title: Effect of pupil size on optical quality parameters in astigmatic eyes using a double-pass instrument.
abstract: OBJECTIVE
  To objectively determine the effects of pupil size on optical quality parameters in astigmatic eyes using a double-pass instrument.
  
  
  METHODS
  We examined twenty-two eyes of 22 healthy volunteers (mean age  ±  standard deviation, 27.1 ± 2.8 years) who had no ophthalmic diseases other than refractive errors (manifest cylinder ≤ 0.25 diopters (D)). After we fully corrected cycloplegic refraction, we created with-the-rule astigmatism of 1, 2, and 3 diopters in these eyes and then quantitatively assessed the modulation transfer function (MTF) cutoff frequency and the Strehl2D ratio with 2-, 4-, and 6-mm pupil sizes using the Optical Quality Analysis System.
  
  
  RESULTS
  The MTF cutoff frequency and the Strehl2D ratio decreased significantly as the amount of astigmatism increased at each pupil size (P < 0.001 for 2, 4, and 6 mm, analysis of variance). They also decreased significantly with an increase in pupil size at each diopter of astigmatism (P < 0.001 for 0, 1, 2, and 3 D). Multiple comparisons demonstrated a significant difference between measurements made for a 2-mm pupil and for a 6-mm pupil at each diopter of astigmatism (P < 0.001 for 0, 1, 2, and 3 D, Dunnett test) and those made for a 4-mm pupil and for a 6-mm pupil at each diopter of astigmatism (P < 0.001 for 0 D, P < 0.05 1, 2, and 3 D).
  
  
  CONCLUSIONS
  Eyes with larger pupils had lower optical quality even when they were astigmatic. It may be necessary to correct the preexisting astigmatism to acquire excellent visual performance, especially in astigmatic eyes with larger pupils.
authors.affiliation: Department of Ophthalmology, University of Kitasato School of Medicine, 1-15-1 Kitasato, Minami, Sagamihara, Kanagawa 252-0374, Japan.
authors.forename: Hidenaga
authors.initials: H
authors.lastname: Kobashi
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Kamiya
authors.forename: Kyohei
authors.initials: K
authors.lastname: Yanome
authors.forename: Akihito
authors.initials: A
authors.lastname: Igarashi
authors.forename: Kimiya
authors.initials: K
authors.lastname: Shimizu
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000473:pathology*; D003710:Demography; D005260:Female; D006801:Humans; D008297:Male; D055620:Optical Phenomena; D009907:Optometry / Q000295:instrumentation*; D009929:Organ Size; D011680:Pupil