Hj. Zambarakji et al., VOLUMETRIC-ANALYSIS OF EARLY MACULAR EDEMA WITH THE HEIDELBERG RETINATOMOGRAPH IN DIABETIC-RETINOPATHY, Ophthalmology, 105(6), 1998, pp. 1051-1059
Objective: This study describes a new method for the quantification of
diabetic macular edema by volumetric analysis with the Heidelberg Ret
ina Tomograph (HRT) scanning laser ophthalmoscope. Design: Topographic
images of the macula were obtained in 25 consecutive patients who fit
ted the inclusion criteria. Twenty age-matched control subjects were r
andomly selected for a similar examination. Participants: Twenty norma
l control eyes and 32 eyes of 25 patients with diabetes mellitus were
studied. Intervention: Patients with diabetes were examined by HRT and
slit-lamp biomicroscopy with a contact lens. On HRT, the volumes abov
e reference plane bound by three consecutive circles centered at the f
ovea (diameter, 1, 2, and 3 mm) were measured. Measurements were repea
ted three times in a masked fashion, and the mean measurements were us
ed for the analysis. Main Outcome Measures: Visual acuity, macular ede
ma, and volume above reference plane were measured. Results: There wer
e 19 diabetic eyes with clinical macular edema (deemed positives) and
13 without edema (deemed negatives). Diabetic eyes with macular edema
had statistically greater volumes above reference plane than did diabe
tic eyes without edema (P < 0.001) and greater than the control eyes (
P < 0.001) for all three circles. There was no statistically significa
nt difference between volumes measured in eyes without macular edema a
nd control eyes (P = 0.42 for the 1-mm diameter circle; P = 0.72 for t
he 2-mm diameter circle; and P = 0.19 for the 3-mm diameter circle). F
or the two smallest circles only, the sensitivity of the HRT was 78.94
%, and the specificity was 84.61%. None of the patients missed on the
two smallest circles would have been positively identified on the 3-mm
diameter circle. Conclusion: The HRT can detect and quantify macular
edema in diabetes by volumetric analysis with the method the authors h
ave described. It is sufficient to measure the volumes above reference
plane of two circles centered on the fovea and measuring 1 and 2 mm i
n diameter because the 3-mm diameter circle does not increase the syst
em's sensitivity.