Comparison of visual acuities at different distances and defocus curves

Purpose: To evaluate how visual acuities at different distances correlate with results from defocus curves. Setting: Department of Ophthalmology and Institute of Medical Physics, University of Vienna, Medical School, Vienna, and Department of Ophthalmology, Krankenhaus St. Pölten, St. Pölten, Austria. Methods: This study comprised 15 eyes of 14 patients with a mean age of 67.9 years ± 9.7 (SD) with a monofocal silicone intraocular lens (911A, Pharmacia). The best corrected distance visual acuity was determined at viewing distances of 6 m, 2 m, 1 m, 67 cm, 50 cm, 40 cm, and 33 cm using logMAR charts. Defocus curves were then evaluated from −3.0 to −0.5 diopter (D) at 0.5 D increments from the best distance correction at a viewing distance of 6 m. Results: The mean distance visual acuity was logMAR 0.08 ± 0.07. The visual acuity graph from the testing at different distances was above the defocus graph at all testing points. Comparison of the visual acuity results from the 2 tests revealed statistically significant differences in the range from 2 m (–0.5 D) to 33 cm (–3.0 D). Conclusion: Results of defocus curves disregard the diminutions of minus glasses, the normally restricted viewing distance to 6 m for distance acuity determination, and in particular the physiological miosis caused by the near-point reaction.