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Haiyan Wang, Jay Chhablani, Lingyun Cheng, William R. Freeman; The Characteristics Of Diabetic Microaneurysms In Spectralis Optic Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1277.
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To evaluate the anatomical depth location and sizes of diabetic microaneurysms in eyes with diabetic maculopathy who underwent simultaneous fluorescein angiography and spectral domain OCT.(Spectralis, Heidelberg engineering).
The depth and distribution of diabetic microaneurysms has not been well studied. We have observed that a significant number of such lesions are present in the outer retina. We used simultaneous Spectral Domain OCT and fluorescein angiography to co-localize microaneurysms in eyes with diabetic retinopathy and to determine the retinal layers and depth at which such microaneurysms are located. We studied 134 microaneuryss of 72 eyes. This was a consecutive case series of diabetic eyes in which mocroaneurysms were demonstrated by fluorescein angiography. We analyzed all lesions which had a simultaneous horizontal or vertical SD OCT scan thru the apparent center of the vascular aneurysm. We determined the distance from the center of the aneurysm to the retinal surface and the RPE layer. In addition measurements of microaneurysm size were also performed using OCT software (Heidelberg Spectralis, Vista, Ca.) Two masked observers performed all measurements.
The correlation between the two observers for microaneurysm dimensions, distance to ILM and RPE layer ranged from 93 to 97%; a high concordance. The distance from the microaneurysm center to the retina ILM was 123 micron± 37 microns. The median macular thickness at the location of the aneurysm was 341 ± 85 microns. A total of 23% of the aneurysms were in the outer half of the retina (over 150 microns from the retinal surface). The outer diameter of aneurysms was 121±43 microns and the inner diameter was 71±42 microns.
Despite classical histopathological studies suggesting that diabetic microaneurysms are present near the surface of the retina, the typical aneurysm is located at the junction of the inner and middle third with fully a quarter located in the outer retina. On angiography, these lesions are perfused via the retinal vessels. The reason for the discrepancy between in vivo OCT analysis and classical histopathological work is unknown but may be due to sampling issues. The idea that one can focus retinal laser beams on the retinal surface to assist in selectively photocoagulate aneurysms may be spurious. Coagulation of aneurysms is likely due to either pure thermal absorption by hemoglobin or is secondary to absorption of the laser energy by the RPE with spread towards the middle retinal layers.
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