Developing a Continuous Severity Scale for Macular Telangiectasia Type 2 Using Deep Learning and Implications for Disease Grading

PURPOSE

Deep learning (DL) models have achieved state-of-the-art medical diagnosis classification accuracy. Current models are limited by discrete diagnosis labels, but could yield more information with diagnosis in a continuous scale. We developed a novel continuous severity scaling system for macular telangiectasia (MacTel) type 2 by combining a DL classification model with uniform manifold approximation and projection (UMAP).

DESIGN

We used a DL network to learn a feature representation of MacTel severity from discrete severity labels and applied UMAP to embed this feature representation into 2 dimensions, thereby creating a continuous MacTel severity scale.

PARTICIPANTS

A total of 2003 OCT volumes were analyzed from 1089 MacTel Project participants.

METHODS

We trained a multiview DL classifier using multiple B-scans from OCT volumes to learn a previously published discrete 7-step MacTel severity scale. The classifiers' last feature layer was extracted as input for UMAP, which embedded these features into a continuous 2-dimensional manifold. The DL classifier was assessed in terms of test accuracy. Rank correlation for the continuous UMAP scale against the previously published scale was calculated. Additionally, the UMAP scale was assessed in the κ agreement against 5 clinical experts on 100 pairs of patient volumes. For each pair of patient volumes, clinical experts were asked to select the volume with more severe MacTel disease and to compare them against the UMAP scale.

MAIN OUTCOME MEASURES

Classification accuracy for the DL classifier and κ agreement versus clinical experts for UMAP.

RESULTS

The multiview DL classifier achieved top 1 accuracy of 63.3% (186/294) on held-out test OCT volumes. The UMAP metric showed a clear continuous gradation of MacTel severity with a Spearman rank correlation of 0.84 with the previously published scale. Furthermore, the continuous UMAP metric achieved κ agreements of 0.56 to 0.63 with 5 clinical experts, which was comparable with interobserver κ values.

CONCLUSIONS

Our UMAP embedding generated a continuous MacTel severity scale, without requiring continuous training labels. This technique can be applied to other diseases and may lead to more accurate diagnosis, improved understanding of disease progression, and key imaging features for pathologic characteristics.

FINANCIAL DISCLOSURE(S)

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

A Novel Role for Corneal Pachymetry in Planning Cataract Surgery by Determining Changes in Spherical Equivalent Resulting from a Previous LASIK Treatment

Objectives

To provide a metric to differentiate between hyperopic and myopic ablation of a prior LASIK treatment based on the corneal pachymetry profile after laser vision correction (LVC).

Methods

Pachymetry data were retrospectively recovered from patients who had previous LASIK for refractive purposes between 2019 and 2020. Patients with any corneal disorder were excluded. Ablation spherical equivalent was predicted from the central to semiperipheral corneal thickness (CPT) ratio, both values were provided by using the Pentacam user interface software (UI), and values were computed from extracted raw pachymetry data.

Results

Data of 157 eyes of 81 patients were collected, of which data were analysed for 73 eyes of 73 patients to avoid concurrence of measurements in both eyes per subject (42% female; mean age 40.9; SD 12.8). The CPT ratio cutoff for distinction between myopic and hyperopic LASIK was 0.86 for Pentacam UI data. Sensitivity and specificity were 0.7 and 0.95, respectively. Accuracy increased with computation of the CPT ratio based on extracted raw data with sensitivity and specificity of 0.87 and 0.99, respectively. There was a marked linear correlation between the CPT ratio and the ablation spherical equivalent (R² = 0.93).

Conclusions

CPT ratio cutoffs can correctly classify if a cornea previously had a hyperopic versus myopic LASIK surgery and estimate the ablation spherical equivalent of such treatment. This could prove useful for increased accuracy of intraocular lens (IOL) calculations for patients with no historical data of their prior LVC surgery at the time of cataract surgery planning.

Description of a patient cohort with Hereditary Sensory Neuropathy Type 1 without retinal disease Macular Telangiectasia type 2 - implications for retinal screening in HSN1

BACKGROUND AND AIMS

Pathogenic variants in the genes encoding serine palmitoyl transferase (SPTLC1 or SPTLC2) are the most common causes of the rare peripheral nerve disorder Hereditary Sensory Neuropathy Type 1 (HSN1). Macular telangiectasia type 2 (MacTel), a retinal disorder associated with disordered serine-glycine metabolism and has been described in some patients with HSN1. This study aims to further investigate this association in a cohort of people with HSN1.

METHODS

Fourteen patients with a clinically and genetically confirmed diagnosis of HSN1 from the National Hospital for Neurology and Neurosurgery (NHNN, University College London Hospitals NHS Foundation Trust, London, United Kingdom) were recruited to the MacTel Registry, between July 2018 and April 2019. Two additional patients were identified from the dataset of the international clinical registry study (www.lmri.net). Ocular examination included fundus autofluorescence, blue light and infrared reflectance, macular pigment optical density mapping, and optical coherence tomography.

RESULTS

Twelve patients had a pathogenic variant in the SPTLC1 gene, with p.Cys133Trp in eleven cases (92%) and p.Cys133Tyr in one case (8%). Four patients had a variant in the SPTLC2 gene. None of the patients showed clinical evidence of MacTel.

INTERPRETATION

The link between HSN1 and MacTel seems more complex than can solely be explained by the genetic variants. An extension of the spectrum of SPTLC1/2-related disease with phenotypic pleiotropy is proposed. HSN1 patients should be screened for visual symptoms and referred for specialist retinal screening, but the association of the two diseases is likely to be variable and remains unexplained. This article is protected by copyright. All rights reserved.

Effect of ethnicity and other sociodemographic factors on attendance at diabetic eye screening: a 12-month retrospective cohort study

OBJECTIVES

To examine the association of sociodemographic characteristics with attendance at diabetic eye screening in a large ethnically diverse urban population.

DESIGN

Retrospective cohort study.

SETTING

Screening visits in the North East London Diabetic Eye Screening Programme (NELDESP).

PARTICIPANTS

84 449 people with diabetes aged 12 years or older registered in the NELDESP and scheduled for screening between 1 April 2017 and 31 March 2018.

MAIN OUTCOME MEASURE

Attendance at diabetic eye screening appointments.

RESULTS

The mean age of people with diabetes was 60 years (SD 14.2 years), 53.4% were men, 41% South Asian, 29% White British and 17% Black; 83.4% attended screening. Black people with diabetes had similar levels of attendance compared with White British people. However, South Asian, Chinese and 'Any other Asian' background ethnicities showed greater odds of attendance compared with White British. When compared with their respective reference group, high levels of deprivation, younger age, longer duration of diabetes and worse visual acuity, were all associated with non-attendance. There was a higher likelihood of attendance per quintile improvement in deprivation (OR, 1.06; 95% CI, 1.03 to 1.08), with increasing age (OR per decade, 1.17; 95% CI, 1.15 to 1.19), with better visual acuity (OR per Bailey-Lovie chart line 1.12; 95% CI, 1.11 to 1.14) and with longer time of NELDESP registration (OR per year, 1.02; 95% CI, 1.01 to 1.03).

CONCLUSION

Ethnic differences in diabetic eye screening uptake, though small, are evident. Despite preconceptions, a higher likelihood of screening attendance was observed among Asian ethnic groups when compared with the White ethnic group. Poorer socioeconomic profile was associated with higher likelihood of non-attendance for screening. Further work is needed to understand how to target individuals at risk of non-attendance and reduce inequalities.

Fundus Autofluorescence Imaging in Macular Telangiectasia Type 2: MacTel Study Report Number 9

PURPOSE

To investigate the role of fundus autofluorescence (FAF) imaging in the diagnosis of macular telangiectasia type 2 (MacTel) and to describe disease-associated FAF patterns and their origin.

DESIGN

Cross-sectional multicenter study METHODS: FAF images were collected from the multicenter MacTel Natural History Observation and Registry Study. In a first qualitative approach, common FAF phenotypes were defined and correlated with multimodal imaging. We then evaluated how many eyes showed FAF changes, and temporal vs nasal asymmetry of FAF changes was graded. Finally, 100 eyes of MacTel patients and 100 control eyes (50 normal eyes and 50 eyes with other macular diseases) were combined and 2 masked graders assessed the presence of MacTel based on FAF images alone.

RESULTS

The study included 807 eyes of 420 patients (33 eyes were excluded owing to poor image quality). Loss of macular pigment, cystoid spaces, pigment plaques, neovascular membranes, and ectatic vascular changes commonly caused characteristic changes on FAF images. All MacTel patients had macular FAF changes in at least 1 eye. In 95% of eyes, these changes were more pronounced temporally than nasally. Common FAF patterns were increased (60%) and mixed/decreased FAF (38%) and/or visibility of vascular changes such as blunted vessels or ectatic capillaries (79%). Based on those features, high diagnostic performance was achieved for detection of the disease based on FAF alone (Youden index up to 0.91).

CONCLUSIONS

The study demonstrates that MacTel is consistently associated with disease-specific changes on FAF imaging. Those changes are typically more pronounced in the temporal parafovea.

Author Correction: Identification of genetic factors influencing metabolic dysregulation and retinal support for MacTel, a retinal disorder

A Correction to this paper has been published: https://doi.org/10.1038/s42003-021-01972-y

Contextualizing single-arm trials with real-world data: An emulated target trial comparing therapies for neovascular age-related macular degeneration

Abstract

One‐in‐four ophthalmology trials are single‐armed, which poses challenges to their interpretation. We demonstrate how real‐world cohorts used as external/synthetic control arms can contextualize such trials. We herein emulated a target trial on the intention‐to‐treat efficacy of off‐label bevacizumab (q6w) pro re nata relative to fixed‐interval aflibercept (q8w) for improving week 54 visual acuity of eyes affected by neovascular age‐related macular degeneration. The bevacizumab arm (n = 65) was taken from the ABC randomized controlled trial. A total of 4,471 aflibercept‐treated eyes aligning with the ABC trial eligibility were identified from electronic health records and synthetic control arms were created by emulating randomization conditional on age, sex, and baseline visual read via exact matching and propensity score methods. We undertook an inferiority analysis on mean difference at 54 weeks; outcomes regression on achieving a change in visual acuity of greater than or equal to 15, greater than or equal to 10, and less than or equal to −15 Early Treatment Diabetic Retinopathy (ETDRS) letters at week 54; and a time‐to‐event analysis on achieving a change in visual acuity of greater than or equal to 15, greater than or equal to 10, and less than or equal to −15 ETDRS letters by week 54. The findings suggest off‐label bevacizumab to be neither inferior nor superior to licensed aflibercept. Our study highlights how real‐world cohorts representing the counterfactual intervention could aid the interpretation of single‐armed trials when analyzed in accord to the target trial framework.

Identification of genetic factors influencing metabolic dysregulation and retinal support for MacTel, a retinal disorder

Macular Telangiectasia Type 2 (MacTel) is a rare degenerative retinal disease with complex genetic architecture. We performed a genome-wide association study on 1,067 MacTel patients and 3,799 controls, which identified eight novel genome-wide significant loci (p < 5 × 10^-8), and confirmed all three previously reported loci. Using MAGMA, eQTL and transcriptome-wide association analysis, we prioritised 48 genes implicated in serine-glycine biosynthesis, metabolite transport, and retinal vasculature and thickness. Mendelian randomization indicated a likely causative role of serine (FDR = 3.9 × 10^-47) and glycine depletion (FDR = 0.006) as well as alanine abundance (FDR = 0.009). Polygenic risk scoring achieved an accuracy of 0.74 and was associated in UKBiobank with retinal damage (p = 0.009). This represents the largest genetic study on MacTel to date and further highlights genetically-induced systemic and tissue-specific metabolic dysregulation in MacTel patients, which impinges on retinal health.

Effect of Face-Down Positioning vs Support-the-Break Positioning After Macula-Involving Retinal Detachment Repair: The PostRD Randomized Clinical Trial

Importance

A lack of consensus exists with regard to the optimal positioning regimen for patients after macula-involving retinal detachment (RD) repair.

Objective

To evaluate the effect of face-down positioning vs support-the-break positioning on retinal displacement and distortion after macula-involving RD repair.

Design, Setting, and Participants

A prospective 6-month single-masked randomized clinical trial was conducted at a multicenter tertiary referral setting from May 16, 2016, to May 1, 2018. Inclusion criteria were fovea-involving rhegmatogenous RD; central visual loss within 14 days; patients undergoing primary vitrectomy and gas surgery, under local anesthetic; patients able to give written informed consent; and 18 years old and older. Analysis was conducted following a modified intention-to-treat principle, with patients experiencing a redetachment or failure to attach the macula being excluded from analysis.

Interventions

Participants were randomized 1:1 to receive face-down positioning or support-the-break positioning for a 24-hour period postoperatively. Positioning compliance was not monitored.

Main Outcomes and Measures

The proportion of patients with retinal displacement on autofluorescence imaging at 6 months postoperatively. Secondary outcomes included proportion of patients with displacement at 2 months; amplitude of displacement at 2 and 6 months; corrected Early Treatment Diabetic Retinopathy Study visual acuity; objective Distortion Scores; and quality of life questionnaire scores at 6 months.

Results

Of the 262 randomized patients, 239 were analyzed (171 male [71.5%]; mean [SD] age, 60.8 [9.8] years). At 6 months, retinal displacement was detected in 42 of 100 (42%) in the face-down positioning group vs 58 of 103 (56%) in the support-the-break positioning group (odds ratio, 1.77; 95%CI, 1.01-3.11; P = .04). The degree of displacement was lower in the face-down group. Groups were similar in corrected visual acuity (face-down, 74 letters vs support-the-break, 75 letters), objective D Chart Distortion Scores (range: 0, no distortion to 41.6, severe distortion; with face-down at 4.5 vs support-the-break at 4.2), and quality of life scores (face-down 89.3 vs support-the-break 89.0) at 2 and 6 months. Retinal redetachment rate was similar in both groups (face-down group, 12.2% and support-the-break group, 13.7%). Retinal folds were less common in the face-down positioning group vs the support-the-break positioning group (5.3% vs 13.5%, respectively; odds ratio, 2.8; 95% CI, 1.2-7.4; P = .03). Binocular diplopia was more common in the support-the-break group compared with the face-down positioning group (7.6% vs 1.5%, respectively; odds ratio, 5.3; 95% CI, 1.3-24.6; P = .03). Amplitude of displacement was associated with worse visual acuity (r = -0.5; P < .001) and distortion (r = 0.28; P = .008).

Conclusions and Relevance

In this study, findings suggest that face-down positioning was associated with a reduction in the rate and amplitude of postoperative retinal displacement after macula-involving RD repair and with a reduction in binocular diplopia. No association was found with visual acuity or postoperative distortion.

Trial Registration

ClinicalTrials.gov Identifier: NCT02748538.

[Artificial intelligence in ophthalmology : Guidelines for physicians for the critical evaluation of studies]

BACKGROUND

Empirical models have been an integral part of everyday clinical practice in ophthalmology since the introduction of the Sanders-Retzlaff-Kraff (SRK) formula. Recent developments in the field of statistical learning (artificial intelligence, AI) now enable an empirical approach to a wide range of ophthalmological questions with an unprecedented precision.

OBJECTIVE

Which criteria must be considered for the evaluation of AI-related studies in ophthalmology?

MATERIAL AND METHODS

Exemplary prediction of visual acuity (continuous outcome) and classification of healthy and diseased eyes (discrete outcome) using retrospectively compiled optical coherence tomography data (50 eyes of 50 patients, 50 healthy eyes of 50 subjects). The data were analyzed with nested cross-validation (for learning algorithm selection and hyperparameter optimization).

RESULTS

Based on nested cross-validation for training, visual acuity could be predicted in the separate test data-set with a mean absolute error (MAE, 95% confidence interval, CI of 0.142 LogMAR [0.077; 0.207]). Healthy versus diseased eyes could be classified in the test data-set with an agreement of 0.92 (Cohen's kappa). The exemplary incorrect learning algorithm and variable selection resulted in an MAE for visual acuity prediction of 0.229 LogMAR [0.150; 0.309] for the test data-set. The drastic overfitting became obvious on comparison of the MAE with the null model MAE (0.235 LogMAR [0.148; 0.322]).

CONCLUSION

Selection of an unsuitable measure of the goodness-of-fit, inadequate validation, or withholding of a null or reference model can obscure the actual goodness-of-fit of AI models. The illustrated pitfalls can help clinicians to identify such shortcomings.

WITHDRAWN: Hyper-reflectivity on optical coherence tomography in macular telangiectasia type 2

Ahead of Print article withdrawn by publisher.

Longitudinal Assessment of Remnant Foveal Cone Structure in a Case Series of Early Macular Telangiectasia Type 2

Purpose

To determine the extent of remnant cone structure within early foveal ellipsoid zone (EZ) lesions in macular telangiectasia type 2 longitudinally using both confocal and split detector adaptive optics scanning light ophthalmoscopy (AOSLO).

Methods

Spectral domain optical coherence tomography (SDOCT), confocal and split detector AOSLO were acquired from seven patients (10 eyes) with small (early) EZ lesions on SDOCT secondary to macular telangiectasia type 2 at baseline, 6 months, and 12 months. The presence of cone structure on AOSLO in areas of EZ loss as well as cones at 1° eccentricity, and their change over time were quantified.

Results

By split detector AOSLO, remnant cone structure was identified within and on the borders of all foveal EZ lesions. Within the extent of these lesions, cone spacing ranged from 4.97 to 9.95 µm at baseline, 5.30 to 6.10 µm at 6 months, and 4.99 to 7.12 µm at 12 months. Four eyes with significantly smaller EZ lesions showed evidence of recovery of EZ reflectivity on SDOCT B-scans. Remnant cone structure was identified in some areas where EZ reflectivity recovered at the following time point. Eyes that showed recovery of EZ reflectivity had a continuous external limiting membrane.

Conclusions

Remnant cone structure can persist within small SDOCT-defined EZ lesions, which can wax and wane in appearance over time. AOSLO can help to inform the interpretation of SDOCT imaging.

Translational Relevance

The absence of EZ in early macular telangiectasia type 2 and other retinal conditions needs careful interpretation because it does not always indicate an absence of underlying cone structure. The integrity of the external limiting membrane may better predict the presence of remnant cone structure and recovery of EZ reflectivity.

Systemic lipid dysregulation is a risk factor for macular neurodegenerative disease

Macular Telangiectasia type 2 (MacTel) is an uncommon bilateral retinal disease, in which glial cell and photoreceptor degeneration leads to central vision loss. The causative disease mechanism is largely unknown, and no treatment is currently available. A previous study found variants in genes associated with glycine-serine metabolism (PSPH, PHGDH and CPS1) to be associated with MacTel, and showed low levels of glycine and serine in the serum of MacTel patients. Recently, a causative role of deoxysphingolipids in MacTel disease has been established. However, little is known about possible other metabolic dysregulation. Here we used a global metabolomics platform in a case-control study to comprehensively profile serum from 60 MacTel patients and 58 controls. Analysis of the data, using innovative computational approaches, revealed a detailed, disease-associated metabolic profile with broad changes in multiple metabolic pathways. This included alterations in the levels of several metabolites that are directly or indirectly linked to glycine-serine metabolism, further validating our previous genetic findings. We also found changes unrelated to PSPH, PHGDH and CPS1 activity. Most pronounced, levels of several lipid groups were altered, with increased phosphatidylethanolamines being the most affected lipid group. Assessing correlations between different metabolites across our samples revealed putative functional connections. Correlations between phosphatidylethanolamines and sphingomyelin, and glycine-serine and sphingomyelin, observed in controls, were reduced in MacTel patients, suggesting metabolic re-wiring of sphingomyelin metabolism in MacTel patients. Our findings provide novel insights into metabolic changes associated with MacTel and implicate altered lipid metabolism as a contributor to this retinal neurodegenerative disease.

Macular Telangiectasia Type 2: Visual Acuity, Disease End Stage, and the MacTel Area: MacTel Project Report Number 8

PURPOSE

To report the visual acuity measures from the macular telangiectasia type 2 (MacTel) registry and to investigate and describe phenotypic findings in eyes with substantial vision loss resulting from MacTel.

DESIGN

Cross-sectional multicenter study.

PARTICIPANTS

Participants in the MacTel Natural History Observation Registration Study.

METHODS

Best-corrected visual acuity (BCVA) data, retinal imaging data, and clinical data were accessed from the MacTel Study databases in May 2019.

MAIN OUTCOME MEASURES

Frequency distribution of BCVA and its relationship to age; morphologic changes in eyes with very late disease stages, defined by a BCVA of 20/200 or worse; average retinal thickness of macular subfields on OCT; and dimensions of the area affected by MacTel (i.e., the MacTel area).

RESULTS

Best-corrected visual acuity was 20/50 or worse in 37.3% and 20/200 or worse in 3.8% of 4449 eyes of 2248 patients; 18.4% and 0.7% of all patients showed bilateral BCVA of 20/50 or worse and 20/200 or worse, respectively. Asymmetry between right and left eyes was present (median BCVA, 71 letters vs. 74 letters), a finding supported by more advanced morphologic changes in right eyes. Participant age correlated with BCVA, but the effect size was small. If a neovascularization or macular hole were present, bilateral occurrence was frequent (33% or 17%, respectively), and BCVA was better than 20/200 (79% or 78%, respectively) or 20/50 or better (26% or 13%, respectively). Eyes with advanced disease (BCVA, ≤20/200) showed the following characteristics: (1) atrophy of the foveal photoreceptor layer with or without associated subretinal fibrosis; (2) an affected area, termed MacTel area, limited to a horizontal diameter not exceeding the distance between the temporal optic disc margin and foveal center, and the vertical diameter not exceeding approximately 0.8 times this distance (exceptions were eyes with large active or inactive neovascular membranes); (3) reduced retinal thickness measures within the MacTel area; and (4) less frequent retinal greying and more frequent hyperpigmentations compared with eyes that have better BCVA.

CONCLUSIONS

Severe vision loss is rare in MacTel and is related to photoreceptor atrophy in most people. Results indicate disease asymmetry with slightly worse vision and more advanced disease manifestation in right eyes. MacTel-related neurodegeneration does not spread beyond the limits of the MacTel area.

Binocular Inhibition of Reading in Macular Telangiectasia Type 2

Purpose

To assess the presence of binocular gain in macular telangiectasia type 2 (MacTel) and its correlation to paracentral scotomas.

Methods

Sixty-eight patients with MacTel were consecutively recruited for a cross-sectional analysis. Best-corrected visual acuity (BCVA), reading acuity, and reading speed were tested monocularly and binocularly. Macular retinal sensitivity was examined with fundus-controlled perimetry (microperimetry). Scotomas were quantified by their size, their depth, and their proximity to the fovea.

Results

Binocular reading speed and acuity were lower than monocular reading speed and acuity in the functionally better eye (142 vs. 159 words per minute and 0.43 vs. 0.28 log reading acuity determination, P < 0.001). Magnitude of binocular inhibition of reading speed was correlated to the degree of interocular functional difference (R2 = 0.61, P < 0.001). This correlation was not found for reading acuity or BCVA (R2 < 0.03). Binocular reading speed was negatively correlated to size of right and left eye scotomas, with bigger effect size for left eye scotomas. The magnitude of binocular inhibition was correlated to size of left eye scotomas, but not of right eye scotomas. When both eyes had similar scotoma characteristics, the right eye was more frequently the better reading eye.

Conclusions

We provide evidence for the presence of binocular inhibition of reading performance in MacTel, likely due to binocular rivalry. This may result from the characteristic paracentral scotomas in noncorresponding retinal fields and, in particular, a disruptive projection of scotomas in reading direction arising from the left eyes. Patients may benefit from occluding one eye while reading.

Postretinal Detachment Retinal Displacement: How Best to Detect It?

PURPOSE

The reported incidence of postretinal detachment (RD) macular displacement varies markedly (14-72%). This may in part be due to the imaging modalities used. We compared the ability of 2 types of fundus autofluorescence (FAF) imaging modalities to detect this phenomenon.

METHODS

Prospective study of 70 eyes with macula-involving RDs. 8 weeks postoperatively, patients underwent FAF imaging with 2 machines: a confocal scanning laser ophthalmoscope (cSLO) and a digital fundus camera (FC). Images were graded for the presence of hyperautofluorescent RPE (retinal pigment epithelium) ghost vessels, indicative of retinal displacement, by 2 masked, independent graders.

RESULTS

In total, 87.1% of FC images were gradable versus 88.6% of cSLO images. Retinal displacement was detectable in 61.4% of FC images versus 52.8% of cSLO images. Vessel shift often appeared more autofluorescent on FC imaging, but choroidal vessels were more visible. Cohen's agreement between the imaging modalities was 0.50, rated as moderate agreement. For both imaging modalities, the inter- and intragrader agreement was substantial, representing good test-retest reliability.

CONCLUSIONS

Detection of post-RD retinal displacement was similar between FC and cSLO FAF imaging, with only moderate agreement between both modalities.

Serine and Lipid Metabolism in Macular Disease and Peripheral Neuropathy

BACKGROUND

Identifying mechanisms of diseases with complex inheritance patterns, such as macular telangiectasia type 2, is challenging. A link between macular telangiectasia type 2 and altered serine metabolism has been established previously.

METHODS

Through exome sequence analysis of a patient with macular telangiectasia type 2 and his family members, we identified a variant in SPTLC1 encoding a subunit of serine palmitoyltransferase (SPT). Because mutations affecting SPT are known to cause hereditary sensory and autonomic neuropathy type 1 (HSAN1), we examined 10 additional persons with HSAN1 for ophthalmologic disease. We assayed serum amino acid and sphingoid base levels, including levels of deoxysphingolipids, in patients who had macular telangiectasia type 2 but did not have HSAN1 or pathogenic variants affecting SPT. We characterized mice with low serine levels and tested the effects of deoxysphingolipids on human retinal organoids.

RESULTS

Two variants known to cause HSAN1 were identified as causal for macular telangiectasia type 2: of 11 patients with HSAN1, 9 also had macular telangiectasia type 2. Circulating deoxysphingolipid levels were 84.2% higher among 125 patients with macular telangiectasia type 2 who did not have pathogenic variants affecting SPT than among 94 unaffected controls. Deoxysphingolipid levels were negatively correlated with serine levels, which were 20.6% lower than among controls. Reduction of serine levels in mice led to increases in levels of retinal deoxysphingolipids and compromised visual function. Deoxysphingolipids caused photoreceptor-cell death in retinal organoids, but not in the presence of regulators of lipid metabolism.

CONCLUSIONS

Elevated levels of atypical deoxysphingolipids, caused by variant SPTLC1 or SPTLC2 or by low serine levels, were risk factors for macular telangiectasia type 2, as well as for peripheral neuropathy. (Funded by the Lowy Medical Research Institute and others.).

Validation of automated artificial intelligence segmentation of optical coherence tomography images

PURPOSE

To benchmark the human and machine performance of spectral-domain (SD) and swept-source (SS) optical coherence tomography (OCT) image segmentation, i.e., pixel-wise classification, for the compartments vitreous, retina, choroid, sclera.

METHODS

A convolutional neural network (CNN) was trained on OCT B-scan images annotated by a senior ground truth expert retina specialist to segment the posterior eye compartments. Independent benchmark data sets (30 SDOCT and 30 SSOCT) were manually segmented by three classes of graders with varying levels of ophthalmic proficiencies. Nine graders contributed to benchmark an additional 60 images in three consecutive runs. Inter-human and intra-human class agreement was measured and compared to the CNN results.

RESULTS

The CNN training data consisted of a total of 6210 manually segmented images derived from 2070 B-scans (1046 SDOCT and 1024 SSOCT; 630 C-Scans). The CNN segmentation revealed a high agreement with all grader groups. For all compartments and groups, the mean Intersection over Union (IOU) score of CNN compartmentalization versus group graders' compartmentalization was higher than the mean score for intra-grader group comparison.

CONCLUSION

The proposed deep learning segmentation algorithm (CNN) for automated eye compartment segmentation in OCT B-scans (SDOCT and SSOCT) is on par with manual segmentations by human graders.

High-Resolution In Vivo Fundus Angiography using a Nonadaptive Optics Imaging System

Purpose

We provide a proof of concept for the detailed characterization of retinal capillary features and surrounding photoreceptor mosaic using a customized nonadaptive optics angiography imaging system.

Methods

High-resolution fluorescein angiography (FFA) and/or indocyanine green angiography (ICGA) images were obtained using a modified Heidelberg retina angiograph (HRA2) device with a reduced scan angle enabling 3° field of view. Colocalized images of the photoreceptor mosaic also were captured in vivo using the same instrument. Visibility of vascular subbranches were compared between high-resolution images and conventional fundus angiography (FA) with a 30° field of view.

Results

High-resolution angiographic and infrared images (3° × 3° field of view, a 10-fold magnification) were obtained in 10 participants. These included seven patients with various retinal diseases, including myopic degeneration, diabetic retinopathy, macular telangiectasia, and central serous chorioretinopathy, as well as three healthy controls. Images of the retinal vasculature down to the capillary level were obtained on angiography with the ability to visualize a mean 1.2 levels more subbranches compared to conventional FA. In addition, imaging of the photoreceptor cone mosaic, to a sufficient resolution to calculate cone density, was possible. Movement of blood cells within the vasculature also was discernible on infrared videography.

Conclusions

This exploratory study demonstrates that fast high-resolution angiography and cone visualization is feasible using a commercially available imaging system.

Translational Relevance

This offers potential to better understand the relationship between the retinal neurovascular system in health and disease and the timing of therapeutic interventions in disease states.

Estimating Retinal Sensitivity Using Optical Coherence Tomography With Deep-Learning Algorithms in Macular Telangiectasia Type 2

IMPORTANCE

As currently used, microperimetry is a burdensome clinical testing modality for testing retinal sensitivity requiring long testing times and trained technicians.

OBJECTIVE

To create a deep-learning network that could directly estimate function from structure de novo to provide an en face high-resolution map of estimated retinal sensitivity.

DESIGN, SETTING, AND PARTICIPANTS

A cross-sectional imaging study using data collected between January 1, 2016, and November 30, 2017, from the Natural History Observation and Registry of macular telangiectasia type 2 (MacTel) evaluated 38 participants with confirmed MacTel from 2 centers.

MAIN OUTCOMES AND MEASURES

Mean absolute error of estimated compared with observed retinal sensitivity. Observed retinal sensitivity was obtained with fundus-controlled perimetry (microperimetry). Estimates of retinal sensitivity were made with deep-learning models that learned on superpositions of high-resolution optical coherence tomography (OCT) scans and microperimetry results. Those predictions were used to create high-density en face sensitivity maps of the macula. Training, validation, and test sets were segregated at the patient level.

RESULTS

A total of 2499 microperimetry sensitivities were mapped onto 1708 OCT B-scans from 63 eyes of 38 patients (mean [SD] age, 74.3 [9.7] years; 15 men [39.5%]). The numbers of examples for our algorithm were 67 899 (103 053 after data augmentation) for training, 1695 for validation, and 1212 for testing. Mean absolute error results were 4.51 dB (95% CI, 4.36-4.65 dB) when using linear regression and 3.66 dB (95% CI, 3.53-3.78 dB) when using the LeNet model. Using a 49.9 million-variable deep-learning model, a mean absolute error of 3.36 dB (95% CI, 3.25-3.48 dB) of retinal sensitivity for validation and test was achieved. Correlation showed a high degree of agreement (Pearson correlation r = 0.78). By paired Wilcoxon rank sum test, our model significantly outperformed these 2 baseline models (P < .001).

CONCLUSIONS AND RELEVANCE

High-resolution en face maps of estimated retinal sensitivities were created in eyes with MacTel. The maps were of unequalled resolution compared with microperimetry and were able to correctly delineate functionally healthy and impaired retina. This model may be useful to monitor structural and functional disease progression and has potential as an objective surrogate outcome measure in investigational trials.

Stereoscopic Vision in Macular Telangiectasia Type 2

PURPOSE

To investigate stereoscopic vision in patients with macular telangiectasia (MacTel) type 2 and correlate paracentral sensitivity loss to reduced stereoscopic function.

METHODS

In a prospective single-center study, 50 patients with MacTel type 2 and 25 age-matched controls were investigated. Stereoscopic function was evaluated with Lang I, Titmus, and TNO tests. Sensitivity of the central 16° was tested using fundus-controlled perimetry (microperimetry). Functional loss was quantified as depth, size, and localization of scotomata.

RESULTS

Both the Titmus and the TNO test revealed significantly reduced stereoscopic vision in patients compared to controls (p < 0.0001 for both). This applied even to patients with only relative or monocular paracentral scotoma. A strong correlation was observed for reduced stereoscopic vision with horizontal scotoma size and with the distance of scotomata from the foveal center.

CONCLUSIONS

The results indicate that stereoscopic vision is impaired early in patients with MacTel type 2. A paracentral sensitivity loss, even if mild and limited to one eye, may considerably interfere with stereoscopic function despite normal visual acuity. Projection of paracentral scotomata within the patient's central visual field plays an important role in stereoscopic vision and should be considered when interpreting stereoscopic test results.

Contrast sensitivity and visual acuity under low light conditions in macular telangiectasia type 2

Background/Aim

Macular pigment optical density (MPOD) is centrally depleted early on in macular telangiectasia type 2 (MacTel). Contrast sensitivity (CS) might be related to MPOD, and thus impaired in early MacTel. The effect of low luminance was assessed on both CS and best corrected visual acuity (BCVA).

Methods

This is a cross-sectional study. Pelli-Robson charts were used for CS testing at 1 m in photopic (110 lux) and mesopic (1 lux) conditions. BCVA was tested with ETDRS charts and low luminance visual acuity (LLVA) with a 2.0 log unit neutral density filter. MPOD was obtained with dual-wavelength autofluorescence.

Results

One hundred and three eyes of 52 patients with MacTel (mean±SD age 62.9±10.2, range 35–77) were compared with 34 healthy eyes of 17 controls (mean±SD age 65.2±7.4, range 53–78). CS was significantly lower in the eyes with MacTel. This impairment was higher in low light conditions (low light contrast sensitivity (LL-CS)). Eyes at the early stages of MacTel had significantly lower LL-CS than controls, but normal (photopic) CS. The results were similar but less pronounced for BCVA/LLVA. Decrease in CS was correlated with loss of MPOD.

Conclusions

Low light conditions have a detrimental effect on visual performance in MacTel. Impaired CS might correlate with MPOD depletion as a pathognomonic finding in MacTel. Functional impairment might precede structural disintegration, indicating dysfunction at the cellular level. The applied tests might be useful as additional functional assessments in clinical routine and as outcome measures in future interventional clinical trials.

Treatment for Macular Telangiectasia Type 2

Macular telangiectasia (MacTel) type 2 is a bilateral disease of unknown cause with localized retinal degeneration and characteristic changes of the retinal vasculature. Funduscopic findings include reduced retinal transparency, crystalline deposits, ectatic capillaries, blunted venules, retinal pigment plaques, foveal atrophy and neovascular complexes. Leakage of telangiectatic macular capillaries is a characteristic finding on fluorescein angiography, and neurosensory atrophy may be present on optical coherence tomography images. Furthermore, there is a specific depletion of macular pigment in the central retina. Depending on the development of neovascular membranes, a nonproliferative and a proliferative (neovascular) disease stage may be distinguished. To date, there is no evidence for an effective treatment of nonproliferative MacTel type 2. Patients with proliferative MacTel type 2 and hence decreasing visual function may benefit from intravitreal application of vascular endothelial growth factor inhibitors. Early treatment and a small size of the neovascular membrane might be predictive factors for visual function outcome.

Macular telangiectasia type 2

Macular telangiectasia type 2 is a bilateral disease of unknown cause with characteristic alterations of the macular capillary network and neurosensory atrophy. Its prevalence may be underestimated and has recently been shown to be as high as 0.1% in persons 40 years and older. Biomicroscopy may show reduced retinal transparency, crystalline deposits, mildly ectatic capillaries, blunted venules, retinal pigment plaques, foveal atrophy, and neovascular complexes. Fluorescein angiography shows telangiectatic capillaries predominantly temporal to the foveola in the early phase and a diffuse hyperfluorescence in the late phase. High-resolution optical coherence tomography (OCT) may reveal disruption of the photoreceptor inner segment-outer segment border, hyporeflective cavities at the level of the inner or outer retina, and atrophy of the retina in later stages. Macular telangiectasia type 2 shows a unique depletion of the macular pigment in the central retina and recent therapeutic trials showed that such depleted areas cannot re-accumulate lutein and zeaxanthin after oral supplementation. There have been various therapeutic approaches with limited or no efficacy. Recent clinical trials with compounds that block vascular endothelial growth factor (VEGF) have established the role of VEGF in the pathophysiology of the disease, but have not shown significant efficacy, at least for the non-neovascular disease stages. Recent progress in structure-function correlation may help to develop surrogate outcome measures for future clinical trials. In this review article, we summarize the current knowledge on macular telangiectasia type 2, including the epidemiology, the genetics, the clinical findings, the staging and the differential diagnosis of the disease. Findings using retinal imaging are discussed, including fluorescein angiography, OCT, adaptive optics imaging, confocal scanning laser ophthalmoscopy, and fundus autofluorescence, as are the findings using visual function testing including visual acuity and fundus-controlled microperimetry. We provide an overview of the therapeutic approaches for both non-neovascular and neovascular disease stages and provide a perspective of future directions including animal models and potential therapeutic approaches.