Optical coherence tomography (OCT) angiography (OCTA) is a novel, noninvasive, three-dimensional imaging technique that allows for the visualization of intravascular flow in the microvasculature. ...Swept-source OCT technology utilizes longer-wavelength infrared light than conventional spectral-domain OCT. This enables improved penetration into tissue and imaging through optical opacities and is invisible to the subject. Topcon has recently developed an innovative OCTA algorithm, OCTARA (OCTA Ratio Analysis), which benefits from being paired with swept-source OCT. OCTARA aims to provide improved detection sensitivity of low blood flow and reduced motion artifacts without compromising axial resolution. In this chapter, we describe the implementation of OCTARA with swept-source OCT technology, the technical specifications of acquisition (e.g. the number of scans, area of examination field, etc.) along with the algorithm's function and principles for analysis of B-scan data to achieve angiographic visualization. Examples of OCTA scans performed using the OCTARA algorithm and a comparison of these scans with images obtained using other technologies are also presented.
To understand the problems involved in using global OCT measures for detecting progression in early glaucoma.
Eyes from 76 patients and 28 healthy controls (HC) had a least two OCT scans at least 1 ...year apart. To determine the 95% confidence intervals (CI), 151 eyes (49 HC and 102 patients) had at least two scans within 6 months. All eyes had 24-2 mean deviation ≥-6dB. The average (global) thicknesses of the circumpapillary retinal nerve fibre layer (cRNFL), G
, and of the retinal ganglion cell layer plus inner plexiform layer (RGCLP), G
, were calculated. Using quantile regression, the 95% CI intervals were determined. Eyes outside the CIs were classified as "progressors." For a reference standard (RS), four experts evaluated OCT and VF information.
Compared to the RS, 31 of the 76 (40.8%) patient eyes were identified as progressors (RS-P), and 45 patient, and all 28 HC, eyes as nonprogressors (RS-NP). The metrics missed (false negative, FN) 15 (48%) (G
) and 9 (29%) (G
) of the 31 RS-P. Further, G
and/or G
falsely identified (false positive, FP) 10 (22.2%) of 45 patient RS-NP eyes and 7 (25%) of the 28 HC eyes as progressing. Post-hoc analysis identified three reasons (segmentation, centring, and local damage) for these errors.
Global metrics lead to FPs and FNs because of problems inherent in OCT scanning (segmentation and centring), and to FNs because they can miss local damage. These problems are difficult, if not impossible, to correct, and raise concerns about the advisability of using G
and G
for detecting progression.
To demonstrate the effect of intravitreal bevacizumab (IVB) on the size and vascularity of the fibro-vascular complex with the optical coherence tomography angiography (OCTA) before pars plana ...vitrectomy (PPV).
Observational case series of three eyes with active diabetic fibro-vascular complex and tractional retinal detachment (TRD) who underwent IVB (1.25 mg/0.05 ml) two days before proceeding to PPV. OCTA was carried out prior to IVB, two days after IVB and six weeks after PPV.
OCTA showed a reduction in the size and calibre of the diabetic fibro-vascular complex two days after IVB in all the cases. Consequently, there was less traumatic dissection of the fibro-vascular membranes during PPV and thus reduced chances of intraoperative and postoperative vitreous cavity bleeding. One case showed mild hemorrhage in the posterior vitreous on the second day post-injection which implies the increased traction caused by IVB.
In this case series, we have used OCTA to demonstrate how IVB is highly effective in reducing the vascularity of diabetic fibro-vascular membranes. This finding also suggests that the use of IVB before PPV in the management of diabetic TRD could also be much shorter than the advocated standard practice of one week in most institutions.
A method for detecting glaucoma based only on optical coherence tomography (OCT) is of potential value for routine clinical decisions, for inclusion criteria for research studies and trials, for ...large-scale clinical screening, as well as for the development of artificial intelligence (AI) decision models. Recent work suggests that the OCT probability (p-) maps, also known as deviation maps, can play a key role in an OCT-based method. However, artifacts seen on the p-maps of healthy control eyes can resemble patterns of damage due to glaucoma. We document in section 2 that these glaucoma-like artifacts are relatively common and are probably due to normal anatomical variations in healthy eyes. We also introduce a simple anatomical artifact model based upon known anatomical variations to help distinguish these artifacts from actual glaucomatous damage. In section 3, we apply this model to an OCT-based method for detecting glaucoma that starts with an examination of the retinal nerve fiber layer (RNFL) p-map. While this method requires a judgment by the clinician, sections 4 and 5 describe automated methods that do not. In section 4, the simple model helps explain the relatively poor performance of commonly employed summary statistics, including circumpapillary RNFL thickness. In section 5, the model helps account for the success of an AI deep learning model, which in turn validates our focus on the RNFL p-map. Finally, in section 6 we consider the implications of OCT-based methods for the clinic, research, screening, and the development of AI models.
•A method based upon only OCT can achieve excellent specificity and sensitivity.•A simple model of normal anatomical variation improves specificity.•The model helps explain the poor performance of common summary statistics.•An AI deep learning model has excellent sensitivity and specificity and validates the use of OCT.
We sought to test the hypothesis that a recently proposed pattern standard deviation (PSD) metric, based upon the 24-2 visual field (VF) test, as well as the PSD of the 10-2 VF, will miss central ...glaucomatous damage confirmed with an objective structure-function method.
Cross-sectional study.
A glaucoma (G) group (70 eyes/patients) diagnosed with glaucoma and a 24-2 mean deviation better than −6 dB and a healthy (H) group (45 eyes/patients) had 24-2 and 10-2 VFs and optical coherence tomography (OCT) scans twice within 4 weeks. The PSD(C24-2), based upon the central 12 points of the 24-2, was compared with the PSD(10-2). To evaluate central damage (CD) in G eyes with normal PSD(C24-2) values, a post hoc analysis was combined with a CD reference standard (CD-RS), which was based upon an objective, topographic comparison between abnormal points on the 10-2 VF and OCT probability maps.
The 115 PSD(C24-2) and PSD(10-2) values were significantly correlated (Spearman correclation coefficient: rho = 0.55; P < .001) and the number of G eyes (19) identified as abnormal by the PSD(C24-2) was not significantly different from the number (22) identified by the PSD(10-2) (P = .15). However, based upon the CD-RS, 44 of 70 G eyes were classified as abnormal. The PSD(C24-2) missed 27 (61%) of these 44 eyes, and the PSD(10-2) missed 23 (52%) of these eyes. Post hoc analysis revealed clear CD in most of these eyes.
Neither the PSD(C24-2) nor the PSD(10-2) metric is good measure of early CD. Instead we recommend a topographic approach based upon OCT probability maps and a 10-2 VF.
To assess the agreement between structural (optical coherence tomography OCT) and functional (visual field VF) glaucomatous damage with an automated method and deviation/probability maps, and to ...compare this method to a metric method.
Wide-field spectral-domain OCT scans, including the disc and macula, and 24-2 and 10-2 VFs were obtained from 45 healthy control (H) eyes/individuals, and 53 eyes/patients with 24-2 mean deviation (MD) better than -6 dB diagnosed as "definite glaucoma" (DG) by experts. Abnormal structure-abnormal function (aS-aF) agreement was assessed with an automated topographic (T) method based upon VF pattern deviation and OCT probability maps. Results were compared to a metric (M) method optimized for accuracy, (abnormal 24-2 glaucoma hemifield test GHT or pattern standard deviation PSD, or 10-2 PSD AND abnormal OCT quadrant).
For the T-method, 47 (88.7%) of the 53 DG eyes showed aS-aF agreement, compared to 2 (4.5%) of the 45 H eyes. The aS-aF agreement for these two H eyes was easily identified as mistaken, and did not replicate on a subsequent test. Without the 10-2, the aS-aF agreement decreased from 47 to 34 (64.2%) of 53 DG eyes. For the M-method, 37 (69.8%) of the 53 DG eyes showed aS-aF agreement, while omitting the 10-2 VF resulted in agreement in only 33 (62.3%) eyes.
There is good agreement between structural and functional damage, even in eyes with confirmed early glaucomatous damage, if both 24-2 and 10-2 VFs are obtained, and abnormal locations on the VFs are compared to abnormal regions seen on OCT macular and disc scans. This can be done in an objective, automated fashion. (ClinicalTrials.gov number, NCT02547740.).
The central macula contains a thick donut shaped region of the ganglion cell layer (GCL) that surrounds the fovea. This region, which is about 12 degrees (3.5 mm) in diameter, is essential for ...everyday functions such as driving, reading, and face recognition. Here, we describe a model of progression of glaucomatous damage to this GCL donut. This model is based upon assumptions supported by the literature, and it predicts the patterns of glaucomatous damage to the GCL donut, as seen with optical coherence tomography (OCT). After describing the assumptions and predictions of this model, we test the model against data from our laboratory, as well as from the literature. Finally, three uses of the model are illustrated. One, it provides an aid to help clinicians focus on the essential central macula and to alert them to look for other, non-glaucomatous causes, when the GCL damage does not fit the pattern predicted by the model. Second, the patterns of progression predicted by the model suggest alternative end points for clinical trials. Finally, the model provides a heuristic for future research concerning the anatomic basis of glaucomatous damage.
To evaluate the International Classification of Disease, Tenth Revision (ICD-10) codes used for glaucoma severity classification, which are based on the location of visual field (VF) defects; given ...the known poor sensitivity of the 24-2 visual field test to early disease and macular damage, we hypothesized that the ICD-10 codes would not accurately reflect the extent of glaucomatous damage.
Retrospective validity and reliability analysis.
We evaluated 80 eyes with glaucomatous optic neuropathy (GON). Masked reviewers assigned an ICD-10 severity grade based on 24-2 VF. Two additional masked examiners determined the presence of optical coherence tomography (OCT) structural damage in each hemifield and/or central 5 degrees to define an OCT-based equivalent ICD-10 classification.
A total of 80 eyes with GON were classified as mild, moderate and advanced in 15, 23, and 42 cases, respectively, based on the 24-2 VF, and in 6, 7, and 67 cases, respectively, based on OCT. The OCT classifications were more severe in 29 of 80 cases (36%). In 33 cases (41.3%), macular damage detected by OCT was missed by the 24-2. In 4 of 80 cases (5%), the VF overestimated the severity, likely due to variability of the 24-2 test.
The ICD-10 system relies solely on damage seen on the 24-2 and as provides a 24-2 functional score rather than a “glaucoma” severity score. OCT revealed wide variation of damage across grades, with a significant proportion of the eyes showing macular structural damage missed with the 24-2 VF. Adding OCT information to the ICD-10 system would help it to more accurately reflect the extent of glaucomatous damage.
Purpose:
To identify a new cortical vitreous segmentation protocol for non invasive standardised investigation of Neovascularisation (NV) with detection of regression of NV activity in Proliferative ...Diabetic Retinopathy (PDR).
Design:
Retrospective study.
Participants:
One hundred and eighty-six eyes of 93 consecutive diabetic patients (mean age: 52.6 ± 11.0 years) imaged using Topcon Triton® Swept-Source Optical Coherence Tomography Angiography (SS-OCTA) from June 2015 to January 2017.
Methods:
Scans were performed through the macula, optic disc and areas of possible NV in mid-peripheral retina using 6 × 6 mm and/or 9 × 9 mm raster-patterns in three segmentation protocols: Vitreo-Retinal (VRS), Outer-Vitreous (OVS) and Core-Vitreous Segmentation (CVS). Any suspicion of PDR was confirmed in all patients by Heidelberg® Widefield-Fundus-Fluorescein-Angiography (WF-FFA) and/or Optos® Ultra-WF-FFA (UWF-FFA). Inter-observer reproducibility of NV diagnosis and agreement between SS-OCTA and UWF-FFA were assessed. Primary outcome was the identification of an effective and reproducible segmentation protocol. Secondary outcome was the identification of NV regression after treatment.
Results:
Sensitivity-specificity reached, respectively, the value of 100 to 100 in detecting NVD, and 96.6 to 100 in detecting NVE in compared areas. SS-OCTA was able to confirm absence of blood flow within the residual NV plexus when using VRS protocol in 30 eyes in which regression of NV with absence of leakage was documented on FFA.
Conclusion:
Three segmentation protocols (VRS, OVS and CVS) with different but complementary characteristics, allowed a reproducible and standardised investigation of NVD and NVE. The proposed new SS-OCTA cortical vitreous segmentation protocols may be of value when identifying and assessing NV-activity (VRS, OVS and CVS) or NV-regression (VRS) in PDR and therefore, response to therapy.
PDF
