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Comparison of visual acuities at different distances and defocus curves
Stefan Pieh1, Christian Kellner, Georg Hanselmayer
1Department of Ophthalmology and Optometry, Medical School, University of Vienna, Vienna, Austria. stefan.pieh@univie.ac.at
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).
Conclusions:
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.