Changes in tissue thickness in the back of the eye can correlate with worsening or improvement of renal problems and could help predict who will have worsening of kidney function, a new analysis report finds.
The research, published in the journal Nature Communications, is the first to show an association between chronic kidney disease (CKD) and the thickness of the retinal and choroidal layers in the back of the eye as measured by optical coherence tomography (OCT), a noninvasive imaging technology commonly used to evaluate eye diseases such as age-related macular degeneration (AMD), diabetic eye disease, and retinal detachments.
“These are common scans that people get at the opticians and now in many hospitals,” said Neeraj Dhaun, MD, PhD, a professor of nephrology at the University of Edinburgh, Scotland. (Opticians in the United Kingdom are the equivalent of optometrists in North America.)
CKD Severity Equals Thinner Retinas
“We scanned the back of eye of healthy people as well as patients with various types and degrees of kidney disease, and we found that two layers in the back of eye, the retina and the choroid, were thinner in patients with kidney disease compared to people who are healthy, and that the extent of this thinning predicts whether kidney function would decline going forward over a period of 2 or 3 years,” Dr. Dhaun, the corresponding author of the new paper, said.
The publication is a report of four different studies. The first study measured OCT metrics in 112 patients with CKD, 92 patients with a functional kidney transplant, and 86 control volunteers. The researchers found the retina was 5% thinner in patients with CKD than in healthy controls. They also found that patients with CKD had reduced macular volume: 8.44 ± .44 mm3 vs 8.73 ± .36 mm3 (P < .001). The choroid was also found to be thinner at each of three macular locations measured in patients with CKD vs control volunteers. At baseline, CKD and transplant patients had significantly lower estimated glomerular filtration rate (eGFR) at 55 ± 27 and 55 ± 24 mL/min/1.73 m2 compared with control volunteers at 97 ± 14 mL/min/1.73 m2.
The second study reported on OCT measurements and kidney histologic injury in 50 patients who had a kidney biopsy within 30 days of their OCT. It found that choroidal thinning at all three macular locations was independently associated with more extensive kidney scarring.
The third study focused on 25 patients with kidney failure who had a kidney transplant. Their eGFR improved from 8 ± 3 to 58 ± 21 mL/min/1.73 m2 in the first week after the transplant. The choroid in these patients thickened about 5% at 1 week and by about 10% at 1 month posttransplant. OCT of 22 kidney donors showed thickening of the choroid a week after nephrectomy before a tendency to thinning over the next year.
The fourth study found that for patients with stable CKD, every 1 mm3 decrease in macular volume correlated to an increased odds of a decline in eGFR by more than 10% at 1 year (2.48; 95% CI, 1.26-5.08; P = .01) and by more than 20% at 2 years (3.75; 95% CI, 1.26-5.08; P = .004).