Impact Of Contrast On Near Reading Performance With A Diffractive Trifocal Intraocular Lens

Reading is an essential skill and demonstrates functional vision in everyday life. Reading performance has been measured routinely with standardized reading charts at 100% letter contrast. Everyday reading may include text with low contrast and reading performance with low contrast visual stimuli is unclear. The goal of this study was to measure the impact of contrast on near reading performance in patients bilaterally implanted with a trifocal intraocular lens (IOL).

Single surgeon private eye clinic in Haugesund, Norway.

Forty patients (80 eyes) implanted with a single-piece diffractive trifocal IOL (TFNT00) in both eyes were recruited. Binocular uncorrected and best corrected visual acuities at distance (UCDVA and BCDVA, 4m) and near (UCNVA and DCNVA, 40cm) were measured using ETDRS logMAR charts. Patients read aloud sentences wearing their distance refractive correction binocularly. Reading speed was recorded as patients read from a Norwegian Colenbrander chart set at 40 cm. Print size ranged from 1.20 to -0.10 logMAR and five contrast levels (100%, 50%, 25%, 10%, and 5%) were tested at each print size.

The mean (SD) age of the patients was 61.6 (6.0) years. Mean (SD) of postoperative duration was 3.46 (1.24) years. Mean binocular UCDVA and BCDVA were: -0.04 and -0.08 logMAR. Mean binocular UCNVA and DCNVA were: 0.01 and -0.02 logMAR. For larger prints (≥ 0.90 logMAR), there was no impact of contrast on reading speed (mean = 203.74 words/min). There was a systematic decline in reading speed with smaller prints with steeper slopes for low contrast (≤10%). The mean reading speed maintained at high level (>80 words/min) for print sizes up to 0.20 logMAR and contrast (≥ 25%).

The results demonstrate good near visual acuity and good functional reading performance with TFNT00 trifocal at various contrast levels. Fluent reading for various print sizes is consistent with the acuity reserve provided by this trifocal at near.