Comparison between laser scanning tomography and computerised image analysis of the optic disc
a Department of
Ophthalmology Queen's Medical Centre, University of Nottingham, b Glaucoma Service, Wills
Eye Hospital, Jefferson Medical College, Philadelphia, PA, USA, c Retina Service, Wills Eye Hospital,
Jefferson Medical College, Philadelphia, PA, USA
Correspondence to: Augusto Azuara-Blanco, MD, Department of Ophthalmology, B-Floor, South Block, Queen's Medical Centre, University Hospital, Nottingham NG7 2UH.
Accepted for publication 22 September 1998
AIMS
To study the
interchangeability of the measurements of the optic disc topography
obtained by one computerised image analyser and one confocal laser
tomographic scanner.
METHODSOne eye of 28 patients with glaucoma or glaucoma suspects was studied. All cases had
simultaneous stereoscopic disc photographs taken with the fundus
camera Topcon TRC-SS and optic disc examination with the Heidelberg
retina tomograph (HRT) during the same visit. The optic disc
photographs were digitised and analysed with the Topcon ImageNet (TI)
system. Three variables of the optic disc topography provided by the TI
and the HRT were comparedcup volume (CV), rim area (RA), and cup area
to disc area ratio (CA/DA).
RESULTSThe mean
values of CV and RA provided by the TI (0.52 (SD 0.32) mm3
and 1.58 (0.39) mm2, respectively) were greater (p<0.01)
than the mean values of CV and RA determined by the HRT (0.32 (0.25)
mm3, and 1.33 (0.47) mm2, respectively). The
mean value of CA/DA provided by the TI (0.42 (0.14)) and the HRT (0.42 (0.18)) was similar (p=0.93). Correlation coefficients between
measurements obtained by the two methods ranged from 0.53 to 0.73.
CONCLUSIONThere was a
significant discrepancy in the measurements of rim area and cup volume
of the optic disc obtained by a computerised image analyser and a laser
scanning tomograph.
© 1999 by British Journal of Ophthalmology
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