Association of reduced inner retinal thicknesses with chronic kidney disease

Abstract

Background: Tissue derived biomarkers may offer utility as indicators of accumulated damage. Reduced thickness of retinal neuronal tissue and the vascular choroid have previously been associated with vascular damage and diabetes. We evaluated associations between retinal thickness, retinal microvascular and choroidal measures, and renal function in a population with a high burden of comorbidity.

Methods: Participants were recruited from nuclear cardiology or renal medicine clinics. Retinal and choroidal thickness were measured from spectral-domain optical coherence tomograms. Retinal microvascular parameters were assessed from digital fundus photographs using a semi-automated software package.

Main outcome measure: Chronic kidney disease (CKD) categorised as: CKD stages 1-2, eGFR ≥60 ml/min/1.73m²; CKD stage 3, eGFR 30-59 ml/min/1.73m², and CKD stages 4-5, eGFR ≤29 ml/min/1.73m².

Results: Participants (n = 241) had a mean age of 65 years and a mean eGFR of 66.9 ml/min/1.73m². Thirty-nine % of the cohort had diabetes and 27% were using diuretics. Thinning of the inner retina and changes to its microvascular blood supply were associated with lower eGFR and CKD stages 4 and 5, while no associations were found between the outer retinal layers or their choroidal blood supply and CKD of any stage. These associations remained following adjustment for age, mean arterial blood pressure, diabetes status, low-density lipoprotein, body mass index, and sex.

Conclusions: Inner retinal thinning and retinal microvascular variation is associated with advanced CKD (stages 4 & 5) independent of important confounding factors, but not with earlier stage CKD (stage 3) and, therefore, its utility as a biomarker for early CKD is not supported in this study.

Keywords: Choroid; Choroidal vascularity index; Choroidal volume; Chronic kidney disease; Renal function; Retina; Retinal microvasculature; Retinal thickness.

Fig. 1

Retinal images and grid positions: a shows an image of the retina en face. b shows a cross-sectional image with differentiation of the retinal layers using the HAYEX software. The cross-section of the retina represents the layers directly behind the green line bisecting the en face image in panel A. The cross hairs in the left hand panel indicate the location of the foveal dip which can be seen as a depression in the centre of the image in panel B. c indicates the approximate position and size of the ETDRS grid used for reporting retinal thickness. Segment F is centred over the fovea. The annulus proximal to the fovea (annulus 1) comprises segments; S1 = superior 1; N1 = nasal 1; I1 = inferior 1; T1 = temporal 1. The annulus distal to the fovea comprises segments; S2 = superior 2; N2 = nasal 2; I2 = inferior 2; T2 = temporal 2. d highlights the locations where the ETDRS grid segments bisect the retinal image shown in panel B