Alterations in Retinal Layer Metrics and Their Association with Visual Acuity in Diabetic Retinopathy
thesisposted on 27.10.2017, 00:00 authored by LakshmiPriya Rangaraju
Diabetic Retinopathy (DR), which is the most serious ocular complication of diabetes, causes alterations in retinal structure, leading to visual acuity (VA) loss. Proper assessment and monitoring of the disease progression with timely therapeutic intervention can help prevent vision loss due to DR. Previous studies have reported changes in retinal layer thickness due to DR and their association with VA, as well as changes in retinal layer reflectance and organization. However, concurrent assessment of these metrics and their relationship with VA has not been reported. In the current study, our primary aim was to determine the associations of retinal layer thickness, retinal layer reflectance, and retinal layer disruption with VA. Quantitative retinal metrics were obtained from optical coherence tomography (OCT) images in 149 diabetic patients, categorized into three groups: no DR (N=50) non-proliferative DR (NPDR; N=59) proliferative DR (PDR; N=40). In a follow-up study, 23 of these patients were imaged at a second visit to evaluate changes in retinal layer metrics over time. The OCT images were analyzed using a semi-automated image segmentation software to identify 7 different retinal layers and generate en face thickness maps and reflectance images. ANOVA identified significant differences in thickness of the central subfield (CST) among three groups (P=0.01). VA and thickness of three retinal structures: CST, INL and OPL were correlated significantly (ρ>0.24; P<0.001), such that increased thickness was associated with reduced acuity. VA and NFL reflectance were correlated significantly (ρ=-0.24; P=0.003), such that subjects with higher reflectance had better VA. Lower OSL reflectance was correlated with lower VA (ρ=-0.29; P<0.001). Subjects with disruptions in the INL and ONL had lower VA compared to subjects with no disruptions in these interfaces (P<0.001). In the follow-up study, RPE and OSL thickness were significantly different between two visits. These results indicate that assessment of specific retinal structures may be helpful for monitoring visual outcome due to DR. Similarly, reflectance alterations, which are not commonly evaluated, may provide additional important information. Finally, changes in selected retinal thickness can be observed over a relatively short time in DR, with significant thickening observed in the RPE and OSL.