HYPERREFLECTIVE FOCI AS A PATHOGENETIC BIOMARKER IN CHOROIDEREMIA

Vogt-Koyanagi-Harada Disease: A Narrative Review

Vogt-Koyanagi-Harada (VKH) disease is an idiopathic immune-related sickness that affects multiple systems and melanocytes in organs such as the uvea, ear, and meninges. The primary cause of activity is cellular immunological responses. Vogt-Koyanagi disease is identified primarily by skin abnormalities and anterior uveitis. Harada's illness is distinguished by neurological symptoms and exudative retinal detachments, which are associated with the HLA-DR4 and HLA-DRw53 genes. Pigmented races, such as Hispanics and Native Americans, are more likely to have VKH disease. Clinical features are blurred vision, floaters, alopecia, vitiligo, diffuse choroidal inflammation with disc edema, and exudative retinal detachment. Differential diagnoses include posterior scleritis, uveal effusion syndrome, central serous chorioretinopathy, and sympathetic ophthalmitis. The investigations used are optical coherence tomography (OCT), fundus fluorescein angiography (FA), and B-scan ultrasonography (USG). Treatment is done by using systemic steroids, cycloplegics, and immunosuppressants.

Alteration of perivascular reflectivity on optical coherence tomography of branched retinal vein obstruction

This study aimed to evaluate perivascular reflectivity in patients with branched retinal vascular obstruction (BRVO) using en-face optical coherence tomography (OCT). The study retrospectively analyzed 45 patients with recurrent BRVO, 30 with indolent BRVO, and 45 age- and sex-matched controls. Using a 3.0 × 3.0-mm deep capillary plexus slab on macular scans, OCT angiography (OCTA) and structural en-face OCT scans were divided into four quadrants. Obstructive quadrants of OCTA scans were binarized using a threshold value of mean + 2 standard deviation. The selected area of high signal strength (HSS) was applied to the structural en-face OCT scans, and the corrected mean perivascular reflectivity was calculated as the mean reflectivity on the HSS area/overall en-face OCT mean reflectivity. The same procedure was performed in the quadrants of the matched controls. Regression analysis was conducted on several factors possibly associated with corrected perivascular reflectivity. The perivascular reflectivity in the obstructive BRVO quadrant was significantly higher than in the indolent BRVO and control quadrants (P = 0.009, P = 0.003). Both univariate and multivariate regression analyses showed a significant correlation between the average number of intravitreal injections (anti-vascular endothelial growth factor or dexamethasone implant) per year and refractive errors and image binarization threshold and perivascular reflectivity (P = 0.011, 0.013, < 0.001/univariate; 0.007, 0.041, 0.005/multivariate, respectively). En-face OCT scans of the deep capillary plexus slab revealed higher perivascular reflectivity in recurrent BRVO eyes than in indolent BRVO and control eyes. The results also indicate a remarkable correlation between perivascular reflectivity and the average number of intravitreal injections, suggesting a link to recurrence rates.

Automatic Segmentation of Hyperreflective Foci in OCT Images Based on Lightweight DBR Network

Hyperreflective foci (HF) reflects inflammatory responses for fundus diseases such as diabetic macular edema (DME), retina vein occlusion (RVO), and central serous chorioretinopathy (CSC). Shown as high contrast and reflectivity in optical coherence tomography (OCT) images, automatic segmentation of HF in OCT images is helpful for the prognosis of fundus diseases. Previous traditional methods were time-consuming and required high computing power. Hence, we proposed a lightweight network to segment HF (with a speed of 57 ms per OCT image, at least 150 ms faster than other methods). Our framework consists of two stages: an NLM filter and patch-based split to preprocess images and a lightweight DBR neural network to segment HF automatically. Experimental results from 3000 OCT images of 300 patients (100 DME,100 RVO, and 100 CSC) revealed that our method achieved HF segmentation successfully. The DBR network had the area under curves dice similarity coefficient (DSC) of 83.65%, 76.43%, and 82.20% in segmenting HF in DME, RVO, and CSC on the test cohort respectively. Our DBR network achieves at least 5% higher DSC than previous methods. HF in DME was more easily segmented compared with the other two types. In addition, our DBR network is universally applicable to clinical practice with the ability to segment HF in a wide range of fundus diseases.

En-face optical coherence tomography hyperreflective foci of choriocapillaris in central serous chorioretinopathy

The purpose of this study is to evaluate choroidal hyperreflective foci (HRF) changes in central serous chorioretinopathy (CSC) on en-face optical coherence tomography (OCT). Retrospective analysis of 42 patients with unilateral CSC (84 eyes, including fellow eyes for controls) and 42 age- and sex-matched controls. With 4.5 × 4.5 mm macular scans, structural en-face OCT choriocapillaris (CC) slabs were used to calculate the density and number of HRF in acute CSC eyes with serous retinal detachment (SRD), resolved CSC eyes without SRD, unaffected fellow eyes, control eyes, and 1-year follow-up eyes. Based on the 2-disc diameter (3000 μm), the en-face OCT scan was divided into foveal and perifoveal lesion and analyzed to consider the impact of SRF in HRF measurement. Regression analyses were performed on the several factors with HRF number and density in the acute and resolved CSC eyes. The perifoveal density and number of CC HRF was significantly lower in the resolved CSC eyes when compared to the acute CSC eyes (P = 0.002, both), fellow eyes (P = 0.042/density, 0.028/number), and controls (P = 0.021/density, P = 0.003/number). There was no significant difference between the acute CSC eyes, fellow eyes, controls, and 1-year follow-up eyes. As subfoveal choroidal thickness decreased and choroidal vascularity (CVI) increased, the perifoveal density and number of HRF was measured higher with a significant correlation in univariate regression analysis of the acute and resolved CSC eyes (all, P < 0.05). The authors hypothesized that stromal edema induced by choroidal congestion and hyperpermeability has the greatest influence on HRF measurement, possibly affected by inflammatory cells and materials extravasation.

Outer retinal and choriocapillaris modifications in choroideremia: three differentially impaired retinal regions and the potential diagnostic role of the external limiting membrane

BACKGROUND

The external limiting membrane (ELM) is formed by the apical processes of Müller cells attached to the inner segments of the photoreceptor cells. Both cells are implicated in the pathogenesis of choroideremia (CHM). The purpose of this study was to explore the diagnostic role of ELM in CHM.

METHODS

The study was designed as observational case series. Sixteen CHM eyes were examined by multimodal imaging and were compared to healthy controls. The main outcome was the measurement of ELM thickness and reflectivity over the follow-up, and its relationship with other multimodal imaging quantitative parameters.

RESULTS

Baseline ELM was characterized by 11 ± 1 µm of thickness and 0.68 ± 0.13 of reflectivity, resulting 8 ± 1 µm (p < 0.01) and 0.65 ± 0.14 (p > 0.05) at the last follow-up. Choriocapillaris (CC) analysis revealed 3 regions. The first was characterized by normal vessel density (VD). The second surrounding the partially preserved islet, showing significantly lower baseline VD and undergoing minor changes over the follow-up. The third was localized in the partially preserved islet, showing significantly lower VD at baseline, and resulted atrophic at the last follow-up. ELM reflectivity and ELM thickness correlated both with outer retinal atrophy progression and the CC status.

CONCLUSIONS

ELM may be considered a useful imaging biomarker in CHM. Its assessment confirmed a primary role of Müller cells impairment in the pathogenesis of CHM.

Imaging biomarkers of leukaemic choroidopathy

PURPOSE

To longitudinally investigate choroidal and choriocapillaris perfusion metrics and the number of choroidal hyperreflective foci (HRF) in patients with acute leukaemia (AL) before and after disease remission and to correlate these metrics with systemic parameters during active disease.

METHODS

Prospective, longitudinal study of 26 eyes of 14 AL patients. All patients underwent optical coherence tomography (OCT) and OCT-angiography (OCTA) in the acute phase. Subfoveal choroidal thickness (CT), total, luminal and stromal choroidal area (TCA, LCA, SCA), choroidal vascularity index (CVI), choriocapillaris flow deficits (cFD) density, and choroidal HRF number were computed. In a subset, the measurements were repeated after AL remission. Age- and gender-matched 26 healthy controls were recruited for cross-sectional comparisons.

RESULTS

Patient's mean age was 59 ± 12 years. The TCA, LCA, SCA and choroidal HRF number were significantly higher in patients than controls (p = 0.028, p = 0.044, p = 0.024 and p = 0.001, respectively). Lower haemoglobin levels were associated with lower CT (r = 0.58, p = 0.008). Higher D-dimer values were associated with lower TCA (r = -0.52, p = 0.008), lower LCA (r = -0.50, p = 0.006), higher cFD density (r = 0.41, p = 0.044) and higher choroidal HRF number (r = 0.47, p = 0.008). The CT, TCA, SCA and choroidal HRF number significantly reduced after AL remission (p = 0.001, p = 0.047, p = 0.007 and p = 0.002 respectively). The CVI increased significantly compared to the active phase (p = 0.013).

CONCLUSION

The study demonstrates a subclinical choroidal involvement in patients with AL, with relative stromal thickening in the acute phase, and normalization after disease remission. Choroidal HRF were identified as a biomarker of leukaemic choroidopathy. Choriocapillaris and choroidal vascularity were inversely correlated with a systemic pro-coagulant state.

Quantitative approaches in multimodal fundus imaging: State of the art and future perspectives

When it first appeared, multimodal fundus imaging revolutionized the diagnostic workup and provided extremely useful new insights into the pathogenesis of fundus diseases. The recent addition of quantitative approaches has further expanded the amount of information that can be obtained. In spite of the growing interest in advanced quantitative metrics, the scientific community has not reached a stable consensus on repeatable, standardized quantitative techniques to process and analyze the images. Furthermore, imaging artifacts may considerably affect the processing and interpretation of quantitative data, potentially affecting their reliability. The aim of this survey is to provide a comprehensive summary of the main multimodal imaging techniques, covering their limitations as well as their strengths. We also offer a thorough analysis of current quantitative imaging metrics, looking into their technical features, limitations, and interpretation. In addition, we describe the main imaging artifacts and their potential impact on imaging quality and reliability. The prospect of increasing reliance on artificial intelligence-based analyses suggests there is a need to develop more sophisticated quantitative metrics and to improve imaging technologies, incorporating clear, standardized, post-processing procedures. These measures are becoming urgent if these analyses are to cross the threshold from a research context to real-life clinical practice.

Inflammation in diabetic retinopathy: possible roles in pathogenesis and potential implications for therapy

Diabetic retinopathy, characterized as a microangiopathy and neurodegenerative disease, is the leading cause of visual impairment in diabetic patients. Many clinical features observed in diabetic retinopathy, such as capillary occlusion, acellular capillaries and retinal non-perfusion, aggregate retinal ischemia and represent relatively late events in diabetic retinopathy. In fact, retinal microvascular injury is an early event in diabetic retinopathy involving multiple biochemical alterations, and is manifested by changes to the retinal neurovascular unit and its cellular components. Currently, intravitreal anti-vascular endothelial growth factor therapy is the first-line treatment for diabetic macular edema, and benefits the patient by decreasing the edema and improving visual acuity. However, a significant proportion of patients respond poorly to anti-vascular endothelial growth factor treatments, indicating that factors other than vascular endothelial growth factor are involved in the pathogenesis of diabetic macular edema. Accumulating evidence confirms that low-grade inflammation plays a critical role in the pathogenesis and development of diabetic retinopathy as multiple inflammatory factors, such as interleukin-1β, monocyte chemotactic protein-1 and tumor necrosis factor -α, are increased in the vitreous and retina of diabetic retinopathy patients. These inflammatory factors, together with growth factors such as vascular endothelial growth factor, contribute to blood-retinal barrier breakdown, vascular damage and neuroinflammation, as well as pathological angiogenesis in diabetic retinopathy, complicated by diabetic macular edema and proliferative diabetic retinopathy. In addition, retinal cell types including microglia, Müller glia, astrocytes, retinal pigment epithelial cells, and others are activated, to secrete inflammatory mediators, aggravating cell apoptosis and subsequent vascular leakage. New therapies, targeting these inflammatory molecules or related signaling pathways, have the potential to inhibit retinal inflammation and prevent diabetic retinopathy progression. Here, we review the relevant literature to date, summarize the inflammatory mechanisms underlying the pathogenesis of diabetic retinopathy, and propose inflammation-based treatments for diabetic retinopathy and diabetic macular edema.

Anti-VEGF reduces inflammatory features in macular edema secondary to retinal vein occlusion

AIM

To investigate the anti-inflammatory effect of intravitreal injection of anti-vascular endothelial growth factor (anti-VEGF) in patients with macular edema secondary to retinal vein occlusion (RVO-ME).

METHODS

Twenty-eight eyes from twenty-eight treatment-naïve patients (14 males and 14 females) with RVO-ME were included in this retrospective study. The retinal vein occlusion (RVO) was comprised of both central retinal vein occlusion (CRVO, n=14) and branch retinal vein occlusion (BRVO, n=14). Intravitreal injection of anti-VEGF reagents were administered monthly for three consecutive months, in which 18 patients were injected with ranibizumab and 10 patients were injected with conbercept. All eyes were imaged with optical coherence tomography angiography (OCTA) at baseline and 1wk after monthly intravitreal anti-VEGF injection. The visual acuity (VA), central macular thickness (CMT), the number of hyperreflective foci (HRF) recognized as an inflammatory sign in OCT images, and non-perfusion area (NPA), were compared before and after anti-VEGF treatments.

RESULTS

The mean interval between baseline and follow-up was 29.4±0.79 (range, 27-48)d. Compared with the baseline, the VA improved (logMAR 1.5±0.1 vs 0.8±0.1, P<0.05) and CMT decreased (460±34.0 µm vs 268.8±12.0 µm, P<0.05), significantly, after anti-VEGF treatment. The number of HRF was decreased significantly (76.5±4.8 vs 47.8±4.3, P<0.05) after anti-VEGF treatment.

CONCLUSION

Anti-VEGF therapy is effective in treating RVO-ME. The mechanisms for the decreased HRF and the reduction of NPA by anti-VEGF therapy merits further exploration.

Correlation Between Hyperreflective Foci in the Choroid and Choroidal Discoloration in Vogt-Koyanagi-Harada Disease

Purpose

To investigate the distribution of hyperreflective choroidal foci (HCF) in eyes with Vogt-Koyanagi-Harada (VKH) disease.

Methods

We included 22 eyes of 11 patients with VKH disease in the convalescent stages and 22 eyes of age- and sex-matched normal controls. HCF were quantified using en face optical coherence tomography (OCT) images of the choroid, and the degree of fundus pigmentation was determined by the color balance of the fundus photographs. The results were then analyzed between the eyes with and without sunset glow fundus (SGF).

Results

The median age of patients with VKH disease was 58.0 (range 54.0–65.0) years, and median disease duration was 66.4 (range 8.5–147.7) months. In 22 eyes with VKH, the number and total area of HCF were correlated with the degree of fundus pigmentation (ρ = −0.671, P < 0.001; ρ = −0.612, P = 0.002, respectively). The number of HCF was significantly smaller in VKH disease–affected eyes with SGF (median, interquartile range; 134.6, 110.0–159.2) than in those without SGF (229.0, 197.0–261.0) and the eyes of normal controls (211.8, 190.3–233.4).

Conclusions

HCF distributions correlated with the degree of fundus pigmentation in eyes with VKH disease. Quantitative measurements of HCF on en face OCT images can be a novel tool in evaluating choroidal pigmentation in patients with VKH disease.

Detailed analyses of microstructure of photoreceptor layer at different severities of occult macular dystrophy by ultrahigh-resolution SD-OCT

Purpose

To analyze the microstructures of the photoreceptor layer in detail in eyes with occult macular dystrophy (OMD, Miyake's disease) by ultrahigh-resolution spectral-domain optical coherence tomography (UHR-SD-OCT).

Observations

Twenty-eight normal subjects and 5 patients with OMD of different severities were studied. Cross-sectional images through the fovea were recorded with a UHR-SD-OCT system with a depth resolution of <2.0 μm. In patients with OMD, the UHR-SD-OCT images revealed abnormal photoreceptor microstructures which were not detected in the conventional SD-OCT images. The UHR-SD-OCT images showed that the interdigitation zone (IZ) was not present and the outer segments were hyperreflective with hyperreflective dots (HRDs) aligned like string of pearls during the earlier stages. There was a disruption of the ellipsoid zone (EZ) which appeared as clusters of larger HRDs, and these HRDs became less apparent with increasing time. The outer segments became hyporeflective and rod IZ became apparent with longer duration of the disease process.

Conclusions and Importance

The UHR-SD-OCT images show detailed characteristics of the photoreceptor microstructures of different severities during the progression of OMD. These detailed observations will help in understanding the mechanisms involved in the retinal pathology and should provide important information for their treatments.

Hyperreflective Foci and Subretinal Fluid Are Potential Imaging Biomarkers to Evaluate Anti-VEGF Effect in Diabetic Macular Edema

Purpose: The aim was to investigate the effect and underlying mechanism of anti-vascular endothelial growth factor (anti-VEGF) in diabetic macular edema (DME) by optical coherence tomography angiography (OCTA). Methods: Twenty-five eyes in 18 treatment-naïve patients with DME were included. All eyes were imaged by OCTA at baseline and 1 week after monthly intravitreal aflibercept injection (IAI). Visual acuity was measured as best corrected visual acuity (BCVA). Additional parameters were evaluated by OCTA, including central macular thickness (CMT), the number of hyperreflective foci (HRF), foveal avascular zone (FAZ), vessel density (VD) in the deep capillary plexus (DCP), the en-face area of cystoid edema in DCP segmentation, and subretinal fluid (SRF) height. Results: The mean time between baseline and final follow-up by OCTA was 79.24 ± 38.15 (range, 28-163) days. Compared with baseline, BCVA was increased significantly after the 3rd IAI, while CMT was decreased significantly from the 1st IAI. SRF height and the area of cystoid edema in DCP segmentation were decreased significantly after the 2nd IAI compared with baseline. The number of HRF was decreased significantly after the 1st IAI (8.87 ± 9.38) compared with baseline (11.22 ± 10.63). However, FAZ's area and perimeter as well as VD in DCP showed no significant changes post-treatment. Conclusion: Anti-VEGF is effective in treating DME, improving visual acuity and decreasing macular edema. The decreased HRF indicates anti-inflammatory effects of aflibercept to deactivate retinal microglia/macrophages. The decreased cystoid edema and SRF height indicated improved drainage function of Müller glial cells and retinal pigment epithelium after IAI.

Gene Therapy in Inherited Retinal Diseases: An Update on Current State of the Art

Background: Gene therapy cannot be yet considered a far perspective, but a tangible therapeutic option in the field of retinal diseases. Although still confined in experimental settings, the preliminary results are promising and provide an overall scenario suggesting that we are not so far from the application of gene therapy in clinical settings. The main aim of this review is to provide a complete and updated overview of the current state of the art and of the future perspectives of gene therapy applied on retinal diseases.

Methods: We carefully revised the entire literature to report all the relevant findings related to the experimental procedures and the future scenarios of gene therapy applied in retinal diseases. A clinical background and a detailed description of the genetic features of each retinal disease included are also reported.

Results: The current literature strongly support the hope of gene therapy options developed for retinal diseases. Although being considered in advanced stages of investigation for some retinal diseases, such as choroideremia (CHM), retinitis pigmentosa (RP), and Leber's congenital amaurosis (LCA), gene therapy is still quite far from a tangible application in clinical practice for other retinal diseases.

Conclusions: Gene therapy is an extremely promising therapeutic tool for retinal diseases. The experimental data reported in this review offer a strong hope that gene therapy will be effectively available in clinical practice in the next years.

Hyperreflective foci in the choroid of normal eyes

PURPOSE

To investigate hyperreflective choroidal foci (HCF) using en face swept-source optical coherence tomography (SS-OCT) and determine the factors that contribute to the distribution of HCF in normal eyes.

METHODS

In this retrospective study, we included healthy eyes with a normal fundus. HCF were defined as hyperreflective spots on en face SS-OCT images. The number, mean area, total area, and circularity of the HCF were compared with various choroid measurements obtained using SS-OCT, SS-OCT angiography, and fundus photography.

RESULTS

We investigated 51 eyes from 51 patients. The mean patient age was 56.0 ± 14.7 years, and 32 (62.7%) were female. The number and total area of HCF did not differ between the female and male patients and the right and left eyes. The number of HCF was correlated with the stromal area of the choroid (r = 0.291, P = 0.040) and subfoveal choroidal vascularity index (r =  - 0.364, P = 0.009). The total area of HCF was correlated with the stromal area of the choroid (r = 0.283, P = 0.045). However, the number and total area of HCF were not correlated with age, degree of macular tessellation, subfoveal choroidal thickness, and choriocapillaris vascular density and flow void area.

CONCLUSION

HCF were observed in normal eyes, and their distribution was associated with the underlying stromal component of the choroid. The results of this study can be used as a reference for determining abnormal hyperreflective foci in the choroid of the eyes with various diseases.

CNGB1-related rod-cone dystrophy: A mutation review and update

Cyclic nucleotide-gated channel β1 (CNGB1) encodes the 240-kDa β subunit of the rod photoreceptor cyclic nucleotide-gated ion channel. Disease-causing sequence variants in CNGB1 lead to autosomal recessive rod-cone dystrophy/retinitis pigmentosa (RP). We herein present a comprehensive review and analysis of all previously reported CNGB1 sequence variants, and add 22 novel variants, thereby enlarging the spectrum to 84 variants in total, including 24 missense variants (two of which may also affect splicing), 21 nonsense, 19 splicing defects (7 at noncanonical positions), 10 small deletions, 1 small insertion, 1 small insertion-deletion, 7 small duplications, and 1 gross deletion. According to the American College of Medical Genetics and Genomics classification criteria, 59 variants were considered pathogenic or likely pathogenic and 25 were variants of uncertain significance. In addition, we provide further phenotypic data from 34 CNGB1-related RP cases, which, overall, are in line with previous findings suggesting that this form of RP has long-term retention of useful central vision despite the early onset of night blindness, which is valuable for patient counseling, but also has implications for it being considered a priority target for gene therapy trials.

Imaging Hyperreflective Foci as an Inflammatory Biomarker after Anti-VEGF Treatment in Neovascular Age-Related Macular Degeneration Patients with Optical Coherence Tomography Angiography

Purpose

To investigate the hyperreflective foci (HRF) as an inflammatory biomarker using optical coherence tomography angiography (OCTA) in neovascular age-related macular degeneration (AMD) patients after antivascular endothelial growth factor (anti-VEGF) treatment and its association with the retinal microcapillary density.

Methods

Twenty-five eyes from 25 patients with neovascular AMD were included in the study. All eyes were imaged with OCTA at baseline (M0) and after 3 consecutive injections (M3; injection performed each month) of anti-VEGF. The number of HRF in the superficial capillary plexus (SCP), deep capillary plexus (DCP), and outer retina was counted. The vascular density of the fovea, parafovea, and the whole macula, as well as the area of the foveal avascular zone (FAZ), was measured.

Results

The mean interval between baseline and follow-up with OCTA was 93.08 ± 5.00 (range, 85-101) days. Compared with the baseline, the number of HRF significantly decreased in DCP (7.52 ± 3.06 vs. 3.76 ± 1.48, P < 0.01) and outer retina (12.04 ± 4.91 vs. 5.88 ± 3.32, P < 0.01) after treatment. There was no significant difference for HRF number in the SCP, the vascular density (containing foveal, parafoveal, and whole macular), and FAZ area before and after treatments.

Conclusion

The number of HRF in DCP and outer retina might serve as an inflammatory biomarker in patients with neovascular AMD. The reduced HRF possibly represents the alleviation of inflammation after anti-VEGF treatment in patients with AMD.

Whole exome sequencing of a family revealed a novel variant in the CHM gene, c.22delG p.(Glu8Serfs*4), which co-segregated with choroideremia

Choroideremia is a complex form of blindness-causing retinal degeneration. The aim of the present study was to investigate the pathogenic variant and molecular etiology associated with choroideremia in a Chinese family. All available family members underwent detailed ophthalmological examinations. Whole exome sequencing, bioinformatics analysis, Sanger sequencing, and co-segregation analysis of family members were used to validate sequencing data and confirm the presence of the disease-causing gene variant. The proband was diagnosed with choroideremia on the basis of clinical manifestations. Whole exome sequencing showed that the proband had a hemizygous variant in the CHM gene, c.22delG p. (Glu8Serfs*4), which was confirmed by Sanger sequencing and found to co-segregate with choroideremia. The variant was classified as likely pathogenic and has not previously been described. These results expand the spectrum of variants in the CHM gene, thus potentially enriching the understanding of the molecular basis of choroideremia. Moreover, they may provide insight for future choroideremia diagnosis and gene therapy.