Evaluation of retinal vessel quantity within individual retinal structural layers using optical coherence tomography angiography.

PURPOSE: To evaluate retinal vessel quantity within various retinal structural layers using optical coherence tomography angiography (OCTA). METHODS: In this IRB-approved study, 22 normal eyes (from 22 subjects) were imaged using the Spectralis OCT2, with a 15 × 15 degree OCTA scan centered on fovea and two additional 15 × 5 degree OCTA scans, displaced temporally and nasally by 15 degrees along the fovea-Bruch's membrane opening (BMO) axis. Following projection artifact removal (PAR), vessel quantity (i.e., amount of flow signal) within each retinal nuclear and plexiform layer was assessed across the scan and was plotted as a vessel quantity profile over this fovea-BMO axis. Vessel quantity was correlated against the retinal layer thickness at the corresponding locations using the Spearman correlation. RESULTS: For the nerve fiber layer (NFL), the vessel quantity was highest nasally and declined towards the fovea and was near zero temporal to the fovea with or without PAR. For all other retinal layers, the retinal vessel quantities were greatest in the parafoveal retina, peaking approximately 5 degrees from the foveal center. Before PAR, the parafoveal vessel quantity was highest in the inner plexiform layer (IPL). Following PAR, the vessel quantity in the IPL decreased but was relatively unchanged in the other layers. The vessel quantity correlated moderately well with retinal layer thickness (r = 0.432 to 0.511; P < 0.05 among the various layers). CONCLUSIONS: Retinal vessel quantity varies significantly among the various structural layers, with significant regional variability. Projection artifact can significantly impact retinal vessel quantity in the deeper layers, but the effect appears to be most pronounced in the IPL.

Relationship between Retinal Thickness Profiles and Visual Outcomes in Young Adults Born Extremely Preterm: The EPICure@19 Study.

PURPOSE: To quantify inner and outer retinal layer thicknesses and understand their relevance to visual function among young adults born extremely preterm (EP). DESIGN: Prospective observational study with 19 years of follow-up. PARTICIPANTS: A total of 354 eyes (226 eyes of former EP infants and 128 age-matched full-term control eyes) from 177 young adults were evaluated. Among EP participants, 50% of eyes (112/226) were not previously diagnosed with neonatal retinopathy of prematurity (ROP), 38% of eyes (84) had ROP not deemed to require treatment in the neonatal period, and 13% of eyes (30) had neonatal cryotherapy or laser ablation for ROP. METHODS: Subjects underwent eye examinations including best-corrected visual acuity (BCVA) and Heidelberg Spectralis (Heidelberg Engineering, Heidelberg, Germany) macular spectral-domain (SD) OCT imaging. Retinal layers were auto-segmented and thickness profiles were computed at the fovea by the instrument software. MAIN OUTCOME MEASURES: Correlation between retinal sublayer thickness and BCVA. RESULTS: Compared with control eyes, the inner and outer retinal layers of EP eyes were significantly thicker and BCVA was significantly reduced. Retinal layer thicknesses and BCVA were similar for untreated EP eyes and those without neonatal ROP. In contrast, treated eyes had increased inner and outer retinal layer thickness and decreased vision. Inner retinal layer thickness was moderately correlated with worse BCVA (r = 0.30, P < 0.001), but outer retinal layer thickness was not (r = -0.01, P = 0.80). Multivariate regression indicated ganglion cell layer thickness was a significant independent predictor of BCVA. CONCLUSIONS: Extremely premature birth influences maturation of the fovea and visual outcomes into early adult life. Increased ganglion cell layer thickness was associated with worse BCVA. Eyes requiring neonatal treatment for ROP had associated worse BCVA at the age of 19 years.

Morphological characteristics of eyes with neovascular age-related macular degeneration and good long-term visual outcomes after anti-VEGF therapy.

PURPOSE: To analyse the morphological characteristics of eyes with neovascular age-related macular degeneration (AMD) with good long-term visual acuity after anti-VEGF (vascular endothelial growth factor) therapy. METHODS: Retrospective, observational study of 175 patients with neovascular AMD with >5 years of follow-up after initiating anti-VEGF therapy. Spectral-domain optical coherence tomography images were assessed for thickness of pigment epithelial detachment (PED), subretinal hyper-reflective material (SHRM), subretinal fluid and subfoveal choroidal, as well as the integrity of the outer retinal bands. RESULTS: The final analysis cohort included 203 eyes (175 patients) followed for a mean of 7.84±1.70 years (range: 5-11). The maximum PED thickness in the foveal central subfield (FCS) was significantly lower (p<0.001) in the poor vision group (13.11 µm) compared with the intermediate (86.25 µm) or good (97.92 µm) vision groups, respectively. In contrast, the maximum thickness of SHRM in the FCS was significantly thicker (p<0.001) in eyes with poor vision (149.46 µm) compared with eyes with intermediate vision (64.37 µm) which in turn were significantly thicker (p<0.001) than eyes with good vision (9.35 µm). The good vision group also had better continuity of all outer retinal bands (external limiting membrane, ellipsoid zone, and retinal pigment epithelium) compared with the other two groups (all p<0.001). CONCLUSION: A thicker PED and thinner SHRM were correlated with better vision in eyes with neovascular AMD following long-term anti-VEGF therapy. If replicated in future prospective studies, these findings may have implications for design of optimal anatomic endpoints for neovascular AMD treatment.

Retinal Vascular Changes During Pregnancy Detected With Optical Coherence Tomography Angiography.

Purpose: To evaluate retinal vascular status during pregnancy by using optical coherence tomography angiography (OCTA). Methods: Women in their third trimester of pregnancy and nonpregnant age-matched women were recruited for this prospective, case-control study. Subjects were imaged with OCTA. Main outcome measures were foveal avascular zone parameters, perfusion density (PD) percentage in the superficial retinal capillary plexus (SCP), PD percentage in the deep retinal capillary plexus (DCP), SCP vessel length density (VLD), DCP-VLD, and choriocapillaris (CC) flow voids (i.e., flow deficits in the CC). Results: Nineteen eyes of 10 pregnant subjects and 44 eyes of 27 nonpregnant control women were included. Mean ages were 36 ± 7 and 35 ± 8 years (SD), respectively (P value = 0.78). Mean gestational age of pregnant women was 33 weeks (range = 29-39, SD = 3). There was a significant reduction in the SCP-PD in the entire scan and in the nasal Early Treatment Diabetic Retinopathy Study subfield (47.9 vs. 49.7, P = 0.04 and 49.3 vs. 51.6, P = 0.03, respectively) in the pregnant cohort versus controls. There was a significant increase in the DCP-PD in the parafoveal region and in the temporal and inferior Early Treatment Diabetic Retinopathy Study subfields (58.0 vs. 55.9, P = 0.03; 57.9 vs. 55.5, P = 0.02; 58.0 vs. 55.9, P = 0.05, respectively) in the pregnant cohort. There was no significant difference in foveal avascular zone parameters, SCP-VLD, DCP-VLD, or CC flow voids between the two populations. Conclusions: This study detected retinal vasculature changes in the third trimester of pregnancy. Mean SCP-PD was significantly decreased and mean DCP-PD was significantly increased without a difference in VLD.

Distinct Retinal Capillary Plexuses in Normal Eyes as Observed in Optical Coherence Tomography Angiography Axial Profile Analysis.

Optical coherence tomography angiography (OCTA) allows the retinal microvasculature to be visualized at various retinal depths. Previous studies introduced OCTA axial profile analysis and showed regional variations in the number and location of axially distinct vascular retinal plexuses. OCTA acquisition and processing approaches, however, vary in terms of their resulting transverse and axial resolutions, and especially the latter could potentially influence the profile analysis results. Our study imaged normal eyes using the Spectralis OCT2 with a full-spectrum, probabilistic OCTA algorithm, that, in marked contrast to split-spectrum approaches, preserves the original high OCT axial resolution also within the resulting OCTA signal. En face OCTA images are generally created by averaging flow signals over a finite axial depth window. However, we assessed regional OCTA signal profiles at each depth position at full axial resolution. All regions had two sharp vessel density peaks near the inner and outer boundaries of the inner nuclear layer, indicating separate intermediate and deep capillary plexuses. The superficial vascular plexus (SVP) separated into two distinct peaks within the ganglion cell layer in the parafoveal zone. The nasal, superior, and inferior perifovea had a deeper SVP peak that was shifted anteriorly compared to the parafoveal zone. Axial vascular density analysis with high-resolution, full spectrum OCTA thus allows healthy retinal vasculature to be precisely reconstructed and may be useful for clinically assessing retinal pathology.