Quantification of macular ischaemia in sickle cell retinopathy

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.

Sickle Eye Project: a cross-sectional, non-interventional study of the prevalence of visual impairment due to sickle cell retinopathy and maculopathy in the UK

INTRODUCTION

Sickle cell disease (SCD) is one of the most common genetic disorders in the UK, with over 15 000 people affected. Proliferative sickle cell retinopathy (SCR) is a well-described complication of SCD and can result in significant sight loss, although the prevalence in the UK is not currently known. There are currently no national screening guidelines for SCR, with wide variations in the management of the condition across the UK.

METHODS AND ANALYSIS

The Sickle Eye Project is an epidemiological, cross-sectional, non-interventional study to determine the prevalence of visual impairment due to SCR and/or maculopathy in the UK. Haematologists in at least 16 geographically dispersed hospitals in the UK linked to participating eye clinics will offer study participation to consecutive patients meeting the inclusion criteria attending the sickle cell clinic. The following study procedures will be performed: (a) best corrected visual acuity with habitual correction and pinhole, (b) dilated slit lamp biomicroscopy and funduscopy, (c) optical coherence tomography (OCT), (d) OCT angiography where available, (e) ultrawide fundus photography, (f) National Eye Institute Visual Function Questionnaire-25 and (g) acceptability of retinal screening questionnaire. The primary outcome is the proportion of people with SCD with visual impairment defined as logarithm of the minimum angle of resolution ≥0.3 in at least one eye. Secondary outcomes include the prevalence of each stage of SCR and presence of maculopathy by age and genotype; correlation of stage of SCR and maculopathy to severity of SCD; the impact of SCR and presence of maculopathy on vision-related quality of life; and the acceptability to patients of routine retinal imaging for SCR and maculopathy.

ETHICS AND DISSEMINATION

Ethical approval was obtained from the South Central-Oxford A Research Ethics Committee (REC 23/SC/0363). Findings will be reported through academic journals in ophthalmology and haematology.

Evaluation of retinal microvascular structures by optical coherence tomography angiography in primary Sjögren's syndrome

OBJECTIVES

There are insufficient data in the literature on how retinal capillaries are affected in primary Sjögren's syndrome (PSS). The aim of this study was to evaluate the retinal capillary density (CD) in PSS using optical coherence tomography angiography (OCTA).

METHODS

In this case-control study, 26 eyes from 13 PSS patients and 39 eyes from 20 healthy controls (HCs) were included. The CD in the regions of the superior capillary plexus (SCP), deep capillary plexus (DCP) and radial peripapillary capillaries (RPC) as well as assessment parameters of the foveal avascular zone (FAZ) were examined by OCTA.

RESULTS

The mean CD (%) was 50.2 ± 4.2 and 50.5 ± 3.4 in the SCP (p = 0.904), 49.2 ± 7.5 and 53.9 ± 5.7 in the DCP (p = 0.006) and 50.8 ± 2.1 and 49.8 ± 2.2 in the RPC (p = 0.088) regions in patients with PSS and HCs, respectively. In patients with PSS and HCs, the mean sizes of the FAZ were 0.243 ± 0.07 mm² and 0.283 ± 0.13 mm² (p = 0.142), and the mean sizes of the non-flow area were 0.480 ± 0.11 mm² and 0.509 ± 0.13 mm², respectively (p = 0.359). The correlation coefficients (Rho) of retinal CD in the SCP, DCP and RPC regions with disease duration were - 0.545 (p = 0.004), - 0.389 (p = 0.050) and - 0.795 (p < 0.001), respectively.

CONCLUSION

The retinal CD in PSS is lower than that in the healthy population in deep retinal capillaries, and retinal CD shows a negative correlation with disease duration in PSS.

CLINICAL TRIALS REGISTRATION

This study was not registered to clinicaltrials.gov.

Automated vessel density detection in fluorescein angiography images correlates with vision in proliferative diabetic retinopathy

Purpose

To investigate the correlation between quantifiable vessel density, computed in an automated fashion, from ultra-widefield fluorescein angiography (UWFFA) images from patients with proliferative diabetic retinopathy (PDR) with visual acuity and macular thickness.

Methods

We performed a secondary analysis of a prospective randomized controlled trial. We designed and trained an algorithm to automate retinal vessel detection from input UWFFA images. We then used our algorithm to study the correlation between baseline vessel density and best corrected visual acuity (BCVA) and CRT for patients in the RECOVERY study. Reliability of the algorithm was tested using the intraclass correlation (ICC). 42 patients from the Intravitreal Aflibercept for Retinal Non-Perfusion in Proliferative Diabetic Retinopathy (RECOVERY) trial who had both baseline UWFFA images and optical coherence tomography (OCT) data were included in our study. These patients had PDR without significant center-involving diabetic macular edema (central retinal thickness [CRT] ≤320μm).

Results

Our algorithm analyzed UWFFA images with a reliability measure (ICC) of 0.98. A positive correlation (r = 0.4071, p = 0.0075) was found between vessel density and BCVA. No correlation was found between vessel density and CRT.

Conclusions

Our algorithm is capable of reliably quantifying vessel density in an automated fashion from baseline UWFFA images. We found a positive correlation between computed vessel density and BCVA in PDR patients without center-involving macular edema, but not CRT.

Translational relevance

Our work is the first to offer an algorithm capable of quantifying vessel density in an automated fashion from UWFFA images, allowing us to work toward studying the relationship between retinal vascular changes and important clinical endpoints, including visual acuity, in ischemic eye diseases.

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.

[Foveal avascular zone and OCT angiography. An overview of current knowledge]

BACKGROUND

The foveal avascular zone (FAZ) has often been analyzed under different aspects in the last decades, mainly by fluorescence angiography (FA); however, the novel technology of optical coherence tomography angiography (OCTA) enables a non-invasive examination, visualization and quantitative analysis of the FAZ, which has recently led to many new findings, especially in a multidisciplinary manner. This article provides an overview of the investigation of the FAZ using OCTA and the new findings that have been obtained using OCTA in recent years.

METHODS

This article is based on a comprehensive literature review.

RESULTS

In many studies a good reproducibility and repeatability of the FAZ measurements by OCTA could be proven, also by comparing different OCTA devices. In patients with ocular pathologies and systemic diseases, e. g. after retinal vein occlusion or retinal surgery and in patients with diabetes mellitus without diabetic retinopathy, differences to healthy control groups and correlations to visual function could be shown. Moreover, in patients with neurological diseases, such as Alzheimer's dementia, changes of the FAZ could be identified.

CONCLUSION

The OCTA is a non-invasive technology, which enables a reliable visualization and reproducible quantification of the FAZ. The size of the FAZ seems to be altered in different retinal and systemic diseases, which also may correlate with visual function; however, long-term studies evaluating the diagnostic value of these changes in the course of the disease are currently lacking.

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.

Multifocal electroretinogram findings in sickle cell maculopathy

BACKGROUND

The aim of the present work was to describe and compare multifocal electroretinogram findings (mfERG) between patients with sickle cell disease (SCD) without clinical sign of maculopathy and controls (HbAA).

METHODS

Both HbSS (homozygous SCD) and HbSC (compound heterozygous SCD) patients, the two most frequent SCD genotypes, were included. All individuals underwent a full ophthalmologic examination (with a fundoscopy), a spectral domain ocular coherence tomography (SD-OCT) and a mfERG.

RESULTS

A total of 86 subjects were included: 54 SCD patients (107 eyes) with 32 HbSS (63 eyes) and 22 HbSC (44 eyes) and 32 controls (64 eyes). None of the eyes showed retinal clinical abnormalities. SD-OCT analysis showed that macular thickness was statistically lower in SCD eyes than in controls. mfERG analysis demonstrated a significant reduction of N1 (initial-negative deflection), and P1 (positive peak) response amplitude densities of HbSS eyes compared to HbAA eyes from the centre (<2°) and to the periphery (>15°). Implicit time response was also reduced in the centre (<2°). N1 and P1 response amplitude densities of HbSC eyes were significantly lower than those of HbAA eyes from the centre (<2°) to the periphery (>15°). N1 implicit time was statistically reduced in HbSS compared to HbSC eyes.

CONCLUSION

Our study is the first one to describe macular electrophysiological dysfunction in SCD patients. Moreover, we confirm that SCD maculopathy is equally frequent in HbSS and HbSC.

Sickle cell maculopathy: Identification of systemic risk factors, and microstructural analysis of individual retinal layers of the macula

Purpose

To identify systemic risk factors for sickle cell maculopathy, and to analyze the microstructure of the macula of Sickle Cell Disease (SCD) patients by using automated segmentation of individual retinal layers.

Methods

Thirty consecutive patients with SCD and 30 matched controls underwent spectral-domain optical coherence tomography (SD-OCT) and automated thickness measurement for each retinal layer; thicknesses for SCD patients were then compared to normal controls. Demographic data, systemic data, and lab results were collected for each SCD patient; multivariate logistic regression analysis was used to identify potential risk factors for sickle cell maculopathy.

Results

Ongoing chelation treatment (p = 0.0187) was the most predictive factor for the presence of sickle cell maculopathy; the odds were 94.2% lower when chelation was present. HbF level tended to influence sickle cell maculopathy (p = 0.0775); the odds decreased by 12.9% when HbF increased by 1%. Sickle cell maculopathy was detected in 43% of SCD patients as patchy areas of retinal thinning on SD-OCT thickness map, mostly located temporally to the macula, especially in eyes with more advanced forms of sickle cell retinopathy (p = 0.003). In comparison to controls, SCD patients had a subtle thinning of the overall macula and temporal retina compared to controls (most p<0.0001), involving inner and outer retinal layers. Thickening of the retinal pigment epithelium was also detected in SCD eyes (p<0.0001).

Conclusions

Chronic chelation therapy and, potentially, high levels of HbF are possible protective factors for the presence of sickle cell maculopathy, especially for patients with more advanced forms of sickle cell retinopathy. A subtle thinning of the overall macula occurs in SCD patients and involves multiple retinal layers, suggesting that ischemic vasculopathy may happen in both superficial and deep capillary plexi. Thinning of the outer retinal layers suggests that an ischemic insult of the choriocapillaris may also occur in SCD patients.

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.

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.

Beyond the definitions of the phenotypic complications of sickle cell disease: an update on management

The sickle hemoglobin is an abnormal hemoglobin due to point mutation (GAG → GTG) in exon 1 of the β globin gene resulting in the substitution of glutamic acid by valine at position 6 of the β globin polypeptide chain. Although the molecular lesion is a single-point mutation, the sickle gene is pleiotropic in nature causing multiple phenotypic expressions that constitute the various complications of sickle cell disease in general and sickle cell anemia in particular. The disease itself is chronic in nature but many of its complications are acute such as the recurrent acute painful crises (its hallmark), acute chest syndrome, and priapism. These complications vary considerably among patients, in the same patient with time, among countries and with age and sex. To date, there is no well-established consensus among providers on the management of the complications of sickle cell disease due in part to lack of evidence and in part to differences in the experience of providers. It is the aim of this paper to review available current approaches to manage the major complications of sickle cell disease. We hope that this will establish another preliminary forum among providers that may eventually lead the way to better outcomes.

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.

Ocular perfusion abnormalities in diabetes

PURPOSE

To review the role of ocular perfusion in the pathophysiology of diabetic retinopathy, one of the leading causes of irreversible blindness in the industrialized world.

METHODS

We carried out a Medline search of the literature published in English or with English abstracts from 1966 to 2000 using various combinations of relevant key words.

RESULTS

Hyperglycaemia leads to a wide variety of vascular abnormalities at the microvascular and macrovascular levels, including abnormal autoregulation.

CONCLUSION

Three major aspects of ocular perfusion in diabetic retinopathy require additional investigation. Firstly, the precise mechanisms that link elevated glucose to dysfunction of retinal vascular cells need to be identified. Secondly, those factors that lead to both capillary dropout and to angiogenesis, twin processes that are linked to tissue hypoxia and lead to excess perfusion, increased risk of extravascular leakage and frank haemorrhage, must be carefully delineated. Finally, once specific knowledge of disease fundamentals has been amassed, tests of therapies to reverse or prevent these pathological processes can move forward.

Foveal avascular zone in macular branch retinal vein occlusion

The mean area of the foveal avascular zone (FAZ) in normal subjects was reported as 0.231 mm2 to 0.405 mm2, using fluorescein angiography. The FAZ enlarges in vaso-occlusive diseases, especially diabetic retinopathy, sickle cell retinopathy, talc retinopathy and branch retinal vein occlusion. In the present study the FAZ of 20 patients affected by macular branch retinal vein occlusion (MBRVO) was compared with the FAZ of 41 control subjects. The FAZ mean area was 0.56 +/- 0.34 mm2 SD in the MBRVO group, while 0.26 +/- 0.07 mm2 SD in the control group, with a statistically significant difference (p < 0.001). The FAZ mean perimeter was 4.77 +/- 1.90 mm SD in the MBRVO group, and 2.36 +/- 0.32 mm SD in the control group, with a statistically significant difference (p < 0.001). Taking into account the MBRVO group, a statistical correlation was found between visual acuity impairment and FAZ enlargement (p = 0.02), but not between visual acuity impairment and macular edema (p = 0.41). In 14 cases (70%) secondary avascular microzones located in the macular sector correspondent to MBRVO were also evident. MBRVO causes an irregular enlargement of the FAZ which seems to represent the most important feature related to visual acuity impairment.