title: Revisiting the impact of phenylephrine hydrochloride on static and dynamic accommodation.
abstract: OBJECTIVE
  Phenylephrine hydrochloride (PHCl), a commonly used mydriatic agent, causes a small but significant deterioration of accommodation. The relative roles of pharmacology and optics in this deterioration, however, remain unascertained. The study determined the combined impact of PHCl concentration (pharmacology) and pupil size (optics) on the static and dynamic characteristics of accommodation.
  
  
  METHODS
  A total of 16 emmetropic Indian adults viewed a high-contrast visual target that switched between 67 and 33 cm viewing distance (1.5D stimulus) with their right eye (left eye occluded using infrared transmitting filter) through natural pupils and through 8, 6, 4, and 1 mm diameter artificial pupils. This protocol was repeated once without PHCl and once each with 2.5%, 5%, and 10% PHCl. Consensual accommodation of the left eye was recorded using infrared photorefraction (60 Hz).
  
  
  RESULTS
  Relative to no PHCl, the horizontal pupil diameter of left eye was significantly larger (P < 0.001) and the response magnitude and peak velocity of accommodation and disaccommodation were modestly but significantly smaller (P < 0.02 for all) for all concentrations of PHCl tested. There was no significant difference in these parameters across the three drug concentrations (P > 0.4 for all). The response magnitude and peak velocity also decreased significantly with pupil diameter, at similar rates for the no PHCl and the three PHCl conditions (P < 0.001 for all).
  
  
  CONCLUSIONS
  The reduction in accommodative performance with all drug concentrations and with pupil diameter suggests independent roles of pharmacology and optics in determining accommodative performance with PHCl. The reduction in accommodative performance is, however, modest and may be clinically irrelevant in Indian eyes.
authors.affiliation: Visual Optics and Psychophysics Laboratory, Champalimaud Translational Centre for Eye Research, Prof. Brien Holden Eye Research Centre, L V Prasad eye Institute, Hyderabad, India.
authors.forename: Samrat
authors.initials: S
authors.lastname: Sarkar
authors.forename: Ali Mohammed
authors.initials: AM
authors.lastname: Hasnat
authors.forename: Shrikant R
authors.initials: SR
authors.lastname: Bharadwaj
mesh_terms: D000065:Accommodation, Ocular / Q000187:drug effects / Q000502:physiology*; D000328:Adult; D058453:Emmetropia / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D009184:Mydriatics / Q000008:administration & dosage; D009883:Ophthalmic Solutions; D010656:Phenylephrine / Q000008:administration & dosage*; D011680:Pupil / Q000187:drug effects* / Q000502:physiology; D012016:Reference Values; D014792:Visual Acuity; D055815:Young Adult
chemical_list: D009184:Mydriatics; D009883:Ophthalmic Solutions; D010656:Phenylephrine