Abstract
Recent studies have shown that retinal neurodegeneration may precede visible vascular changes in diabetic retinopathy (DR). In addition, the relationship of choroidal thickness (CT) with DR stage is not well defined. To assess the inner retinal and choroidal structural changes in type 1 diabetic subjects (T1D), a cross-sectional study was conducted in 242 T1D patients and in 69 age-matched, non-diabetic individuals. The nasal retinal nerve fibre layer (RNFL) thickness was lower in T1D patients without DR (p < 0.001), with mild DR (p < 0.001), and with advanced DR (p < 0.001) compared to control subjects. The ganglion cell layer (GCL) thickness was lower in T1D patients with advanced DR compared to those with mild DR (p = 0.003) and without DR (p < 0.001) and compared to the control subjects (p < 0.001). T1D subjects with no DR and mild DR had higher CT than the control subjects, but the CT in T1D patients with advanced DR was lower (p = 0.038) than that in T1D subjects with mild DR and was not significantly different from that of the control subjects. In conclusion, T1D subjects showed a significant thinning of the nasal RNFL in the early stages of the disease, even before any vascular changes in the retina. A decrease in the GCL thickness during advanced DR stages was observed. Choroidal thickness was higher in T1D subjects without DR and in early DR stages but decreased in advanced stages.
Highlights
Diabetic retinopathy (DR) is one of the leading causes of visual impairment and preventable blindness among the adult working-age population in developed countries
We found that, compared to control subjects, nasal retinal nerve fibre layer (RNFL) thickness was lower in type 1 diabetic subjects (T1D) subjects, regardless of the DR grade
Choroidal thickness was higher in patients with no DR and mild DR compared to the control subjects
Summary
Diabetic retinopathy (DR) is one of the leading causes of visual impairment and preventable blindness among the adult working-age population in developed countries. DR has primarily been considered a microvascular disorder in which the initial manifestations include retinal microaneurysms, capillary alterations, and haemorrhaging These vascular alterations may lead to degeneration of the neuronal and glial structures of the inner retina as the disease progresses. Data from recent studies using spectral-domain optical coherence tomography (SD-OCT) imaging suggest that morphological changes in retinal neurodegeneration may precede any visible vascular changes [3,4,5,6,7] In this regard, the earliest neurodegenerative alterations occur in the main layers of the inner retina, as evidenced by the thinning of the retinal nerve fibre layer (RNFL) and the ganglion cell complex (GCC) [4,6,7,8]
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