title: Does optometrists' self-reported practice in glaucoma detection predict actual practice as determined by standardised patients?
abstract: OBJECTIVE
  Questionnaires are commonly used as a proxy measure of clinical practice; however their application in a variety of healthcare settings has found significant self-reporting bias. The aim of this study is to estimate the validity of self-reporting as a measure of optometrist case-finding practice for glaucoma and the appropriate referral of suspects.
  
  
  METHODS
  Two complementary approaches were used: (1) a sample of optometrists (N=34) on an ophthalmic list in West London were visited incognito by Standardised Patient (SP) volunteers aged over 54 who were trained to identify the components of a standard Sight Test. Optometrists from the same list were then invited to participate in a structured face-to-face interview regarding their case finding practice for glaucoma. The findings from the two sources were compared. (2) as part of a national glaucoma survey of optometrists, respondents (N=1264) were asked in a free text question for the information that they would include in a referral letter for suspect glaucoma. The responses were compared to the content of a sample of glaucoma referral letters (N=571) obtained from consultant ophthalmologists across the UK. In each case, the degree of correspondence ('match') between reported practice and actual practice was assessed by chi-square analysis.
  
  
  RESULTS
  For the SP study there was incomplete correspondence between the questionnaire and SP reports in several areas e.g. questions relating to a complete history and symptoms, measurement of intra-ocular pressure and visual fields. Complete correspondence was found for questions asking about the routine assessment of ocular health and refraction. For the referral study, correspondence between survey findings and referral letters was obtained for IOP only. No correspondence was found for disc assessment, visual fields or family history of glaucoma.
  
  
  CONCLUSIONS
  The overall findings from both studies indicate that self-reported clinical practice questionnaires overestimate routine tests undertaken by optometrists in practice. Although there was a good correspondence for mandatory tests, correspondence was poor for discretionary tests. These findings should be borne in mind in all questionnaire studies that report current practice in glaucoma case-finding.
authors.affiliation: Glaucoma Unit, Moorfields Eye Hospital, London, UK.
authors.forename: Julia
authors.initials: J
authors.lastname: Theodossiades
authors.forename: Joy
authors.initials: J
authors.lastname: Myint
authors.forename: Ian E
authors.initials: IE
authors.lastname: Murdoch
authors.forename: David F
authors.initials: DF
authors.lastname: Edgar
authors.forename: John G
authors.initials: JG
authors.lastname: Lawrenson
mesh_terms: D000368:Aged; D002983:Clinical Competence; D015709:Correspondence as Topic; D005901:Glaucoma / Q000175:diagnosis*; D006801:Humans; D008875:Middle Aged; D009907:Optometry / Q000379:methods / Q000592:standards*; D016544:Patient Simulation; D011364:Professional Practice / Q000592:standards* / Q000706:statistics & numerical data; D012017:Referral and Consultation / Q000592:standards; D011795:Surveys and Questionnaires; D006113:United Kingdom