Diabetes

Type 2 diabetes is expected to accelerate age-related peripapillary retinal nerve fiber layer (pRNFL) loss; but limited information on the rate of reduction; in pRNFL thicknesses in patients with type 2 diabetes is available. People with type 2 diabetes show accelerated thinning of the peripapillary retinal nerve fiber layer (pRNFL); even in the absence of diabetic retinopathy (DR), according to South Korean researchers.

“However, they results suggest that the pRNFL status as well as DR status should be checked periodically,” Dr. Jung Yeul Kim of Chungnam National University Hospital, in Daejeon, and colleagues write in JAMA Ophthalmology. However, the team notes that pRNFL is a reliable and important variable in various ophthalmic conditions that “can be measured easily by spectral-domain optical coherence tomography.”

Patients with type 2 diabetes

A total of 164 eyes of 63 healthy individuals; and 101 patients with type 2 diabetes (49 patients without DR [non-DR group] and 52 patients with mild to moderate nonproliferative DR [NPDR group]); enrolled in this prospective, longitudinal, observational study from January 2, 2013, through February 27, 2015.

However, participants followed up for 3 years, and the peripapillary mean; and sector RNFL thicknesses measured at 1-year intervals. The mean rate of pRNFL loss estimated using a linear mixed model; and compared among the 3 groups. Follow-up was completed on March 16, 2018, and data analyzed from April 2 through July 27, 2018.

However, at baseline the mean pRNFL thickness was 96.2 um in the control group; 93.5 um in the non-DR group and 90.4 um in the DR group. Over the course of three years of follow-up; these numbers fell to 95.0, 90.3 and 86.6, respectively. But in a linear mixed model, the estimated mean pRNFL loss annually was significantly greater in the diabetic groups; compared with controls. In particular, it was 2.9 times greater in the non-DR group and 3.3 times greater in the DR group.

Glaucoma or optic neuropathy

However, the difference between the diabetic groups was not significant. The rate of pRNFL loss in the control group, the researchers note, was consistent with those of previous studies; and the reduction rates in the diabetic groups ” similar to those of patients with glaucoma.” “However, if patients with diabetes have a disease causing pRNFL reduction; including glaucoma or optic neuropathy,” the team adds, “the reduction rate may be accelerated.

“Dr. Elliott H. Sohn of the University of Iowa, in Iowa City, who co-wrote an accompanying editorial; told Reuters Health by email, “But this study builds on the paradigm-shifting concept; they purported in 2016 that diabetic retinal neurodegeneration (DRN) may manifest before clinically apparent diabetic retinopathy.” “However, the lingering questions,” he added, “are how frequently DRN is found before clinical apparent diabetic retinopathy in humans, what is the mechanism for how this occurs, and what is the impact DRN has on visual function?”