Erosive vitreoretinopathy. A new clinical entity

The genetics and disease mechanisms of rhegmatogenous retinal detachment

Rhegmatogenous retinal detachment (RRD) is a sight threatening condition that warrants immediate surgical intervention. To date, 29 genes have been associated with monogenic disorders involving RRD. In addition, RRD can occur as a multifactorial disease through a combined effect of multiple genetic variants and non-genetic risk factors. In this review, we provide a comprehensive overview of the spectrum of hereditary disorders involving RRD. We discuss genotype-phenotype correlations of these monogenic disorders, and describe genetic variants associated with RRD through multifactorial inheritance. Furthermore, we evaluate our current understanding of the molecular disease mechanisms of RRD-associated genetic variants on collagen proteins, proteoglycan versican, and the TGF-β pathway. Finally, we review the role of genetics in patient management and prevention of RRD. We provide recommendations for genetic testing and prophylaxis of at-risk patients, and hypothesize on novel therapeutic approaches beyond surgical intervention.

Long-Term Outcomes and Risk Factors for Severe Vision Loss in Autosomal Dominant Neovascular Inflammatory Vitreoretinopathy (ADNIV)

Autosomal dominant neovascular inflammatory vitreoretinopathy (ADNIV) is a rare disorder characterized by uveitis, retinal neovascularization, and retinal degeneration. We sought to describe the course of treated and untreated ADNIV and to identify risk factors for severe vision loss.

DESIGN

Observational case series.

METHODS

Clinical data from ADNIV patients from 4 families seen from 1967 through 2019 at a single academic, tertiary referral center were reviewed. The main outcome measures were visual acuity at baseline and follow-up, as well as risk factors for vision loss.

RESULTS

A total of 130 eyes from 65 ADNIV patients (45 female, 20 male; mean age 40.8 years, range 6-77 years) were included. Mean best corrected visual acuity (BCVA) at presentation was LogMAR 0.59 (about Snellen 20/80). Longitudinal analysis included 84 eyes from 42 patients (31 female, 11 male), with mean follow-up of 17.3 years (range 2-43.6 years). Mean BCVA at last follow-up was LogMAR 1.48 (about Snellen 20/600). The disease accelerated in the fifth decade of life, during which the majority of eyes went from normal vision or mild vision loss to at least moderate vision loss (20/70 Snellen equivalent); 25 eyes from 16 patients (29.8%;) showed a steep trajectory of vision loss to no light perception. Tractional retinal detachment was the greatest risk factor for severe vision loss (BCVA <20/200) on multivariable analysis (P < .05).

CONCLUSIONS

Patients with ADNIV have a high lifetime risk of severe vision loss. Tractional retinal detachment is an important risk factor for poor vision.

Comparison of rigid versus foldable iris-fixed phakic intraocular lens implantation for high myopia: A systematic review and meta-analysis

BACKGROUND

This study aimed to assess the efficacy of rigid versus foldable iris-fixed phakic intraocular lens (PIOL) implantation in the treatment of high myopia.

METHODS

A systematic search based on electronic databases such as Pubmed, Embase, and Cochrane Library was conducted to identify relevant studies published up to January 11, 2019. The pooled odds ratios and weighted mean differences (WMDs) with corresponding 95% confidence intervals were calculated.

RESULTS

Eight comparative studies with 835 participants were included in this meta-analysis. The overall WMD showed statistical significance in terms of postoperative uncorrected distance visual acuity (UDVA), mean postoperative spherical equivalence (SE), and mean postoperative intraocular higher-order aberrations (HOA) (μm) for a 6-mm pupil, suggesting that foldable PIOL group showed significant improvement of high myopia, compared to rigid PIOL group. Besides, compared with rigid PIOL group, foldable PIOL group had beneficial effect on the proportion of eyes with central endothelial cell density (ECD) loss in patients with high myopia.

CONCLUSION

This meta-analysis provided the up-to-date evidence and found that foldable PIOL group had significant beneficial effect on UDVA, SE, HOA, contrast sensitivity, and ECD, except best spectacle-corrected visual acuity, and safety in the treatment of high myopia over rigid PIOL group.

VCAN Canonical Splice Site Mutation is Associated With Vitreoretinal Degeneration and Disrupts an MMP Proteolytic Site

Purpose

To gain insight into the pathophysiology of vitreoretinal degeneration, the clinical course of three family members with Versican Vitreoretinopathy (VVR) is described, and a canonical splice site mutation in the gene encoding for versican (VCAN) protein was biochemically analyzed.

Methods

A retrospective chart review, human eye histopathology, Sanger DNA sequencing, protein structural modeling, and in vitro proteolysis assays were performed.

Results

The proband (II:1), mother (I:2), and younger sibling (II:2) suffered retinal degeneration with foveal sparing and retinal detachments with proliferative vitreoretinopathy, features that were confirmed on histopathologic analysis. All affected members carried a heterozygous adenine to guanine variant (c.4004-2A>G) predicted to result in exon 8 skipping or the deletion of 13 amino acids at the beginning of the GAGβ chain (VCAN p.1335-1347). This deleted region corresponded to a putative MMP cleavage site, validated using fluorescence resonance energy transfer (FRET)-based proteolysis assays. Proteomic network analysis identified 10 interacting partners in the human vitreous and retina linked to retinal detachment and degeneration.

Conclusions

VVR causes significant ocular disease, including retinal detachment and retinal dystrophy. The intronic VCAN mutation removes an MMP cleavage site, which alters versican structure and results in abnormal vitreous modeling. Disruption of a versican protein network may underlie clinicopathologic disease features and point to targeted therapies.

The molecular basis of human retinal and vitreoretinal diseases

During the last two to three decades, a large body of work has revealed the molecular basis of many human disorders, including retinal and vitreoretinal degenerations and dysfunctions. Although belonging to the group of orphan diseases, they affect probably more than two million people worldwide. Most excitingly, treatment of a particular form of congenital retinal degeneration is now possible. A major advantage for treatment is the unique structure and accessibility of the eye and its different components, including the vitreous and retina. Knowledge of the many different eye diseases affecting retinal structure and function (night and colour blindness, retinitis pigmentosa, cone and cone rod dystrophies, photoreceptor dysfunctions, as well as vitreoretinal traits) is critical for future therapeutic development. We have attempted to present a comprehensive picture of these disorders, including biological, clinical, genetic and molecular information. The structural organization of the review leads the reader through non-syndromic and syndromic forms of (i) rod dominated diseases, (ii) cone dominated diseases, (iii) generalized retinal degenerations and (iv) vitreoretinal disorders, caused by mutations in more than 165 genes. Clinical variability and genetic heterogeneity have an important impact on genetic testing and counselling of affected families. As phenotypes do not always correlate with the respective genotypes, it is of utmost importance that clinicians, geneticists, counsellors, diagnostic laboratories and basic researchers understand the relationships between phenotypic manifestations and specific genes, as well as mutations and pathophysiologic mechanisms. We discuss future perspectives.

Mutational hot spot potential of a novel base pair mutation of the CSPG2 gene in a family with Wagner syndrome

OBJECTIVE

To report a 3-generation white family clinically diagnosed variably with Wagner, Stickler, and Jansen syndromes and screened for sequence variants in the COL2A1 and CSPG2 genes. Wagner syndrome is an autosomal dominant vitreoretinopathy with a predisposition to retinal detachment and cataracts. It has significant phenotypic overlap with allelic Jansen syndrome and ocular Stickler syndrome type 1. Sticker syndrome type 1 maps to chromosome 12q13.11-q13.2, with associated COL2A1 gene mutations. Wagner syndrome maps to chromosome 5q13-q14 and is associated with mutations in CSPG2 encoding versican, a proteoglycan present in human vitreous.

METHODS

Genomic DNA samples derived from venous blood were collected from all family members. Complete sequencing of COL2A1 was performed on a proband. Primers for polymerase chain reaction and sequencing were designed to cover all exon and intron-exon boundaries. Direct sequencing of CSPG2 was performed on all family member samples.

RESULTS

No detectable COL2A1 mutations were noted, making the diagnosis of ocular Stickler syndrome highly unlikely for this family. A unique base pair substitution (c.9265 + 1G>T) in intron 8 of the CSPG2 gene cosegregating with disease status was identified. This mutation occurred in a highly conserved previously reported splice site with a similar base pair substitution (G>A). Direct sequencing of this splice site mutation in 107 unrelated external controls revealed no variants, supporting the rarity of this base pair change and its causation in Wagner syndrome. This novel base pair substitution is thought to cause the deletion of exon 8 and formation of a truncated protein product.

CONCLUSION

Mutation screening of CSPG2 in autosomal dominant vitreoretinopathy families is important for accurate diagnosis.

CLINICAL RELEVANCE

This study underscores the importance of obtaining extensive pedigree information and comparative ophthalmologic clinical information, as the phenotypic findings may vary greatly among independent family members. The study also affirms the paradigm shift from diagnosis assignment based on eponyms to that based on gene mutation type.

Recent trends in the management of rhegmatogenous retinal detachment

It has been nearly a century since Jules Gonin performed the first intervention for rhegmatogenous retinal detachment, trans-scleral cautery, achieving successful outcomes in close to 50% of his cases. With the introduction of alternative surgical approaches in the last half-century, including Charles Schepens' scleral buckle technique and Robert Machemer's pars plana vitrectomy, the surgical success rates have risen to close to 90%. Nonetheless, despite dramatic progress in the success of reattachment surgeries, reasonable disagreement exists as to which approach (or combination of approaches) is the best form of surgical intervention for patients with rhegmatogenous retinal detachments. In this review, the authors summarize the current knowledge of retinal detachment, and examine emerging results from the first large scale, prospective, randomized, controlled clinical trials addressing the efficacy of these surgical approaches for retinal detachment, with the hope of identifying the most appropriate (evidence-based) therapeutic intervention for the treatment of rhegmatogenous retinal detachment.

Clinical characterisation and molecular analysis of Wagner syndrome

AIM

To detail the clinical findings in a British family with molecularly characterised Wagner syndrome.

BACKGROUND

Only in the last year has the specific genetic defect in Wagner syndrome been identified, and the background literature of the molecular genetics is outlined. Clinical and laboratory findings in a second case of Wagner syndrome are included to highlight difficulties that can be encountered when identifying pathogenic mutations for disorders arising in complex genes.

METHODS

Mutation screening was performed using PCR and RT-PCR.

RESULTS

A heterozygous mutation was found converting the donor splice site of exon 8 of the chondroitin sulphate proteoglycan 2 (CSPG2). This is the same mutation that has been reported in the original Wagner pedigree. The main clinical features of Wagner syndrome are vitreous syneresis, thickening and incomplete separation of the posterior hyaloid membrane, chorioretinal changes accompanied by subnormal electroretinographic responses, an ectopic fovea and early-onset cataract. A clinical feature present in this family, but previously undescribed, is anterior uveitis without formation of synechiae. Wagner syndrome has a progressive course, resulting in loss of vision even in the absence of retinal detachment.

CONCLUSION

On a background of considerable confusion regarding the distinction between Wagner syndrome and predominantly ocular Stickler syndrome, it is now apparent the that two conditions are both clinically and genetically distinct. This report summarises the clinical findings in Wagner syndrome and extends the phenotypic characteristics.

Snowflake vitreoretinal degeneration

PURPOSE

The ocular findings, systemic features, and genetic loci distinguishing known genetic causes of vitreoretinal degenerations were studied in the original Snowflake family.

DESIGN

Prospective, comparative study and molecular genetic investigation.

PARTICIPANTS

Members of the original snowflake vitreoretinal degeneration family.

METHODS

Clinical data were collected on 26 family members by history and examination. Thirteen of the 26 total family members underwent prospective examination. Linkage to known vitreoretinal degeneration loci (COL2A1, COL11A1, and the Wagner disease locus) was evaluated with short tandem repeat markers.

MAIN OUTCOME MEASURES

Ocular and systemic features of known vitreoretinal degenerations.

RESULTS

Six of the 13 prospectively examined subjects had snowflake vitreoretinal degeneration. Corneal guttae (4/5; 80%), early onset cataract (5/6; 83%), fibrillar vitreous degeneration (6/6; 100%), and peripheral retinal abnormalities (5/6; 83%), including minute crystallinelike deposits called snowflakes (4/6; 67%), were common. Retinal detachment was seen in 1 of 6 of these prospectively examined subjects (17%). A total of 14 affected subjects were identified within the family, and in 3 (21%), retinal detachment developed. Orofacial features, early-onset hearing loss, and arthritis typical of Stickler syndrome were absent. Linkage to known vitreoretinal degeneration loci was excluded.

CONCLUSIONS

The absence of vitreous gel in the retrolental space and presence of fibrillar vitreous degeneration were consistent with the vitreous structure reported for collagen 11A1 (COL11A1) but not collagen 2A1 (COL2A1) mutations. The absence of systemic features was characteristic of the vitreoretinopathies linked to chromosome 5q13 (Wagner disease and erosive vitreoretinopathy) and mutations in exon 2 of the COL2A1 gene. Snowflakes in the peripheral retina and the absence of nyctalopia, posterior chorioretinal atrophy, and tractional retinal detachment were inconsistent with the chromosome 5q13 vitreoretinopathies. The association of Fuchs' corneal endothelial dystrophy found in this family has not been reported previously in other vitreoretinal degenerations. These findings and the exclusion of known genetic loci suggest snowflake is a distinct vitreoretinal degeneration.

A novel hereditary developmental vitreoretinopathy with multiple ocular abnormalities localizing to a 5-cM region of chromosome 5q13-q14

BACKGROUND

To undertake a clinical and molecular analysis of a previously unpublished kindred with a phenotypically distinct vitreoretinopathy characterized by associated ocular developmental abnormalities.

DESIGN

Family genetic study.

PARTICIPANTS

A total of 23 members, both affected and unaffected, of 1 kindred with vitreoretinopathy.

METHOD

Individuals within the kindred were examined clinically and blood samples taken for DNA analysis. Genetic analysis was performed for the proximal region of chromosome 5q by means of polymerase chain reaction (PCR).

MAIN OUTCOME MEASURES

Detection of vitreoretinopathy and associated abnormalities.

RESULTS

This novel, hereditary vitreoretinopathy, showing the classic features of vitreous pathology and early-onset retinal detachments, was associated with a variety of ocular developmental abnormalities, including posterior embryotoxon, congenital glaucoma, iris hypoplasia, congenital cataract, ectopia lentis, microphthalmia, and persistent hyperplastic primary vitreous. There were no associated systemic features. Genetic mapping with markers from the proximal region of 5q13-q14 showed linkage to a 5-cM region between the markers D5S626 and D5S2103.

CONCLUSIONS

The 5-cM region is within that implicated in the etiology of both Wagner and erosive vitreoretinopathies. This suggests that this novel condition may be allelic, refines the genetic mapping for vitreoretinopathies that map to 5q13-q14, and implicates a gene important not only in vitreous production but also in early ocular development.

Clinical and molecular genetics of Stickler syndrome

Stickler syndrome is an autosomal dominant disorder with characteristic ophthalmological and orofacial features, deafness, and arthritis. Abnormalities of vitreous gel architecture are a pathognomonic feature, usually associated with high myopia which is congenital and non-progressive. There is a substantial risk of retinal detachment. Less common ophthalmological features include paravascular pigmented lattice degeneration and cataracts. Non-ocular features show great variation in expression. Children with Stickler syndrome typically have a flat midface with depressed nasal bridge, short nose, anteverted nares, and micrognathia. These features can become less pronounced with age. Midline clefting, if present, ranges in severity from a cleft of the soft palate to Pierre-Robin sequence. There is joint hypermobility which declines with age. Osteoarthritis develops typically in the third or fourth decade. Mild spondyloepiphyseal dysplasia is often apparent radiologically. Sensorineural deafness with high tone loss may be asymptomatic or mild. Occasional findings include slender extremities and long fingers. Stature and intellect are usually normal. Mitral valve prolapse was reported to be a common finding in one series but not in our experience. The majority of families with Stickler syndrome have mutations in the COL2A1 gene and show the characteristic type 1 vitreous phenotype. The remainder with the type 2 vitreous phenotype have mutations in COL11A1 or other loci yet to be identified. Mutations in COL11A2 can give rise to a syndrome with the systemic features of Stickler syndrome but no ophthalmological abnormality.

Refined genetic and physical localization of the Wagner disease (WGN1) locus and the genes CRTL1 and CSPG2 to a 2- to 2.5-cM region of chromosome 5q14.3

Wagner syndrome (WGN1; MIM 143200), an autosomal dominant vitreoretinopathy characterized by chorioretinal atrophy, cataract, and retinal detachment, is linked to 5q14.3. Other vitreoretinopathies without systemic stigmata, including erosive vitreoretinopathy, are also linked to this region and are likely to be allelic. Within the critical region lie genes encoding two extracellular macromolecules, link protein (CRTL1) and versican (CSPG2), which are important in binding hyaluronan, a significant component of the mammalian vitreous gel, and which therefore represent excellent candidates for Wagner syndrome. Genetic mapping presented here in two further families reduces the critical region to approximately 2 cM. Subsequent refinement of the physical map allows ordering of known polymorphic microsatellites and excludes CRTL1 as a likely candidate for the disorder. CSPG2 is shown to lie within the critical region; however, analysis of the complete coding region of the mature peptide reveals no clear evidence that it is the gene underlying WGN1.

Hereditary vitreopathy

Heterogeneity has long been recognised within the spectrum of inherited vitreo-retinal disease but the extent of the variation has been less easy to quantify. This has been compounded by the small size and numbers of pedigrees available for the study, and the phenotypic variation both within and between pedigrees. Formation abnormalities in the vitreous architecture have, in the past, been eclipsed by classifications based on general skeletal and morphological differences. Stickler syndrome is the commonest disorder within the spectrum of hereditary vitreous abnormalities and many of the recent published advances relate to this. Stickler syndrome has been subclassified on the basis of vitreo-retinal phenotype: type 1 families with a characteristic congenital vitreous anomaly show linkage without recombination to markers at the COL2A1 locus; type 2 families with different congenital vitreo-retinal phenotypes are not linked to COL2A1. A recent report identifies the COL11A2 mutation in a Dutch pedigree with systemic features of Stickler syndrome but without ocular involvement. Others have implicated COL11A1 in a type 2 Stickler syndrome pedigree with ocular abnormalities. Both COL11A1 and COL11A2 are expressed in cartilage, but on the basis of studies of bovine vitreous it is likely that only the alpha 1(XI) chain encoded by COL11A1 is present in vitreous. This would be consistent with the hypothesis that mutations in the genes encoding collagen XI can give rise to manifestations of Stickler syndrome, but of these, only mutations in COL11A1 will give the full syndrome including the vitreo-retinal features.

Wagner vitreoretinal degeneration. Follow-up of the original pedigree

PURPOSE

Wagner disease belongs to a heterogeneous group of hereditary vitreoretinal degenerations. The authors have observed complications of this disorder that have not been reported before and therefore re-examined Wagner's original pedigree to further delineate the spectrum of the associated findings and its prognosis.

METHODS

Sixty members of the family agreed to be examined. All had complete clinical eye examinations, 40 had dark adaptation studies as well as single-flash and Ganzfeld rod and cone electroretinography. Fluorescein angiograms were performed in selected patients.

RESULTS

Twenty-eight family members were affected. The most consistent finding was an empty vitreous cavity with avascular strands or veils. Chorioretinal atrophy and cataract increased with the patients' age and had occurred in all patients older than 45 years of age. Four patients had a history of a rhegmatogenous retinal detachment in one eye at a median age of 20 years. The authors observed peripheral tractional retinal detachments in 55% of eyes among patients older than 45 years. Glaucoma was present in ten eyes (18%), four of which showed neovascular glaucoma. Of all patients, 63% showed elevated rod and cone thresholds on dark adaptation, and 87% showed subnormal b-wave amplitudes of the rod- and of the cone system on the electroretinography.

CONCLUSIONS

Clinical expressivity of Wagner disease varies from unaffected carriers to bilateral blindness. Rhegmatogenous retinal detachment is observed infrequently, whereas peripheral traction retinal detachment, chorioretinal atrophy, and cataracts are present in most of the elderly affected individuals. Progression of the chorioretinal pathology is paralleled by electrophysiologic abnormalities.