| Abstrakt: |
The effectiveness of multifocal correction upon presbyopic near and intermediate visual resolution performance was measured using Landolt ring targets. Decimal resolution acuity was determined at eight viewing distances from 36.4 cm to 1 m for non-presbyopic controls, presbyopic subjects corrected for infinity, and for presbyopic subjects corrected by bifocals, trifocals and Varilux 2 multifocal lenses. Non-presbyopic subjects demonstrated a resolution ability of 1.9 decimal acuity or better at all viewing distances. Presbyopic subjects corrected for distance but without multifocal addition showed a precipitous decrease in visual acuity to less than .50 decimal acuity at distances closer than 58 cm. When corrected by conventional straight-top bifocal lenses, these individuals regained a maximum of 1.8 decimal acuity at 40 cm, but demonstrated a significant depression of intermediate visual acuity to about .90 between 44 and 58 cm. Correction with straight top trifocal lenses and Varilux 2 progressive addition lenses enabled presbyopic subjects to resolve acuity targets at the level of 1.6 decimal acuity at all test distances. |
