[Visual acuity at twilight and contrast vision in patients with bifocal IOL]

After cataract extraction by phacoemulsification, the True Vista bifocal lens (group I; Storz Ophthalmics, St. Louis, Missouri, USA) was implanted in 20 eyes, and the Accurasee bifocal lens (group II; Alcon, Forth Worth, Texas, USA) was implanted in 14 eyes. Following a 4-6 month postoperative period, both groups were checked with respect to visual acuity, mesopic acuity, and thresholds of contrast under mesopic light conditions. As mean values, group I demonstrated a distance acuity without correction of 0.77 (+/- 0.17), group II of 0.73 (+/- 0.14); the average near acuity without correction in group I was 0.84 (+/- 0.17), and in group II, 0.85 (+/- 0.15). The near acuity, with distance correction only, was determined to be 0.94 (+/- 0.09) in group I, and 0.91 (+/- 0.01) in group II. Examination of mesopic visual acuity by means of the Mesoptometer II (Oculus Company, Dutenhofen) revealed 0.25 (+/- 0.08) for the True Vista bifocal lens, and 0.26 (+/- 0.07) for the Accurasee bifocal lens. Under reduced field luminance, both groups of lenses showed comparable results while testing contrast thresholds were under 0.1 cd/m2; under 0.032 cd/m2 and 0.1 cd/m2 with permanent glare, however, group I demonstrated a slight advantage.