title: The Effect of Light Level and Small Pupils on Presbyopic Reading Performance.
abstract: OBJECTIVE
  To examine the impact of small pupils and light levels on reading performance of distance-corrected presbyopes. To determine whether small pupils would enable presbyopes to read at near even at low light levels.
  
  
  METHODS
  To establish the lower range of text luminances, we quantified the space-averaged luminance of text in nine different artificially lit interior environments, and examined the impact of the text characters on space-averaged luminance of electronic and printed displays. Distance and near reading speeds of 20 presbyopes (ages 40-60 years) were measured while viewing through artificial pupils (diameters 1-4.5 mm), natural pupils, or with a multifocal contact lens. Space-averaged text luminance levels varied from 0.14 to 140 cd/m2 (including the range of measured environmental text luminances).
  
  
  RESULTS
  Adding black text to a white computer display or paper reduces luminance by approximately 15% to 31%, and the lowest encountered environmental text luminance was approximately 2 to 3 cd/m2. For both distance and near reading performance, the 2- to 3-mm small pupil yielded the best overall reading acuity for space-averaged text light levels ≥ 2 cd/m2. The 2- to 3-mm artificial pupils and the multifocal contact lenses both enabled maximum or near-maximum reading speeds for 0.5 logMAR characters at distance and near, but with natural pupils, reading speeds were significantly reduced at near.
  
  
  CONCLUSIONS
  Although photon noise at low luminance reduces the visual benefits of small pupils, the benefits of 2- to 3-mm artificial pupils are sufficient to enable >80% of distance-corrected presbyopes to read proficiently at near, even at the lowest text luminances found in interior environments.
authors: Indiana University, School of Optometry, Bloomington, Indiana, United States.
authors: Renfeng
authors: R
authors: Xu
authors: Allergan, Irvine, California, United States.
authors: Daniel
authors: D
authors: Gil
authors: Allergan, Irvine, California, United States.
authors: Mohammed
authors: M
authors: Dibas
authors: Allergan, Irvine, California, United States.
authors: William
authors: W
authors: Hare
authors: Indiana University, School of Optometry, Bloomington, Indiana, United States.
authors: Arthur
authors: A
authors: Bradley
mesh_terms: D000328:Adult; D003261:Contact Lenses; D005139:Eyeglasses; D005260:Female; D006801:Humans; D008029:Lighting / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015877:Miosis / Q000503:physiopathology*; D011305:Presbyopia / Q000503:physiopathology*; D011680:Pupil / Q000502:physiology*; D011932:Reading; D015348:Vision, Binocular / Q000502:physiology*; D014792:Visual Acuity