Apparent accommodation and depth of field in pseudophakia

Purpose: To assess depth of field in phakic and pseudophakic eyes to explain good distance and uncorrected near visual acuity in pseudophakic eyes. Setting: Department of Ophthalmology, University of Otago Medical School, Dunedin, New Zealand. Methods: Depth of field was measured in pseudophakic (n = 10) and phakic (n = 10) eyes for both near and distant targets. Test conditions included cycloplegia and a constant pupillary aperture using a soft contact lens with a central artificial pupil diameter of 2.5 mm. Results: There was no statistically significant difference between phakic and pseudophakic eyes for any test. Depth of field for near visual acuity was +/-0.85 diopters (D), but amplitude of legibility was +/- 1.94 D. Depth of field for distance visual acuity was between 0.25 and 0.50 D in 85% of eyes. Conclusion: In the absence of astigmatism and disease, a pseudophakic eye with -0.75 D of myopia can expect to achieve 20/30 uncorrected distance acuity and read N5 unaided if the pupil is approximately 2.5 mm.