Structural and Functional Abnormalities in Early-stage Diabetic Retinopathy.

Area of Science:

• Ophthalmology
• Diabetic Retinopathy Research
• Retinal Imaging and Function

Background:

• Diabetic retinopathy (DR) is a leading cause of vision loss.
• Early-stage DR is characterized by subtle retinal changes.
• Understanding structure-function relationships is crucial for early detection.

Purpose of the Study:

• To investigate the correlation between microperimetric (MP) sensitivity and retinal thickness in individuals with mild or no diabetic retinopathy.
• To quantify structure-function relationships in early-stage diabetic eyes.

Main Methods:

• Compared 50 non-diabetic controls with 50 type-2 diabetic subjects (25 no clinically apparent DR [NDR], 25 mild nonproliferative DR [MDR]).
• Measured MP sensitivity at 36 retinal locations (3°, 6°, 12° radii).
• Quantified total retinal thickness (TRT), inner retinal thickness (IRT), and outer retinal thickness (ORT) using optical coherence tomography (OCT) at co-registered locations.

Main Results:

• Significant reductions in TRT and IRT were observed in NDR and MDR groups compared to controls, most prominent at 3°.
• Outer retinal thickness (ORT) showed no significant reduction in diabetic groups.
• MP sensitivity was significantly reduced in both diabetic groups across all measured rings.
• Structure-function associations were generally weak, with a ~27 µm thickness reduction correlating to ~1 dB sensitivity loss in MDR.

Conclusions:

• Early retinal neurodegeneration occurs in diabetics with NDR or MDR.
• Structural deficits (retinal thinning) and functional deficits (reduced sensitivity) are present early in DR.
• The weak association suggests additional mechanisms beyond retinal thinning contribute to functional impairment in early DR.