En-face Images Research Articles

En Face OCT in Acute Zonal Occult Outer Retinopathy

A 32-year-old man presented with scotoma and photopsias in his left eye. Visual field testing revealed a paracentral scotoma and an enlarged blind spot. OCT B-scan showing the absence of the ellipsoid zone (EZ) and interdigitation zone (IZ) in the peripapillary and parafoveal areas (Fig A). En face image with segmentation from EZ to IZ showing hyporeflective areas surrounded by hyperreflective rings corresponding to the photoreceptor defects observed on B-scan (Fig B). B-scan obtained 1 week later showing subtle enlargement of the parafoveal photoreceptor defects (Fig C).

Analysis of microstructural changes in an X-linked juvenile retinoschisis patient harboring RS1 G668A mutation by en-face optical coherence tomography imaging

Juvenile X-linked retinoschisis (JXLR) is an X-linked recessive retinal dystrophy caused by retinoschisin (RS1) gene mutations. The current study reports and describes the cumulative findings of en-face OCT for a 7-year-old JXLR patient harboring a hemizygous pathogenic RS1 mutation (c.G668A; p.Cys223Tyr), where residue 223 is vital for cellular adhesion. Fundoscopy showed cart-wheel appearance at macula. Further, en-face OCT revealed characteristic schitic lesions in the ganglion cell layer, inner plexiform layer, inner nuclear layer, and outer plexiform layer. Our report adds to the Indian RS1 mutation spectrum and casts insights into the schisis microstructure using en-face imaging.

Analysis of Microvasculature in Nonhuman Primate Macula With Acute Elevated Intraocular Pressure Using Optical Coherence Tomography Angiography.

PurposeTo investigate responses of macular capillary vessel area density (VAD) of superficial and deep retinal vascular plexuses to elevations in intraocular pressure (IOP) in cynomolgus macaque monkeys using optical coherence tomography angiography (OCTA).MethodsIn five general anesthetized male cynomolgus monkeys, the IOP was increased incrementally by 10 mmHg from baseline (10 mmHg) to 70 mmHg and then decreased back to 10 mmHg (recovery state). Structural OCT (30° × 30°) and OCTA (20° × 15°) centered on the macula were obtained at each IOP and 3, 15, and 30 minutes after recovery. En face images of the superficial vascular complex (SVC) and deep vascular complex (DVC) were extracted, and VAD (%) compared with that at baseline was calculated.ResultsThe VADs in the SVC and DVC at baseline and at 30 mmHg IOP were 34.96%, 34.15%, 35.38%, and 30.12%, respectively. The VAD plateaued until 30 mmHg; however, the VAD was affected more in the DVC than in the SVC (P = 0.008) at 30 mmHg. It showed a significant reduction at 40 mmHg (16.52% SVC, P = 0.006; 18.59% DVC, P = 0.012). In the recovery state, the SVC showed full retention of baseline VAD, but the DVC maintained VAD approximately 70% of that at baseline. Structural OCT showed hyperreflectivity in the nuclear layer, retinal swelling, and an undifferentiated ellipsoid zone from 50 mmHg.ConclusionsDespite physiological autoregulation, perifoveal microcirculation was affected at high IOP ≥ 40 mmHg, especially in the DVC, which explains the pathological mechanism of macular vulnerability in ischemic diseases.

Evaluation of En-Face OCT Imaging in the diagnosis of macular diseases

Evaluation of En-Face OCT Imaging in the diagnosis of macular diseases

Imbalanced choroidal circulation in eyes with asymmetric dilated vortex vein.

Asymmetric dilated vortex vein (ADVV) observed in eyes with pachychoroid spectrum diseases is thought to be due to congestion of choroidal blood flow. The purpose of this study was to quantitatively investigate the blood flow velocity of ADVV using laser speckle flowgraphy (LSFG). Retrospective case series. This was a retrospective case series with 23 eyes of 18 patients with ADVV on en-face OCT. A pair of choroidal veins from ADVV side (defined as ADVV vein) and non-ADVV side (defined as non-ADVV vein) was selected in each eye under the following criteria: (i) equivalent proximity to the deviated watershed, (ii) does not overlap with retinal blood vessels in the en-face OCT image, (iii) has approximately the same blood vessel diameter. Rubber bands were placed on the selected choroidal veins on the LSFG color map. Mean blur rate (MBR) values of ADVV and non-ADVV veins were statistically compared. The average MBR was 10.11 ± 1.9 in the ADVV veins and 13.49 ± 6.2 in the non-ADVV veins, showing significantly lower values in the ADVV veins (P = 0.03). The blood vessel diameter of the ADVV was 10.26 ± 3.0 and in the non-ADVV veins, 10.63 ± 2.9 pixels; not significantly different (P = 0.66). The distance from the deviated watershed to the ADVV was 53.3 ± 24.8 and to the non-ADVV veins, 46.80 ± 20.3 pixels; not significantly different (P = 0.41). In eyes with ADVV, the blood flow velocity in the ADVV veins was lower than in the non-ADVV veins, suggesting anatomical congestion of ADVV.

Dual-Wavelength Fluorescence Monitoring of Photodynamic Therapy: From Analytical Models to Clinical Studies.

Simple SummaryFluorescence imaging is an efficient tool in monitoring photodynamic therapy procedures allowing us to track accumulation and photobleaching of a photosensitizer (PS). Chlorin-based PSs feature high absorption in the red and blue bands of visible spectrum. Due to spectral dispersion of light penetration depth in biotissues, fluorescence signals registered upon excitation by red or blue light are formed in different measurement volumes. We present analytical and numerical models of dual-wavelength fluorescence imaging for evaluation of PS localization depth in the cases of topical administration and intravenous injection. The results of analytical and numerical simulations are in good agreement with the phantom experiments, and are translated to the in vivo imaging, which allows to interpret experimental observations in animal trials, human volunteers, and clinical studies. The proposed approach allows us to noninvasively estimate typical accumulation depths of PS localization which are consistent with the morphologically expected values.Fluorescence imaging modalities are currently a routine tool for the assessment of marker distribution within biological tissues, including monitoring of fluorescent photosensitizers (PSs) in photodynamic therapy (PDT). Conventional fluorescence imaging techniques provide en-face two-dimensional images, while depth-resolved techniques require complicated tomographic modalities. In this paper, we report on a cost-effective approach for the estimation of fluorophore localization depth based on dual-wavelength probing. Owing to significant difference in optical properties of superficial biotissues for red and blue ranges of optical spectra, simultaneous detection of fluorescence excited at different wavelengths provides complementary information from different measurement volumes. Here, we report analytical and numerical models of the dual-wavelength fluorescence imaging of PS-containing biotissues considering topical and intravenous PS administration, and demonstrate the feasibility of this approach for evaluation of the PS localization depth based on the fluorescence signal ratio. The results of analytical and numerical simulations, as well as phantom experiments, were translated to the in vivo imaging to interpret experimental observations in animal experiments, human volunteers, and clinical studies. The proposed approach allowed us to estimate typical accumulation depths of PS localization which are consistent with the morphologically expected values for both topical PS administration and intravenous injection.

Persistent Hypertransmission Defects Detected on En Face Swept Source Optical Computed Tomography Images Predict the Formation of Geographic Atrophy in Age-Related Macular Degeneration

To determine whether persistent hypertransmission defects (hyperTDs), previously shown to have a greatest linear dimension (GLD) ≥250 µm on en face swept source OCT (SS-OCT) images, serve as a stand-alone early biomarker for the future formation geographic atrophy (GA). Post hoc cohort study using a subgroup of a prospective study. Patients with intermediate age-related macular degeneration (iAMD) underwent 6-×6-mm SS-OCT raster scans at baseline and during their follow-up period. En face images were generated using a slab with segmentation boundaries positioned 64 µm to 400 µm beneath the Bruch's membrane. Two graders independently evaluated all en face structural images for the presence of hyperTDs with a GLD ≥250 µm and GA. A total of 190 eyes were included with a mean ± SD follow-up of 31 ± 13.2 months. At baseline, 31 eyes (16%) had at least 1 hyperTD ≥250 µm, and 13 eyes (42%) progressed to GA. In those eyes without a hyperTD ≥250 µm at baseline, 42 (26%) developed hyperTDs ≥250 µm during their follow-up, and 11 eyes (7%) progressed to GA. At the last available follow-up visit, 25 eyes (13%) progressed to GA and of these 25 eyes, a prior hyperTD ≥250 µm was detected in 24 eyes before GA formed. A time-dependent Cox-survival regression analysis estimated an 80-fold (95% CI, 10.7-614, P < .001) increased risk of developing GA once a hyperTD ≥250 µm appeared. Persistent hyperTDs detected on en face OCT images were shown to serve as an early stand-alone OCT biomarker for the future formation of GA.

An unusual association of macular retinoschisis with progressive familiar intrahepatic cholestasis: A multimodal imaging study.

To evaluate a case of macular retinoschisis associated with a TJP2 mutation in a young woman affected by a Progressive Familiar Intrahepatic Cholestasis (PFIC) using multimodal imaging. Observational case report. A 35-year-old woman, undergone a liver transplant for PFIC, was referred to Eye Clinic for complete ophthalmological examination and multimodal imaging. Fundus examination showed no significant alterations in both eyes while multicolor image revealed the presence of several cystes in macular region. The autofluorescence image highlighted small areas of iperautofluorescence in macular region. En-face image showed a "coral shape pattern" and structural optical coherence tomography (OCT) revealed foveal hyporeflective cystic spaces in outer and inner nuclear layers, areas of splitting within the nerve fiber layer (schisis areas) and an initial preretinal fibrosis. Lastly, OCT-angiography (OCT-A) demonstrated small perifoveal teleangectasias and slight reduction of the foveal avascular zone area. Multimodal imaging could help to highlight the presence of a rare retinal disorder associated with a gene related systemic disease.

Tomographic refractive index profiling of direct laser written waveguides.

The fabrication of complex integrated photonic devices via direct laser writing is a powerful and rapidly developing technology. However, the approach is still facing several challenges. One of them is the reliable quantitative characterization of refractive index (RI) changes induced upon laser exposure. To this end, we develop a tomographic reconstruction algorithm following a modern optimization approach, relying on accelerated proximal gradient descent, based on intensity images only. Very recently, such algorithms have become the state of the art in the community of bioimaging, but have never been applied to direct laser written structures such as waveguides. We adapt the algorithm to our concern of characterizing these translation-invariant structures and extend it in order to jointly estimate the aberrations introduced by the imaging system. We show that a correct estimation of these aberrations is necessary to make use of data recorded at larger angles and that it can increase the fidelity of the reconstructed RI profiles. Moreover, we present a method allowing to cross-validate the RI reconstructions by comparing en-face widefield images of thin waveguide sections with matching simulations based on the retrieved RI profile.

MISALIGNMENT BETWEEN CENTER OF FOVEAL AVASCULAR ZONE AND CENTER OF FOVEAL PHOTORECEPTORS IN EYES WITH IDIOPATHIC EPIRETINAL MEMBRANE.

To determine the degree of misalignment between the center of foveal avascular zone and the center of foveal photoreceptors in eyes with an idiopathic epiretinal membrane (ERM). We reviewed the medical records of 61 eyes with an idiopathic ERM. A 3 × 3 mm area centered on the fovea was scanned with optical coherence tomography angiography before and at 6 months after surgery. The center of foveal avascular zone and the center of foveal photoreceptors were detected by en-face optical coherence tomography angiography images and sequential optical coherence tomography B-sections in the macular region. The presence or absence of ectopic inner foveal layers was also evaluated. The mean distance from the center of foveal photoreceptors to the center of foveal avascular zone was 111.7 ± 106.8 µm in eyes with preoperative ERM. This distance was significantly correlated with the preoperative central foveal thickness (r = 0.33, P = 0.0104). Preoperatively, the ectopic inner foveal layers were present in 27 (44.3%) of 61 eyes. The foveal misalignment was greater in eyes with ectopic inner foveal layers than in those without ectopic inner foveal layers (158.6 ± 140.0 vs. 74.4 ± 45.4 µm, P < 0.0003). At 6 months after ERM surgery, the foveal misalignment was significantly reduced to 73.7 ± 48.0 µm (P = 0.0018). Determining the degree of misalignment between the center of foveal avascular zone and the center of foveal photoreceptors might be a useful way to evaluate the degree of ERM traction.

Mean macular intercapillary area in eyes with diabetic macular oedema after anti-vascular endothelial growth factor therapy and its association with treatment response.

To evaluate the changes in the mean macular intercapillary area (ICA) from sequential enface optical coherence tomography angiography (OCTA) images following intravitreal anti-vascular endothelial growth factor (VEGF) therapy in initially treatment-naïve eyes with diabetic macular oedema (DME). In this multicentre retrospective study, 6 × 6 and 3 × 3 mm customised, total retinal projection enface OCTA images were collected and processed for quantitative assessment of ICA by a customised MATLAB software. Measurements were done in concentric regions centred on the fovea-with the exclusion of foveal avascular zone (FAZ)-in 0.5 mm diameter increments as well as within the intervening rings. In this study, 6 × 6 mm OCTA images from 46 eyes of 29 patients, and 3 × 3 mm OCTA images from 23 eyes of 15 patients were included. There was no significant change in mean ICA after treatment in either scan size or in any measurement regions (all p > 0.05). Multivariate analysis revealed that baseline BCVA was significantly correlated with the visual outcome (p=0.039). Additionally, after correction for age, baseline central retinal thickness (CRT), baseline BCVA, and retinopathy severity, mean ICA in the 1.5 mm circle was found to be a significant predictor of post treatment CRT, (p=0.006). Absence of significant change in mean ICA after a minimum of three intravitreal anti-VEGF injections, may indicate that, in the short term, anti-VEGF injections neither impair nor improve macular perfusion in DME. Baseline BCVA was found to be a robust predictor of functional outcome, while inner mean ICA was a significant predictor for macular thickness outcomes.

WIDE-FIELD SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY OF DIABETIC TRACTIONAL RETINAL DETACHMENTS BEFORE AND AFTER SURGICAL REPAIR.

Wide-field (WF) swept-source (SS) optical coherence tomography angiography (SS-OCTA) was used to image diabetic tractional retinal detachments (TRDs) before and after pars plana vitrectomy. The clinical utility of SS-OCTA was assessed. Patients with diabetic TRDs were imaged prospectively with SS-OCTA. Ultrawide-field imaging was obtained when possible. Postoperative WF SS-OCTA imaging was performed. From January 2018 through December 2019, 31 eyes of 21 patients with diabetic TRDs were imaged. Wide-field SS-OCTA en-face images captured all areas of TRD and fibrovascular proliferation within the posterior pole that were visualized on ultrawide-field imaging. Optical coherence tomography angiography B-scans revealed the vascularity of preretinal membranes and identified areas of vitreoretinal traction and posterior vitreous detachment. Ten eyes underwent pars plana vitrectomy. Postoperative SS-OCTA imaging demonstrated removal of fibrovascular membranes, relief of traction, and resolution of TRDs. Retinal ischemia before and after surgical repair appeared similar. All clinically relevant features of diabetic TRDs were identified at baseline and assessed longitudinally after pars plana vitrectomy using WF SS-OCTA, which showed resolution of vitreoretinal traction and no apparent change in the status of retinal perfusion after surgery. If the media are clear and fixation is adequate, WF SS-OCTA is likely the only imaging modality needed for the diagnosis and longitudinal evaluation of diabetic TRDs.

In vitro detection of structural changes in chondrogenic mesenchymal stem cell pellets at the nano-scale using nano-sensitive optical coherance tomography

In vitro detection of structural changes in chondrogenic mesenchymal stem cell pellets at the nano-scale using nano-sensitive optical coherance tomography

Change in the Foveal Avascular Zone and Macular Capillary Network Density after Hyperbaric Oxygen Therapy in Healthy Retina.

PurposeThis study aimed to evaluate responses in retinal tissue by swept source OCT angiography (OCT-A) to hyperoxia after hyperbaric oxygen (HBO2) therapy.Methods The study was conducted in volunteers who received HBO2 treatment but did not have any eye disease. Patients underwent detailed eye examinations including dilated fundus examination, visual acuity, and refraction before being admitted for HBO2 therapy. Measurements were made before and immediately after HBO2 therapy. Enface images of the retinal vasculature were obtained from the superficial and deep retinal plexus (SP/DP). Quantitative analysis of the vessel density (VD) and foveal avascular zone (FAZ) area was performed.Results In total, 31 patients (15 female) with healthy retina were included in the study. The mean age was 42.8 years. The mean SP vascular density measurements before HBO2 therapy for the right and left eyes were 15.18 1.2 mm and 15.01 1.3 mm, respectively; the measurements after HBO2 therapy for the right and left eyes were 14.34 1.4 mm and 14.48 1.19 mm. The mean DP vascular density measurements before HBO2 therapy for the right and left eyes were 16.03 1.69 mm and 16.1 1.45 mm, respectively; the measurements after HBO2 therapy for the right and left eyes were 15.02 1.65 mm and 15.12 2.16 mm, respectively. Reduction of mean VD in superficial and deep plexus after HBO2 was statistically significant (P = 0.001 and P = 0.000, respectively). Changes in mean FAZ area before and after HBO2 therapy were not statistically significant (P = 0.719).Conclusion The healthy retina responds to oxygen supersaturation with HBO2 therapy by eventually decreasing vascular density in all layers. These findings may be important for further studies especially related to retina and choroidal oxygenation.

Framework for quantitative three-dimensional choroidal vasculature analysis using optical coherence tomography.

Choroidal vasculature plays an important role in the pathogenesis of retinal diseases, such as myopic maculopathy, age-related macular degeneration, diabetic retinopathy, central serous chorioretinopathy, and ocular inflammatory diseases. Current optical coherence tomography (OCT) technology provides three-dimensional visualization of the choroidal angioarchitecture; however, quantitative measures remain challenging. Here, we propose and validate a framework to segment and quantify the choroidal vasculature from a prototype swept-source OCT (PLEX Elite 9000, Carl Zeiss Meditec, USA) using a 3×3 mm scan protocol centered on the macula. Enface images referenced from the retinal pigment epithelium were reconstructed from the volumetric data. The boundaries of the choroidal volume were automatically identified by tracking the choroidal vessel feature structure over the depth, and a selective sliding window was applied for segmenting the vessels adaptively from attenuation-corrected enface images. We achieved a segmentation accuracy of 96% ± 1% as compared with manual annotation, and a dice coefficient of 0.83 ± 0.04 for repeatability. Using this framework on both control (0.00 D to -2.00 D) and highly myopic (-8.00 D to -11.00 D) eyes, we report a decrease in choroidal vessel volume (p<0.001) in eyes with high myopia.

Perivenular fern-like paracentral acute middle maculopathy. En-face optical coherence tomography imaging

Perivenular fern-like paracentral acute middle maculopathy. En-face optical coherence tomography imaging

On the shape and structure of the murine pulmonary heart valve

Murine animal models are an established standard in translational research and provides a potential platform for studying heart valve disease. To date, studies on heart valve disease using murine models have been hindered by a lack of appropriate methodologies due to their small scale. In the present study, we developed a multi-scale, imaging-based approach to extract the functional structure and geometry for the murine heart valve. We chose the pulmonary valve (PV) to study, due to its importance in congenital heart valve disease. Excised pulmonary outflow tracts from eleven 1-year old C57BL/6J mice were fixed at 10, 20, and 30 mmHg to simulate physiological loading. Micro-computed tomography was used to reconstruct the 3D organ-level PV geometry, which was then spatially correlated with serial en-face scanning electron microscopy imaging to quantify local collagen fiber distributions. From the acquired volume renderings, we obtained the geometric descriptors of the murine PV under increasing transvalvular pressures, which demonstrated remarkable consistency. Results to date suggest that the preferred collagen orientation was predominantly in the circumferential direction, as in larger mammalian valves. The present study represents a first step in establishing organ-level murine models for the study of heart valve disease.

Glaucoma classification based on scanning laser ophthalmoscopic images using a deep learning ensemble method.

This study aimed to assess the utility of optic nerve head (onh) en-face images, captured with scanning laser ophthalmoscopy (slo) during standard optical coherence tomography (oct) imaging of the posterior segment, and demonstrate the potential of deep learning (dl) ensemble method that operates in a low data regime to differentiate glaucoma patients from healthy controls. The two groups of subjects were initially categorized based on a range of clinical tests including measurements of intraocular pressure, visual fields, oct derived retinal nerve fiber layer (rnfl) thickness and dilated stereoscopic examination of onh. 227 slo images of 227 subjects (105 glaucoma patients and 122 controls) were used. A new task-specific convolutional neural network architecture was developed for slo image-based classification. To benchmark the results of the proposed method, a range of classifiers were tested including five machine learning methods to classify glaucoma based on rnfl thickness—a well-known biomarker in glaucoma diagnostics, ensemble classifier based on inception v3 architecture, and classifiers based on features extracted from the image. The study shows that cross-validation dl ensemble based on slo images achieved a good discrimination performance with up to 0.962 of balanced accuracy, outperforming all of the other tested classifiers.

A Simple Subjective Evaluation of Enface OCT Reflectance Images Distinguishes Glaucoma From Healthy Eyes.

PurposeWe present a subjective approach to detecting glaucomatous defects in enface images and assess its diagnostic performance. We also test the hypothesis that if reflectivity changes precede thickness changes in glaucoma there should be reduced correlation between the modalities in glaucoma compared to controls.MethodsTwenty glaucoma participants and 20 age-matched controls underwent high-resolution OCT scans of one eye. 4 µm-thick enface slabs were constructed through the retina. Enface indices were depths of first gap in visible retinal nerve fiber bundles (RNFBs) and last visible bundle, subjectively evaluated in six sectors of a 3.5 mm circle around the optic disc. Retinal nerve fiber layer thickness (RNFLT) along the same circle was extracted at angles corresponding to enface indices. Between-group differences were tested by linear mixed models. Diagnostic performance was measured by partial receiver operating characteristic area (pAUC).Results First gap and last visible bundle were closer to the inner limiting membrane in glaucoma eyes (both P < 0.0001). Enface indices showed excellent diagnostic performance (pAUCs 0.63–1.00), similar to RNFLT (pAUCs 0.63–0.95). Correlation between enface and RNFLT parameters was strong in healthy (r = 0.81–0.92) and glaucoma eyes (r = 0.73–0.80).ConclusionsThis simple subjective method reliably identifies glaucomatous defects in enface images with diagnostic performance at least as good as existing thickness indices. Thickness and reflectivity were similarly related in healthy and glaucoma eyes, providing no strong evidence of reflectivity loss preceding thinning. Objective analyses may realize further potential of enface OCT images in glaucoma.Translational RelevanceNovel enface OCT indices may aid glaucoma diagnosis.

Cystic maculopathy of the inner nuclear layer in glaucoma patients

The study aimed to detect and describe glaucoma-related pseudocystic abnormalities at the internal nuclear layer (INL) of the macula using OCT, in relation with visual field defects and other clinical data. Primary open-angle glaucoma patients presenting for a follow-up visit were consecutively included over 5 months and underwent clinical examination, OCT imaging, and central 10-2 visual field testing. OCT measures included the thickness of the peripapillary retinal nerve fiber layer (RNFL) and macular ganglion cell complex (GCC), together with an analysis of B-Scans and en-face images. All data provided by OCT were analyzed and compared with the visual field testing. Fourteen patients out of 216 showed pseudocysts in the INL of the macula. These cysts were hyporeflective, fusiform, and of variable size (15 to 25μm) and were always associated with a thinning of both the RNFL and GCC. En-face OCT showed evidence of a distribution of cysts in the macular region, based on the appearance of numerous, dense hyporeflective pits whose localization matched precisely with the vision loss as assessed by central 10-2 visual field testing. No other correlations were found. Pseudocysts of the internal nuclear layer of the macular region are found in some cases of chronic glaucoma. Their presence is always associated with a scotoma in the visual field and appear to constitute a marker for glaucoma progression. Glaucoma-related central pseudocysts could result from Müller cell changes, excitotoxicity, and/or trans-synaptic retrograde degeneration. The presence of pseudocysts could be a marker of a particular subpopulation whose features remain to be determined.