Abstract
Abstract: :
Purpose:A prospective study of objective mesurements of differences in the retinal thickness with Optical Coherence Tomography (OCT) in diabetic patients with non–significant macular edema from baseline to 18 months and to investigate whether the difference in retinal thickness correponds to the clinical evaluation of progression to clinically significant macular edema (CSME). Methods:14 eyes in 12 patients with diabetes, mean age 49.7 years of age (range 37 –56) with a mean duration of diabetes of 13 years (range 1–32 years). 3 patients had type I diabetes and 9 patients had diagnosed type II diabetes. At baseline the retinopathy level was from mild to moderate (35D to 47A) and the presence of non–significant macular edema was confirmed by a Reading Center. The EDTRS criteria were used for evaluating vísual acuity and macular edema.The retinal thickness was measured using the OCT (software A6) with the six radial lines 30 degrees apart centered around the fovea (6 mm scans). Off–line the six radial scans were analyzed by use of a user–controlled software and a macular map with linear interpolation between the radial lines was constructed. The user–controlled software allows correction for obvious artefacts and calculation of volume differences between the maps of macular thickness. Results:CSME did not develop within the 18 months in any eye. After 18 months of observation the retinal thickness had increased significantly by 0.22 mm3 (p<0.001) although no significant change was seen in visual acuity (p=0.2). Thereafter the patients were followed for additional 32 months. 4 eyes in 4 patients had macular photocoagulation treatment after the 18 months due to CSME. In one eye additional peripheral photocoagulation was given. The mean increase in volume from baseline to 18 months was larger in the 4 photocoagulated eyes than in the non–photocoagulated eyes (0.34 vs 0.16 mm3, p= 0.3). Conclusions:In diabetic eyes with non–significant macular edema, a significant increase was found in retinal volume during a 18 month study. However, only 4 of the 14 included eyes developed CSME during an additional 32 months observation time underlining the slow progression of macular edema. There was a 2–fold increase in retinal volume in the photocoagulated eyes during the 18–month study indicating that measurement of retinal volume might be an early sensitive predictive parameter for photocoagulation.
Keywords: diabetic retinopathy • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • clinical (human) or epidemiologic studies: natural history