Abstract
Purpose: :
To determine the edema index (EI) values of the Heidelberg Retina Tomograph (HRT) in patients with diabetes and in normal controls.
Methods: :
The sample comprised 4 groups. G1: 51 non-diabetic controls (mean age 52.7yrs, SD 8.5); G2: 66 patients (54.2yrs, 8.2) with diabetes but no clinically visible retinopathy; G3: 66 patients (56.7yrs, 7.5) with hard exudates and/or microaneurysms within the macular but no clinically visible diabetic macular edema (DME); G4: 50 patients (58.6yrs, 7.1) with pre-treatable DME. Each patient had on average 3 scans acquired with the Heidelberg Retinal Tomograph using the Retina Module. The Early Treatment Diabetic Retinopathy Study grid was used to assess EI values within 9 zones arranged concentrically and centred on the fovea. An expert assessor masked to the status of each patient also subjectively assessed each zone for edema using the topographic HRT edema index maps.
Results: :
The average EI (range for the 9-zones) for G1 was 1.13 (1.06-1.22), for G2 was 1.24 (1.17-1.32), for G3 was 1.28 (1.20-1.37) and for G4 was 1.31 (1.17-1.43). Central zones for all diabetic groups had significantly higher EI values compared to controls (p<0.014). G2 had 4 of 9, G3 had 6 and G4 had 7 zones with elevated EI compared to controls. Subjective assessment of edema maps detected retinal edema for at least one sector in 4% of G1, 27% of G2, 57% of G3 and 79% of G4 patients.
Conclusions: :
EI values were elevated in patients with diabetes. There was a progressive increase in EI with worsening retinopathy. Subjective assessment also showed a progressive increase in the detection of edema with worsening retinopathy.
Keywords: edema • diabetic retinopathy • imaging/image analysis: clinical