Experts Examine the Association Between Retinal Damage, DKD Presence in Patients With T2D

Early neurovascular retinal damage was seen among patients with type 2 diabetes (T2D), while changes were more significant in patients with diabetic kidney disease (DKD), according to results of a cross-sectional study. Findings were published in International Journal of Retinal and Vitreous.

Diabetic retinopathy (DR) constitutes the leading cause of vision loss among patients with diabetes, and duration of the disease, chronic hyperglycemia, and hypertension can all increase the risk of DR.

“The microvascular complications of diabetes affect the eyes and kidneys and are associated with different risk factors such as diabetes duration and blood pressure and lipid control,” researchers explained.

Furthermore, previous research has suggested a strong association between DR and diabetic renal neurodegeneration (DRN) and “similar molecular pathways appear to be involved in the development of DKD and retinal microvascular injury,” they added.

To detect structural and vascular retinal changes in patients with T2D without or without DKD, the researchers used swept-source optical coherence tomography (OCT) and OCT angiography (OCTA) to assess the eyes of patients presenting to a hospital in southern Brazil.

All participants presented to the public teaching hospital between July 2018 and July 2019 and were older than 45 years. A control group was made up of healthy, age-matched volunteers with no prior or current history of diabetes or kidney disease. “Controls also could not present any ophthalmologic condition that could interfere on images evaluation as opacities and spherical equivalent outside ± 3 diopters,” the authors said.

The Chronic Kidney Disease Epidemiology Collaboration equation was used to calculate estimated glomerular filtration rate (eGFR), and all examinations were carried out in the morning. Each participant also underwent a complete ophthalmologic examination.

Of 129 patients with T2D, 258 eyes were included: 128 of 64 individuals with mild or no DKD and 130 eyes of 65 patients with DKD. Seventy-four eyes of 37 controls were also included in analyses. Sixteen eyes of patients with T2D were excluded for potentially confounding factors.

Analyses revealed:

• Patients with T2D and DKD were more likely to have mild DR (72.9%; P < .001) and higher mean (SD) urinary albumin concentration (UAC) (310.2 [878.6] mg/L; P ≤ .001)
• These patients were also more likely to present with worse mean best corrected visual acuity (43.7 [10.9] letters read; P = .022) and lower eGFR values (72.6 [27.7] mL/min per 1.73 m²; P < .001)
• Retinal layers in patients with T2D were thinner than in controls in the inner retina, central retinal thickness, and total volume; ganglion cell layer plus (GCL+) (all quadrants); GCL++ (all quadrants); and retinal nerve fiber layer (RNFL) total and temporally
• The superficial plexus of patients with T2D presented lower capillary density compared with controls (central quadrant 95% CI, −3.8 to 0.7; P = .004), except in the inferior quadrant
• OCTA showed a lower capillary density in superficial plexus, central quadrant (95% CI, − 4.0 to − 0.3; P = .016) in the DKD group compared with controls (95% CI, − 4.2 to − 0.3; P = .020)

Overall, “results showed significant thinning of the inner retina of T2D patients, especially the GCL+/++ layer and RNFL; enlargement of the foveal avascular zone (both superficial and deep plexus); and lower capillarity in the superficial retinal plexus compared with controls,” the authors wrote. They added these findings suggest “neurovascular changes are an ongoing component of DR that may precede clinically moderate to severe microvascular changes.”

Results are also in accordance with prior descriptions of microcirculatory impairment in the vasculature of diabetic eyes prior to severe indicators of DR, the researchers explained. Data also point to a possible link between signs of DKD and microvascular foveal changes that suggest a higher risk for more severe DR.

The cross-sectional design of the study and its limited sample, composed mainly of White women, mark limitations to the analysis. Future longitudinal studies are warranted to better elucidate the relationship between early retinal neurovascular changes and risk of kidney disease or if DKD can drive worse retinal prognoses.

However, data did show “DKD was associated with inner retinal and superficial plexus vascular changes in T2D patients with mild or no DR, suggesting an association of eye and early kidney changes,” the authors concluded.

Reference

da Silva MO, do Carmo Chaves AEC, Gobbato GC, et al. Early neurovascular retinal changes detected by swept-source OCT in type 2 diabetes and association with diabetic kidney disease. Int J Retina Vitreous. Published online December 5, 2021. doi:10.1186/s40942-021-00347-z