Abstract
Purpose :
Macular retinal nerve fiber layer (mRNFL) and ganglion cell-inner plexiform layer thickness (GC-IPL) measurements are important markers of diabetic retinal neurodegeneration (DRN). However, we do not fully understand the factors that contribute to the variation in mRNFL and GC-IPL thickness among patients with diabetes. Based on our prior work in normal eyes, we hypothesized that total retinal thickness (TRT) is an important factor accounting for variation in mRNFL and GC-IPL thickness among patients with diabetes.
Methods :
We used macular-centered spectral domain-optical coherence tomography (SD-OCT) scans of patients with diabetes from the UK Biobank dataset. We excluded participants with poor quality scans, retinal or optic nerve disease, or retinal disease visible on scans. Independent linear regression was used to determine factors associated with mRNFL and GC-IPL thicknesses. Statistically and clinically significant factors were included in three multiple linear regression models for each layer: model 1: not accounting for TRT; and model 2: accounting for TRT. Model 3 included mRNFL and GC-IPL as a percentage of TRT as the outcome. A p-value of less than 0.05 was considered statistically significant.
Results :
A total of 3,954 eyes of participants with diabetes were analyzed. Most factors including age, glaucoma, history of cataract surgery, severity of diabetic retinopathy, hemoglobin A1c, hypertension, diabetic neuropathy, visual acuity, and intraocular pressure were statistically significantly associated with mRNFL and/or GC-IPL thickness on multivariable regression (model 1) but explained less than 1% of the variation in their thicknesses. In model 2, most of the variation was accounted for by TRT (20% for mRNFL and 50% for GC-IPL) followed by spherical equivalent and gender (mRNFL only). Race accounted for 0.2% of the variation in mRNFL thickness in model 2 and was not significantly associated with it once TRT was accounted for. Model 3 showed results similar to model 2.
Conclusions :
Although many factors were significantly associated with mRNFL and GC-IPL thickness in patients with diabetes, they accounted for a fraction of the variation in the thickness of both layers. TRT explained a fifth of the variation in mRNFL and half of the variation in GC-IPL, hence using mRNFL and GC-IPL as a percentage of TRT may be a clinically useful metric to evaluate DRN while accounting for TRT.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.