Abstract
Purpose::
To evaluate the relative variability of two different edema parameters using HRT III (Heidelberg Engineering, Heidelberg, Germany) edema index and the retinal tickness of OCT (Zeiss, Germany).
Methods::
Twenty eyes of 10 consecutive patients with diabetic macular edema (DME) were recruited. Each study eye underwent refraction,visual acuity (Early Treatment of Diabetic Reinopathy Study charts ), pupillary dilation , assessment of lens opacity (using the Lens Opacity Classification System III -LOCS III-), stereo fundus biomicroscopy, fluorangiography with with the Heidelberg Retinal Angiograph (HRA, Ottobrunn, Germany), Edema Index Analysis with HRT III and OCT. The clinical gold standard of stereo fundus biomicroscopy was used throughout the study. All the patients were recruited because showed the same visual acuity of 16/20 and the same angiographic pattern valued by one of the retinal specialist . The foveal average tickness and the edema index were considered.
Results::
The patient showed comparable lens clarity , refraction and the same angiographic pattern.The average and standard deviation for Edema Index was 2,98 and 1,38 respectively. The average and standard deviation for OCT foveal Tickness was 392,8 micron and 111,5 micron respectively. The Coefficience of variation (COV) was calculated for each group of data and were 46% for the edema index obtained with HRT III and 28% for the retinal tickness obtained with OCT.
Conclusions::
Both the HRT III and OCT were able to identify DME objectively.E ach instrument used distincively different methodology to assess the presence of edema and give different quantitative values. Considering the foveal function and the angiographic pattern equal and comparable among all the patient, the relative variabilty in the series of values was higher for the Edema Index than for the foveal Tickness (46% vs 28%).
Keywords: diabetic retinopathy • edema • imaging/image analysis: clinical