Macular and perimacular vascular remodelling sickling haemoglobinopathies

LONGITUDINAL ANALYSIS OF MICROVASCULAR CHANGES IN SICKLE CELL DISEASE USING SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

PURPOSE

To analyze the changes in macular vascular densities (VDs) and foveal avascular zone (FAZ) over a 6-year period using swept-source optical coherence tomography angiography in patients with sickle cell disease compared with unaffected control subjects.

METHODS

Thirty eyes of patients with sickle cell disease and 12 eyes of unaffected control subjects matched for age and ethnicity were examined at a 6-year interval using the same imaging protocol, including ultra-wide-field angiography, swept-source OCT, and 3 × 3-mm optical coherence tomography angiography. The macular VD and FAZ were measured on ImageJ software according to previously reported algorithms.

RESULTS

In sickle cell eyes, the mean FAZ significantly increased ( P < 0.01), and the VD decreased in the foveal (within a circle of 1.5 mm in diameter around the foveal center) and temporal areas in both the superficial and the deep capillary plexuses ( P < 0.01). The VD did not change over time in the parafoveal area (annulus between two circles of 1.5 and 3 mm in diameter) and in the superior, inferior, and nasal sectors. No worsening of peripheral retinopathy was observed in the cohort during the follow-up, except for one eye that developed sea-fan. In the control eyes, no microvascular change was observed over time in FAZ size and VD.

CONCLUSION

These longitudinal optical coherence tomography angiography findings in patients with sickle cell disease showed an enlargement of the FAZ and a decrease in VD in the temporal and perifoveal regions despite the absence of progression of peripheral retinopathy, suggesting a worsening of the macular nonperfusion over time in sickle cell disease.

ATYPICAL FOVEAL AND PARAFOVEAL ABNORMALITIES IN SICKLE CELL DISEASE

PURPOSE

The primary aim was to describe the patterns of paramacular involvement, not yet reported but that optical coherence tomography angiography can now detect in patients with sickle cell disease. The secondary aim was to search arguments concerning the physiopathogeny of paramacular involvement.

METHODS

This institutional cohort retrospective study was conducted in a Referral Center for Ophthalmological Rare Diseases. Follow-up included an ophthalmologic examination with optical coherent tomography and optical coherent tomography angiography.

RESULTS

One hundred and thirty-two patients with SCD were included. Typical sickle cell maculopathy was observed in temporal area in 84 eyes (40.0%) of SS patients and eight eyes (14.8%) of SC patients ( P < 0.001). Enlargement of the foveal avascular zone was observed in 10 eyes of eight SS patients. Two atypical parafoveal abnormalities were found in SS patients only. The first one consisted of macular thinning with normal vascularization in 15 eyes of 11 patients. The second atypical maculopathy was large areas of loss of vascularization without retinal thinning 10 eyes of six patients. Multivariate analysis did not show a statistically significant relation between the peripheral sickle retinopathy stage and the different type of sickle cell maculopathy ( P = 0.21).

CONCLUSION

Those atypical sickle cell maculopathy may correspond to early forms preceding a typical sickle cell disease maculopathy (SCDM). This would point toward several physiopathogenic mechanisms. The first one included the existence of ischemia that can be related to anemia. Presence of retinal thinning without vascular involvement point out to a neurogenic mechanism.

Acute macular infarctions in pediatric patients with hemoglobin SS disease

Purpose

To report two cases of symptomatic posterior pole arterial occlusions in patients with hemoglobin SS disease.

Observations

Two teenage patients with hemoglobin SS disease presented with visual distortions, and on dilated fundus examination and testing, they were found to have arterial occlusions involving the posterior pole. The patients were evaluated for stroke with head imaging and received exchange transfusion by hematology.

Conclusions and Importance

This case series reports the unusual findings of arterial occlusions in the posterior pole resulting in areas of retinal whitening and ischemia in patients with HbSS. While sickle cell retinopathy is typically considered a peripheral retinal disease, these findings underscore the importance of vigilance when examining patients with sickle cell disease.

Assessing the Sensitivity of OCT-A Retinal Vasculature Metrics

Purpose

The purpose of this study was to examine the sensitivity of quantitative metrics of the retinal vasculature derived from optical coherence tomography angiography (OCT-A) images.

Methods

Full retinal vascular slab OCT-A images were obtained from 94 healthy participants. Capillary loss, at 1% increments up to 50%, was simulated by randomly removing capillary segments (1000 iterations of randomized loss for each participant at each percent loss). Thirteen quantitative metrics were calculated for each image: foveal avascular zone (FAZ) area, vessel density, vessel complexity index (VCI), vessel perimeter index (VPI), fractal dimension (FD), and parafoveal intercapillary area (PICA) measurements with and without the FAZ (mean PICA, summed PICA, PICA regularity, and PICA standard deviation [PICA SD]). The sensitivity of each metric was calculated as the percent loss at which 80% of the iterations for a participant fell outside of two standard deviations from the sample's normative mean.

Results

The most used OCT-A metrics, FAZ area and vessel density, were not significantly different from normative values until 27.69% and 16.00% capillary loss, respectively. Across the remaining metrics, metric sensitivity ranged from 6.37% (PICA SD without FAZ) to 39.78% (Summed PICA without FAZ).

Conclusions

The sensitivity of vasculature metrics for detecting random capillary loss varies substantially. Further efforts simulating different patterns of capillary loss are needed for comparison. Additionally, mapping the repeatability of metrics over time in a normal population is needed to further define metric sensitivity.

Translational Relevance

Quantitative metrics vary in their ability to detect vascular abnormalities in OCT-A images. Metric choice in screening studies will need to balance expected capillary abnormalities and the quality of the OCT-A images being used.

Retinal and choroidal thickness in pediatric patients with sickle cell disease: a cross-sectional cohort study

BACKGROUND

To measure the retinal/choroidal thicknesses in the macular area of asymptomatic pediatric patients with sickle cell disease (SCD).

METHODS

This cross-sectional cohort study included 40 children (79 eyes) with SCD and 19 control patients (36 eyes). All subjects underwent spectral-domain optical coherence tomography (SD-OCT) with enhanced-depth imaging OCT. Generalized Estimating Equations (GEE) were applied to compare the outcomes between groups. P ≤ 0.05 was considered significant.

RESULTS

The choroidal thickness in the macular area in the study subfields was significantly thinner in the SCD eyes compared with control eyes (subfoveal subfield and temporal parafoveal subfield, p < 0.0001; nasal parafoveal subfield, p < 0.0001 temporal perifoveal subfield, p < 0.0001; and nasal perifoveal subfield, p < 0.0001). The variations in the retinal thickness were not significant.

CONCLUSION

EDI-OCT showed that the macular choroidal thickness is thinner in asymptomatic pediatric patients with SCD.

Quantification of intermittent retinal capillary perfusion in sickle cell disease

Pathophysiology of sickle cell disease (SCD) features intermittent vaso-occlusion of microcirculatory networks that facilitate ischemic damage. Past research has, however, relied on static images to characterize this active disease state. This study develops imaging metrics to more fully capture dynamic vascular changes, quantifying intermittent retinal capillary perfusion in unaffected controls and SCD patients using sequential optical coherence tomography angiography (OCT-A) scans. The results reveal significant dynamic variation of capillary perfusion in SCD patients compared to controls. This measurement of vaso-occlusive burden in patients would provide utility in monitoring of the disease state and in evaluating treatment efficacy.

VASCULAR COMPLEXITY ANALYSIS IN OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY OF DIABETIC RETINOPATHY

PURPOSE

This study aimed to verify the feasibility of using vascular complexity features for objective differentiation of controls and nonproliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR) patients.

METHODS

This was a cross-sectional study conducted in a tertiary, subspecialty, academic practice. The cohort included 20 control subjects, 60 NPDR patients, and 56 PDR patients. Three vascular complexity features, including the vessel complexity index, fractal dimension, and blood vessel tortuosity, were derived from each optical coherence tomography angiography image. A shifting-window measurement was further implemented to identify local feature distortions due to localized neovascularization and mesh structures in PDR.

RESULTS

With mean value analysis of the whole-image, only the vessel complexity index and blood vessel tortuosity were able to classify NPDR versus PDR patients. Comparative shifting-window measurement revealed increased sensitivity of complexity feature analysis, particularly for NPDR versus PDR classification. A multivariate regression model indicated that the combination of all three vascular complexity features with shifting-window measurement provided the best classification accuracy for controls versus NPDR versus PDR.

CONCLUSION

Vessel complexity index and blood vessel tortuosity were the most sensitive in differentiating NPDR and PDR patients. A shifting-window measurement increased the sensitivity significantly for objective optical coherence tomography angiography classification of diabetic retinopathy.

[Maculopathy in sickle cell disease]

Hintergrund

Die Sichelzellerkrankung (SZE) ist eine hereditäre Hämoglobinopathie, die durch rezidivierende vasookklusive Episoden zur Mikrozirkulationsstörung verschiedener Organsysteme mit teils letalem Ausgang führt. Bei der okulären Manifestation der SZE ist am bekanntesten die periphere Sichelzellretinopathie (SZR). Unabhängig davon kann es bereits früh im Krankheitsverlauf zur Sichelzellmakulopathie (SZM) kommen.

Methoden

Review der internationalen und deutschsprachigen Literatur zur okulären Beteiligung bei SZE mit Fokus auf die SZR und SZM sowie Überblick über aktuelle systemische Therapieansätze bei SZE anlässlich der Vorstellung zweier Patienten mit HbSS-SZE.

Ergebnis und Schlussfolgerung

Im Gegensatz zur SZR ist die SZM mit temporaler Verdünnung der inneren Netzhautschichten erst in den letzten 5 Jahren mit der Einführung von SD-OCT und OCTA vermehrt in die Literatur eingegangen. Unabhängig vom Vorliegen einer SZR kann es immerhin bei etwa der Hälfte der Patienten bereits früh im Krankheitsverlauf zu einer SZM kommen. Das Krankheitsbild wird auch in Deutschland durch den Fortschritt der systemischen Therapiemöglichkeiten und aufgrund von Migration präsenter werden. Durch Wissen um diese Komplikation der SZE kann eine frühzeitige Diagnosestellung erfolgen und unnötige Diagnostik vermieden werden.

Longitudinal assessment of quantitative ultra-widefield ischaemic and vascular parameters in sickle cell retinopathy

PURPOSE

To evaluate longitudinal quantitative ischaemic and vasculature parameters, including ischaemic index, vessel area, length and geodesic distance in sickle cell retinopathy (SCR) on ultra-widefield fluorescein angiography (UWFA).

METHODS

Optimal UWFA images from two longitudinal timepoints of 74 eyes from 45 patients with SCR were aligned and a common region of interest was determined. A deep-learning augmented ischaemia and vascular segmentation platform was used for feature extraction. Geodesic distance maps demonstrating the shortest distance within the vascular masks from the centre of the optic disc were created. Ischaemic index, vessel area, vessel length and geodesic distance were measured. Paired t-test and linear mixed effect model analysis were performed.

RESULTS

Overall, 25 (44 eyes) patients with HbSS, 14 (19 eyes) with HbSC, 6 (11 eyes) with HbSthal and other genotypes were included. Mean age was 40.1±11.0 years. Mean time interval between two UWFA studies was 23.0±15.1 months (range: 3-71.3). Mean panretinal ischaemic index increased from 10.0±7.2% to 10.9±7.3% (p<0.005). Mean rate of change in ischaemic index was 0.5±0.7% per year. Mean vessel area (p=0.020) and geodesic distance (p=0.048) decreased significantly. Multivariate analysis demonstrated baseline ischaemic index and Goldberg stage are correlated with progression.

CONCLUSION

Longitudinal ischaemic index and retinal vascular parameter measurements demonstrate statistically significant progression in SCR. The clinical significance of these relatively small magnitude changes remains unclear but may provide insights into the progression of retinal ischaemia in SCR.

Analysis of the foveal microvasculature in sickle cell disease using swept-source optical coherence tomography angiography

Ischemic microangiopathy was clearly identified in sickle cell disease (SCD) using fluorescein angiography. A prospective observational clinical study was conducted to assess the foveal avascular zone (FAZ) area and explore perifoveal microvasculature changes in the superficial (SCP) and deep (DCP) capillary plexus using optical coherence tomography angiography (OCTA) and compare two genotypes—HbS/HbS (HbSS) and HbS/HbC (HbSC)-to control. All consecutive patients with electrophoretic confirmation of SCD were included. Swept-source OCTA scans (Triton Plus, Topcon, Tokyo, Japan) with a 3 × 3-mm scanning area and ultra-wide field (UWF) retinography (California, Optos, Fife, Scotland) were recorded for all patients. For OCTA analysis, preset parameters were used to segment the SCP and DCP. The FAZ area was manually assessed. The number of vascular branching points was automatically assessed based on the vascular skeletonization using ImageJ software. Eyes were staged based on Goldberg’s classification of SCD retinopathy (SCDR) using UWF imaging. Forty-six eyes of 24 patients were included in the HbSS (n = 27) and HbSC (n = 19) groups and 16 eyes of 8 unaffected patients in a control group. In the DCP, the FAZ was significantly larger in the HbSC (p = 0.0001) and HbSS (p = 0.0004) groups compared to controls. The FAZ area in the SCP, CRT and number of superficial vascular branching points did not significantly differ between both genotypes. There were less branching points in the HbSC (p = 0.034) and HbSS (p = 0.0014) groups than in controls. The Goldberg stage was significantly higher in the HbSC group than in the HbSS group (2.21 vs. 1.22, p = 0.0062). OCTA provides useful information on macular microvasculature and structural alterations associated with SCDR. Ischemic abnormalities are more predominant in the DCP in case of SCDR and no difference was found between genotypes of patients visually asymptomatic.

Interocular asymmetry of foveal avascular zone morphology and parafoveal capillary density in sickle cell retinopathy

OBJECTIVES

To examine interocular asymmetry of foveal avascular zone (FAZ) and parafoveal capillary density metrics in sickle cell retinopathy (SCR) using optical coherence tomography angiography (OCT-A).

METHODS

This cross-sectional, retrospective study evaluated SCR patients and unaffected controls who underwent 3x3mm macular OCT-A imaging using a spectral domain-OCT system. FAZ (area, perimeter, and acircularity index) and parafoveal capillary density metrics were computed for both eyes of each participant. In unaffected controls, interocular difference in FAZ and parafoveal capillary density metrics were evaluated using Bland-Altman plots. SCR patients with interocular difference outside the upper 97.5% and lower 2.5% limits of agreement from controls were defined as having interocular asymmetry. Area under receiver operating characteristic curve (AROC) was also performed to determine the ability of the absolute interocular difference to differentiate between subjects with SCR-including non-proliferative SCR (NP-SCR) and proliferative SCR (P-SCR)-and unaffected controls.

RESULTS

Thirty-one patients with SCR (21 NP-SCR and 10 P-SCR) and 14 race-matched and age-matched controls were included for analysis. Interocular asymmetry was seen for all FAZ and parafoveal capillary density metrics in NP-SCR and P-SCR subjects. SCR subjects showed greater disease severity in the left-eye for FAZ and parafoveal capillary density metrics.

CONCLUSIONS

NP-SCR and P-SCR patients demonstrated quantifiable interocular asymmetry in FAZ and parafoveal capillary density metrics compared to unaffected subjects, with left-eye predominance in disease severity.

QUANTITATIVE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY FEATURES FOR OBJECTIVE CLASSIFICATION AND STAGING OF DIABETIC RETINOPATHY

PURPOSE

This study aims to characterize quantitative optical coherence tomography angiography (OCTA) features of nonproliferative diabetic retinopathy (NPDR) and to validate them for computer-aided NPDR staging.

METHODS

One hundred and twenty OCTA images from 60 NPDR (mild, moderate, and severe stages) patients and 40 images from 20 control subjects were used for this study conducted in a tertiary, subspecialty, academic practice. Both eyes were photographed and all the OCTAs were 6 mm × 6 mm macular scans. Six quantitative features, that is, blood vessel tortuosity, blood vascular caliber, vessel perimeter index, blood vessel density, foveal avascular zone area, and foveal avascular zone contour irregularity (FAZ-CI) were derived from each OCTA image. A support vector machine classification model was trained and tested for computer-aided classification of NPDR stages. Sensitivity, specificity, and accuracy were used as performance metrics of computer-aided classification, and receiver operation characteristics curve was plotted to measure the sensitivity-specificity tradeoff of the classification algorithm.

RESULTS

Among 6 individual OCTA features, blood vessel density shows the best classification accuracies, 93.89% and 90.89% for control versus disease and control versus mild NPDR, respectively. Combined feature classification achieved improved accuracies, 94.41% and 92.96%, respectively. Moreover, the temporal-perifoveal region was the most sensitive region for early detection of DR. For multiclass classification, support vector machine algorithm achieved 84% accuracy.

CONCLUSION

Blood vessel density was observed as the most sensitive feature, and temporal-perifoveal region was the most sensitive region for early detection of DR. Quantitative OCTA analysis enabled computer-aided identification and staging of NPDR.

Foveal avascular zone morphology and parafoveal capillary perfusion in sickle cell retinopathy

Background/aims

To assess foveal avascular zone (FAZ) morphology and parafoveal capillary perfusion in patients with various stages of sickle cell retinopathy (SCR) using optical coherence tomography angiography (OCT-A).

Methods

This is a multi-institutional retrospective study of patients with various stages of SCR compared with healthy controls. Parafoveal OCT-A images obtained using a commercial spectral domain-OCT system were reviewed. Foveal-centred 3×3 mm full vascular slab OCT-As were used for image processing and data analysis. FAZ area, perimeter, and acircularity index were determined on the OCT-A image after manual delineation of the FAZ border. Quadrant-based parafoveal capillary density and per cent area deviating from normal distribution were also measured.

Results

Fifty-two patients with SCR (33 non-proliferative and 19 proliferative) and 20 age and race-matched healthy controls were included. One randomly selected eye per study participant was analysed. FAZ perimeter and acircularity index were significantly greater in SCR eyes when compared with the controls. While parafoveal capillary density was significantly lower, per cent area deviated from normal distribution was significantly higher in SCR eyes than that of the control. However, no statistically significant difference between the two SCR stages was observed. In quadrant-based analysis, the temporal quadrant showed greater parafoveal capillary dropout due to SCR, with the most profound effect in patients with proliferative SCR.

Conclusions

Abnormal FAZ morphology and altered parafoveal capillary perfusion were found in patients with SCR. Our customised OCT-A image analysis method uniquely highlights significant quantitative alterations in perfusion density mapping in a qualitative display, with minimal obscuration of OCT-A image detail.

Supervised Machine Learning Based Multi-Task Artificial Intelligence Classification of Retinopathies

Artificial intelligence (AI) classification holds promise as a novel and affordable screening tool for clinical management of ocular diseases. Rural and underserved areas, which suffer from lack of access to experienced ophthalmologists may particularly benefit from this technology. Quantitative optical coherence tomography angiography (OCTA) imaging provides excellent capability to identify subtle vascular distortions, which are useful for classifying retinovascular diseases. However, application of AI for differentiation and classification of multiple eye diseases is not yet established. In this study, we demonstrate supervised machine learning based multi-task OCTA classification. We sought (1) to differentiate normal from diseased ocular conditions, (2) to differentiate different ocular disease conditions from each other, and (3) to stage the severity of each ocular condition. Quantitative OCTA features, including blood vessel tortuosity (BVT), blood vascular caliber (BVC), vessel perimeter index (VPI), blood vessel density (BVD), foveal avascular zone (FAZ) area (FAZ-A), and FAZ contour irregularity (FAZ-CI) were fully automatically extracted from the OCTA images. A stepwise backward elimination approach was employed to identify sensitive OCTA features and optimal-feature-combinations for the multi-task classification. For proof-of-concept demonstration, diabetic retinopathy (DR) and sickle cell retinopathy (SCR) were used to validate the supervised machine leaning classifier. The presented AI classification methodology is applicable and can be readily extended to other ocular diseases, holding promise to enable a mass-screening platform for clinical deployment and telemedicine.

Color Fundus Image Guided Artery-Vein Differentiation in Optical Coherence Tomography Angiography

Purpose

This study aimed to develop a method for automated artery-vein classification in optical coherence tomography angiography (OCTA), and to verify that differential artery-vein analysis can improve the sensitivity of OCTA detection and staging of diabetic retinopathy (DR).

Methods

For each patient, the color fundus image was used to guide the artery-vein differentiation in the OCTA image. Traditional mean blood vessel caliber (m-BVC) and mean blood vessel tortuosity (m-BVT) in OCTA images were quantified for control and DR groups. Artery BVC (a-BVC), vein BVC (v-BVC), artery BVT (a-BVT), and vein BVT (a-BVT) were calculated, and then the artery-vein ratio (AVR) of BVC (AVR-BVC) and AVR of BVT (AVR-BVT) were quantified for comparative analysis. Sensitivity, specificity, and accuracy were used as performance metrics of artery-vein classification. One-way, multilabel ANOVA with Bonferroni's test and Student's t-test were employed for statistical analysis.

Results

Forty eyes of 20 control subjects and 80 eyes of 48 NPDR patients (18 mild, 16 moderate, and 14 severe NPDR) were evaluated in this study. The color fundus image-guided artery-vein differentiation reliably identified individual arteries and veins in OCTA. AVR-BVC and AVR-BVT provided significant (P < 0.001) and moderate (P < 0.05) improvements, respectively, in detecting and classifying NPDR stages, compared with traditional m-BVC analysis.

Conclusions

Color fundus image-guided artery-vein classification provides a feasible method to differentiate arteries and veins in OCTA. Differential artery-vein analysis can improve the sensitivity of OCTA detection and classification of DR. AVR-BVC is the most-sensitive feature, which can classify control and mild NPDR, providing a quantitative biomarker for objective detection of early DR.

Analysis of Retinal Thinning Using Spectral-domain Optical Coherence Tomography Imaging of Sickle Cell Retinopathy Eyes Compared to Age- and Race-Matched Control Eyes

PURPOSE

To determine whether the retina is thinner in sickle cell patients than in race- and age-matched controls, and, if it is thinner, whether there is any association with systemic diseases.

METHODS

Sickle cell and control (age- and race-matched) patients were prospectively enrolled from a university retina clinic into this observational study. Participants underwent visual acuity testing, slit-lamp biomicroscopy, dilated ophthalmoscopy, and spectral-domain optical coherence tomography imaging. Sickle cell retinal lesions, degree of vascular tortuosity, caliber of arteriovenous anastomosis, and stage of retinopathy were noted. Early Treatment Diabetic Retinopathy Study (ETDRS) subfield measurements were compared between sickle cell and control subjects and also among sickle cell hemoglobin subtypes. Associations between ETDRS subfield measurements and hemoglobin subtype, retinopathy stage, and systemic diseases were assessed.

RESULTS

A total of 513 sickle cell eyes (260 patients) and 75 control eyes (39 patients) had median visual acuities of 20/20. ETDRS central (P = .002), inner (nasal P = .009, superior P = .021, temporal P < .001, inferior P = .017), and temporal outer (P = .012) subfield measurements were thinner in sickle cell eyes compared to control eyes. Hemoglobin SS eyes had significantly thinner inner ETDRS subfield measurements compared to SC and SThal eyes. Retinal thinning in all subfields was associated with age (P = .017) for sickle cell and control eyes. No association was found between retinal thinning and hydroxyurea use or arteriovenous anastomosis caliber.

CONCLUSIONS

The macula is thinner in sickle cell eyes compared to control eyes; retinal thickness decreases with increasing age and sickle cell retinopathy stage and is most severe in hemoglobin SS subtypes. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

Visual Function in Asymptomatic Patients With Homozygous Sickle Cell Disease and Temporal Macular Atrophy

Importance

Temporal macular involvement in sickle cell disease can now easily be detected by optical coherence tomography (OCT). However, while recent studies have demonstrated its high prevalence, little is known about its potential consequences on visual function.

Objective

To assess the visual function of patients with sickle cell disease with no visual symptoms despite temporal macular atrophy.

Design, Setting, and Participants

This retrospective case series included data collection and explorations made in a single referral center for sickle cell disease in 2016. Three patients with sickle cell disease exhibiting preserved visual acuity but showing temporal macular retinal atrophy were included.

Exposures

Patients underwent the following explorations: best-corrected distance and near visual acuity evaluation; dilated fundus examination; OCT with 12 × 6-mm thickness map; horizontal, vertical, and en face sections; OCT angiography of the 6 × 6-mm perifoveal retina; 30° and 12° central visual fields; Lanthony 15-hue color vision test; automated static contrast sensitivity test; and global electroretinography.

Main Outcomes and Measures

The OCT thickness maps were checked for areas of retinal thinning, appearing as blue patches. When present, these areas were compared with the areas of superficial and deep capillary flow loss on OCT angiography and with the scotomas on visual fields. Contrast sensitivity and color vision loss were quantified.

Results

All 3 patients included had homozygous sickle cell disease. They presented with a 20/20 distance visual acuity, and Parinaud 1,5 near visual acuity in both eyes. They were all followed up for a severe cerebral vasculopathy related to sickle cell disease. The areas of atrophy involved the inner retinal layers and were associated with an absence of signal in the deep capillary plexuses in OCT angiography. These patches of retinal thinning were also matching with scotomas in the automated visual fields. Color vision ability and contrast sensitivity were impaired in all patients. Global electroretinography findings were normal.

Conclusions and Relevance

Temporal macular atrophy in sickle cell disease may have direct consequences on visual function, including in children, even when visual acuity is preserved. Optical coherence tomographic imaging may be warranted when evaluating patients with sickle cell disease, even if asymptomatic with 20/20 visual acuity.

Sickle cell disease and the eye

PURPOSE OF REVIEW

To review recent literature pertaining to sickle cell retinopathy (SCR) and, in particular, sickle cell maculopathy.

RECENT FINDINGS

Several recent studies suggest that macular perfusion abnormalities seen in patients with sickle cell disease of various genotypes may affect both the superficial and deep capillary plexi, with a predilection for the deep capillary plexus. Further, these changes may be associated with areas of macular thinning, as well as with peripheral retinal ischemia, even in individuals without visual symptoms, contrary to what has previously been described in both diabetic retinopathy and retinal vein occlusion. Several cases also suggest that paracentral acute middle maculopathy may be the pathophysiologic mechanism by which microvascular occlusion leads to macular thinning.

SUMMARY

Sickle cell disease can manifest in a number of ways within the orbit as well as intraocularly because of its nonspecific vasoocclusive episodes. However, SCR is the most common ophthalmic manifestation of this disease. Historically, SCR has been considered a peripheral retinopathy, but the development and use of spectral-domain optical coherence tomography and optical coherence tomography angiography suggest that significant macular vascular changes occur early in this disease, even in asymptomatic individuals.

Computer-aided classification of sickle cell retinopathy using quantitative features in optical coherence tomography angiography

As a new optical coherence tomography (OCT) imaging modality, there is no standardized quantitative interpretation of OCT angiography (OCTA) characteristics of sickle cell retinopathy (SCR). This study is to demonstrate computer-aided SCR classification using quantitative OCTA features, i.e., blood vessel tortuosity (BVT), blood vessel diameter (BVD), vessel perimeter index (VPI), foveal avascular zone (FAZ) area, FAZ contour irregularity, parafoveal avascular density (PAD). It was observed that combined features show improved classification performance, compared to single feature. Three classifiers, including support vector machine (SVM), k-nearest neighbor (KNN) algorithm, and discriminant analysis, were evaluated. Sensitivity, specificity, and accuracy were quantified to assess the performance of each classifier. For SCR vs. control classification, all three classifiers performed well with an average accuracy of 95% using the six quantitative OCTA features. For mild vs. severe stage retinopathy classification, SVM shows better (97% accuracy) performance, compared to KNN algorithm (95% accuracy) and discriminant analysis (88% accuracy).

CORRELATION OF MULTIMODAL IMAGING IN SICKLE CELL RETINOPATHY

PURPOSE

To correlate macular findings on spectral domain optical coherence tomography (SDOCT) and optical coherence tomography angiography (OCTA) with quantitative ischemic index calculations on ultra-wide-field fluorescein angiography (UWFFA) in patients with sickle cell retinopathy.

METHODS

In this retrospective case series, SDOCT, OCTA, and UWFFA images of patients with sickle cell retinopathy were evaluated. Eyes were staged based on the Goldberg classification of proliferative sickle cell retinopathy. Focal areas of macular thinning were assessed on SDOCT, macular vessel density was derived from OCTA, and peripheral ischemic index was calculated from UWFFA.

RESULTS

Eighteen eyes of 10 patients were included. Mean age was 36.8 ± 16.8 years, and 6 patients (11 eyes) were SS, 3 patients (5 eyes) were SC, and 1 patient (2 eyes) was Sβ thalassemia in hemoglobin electrophoresis. Abnormal macular findings included inner retinal atrophy in 11 eyes (61%) on SDOCT, vascular remodeling and nonperfusion in the superficial and deep retinal capillary plexus in 12 eyes (67%) on OCTA, and macular microvascular abnormalities in 9 eyes (50%) on UWFFA. Sickle cell retinopathy Stage I was identified in 4 eyes (22.2%), Stage II in 8 eyes (44.4%), and Stage III in 6 eyes (33.3%). Mean ischemic index was 14.1 ± 9.1%. Ischemic index was significantly correlated with hemoglobinopathy subtype (23.7 ± 9.8%, 9.3 ± 5.4%, and 16.3 ± 3.2%, for SC, SS, and Sβ thalassemia disease, respectively), stage of sickle cell retinopathy (22.5 ± 9.2%, 12.5 ± 4.9%, and 4.5 ± 0.73% for Stages III, II, and I, respectively), and presence of retinal thinning on SDOCT (17.4 ± 9.7% vs. 8.8 ± 5.1%, respectively).

CONCLUSION

Multimodal imaging can provide a more complete description of the microvascular and structural alterations associated with sickle retinopathy. The correlation between the severity of peripheral nonperfusion and stage and subtype of retinopathy suggests that UWF imaging may be a useful tool in the evaluation of these patients.

Quantitative characteristics of sickle cell retinopathy in optical coherence tomography angiography

Early detection is an essential step for effective intervention of sickle cell retinopathy (SCR). Emerging optical coherence tomography angiography (OCTA) provides excellent three-dimensional (3D) resolution to enable label-free, noninvasive visualization of retinal vascular structures, promising improved sensitivity in detecting SCR. However, quantitative analysis of SCR characteristics in OCTA images is yet to be established. In this study, we conducted comprehensive analysis of six OCTA parameters, including blood vessel tortuosity, vessel diameter, vessel perimeter index (VPI), area of foveal avascular zone (FAZ), contour irregularity of FAZ and parafoveal avascular density. Compared to traditional retinal thickness analysis, five of these six OCTA parameters show improved sensitivity for SCR detection than retinal thickness. It is observed that the most sensitive parameters were the contour irregularity of FAZ in the superficial layer and avascular density in temporal regions, while the area of FAZ, tortuosity and mean diameter of the vessel were moderately sensitive.

Macular Microangiopathy in Sickle Cell Disease Using Optical Coherence Tomography Angiography

PURPOSE

To characterize the optical coherence tomography angiography (OCTA) appearance of the perifoveal macular microvasculature in visually asymptomatic patients with sickle cell disease, and to compare these findings with those of fluorescein angiography (FA).

DESIGN

Retrospective observational case series.

METHODS

Eighteen eyes of 9 consecutive patients with a median age of 41 years (range: 19-54 years) with electrophoretic confirmation of sickle cell disease were included and analyzed. A complete ophthalmologic examination was performed, including fundus examination, FA, and OCTA. Nine eyes of 5 healthy subjects were also analyzed with OCTA to serve as a control group.

RESULTS

OCTA demonstrated microvascular abnormalities in the perifoveal region of the macula in all eyes, whereas FA appeared normal in 9 of 18 eyes (50%). Most capillary abnormalities were located in the temporal juxtafoveal region and involved both the superficial and the deep capillary plexuses. The nonflow area (foveal avascular zone) was significantly larger in sickle cell disease patients than in the control group, both in the superficial and the deep capillary plexuses (P < .0001). The perifoveal vessel density was significantly lower in the sickle cell disease patients than in the control group in both the superficial (P = .0011) and the deep capillary plexuses (P = .0018).

CONCLUSION

OCTA provided detailed imaging of the perifoveal microvasculature in sickle cell disease. It appeared more sensitive than FA in detecting macular microangiopathy in asymptomatic patients. Microvascular abnormalities in sickle cell disease involved both the superficial and the deep capillary plexuses.

OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY OF SICKLE CELL MACULOPATHY

PURPOSE

To report a case of sickle cell retinopathy imaged with optical coherence tomography angiography.

METHODS

Case report.

RESULTS

An asymptomatic 33-year-old man with known sickle cell anemia (SS) presented for routine eye examination. Ultrawide-field fluorescein angiography confirmed areas of temporal nonperfusion without neovascularization and subtle enlargement of the foveal avascular zone in the left eye. Spectral domain optical coherence tomography showed thinning of the inner layers of the temporal macula in both eyes. Optovue split-spectrum amplitude decorrelation angiography optical coherence tomography was performed and showed reduced flow within the superficial and deep macular plexuses of each eye, most severely within the deep retinal capillary plexus. This abnormality was more extensive than could it be appreciated with conventional angiography.

CONCLUSION

This report provides evidence that optical coherence tomography angiography may be more sensitive in detecting macular capillary nonperfusion than fluorescein angiography. It also provides further evidence that the ischemic vasculopathy of sickle cell retinopathy preferentially affects the deep capillary plexus.

Detection and monitoring of sickle cell retinopathy using ultra wide-field color photography and fluorescein angiography

PURPOSE

In this study, we demonstrate the use of wide-field photography and fluorescein angiography to visualize the peripheral vascular changes and to identify patients with risk factors for developing proliferative sickle cell retinopathy.

METHODS

This is a retrospective case series of 12 eyes of 6 patients with sickle cell disease. Visual acuity testing, slit-lamp biomicroscopy, dilated fundus examinations, and noncontact wide-field fundus photography and fluorescein angiography using Optomap scanning laser ophthalmoscope (Optos, Marlborough, MA) were performed in all patients. The retinopathy was classified into proliferative and nonproliferative retinopathies, and the extent of retinopathy was measured in degrees. Wide-field images obtained using Optomap were compared with the derived seven-standard field images.

RESULTS

At the time of initial examination, 50% of the total eyes had proliferative retinopathy. All the peripheral retinas and vasculature were easily imaged within a single frame with Optomap. Six eyes met the high-risk criteria for developing proliferative changes. None of the eyes in our case series had tractional retinal detachment. The degrees of any type of sickle cell retinopathy and active neovascularization ranged from 20° to 360° and 10° to 60°, respectively. In all but one eye, wide-field images detected peripheral vascular changes missed on the seven-standard field photographs.

CONCLUSION

Wide-field fluorescein angiography and color photography enhance clinicians' ability to visualize peripheral vascular remodeling in sickle cell disease and to identify high-risk characteristics for proliferative sickle cell retinopathy.

Structural and functional correlation in sickle cell retinopathy using spectral-domain optical coherence tomography and scanning laser ophthalmoscope microperimetry

PURPOSE

To correlate macular structural changes by spectral-domain optical coherence tomography (SD-OCT) with functional changes by scanning laser ophthalmoscope (SLO) microperimetry testing in patients with sickle cell hemoglobinopathies.

DESIGN

Prospective, investigational study.

METHODS

Patients with electrophoretic confirmation of sickle cell hemoglobinopathies and normal subjects underwent SD-OCT and microperimetry testing with the OPKO Spectral OCT/SLO instrument. Based on SD-OCT findings, patients were grouped into those with focal macular thinning (Group A) and those without (Group B). Main outcome measure were mean retinal sensitivities measured by microperimetry and mean macular thicknesses in the 9 Early Treatment Diabetic Retinopathy Study (ETDRS)-like subfields.

RESULTS

Thirty-seven eyes of 19 patients with sickle cell hemoglobinopathies (SS, SC, and S-thalassemia) and 34 eyes of 34 age-similar normal controls were included. Mean age and mean logMAR best-corrected visual acuity between Groups A and B were not statistically different (39.7 years vs 36.5 years, P = .64 and 0.015 vs 0.016, P = .93, respectively). Group A had significantly thinner retinas compared to Group B in the parafoveal superior (P = .019), parafoveal temporal (P < .004), parafoveal inferior (P = .003), perifoveal superior (P = .04), perifoveal temporal (P = .0005), and perifoveal inferior (P = .045) subfields. The overall mean microperimetry retinal sensitivities of Group A were significantly less than those of Group B (14.2 dB vs 16.5 dB, P = .00005). However, there was no statistical difference between Group B and controls (16.5 dB vs 16.7 dB, P = .63).

CONCLUSION

Sickle cell patients with focal macular thinning present on SD-OCT have significantly decreased retinal sensitivities compared to those without focal thinning or normal controls based on mean microperimetry sensitivities, despite similar age and visual acuity. Microperimetry is a sensitive measurement of macular function in patients with sickle cell hemoglobinopathies.

Sickle cell-hemoglobin C retinopathy: transient obstruction of retinal and choroidal circulations and transient drying out of retinal neovessels

We present a case of sickle cell-hemoglobin C disease that presented acute retinal and choroidal peripheral non-perfusion on the base of chronic microvascular obstruction, which transiently closed retinal neovessels.

Effects of Sickle Cell Disease on the Eye: Clinical Features and Treatment

Ocular complications of the sickling disorders are multiple and require continuing assessment to detect lesions early enough for effective prophylactic therapy to maximize visual functioning. The disease requires close monitoring of the patient for progression or regression of lesions in determining the selection of therapeutic options.

Macular vasculopathy and its evolution in incontinentia pigmenti

PURPOSE

To describe macular vasculopathy in incontinentia pigmenti.

METHODS

Twelve baby girls with incontinentia pigmenti were examined under general anesthesia by fluorescein angiography of the macula. Nine eyes of 9 patients had sufficient detail to allow evaluation of capillary changes. Angiography was initiated as early as 3 months of age and was repeated in 7 eyes at 3- to 12-month intervals. Changes in capillary patterns were identified.

RESULTS

Irregularly enlarged or distorted foveal avascular zones were noted in all 9 maculas. Sparseness of the perifoveolar capillary bed was a characteristic finding. Sequential macular angiography demonstrated non-progressive (stable) capillary closure in 2 eyes; progressive closure in another macula; progressive closure plus addition or reopening of macular capillaries in 3 eyes; and central retinal artery occlusion, with cherry-red spot formation, in 1 eye at 12 days of age. In addition, progressive tractional detachment of the macula occurred in 2 of these eyes, and progressive macular neovascularization occurred in 1 eye.

CONCLUSIONS

Macular ischemia is characteristic of incontinentia pigmenti and is often progressive. It is the initiating event of a typical vasculopathy, characterized by capillary remodelling and, occasionally, by neovascularization and tractional detachment of the retina.

Comparison of fluorescein angiography with microvascular anatomy of macaque retinas

Recent anatomic work has shown that the capillary network of the fovea is multilaminar. We have identified the elements of this network that are visualized by fluorescein angiography and those that are missed. Fluorescein angiograms of monkey retinas (Macaca fascicularis) with good visualization of individual capillaries were obtained by standard clinical techniques. Retinal whole mounts were prepared from the same animals. Anatomic drawings made from the whole mounts were used to identify which parts of the capillary network were visualized angiographically. Angiographic estimates of dimensions of the foveal avascular zone corresponded closely to the anatomy. Capillary visibility declined rapidly from near perfect visualization at the edge of the foveal avascular zone to less than 40% by 900 microns eccentricity. While all the widest capillary segments (diameter 6.1-7.0 microns) were visualized, only 43% of the modal group of capillary segments (diameter 4.1-4.5 microns) were detected. When a relatively homogeneous population of capillaries was analyzed (diameters limited to the narrow range of 4.0-5.0 microns), visualization declined monotonically with depth in the retina. Capillary segments in the nerve fiber plane were visualized more than four times as effectively as segments of comparable diameter in the deepest vascular plane. High quality angiograms accurately delineate the foveal avascular zone, but they visualize only a fraction of the adjacent multilaminar network. Therefore, current techniques may not detect the earliest nonperfusion of capillaries in vaso-occlusive diseases. Capillary visibility is a joint function of diameter and of retinal depth. The decline in visualization with retinal depth implies that light scattering in the retina degrades the angiographic image.

Ocular fundus lesions in divers

Retinal fluorescein angiography was used to examine the ocular fundi of 84 divers. The retinal capillary density at the fovea was low and microaneurysms and small areas of capillary nonperfusion were seen. The divers had significantly more abnormalities of the retinal pigment epithelium than a comparison group of non-divers. Furthermore, the prevalence of fundus abnormality was related to length of diving history. All observed changes were consistent with the obstruction of the retinal and choroidal circulations. Such obstruction could be due either to intravascular bubble formation during decompression, or to altered behaviour of blood constituents and blood vessels in hyperbaric conditions.

Patterns of visual loss in untreated sickle cell retinopathy

Ophthalmic assessments of 120 patients with homozygous sickle cell (SS) disease and of 222 with sickle cell haemoglobin-C (SC) disease were conducted over a period of ten years. Visual acuity loss (V.A. less than or equal to 6/18) attributable to sickle cell retinopathy occurred in 10% of untreated eyes during a mean observation period of 6.9 years. Visual loss was strongly associated with proliferative sickle retinopathy (p less than 0.001) and most commonly resulted from vitreous haemorrhage, tractional retinal detachment and epiretinal membranes. The incidence of visual loss was 31 per 1000 eye-years observation among eyes with proliferative disease compared to 1.4 per 1000 eye-years observation among eyes with non-proliferative disease.

Recurrent visual loss in homozygous sickle cell disease

In sickle cell retinopathy vascular involvement is most frequently recognised at the retinal periphery, but obstruction of perimacular arterioles and of major retinal vessels may also occur. This report describes a patient with homozygous sickle cell (SS) disease with recurrent occlusion of major retinal vessels associated with recurring transient impairment of visual function.

Alpha thalassaemia and the macular vasculature in homozygous sickle cell disease

The interaction of homozygous alpha thalassaemia 2 with homozygous sickle cell (SS) disease results in a generally milder haematological picture with less intravascular sickling, less haemolysis, and higher haemoglobin levels. Clinically, patients are generally more mildly affected, though not all vaso-occlusive complications are reduced. Thus there is a possibility that the advantages gained by inhibition of sickling have been offset by the rheological disadvantages of the higher haemoglobin level. The capillary bed in the perimacular region of the posterior pole has been used to examine the degree of vaso-occlusion in age and sex matched controls with SS disease with and without homozygous alpha thalassaemia 2. The results demonstrated significantly less capillary abnormalities in the perimacular region of patients with alpha thalassaemia, though the size of the foveal avascular zone and the grading of perimacular capillary drop-out did not differ between the 2 genotypes. These results are compatible with a mild inhibitory effect of alpha thalassaemia on vaso-occlusion of the macular vasculature in SS disease.

Arteriolar occlusive diseases of the macula

Occlusion of retinal precapillary arterioles may be related to vascular endothelial damage, embolization, vasculitis, and other factors. Following acute retinal precapillary arteriolar occlusion in the macular area, inhibition of axoplasmic transport results in the formation of cotton-wool patches. A variable loss of retinal function occurs. During the subacute phase, reperfusion of the vascular bed is usually seen with a gradual fading of the cotton-wool patch. In the chronic phase, the only sign of the infarction may be a loss of inner retinal substance with an irregularity of the light reflex from the internal limiting membrane, the retinal depression sign. The characteristics of retinal precapillary arteriolar occlusions are reviewed and specific features of hypertensive retinopathy, talc retinopathy, and sickle cell retinopathy are discussed.

Peripheral circumferential retinal scatter photocoagulation for treatment of proliferative sickle retinopathy

Twenty-nine patients (40 eyes) with proliferative sickle retinopathy (PSR) were treated with circumferential argon laser scatter photocoagulation to zones of peripheral retinal capillary nonperfusion. Each eye was examined in a prospective fashion, with a mean follow-up of 1.4 years. Following scatter treatment, 26% of the pre-existing sea fans regressed completely, 57% regressed partially, 17% remained stable, and none showed progression. In only one eye did de novo neovascularization develop. The results compare favorably with the natural history of PSR (Condon et al, 1980), in which de novo lesions occurred in 58%, and the visual acuity was decreased to less than 20/200 in 12% of affected eyes. Severe iatrogenic complications reported following direct focal treatment of sea fans, such as vitreous hemorrhage, progressive traction retinal detachment, retinal breaks, and choroidal-retinal-vitreal neovascularization were virtually eliminated.

Irreversible visual loss in Waldenström's macroglobulinaemia

A patient with Waldenström's macroglobulinaemia presented with visual reduction in both eyes. The funduscopic and angiographic demonstrations of venous engorgement ('string of sausages'), retinal haemorrhages at all levels, retinal and disc oedema, and serous detachment of the maculas were consistent with this diagnosis. The cryoprecipitation of the immunoglobulin at a temperature slightly below body temperature precluded routine blood studies and plasmapheresis. Plasmapheresis was ultimately performed without difficulty with the patient and equipment at 88 degrees F (31 degrees C). Despite marked improvement in the funduscopic and angiographic appearance of the retina, perifoveal capillary nonperfusion and serous elevation of the macula persisted. Even when the maculas flattened in both eyes, no visual recovery occurred. Early diagnosis, even on a clinical basis when laboratory studies cannot be performed, and early plasmapheresis to reduce serum viscosity are warranted to prevent intravascular occlusion in the perifoveal capillary bed, deposition of immunoglobulin in the retina, and transudation in the subretinal space.

Macular vasculature, visual acuity, and irreversibly sickled cells in homozygous sickle cell disease

Observations of visual acuity and the conjunctival, macular, and perimacular vascularity have been assessed in patients with homozygous sickle cell (SS) disease. There were 17 matched pairs, each consisting of one patient with a high count (greater than or equal to 15%) and one with a low count (less than or equal to 5%) of irreversibly sickled cells (ISCs). The macular vascular bed was assessed by measurements of the foveal avascular zone (FAZ), perimacular avascular zones, and counts of perimacular vascular abnormalities (perimacular counts). Small foveal avascular zones and high perimacular counts were commoner in younger than older patients and there was a significant inverse correlation between size of the FAZ and the perimacular count. These observations were compatible with the hypothesis that perimacular vessel anomalies represent the early vaso-occlusive phase which progresses to ischaemia and the formation and enlargement of avascular areas. Visual acuity was assessed by Snellen's test type and by measuring contrast sensitivity. There was no obvious relationship between acuity measured by the 2 methods and no relationship between acuity and observations of macular vascularity. High ISC counts were significantly related to abnormalities of the conjunctival vasculature, but no relationship was noted with abnormalities of the macular vasculature or with visual acuity.