Coats' disease of the retina (unilateral retinal telangiectasis) caused by somatic mutation in the NDP gene: a role for norrin in retinal angiogenesis

Rare pediatric retinal diseases: A review

Rare pediatric retinal disorders present significant challenges in diagnosis and management due to their limited prevalence and diverse clinical manifestations. This paper provides a comprehensive review of select rare retinal disorders affecting the pediatric population, focussing a brief on their epidemiology, clinical characteristics, diagnostic modalities, and therapeutic interventions. Through a systematic examination of current literature and clinical case studies, this review aims to elucidate the distinct features and challenges associated with each disorder. Despite the rarity of these conditions, their impact on visual function and quality of life necessitates heightened awareness among clinicians and researchers to facilitate timely diagnosis, appropriate management, and improved outcomes for affected children as their visual systems are still developing. Furthermore, advancements in diagnostic modalities such as fundus fluorescein angiography, optical coherence tomography, electroretinography, and genetic testing are examined for their role in enhancing our understanding of rare pediatric retinal disorders and facilitating early intervention strategies. The literature selection for this article was conducted through PubMed, Google Scholar, and the Cochrane Library databases. A thorough systematic search was carried out for the concerned diseases. Relevant review articles, original research studies, case series, and reports were examined. Additionally, references from these sources were reviewed and included if they provided pertinent information on the topic. The search was not restricted by publication date.

Clinical Characteristics and Treatment Outcomes in Unilateral Coats Disease: A Global Collaborative Study

PURPOSE

To evaluate the clinical outcomes and prognostic factors in unilateral Coats disease in the era of anti-VEGF therapy.

DESIGN

Global, multicenter, retrospective case series.

SUBJECTS

Six hundred fifty-six eyes of 656 subjects with Coats disease were included in this study. Exclusion criteria were Coats disease secondary to retinitis pigmentosa as well as bilateral cases.

METHODS

Clinical data from patients with Coats disease were collected from 20 ophthalmic practices around the world. We compared early-stage (stage 1-2) and advanced-stage (stage 3-5) Coats disease in terms of clinical characteristics and treatment modalities.

MAIN OUTCOME MEASURES

Functional outcomes include achieving visual acuity (VA) of 0.3 logarithm of the minimum angle of resolution or better and VA improvement or stability. Anatomical failure was defined as the development of phthisis, chronic retinal detachment, massive fibrosis, or the requirement for enucleation.

RESULTS

Subjects with early-stage disease were significantly older, with a mean age of 17.4 ± 17.8 years, compared with 7.1 ± 7.1 years in the advanced-stage group (P < 0.001). There was a male predominance in both early and advanced stages (84.7%). Advanced disease was associated with a higher incidence of strabismus (20.2% vs. 6.7%, P < 0.001) and leukocoria (12.3% vs. 3.2%, P < 0.001). More subjects with early-stage disease received laser photocoagulation as monotherapy (44.7% vs. 21.1%, P < 0.001). Additionally, early-stage disease received more sessions of intravitreal anti-VEGF injections as adjunct therapy (4.4 ± 6.2 vs. 2.7 ± 2.1, P = 0.005). Factors associated with poorer functional outcomes included worse presenting VA, advanced disease stage, and the presence of a foveal nodule. Worse presenting VA and advanced disease stage were associated with lower likelihood of anatomical success, whereas combination therapy increased the odds of anatomical success.

CONCLUSIONS

Unilateral Coats disease predominantly affects males, regardless of disease stage. Identifying a foveal nodule is crucial for visual prognosis. Laser photocoagulation remains the primary treatment. Although anti-VEGF may prevent enucleation, its role in early-stage disease requires further clarification.

FINANCIAL DISCLOSURE(S)

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

Overlap between ophthalmology and psychiatry - A narrative review focused on congenital and inherited conditions

A number of congenital and inherited diseases present with both ocular and psychiatric features. The genetic inheritance and phenotypic variants play a key role in disease severity. Early recognition of the signs and symptoms of those disorders is critical to earlier intervention and improved prognosis. Typically, the associations between these two medical subspecialties of ophthalmology and psychiatry are poorly understood by most practitioners so we hope to provide a narrative review to improve the identification and management of these disorders. We conducted a comprehensive review of the literature detailing the diseases with ophthalmic and psychiatric overlap that were more widely represented in the literature. Herein, we describe the clinical features, pathophysiology, molecular biology, diagnostic tests, and the most recent approaches for the treatment of these diseases. Recent studies have combined technologies for ocular and brain imaging such as optical coherence tomography (OCT) and functional imaging with genetic testing to identify the genetic basis for eye-brain connections. Additional work is needed to further explore these potential biomarkers. Overall, accurate, efficient, widely distributed and non-invasive tests that can help with early recognition of these diseases will improve the management of these patients using a multidisciplinary approach.

ABNORMALITIES IN THE RETINAL CAPILLARY PLEXUSES IN COATS DISEASE IN ADULTHOOD ON OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

PURPOSE

To describe and quantify the abnormalities of the retinal capillary plexuses using optical coherence tomography angiography in Coats disease.

METHODS

Retrospective study. Eleven eyes of 11 patients with Coats disease (9 men and two women aged 32-80 years) compared with nine fellow eyes and 11 healthy control eyes. Horizontal bands of contiguous 3 × 3 mm optical coherence tomography angiograms of the superficial vascular plexus and deep capillary complex were acquired from the optic disk to 6 mm temporal to the fovea, through areas with telangiectasia visible on fluorescein angiography in 9 cases.

RESULTS

The vascular density was significantly decreased in both plexuses in eyes with Coats disease compared with normal and fellow eyes within the 6 mm temporal to the fovea (superficial vascular plexus: 21.5 vs. 29.4%, P = 0.00004 and vs. 30.3%, P = 0.00008; deep capillary complex, 16.5 vs. 23.9%, P = 0.00004 and vs. 24.7%, P = 0.00008, respectively). The fractal dimension was also significantly decreased in eyes with Coats disease (superficial vascular plexus: 1.796 vs. 1.848 P = 0.001 and vs. 1.833, P = 0.003; deep capillary complex: 1.762 vs. 1.853, P = 0.003 and vs. 1.838, P = 0.004, respectively).

CONCLUSION

Retinal plexuses' vascular density was decreased in Coats disease, including in areas with no visible telangiectasia.

Coats' Disease in a Patient With Cornelia de Lange Syndrome: Management With Laser and Bevacizumab

Cornelia de Lange syndrome is a congenital disorder with multisystem abnormalities including multiple ocular findings. The authors report a case of Coats' disease in a patient with Cornelia de Lange syndrome who was successfully treated with laser and intravitreal bevacizumab. This case demonstrates the importance of fluorescein angiography in making the diagnosis and directing treatment and the efficacy of combined laser with intravitreal anti-vascular endothelial growth factor therapy for persistent vascular leakage associated with Coats' disease in Cornelia de Lange syndrome. [J Pediatr Ophthalmol Strabismus. 2023;60(4):e45-e48.].

The role of PLVAP in endothelial cells

Endothelial cells play a major part in the regulation of vascular permeability and angiogenesis. According to their duty to fit the needs of the underlying tissue, endothelial cells developed different subtypes with specific endothelial microdomains as caveolae, fenestrae and transendothelial channels which regulate nutrient exchange, leukocyte migration, and permeability. These microdomains can exhibit diaphragms that are formed by the endothelial cell-specific protein plasmalemma vesicle-associated protein (PLVAP), the only known protein component of these diaphragms. Several studies displayed an involvement of PLVAP in diseases as cancer, traumatic spinal cord injury, acute ischemic brain disease, transplant glomerulopathy, Norrie disease and diabetic retinopathy. Besides an upregulation of PLVAP expression within these diseases, pro-angiogenic or pro-inflammatory responses were observed. On the other hand, loss of PLVAP in knockout mice leads to premature mortality due to disrupted homeostasis. Generally, PLVAP is considered as a major factor influencing the permeability of endothelial cells and, finally, to be involved in the regulation of vascular permeability. Following these observations, PLVAP is debated as a novel therapeutic target with respect to the different vascular beds and tissues. In this review, we highlight the structure and functions of PLVAP in different endothelial types in health and disease.

[Molecular genetics in diagnosis of Coats disease: combination of oligogenic variants associated with different forms of hereditary retinal dystrophy]

Coats disease (OMIM 300216) is a form of hereditary retinal dystrophy, which occurs due to congenital abnormality of retinal vessels and features unilateral exudative vitreoretinopathy. Coats disease mostly occurs sporadically; its genetic cause is still undetermined. Molecular genetic research including whole exome sequencing by the NGS method was used to define a genetic cause of the observed phenotype. Two heterozygous variants in different genomic loci associated with other forms of hereditary retinal dystrophy were detected, a rare variant in the HMCN1 gene c.9571C>T, p.(Arg3191Cys), and a known pathogenic variant in the NPHP4 gene c.2930C>T, p.(Thr977Met). The HMCN1 gene is responsible for dominant age-related macular degeneration (OMIM 603075), pathogenic variants in the NPHP4 gene cause recessive Senior-Løken syndrome 4 (OMIM 266900). These genes encode the proteins that are involved in the regulation of integrity of the blood-retinal barrier in the vascular endothelium (NPHP4) and retinal pigment epithelium (HMCN1). The identified mutation in the NPHP4 gene could lead to decreased function of the NPHP4 protein and contribute to the development of retinal degeneration, potentially of oligogenic nature.

Longitudinal characterization and treatment response of retinal arterial macroaneurysms in adult-onset coats disease

Purpose

To perform longitudinal analysis of retinal arterial macroaneurysms in 3 patients with adult-onset Coats disease.

Observations

Three eyes of three patients with adult-onset Coats disease were followed longitudinally for 4–15 years. Ultra-widefield images and montage color fundus photographs of affected eyes were analyzed. Size, retinal location, and grading for predominant characteristic (hemorrhagic, exudative, or quiescent) of each individual macroaneurysm were followed longitudinally from the time of onset. Fifty-one individual retinal arterial macroaneurysms were identified. The distance of any lesion-associated hemorrhage or exudation present from the foveal center was measured. Macroaneurysms were located in all quadrants of the retina, with the majority (37/51) graded as hemorrhagic at lesion onset. Hemorrhagic and exudative macroaneurysms that entered the quiescent phase remained quiescent for an average of 26 months. Seven macroaneurysms were found to have hemorrhage or exudation that came within 125 μm of the fovea and all three eyes followed demonstrated a longitudinal decrease in visual acuity despite laser and intravitreal injection therapy. At the initial visit, visual acuities ranged from 20/40 to 20/200, but decreased to 20/80 to 20/320 by the last follow-up visit.

Conclusion and Importance

There are many challenges in treating patients with adult-onset Coats disease. Long-term loss of visual acuity often results from sequelae of hemorrhage and exudation affecting the macula.

Fovea-threatening and fovea-involving peripheral Coats disease: effects of posture and intervention

BACKGROUND

We believe that our experience with patients presenting with Coats disease and macular sparing should be shared with our colleagues. We would like to show the effect of posture and prompt intervention in cases with fovea-threatening and/or fovea-involving peripheral Coats disease (FTPCD). This association has been poorly debated in our specialty and literature. We call the attention for the unexpexted scenario of observing the lost of the fovea during some types of traditional and prompt interventional treatments of these cases with previous 20/20 vision (something that we have been studying and observing for many years). In order to publish our best representative cases, we have chosen 8 Brazilian patients (age range, 7-62 years; 5 male) with FTPCD. All patients underwent multimodal imaging and different treatments (observation, sleep-posture repositioning, laser, intraocular steroids, and/or anti-vascular endothelial growth factor therapy). All patients, initially, informed to adopt a sleeping lateral-down position, favoring exudation shifting to the fovea pre-treatment. Most promptly-treated patients in this way (n = 4), developed subretinal fluid and exudates in the macula and some had irreversible central visual loss (n = 3). Patients with recent fovea-involving exudation who changed postural sleep position (to protect the foveal area) before and during treatment fared better, with some preserved central vision and an intact fovea (n = 5). The fundus status was correlated with the gravitational effects of posture before and after treatment. Despite prepared as an observational/interventional study, with a small number of cases, the most difficult part is documenting the sleep position of these patients and its influence in the outcomes as there is not good way to prove how well or poorly the positioning occurred in our cases. Finally, we also intended to call the attention to the fact that Coats disease must be studied in all its clinical stage variants and not only seen as a potential blinding and incurable ocular disease.

CASE PRESENTATION

This study is a retrospective and/or interventional analysis of eight cases with a less severe clinical variant of classic Coats disease that we refer to as fovea-threatening and fovea-involving peripheral Coats disease (FTPCD). All cases were unilateral with no systemic disease or family history of Coats disease. The bilateral anterior segment and intraocular pressure were normal in all patients. The characteristics of all patients are shown in the Table.

CONCLUSION

The funduscopic features of FTPCD are fundamental to disease understanding and optimal management. Habitual posturing may affect the fundus morphologic features of retinal exudation as observed in all current patients with exudative peripheral Coats disease. When sleep habitual posture is not observed in patients with FTPCD, the effects of prompt invasive treatments can cause rapid visual loss because of foveal subretinal pooling of exudates post-treatment. Initial vigilant adjusting of the habitual sleep posture for several patients with FTPCD, before the indication of traditional invasive treatments (laser and/or pharmacologic medications) can result in improved vision and fundoscopic morphologic features.

Genetic evaluation in phenotypically discordant monozygotic twins with Coats Disease

PURPOSE

To report the unique case of a pair of phenotypically discordant monozygotic twins, with one of them affected by unilateral Coats disease.

CASE REPORT

Both patients underwent a complete ophthalmologic evaluation and were genetically tested with whole-exome sequencing (WES). Any known or unknown potential genetic determinant of Coats disease wasn't found.

CONCLUSION

It may suggest a non-genetic etiology for this disorder. This represents, to the best of our knowledge, the first case of genetic analysis of monozygotic twins, one of whom is affected by Coats disease. Further studies are warranted, including performing genetic analysis directly on retinal biopsy tissue.

Spectrum of Mutations in NDP Resulting in Ocular Disease; a Systematic Review

Aims and Rationale: The inner retina is supplied by three intraretinal capillary plexi whereas the outer retina is supplied by the choroidal circulation: NDP is essential for normal intraretinal vascularisation. Pathogenic variants in NDP (Xp11.3) may result in either a severe retinal phenotype associated with hearing loss (Norrie Disease) or a moderate retinal phenotype (Familial Exudative Vitreoretinopathy, FEVR). However, little is known about whether the nature or location of the NDP variant is predictive of severity. In this systematic review we summarise all reported NDP variants and draw conclusions about whether the nature of the NDP variant is predictive of the severity of the resulting ocular pathology and associated hearing loss and intellectual disability. Findings: 201 different variants in the NDP gene have been reported as disease-causing. The pathological phenotype that may result from a disease-causing NDP variant is quite diverse but generally comprises a consistent cluster of features (retinal hypovascularisation, exudation, persistent foetal vasculature, tractional/exudative retinal detachment, intellectual disability and hearing loss) that vary predictably with severity. Previous reviews have found no clear pattern in the nature of NDP mutations that cause either FEVR or Norrie disease, with the exception that mutations affecting cysteine residues have been associated with Norrie Disease and that visual loss amongst patients with Norrie disease tends to be more severe if the NDP mutation results in an early termination of translation as opposed to a missense related amino acid change. A key limitation of previous reviews has been variability in the case definition of Norrie disease and FEVR amongst authors. We thus reclassified patients into two groups based only on the severity of their retinal disease. Of the reported pathogenic variants that have been described in more than one patient, we found that any given variant caused an equivalent severity of retinopathy each time it was reported with very few exceptions. We therefore conclude that specific NDP mutations generally result in a consistent retinal phenotype each time they arise. Reports by different authors of the same variant causing either FEVR or Norrie disease conflict primarily due to variability in the authors' respective case definitions rather than true differences in disease severity.

Structure and function of the retina of low-density lipoprotein receptor-related protein 5 (Lrp5)-deficient rats

Loss-of-function mutations in the Wnt co-receptor, low-density lipoprotein receptor-related protein 5 (LRP5), result in familial exudative vitreoretinopathy (FEVR), osteoporosis-pseudoglioma syndrome (OPPG), and Norrie disease. CRISPR/Cas9 gene editing was used to produce rat strains deficient in Lrp5. The purpose of this study was to validate this rat model for studies of hypovascular, exudative retinopathies. The retinal vasculature of wildtype and Lrp5 knockout rats was stained with Giffonia simplifolia isolectin B4 and imaged by fluorescence microscopy. Effects on retinal structure were investigated by histology. The integrity of the blood-retina barrier was analyzed by measurement of permeability to Evans blue dye and staining for claudin-5. Retinas were imaged by fundus photography and SD-OCT, and electroretinograms were recorded. Lrp5 gene deletion led to sparse superficial retinal capillaries and loss of the deep and intermediate plexuses. Autofluorescent exudates were observed and are correlated with increased Evans blue permeability and absence of claudin-5 expression in superficial vessels. OCT images show pathology similar to OCT of humans with FEVR, and retinal thickness is reduced by 50% compared to wild-type rats. Histology and OCT reveal that photoreceptor and outer plexiform layers are absent. The retina failed to demonstrate an ERG response. CRISPR/Cas9 gene-editing produced a predictable rat Lrp5 knockout model with extensive defects in the retinal vascular and neural structure and function. This rat model should be useful for studies of exudative retinal vascular diseases involving the Wnt and norrin pathways.

Severe Exudative Vitreoretinopathy as a Common Feature for CTNNB1, KIF11 and NDP Variants Plus Sector Degeneration for KIF11

PURPOSE

To characterize ocular phenotypes in patients with CTNNB1, KIF11, or NDP variants.

DESIGN

Retrospective case series.

METHODS

Seventy-four patients from 59 unrelated families with CTNNB1, KIF11, and NDP variants were enrolled based on exome sequencing. The clinical data of ophthalmoscope, fundus photography, fluorescein angiography, and ocular ultrasound scan were evaluated.

RESULTS

A total of 55 potential pathogenic variants were identified, including 26 in KIF11 (28 families), 23 in NDP (25 families), and 6 in CTNNB1 (6 families). In total, 74 patients from the 59 families carried the variants, in whom clinical data were available from 70 patients for the current analysis. Severe familial exudative vitreoretinopathy (FEVR), stages 4 and 5, was present in 72.9% (51/70) of patients. In addition, panretinal or sector chorioretinal degeneration along with FEVR is a specific feature associated with KIF11 variants, present in 93.8% (30/32) of patients. FEVR-like change was observed in almost all patients with rare hemizygous variants in NDP, patients with heterozygous truncation variants in CTNNB1, as well as patients with heterozygous truncation or damaging missense variants in KIF11.

CONCLUSIONS

Severe FEVR-like change with or without significant chorioretinopathy is a common feature in addition to neurodevelopmental disorders for variants in CTNNB1, KIF11, and NDP. In our cohort, the frequency of families with variants in KIF11 was comparable to that in TSPAN12, so as for NDP. Recognizing the characteristics of variants in the 3 genes and associated ocular phenotypes may enrich our understanding and potential management of this disease.

Phenotype of Coats disease in females

Objective

To determine whether the clinical presentation of Coats disease differs between males and females.

Methods and analysis

Records of patients diagnosed with Coats disease at a single institution were retrospectively reviewed. Demographic data, main reason for initial consultation, comprehensive ocular examination at diagnosis and modalities of treatments during the follow-up were recorded.

Results

Records from 114 patients with Coats disease were analysed. Ninety-eight patients (86%) were male and 16 (14%) female. Mean age at diagnosis was 6.2 years±6.1 in males and 7.4 years±4.7 in females. The main initial reason for consultation was strabismus in males and decreased visual acuity in females. Stage severity at diagnosis was similar in the two groups with half of the patients presenting with stage 2B2 or lower. The extension of peripheral retinal telangiectasia was also similar (mean: 6.2±3.4 and 5.8±4.0, respectively), as was the extension of intraretinal exudation (mean: 5.0±4.5 and 5.8±4.4) and the frequency of a subfoveal nodule at diagnosis (40% vs 30%, respectively). There was no distinction between the number of laser photocoagulation or cryotherapy sessions required for both groups during the follow-up.

Conclusions

Coats disease presentation does not differ between genders despite being much rarer in females. We propose a pathogenic mechanism accounting for the gender-dependent incidence combined with gender-independent expressivity of Coats disease.

Whole-Exome Sequencing Reveals Novel NDP Variants in X-Linked Familial Exudative Vitreoretinopathy

PURPOSE

To investigate causative variants in three Chinese families affected with familial exudative vitreoretinopathy (FEVR).

METHODS

Three unrelated Chinese families were recruited in this study. The three probands and their family members experienced a comprehensive age-appropriate eye examination and genetic analysis. Luciferase assay was performed to evaluate impacts of variants on Norrin/β-catenin signaling activity.

RESULTS

Here we report two novel NDP variants associated with FEVR in three families, including c.17T>C (p.Leu6Pro) in family 1 and c.58G>A (p.Gly20Arg) in family 2 and 3. These two variants were co-segregated with the disease phenotypes within each family. In addition, both variants resulted in compromised Norrin/β-catenin signaling activity.

CONCLUSION

Our study identified two FEVR-associated pathogenic variants in NDP, which expanded the variant spectrum and provided information for the genetic diagnosis of FEVR.

A novel frameshift c.22_25dupGCAT mutation of the NDP gene in a Chinese infant with Norrie disease: A case report

RATIONALE

Norrie disease (ND) is a rare X-linked recessive disease characterized by bilateral congenital blindness and auditory impairments. According to the previous studies, Norrin cystine knot growth factor (NDP) gene have been found to be responsible for ND. Herein, we report a case of ND with a novel mutation in NDP and elucidate the clinical and molecular characteristics of this patient.

PATIENT CONCERNS

A 2-month-old Chinese male infant presented with gray-white opacification in the bilateral cornea. Vitreous opacity and retinal detachment were observed on ocular ultrasound. Furthermore, a novel de novo hemizygous mutation (c.22_25dupGCAT, p.S9Cfs∗18) in exon 2 of the NDP gene was identified by next-generation sequencing. SWISS-MODEL predicted that the c.22_25dupGCAT mutation truncated the NDP protein.

DIAGNOSIS

Based on the above clinical and genetic evidence, this patient was eventually diagnosed with ND.

INTERVENTIONS

Currently, no clinical therapy is available for ND.

OUTCOMES

In addition to the typical ocular symptoms, no other abnormalities were observed. The patient's vital signs remained stable and normal.

LESSON

A novel causative mutation of NDP was identified using next-generation sequencing. Our report expands the pathogenic mutation spectrum of NDP and facilitates genetic counseling and prenatal diagnosis. Additionally, we emphasize the importance of molecular genetic testing in the diagnosis of ND.

Clinical and Histopathologic Correlates of Asymmetric Retinitis Pigmentosa

Importance

Asymmetric retinitis pigmentosa (RP) is a rare presentation of a normally symmetric condition. Histopathologic evidence should be examined to see if this asymmetry extends to the tissue and cellular levels.

Objective

To determine whether additional information can be obtained about asymmetric RP from studying clinical imaging and pathology correlates, including pathology samples from autopsied eyes.

Design, Setting, and Participants

In this case report, clinical and postmortem histopathological characteristics were compared in 2 eyes of a patient in her 50s with asymmetric RP. Individuals with rare mendelian diseases, such as RP, were studied using data from the curated National Eye Institute Eye Pathology collection.

Main Outcome and Measures

Results of clinical evaluation, multimodal retinal imaging, histopathology, and molecular genetic testing in a case of nonsyndromic asymmetric RP using resources from the ocular pathology collection.

Results

Eyes from a deceased patient in her 50s with nonsyndromic asymmetric RP found within the ocular pathology collection were studied. The patient was diagnosed with RP as an adolescent and presented in her 50s to the eye clinic with advanced RP, with the left eye affected much more severely than the right. The patient's phenotype was studied using in vivo imaging and postmortem histopathology to identify interocular differences in tissue degeneration. Extraction of blood-derived DNA and formalin-fixed paraffin-embedded DNA from autopsied eyes analyzed using next-generation sequencing did not yield a definitive molecular diagnosis nor significant tissue differences.

Conclusions and Relevance

This study demonstrates newly reported histopathological and molecular correlates in asymmetric RP. This report also highlights the relevance of studying previously seen patients and reevaluating their conditions using resources within the ocular pathology collection to gain further insight on their disease.

Serpiginous Intraretinal Lesions Associated With Familial Exudative Vitreoretinopathy

Familial exudative vitreoretinopathy (FEVR) is a rare inherited disorder affecting retinal angiogenesis that may present with a wide range of phenotypic characteristics. In this report, the authors describe an atypical presentation of FEVR in a healthy 9-year-old male with progressive decreased visual acuity in the left eye. Fundus examination showed an avascular retina in the temporal periphery bilaterally. The left eye also revealed serpiginous hypopigmented lesions in the superior quadrant, which showed intraretinal location on optical coherence tomography and hyperautofluorescence. Genetic testing revealed LRP5 mutation, confirming a diagnosis of FEVR. The serpiginous lesions represent an unusual finding associated with FEVR not previously described in the literature. [Ophthalmic Surg Lasers Imaging Retina. 2021;52:155-159.].

Retinoschisis and Norrie disease: a missing link

OBJECTIVE

Retinoschisis and Norrie disease are X-linked recessive retinal disorders caused by mutations in RS1 and NDP genes respectively. Both are likely to be monogenic and no locus heterogeneity has been reported. However, there are reports showing overlapping features of Norrie disease and retinoschisis in a NDP knock-out mouse model and also the involvement of both the genes in retinoschisis patients. Yet, the exact molecular relationships between the two disorders have still not been understood. The study investigated the association between retinoschisin (RS1) and norrin (NDP) using in vitro and in silico approaches. Specific protein-protein interaction between RS1 and NDP was analyzed in human retina by co-immunoprecipitation assay and MALDI-TOF mass spectrometry. STRING database was used to explore the functional relationship.

RESULT

Co-immunoprecipitation demonstrated lack of a direct interaction between RS1 and NDP and was further substantiated by mass spectrometry. However, STRING revealed a potential indirect functional association between the two proteins. Progressively, our analyses indicate that FZD4 protein interactome via PLIN2 as well as the MAP kinase signaling pathway to be a likely link bridging the functional relationship between retinoschisis and Norrie disease.

X-Linked Retinoschisis and a Coats-Like Response in the Setting of Retinopathy of Prematurity

Purpose

This case report describes a unique case of a young patient with retinopathy of prematurity (ROP), a unilateral Coats-like response, and X-linked retinoschisis (XLRS).

Methods

A 9-year-old boy with a history of regressed ROP presented with a unilateral Coats-like response, subretinal exudation, and XLRS. Examination and imaging findings demonstrated a highly unique combination of bilateral retinoschisis and a dramatic unilateral Coats-like response with a large schisis cavity.

Results

Treatment with laser photocoagulation and anti-VEGF therapy led to resolution of the subretinal exudative changes.

Conclusions

This is the first published description to our knowledge of a patient with a Coats-like response, XLRS, and a history of regressed ROP with resolution after treatment.

SUBCLINICAL MACULAR CHANGES AND DISEASE LATERALITY IN PEDIATRIC COATS DISEASE DETERMINED BY QUANTITATIVE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

Optical coherence tomography angiography quantitative data in pediatric eyes with unilateral Coats disease found significant differences in vascular density and foveal avascular zone area between disease and fellow eyes that precede clinical signs.

Purpose:

To determine vascular change at the macula in both eyes in unilateral pediatric Coats disease using optical coherence tomography angiography.

Methods:

Retrospective case-series. Thirteen eyes of pediatric patients with a diagnosis of unilateral Coats disease of various stages were compared with 13 fellow eyes. Optical coherence tomography angiography images were acquired using the RTVue XR Avanti. Scans were analyzed with novel projection artifact removal software and improved segmentation. Vascular density and foveal avascular zone area were calculated.

Results:

Vascular density was significantly decreased in eyes with Coats disease in comparison with fellow eyes in both the superficial capillary plexus and deep capillary plexus (43.7 ± 4.7 vs. 45.9 ± 4.4 [P = 0.000] and 43.0 ± 6.3 vs. 50.3 ± 2.2 [P = 0.001], respectively). The difference was also significant for most sectors of the macula. Foveal avascular zone area was significantly larger in eyes with Coats disease in comparison with fellow eyes (0.29 ± 0.1 vs. 0.24 ± 0.09 [P = 0.003]). These significant differences appeared as early as Stage 2A, preceding clinical findings.

Conclusion:

The findings support the unilaterality of Coats disease and show that vascular changes on optical coherence tomography angiography precede clinical staging of the condition.

Two-year results of intravitreal injections of aflibercept in Coats' Disease; a case report

PURPOSE

To report long term results of treatment with intravitreal injections of aflibercept in a newly diagnosed case of Coats' disease.

CASE REPORT

An 18-year-old man presented to the Retina Clinic of our Hospital complaining of blurred vision in the right eye (OD) for the past 3 months. His past medical and ocular history were unremarkable. Best corrected visual acuity (BCVA) was 20/200 OD and 20/20 in the left eye. Fundoscopy in OD revealed extensive macular edema with a circinate ring of hard exudates in the posterior pole temporally to the macula. Optical coherence tomography (OCT) demonstrated macular edema with subretinal fluid. Peripheral telangiectasias and light bulb aneurysms in the inferior temporal arcade, as well as in the nasal far periphery were found in OD in fluorescein angiography (FA), confirming the diagnosis of stage 2B Coats' disease. The left eye was normal. The original therapeutic strategy proposed was anti-VEGF injections in OD followed by laser photocoagulation. However, the patient did not consent to laser treatment and was treated with aflibercept monotherapy with 8 monthly intravitreal injections of aflibercept followed by 6 injections every 2 months for a total of 14 injections over a period of 2 years. The BCVA in OD improved to 20/25 while OCT imaging revealed significant decrease in retinal thickness with resolution of macular edema and FA demonstrated prominent regression of aneurysms and leakage.

CONCLUSION

To our knowledge this is the first case treated with aflibercept monotherapy, suggesting the significant role of vascular endothelial growth factor (VEGF) in vascular permeability in Coats' and supporting the rationale that anti-VEGFs are a valuable therapeutic option for Coats' disease.

A novel c.287G>T NDP missense mutation in a Chinese family with Norrie disease

BACKGROUND

Norrie disease is a rare X-linked recessive disorder in affected males. The typical features are congenital blindness, progressive hearing impairment, and, in some cases, some degree of mental retardation, microphthalmia, microcornea, growth failure, and seizures. Norrie disease is caused by mutations in the Norrie disease pseudoglioma gene (NDP), which encodes the Norrin protein that plays a crucial role in vascular development, neural cell differentiation, and proliferation in the retina and cerebellum. The aim of the present study was to identify the genetic cause of the disease and the phenotypic characteristics of the patients in an affected Chinese family.

MATERIALS AND METHODS

A Chinese family with Norrie disease was studied, and clinical phenotypes of the proband were observed. With informed consent from the patients' family, blood samples from family members were collected, genomic DNA was extracted, and Sanger sequencing was performed to identify the disease-causing mutation.

RE

sults: The c.287 G > T mutation of NDP was identified by Sanger sequencing and resulted in p.Cys96Phe. The pathogenicity prediction was performed by MutationTaster, Polyphen-2, SIFT, and PROVEAN, all of which suggested that the mutation is disease-causing and may be responsible for the phenotypes of Norrie disease.

CONCLUSION

The c.287 G > T of NDP is a novel mutation responsible for Norrie disease in a Chinese family.

SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY ASSESSMENT OF FELLOW EYES IN COATS DISEASE

PURPOSE

To assess foveal and parafoveal vasculature at superficial capillary plexus (SCP), deep capillary plexus, and choriocapillaris using optical coherence tomography angiography in the fellow eyes of patients with Coats disease.

METHODS

Observational and prospective case series. Thirteen patients with unilateral Coats and 14 healthy age- and sex-matched controls were consecutively recruited at Manchester Royal Eye Hospital and the Department of Ophthalmology of San Raffaele Hospital. Both groups underwent complete ophthalmologic examination, including optical coherence tomography angiography (Topcon Corp) 3 mm × 3 mm scans. Images were imported into ImageJ software and binarized; foveal avascular zone area was manually outlined and vessel density analyzed in inner (foveal) and outer (parafoveal) areas of SCP, deep capillary plexus, and choriocapillaris.

RESULTS

Fellow eyes disclosed a significant increase in the foveal vessel density of SCP (P = 0.04); in particular, superior and temporal quadrants showed more marked alterations (P = 0.02 and 0.04, respectively). Analysis of foveal avascular zone area revealed a significant enlargement in the SCP (P = 0.04). No correlation was found between fellow eyes and the stage of affected eyes.

CONCLUSION

Fellow eyes of Coats patients carry quantitative foveal vascular alterations at SCP. These may represent markers of altered inner blood-retinal barrier, due to a bilateral defect in midcapillary angiogenesis.

Late re-activation of Coats disease

Purpose

Observation

Conclusion

Vitrectomy for a secondary epiretinal membrane following treatment of adult-onset Coats' disease

Purpose

To report a case of adult-onset Coats’ disease that had worsening of macular edema and progressive macular traction following cryotherapy and repeated intravitreal bevacizumab injections due to formation of a secondary epiretinal membrane which only improved following pars plana vitrectomy and membrane peeling.

Observations

A 35-year-old male presented with diminution of vision in his left eye and was found to have localized telangiectatic retinal vessels and aneurysmal dilatations with massive exudation and cystoid macular edema. He was diagnosed as adult-onset Coats’ disease and treated with cryotherapy and a concomitant intravitreal injection of 2.5 mg bevacizumab followed by 3 monthly intravitreal injections of 2.5 mg bevacizumab and a single injection of 4 mg triamcinolone acetonide. Partial obliteration of the telangiectatic vessels and aneurysmal dilatations with improvement in surrounding lipid and fluid exudate was achieved, however, this was associated with progressive worsening of macular edema and macular traction due to formation of an epiretinal membrane which only improved following vitrectomy and membrane peeling. Effect of therapy at each stage was evaluated using visual acuity testing, fundus examination, fundus fluorescein angiography, and optical coherence tomography.

Conclusion and Importance

A secondary epiretinal membrane can develop following treatment of adult-onset Coats’ disease and cause traction especially when combining cryotherapy with bevacizumab injections. Vitrectomy in such cases with membrane peeling may result in improvement of anatomical and functional outcomes.

Basal ganglia calcifications (Fahr's syndrome): related conditions and clinical features

Basal ganglia calcifications could be incidental findings up to 20% of asymptomatic patients undergoing CT or MRI scan. The presence of neuropsychiatric symptoms associated with bilateral basal ganglia calcifications (which could occur in other peculiar brain structures, such as dentate nuclei) identifies a clinical picture defined as Fahr's Disease. This denomination mainly refers to idiopathic forms in which no metabolic or other underlying causes are identified. Recently, mutations in four different genes (SLC20A2, PDGFRB, PDGFB, and XPR1) were identified, together with novel mutations in the Myogenic Regulating Glycosylase gene, causing the occurrence of movement disorders, cognitive decline, and psychiatric symptoms. On the other hand, secondary forms, also identified as Fahr's syndrome, have been associated with different conditions: endocrine abnormalities of PTH, such as hypoparathyroidism, other genetically determined conditions, brain infections, or toxic exposure. The underlying pathophysiology seems to be related to an abnormal calcium/phosphorus homeostasis and transportation and alteration of the blood-brain barrier.

Adult Coats' Disease, Dubin-Johnson Syndrome, and the Search for Targeted Therapies

Coats' disease is nonhereditary retinal vascular disorder characterized by telangiectatic retinal vessels with prominent aneurysmal changes and exudation. A conclusive etiology has not yet been determined. In this retrospective case report and literature review, a 64-year-old male with Dubin-Johnson syndrome presented with unilateral retinal vascular changes and exudation consistent with a diagnosis of adult Coats' disease. The authors conclude that patients with Dubin-Johnson syndrome carry mutations in a multidrug resistance associated protein (MRP). MRPs are also expressed in the retina, retinal pigment epithelium, and vascular endothelium, where they export toxins and metabolites, and may serve as a therapeutic target. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:318-321.].

Recent advances in the diagnosis and treatment of Coats' disease

PURPOSE

To review and summarize the recent progress in the diagnosis and treatment of Coats' disease.

METHODS

Literature was collected from Web of Science, Medline and Pubmed, through searching of these keywords: "Coats' disease", "diagnosis" and "treatment".

RESULTS

Coats' disease is characterized by idiopathic leaky retinal vascular telangiectasia and microvascular abnormalities often accompanied by intraretinal or subretinal exudation and retinal detachment. Neovascular glaucoma and phthisis bulbi often occur in advanced cases. Coats' disease has significant diversity in terms of its clinical presentation and morphology. Anti-VEGF therapy combined with laser photocoagulation for early Coats' disease and anti-VEGF therapy combined with minimally invasive vitrectomy for advanced Coats' disease can achieve good efficacy.

CONCLUSION

Early diagnosis and timely treatment based on clinical stage are critical to retaining the patient's visual function. Patients should be aware that close long-term follow-up is necessary.

The importance of biochemical and genetic findings in the diagnosis of atypical Norrie disease

BACKGROUND

Norrie disease (ND) is a rare X-linked disorder characterized by bilateral congenital blindness. ND is caused by a mutation in the Norrie disease pseudoglioma (NDP) gene, which encodes a 133-amino acid protein called norrin. Intragenic deletions including NDP and adjacent genes have been identified in ND patients with a more severe neurologic phenotype. We report the biochemical, molecular, clinical and radiological features of two unrelated affected males with a deletion including NDP and MAO genes.

METHODS

Biochemical and genetic analyses were performed to understand the atypical phenotype and radiological findings. Biogenic amines in cerebrospinal fluid (CSF) were measured by high-performance liquid chromatography. The coding exons of NDP gene were amplified by polymerase chain reaction. Multiplex ligation-dependent probe amplification and chromosomal microarray were carried out on both affected males. Computed tomography and magnetic resonance imaging were performed on the two patients.

RESULTS

In one patient, the serotonin and catecholamine metabolite levels in CSF were virtually undetectable. In both patients, genetic studies revealed microdeletions in the Xp11.3 region, involving the NDP, MAOA and MAOB genes. Radiological examination demonstrated brain and cerebellar atrophy.

CONCLUSIONS

We suggest that alterations caused by MAO deficit may remain during the first years of life. Clinical phenotype, biochemical findings and neuroimaging can guide the genetic study in patients with atypical ND and help us to a better understanding of this disease.

A Novel Pathogenic Variant in NDP Gene With Incomplete Penetrance Manifests as X-Linked Familial Exudative Vitreoretinopathy

Familial exudative vitreoretinopathy (FEVR) is a rare hereditary ocular disorder characterized by incomplete or abnormal development of peripheral retinal vasculature. The genes responsible for this disorder are associated with the wingless-related integration site (Wnt) signaling pathway, a critical pathway for the development of normal retinal vasculature. A pathogenic variant in any one of these genes may disrupt retinal vasculogenesis. Furthermore, the type and number of pathogenic variants may influence the severity of disease and clinical course. Here, the authors identify a novel pathogenic variant in the NDP gene, not previously described in the literature. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:120-124.].

Wnt Signaling in vascular eye diseases

The Wnt signaling pathway plays a pivotal role in vascular morphogenesis in various organs including the eye. Wnt ligands and receptors are key regulators of ocular angiogenesis both during the eye development and in vascular eye diseases. Wnt signaling participates in regulating multiple vascular beds in the eye including regression of the hyaloid vessels, and development of structured layers of vasculature in the retina. Loss-of-function mutations in Wnt signaling components cause rare genetic eye diseases in humans such as Norrie disease, and familial exudative vitreoretinopathy (FEVR) with defective ocular vasculature. On the other hand, experimental studies in more prevalent vascular eye diseases, such as wet age-related macular degeneration (AMD), diabetic retinopathy (DR), retinopathy of prematurity (ROP), and corneal neovascularization, suggest that aberrantly increased Wnt signaling is one of the causations for pathological ocular neovascularization, indicating the potential of modulating Wnt signaling to ameliorate pathological angiogenesis in eye diseases. This review recapitulates the key roles of the Wnt signaling pathway during ocular vascular development and in vascular eye diseases, and pharmaceutical approaches targeting the Wnt signaling as potential treatment options.

The clinical relevance of visualising the peripheral retina

Recent developments in imaging technologies now allow the documentation, qualitative and quantitative evaluation of peripheral retinal lesions. As wide field retinal imaging, capturing both the central and peripheral retina up to 200° eccentricity, is becoming readily available the question is: what is it that we gain by imaging the periphery? Based on accumulating evidence it is clear that findings in the periphery do not always associate to those observed in the posterior pole. However, the newly acquired information may provide useful clues to previously unrecognised disease features and may facilitate more accurate disease prognostication. In this review, we explore the anatomy and physiology of the peripheral retina, focusing on how it differs from the posterior pole, recount the history of peripheral retinal imaging, describe various peripheral retinal lesions and evaluate the overall relevance of peripheral retinal findings to different diseases.

Retinal detachments in the pediatric population

In this review, we present a concise summary of the more commonly seen types of retinal detachments (RDs) that one can encounter in pediatric patients. A spectrum of diseases from rhegmatogenous RD in Stickler syndrome, Marfan syndrome, and choroidal coloboma to exudative RD in Coats disease, to tractional RD in persistent fetal vasculature, and combined RDs in familial exudative vitreoretinopathy are described with the management pearls for each.

A 12-Year-Old Girl with Bilateral Coats Disease and ABCA4 Gene Mutation

A 12-year-old girl with bilateral stage 2B Coats disease was screened meticulously for a possible underlying systemic disease as she was female and the disease was bilateral. Full systemic workout turned out to be unremarkable. However, an ABCA4 gene mutation was found in the genetic analysis. NDP and TINF2 gene mutations were not present. She was successfully treated with a bilateral, single intravitreal injection of dexamethasone implant and a single session of indirect laser photocoagulation with a relatively good anatomic and functional result. To the best of our knowledge, the present case is the only reported case of Coats disease with an ABCA4 gene mutation.

Anti-VEGF for ROP and Pediatric Retinal Diseases

Vascular endothelial growth factor (VEGF) is an important mediator of the pathological neovascularization and vascular permeability of the eye. The increasing use of intravitreal therapies targeting VEGF has revolutionized the treatment of pediatric vitreoretinal diseases. In retinopathy of prematurity (ROP), the role of VEGF in pathogenesis has been well recognized and the use of anti-VEGF treatment in phase 2 ROP has demonstrated promising results, particularly in severe cases of posterior disease. This has made VEGF an established target in the treatment of pediatric retinal diseases known to have abnormal vascular activity. However, questions remain about late systemic and neurodevelopmental effects after anti-VEGF therapy for children because intravitreal injection of anti-VEGF may result in systemic circulation of anti-VEGF agent and a corresponding suppression of systemic VEGF. We do not currently know whether the short-term suppression of systemic VEGF affects long-term neurodevelopmental outcomes because VEGF is a vital supporting factor during neurodevelopment. This review article focuses on the evidence for the use of anti-VEGF treatment in certain pediatric ocular diseases, including ROP, Coats disease, and retinoblastoma. More extensive and prospective studies are warranted to further elucidate the role of anti-VEGF therapy in these diseases and illustrate how we can optimally use these agents in pediatric patients.

Cystoid edema, neovascularization and inflammatory processes in the murine Norrin-deficient retina

Mutations in the Norrin (NDP) gene cause severe developmental blood vessel defects in the retina leading to congenital blindness. In the retina of Ndph-knockout mice only the superficial capillary network develops. Here, a detailed characterization of this mouse model at late stages of the disease using in vivo retinal imaging revealed cystoid structures that closely resemble the ovoid cysts in the inner nuclear layer of the human retina with cystoid macular edema (CME). In human CME an involvement of Müller glia cells is hypothesized. In Ndph-knockout retinae we could demonstrate that activated Müller cells were located around and within these cystoid spaces. In addition, we observed extensive activation of retinal microglia and development of neovascularization. Furthermore, ex vivo analyses detected extravasation of monocytic cells suggesting a breakdown of the blood retina barrier. Thus, we could demonstrate that also in the developmental retinal vascular pathology present in the Ndph-knockout mouse inflammatory processes are active and may contribute to further retinal degeneration. This observation delivers a new perspective for curative treatments of retinal vasculopathies. Modulation of inflammatory responses might reduce the symptoms and improve visual acuity in these diseases.

LONG-TERM ANATOMICAL AND FUNCTIONAL OUTCOMES FOLLOWING VITRECTOMY FOR ADVANCED COATS DISEASE

PURPOSE

To assess the long-term anatomical and functional results of vitreoretinal surgery in patients with advanced Coats disease.

METHODS

Retrospective analysis of 23 patients who underwent 23-gauge pars plana vitrectomy combined with transscleral cryotherapy, laser photocoagulation, and intraocular tamponade between 2005 and 2014 and had a follow-up of at least 1 year. The primary outcomes were mean visual acuity and anatomical success.

RESULTS

The average age at the time of surgery was 8.7 ± 1.3 years (range, 2-18 years). The mean follow-up period was 55.2 ± 31 months (range, 12-120 months). In 16 eyes (70%), further treatment was not necessary. In the remaining 7 patients (30%), revision surgery with silicone oil tamponade was required. In 20 eyes (87%), the retina was reattached. At the final visit, 8 eyes (35%) had improved mean Snellen visual acuity from 20/1,000 at initial presentation to 20/160, 3 eyes (13%) showed stabilization, and 6 eyes (26%) had decline in visual acuity. No enucleation was necessary, and no progression to neovascular glaucoma was observed.

CONCLUSION

Pars plana vitrectomy combined with cryotherapy, laser photocoagulation, and intraocular tamponade could be an effective treatment option for advanced Coats disease. Despite surgery, disease-related complications remained high, but the main aim of management in these young patients is functional and anatomical stability.

INTRAVITREAL RANIBIZUMAB AS AN ADJUNCTIVE TREATMENT FOR COATS DISEASE (6-YEAR FOLLOW-UP)

PURPOSE

To evaluate the effectiveness of intravitreal ranibizumab in combination with laser photocoagulation in the management of Coats disease.

METHOD

Six intravitreal injections of 0.5 mg (0.05 mL) ranibizumab were performed, each 4 weeks apart. Correspondence to therapy was evaluated using visual acuity measurements and optical coherence tomography images. Six months after the initiation of treatment, laser photocoagulation was applied on the telangiectasias and on the surrounding ischemic areas, followed by a single intravitreal ranibizumab injection. Three months later, laser photocoagulation was repeated in purpose to prevent recurrence.

RESULTS

In the sixth month, no improvement in visual acuity was recorded, as thick circinate hard exudates still remained in the submacular space. Nevertheless, retinal detachment had completely subsided, and fluorescein angiography showed a significant decrease of leakage from the telangiectatic vessels. At the 12-month follow-up visit, an impressive improvement was recorded, with total absorption of the submacular exudate and visual acuity being 20/30. At the 20-month follow-up visit, his visual acuity was 20/20 and the retina was flat with no signs of macular edema or exudates. At the 6-year follow-up visit, the patient was absolutely stable.

DISCUSSION

Elevated vascular endothelial growth factor levels have been demonstrated in Coats disease. Anti-vascular endothelial growth factor agents assist to the decrease of vascular permeability of the capillary endothelial cells, thus increasing the efficiency of laser application.

Mutation spectrum of NDP, FZD4 and TSPAN12 genes in Indian patients with retinopathy of prematurity

AIM

Retinopathy of prematurity (ROP) is a vasoproliferative eye disease in preterm infants. Based on its phenotypic similarities with familial exudative vitreo retinopathy (FEVR), the present study was conducted to screen the Norrin signalling pathway genes (already been implicated in FEVR) for understanding their involvement among Indian patients with ROP.

METHODS

The study cohort consisted of patients with ROP (n=246) and controls (n=300) that included full term (n=110) and preterm babies devoid of ROP (n=190). Screening of the NDP, FZD4, TSPAN12 genes were accomplished by resequencing the entire coding and untranslated regions (UTR). The genotype data of the patients with ROP were analysed in the background of their clinical manifestations and further analysed in conjunction with other available data on these genes worldwide.

RESULTS

Two novel variants in intron 1 (IVS1 +16A>G) and 3'UTR (c.5 22T>C) along with a previously reported change in the 5'UTR (c.395_409del14bp) were observed in the NDP gene in three patients with ROP. Screening of the FZD4 revealed four heterozygous variants, p.(Pro33Ser), p.(Pro168Ser), p.(Ile192Ile) and p.(Ile360Val), a compound heterozygous (p.(Pro33Ser)/p.(Pro168Ser)) and a 3'UTR (c*G>T) variants in the study cohort. Variants p.(Pro33Ser) and p.(Pro168Ser) were found to be significantly associated with ROP. A heterozygous variant p.(Leu119Arg) in TSPAN12 gene was observed in a patient with threshold ROP. However, a formal genotype-phenotype correlation could not be established due to the low frequencies of the variant alleles in these genes.

CONCLUSIONS

This is a first study that revealed association of few variants in Norrin signalling genes among Indian patients with ROP that warrants further detailed investigation worldwide.

Refining Coats' disease by ultra-widefield imaging and optical coherence tomography angiography

PURPOSE

The purpose of our study was to describe ultra-widefield (UWF) imaging and optical coherence tomography angiography (OCT-A) findings in affected and fellow eyes of patients with Coats' disease.

METHODS

Consecutive patients affected by Coats' disease were prospectively recruited at the Department of Ophthalmology, San Raffaele Hospital, Milan, Italy in this cross-sectional, observational study. Patients underwent UWF color fundus photographs, UWF green autofluorescence, UWF fluorescein angiography (FA), optical coherence tomography (OCT), with 3 × 3 mm and 6 × 6 mm OCT-A scans of the macula. Images were qualitatively evaluated by two independent operators for the presence of pathology.

RESULTS

Eleven patients affected by Coats' disease (eight males, mean age 17.1 ± 6.7 years). Nine and two patients had a clinical diagnosis of unilateral and bilateral disease, respectively. Five eyes had macular fibrosis. All clinically affected eyes exhibited retinal pathology at UWF imaging with the temporal sector most involved followed by the inferior, nasal, superior and macula. In all eyes with macular fibrosis, OCT-A revealed replacement of the foveal avascular zone with coarse vessels suggestive of vascularized fibrosis and flow void area in the choriocapillaris due to a masking effect; type 3 neovascularization was seen in 75% of cases. Seven out of nine clinically unaffected fellow eyes showed retinal pathology at UWF FA with the temporal quadrant most involved.

CONCLUSION

We demonstrated that Coats' disease is a highly asymmetric bilateral disease and that UWF imaging is able to identify more retinal pathology than standard fundus imaging, thus guiding proper retinal photocoagulation. OCT-A allowed easy identification of type 3 neovascularization in a proportion of patients with macular fibrosis.

Long-term consequences of developmental vascular defects on retinal vessel homeostasis and function in a mouse model of Norrie disease

Loss of Norrin signalling due to mutations in the Norrie disease pseudoglioma gene causes severe vascular defects in the retina, leading to visual impairment and ultimately blindness. While the emphasis of experimental work so far was on the developmental period, we focus here on disease mechanisms that induce progression into severe adult disease. The goal of this study was the comprehensive analysis of the long-term effects of the absence of Norrin on vascular homeostasis and retinal function. In a mouse model of Norrie disease retinal vascular morphology and integrity were studied by means of in vivo angiography; the vascular constituents were assessed in detailed histological analyses using quantitative retinal morphometry. Finally, electroretinographic analyses were performed to assess the retinal function in adult Norrin deficient animals. We could show that the primary developmental defects not only persisted but developed into further vascular abnormalities and microangiopathies. In particular, the overall vessel homeostasis, the vascular integrity, and also the cellular constituents of the vascular wall were affected in the adult Norrin deficient retina. Moreover, functional analyses indicated to persistent hypoxia in the neural retina which was suggested as one of the major driving forces of disease progression. In summary, our data provide evidence that the key to adult Norrie disease are ongoing vascular modifications, driven by the persistent hypoxic conditions, which are ineffective to compensate for the primary Norrin-dependent defects.

Wnt signaling pathway in retinal vascularization

Wnt-signaling, a ubiquitous pathway that directs differentiation, cell polarity, and tissue specificity, has been implicated as an important gene-expression pathway in retinal development. An increasing body of evidence supports the importance of Wnt-signaling, and specifically, norrin-mediated Wnt-signaling in retinal development and retinal maintenance. Gene mutations affecting the Wnt-signaling pathways result in a variety of inherited vitreoretinopathies. Additionally, there is growing evidence that prematurity and associated retinopathy are associated with alterations in the Wnt-signaling pathways. Further investigations may allow for improved diagnoses, management, and therapies in the future.

TRANSCLERAL DRAINAGE OF SUBRETINAL FLUID, ANTI-VASCULAR ENDOTHELIAL GROWTH FACTOR, AND WIDE-FIELD IMAGING-GUIDED LASER IN COATS EXUDATIVE RETINAL DETACHMENT

PURPOSE

To evaluate the safety and efficacy of combined transscleral drainage of subretinal fluid (SRF) with intravitreal bevacizumab and laser photocoagulation in the management of advanced Coats disease (Stage 3) with exudative retinal detachment.

DESIGN

Retrospective interventional case series.

METHODS

Retrospective case review of eight eyes in eight children with advanced Coats disease manifested as total or subtotal retinal detachment. All eyes initially underwent surgical drainage of exudative SRF followed by intravitreal injection of bevacizumab and laser photocoagulation. Patients were subsequently followed up for up to 60 months.

RESULTS

In all eyes, after SRF drainage and administration of one to two intravitreal injections, SRF was completely eliminated. Patients required up to four sessions of laser photocoagulation. Retinal detachment consequently reduced with all patients showing total retinal reattachment and resolution of the subretinal exudates. At the last follow-up, no patient showed recurrent SRF and no ocular complications related to bevacizumab nor evidence of further disease progression were noted.

CONCLUSION

The authors present a new therapeutic approach that allows for the first time successful treatment of advanced cases of exudative retinal detachment in Coats disease without the need for vitrectomy. Transscleral drainage of SRF accompanied by anti-vascular endothelial growth factor injection and laser photocoagulation appears to be successful in halting progression of advanced Coats disease with exudative detachment and a less invasive approach when compared with conventional management.

Plasmalemma vesicle-associated protein: A crucial component of vascular homeostasis

Endothelial subcellular structures, including caveolae, fenestrae and transendothelial channels, are crucial for regulating microvascular function. Plasmalemma vesicle-associated protein (PLVAP) is an endothelial cell-specific protein that forms the stomatal and fenestral diaphragms of blood vessels and regulates basal permeability, leukocyte migration and angiogenesis. Loss of PLVAP in mice leads to premature mortality due to disrupted homeostasis. Evidence from previous studies suggested that PLVAP is involved in cancer, traumatic spinal cord injury, acute ischemic brain disease, transplant glomerulopathy, Norrie disease and diabetic retinopathy. Specifically, PLVAP expression has been demonstrated to be upregulated in these diseases, accompanied by pro-angiogenic or pro-inflammatory responses. Therefore, PLVAP is considered a novel therapeutic target, in addition to an endothelial cell marker. The present review summarizes the structure and functions of PLVAP, and its roles in pathophysiological processes.