| Volume | 41 |
| Publication status | Published - 1 Jun 2018 |