Measurements of optic disk size with HRT II, Stratus OCT, and funduscopy are not interchangeable.
OBJECTIVE
To assess the interchangeability of optic disk size measurements using slit-lamp funduscopy, optical coherence tomography (OCT-3), and confocal scanning laser ophthalmoscopy (HRT-II) in clinical practice.


METHODS
Prospective nonrandomized clinical study.


METHODS
Measurements of vertical disk diameter (VDD) were obtained with the three methods. Disk area was obtained from OCT and HRT printouts. True agreement between methods in measuring VDD was assessed using Bland-Altman graphs and 95% limits of agreement (LoA). Disks were classified as small, average, or large, and agreement between methods in this classification was assessed using kappa statistics.


RESULTS
Forty-eight patients were enrolled (mean age 53.4 +/- 14.3 years). VDD (mean +/- SD) was 1.58 +/- 0.15, 1.70 +/- 0.22, and 1.90 +/- 0.24 mm with funduscopy, HRT, and OCT, respectively. Very large LoA were observed: -0.29 to 0.70 mm for OCT and HRT, -0.07 to 0.71 mm for OCT and funduscopy, and -0.29 to 0.53 mm for HRT and funduscopy. There was poor agreement (kappa < 0.4) in classification of disk size as small, average, or large whether disk diameter or area was compared and using two definitions of disk size.


CONCLUSIONS
We observed a large range of differences in estimating disk size with HRT, OCT, and funduscopy. This precludes interchangeable use of these measurements in clinical practice, and does not allow simple conversion formulas to be proposed. In addition, there is poor agreement between these methods in classifying disk size as small, average, or large. At present, estimation of both absolute and relative disk size can only be defined separately for each measurement modality.
Barkana
Yaniv
Y
Department of Ophthalmology, The New York Eye and Ear Infirmary, New York, New York 10003, USA.
Harizman
Noga
N
Gerber
Yariv
Y
Liebmann
Jeffrey M
JM
Ritch
Robert
R
D000886:Anthropometry; D001837:Body Weights and Measures; D005260:Female; D005901:Glaucoma / Q000175:diagnosis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009887:Ophthalmoscopy / Q000379:methods*; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D011446:Prospective Studies; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods*