Studies on Contrast Visual Acuities in Normal, Cataractous and Pseudophakic Eyes

抄録

Contrast sensitivity and glare sensitivity are often abnormal in cataract patients. However, despite significant subjective complains, relatively good visual acuities are obtained with high-contrast optotypes. Using Variable Contrast Visual Acuity Charts with contrast levels of 90, 15, and 2.5% and reverse polarity of 90% contrast, contrast visual acuities were measured in 24 normal subjects (40 eyes) (Landolt visual acuity ≥1.0); 28 cataract patients (40 eyes)(Landolt visual acuity ≥0.6); and 75 patients (100 eyes) [best-corrected Landolt visual acuity ≥0.8 after intraocular lens (IOL) implantation]. The cataract group experienced the greatest decrease of contrast visual acuity when the high-contrast chart (chart 1) measurements were compared with the 15% (0.71 vs 0.52-0.64 octave) and the 2.5% contrast charts (1.75 vs 1.21-1.48 octaves), followed by the IOL group, and the normal subjects. In the cataract group, 23/40 eyes (57.5%) showed better contrast visual acuity with chart 4 than chart 1. Although much less in frequency, 28/100 (28%) eyes with IOLs also showed better contrast acuity measured with chart 4 than with chart 1. In addition to high-contrast optotypes, acuity measurements using intermediate-to low-contrast optotypes, combined with the reverse polarity chart, seem effective to analyze visual disabilities caused by early cataract. The pattern of the contrast acuity profile of the IOL patients was comparable to normal subjects, but the glare effect still existed after IOL implantation, though to a lesser degree than in cataractous eyes.