Study Suggests Connections Between Structure and Function in Subclinical Diabetic Retinopathy
By Liang Zhang, MD, PhD
Many studies have documented subclinical changes in the retinal microvasculature revealed by OCT angiography (OCTA) and showed reduced retinal function in eyes of diabetic patients without otherwise discernible diabetic retinopathy. Far fewer studies have explored a relationship between retinal function and OCTA-detected microvascular changes. My colleagues and I recently completed such a study.1
In 66 patients with type 2 diabetes and no DR and 62 healthy controls, we compared 16 and 32 Tds flicker electroretinography (ERG), OCT-measured macular ganglion cell complex thickness and retinal nerve fiber layer thickness, and OCTA-measured radial peripapillary capillary density and vessel density in the superficial capillary plexus and deep capillary plexus. With the exception of GCC thickness, all measured parameters were significantly reduced in the diabetic eyes (Figure 1). On ERG, implicit time was delayed, and amplitude was decreased in the diabetic group compared with the control group (Figure 2).
Our results were similar to results from previous investigations in that we observed microvascular and functional impairments in the absence of any retinal lesions. We also found ERG-measured function to be associated with decreased vessel density in the superficial capillary plexus parafoveal region and with increased HbA1c. These findings are particularly interesting because they suggest prolonged hyperglycemia and metabolic abnormalities may have direct effects on retinal neurons and capillaries.
OCTA’s advancement of our understanding of diabetic eye disease will likely lead to new treatment targets that will improve outcomes. In the meantime, the technology enables frequent, noninvasive patient monitoring, which our study suggests may be warranted to help safeguard vision for diabetic patients without diabetic retinopathy.
Figure 1. OCTA 4.5×4.5-mm scans of a control nondiabetic eye (a) and a diabetic eye without clinically detectable retinopathy (b). Reduced capillary density is seen inside the optic disc and in the peripapillary region.
Figure 2. ERG waveforms show delayed implicit time (ms) and decreased amplitude (μV) in the eye of a diabetic patient without retinopathy (right) compared with the eye of a nondiabetic patient (left).
1. Zeng Y, Cao D, Yu H, et al. Early retinal neurovascular impairment in patients with diabetes without clinically detectable retinopathy. Br J Ophthalmol. E-pub ahead of print: Jan. 23, 2019.
Dr. Zhang is chief of the Department of Ophthalmology at Guangdong General Hospital in Guangzhou, China.