Abstract
Purpose:
Patients with chronic kidney disease (CKD) have a 10-30 fold increased risk of mortality due to cardiovascular disease (CVD). There is an established association between the vasculopathy affecting the kidney and the retina, suggesting common pathological mechanisms. Consequently, the examination of ocular vasculature and structure may be a valuable clinical aid in studying CVD risk and systemic microvascular damage, particularly in patients with CKD.<br /> The aim of this prospective, cross-sectional study was to examine the retina and choroid in patients with CKD, using Spectral-Domain Optical Coherence Tomography (SD-OCT), and correlate measurements with established biomarkers of CKD.
Methods:
24 patients with CKD, 24 patients with hypertension, and 25 age and sex matched healthy controls were recruited.<br /> Exclusion criteria included severe CKD requiring dialysis.<br /> All participants were imaged with SD-OCT (Heidelberg Spectralis). Measurements included retinal thickness, retinal nerve fibre layer (RNFL) thickness, macular volume and choroidal thickness. Blood and urinary measurements were also taken, including glomerular filtration rate (GFR), urinary protein and plasma Interleukin-6 (IL-6).
Results:
Retinal thickness was reduced across the macula in CKD patients compared to both those with hypertension (p<0.01), and controls (p<0.05). RNFL thickness did not differ between groups. Macular volume was lower in CKD patients compared to both patients with hypertension (p<0.0001) and controls (p<0.001). Similarly, CKD was associated with a reduced choroidal thickness (across all three separate locations measured on the macula) compared to both patients with hypertension (p<0.001) and controls (p<0.01).<br /> Interestingly, in those with CKD, a thinner choroid was associated with a lower GFR (p<0.01) and more severe proteinuria (p<0.01), both important independent CVD risk factors. A thinner choroid also correlated with higher plasma levels of IL-6 (r=-0.61, p<0.01), an inflammatory cytokine thought to be a marker of vascular inflammation.
Conclusions:
The decreases in retinal and choroidal thickness seen in CKD may represent significant systemic microvascular injury. It remains unclear how these may change with therapy. Thus, OCT may offer potential utility in assessing microvascular damage in patients at high CVD risk as well as a potential biomarker of efficacy for therapies used to reduce this risk.