Retinal vascular density evaluated by optical coherence tomography angiography in macular telangiectasia type 2

Skeleton density and ellipsoid zone loss are prognostic for progression in Macular Telangiectasia Type 2

Macular Telangiectasia Type 2 (MacTel) is a chronic, progressive disease of the central retina characterized by vascular and neurodegenerative changes. As there is currently no treatment for non-neovascular MacTel, there is a dearth for biomarkers identifying eyes with an increased risk for disease progression for patient counseling and clinical trial recruitment. Eyes were classified to be stable or progressive, defined by the fundus photography-based grading system by Gass and Blodi. First, structural differences between these two groups were assessed, employing optical coherence tomography (OCT) and OCT-angiography. Univariate regression analyses revealed evidence towards a lower superficial retinal layer (SRL) vessel density (VD), skeleton density (SD) and deep retinal layer (DRL) SD in progressing compared to stable eyes (p = 0.05, p = 0.05, p = 0.07). Second, a multivariable predictive model was employed to examine the predictive value of structural and functional parameters for disease progression. Baseline best corrected visual acuity (BCVA) and SRL SD are prognostic for disease progression (p < 0.001, p = 0.05). The presence of ellipsoid zone (EZ) loss is prognostic for future central retinal thickness (p < 0.01). We propose SRL SD, BCVA, and EZ loss as prognostic biomarkers and as possible outcome measures in future interventional studies in MacTel.

Evaluation of Optic Disc, Retinal Vascular Structures, and Acircularity Index in Patients with Idiopathic Macular Telangiectasia Type 2

BACKGROUND

We aimed to compare the retinal, optic disc vascular density (ODVD) values, and acircularity index (AI) of patients with idiopathic macular telangiectasia type 2 (IMT) and healthy individuals using the optical coherence tomography angiography (OCTA) device.

METHODS

The study included 39 patients with IMT and 37 healthy controls. The OCTA findings of the patients and controls were examined.

RESULTS

The total, parafoveal and perifoveal vascular density of the superficial capillary plexus, choriocapillaris blood flow, inside-disc ODVD, retinal nerve fiber layer (RNFL), and retinal thicknesses were found to be statistically significantly lower, and the foveal avascular zone value was statistically significantly higher in the IMT group compared to the control group (p = 0.001, p = 0.01, p = 0.02, p = 0.01, p = 0.009, p = 0.002, p = 0.02, respectively). There was a statistically significant negative correlation between best-corrected visual acuity (BCVA) and AI (p = 0.02), and a statistically significant positive correlation between peripapillary vascular density and BCVA (p = 0.04).

CONCLUSIONS

We consider that the lower retinal, choriocapillaris, ODVD values, and retinal and RNFL thicknesses in the patients with IMT compared to the controls were due to vascular damage, remodeling, fibrosis, proliferation, and Müller cell damage. Ellipsoid zone defect, AI, and peripapillary vascular density are important indicators in the evaluation of visual acuity in these patients.

Optical coherence tomography angiography findings in transfusion-dependent beta-thalassemia patients with and without splenectomy

BACKGROUND

Ocular involvement is common in transfusion-dependent beta-thalassemia (TDβ-T) patients. We aimed to investigate the effect of splenectomy on optical coherence tomography angiography (OCTA) findings in TDβ-T patients.

METHODS

The study is a prospective cross-sectional study. A total of 45 eyes of 23 patients with splenectomy (34.04±8.83 years), 18 eyes of 9 patients without splenectomy (27.44±5.43 years), and 54 eyes of 27 controls (33.22±6.44 years) were included. Vessel density in superficial capillary plexus, deep capillary plexus and radial peripapillary capillary, foveal avascular zone, choriocapillaris flow area, choroidal and retinal thickness detected by OCTA were evaluated. p < 0.05 was considered significant.

RESULTS

Vessel density of superficial capillary plexus and deep capillary plexus were similar in patients with and without splenectomy, and controls. Choriocapillaris flow area was significantly decreased in patients with splenectomy than that in those without splenectomy and controls (2.02±0.12 vs. 2.17±0.1 and 2.14±0.12; p < 0.001). Choroidal thickness was significantly lower in patients without splenectomy than in patients with splenectomy and controls (260.05±61.02 vs. 305.11±42.13 and 298.89±29.14, p = 0.008). Parafoveal and perifoveal thickness of the full retina and outer retina were significantly lower in patients without splenectomy than in patients with splenectomy and controls (301.06±10.0, 279.78±10.28 vs. 311.04±14.89, 290.87±13.67 and 316.63±13.57, 289.56±9.31, p < 0.001 and p = 0.002; 174.72±7.81, 167.17±6.21 vs. 182.87±8.81, 173.60±7.09 and 185.11±9.26, 173.96±6.79, p = 0.001 and p < 0.001, respectively).

CONCLUSIONS

OCTA findings can provide information about the microvascular effects of splenectomy on the retina of patients with TDβ-T.

Use of OCT Angiography to Diagnose and Manage Atypical Presentations of Macular Telangiectasia Type 2

Macular telangiectasia Type 2 (MacTel) is a bilateral acquired retinal disease characterized by both vascular changes and atrophy of the retina. The purpose of this case series is to highlight the use of optical coherence tomography angiography (OCTA) as a non-invasive imaging modality to distinguish atypical MacTel from other macular conditions with similar presentations. We performed a retrospective review of patients referred to our academic retinal practice with unconfirmed or misdiagnosed MacTel between July 2017 and July 2021. Patients' OCTA imaging findings were reviewed to guide the appropriate diagnosis and management of atypical MacTel. Fifteen eyes from eight patients were included in this study. Six patients were referred with previous diagnoses of either full-thickness macular hole, lamellar hole, vitreomacular traction (VMT), postoperative cystoid macular edema (CME), or diabetic macular edema (DME). Two patients were referred to us to confirm the diagnosis of MacTel. OCTA revealed telangiectatic vessels in the temporal parafovea of all 15 eyes. OCTA also highlighted previously undiagnosed subretinal neovascularization (SRNV) in seven eyes. OCTA imaging is a valuable imaging modality to distinguish MacTel from other macular conditions, whose treatment courses vary substantially. Due to its ease of use, it holds immense potential in the future as treatments for non-proliferative MacTel emerge.

Optical Coherence Tomography Angiography in Healthy Adult Subjects: Normative Values, Frequency, and Impact of Artifacts

Aim

This cross-sectional study is aimed at identifying normative ocular coherence tomography angiography (OCTA) values in a cohort of healthy adult Jordanian individuals and assessing the prevalence of different image artifacts and their impact on quantitative OCTA measurements.

Materials and Methods

One hundred and eighty-one eyes from 100 healthy participants were included in this study. All participants underwent a comprehensive ophthalmological examination including best corrected visual acuity, slit lamp examination, and dilated fundoscopy. Swept-source OCTA images were obtained and analyzed for all 181 eyes. We recorded vascularity measurements and analyzed the prevalence and effect of ten different artifacts on superficial and deep retinal and choriocapillaris layer images.

Results

Sixty-two percent of the participants were men (n = 62), and 38% (n = 38) were women. The age of participants ranged between 24 and 75 years (mean 50.5 ± 10.92). The mean central macular thickness was 237.71 (±22.905) μm, and the mean choroidal thickness was 257.73 (±77.027) μm. Artifacts were present in 46.4% of the acquired scans. Images with artifacts had higher mean age (p = 0.03), lower image quality (p < 0.001), higher central vascular density (p < 0.001), and lower inferior vascular density (p < 0.001) compared to artifact-free tomographs. Motion artifact was the most common type, which was present in 29 (16%) of images, followed by blink artifact 18 (9.9%), and Z offset 8 (4.4%).

Conclusion

OCTA artifact detection and correction remains a challenging aspect of the diagnostic and follow-up process of patients with retinal pathologies. To our knowledge, this is the first study to examine the association between OCTA outputs and artifacts in healthy eyes. We report that in this cohort of normal individuals, images with artifacts had a significantly higher central vascular density (22.62 vs. 16.60) and a lower inferior vascular density (46.09 vs. 48.81). We also found that a significant increase in central vascular density is only present in images with Z offset artifact type (49.03). Motion artifact was the most common artifact seen in our series. However, we observed no alteration in quantitative parameters in images with motion artifacts.

Optical coherence tomography angiography in primary eye care

Optical coherence tomography angiography (OCT-A) is a non-invasive imaging modality for assessing the vasculature within ocular structures including the retina, macula, choroid and optic nerve. OCT-A has a wide range of clinical applications in various optometric conditions which have been independently reported in the literature. This paper aims to present a review of the current literature on the clinical application of OCT-A in optometric practice as well as to analyse and evaluate the quality of the available evidence. This review included 78 articles from a literature search conducted on 26 May 2019 across the following databases: Cochrane Library of Systematic Reviews, Medline, Scopus and Web of Science. Primary ocular pathologies discussed in this review include glaucoma, diabetic retinopathy, age-related macular degeneration, myopia, acquired and congenital macular dystrophies, epiretinal membrane, retinal vein occlusion, retinitis pigmentosa, choroidal melanoma, uveitis, central serous chorioretinopathy, amblyopia and optic neuropathies. Primary outcome variables included vessel density, foveal avascular zone area and diameter, flow velocity and flow index. This review aims to evaluate the evidence available for OCT-A applications in diagnosis and prognosis of ocular conditions in an optometric setting.

Assessing the Influence of OCT-A Device and Scan Size on Retinal Vascular Metrics

Purpose

The purpose of this study was to investigate the effect of device and scan size on quantitative optical coherence tomography angiography (OCT-A) metrics.

Methods

The 3 × 3 mm scans from Optovue AngioVue and Zeiss AngioPlex systems were included for 18 eyes of 18 subjects without ocular pathology. The foveal avascular zone (FAZ) was segmented manually by two observers, from which estimates of FAZ area (using both the nominal image scale and the axial length corrected image scale) and acircularity were derived. Three scan sizes (3 mm, 6 mm HD, and 8 mm) from the AngioVue system were included for 15 eyes of 15 subjects without ocular pathology. For each subject, larger image sizes were resized to the same resolution as 3 × 3 mm scans, aligned, then cropped to a common area. FAZ area, FAZ acircularity, average and total parafoveal intercapillary area, vessel density, and vessel end points were computed.

Results

Between the devices used here, there were no significant differences in FAZ acircularity (P = 0.88) or FAZ area using scaled (P = 0.11) or unscaled images (P = 0.069). Although there was no significant difference in FAZ area across scan sizes (P = 0.30), vessel morphometry metrics were all significantly influenced by scan size.

Conclusions

The scan devices and sizes used here do not affect FAZ area measures derived from manual segmentations. In contrast, vessel morphometry metrics are affected by scan size. As individual differences in axial length induce differences in absolute scan size, extreme care should be taken when interpreting metrics of vessel morphometry, both between and within OCT-A devices.

Translational Relevance

A better characterization of the confounds surrounding OCT-A retinal vasculature metrics can lead to improved application of these metrics as biomarkers for retinal and systemic diseases.

Perivenular Capillary Loss: An Early, Quantifiable Change in Macular Telangiectasia Type 2

Purpose

To evaluate differences in parafoveal vascular density surrounding arterioles and venules in type 2 macular telangiectasia (MacTel).

Methods

Thirty-seven eyes (20 subjects) diagnosed with MacTel and 16 healthy eyes (10 subjects) were imaged with optical coherence tomography angiography between March 2016 and June 2019 in this single-center, observational, cross-sectional study. Arterioles and venules were manually identified, and perivascular density was generated using a custom MATLAB code. The primary outcome measure was the ratio of periarteriolar to perivenular vascular density (arteriovenous [A/V] capillary ratio) in the superficial and deep capillary plexuses across MacTel stages. The main secondary outcome measures were overall parafoveal vascular density (VD), periarteriolar VD, and perivenular VD.

Results

In the superficial capillary plexus (SCP), the A/V capillary ratio was significantly higher in MacTel subjects than controls (0.914 vs. 0.892; P = 0.0044). The greatest differences occurred between controls and nonproliferative MacTel subjects without optical coherence tomography evidence of disease (P = 0.0055). A/V capillary ratios progressed in a nonlinear fashion with MacTel severity, increasing from nonproliferative disease (0.912) to intraretinal proliferative disease (0.931), then decreasing in subretinal proliferative disease (0.905). Parafoveal VD in the SCP was lower in MacTel subjects than controls only in subretinal proliferative disease (P = 0.0130).

Conclusions

The A/V capillary ratio of the SCP is a quantifiable metric of vascular pathology in MacTel that occurs earlier than decline in parafoveal VD. Elevated A/V capillary ratios in MacTel are consistent with an early, disproportionately perivenular disruption in the SCP.

Translational Relevance

Findings inform MacTel pathogenesis through revealing early perivenular capillary loss and offer a new quantitative metric for earliest stage MacTel.

Overlap between telangiectasia and photoreceptor loss increases with progression of macular telangiectasia type 2

OBJECTIVES

To examine the topographical correlation between ellipsoid zone loss and telangiectasia in the deep capillary plexus in patients with macular telangiectasia type 2 (MacTel).

METHODS

38 eyes (20 subjects) diagnosed with MacTel were imaged with OCTA between March 2016 and June 2019 in this single center, cross-sectional observational study. The en face OCTA and OCT were evaluated for areas of deep capillary plexus telangiectasia and ellipsoid zone loss, respectively, and their outlines were superimposed to study their overlap (mm2). The primary outcome was percentage of overlap and its relationship to MacTel stage. Secondary outcomes included the relationship between neovascularization and hyperreflective foci as well as correlations between ellipsoid zone loss, deep capillary plexus telangiectasia and visual acuity.

RESULTS

In nonproliferative MacTel stage, ellipsoid zone loss was localized to margins of telangiectatic areas (mean overlap = 15.2%). In proliferative stages, ellipsoid zone loss showed a higher degree of overlap with telangiectatic areas (mean overlap = 62.8%). Overlap increased with advancing MacTel stages, with an overall average of 45.3%. Overlap correlated highly with ellipsoid zone loss (r = 0.831; p<0.0001). Telangiectasia was present in all 38 eyes (range: 0.08mm2-0.99mm2), while ellipsoid zone loss was absent in 6 (range: 0.00-3.32mm2). Visual acuity correlated most strongly with ellipsoid zone loss (r = 0.569; p = 0.0002), followed by overlap (r = 0.544; p = 0.0004), and finally, telangiectasia (r = 0.404; p<0.0118). Presence of hyperreflective foci on OCT correlated with the presence and intraretinal location of neovascularization.

CONCLUSIONS

Ellipsoid zone loss occurs at the margins of deep capillary plexus telangiectasia in nonproliferative MacTel, with progressively increasing overlap as MacTel advances, peaking in proliferative disease. Deep capillary plexus telangiectasia and its overlap with ellipsoid zone loss are two promising markers of nonproliferative MacTel, while hyper-reflective foci are markers for proliferative MacTel.

Evaluation of 1-year follow-up results of macular telangiectasia type 2 cases by optical coherence tomography angiography

The results of 1-year follow-up with optical coherence tomography angiography (OCTA) of 3 patients with macular telangiectasia type 2 (MacTel 2) were evaluated. The 3X3 mm OCTA imaging was performed in January 2017 and February 2018. The superficial and deep capillary plexus vascular density changes of the whole area, the parafoveal temporal and parafoveal nasal areas were examined. The mean whole, parafoveal temporal, and parafoveal nasal vessel densities at superficial capillary plexus were 51.31, 50.39, 54.57 at baseline and 49.93, 46.79, 51.83 at 1-year follow-up, respectively. The mean whole, parafoveal temporal and parafoveal nasal vessel densities at deep capillary plexus were 59.06, 59.05, 63.39 at baseline and 52.18, 54.68, 57.9 at 1-year follow-up, respectively. In this case series, it was shown quantitatively that vessel densities of MacTel2 patients markedly decreased over time, more pronounced in the deep capillary plexus.