Diabetes patients may experience faster progression of retinal neurodegeneration and choroidal thinning. Photo: Jay M Haynie, OD. Click image to enlarge.

Assessing the rate of change of choroidal, retinal and ganglion cell-inner plexiform layer thickness could be of great clinical significance in predicting diabetic retinopathy (DR) onset and monitoring progression. A recent observational study in China demonstrated a temporal association between the rate of change in thickness of these layers and DR occurrence. While both those who developed DR and those who did not observed an overall reduction in choroidal and ganglion cell-inner plexiform layer thickness, rates of choroidal and retinal thickening were significantly faster in the DR group.

The researchers assessed 924 patients with type 2 diabetes but without DR. In this group, 61% were female, with an average age of 63.7 and an average diabetes duration of 8.6 years. All participants underwent annual ocular examination with swept-source OCT. The team compared the change in the three layer thicknesses between patients who developed incident DR or remained without DR during the three-year follow-up. In the cohort, 17% developed DR.

“The current study found significant rates of retinal thickness thickening and thinning of the choroidal thickness and ganglion cell-inner plexiform layer in incident DR patients after adjustment for confounding factors, which are novel findings not reciprocated by previous studies,” the researchers noted.

Reductions in average ganglion cell-inner plexiform layer thickness over the three years were -0.97μm/year in incident DR patients and -0.76μm/year in non-DR patients. After adjusting for confounding factors, average choroidal and ganglion cell-inner plexiform layer thinning was significantly faster in incident DR patients compared with those without DR by 2.09μm/year and 0.29μm/year, respectively.

The retinal thickness in the incident DR group increased, while the retinal thickness in the non-DR group decreased over time, with the adjusted difference of 2.09μm/year for central field retinal thickness.

“These results may assist to understand the pathophysiology of neurodegeneration and choroidal impairment in diabetic patients, and swept-source OCT should be re-evaluated in patients with glaucoma,” the researchers concluded in their paper. “Further studies with various ethnicities and longer duration are warranted to confirm the value of ganglion cell-inner plexiform layer and choroidal thickness monitoring in DR management.”

Huang Y, Zhang N, Bulloch G, et al. Rates of choroidal and neurodegenerative changes over time in diabetic patients without retinopathy: a three-year prospective study. Am J Ophthalmol. July 20, 2022. [Epub ahead of print].