Abstract
Purpose: :
To evaluate if retinal microglia changes may be detected in vivo in eyes without and with nonproliferative diabetic retinopathy.
Methods: :
60 subjects were enrolled: 40 subjects were affected by diabetes mellitus and 20 normals served as controls. Proliferative diabetic retinopathy, previous laser photocoagulation, intraocular surgery or intravitreal injection, refractive error higher than 6 diopters, glaucoma or ocular hypertension and neurodegenerative diseases were the main exclusion criteria. One eye of each subject was used for statistical analysis. Twenty patients had no diabetic retinopathy (noDR group), 20 patients had non proliferative DR without macular edema (DR group). Full ophthalmic examination, stereoscopic fundus photography, and spectral domain-OCT (SD-OCT) were performed in all eyes. After segmentation of retinal layers by SD-OCT, the thickness of specific layers (inner limiting membrane plus retinal nerve fiber layer: ILM+RNFL; inner nuclear layer plus outer plexiform layer: INL+OPL) was quantified. SD-OCT images were also analyzed for reflectivity changes at the level of the ILM+RNFL, INL+OPL and outer nuclear layer where glial cells are located in human retina. All measurements and examinations were performed twice, by two independent masked graders.
Results: :
No statistically significant differences were found for age among all groups and for glycemic control between diabetic groups. A significant increase in thickness of INL+OPL was found in diabetic eyes (both noDR and DR) vs controls (p=0.002), confirming previous observations about macroglial activation in diabetic eyes. The inter-grader agreement was at least substantial for all measurement. In both noDR and DR eyes relatively uniform microaggregates were systematically detected at the level of ILM+RNFL, without significant difference between the two groups. Such changes were undetected in controls.
Conclusions: :
The presence of discrete microaggregates in areas corresponding to microglia, even before the appearance of clinically detectable retinopathy, may represent the in vivo sign of early microglial changes in diabetic retina. Microglial activation may be detected, as macroglial activation, by spectral domain OCT using targetted analysis. These data strongly suggests a very early reactive and degenerative processs in all glial cells of diabetic retina .
Keywords: diabetic retinopathy • retinal glia • imaging/image analysis: clinical