Effect Of Contrast On Near Visual Acuity With Monofocal And Multifocal Intraocular Lenses

The goal of this study was to measure the impact of contrast on near visual acuity in patients bilaterally implanted with monofocal and multifocal intraocular lens (IOL).

Single surgeon private eye clinic in Haugesund, Norway.

Eighty patients (160 eyes) implanted with a single-piece diffractive multifocal IOL (TFNT00; N= 40) or an aspheric monofocal IOL (SN60WF; N=40) in both eyes were recruited. Binocular best corrected visual acuities at distance (BCDVA, 4m) and near (DCNVA, 40cm) were measured using ETDRS logMAR charts at 100% contrast. Binocular DCNVA was measured with trial lenses from +0.25D to +2.50D in 0.25D steps in both eyes while patients resolved letters on Sloan ETDRS near charts at each of the five contrast levels (100%, 50%, 25%, 10%, and 5%). Mean add power required to achieve a threshold near VA of 20/32 (0.20 logMAR) was calculated.

Mean binocular BCDVA was similar between the groups. Mean binocular DCNVA (logMAR) at 100% contrast were: TFNT00: -0.02, SN60WF: 0.42 and SN60WF +2.50D add: 0.09. There was a systematic decline in DCNVA with decreasing contrast with steeper slopes for low contrast (<25%) in both groups.

With SN60WF, the magnitude of add power required to resolve 20/32 (0.20 logMAR) was > 1.00D for ≤25% contrast. For TFNT00, the binocular DCNVA was ≤0.20 logMAR for contrasts ≥25% with no add power. At low contrast (≤10%), no significant gain in DCNVA with add powers was observed.

The results demonstrate excellent near visual acuity with TFNT00 than SN60WF. With decreasing contrast, the SN60WF required a larger magnitude of add power to retain near visual acuity vs. TFNT00. Good near visual acuity (20/32 or better) with TFNT00 at ≥25% contrast may provide adequate acuity reserve for reading low contrast prints.