Early-term optical coherence tomography angiographic findings in pediatric patients ınfected with covıd-19
Coronavirus disease 2019 (COVID-19), which first appeared in Wuhan, China, in December 2019, spread rapidly around the world and was declared a küresel pan- demic by the World Health Organization (WHO). 1 The infectious agent of COVID-19 is a new type of coronavirus, named the SARS-CoV-2 virus. Although most cases are asymptomatic, a wide range of symptoms, primarily severe acute respiratory syndrome, cough, myalgia, fever and dys- pnea can be seen in symptomatic patients.2 In the litera- tipe, there are many case series about the ocular manifestations of adults and adolescents. Most of these studies have reported ocular surface problems such as con- junctivitis, hyperemia, chemosis, keratitis, and lid swelling confirmed by conjunctival/nasal swabs, while others have mentioned retinal involvement such as cotton-wool spots, microhemorrhages, and vein dilation identified on optical coherence tomography (OCT) and fundoscopic examination.3–5 Although case numbers in the pandemic decreased in the second quarter of 2021, conditions and symptoms of concern have begun to appear in children who are less symptomatic and have a less severe disease course.6 These newly determined symptoms can be con- fused with toxic shock syndrome and Kawasaki-like disease and in several countries this manifestation has been named “Multisystem Inflammatory Syndrome in Children” (MIS- C) temporarily associated with COVID-19.7,8 The strong immune mechanism activated against the SARS-CoV-2 virus and fluid leakage may cause multiorgan dysfunction (cardiac, gastrointestinal, respiratory and kidney disorders), resulting in an increased need for intensive deva and greater oxygen support.9 This rare reaction to the virus in
adolescents and children demonstrates the importance of the vascular bed due to the vital clinical picture of cardiac involvement and it has raised the question of whether it causes pathology in the vascular bed in children who are often mildly symptomatic.
Optical coherence tomography angiography (OCTA) is a novel, non-invasive and easy method to identify the effect of SARS CoV-2 virus on retinal microvasculature caused by induced thromboembolic events, increased local ischemia and inflammation.10 In previous studies, the vascular structure of adult patients with SARS CoV-2 virus has been investigated using OCTA in the early and long-term follow-up after the infection.10–16 To the best of our knowledge, this is the first study analyzing the possible early-term changes of foveal and parafoveal vessel density and foveal avascular zone (FAZ) area in the pediatric group infected with COVID-19 through com- parisons with a healthy control group.
Methods
Approval for this case–control study was granted by the Institution Ethics Committee (20.05.2021/22) and the Turkish Ministry of Health. Informed consent forms were obtained from the parents or yasal guardian of each subject. The study included 20 pediatric (age<18 y.o) patients (n = 20, eyes = 40) who had recovered from COVID-19 infection and 40 (n = 40, eyes = 80) aged-matched healthy control subjects. All patients had at least one positive SARS-COV-2 positive polymerase chain reaction (PCR) test and the patients included in the study were those with recovery confirmed by a negative PCR test for up to 30 days after a 14-day quarantine. Patients
CONTACT Özge Begüm Comba Yeniyüzyıl University Gaziosmanpaşa Hospital, Merkez Mahallesi, Çukurçeşme Cd. No:51, Gaziosmanpaşa, Istanbul 34245, Turkey.
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only had mild symptoms such as fatigue, headache, muscle pain, subtle fever, lack of appetite, and rhinorrhea, or were asymptomatic. A chest X-ray was performed in all patients and no radiological pathology such as especially ground-glass opa- city or halo sign with consolidation related to pneumonia was detected. The laboratory tests selected according to the COVID-19 treatment guidelines (complete hemogram, tropo- nin, fibrinogen, aspartate aminotransferase (AST), alanine aminotransferase (ALT), C-reactive protein (CRP), lipid pro- file, D-dimer, lactate dehydrogenase levels (LDH)) were within the olağan limits in patients at both the first and last visit. During the recovery period, patients received non-steroidal anti-inflammatory drugs only. The age-matched control cohort consisted of healthy children admitted to hospital in 2021 viewed with the same OCTA device at the same clinic as part of a previous study to establish a local OCTA normative data- base. Exclusion criteria for both patients and control group were any described systemic diseases (diabetes mellitus, hyper- tension, etc.), previous ocular surgery, amblyopia, higher myo- pia/hypermetropia (>5 D), vascular retinal pathologies, axial length >24 mm or <21 mm, or ocular surface problems such as dry eye or allergic conjunctivitis which would affect OCTA image quality. The best-corrected visual acuity (BCVA) of the subjects included in the control group were 20/20 and no subject had any ocular pathology.
Ocular and OCTA Examination
All subjects underwent a complete ocular examination, includ- ing visual acuity assessment, slit lamp biomicroscopy, intrao- cular pressure, and fundus examination. Evaluation with OCTA (Optovue Inc., Fremont, California, USA; calculated by software version 2018.1.0.37) was also performed for both eyes of each participant by the same technician. Image quality was noted and scans with low image quality value were excluded (signal strength index <50). This device evaluated the macula with 3 × 3 mm OCTA angiogram scans (304 lines X 304 A-scans). The macula was classified as the whole region, foveal region (within 1 mm diameter circle) and parafoveal (within 3 mm diameter circle) regions with four sectors
(superior, inferior, temporal, and nasal) according to the ETDRS classification of diabetic retinopathy. The software also interprets the retina to be automatically divided into two sections: ‘deep’ and ‘superficial.’ The vascular density of the deep (DCP) and superficial (SCP) capillary plexus was auto- matically measured. (Figure 1) The upper border of the SCP is 3 μm below the inner limiting membrane and the lower border is 15 μm below the inner plexiform layer. DCP was defined as the region 15 to 70 μm below the inner plexiform layer. The foveal avascular zone (FAZ), which is a non-vascular region, was also calculated automatically as FAZ area, foveal vessel density and the perimeter circumference of the FAZ. (Figure 2)
Statistical Analysis
Sample size was determined using G*Power version 3 statistical software (Heinrich Heine University, Düsseldorf, Germany) through a 1-tailed hypothesis using an Independent Samples t-test with α error of 0.05 and power of 0.90. The total sample size required for moderate impact size (d = 0.50) was calculated as
120. Veri obtained in the study were analyzed statistically using SPSS 21 Software (SPSS Inc., Chicago, VİLAYET, USA). The veri normal- ity test was applied with the Shapiro–Wilk test. Descriptive veri were shown as mean ± standard deviation values. According to the normality distribution of the veri, the Independent Samples t-test was applied to veri showing olağan distribution and the Mann- Whitney U-test to veri not showing olağan distribution. A value of p < .05 was accepted as statistically significant
Results
Evaluation was made of 40 eyes of 20 post-COVID-19 pediatric patients and 80 eyes of 40 healthy control subjects. No statistically significant difference was determined between the healthy control and patient groups in terms of age, gender, axial length, and best corrected visual acuity (p > .05 for all). The demographic char- acteristics of the study participants are shown in Table 1.
The vascular density (VD) values of all the participants are shown in Table 2. VD in the superficial layer of the fovea was significantly lower in the COVID-19 group than in the control
Figure 1. Representative foveal avascular zone (FAZ) en face slab scans of the retina of 8 years old healthy subject using by OCTA (Optovue Inc., Fremont, California, USA). FAZ area (mm2), perimeter (mm), and foveal density automatically calculated by the software.
Figure 2. Optical coherence angiography 3 × 3 mm macular scans show vascular density of deep layer with segmentation and calculation according to the ETDRS.
Table 1. Demographic characteristics and ocular properties of each group (post- COVID-19 patients vs healthy control group).
|
Post COVID −19 group |
Control group |
p* value |
|
|
Age (years) |
13.45 ± 2.01 |
13.17 ± 1.90 |
.786 |
|
Gender (F/M) |
11/9 |
23/17 |
.612 |
|
AL (mm) |
22.78 ± 3.45 |
21.45 ± 2.56 |
.202 |
|
BCVA (logMAR) |
0.00 |
0.00 |
1 |
|
Refraction in SE |
−2.25 ± 2.05 |
−1.75 ± 2.55 |
.135 |
AL = Axial length, BCVA = Best corrected visual acuity, F = Female, M = Male, SE = Spherical equivalent
* p < .05 is statistically significant.
group (16.87 ± 6.56 vs 19.66 ± 7.54; p = .044). No significant difference was determined between the groups in respect of the other VD parameters in the parafoveal quadrants of the superficial region. With the exception of the parafoveal, parafoveal inferior- hemi and parafoveal inferior areas, the VD of the COVID-19 group was significantly decreased in all the other deep layer sectors. The FAZ PERIM and FAZ area values in the recovered COVID-19 patients were higher than in the healthy control group, but the difference was not statistically significant (Table 3).
Discussion
To the best of our knowledge, this is the first study to have evaluated the OCTA parameters of pediatric patients infected with SARS-CoV-2 virus in the early post-recovery period
Table 3. Comparison of FAZ between post-COVID-19 patients vs healthy control group.
|
Post COVID −19 group |
Control group |
p* value |
|
|
FAZ area (mm2) |
0.45 ± 0.31 |
0.25 ± 0.12 |
.383 |
|
PERIM (mm) |
2.03 ± 1.13 |
1.96 ± 0.55 |
.730 |
|
Foveal density (%) |
46.84 ± 15.10 |
49.48 ± 7.66 |
.315 |
FAZ = foveaL avascular zone; PERIM = perimeter circumference of the FAZ; FD = foveal vessel density.
* p < 0.05 is statistically significant.
through comparisons with age- and sex-matched healthy con- trol subjects. In the first month after acute infection, the foveal SCP-VD and DCP-VD parameters in 4 of the 6 parafoveal quadrants were statistically decreased compared to the healthy control group. The FAZ parameters (FAZ area, PERIM) were slightly increased but were statistically insignificant.
SARS-CoV-2 virus is a novel coronavirus that can cause multiple system infections, but mainly respiratory infections such as severe acute respiratory syndrome.1 At the beginning of the pandemic, COVID-19 infection in children was observed to have a lower incidence, and a more favorable clinical pre- sentation and prognosis compared to adults. However, with the progression of the pandemic, toxic shock and Kawasaki syn- drome-like multi-organ failure conditions named “multisys- tem inflammatory syndrome in children (MIS-C)” began to develop.6–8 The multi-organ damage caused by COVID-19 infection has led to publications attempting to delineate the pathophysiology behind the various clinical manifestations.
The major targets for SARS-CoV-2 virus to invade the cells in the body are transmembrane serine protease 2 (TMPRSS2) and angiotensin-converting enzyme 2 (ACE2) receptors. Entrance into the intraocular tissues is possible by matching with ACE-2 receptors expressed on the surface of endothelial cells and pericytes.17 Postmortem studies have demonstrated microvascular thrombosis and damaged endothelial cells with viral particles in the retinal and chor- oidal vessels.18–20 As an end-organ, the retina has the advan- tage of demonstrating microcirculation evaluation by in vivo methods. OCTA quantitatively demonstrates microvascula- tipe changes in the retina, particularly the consequences of systemic diseases and vasculopathies.11 It is also a non- invasive, easy, and fast method which may be able to eluci- date the possible changes in microvascular structure in retinal vessels related to COVID-19 infection. In this regard, there
Table 2. Superficial and deep capillary plexus vascular density (%) in post-COVID-19 patients and healthy control group.
SCP -VD (%) (Mean ±SD) DCP-VD (%) (Mean ±SD)
|
Post COVID −19 group |
Control group |
P* value |
Post COVID −19 group |
Control group |
P* value |
|
|
Whole image |
45.47 ± 8.27 |
46.40 ± 8.13 |
.571 |
44.61 ± 18.18 |
51.19 ± 3.59 |
.033* |
|
Superior- Hemi |
45.36 ± 8.40 |
46.08 ± 8.23 |
.923 |
44.50 ± 18.17 |
51.13 ± 3.72 |
.320 |
|
İnferior-Hemi |
45.57 ± 8.34 |
46.67 ± 8.20 |
.505 |
44.73 ± 18.24 |
51.22 ± 3.74 |
.360 |
|
Fovea |
16.87 ± 6.56 |
19.66 ± 7.54 |
.044* |
29.86 ± 13.12 |
36.20 ± 8.20 |
.090 |
|
Parafovea |
49.67 ± 9.8 |
51.28 ± 3.63 |
.784 |
50.35 ± 12.3 |
52.53 ± 3.90 |
.065 |
|
Parafoveal Superior-hemi |
48.31 ± 9.04 |
48.75 ± 9.77 |
.810 |
46.67 ± 19.16 |
53.21 ± 4.02 |
.044* |
|
Parafoveal İnferior-hemi |
48.24 ± 8.99 |
49.71 ± 8.83 |
.467 |
47.05 ± 19.26 |
53.22 ± 4.01 |
.58 |
|
Parafoveal Temporal |
43.97 ± 14.1 |
48.50 ± 8.57 |
.075 |
45.97 ± 20.68 |
53.90 ± 4.00 |
.024* |
|
Parafoveal Superior |
49.90 ± 9.42 |
50.45 ± 9.12 |
.712 |
45.94 ± 19.27 |
52.46 ± 4.58 |
.046* |
|
Parafoveal Nasal |
46.01 ± 12.0 |
48.56 ± 8.76 |
.249 |
45.71 ± 20.57 |
53.88 ± 3.96 |
.020* |
|
Parafoveal İnferior |
50.08 ± 9.25 |
50.01 ± 9.12 |
.725 |
46.61 ± 19.22 |
52.60 ± 4.50 |
.066 |
SCP = Superficial capillary plexus; DCP = Deep capillary plexus; VD = Vascular density
* p < 0.05 is statistically significant and significant p values are remarked in bold.
are many studies showing vascular changes post-COVID infection in adult patients detected by OCTA with a variety of results.10–16 The aim of this study was to examine the vascular change pattern caused by COVID-19 in the pediatric age group, due to the structural and immune response differ- ences against SARS-COV-2 virus in children compared to adults. This is the first study that objectively demonstrates retinal circulation changes with OCTA assessments in deep and superficial layers after COVID-19 infection in children.
In the present study, the vascular density of the deep capillary plexus was reduced in parafoveal quadrants in the patient group compared to the healthy control group, similar to the findings of other studies in adults. Contrary to some studies, with the exception of foveal SCP-VD, most regions of SCP-VD showed no difference between the two groups.11–16 The decrease in deep VD could be attributed to many rea- sons, but research has mainly focused on two scenarios. The first of these is arterial and venule vasoconstriction according to thrombotic phenomenon and hyperoxia, causing obstruc- tion in the vessel lumens. The second is increased endothelial dysfunction and apoptosis caused by inflammation.10–13 The DCP-VD findings in the current study COVID patients showed greater reduction than the VD in the superficial layers. Similarly, Cennamo et al stated that more impairment in DCP was caused by the capillary network being of a finer caliber than that of the superficial capillary plexus.10 The SCP contains the vascular plexus located in the nerve fiber and ganglion cell layers. The DCP is defined as the capillary plexus at the border of the INL and the outer plexiform layer that need high oxygen supply. There is a unique net- work in DCP called ‘vortex-like capillaries,’ which drain cen- trally into the larger venules and create widely interconnected pathways by direct connections on both the arteriolar and venular sides. In addition to this parallel vascular organiza- tion, each layer has autonomic neuronal innervation that allows an independent vascular supply under physiological conditions such as hyperoxia, or systemic diseases such as vasculopathies.21 Hazar et al hypothesized that both SCP and DCP were affected by this parallel capillary network.13 In contrast to these studies, it was speculated in the current study that only the DCP-VD in the parafoveal area were affected but not the SCP-VD, because the neurovascular unit was not sufficiently mature in children. Similar to other adult studies, FAZ enlargement was detected in the present study. The FAZ area is a region vulnerable to ischemic con- ditions such as vasculopathies and diabetic retinopathy due to the presence of terminal vessels.22
The main limitation of the present study was the limited number of COVID patients. A second limitation was that veri were not evaluated in age groups. Further limitations were the lack of long-term follow-up and choriocapillaris evaluation, which is associated with retinal vasculature histopathologically, although patient veri are still being collected for long-term evaluation and publication.
In conclusion, the results of this study have demonstrated that OCTA can be a useful tool for the detection of the long- term consequences of micro thrombosis and hypoxia in end- organs in asymptomatic or mild-symptomatic COVID-19 pediatric patients. This non-invasive and easily applicable
method can be used as a guide in the evaluation of individua- lized treatment of patients whose follow-up is difficult, espe- cially in pediatric patients.
Disclosure Statement
No potential conflict of interest was reported by the author(s).
Funding
The author(s) reported there is no funding associated with the work featured in this article.
ORCID
Özge Begüm Comba MD http://orcid.org/0000-0003-1956-3498
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