Abstract
Purpose::
To establish an age-related database of macular edema index (E-index) values of normal eyes. To compare E-index values from images obtained from normal eyes and eyes with diabetic macular oedema.
Methods::
A total of 203 normal eyes (101 right and 102 left eyes) were imaged with a Heidelberg Retina Tomograph II (HRT II, Heidelberg Engineering, Dossenheim-Germany). The age range of subjects was 20 to 81 years (mean 44.6, SD 16.7). Three final averaged scans were acquired for each subject. The retinal module with a 1500µm radius circle divided into 9 zones was used for analysis. A total of 34 eyes with diabetic macular oedema (14 right and 20 left) from subjects with an age range from 49 to 83 years (mean 66.85, SD 10.57) were also imaged in the same manner.
Results::
The total average E-index value of all normal eyes was 1.10 (SD 0.30) with a total average reflectance tomography Standard Deviation of 16µm. A significant correlation was found for the mean E-index values and age for all zones in normal eyes (Pearson’s correlation 0.225; p = 0.030 right eyes, 0.342; p = 0.001 for left eyes). There was also a significant correlation found for mean E-index and age for the central 500µm zone in the same eyes.A subset of 33 normal eyes (mean age 61.5 SD 8.97) were compared to the 34 eyes with diabetic macular oedema (no significant difference in age between groups, unrelated t-test; p=0.13). The central 500µm zone mean E-index for the normal group was 1.21 (SD 0.43) compared with 1.86 (SD 0.89) for the diabetic macular oedema group.
Conclusions::
We found older subjects had slightly higher and more variable macular E-index values compared to younger subjects. This may be attributed to age-related changes. In subjects of a similar age, macular E-index values were higher in eyes with diabetic macular oedema compared to normal eyes. Establishing an age-related database of normal macular E-index values could help discriminate between normal and abnormal macular scans using the HRT II.
Keywords: imaging/image analysis: clinical • macula/fovea • diabetes