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Br J Ophthalmol 2000;84:894-898 doi:10.1136/bjo.84.8.894
  • Original Article
    • Clinical science

Pharmacological mydriasis and optic disc examination

  1. James F Kirwana,
  2. Pieter Gouwsb,
  3. Anne E T Linnellb,
  4. Jonathan Crowstonc,
  5. Catey Buncec
  1. aDepartment of Epidemiology and International Eye Health, Institute of Ophthalmology, London EC1V 9EL, bThe Roy Harfitt Eye Unit, Sutton Hospital, Sutton SM2 5NF, cMoorfields Eye Hospital, London EC1V 2PD
  1. Mr Kirwan jfkirwan{at}ucl.ac.uk
  • Accepted 24 February 2000

Abstract

AIM To determine whether pharmacological mydriasis leads to a significant difference in interobserver agreement of optic disc measurement compared with examination without mydriasis.

METHOD 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.

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