title: Pharmacological mydriasis and optic disc examination.
abstract: OBJECTIVE
  To determine whether pharmacological mydriasis leads to a significant difference in interobserver agreement of optic disc measurement compared with examination without mydriasis.
  
  
  METHODS
  A cross sectional study was performed with a pair of observers examining the optic disc of two randomised groups of patients, one group before diagnostic mydriasis, and the other afterwards. Horizontal and vertical disc diameters and cup/disc ratios were measured with a 78 dioptre lens. The study was repeated with another observer pair and two further groups of patients.
  
  
  RESULTS
  In study A 86 subjects were examined in total (52 without and 34 with mydriasis). In study B 87 subjects were examined (45 without and 42 with mydriasis). The 95% limits of agreement of the cup/disc ratio measurement differences were significantly larger without mydriasis (p<0.001 for all studies (F test)). For both studies examination after mydriasis gave significantly greater agreement for vertical and horizontal cup/disc ratios. The cases with good agreement (0.1 difference or better) for vertical cup/disc ratios were 37/52 (72%) and 34 /45 (76%) without mydriasis and 33/34 (97%) and 40/42 (95%) respectively with mydriasis. Similar differences were recorded for horizontal cup/disc ratios. Disc diameter measurement results showed similar differences in study A but were not affected by mydriasis in study B.
  
  
  CONCLUSIONS
  Examination of the optic disc without pharmacological mydriasis gives significantly poorer interobserver agreement. In this study, the mean 95% limits of agreement values for all cup/disc ratio values were 0.27 for examination without mydriasis and 0.13 for examination with mydriasis. A measure outside these limits would suggest a real difference. This study indicates that mydriasis is important for reproducible clinical examination in glaucoma.
authors.affiliation: Department of Epidemiology and International Eye Health, Institute of Ophthalmology, London EC1V 9EL. jfkirwan@ucl.ac.uk
authors.forename: J F
authors.initials: JF
authors.lastname: Kirwan
authors.forename: P
authors.initials: P
authors.lastname: Gouws
authors.forename: A E
authors.initials: AE
authors.lastname: Linnell
authors.forename: J
authors.initials: J
authors.lastname: Crowston
authors.forename: C
authors.initials: C
authors.lastname: Bunce
mesh_terms: D003430:Cross-Sectional Studies; D005901:Glaucoma / Q000175:diagnosis*; D006801:Humans; D009184:Mydriatics / Q000494:pharmacology*; D015588:Observer Variation; D009898:Optic Disk / Q000033:anatomy & histology*; D011446:Prospective Studies; D011680:Pupil / Q000187:drug effects / Q000502:physiology
chemical_list: D009184:Mydriatics