Correlation between microaneurysms and retinal thickness in diabetic macular edema.

Purpose: Microaneurysms commonly are believed to be related causally to retinal thickening in diabetic retinopathy, especially by leaking. The hypothesis that thicker areas of retina in diabetic retinopathy have more microaneurysms per unit area than areas that are not as thick was tested.

Methods: Retinal thickness analysis was performed with a prototype instrument for 27 eyes of 27 diabetic patients and 22 normal eyes of 22 healthy subjects. Maps of retinal thickness were created, and microaneurysms were counted in zones having four levels of retinal thickness.

Results: There was no increase in either total microaneurysms or apparent leaking microaneurysms per unit area with increasing levels of retinal thickness (P = 0.77 and 0.87, respectively).

Conclusion: Some microaneurysms may not cause thickening, or other factors may contribute to retinal thickening in diabetic retinopathy. The results may have implications on the pathogenesis of diabetic macular edema.