Avoiding Clinical Misinterpretation and Artifacts of Optical Coherence Tomography Analysis of the Optic Nerve, Retinal Nerve Fiber Layer, and Ganglion Cell Layer

Optical coherence tomography: implications for neurology

PURPOSE OF REVIEW

This article explores the role of optical coherence tomography (OCT) in neurology practice, particularly in diagnosing and monitoring conditions such as papilledema, optic neuritis, and retinal artery occlusion. OCT has been increasingly utilized as a noninvasive and effective tool for detecting and monitoring neuroaxonal damage in the visual pathway, which is important for early intervention and improved patient outcomes across a variety of neurologic conditions.

RECENT FINDINGS

OCT as an imaging modality continues to demonstrate its utility in quantifying optic nerve and retinal changes reflecting neuroaxonal injury, including, peripapillary retinal nerve fiber layer (pRNFL) thickness and macular ganglion cell layer thickness (or volume). This review focuses on recent evidence regarding the utilization of this modality in diagnosing, monitoring, and quantifying treatment responses in patients with papilledema, optic neuritis, and retinal artery occlusion. Advances in OCT technology, including deep learning algorithms, continue to enhance the diagnostic accuracy and predictive capabilities in the field of neuro-ophthalmology.

SUMMARY

In recent years, OCT has become an essential tool in neuro-ophthalmic assessment, offering precise structural and anatomical assessments that support diagnosis, treatment planning, and monitoring of conditions affecting the visual pathway. Ongoing advances in OCT technology are expected to further enhance its clinical utility.

Explainable Deep Learning for Glaucomatous Visual Field Prediction: Artifact Correction Enhances Transformer Models

Purpose

The purpose of this study was to develop a deep learning approach that restores artifact-laden optical coherence tomography (OCT) scans and predicts functional loss on the 24-2 Humphrey Visual Field (HVF) test.

Methods

This cross-sectional, retrospective study used 1674 visual field (VF)-OCT pairs from 951 eyes for training and 429 pairs from 345 eyes for testing. Peripapillary retinal nerve fiber layer (RNFL) thickness map artifacts were corrected using a generative diffusion model. Three convolutional neural networks and 2 transformer-based models were trained on original and artifact-corrected datasets to estimate 54 sensitivity thresholds of the 24-2 HVF test.

Results

Predictive performances were calculated using root mean square error (RMSE) and mean absolute error (MAE), with explainability evaluated through GradCAM, attention maps, and dimensionality reduction techniques. The Distillation with No Labels (DINO) Vision Transformers (ViT) trained on artifact-corrected datasets achieved the highest accuracy (RMSE, 95% confidence interval [CI] = 4.44, 95% CI = 4.07, 4.82 decibel [dB], MAE = 3.46, 95% CI = 3.14, 3.79 dB), and the greatest interpretability, showing improvements of 0.15 dB in global RMSE and MAE (P < 0.05) compared to the performance on original maps. Feature maps and visualization tools indicate that artifacts compromise DINO-ViT's predictive ability but improve with artifact correction.

Conclusions

Combining self-supervised ViTs with generative artifact correction enhances the correlation between glaucomatous structures and functions.

Translational Relevance

Our approach offers a comprehensive tool for glaucoma management, facilitates the exploration of structure-function correlations in research, and underscores the importance of addressing artifacts in the clinical interpretation of OCT.

Total retinal thickness is an important factor in evaluating diabetic retinal neurodegeneration

OBJECTIVE

Macular retinal nerve fibre layer (mRNFL) and ganglion cell-inner plexiform layer thickness (GC-IPL) measurements are important markers of diabetic retinal neurodegeneration (DRN). In this cross-sectional study, we aimed to quantify the contribution of total retinal thickness (TRT) and other factors in the variation of mRNFL and GC-IPL thickness among participants with diabetes.

METHODS AND ANALYSIS

We used macular-centred spectral domain-optical coherence tomography scans from participants with diabetes in the UK Biobank. Two multiple linear regression models (prior to and after adjusting for TRT) were used to determine factors associated with mRNFL and GC-IPL thicknesses. A p value of less than 0.05 was considered statistically significant.

RESULTS

A total of 3832 eyes from 3832 participants with diabetes were analysed. Factors that explained the greatest variation in thickness were TRT (20.9% for mRNFL and 57.2% for GC-IPL), followed by spherical equivalent (8.0% for mRNFL only), gender (2.2% for mRNFL only) and age (1.4% for GC-IPL only). Other factors significantly associated with mRNFL and/or GC-IPL thickness explained less than 1% of the variation in their thicknesses. Self-reported ancestral background was not significantly associated with mRNFL thickness after accounting for TRT.

CONCLUSIONS

Although many factors were significantly associated with mRNFL and GC-IPL thickness in participants with diabetes, they accounted for a fraction of the variation in the thickness of both layers. TRT explained most of the variation in these measurements, hence accounting for TRT is needed when using these metrics to evaluate DRN.

Multimodal photoacoustic microscopy and optical coherence tomography ocular biomarker imaging in Alzheimer's disease in mice

Alzheimer's disease (AD) is a neurodegenerative disease characterized by amyloid beta (Aβ)-containing extracellular plaques and tau-containing intracellular neurofibrillary tangles. Reliable and more accessible biomarkers along with associated imaging methods are essential for early diagnosis and to develop effective therapeutic interventions. Described here is an integrated photoacoustic microscopy (PAM) and optical coherence tomography (OCT) dual-modality imaging system for multiple ocular biomarker imaging in an AD mouse model. Anti-Aβ-conjugated Au nanochains (AuNCs) were engineered and administered to the mice to provide molecular contrast of Aβ. The retinal vasculature structure and Aβ deposition in AD mice and wild-type (WT) mice were imaged simultaneously by dual-wavelength PAM. OCT distinguished significant differences in retinal layer thickness between AD and WT animals. With the unique ability of imaging the multiple ocular biomarkers via a coaxial multimodality imaging system, the proposed system provides a new tool for investigating the progression of AD in animal models, which could contribute to preclinical studies of AD.

Imaging the optic nerve with optical coherence tomography

Optical coherence tomography (OCT) is a non-invasive imaging technology, which may be used to generate in vivo quantitative and qualitative measures of retinal structure. In terms of quantitative metrics, peripapillary retinal nerve fiber layer (pRNFL) thickness provides an indirect evaluation of axonal integrity within the optic nerve. Ganglion layer measures derived from macular scans indirectly reflect retinal ganglion cell status. Notably, ganglion layer indices are platform dependent and may include macular ganglion cell inner plexiform layer (mGCIPL), ganglion cell layer (GCL), and ganglion cell complex (GCC) analyses of thickness or volume. Interpreted together, pRNFL thickness and ganglion layer values can be used to diagnose optic neuropathies, monitor disease progression, and gauge response to therapeutic interventions for neuro-ophthalmic conditions. Qualitative assessments of the optic nerve head, using cross-sectional transverse axial, en face, and circular OCT imaging, may help distinguish papilledema from pseudopapilloedema, and identify outer retinal pathology. Innovations in OCT protocols and approaches including enhanced depth imaging (EDI), swept source (SS) techniques, and angiography (OCTA) may offer future insights regarding the potential pathogenesis of different optic neuropathies. Finally, recent developments in artificial intelligence (AI) utilizing OCT images may overcome longstanding challenges, which have plagued non-vision specialists who often struggle to perform reliable ophthalmoscopy. In this review, we aim to discuss the benefits and pitfalls of OCT, consider the practical applications of this technology in the assessment of optic neuropathies, and highlight scientific discoveries in the realm of optic nerve imaging that will ultimately change how neuro-ophthalmologists care for patients.

Utility of ganglion cells for the evaluation of anterior visual pathway pathology: a review

The management of optic neuropathy is fundamental to neuro-ophthalmic practice. Following the invention of the ophthalmoscope, clinicians, for a century or more, relied upon fundus examination in the evaluation of optic neuropathy. However, the advent of optical coherence tomography, based on the principle of backscattering of light and interferometry, has revolutionized the analysis of optic nerve and retinal disorders. Optical coherence tomography has proven of particular value in the measurement, at the micron level, of the peripapillary retinal nerve fibre layer and the ganglion cell layer. These measurements have proven critical in the differential diagnosis and monitoring of optic neuropathy. Specifically, thinning of the peripapillary nerve fibre layer provides evidence of axonal loss affecting any sector of the optic nerve. Thinning of the macular ganglion cell layer, on the other hand, shows a more precise correlation with visual deficits due to retrograde degeneration following optic nerve damage, although limited to central retina. In daily practise, optical coherence tomography is of great value in assessing the diagnosis, prognosis and response to treatment in optic neuropathy. Particular advances have been made, for example, in the assessment of optic neuritis, papilloedema and chiasmal compression which have translated to everyday practice. As with any other imaging technology the clinician must have a clear understanding of acquisition artefacts. A further issue is the relatively limited normative database in sub-populations such as the young and individuals with a refractive error > + 5 or < -5 dioptres.

Diagnostic dilemma of papilledema and pseudopapilledema

BACKGROUND

Papilledema is the optic disc swelling caused by increased intracranial pressure (ICP) that can damage the optic nerve and cause subsequent vision loss. Pseudopapilledema refers to optic disc elevation without peripapillary fluid that can arise from several optic disc disorders, with optic disc drusen (ODD) being the most frequent cause. Occasionally, pseudopapilledema patients are mistakenly diagnosed as papilledema, leading to the possibility of unneeded procedures. We aim to thoroughly examine the most current evidence on papilledema and pseudopapilledema causes and several methods for distinguishing between both conditions.

METHODS

An extensive literature search was conducted on electronic databases including PubMed and google scholar using keywords that were relevant to the assessed pathologies. Data were collected and then summarized in comprehensive form.

RESULTS

Various techniques are employed to distinguish between papilledema and pseudopapilledema. These techniques include Fundus fluorescein angiography, optical coherence tomography, ultrasonography, and magnetic resonance imaging. Lumbar puncture and other invasive procedures may be needed if results are suspicious.

CONCLUSION

Papilledema is a sight-threatening condition that may lead to visual affection. Many disc conditions may mimic papilledema. Accordingly, differentiation between papilledema and pseudopailledema is crucial and can be conducted through many modalities.

Anatomical Features can Affect OCT Measures Used for Clinical Decisions and Clinical Trial Endpoints

Purpose

To understand the association between anatomical parameters of healthy eyes and optical coherence tomography (OCT) circumpapillary retinal nerve fiber layer (cpRNFL) thickness measurements.

Methods

OCT cpRNFL thickness was obtained from 396 healthy eyes in a commercial reference database (RDB). The temporal quadrant (TQ), superior quadrant (SQ), inferior quadrant (IQ), and global (G) cpRNFL thicknesses were analyzed. The commercial OCT devices code these values based on percentiles (red, <1%; yellow, ≥1% and <5%), after taking age and disc area into consideration. Four anatomical parameters were assessed: fovea-to-disc distance, an estimate of axial length, and the locations of the superior and the inferior peaks of the cpRNFL thickness curve. Pearson correlation values were obtained for the parameters and the thickness measures of each of the four cpRNFL regions, and t-tests were performed between the cpRNFL thicknesses coded as abnormal (red or yellow, <5%) versus normal (≥5%).

Results

For each of the four anatomical parameters, the correlation with the thickness of one or more of the TQ, SQ, IQ, and G regions exceeded the correlation with age or disc area. All four parameters were significantly (P < 0.001) associated with the abnormal cpRNFL values. The significant parameters were not the same for the different regions; for example, a parameter could be negatively correlated for the TQ but positively correlated with the SQ or IQ.

Conclusions

In addition to age and disc area, which are used for inferences in normative databases, four anatomical parameters are associated with cpRNFL thickness.

Translational Relevance

Taking these additional anatomical parameters into consideration should aid diagnostic accuracy.

Case series: Superficial plexus en face may aid distinction of retinal nerve fiber layer loss from diabetic retinal ischemia versus glaucoma

PURPOSE

This study aimed to demonstrate that the pattern and degree of capillary bed dropout in early glaucoma appear different on OCT-A superficial plexus en-face slabs compared with retinal ischemia. RNFL loss associated with retinal ischemia in diabetic patients may be explained and accounted for by overlying the RNFL deviation map on a superficial plexus en-face montage.

CASE REPORTS

Three middle-aged White men with diabetes mellitus showed cup-to-disc ratios of approximately 0.7 and RNFL and ganglion thinning. Each patient had several Cirrus OCT and OCT-A scans taken of the posterior pole. The OCT-A en-face images demonstrated specific patterns of superficial capillary dropout. The appearance of superficial plexus capillary dropout in one case of glaucoma is contrasted against two cases of retinal ischemia.

CONCLUSIONS

Early glaucoma appears to be associated with incomplete capillary bed dropout that extends from macular regions to the disc in a wedge- or arc-shaped pattern. Diabetic retinal ischemia appears to be associated with well-defined patchy and polygonal pockets of complete capillary bed obliteration that may not extend back to the disc. If an RNFL deviation map is superimposed over the superficial plexus en-face montage, areas of RNFL loss may correlate with and thus be well accounted for by areas of retinal ischemia in cases with RNFL thinning likely from ischemia. This approach may supplement inspection of OCT B-scans for focal retinal thinning when trying to differentiate RNFL and ganglion cell loss from retinal ischemia versus glaucoma in patients with diabetes. Formal research studies are needed to validate our observations and proposed use of OCT-A together with OCT in these patients.

Artifacts in OCT Retinal Nerve Fiber Layer Imaging in Patients with Boston Keratoprosthesis Type 1

PURPOSE

To determine the clinical utility of OCT retinal nerve fiber layer (OCT RNFL) imaging for glaucoma evaluation in patients with Boston keratoprosthesis type 1 (KPro) by investigating imaging artifacts.

DESIGN

Case-control study.

SUBJECTS

Patients with KPro and without KPro (controls) matched for age, gender, and glaucoma diagnosis.

METHODS

The most recent Cirrus OCT RNFL scan from 1 eye was categorized as having good signal strength (SS; ≥ 6 out of 10) or poor SS (< 6). Those with good SS were analyzed by 2 independent reviewers for artifacts. Images with good SS and no artifacts affecting the scanning circle were considered useful for glaucoma evaluation.

MAIN OUTCOME MEASURES

The incidence of poor SS and artifacts in OCT RNFL images; patient characteristics associated with useful scans.

RESULTS

Sixty-five patients with KPro and 75 controls were included; 89.2% of KPro patients and 89.3% of control subjects had glaucoma (P = 0.98). Forty percent of KPro patients and 5.3% of controls had poor SS (P < 0.001). The proportion of images with either poor SS or artifacts was similar in KPro (76.9%) vs. controls (72.0%, P = 0.51). The most common artifacts in both groups were missing data (43.6%, 53.2%, respectively, P = 0.32) and motion artifact (25.6%, 19.7%, respectively, P = 0.47). Images were useful for glaucoma evaluation in 43.1% of KPro patients and in 69.3% of controls (P = 0.002). In the KPro group, patients with useful OCT scans, compared with those without, had better visual acuity (0.4 ± 0.3 vs. 0.9 ± 0.7 logarithm of the minimum angle of resolution, P = 0.004), and did not have congenital corneal pathologies (0.0% vs. 24.3%, P = 0.008). A multivariate analysis showed that KPro patients with older age had higher odds of useful OCT images (odds ratio, 1.05; P = 0.03). Among KPro patients with useful OCT scans, retinal nerve fiber layer thickness correlated with observed cup-to-disc ratio (Pearson correlation: r = -0.42, P = 0.03).

CONCLUSIONS

The rate of OCT RNFL images with either poor signal strength or artifacts in the KPro and control population was comparable. In patients with KPro, where intraocular pressure measurements are difficult and glaucoma is highly prevalent and often severe, OCT RNFL imaging can be useful for glaucoma evaluation.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Glaucoma Detection Using Optical Coherence Tomography: Reviewing the Pitfalls of Comparison to Normative Data

PRCIS

Optical coherence tomography is essential in managing glaucoma. This review describes various artifacts that originate from using a normative database to compare the individual's scans. This is a review paper regarding artifacts in optical coherence tomography imaging for glaucoma arising from using a normative database as a reference for healthy retinal nerve fiber layer and ganglion cell layer.

Quantitative analysis of deep learning-based denoising model efficacy on optical coherence tomography images with different noise levels

BACKGROUND

To quantitatively evaluate the effectiveness of the Noise2Noise (N2N) model, a deep learning (DL)-based noise reduction algorithm, on enhanced depth imaging-optical coherence tomography (EDI-OCT) images with different noise levels.

METHODS

The study included 30 subfoveal EDI-OCT images averaged with 100 frames from 30 healthy participants. Artificial Gaussian noise at 25.00, 50.00, and 75.00 standard deviations were added to the averaged (original) images, and the images were grouped as 25N, 50N, and 75N. Afterward, noise-added images were denoised with the N2N model and grouped as 25dN, 50dN, and 75dN, according to previous noise levels. The choroidal vascularity index (CVI) and deep choroidal contrast-to-noise ratio (CNR) were calculated for all images, and noise-added and denoised images were compared with the original images. The structural similarity of the noise-added and denoised images to the original images was assessed by the Multi-Scale Structural Similarity Index (MS-SSI).

RESULTS

The CVI and CNR parameters of the original images (68.08 ± 2.47 %, and 9.71 ± 2.80) did not differ from the only 25dN images (67.97 ± 2.34 % and 8.50 ± 2.43) (p:1.000, and p:0.062, respectively). Noise reduction improved the MS-SSI at each noise level (p < 0.001). However, the highest MS-SSI was achieved in 25dN images.

CONCLUSIONS

The DL-based N2N denoising model can be used effectively for images with low noise levels, but at increasing noise levels, this model may be insufficient to provide both the original structural features of the choroid and structural similarity to the original image.

A Model of Progression to Help Identify Macular Damage Due to Glaucoma

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.

Peripapillary Vascular Density in Childhood Glaucoma: A Pilot Comparative Study with Age and Sex Matched Healthy Subjects

PURPOSE

The aim of this study concerns the evaluation of peripapillary vessel indices in childhood glaucoma (CG) and healthy subjects.

MATERIAL AND METHODS

In this prospective, unicenter, observational cross-sectional study, patients with CG and age and sex-matched healthy subjects were included. We compared retinal nerve fiber layer (RNFL) measurements in optical coherence tomography (OCT), peripapillary vessel density (PVD), and the flux index (FI) of the superficial vascular plexus from OCT angiography (OCT-A) between CG patients and control groups.

RESULTS

We included 39 patients (68 eyes) with CG and 50 (95 eyes) healthy subjects. The peripapillary RNFL thickness, vessel density, and flux index were significantly lower in the CG group than in the control group. The mean PVD of CG patients was 0.52 ± 0.043%, compared with 0.55 ± 0.014%, p < 0.0001 in healthy subjects. The mean FI was 0.32 ± 0.054 versus 0.37 ± 0.028, p < 0.0001, in CG patients and healthy subjects, respectively. PVD and FI in the superior, inferior, and temporal sectors were significantly lower in CG. The peripapillary RNFL thickness showed a higher area under the ROC curve (AUROC) for discriminating healthy and CG eyes and was significantly different than the PVD (0.797, 95%CI 0.726-0.869; p < 0.0001 vs. 0.664, 95%CI 0.574-0.752; p 0.00037), p 0.012.

CONCLUSIONS

PVD and FI show lower values in CG and correlate with RNFL thickness measurement but have lower diagnostic ability than RNFL thickness measurement. Our results reveal possible differences in the pathogenesis of microvascular compromise in childhood glaucoma patients.

Ancillary PanoMap OCT shows the progression of glaucomatous papillomacular bundle defect with disc haemorrhage on the fovea-disc axis

BACKGROUND/AIMS

To identify the spatial relationship between disc haemorrhage (DH) on the fovea-disc axis and retinal nerve fibre layer (RNFL) defect in the papillomacular bundle (PMB) using ancillary PanoMap optical coherence tomography (OCT).

METHODS

We investigated the presence and progression of spatially corresponding PMB defects in glaucomatous eyes with temporally located DH on the fovea-disc axis (FoDi-DH). We identified PMB defects using ancillary PanoMap OCT with guided progression analysis, in addition to red-free photographs.

RESULTS

We studied 36 eyes of 35 glaucoma patients with FoDi-DH, pre-existing PMB defects were observed in 18 eyes (50.0%) at the time and location of the initial FoDi-DH occurrence, 14 (38.9%) of which progressed during the follow-up period. New development of PMB defects occurred in 15 (41.7%) of 18 eyes without pre-existing PMB defects. Overall, FoDi-DH was associated with PMB defects in 33 (91.7%) eyes at locations spatially overlapping the PMB defect. Red-free photography and OCT were complementary in detecting PMB defects and progression. Among 47 cases, 20 were concordant, while 10 and 17 were detected only in photography and OCT, respectively. The central visual field defect increased significantly throughout the follow-up period (p=0.006).

CONCLUSION

Most FoDi-DH cases were related to the presence and progression of glaucomatous PMB defects at locations spatially overlapping the defect. OCT helped clarify changes in PMB defects detected by red-free photograph and the detection of photo-negative PMB defects as well. Similar to inferotemporal and superotemporal-direction DH, temporal DH on the PMB may be an indicator of ongoing RNFL damage that deserves close attention.

Intraocular Pressure and Rates of Macular Thinning in Glaucoma

PURPOSE

To evaluate the effect of intraocular pressure (IOP) on the rates of macular thickness (ganglion cell layer [GCL] and ganglion cell-inner plexiform layer [GCIPL]) change over time measured by spectral-domain (SD) OCT.

DESIGN

Retrospective cohort study.

PARTICIPANTS

Overall, 451 eyes of 256 patients with primary open-angle glaucoma.

METHODS

Data were extracted from the Duke Ophthalmic Registry, a database of electronic medical records of patients observed under routine clinical care at the Duke Eye Center, and satellite clinics. All records from patients with a minimum of 6 months of follow-up and at least 2 good-quality Spectralis SD-OCT macula scans were included. Linear mixed models were used to investigate the relationship between average IOP during follow-up and rates of GCL and GCIPL thickness change over time.

MAIN OUTCOME MEASURES

The effect of IOP on the rates of GCL and GCIPL thickness loss measured by SD-OCT.

RESULTS

Eyes had a mean follow-up of 1.8 ± 1.3 years, ranging from 0.5 to 10.2 years. The average rate of change for GCL thickness was -0.220 μm/year (95% confidence interval [CI], -0.268 to -0.172 μm/year) and for GCIPL thickness was -0.231 μm/year (95% CI, -0.302 to -0.160 μm/year). Each 1-mmHg higher mean IOP during follow-up was associated with an additional loss of -0.021 μm/year of GCL thickness (P = 0.001) and -0.032 μm/year of GCIPL thickness (P = 0.001) after adjusting for potentially confounding factors, such as baseline age, disease severity, sex, race, central corneal thickness, and follow-up time.

CONCLUSIONS

Higher IOP was significantly associated with faster rates of GCL and GCIPL loss over time measured by SD-OCT, even during relatively short follow-up times. These findings support the use of SD-OCT GCL and GCIPL thickness measurements as structural biomarkers for the evaluation of the efficacy of IOP-lowering therapies in slowing down the progression of glaucoma.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Peripapillary Vascular Density in Compressive Optic Neuropathy and Normal-Tension Glaucoma: A Severity-Controlled Comparison

Purpose

To investigate the differences in peripapillary vessel density (VD) between compressive optic neuropathy (CON) and normal-tension glaucoma (NTG).

Methods

We compared patients with chronic CON and NTG, particularly after strictly controlling the mean extent of macular damage by the area of the ganglion cell-inner plexiform layer (GCIPL) loss in optical coherence tomography (OCT). We compared retinal nerve fiber layer (RNFL) and GCIPL thickness from OCT and peripapillary and macular VD from OCT angiography (OCTA) between the CON and NTG groups.

Results

From the initial 184 patients with CON and 443 patients with OAG, we included 41 patients with CON (57 eyes) and 64 patients with NTG (75 eyes) with a comparable extent of macular GCIPL thinning. Under similar mean macular involvement, the peripapillary VD was significantly lower in the CON group than in the NTG group after considering the effects of age, spherical equivalent, visual field sensitivity, peripapillary RNFL (pRNFL) thickness, GCIPL thickness, and image quality scores (P < 0.001). Marked loss of VD in the temporal and nasal sectors in CON was notable, attributing to the significantly lower peripapillary VD compared to NTG.

Conclusions

Patients with CON had a significantly lower peripapillary VD than those with NTG under similar mean degrees of pRNFL thickness and GCIPL damage. Our results reveal the potential utility of OCTA VD besides OCT pRNFL thickness, in relation to different topographic patterns of pRNFL loss, and possible differences in the pathogenesis of microvascular compromise between CON and NTG.

Unexplained Vision Loss Associated With Intraocular Silicone Oil Tamponade in Rhegmatogenous Retinal Detachment Repair

Purpose: To evaluate the visual outcomes with unexplained vision loss during or after silicone oil (SO) tamponade. Methods: This multicenter retrospective case series comprised patients with unexplained vision loss associated with SO tamponade or its removal. Eyes with other clear secondary identifiable causes of vision loss were excluded. Results: Twenty-nine eyes of 28 patients (64% male) were identified. The mean age was 50 ± 13 years (range, 13-78 years). The mean duration of SO tamponade was 148 ± 38 days. Eighteen eyes (62%) developed unexplained vision loss while under SO; 11 (38%) had vision loss after SO removal. The most common optical coherence tomography (OCT) finding was ganglion cell layer (GCL) thinning (55%). Eyes with vision loss after SO removal had a mean logMAR best-corrected visual acuity (BCVA) of 0.6 ± 0.7 (Snellen 20/85) before SO tamponade and 1.2 ± 0.4 (20/340) before SO removal. By the last follow-up after SO removal, the BCVA had improved to 1.1 ± 0.4 (20/235). In eyes with vision loss after SO removal, the BCVA before SO removal was 0.7 ± 0.7 (20/104), which deteriorated to 1.4 ± 0.4 (20/458) 1 month after SO removal. By the last follow-up, the BCVA had improved to 1.0 ± 0.5 (20/219). Conclusions: Unexplained vision loss can occur during SO tamponade or after SO removal. Vision loss was associated with 1000-centistoke and 5000-centistoke oil and occurred in macula-off and macula-on retinal detachments. The duration of tamponade was 3 months or longer in the majority of eyes. Most eyes had GCL thinning on OCT. Gradual visual recovery can occur yet is often incomplete.

Defining the Phenotype and Prognosis of People With Idiopathic Intracranial Hypertension After Cerebrospinal Fluid Diversion Surgery

PURPOSE

To characterize the phenotype of patients with idiopathic intracranial hypertension (IIH) who received cerebrospinal (CSF) diversion surgery and to detail the trajectory of recovery.

DESIGN

Prospective cohort registry study.

METHODS

Patients with IIH with sight-threatening papilledema presenting to a single United Kingdom neuroscience center between 2019 and 2021 were included. Outcomes consisted of perimetric mean deviation (PMD) and optical coherence tomography measures of papilledema (retinal nerve fiber layer [RNFL]) and macular ganglion cell layer (GCL) in both eyes. Headache outcomes included monthly headache days (MHD). Logistic regression methods were used to model long-term outcomes.

RESULTS

Fifty-one patients without previous surgical interventions were included (92% female, mean age 28.1 years [SD 8.4], body mass index 37.4 kg/m2 [SD 9.7], mean days of follow-up 330 [SD 209]). Measurements before surgery showed mean PMD -11.4 dB (SD 9.7), RNFL 364 µm (SD 128), Frisén grade papilledema 4.3 (SD 0.9). and MHD 23 (SD 10.6). At 1 month postoperatively, RNFL and PMD had improved by 38% and 4%, respectively. At 4 months postoperatively, papilledema had resolved. GCL declined by 13% over 12 months. MHD reduced by 75% 3 months postoperatively before returning to baseline levels by 12 months. Five patients (9.8%) required revision surgeries.

CONCLUSIONS

Detailed characteristics of patients with sight-threatening IIH who received CSF diversion surgery and their typical postoperative recovery are presented. These parameters should guide physicians as to when patients with IIH may require surgery and enable the early identification of outliers who fail to respond. Papilledema and PMD recovered but GCL atrophy continued for 12 months. The implication of this delayed atrophy is unknown.

Case Report: Papilledema Secondary to Cerebral Venous Sinus Thrombosis after Severe COVID-19 Infection

SIGNIFICANCE

This case highlights ocular adverse effects of a rare, potentially life-threatening complication from coronavirus disease 2019 (COVID-19). Papilledema can occur because of increased intracranial pressure caused by cerebral venous sinus thrombosis, the incidence of which may be more likely in patients with a history of COVID-19 because of an induced hypercoagulable state.

PURPOSE

This case report presents a case of papilledema secondary to cerebral venous sinus thrombosis in a patient with a recent history of severe coronavirus disease (COVID-19).

CASE REPORT

A 29-year-old man hospitalized with a complicated course of coronavirus disease (COVID-19) was referred to the ophthalmology department for episodic blurry vision of both eyes and intermittent binocular diplopia. Clinical examination revealed diffuse bilateral optic disc edema. Magnetic resonance venography of the brain during his admission revealed subtotal occlusion of the right transverse sinus by thrombosis. At the time of diagnosis, the patient was already taking systemic anticoagulation therapy for treatment of a recent pulmonary embolism also thought to be induced by COVID-19. After additional treatment with acetazolamide, there was improvement in his optic nerve edema.

CONCLUSIONS

Cerebral venous sinus thrombosis, a serious and potentially life-threatening condition, can occur as a rare complication of COVID-19. In such cases, patients may develop increased intracranial pressure, papilledema, and subsequent vision loss. Magnetic resonance venography should be ordered in patients with suspected papilledema to help rule out the presence of cerebral venous sinus thrombosis.

Effects of Myopia on Rates of Change in Optical Coherence Tomography Measured Retinal Layer Thicknesses in People with Multiple Sclerosis and Healthy Controls

PURPOSE

To quantify the associations of myopia with longitudinal changes in retinal layer thicknesses in people with multiple sclerosis (PwMS) and healthy controls (HC).

METHODS

A cohort of PwMS and HC with recorded refractive error (RE) prospectively scanned on Cirrus HD-OCT at the Johns Hopkins MS Center was assessed for inclusion. Exclusion criteria included OCT follow-up < 6 months, ocular comorbidities, incidental OCT pathologies, and inadequate scan quality. Eyes were classified as having high myopia (HM) (RE≤ -6 diopters), low myopia (LM) (RE> -6 and ≤ -3 diopters), or no myopia (NM) (RE> -3 and ≤ +2.75). Linear mixed-effects regression models were used in analyses.

RESULTS

A total of 213 PwMS (eyes: 67 HM, 98 LM, 207 NM) and 80 HC (eyes: 26 HM, 37 LM, 93 NM) were included. Baseline average ganglion cell/inner plexiform (GCIPL) and peri-papillary retinal nerve fiber layer (pRNFL) thicknesses were lower in MS HM compared with MS NM (diff: -3.2 µm, 95% CI: -5.5 to -0.8, p = 0.008 and -5.3 µm, 95% CI: -9.0 to -1.7, p = 0.004, respectively), and similarly in HC HM, as compared with HC NM. Baseline superior, inferior, and nasal pRNFL thicknesses were lower in HM compared with NM, while temporal pRNFL thickness was higher, both in MS and HC (MS: 7.1 µm, 95% CI: 2.7-11.6, p = 0.002; HC: 4.7 µm, 95% CI: -0.3 to 9.7, p = 0.07). No longitudinal differences in rates of GCIPL change were noted between HM and LM vs. NM, either in MS or HC.

CONCLUSION

Cross-sectional differences in average GCIPL and pRNFL thicknesses are commonly seen in people with HM as compared to reference normative values from people with NM and can lead to false attribution of pathology if RE is not taken into account. However, our study suggests that longitudinal changes in average GCIPL thickness in PwMS with myopia are similar in magnitude to PwMS with NM, and therefore are appropriate for monitoring disease-related pathology.

Ocular Optical Coherence Tomography in the Evaluation of Sellar and Parasellar Masses: A Review

Compression of the anterior visual pathways by sellar and parasellar masses can produce irreversible and devastating visual loss. Optical coherence tomography (OCT) is a noninvasive high-resolution ocular imaging modality routinely used in ophthalmology clinics for qualitative and quantitative analysis of optic nerve and retinal structures, including the retinal ganglion cells. By demonstrating structural loss of the retinal ganglion cells whose axons form the optic nerve before decussating in the optic chiasm, OCT imaging of the optic nerve and retina provides an excellent tool for detection and monitoring of compressive optic neuropathies and chiasmopathies due to sellar and parasellar masses. Recent studies have highlighted the role of OCT imaging in the diagnosis, follow-up, and prognostication of the visual outcomes in patients with chiasmal compression. OCT parameters of optic nerve and macular scans such as peripapillary retinal nerve fiber layer thickness and macular ganglion cell thickness are correlated with the degree of visual loss; additionally, OCT can detect clinically significant optic nerve and chiasmal compression before visual field loss is revealed on automated perimetry. Preoperative values of OCT optic nerve and macular parameters represent a prognostic tool for postoperative visual outcome. This review provides a qualitative analysis of the current applications of OCT imaging of the retina and optic nerve in patients with anterior visual pathway compression from sellar and parasellar masses. We also review the role of new technologies such as OCT-angiography, which could improve the prognostic ability of OCT to predict postoperative visual function.

Measurement of retinal nerve fiber layer thickness with a deep learning algorithm in ischemic optic neuropathy and optic neuritis

This work aims at determining the ability of a deep learning (DL) algorithm to measure retinal nerve fiber layer (RNFL) thickness from optical coherence tomography (OCT) scans in anterior ischemic optic neuropathy (NAION) and demyelinating optic neuritis (ON). The training/validation dataset included 750 RNFL OCT B-scans. Performance of our algorithm was evaluated on 194 OCT B-scans from 70 healthy eyes, 82 scans from 28 NAION eyes, and 84 scans of 29 ON eyes. Results were compared to manual segmentation as a ground-truth and to RNFL calculations from the built-in instrument software. The Dice coefficient for the test images was 0.87. The mean average RNFL thickness using our U-Net was not different from the manually segmented best estimate and OCT machine data in control and ON eyes. In NAION eyes, while the mean average RNFL thickness using our U-Net algorithm was not different from the manual segmented value, the OCT machine data were different from the manual segmented values. In NAION eyes, the MAE of the average RNFL thickness was 1.18 ± 0.69 μm and 6.65 ± 5.37 μm in the U-Net algorithm segmentation and the conventional OCT machine data, respectively (P = 0.0001).

Biological Correlations and Confounders for Quantification of Retinal Ganglion Cells by Optical Coherence Tomography Based on Studies of Outbred Mice

Purpose

Despite popularity of optical coherence tomography (OCT) in glaucoma studies, it's unclear how well OCT-derived metrics compare to traditional measures of retinal ganglion cell (RGC) abundance. Here, Diversity Outbred (J:DO) mice are used to directly compare ganglion cell complex (GCC) thickness measured by OCT to metrics of retinal anatomy measured ex vivo with retinal wholemounts and optic nerve histology.

Methods

J:DO mice (n = 48) underwent fundoscopic and OCT examinations, with automated segmentation of GCC thickness. RGC axons were quantified from para-phenylenediamine-stained optic nerve cross-sections and somas from BRN3A-immunolabeled retinal wholemounts, with total inner retinal cellularity assessed by TO-PRO and subsequent hematoxylin staining.

Results

J:DO tissues lacked overt disease. GCC thickness, RGC abundance, and total cell abundance varied broadly across individuals. GCC thickness correlated significantly to RGC somal density (r = 0.58) and axon number (r = 0.44), but not total cell density. Retinal area and nerve cross-sectional area varied widely. No metrics were significantly influenced by sex. In bilateral comparisons, GCC thickness (r = 0.95), axon (r = 0.72), and total cell density (r = 0.47) correlated significantly within individuals.

Conclusions

Amongst outbred mice, OCT-derived measurements of GCC thickness correlate significantly to RGC somal and axon abundance. Factors limiting correlation are likely both biological and methodological, including differences in retinal area that distort sampling-based estimates of RGC abundance.

Translational Relevance

There are significant-but imperfect-correlations between GCC thickness and RGC abundance across genetic contexts in mice, highlighting valid uses and ongoing challenges for meaningful use of OCT-derived metrics.

MERCI: a machine learning approach to identifying hydroxychloroquine retinopathy using mfERG

PURPOSE

Hydroxychloroquine (HCQ) is an anti-inflammatory drug in widespread use for the treatment of systemic auto-immune diseases. Vision loss caused by retinal toxicity is a significant risk associated with long term HCQ therapy. Identifying patients at risk of developing retinal toxicity can help prevent vision loss and improve the quality of life for patients. This paper presents updated reference thresholds and examines the diagnostic accuracy of a machine learning approach for identifying retinal toxicity using the multifocal Electroretinogram (mfERG).

METHODS

A retrospective study of patients referred for mfERG testing to detect HCQ retinopathy. A consecutive series of all patients referred to Kensington Vision and Research Centre between August 2017 and July 2020 were considered eligible. Eyes suspect for other ocular pathology including widespread retinal disease and advanced macular pathology unrelated to HCQ or with poor quality mfERG recordings were excluded. All patients received mfERG testing and Ocular Coherence Tomography (OCT) imaging. Presence of HCQ retinopathy was based on ring ratio analysis using clinical reference thresholds established at KVRC coupled with structural features observed on OCT, the clinical reference standard. A Support Vector Machine (SVM) using selected features of the mfERG was trained. Accuracy, sensitivity and specificity are reported.

RESULTS

1463 eyes of 748 patients were included in the study. SVM model performance was assessed on 293 eyes from 265 patients. 55 eyes from 54 patients were identified as demonstrating HCQ retinopathy based on the clinical reference standard, 50 eyes from 49 patients were identified by the SVM. Our SVM achieves an accuracy of 85.3% with a sensitivity of 90.9% and specificity of 84.0%.

CONCLUSIONS

Machine learning approaches can be applied to mfERG analysis to identify patients at risk of retinopathy caused by HCQ therapy.

The OCT RNFL Probability Map and Artifacts Resembling Glaucomatous Damage

Purpose

The purpose of this study was to improve the diagnostic ability of the optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) probability (p-) map by understanding the frequency and pattern of artifacts seen on the p-maps of healthy control (HC) eyes resembling glaucomatous damage.

Methods

RNFL p-maps were generated from wide-field OCT cube scans of 2 groups of HC eyes, 200 from a commercial normative group (HC-norm) and 54 from a prospective study group, as well as from 62 patient eyes, which included 32 with early glaucoma (EG). These 32 EG eyes had 24-2 mean deviation (MD) better than -6 dB and perimetric glaucoma as defined by 24-2 and 10-2 criteria. For the HC groups, "glaucoma-like" arcuates were defined as any red region near the temporal half of the disc.

Results

Seven percent of the 200 HC-norm and 11% of the 54 HC RNFL p-maps satisfied the definition of "glaucoma-like," as did all the patients' p-maps. The HC p-maps showed two general patterns of abnormal regions, "arcuate" and "temporal quadrant," and these patterns resembled those seen on some of the RNFL p-maps of the EG eyes. A "vertical midline" rule, which required the abnormal region to cross the vertical midline through the fovea, had a specificity of >99%, and a sensitivity of 75% for EG and 93% for moderate to advanced eyes.

Conclusions

Glaucoma-like artifacts on RNFL p-maps are relatively common and can masquerade as arcuate and/or widespread/temporal damage.

Translational Relevance

A vertical midline rule had excellent specificity. However, other OCT information is necessary to obtain high sensitivity, especially in eyes with early glaucoma.

Case Report: Bilateral Cecocentral Visual Field Defect Secondary to Congenital Optic Disc Pit

SIGNIFICANCE

Congenital optic disc pits are known to cause complications, commonly maculopathy due to retinoschisis and/or neurosensory retinal detachment. Retinal nerve fiber layer defects with associated visual field defects without maculopathy are another complication and can result in decreased visual function but have rarely been reported in the literature, especially bilaterally.

PURPOSE

This case report describes a patient with bilateral cecocentral visual field defects due to congenital optic nerve pits without associated maculopathy.

CASE REPORT

A 42-year-old Black man presented with blur symptoms at near uncorrected. Of note, there was no history of substance abuse or nutritional deficiencies. Best-corrected acuities were 20/20 in the right eye and 20/30 in the left eye. Clinical examination revealed bilateral focal grayish depression of the temporal optic nerve cup with associated papillomacular retinal nerve fiber layer defects. Optical coherence tomography (OCT) imaging revealed bilateral focal excavation of the temporal cup, temporal thinning of the retinal nerve fiber layer, and correlated binasal thinning of the ganglion cell complex, in the absence of retinoschisis or neurosensory detachment. Threshold visual field testing revealed stable bilateral cecocentral visual field defects. A diagnosis of bilateral cecocentral visual field defect secondary to congenital optic disc pits was made based on the patient's history and clinical examination.

CONCLUSIONS

A cecocentral visual field defect, unrelated to maculopathy, is a less common complication of congential optic disc pits that can cause decreased visual function. This case report provides evidence of this bilateral ocular condition and reviews the reported clinical, OCT, and threshold visual field manifestations of the disease. Specifically, spectral-domain OCT ganglion cell analysis seems useful in localizing the visual field defect.

Detecting glaucoma with only OCT: Implications for the clinic, research, screening, and AI development

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.

Do biometric parameters improve the quality of optic nerve head measurements with spectral domain optical coherence tomography?

Background

Spectral domain optical coherence tomography (SD-OCT) is a widely applied non-invasive technique for evaluating optic nerve head parameters. The aim of this study was to evaluate the impact of biometric parameters such as the spherical equivalent (SE) and the anterior corneal curvature (ACC) on the peripapillary retinal nerve fiber layer (pRNFL), Bruch’s membrane opening (BMO), and the minimum rim width (MRW) measurements performed by spectral domain optical coherence tomography (SD-OCT) in glaucomatous and healthy eyes.

Methods

In this cross-sectional, case–control prospective pilot study, the glaucoma group consisted of 50 patients with previously diagnosed and treated glaucoma and one healthy group of 50 subjects. Two consecutive examinations of pRNFL, BMO, and MRW with SD-OCT for every patient were performed without ACC and objective refraction (imaging 1) and with them (imaging 2).

Results

The interclass correlation coefficient (ICC) reflected high agreement between imaging 1 and imaging 2 in both groups. The ICC in the glaucoma and healthy groups for pRNFL (0.99 vs. 0.98), BMO (0.95 vs. 0.97), and MRW (1.0 vs. 1.0) was comparable.

Conclusions

Our preliminary data from a small number of eyes showed that the measurements of pRNFL, MRW, and BMO reflected high agreement between both imaging techniques with ACC and objective refraction and without these parameters in subjects with a refractive error up to ± 6.0 diopters. Further studies with participants with higher refractive error are necessary to evaluate the impact of biometric parameters such as SE and ACC on measurements with SD-OCT.

Optical coherence tomography as a useful adjunct in the early detection of meningioma with optic nerve compression

A 48-year-old woman presented with persistent clouding vision in her lower field in the right eye for 5 months. A small retinal hemorrhage was initially reported. Her visual acuity was 20/30 in the right eye and 20/20 in the left, with normal color vision and pupil response. Fundus examination did not reveal any retinal hemorrhage. Although optical coherence tomography (OCT) showed normal macula and retinal nerve fiber layers in both eyes, asymmetric thinning of the ganglion cell inner plexiform layer was found in the superior macula of the right eye in ganglion cell analysis (GCA). Visual field examination revealed a subtle inferonasal scotoma. Compressive optic neuropathy (CON) was suspected. The visual evoked potential test revealed delayed P100 latency. A tuberculum sellae meningioma was found with right medial optic canal extension. The visual acuity of the right eye returned to 20/25 after decompression surgery. OCT can be used to differentiate between retinopathy and optic neuropathy. GCA can help in the early detection of CON and achieve a good visual outcome after surgery.

Structure-function analysis for macular surgery in patients with coexisting glaucoma

PURPOSE

To develop methods to assess the effects of epiretinal membranes (ERM) and macular holes (MH) coexisting with glaucoma on pre-operative retinal structure and function and evaluate post-operative outcomes.

METHODS

Seven eyes of 7 patients with glaucoma, 6 with ERMs and 1 with MH, were enrolled; 4 underwent vitrectomy for ERM and one for MH. Visual fields (VFs) and optical coherence tomography (OCT) scans were obtained pre- and post-operatively. The 10-2VF deviation map was overlayed on ganglion cell and inner plexiform layer (GCL + IPL) and retinal nerve fiber layer (RNFL) deviation maps derived from OCT macula and disc cube scans. Optic nerve circle scans were obtained to assess RNFL thickness, and OCT b-scans associated with VF defects were compared pre- and post-operatively.

RESULTS

Examination of pre-operative VFs and OCT scans showed the importance of determining the extent to which glaucomatous damage contributed to VF loss; verifying automated segmentation of the GCL + IPL and RNFL; and assessing foveal anatomy. Evaluation of post-operative structure-function outcomes required correction of magnification changes in OCT scans and repeated follow-up visits to clarify the origin of VF changes.

CONCLUSIONS

Pre-operative comparisons of VFs and OCT scans may be beneficial in guiding surgical planning, and evaluating outcomes, in eyes with glaucoma undergoing macular surgery.

Feasibility and Repeatability of Handheld Optical Coherence Tomography in Children With Craniosynostosis

Purpose

To determine whether handheld optical coherence tomography (OCT) is feasible and repeatable in children with craniosynostosis.

Methods

This was a prospective cross-sectional study. Children with syndromic and non-syndromic craniosynostosis 0 to 18 years of age were recruited between February 13, 2020, and October 1, 2020. Main outcome measures included feasibility (patient recruitment and handheld OCT success rates) and repeatability, which were assessed using intraclass correlation coefficients (ICCs) where repeated images of the optic nerve head (ONH) within the same visit were available. ONH parameters used for repeatability analysis included cup depth, width, and area; disc width; rim height; retinal thickness; retinal nerve fiber layer thickness; and Bruch's membrane opening minimum rim width.

Results

Fifty children were approached, and all 50 (100%) were successfully recruited. Median age was 51.1 months (range, 1.9-156.9; interquartile range, 37.0-74.2), and 33 of the children (66%) were male. At least one ONH image was obtained in 43 children (86%), and bilateral ONH imaging was successful in 38 children (76%). Factors boosting the likelihood of success included good understanding and cooperation of the child and parent/guardian and availability of an assistant. Repeatability analysis was performed in 20 children, demonstrating good repeatability (ICC range, 0.77-0.99; the majority exceeded 0.90). OCT correctly identified two cases of intracranial hypertension, one of which was undetected by prior fundoscopy.

Conclusions

Handheld OCT is feasible and repeatable in children with syndromic and non-syndromic forms of craniosynostosis.

Translational Relevance

Our handheld OCT approach could be used for the clinical surveillance of children with craniosynostosis.

Ageing and glaucoma progression of the retinal nerve fibre layer using spectral-domain optical coherence tomography analysis

PURPOSE

To compare the effects of ageing and glaucoma progression on the thickness of the circumpapillary retinal nerve fibre layer (cpRNFL) and to evaluate the performance of a set of optical coherence tomography (OCT) progression analyses.

METHODS

The cpRNFL was measured twice by OCT at each of two visits made 10 years apart in 69 healthy individuals and 49 glaucoma patients. Both visits also included Humphrey 24-2 SITA standard testing. The change in cpRNFL thickness was analysed by linear regression, and a sub-analysis was performed on glaucoma patients with a perimetric mean deviation better than -10 dB at the first visit. The proportion of individuals whose OCT progression analyses indicated progression was also evaluated for the same groups.

RESULTS

The average cpRNFL thickness deteriorated by a mean of -0.16 μm/year in the healthy cohort, increased by 0.03 μm/year in the glaucoma cohort, and deteriorated by -0.24 μm/year in eyes with less severe glaucoma; there were no statistically significant differences between the groups. For 17 (30%) of 56 healthy individuals, at least one of the three different OCT progression analyses incorrectly indicated progression.

CONCLUSIONS

No significant differences in change of cpRNFL thickness between visits were found when comparing healthy subjects with glaucoma patients. Also, further cpRNFL thinning was not observed in glaucomatous eyes in which at least one-third of the visual field had been lost. The OCT progression analyses generated a relatively high proportion of false positives. Using OCT for glaucoma follow-up may not be entirely straightforward.

Artifacts in Optical Coherence Tomography Angiography

We performed a comprehensive search of the published literature in PubMed and Google Scholar to identify types, prevalence, etiology, clinical impact, and current methods for correction of various artifacts in optical coherence tomography angiography (OCTA) images. We found that the prevalence of OCTA image artifacts is fairly high. Artifacts associated with eye motion, misidentification of retinal layers, projections, and low optical coherence tomography signal are the most prevalent types. Artifacts in OCTA images are the major limitations of this diagnostic modality in clinical practice and identification of these artifacts and measures to mitigate them are essential for correct diagnosis and follow-up of patients.

Artificial Intelligence (AI) and Retinal Optical Coherence Tomography (OCT)

Ophthalmology has been at the forefront of medical specialties adopting artificial intelligence. This is primarily due to the "image-centric" nature of the field. Thanks to the abundance of patients' OCT scans, analysis of OCT imaging has greatly benefited from artificial intelligence to expand patient screening and facilitate clinical decision-making.In this review, we define the concepts of artificial intelligence, machine learning, and deep learning and how different artificial intelligence algorithms have been applied in OCT image analysis for disease screening, diagnosis, management, and prognosis.Finally, we address some of the challenges and limitations that might affect the incorporation of artificial intelligence in ophthalmology. These limitations mainly revolve around the quality and accuracy of datasets used in the algorithms and their generalizability, false negatives, and the cultural challenges around the adoption of the technology.

Optical Coherence Tomography Neuro-Toolbox for the Diagnosis and Management of Papilledema, Optic Disc Edema, and Pseudopapilledema

BACKGROUND

Distinguishing optic disc edema from pseudopapilledema is a common, sometimes challenging clinical problem. Advances in spectral-domain optical coherence tomography (SD-OCT) of the optic nerve head (ONH) has proven to be a cost effective, noninvasive, outpatient procedure that may help. At its core are tools that quantify the thickness of the retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GC-IPL). The SD-OCT also provides a set of tools that may be qualitatively interpreted in the same way that we read an MRI. They include the transverse axial, en face, and circular tomogram. Our goal is to describe a practical office-based set of tools using SD-OCT in the diagnosis and monitoring of papilledema, optic disc edema, and pseudopapilledema.

EVIDENCE ACQUISITION

Searches on PubMed were performed using combinations of the following key words: OCT, papilledema, pseudopapilledema, optic disc drusen, retinal folds (RF), and choroidal folds (CF).

RESULTS

The principal elements of SD-OCT analysis of the ONH are the RNFL and GC-IPL thickness; however, these metrics have limitations when swelling is severe. Qualitative interpretation of the transverse axial SD-OCT aids in assessing peripapillary shape that may help distinguish papilledema from pseudopapilledema, evaluate atypical optic neuropathies, diagnose shunt failures, and identify outer RF and CF. There is a consensus that the SD-OCT is the most sensitive way of identifying buried optic disc drusen. En face SD-OCT is especially effective at detecting peripapillary wrinkles and outer retinal creases, both of which are common and distinctive signs of optic disc edema that rule out pseudopapilledema. Mechanically stressing the ONH in the adducted eye position, in patients with papilledema, may expose folds and peripapillary deformations that may not be evident in primary position. We also discuss how to optimize the acquisition and registration of SD-OCT images.

CONCLUSIONS

The SD-OCT is not a substitute for a complete history and a careful examination. It is, however, a convenient ancillary test that aids in the diagnosis and management of papilledema, optic disc edema, and pseudopapilledema. It is particularly helpful in monitoring changes over the course of time and distinguishing low-grade papilledema from buried drusen. The application of the SD-OCT toolbox depends on optimizing the acquisition of images, understanding its limitations, recognizing common artifacts, and accurately interpreting images in the context of both history and clinical findings.

Retinal Ganglion Cells-Diversity of Cell Types and Clinical Relevance

Retinal ganglion cells (RGCs) are the bridging neurons that connect the retinal input to the visual processing centres within the central nervous system. There is a remarkable diversity of RGCs and the various subtypes have unique morphological features, distinct functions, and characteristic pathways linking the inner retina to the relevant brain areas. A number of psychophysical and electrophysiological tests have been refined to investigate this large and varied population of RGCs. Technological advances, such as high-resolution optical coherence tomography imaging, have provided additional tools to define the pattern of RGC involvement and the chronological sequence of events in both inherited and acquired optic neuropathies. The mechanistic insights gained from these studies, in particular the selective vulnerability and relative resilience of particular RGC subtypes, are of fundamental importance as they are directly relevant to the development of targeted therapies for these invariably progressive blinding diseases. This review provides a comprehensive description of the various types of RGCs, the developments in proposed methods of classification, and the current gaps in our knowledge of how these RGCs are differentially affected depending on the underlying aetiology. The synthesis of the current body of knowledge on the diversity of RGCs and the pathways that are potentially amenable to therapeutic modulation will hopefully lead to much needed effective treatments for patients with optic neuropathies.

Performance evaluation of two fundus oculi angiographic imaging system: Optos 200Tx and Heidelberg Spectralis

The present study aimed to compare the imaging performance of two ultra-wide-field fluorescein angiography imaging systems, namely the OptosOptomap 200Tx (Optos 200Tx) and the Heidelberg Spectralis (Spectralis). A total of 18 patients (36 eyes) underwent angiography using the two systems at the Department of Ophthalmology, Beijing Friendship Hospital (Beijing, China) between January and June 2017. The images were obtained as a single shot centered on the macula. The total area and area within each of four visualized quadrants were calculated and compared. The averages of the total and individual quadrant area captured by the Optos 200Tx were all larger than those obtained with the Spectralis (P<0.05). For pair-wise comparison, the circular area centered on the macula (radius of 10 and 15 mm) was displayed: Optos 200Tx 10 mm (295.57 mm²) < Spectralis (520.11 mm²) < Optos 200Tx 15 mm (596.45 mm²) < Optos 200Tx (804.36 mm²) (P<0.01). The differences of each of the four quadrant areas were statistically significant between the two systems (P<0.05). The mean size of the areas was in the following order: Inferior < temporal < superior < nasal for the Optos 200Tx, and inferior < temporal < nasal < superior for the Spectralis. Further comparison of the four-quadrant area indicated that the inferior quadrant of the Optos 200Tx was smaller than the other three quadrants (P<0.01) and the inferior quadrant of the Spectralis was smaller than the superior quadrant (P<0.01). The total retinal area and the retinal area of each quadrant captured by the Optos 200Tx were larger than those captured with the Spectralis. The total retinal area captured with the Optos 200Tx was able to cover the mid-peripheral area and part of the far-peripheral area of the retina, whereas the Spectralis only covered the mid-peripheral area.

Effect of Foveal Location on Retinal Nerve Fiber Layer Thickness Profile in Superior Oblique Palsy Eyes

PRéCIS:: Superior oblique palsy (SOP) eyes show thinner inferotemporal retinal nerve fiber layer (RNFL) without adjusting for foveal position. There was a strong correlation between the degree of torsion and the difference in the RNFL thickness before and after adjusting foveal location.

PURPOSE

The impact of foveal position on RNFL thickness has been shown. In this study, we evaluate RNFL thickness profiles according to the disc-foveal angle in SOP and control eyes.

MATERIALS AND METHODS

In 44 eyes of 22 patients with unilateral congenital SOP and 42 eyes of 42 normal controls, the position of the fovea relative to the optic disc was calculated by optical coherence tomography using FoDi (fovea-to-disc) technology. After measuring RNFL thickness with FoDi alignment technology, each optical coherence tomography image was reevaluated with FoDi turned off, and the measurements were repeated to determine RNFL values according to the disc-foveal angle.

RESULTS

The average disc-foveal angle was -10.85±6.60 degrees and -10.71±6.63 degrees in the affected and fellow eyes of SOP patients; these values were significantly greater than control subjects (-5.88±4.09 degrees). There was no significant difference in RNFL sector values between SOP and control eyes with FoDi. From all RNFL sectors, the measured inferotemporal thickness was less in SOP eyes without FoDi than in SOP eyes with FoDi (129.7±20.5 µm vs. 144.6±17.8 µm, respectively, P=0.001). Differences of the RNFL thicknesses with and without FoDi in SOP eyes in the superotemporal and inferotemporal sectors were 5.40±13.42 and 14.84±15.00, respectively, which were significantly more than the same changes in control eyes with amount of 0.30±6.57 and 8.52±10.4 (P=0.02 for both sectors).

CONCLUSIONS

In SOP eyes with large amounts of torsion, a correction for the disc-foveal angle is necessary for accurate determination of the RNFL thickness profile.

Optical Coherence Tomography Segmentation Errors of the Retinal Nerve Fiber Layer Persist Over Time

PRéCIS:: There are errors in automated segmentation of the retinal nerve fiber layer (RNFL) in glaucoma suspects or patients with mild glaucoma that appear to persist over time; however, automated segmentation has greater repeatability than manual segmentation.

PURPOSE

To identify whether optical coherence tomography (OCT) segmentation errors in RNFL thickness measurements persist longitudinally.

METHODS

This was a cohort study. We used spectral domain OCT (Spectralis) to measure RNFL thickness in a 6-degree peripapillary circle, and exported the native "automated segmentation only" results. In addition, we exported RNFL thickness results after "manual refinement" to correct errors in the automated segmentation, and used the differences in these measurements as "error" in segmentation. We used Bland-Altman plots and linear regression to determine the magnitude, location, and repeatability of RNFL thickness error in all twelve 30-degree sectors and compared the error at baseline to follow-up time points at 6 months, 2 years, 3 years, and 4 years.

RESULTS

We included 406 eyes from 213 participants. The 95% confidence interval for errors at baseline was -6.5 to +13.2 μm. The correlation between the baseline error and the errors in the follow-up time periods were high (r>0.5, P<0.001 for all). Automated segmentation had a smaller SD of residuals from the longitudinal trend line when compared to manual refinement (1.56 vs. 1.80 μm, P<0.001), and a higher ability (P=0.009) to monitor progression using an analysis of a longitudinal signal-to-noise ratio.

CONCLUSIONS

Errors in automated segmentation remain relatively stable, and baseline error is highly likely to persist in the same direction and magnitude in subsequent time periods. However, automated segmentation (without manual refinement) is more repeatable and may be more sensitive to glaucomatous progression. Future segmentation algorithms could exploit these findings to improve automated segmentation in the future.

Artifact Rates for 2D Retinal Nerve Fiber Layer Thickness Versus 3D Retinal Nerve Fiber Layer Volume

Purpose

To compare artifact rates in two-dimensional (2D) versus three-dimensional (3D) retinal nerve fiber layer (RNFL) scans using Spectralis optical coherence tomography (OCT)

Methods

Thirteen artifact types in 2D and 3D RNFL scans were identified in 106 glaucomatous eyes and 95 normal eyes. Artifact rates were calculated per B-scan and per eye. In 3D volume scans, artifacts were counted only for the 97 B-scans used to calculate RNFL parameters for the 2.5–3.5-mm annulus. 3D RNFL measurements were calculated twice, once before and again after deletion of B-scans with artifacts and subsequent automated interpolation.

Results

For 2D scans, artifacts were present in 58.5% of B-scans (62 of 106) in glaucomatous eyes. For 3D scans, a mean of 35.4% of B-scans (34.3 of 97 B-scans per volume scan) contained an artifact in 106 glaucomatous eyes. For 3D data of glaucoma patients, mean global RNFL thickness values were similar before and after interpolation (77.0 ± 11.6 µm vs. 75.1 ± 11.2 µm, respectively; P = 0.23). Fewer clinically significant artifacts were noted in 3D RNFL scans, where only 7.5% of glaucomatous eyes (8 of 106) and 0% of normal eyes (0 of 95) had artifacts, compared to 2D RNFL scans, where 58.5% of glaucomatous eyes (62 of 106) and 14.7% of normal eyes (14 of 95) had artifacts.

Conclusions

Compared to 2D RNFL scans, 3D RNFL volume scans less often require manual correction to obtain accurate measurements.

Translational Relevance

3D RNFL volume scans have fewer clinically significant artifacts compared to 2D RNFL thickness scans.

Use of Contact Lenses to Optimize OCT Scans of the Optic Nerve in Glaucoma Suspects or Patients with Glaucoma with High Myopia

PURPOSE

Patients with myopia are at increased risk for the development of glaucoma. The inability to correct for axial length on spectral-domain (SD) OCT translates into lower signal strength and scan reliability in patients with high axial myopia. We evaluated the effectiveness of a contact lens to increase the signal strength and to assess optic nerve dimensions and nerve fiber layer (NFL) thickness using SD OCT in patients with glaucoma or who are glaucoma suspects with high axial myopia.

DESIGN

Single-center, prospective, interventional study.

PARTICIPANTS

Patients with axial lengths of more than 25.5 mm with a diagnosis of glaucoma or glaucoma suspect.

METHODS

The optic nerve cube 200×200 scan using the Cirrus SD OCT 400 (Carl Zeiss Meditec, Inc., Dublin, CA) was carried out first without the use of a contact lens and then repeated with placement of the contact lens to correct for the spherical equivalent of the refractive error.

MAIN OUTCOME MEASURES

The primary outcome measure was the change in the average NFL thickness before and after use of the contact lens. Secondary outcome measures included the changes in cup volume, disc area, and rim area on OCT.

RESULTS

Twelve patients were recruited (20 eyes); the average axial length was 27.06 mm, and the average signal strength interval increased by 1.73 (P = 0.001). With the use of a contact lens, the average NFL thickness was significantly thicker. None of the changes in the secondary outcome measures were significant: rim area, cup volume, or disc area.

CONCLUSIONS

Based on our data, the use of a contact lens statistically improved the signal strength and average NFL thickness of the SD OCT scan. The ability to capture the perimeter of the optic disc accurately can be limited in the setting of peripapillary atrophy, which was present in all but 2 participants. Future studies with a larger number of participants and a wider range of axial myopia to discern if contact lens correction has a greater effect on the highest axial lengths are needed.

Separation and thickness measurements of superficial and deep slabs of the retinal nerve fiber layer in healthy and glaucomatous eyes

PURPOSE

Describe a new method to analyze retinal nerve fiber layer (RNFL) thickness maps.

DESIGN

Cross-sectional study.

SUBJECTS

RNFL thickness maps of healthy and glaucomatous eyes.

METHODS

Optical coherence tomography (OCT) RNFL raster scans from 98 healthy and 50 glaucomatous eyes were analyzed. The RNFL thickness maps were separated into superficial (SNFL) and deep (DNFL) slabs through a partial thickness plane set at the modal thickness (mode). Association between mode and OCT signal strength (SS), age, axial length, and visual field mean deviation (VFMD) was tested (Pearson coefficient, r). Thicknesses of inferior and superior SNFL regions (i-,s-SNFL), and inferior, superior, nasal, and temporal DNFL regions (i-,s-,n-,t-DNFL) were calculated. The regions thicknesses were compared between healthy and glaucomatous eyes (t-test) and between glaucomatous eyes with early, moderate, and severe disease (ANOVA and linear regressions of thickness on VFMD). Diagnostic accuracy and correlation with VFMD of RNFL regions thicknesses were calculated as the area under the receiver operating characteristic curve (AUC) and Pearson r, respectively. P<0.05 was considered significant.

MAIN OUTCOME

Thickness of regions in SNFL and DNFL slabs.

RESULTS

The mode was not associated with SS, age, axial length, or VFMD, it circumscribed the thicker RNFL around the optic disc of healthy and glaucomatous eyes, and it was used to separate the SNFL and DNFL slabs of RNFL thickness maps. The thickness of the SNFL slab was less in glaucomatous eyes than in healthy eyes (P<0.001). S-SNFL and i-SNFL thicknesses (respectively) were 86.0±8.2μm and 87.3±9.6μm in healthy eyes vs. 66.1±9.1μm and 63.4±8.2μm in glaucomatous eyes (P<0.001 for both). The thickness of the DNFL slab was similar between groups (P=0.19). T-DNFL thickness was 37.0±5.3μm in healthy eyes vs. 33.9±5.0μm in glaucomatous eyes (P<0.001); thicknesses of all other DNFL regions were similar. The SNFL regions only thinned with progressively worse glaucoma severity, had excellent AUCs (AUC≥0.95, P<0.001), and correlated strongly with VFMD (r≥0.60, P<0.001).

CONCLUSIONS

Glaucomatous RNFL thinning is predominantly detected within a slab with thickness greater than the mode. SNFL thickness has great AUC and correlation with VFMD in glaucomatous eyes. The usefulness for diagnosis and monitoring of glaucoma needs further study.

Optical coherence tomography is highly sensitive in detecting prior optic neuritis

OBJECTIVE

To explore sensitivity of optical coherence tomography (OCT) in detecting prior unilateral optic neuritis.

METHODS

This is a retrospective, observational clinical study of all patients who presented from January 1, 2014, to January 6, 2017, with unilateral optic neuritis and OCT available at least 3 months after the attack. We compared OCT retinal nerve fiber layer (RNFL) and ganglion cell inner plexiform layer (GCIPL) thicknesses between affected and unaffected contralateral eyes. We excluded patients with concomitant glaucoma or other optic neuropathies. Based on analysis of normal controls, thinning was considered significant if RNFL was at least 9 µm or GCIPL was at least 6 µm less in the affected eye compared to the unaffected eye.

RESULTS

Fifty-one patients (18 male and 33 female) were included in the study. RNFL and GCIPL thicknesses were significantly lower in eyes with optic neuritis compared to unaffected eyes (p < 0.001). RNFL was thinner by ≥9 µm in 73% of optic neuritis eyes compared to the unaffected eye. GCIPL was thinner by ≥6 µm in 96% of optic neuritis eyes, which was more sensitive than using RNFL (p < 0.001). When using a threshold ≤1st percentile of age-matched controls, sensitivities were 37% for RNFL and 76% for GCIPL, each of which was lower than those calculated using the intereye difference as the threshold (p < 0.01).

CONCLUSIONS

OCT, especially with GCIPL analysis, is a highly sensitive modality in detecting prior optic neuritis, which is made more robust by using intereye differences to approximate change.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that OCT accurately identifies patients with prior unilateral optic neuritis.