title: A comparison of cup-to-disc ratio estimates by fundus biomicroscopy and stereoscopic optic disc photography in the Tema Eye Survey.
abstract: PurposeTo determine if there are systematic differences in cup-to-disc ratio (CDR) grading using fundus biomicroscopy compared to stereoscopic disc photograph reading.MethodsThe vertical cup-to-disc ratio (VCDR) and horizontal cup-to-disc ratio (HCDR) of 2200 eyes (testing set) were graded by glaucoma subspecialists through fundus biomicroscopy and by a reading center using stereoscopic disc photos. For validation, the glaucoma experts also estimated VCDR and HCDR using stereoscopic disc photos in a subset of 505 eyes that they had assessed biomicroscopically. Agreement between grading methods was assessed with Bland-Altman plots.ResultsIn both sets, photo reading tended to yield small CDRs marginally larger, but read large CDRs marginally smaller than fundus biomicroscopy. The mean differences in VCDR and HCDR were 0.006±0.18 and 0.05±0.18 (testing set), and -0.053±0.23 and -0.028±0.21 (validation set), respectively. The limits of agreement were ~0.4, which is twice as large as the cutoff of clinically significant CDR difference between methods. CDR estimates differed by 0.2 or more in 33.8-48.7% between methods.ConclusionsThe differences in CDR estimates between fundus biomicroscopy and stereoscopic optic disc photo reading showed a wide variation, and reached clinically significance threshold in a large proportion of patients, suggesting a poor agreement. Thus, glaucoma should be monitored by comparing baseline and subsequent CDR estimates using the same method rather than comparing photographs to fundus biomicroscopy.
authors.affiliation: Department of Ophthalmology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Mwanza
authors.affiliation: Glaucoma Associates of Texas, Dallas, TX, USA.
authors.forename: D S
authors.initials: DS
authors.lastname: Grover
authors.affiliation: Department of Ophthalmology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: D L
authors.initials: DL
authors.lastname: Budenz
authors.affiliation: Duke University Eye Center, Durham, NC, USA.
authors.forename: L W
authors.initials: LW
authors.lastname: Herndon
authors.affiliation: Moorfields Eye Hospital, London, UK.
authors.forename: W
authors.initials: W
authors.lastname: Nolan
authors.affiliation: Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
authors.forename: J
authors.initials: J
authors.lastname: Whiteside-de Vos
authors.affiliation: Peninsula Eye Hospital, Redcliffe, Queensland, Australia.
authors.forename: G
authors.initials: G
authors.lastname: Hay-Smith
authors.affiliation: Bascom Palmer Eye Institute, University of Miami, Miami, FL, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Bandi
authors.affiliation: Department of Ophthalmology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: K A
authors.initials: KA
authors.lastname: Bhansali
authors.affiliation: Department of Ophthalmology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Forbes
authors.affiliation: Bascom Palmer Eye Institute, University of Miami, Miami, FL, USA.
authors.forename: W J
authors.initials: WJ
authors.lastname: Feuer
authors.affiliation: National Institute for Health Research, Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital, London, UK.
authors.forename: K
authors.initials: K
authors.lastname: Barton
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005901:Glaucoma / Q000175:diagnosis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009887:Ophthalmoscopy / Q000379:methods*; D009898:Optic Disk / Q000000981:diagnostic imaging*; D009901:Optic Nerve Diseases / Q000000981:diagnostic imaging*; D061848:Optical Imaging / Q000379:methods*; D010781:Photography / Q000379:methods; D015203:Reproducibility of Results; D066167:Slit Lamp