Diagnosis and pathogenesis of congenital X-linked retinoschisis with optical coherence tomography

OCT Imaging in Infants

Optical coherence tomography (OCT) is widely applied in diagnosis and management of retina diseases particularly macular diseases in adult retina practices. However, it has been under-utilized in pediatric retinal diseases especially in neonates and infants. Utilization of OCT in primary macular diseases in this age group is also uncommon and is less reported. Challenges involved in image acquisition and limitations with available devices technique can explain the limited research and accurate data availability in the literature in this field. Purpose of this review article is to summarize the use of OCT and its importance in various infantile retinal pathologies such as vascular diseases, tumors, retinal dystrophies, and optic nerve pathologies with primary focus on neonates and infants, along with infant choroid. In addition, we also discuss about future directions including OCT angiography for infants.

X-linked juvenile retinoschisis: clinical diagnosis, genetic analysis, and molecular mechanisms

X-linked juvenile retinoschisis (XLRS, MIM 312700) is a common early onset macular degeneration in males characterized by mild to severe loss in visual acuity, splitting of retinal layers, and a reduction in the b-wave of the electroretinogram (ERG). The RS1 gene (MIM 300839) associated with the disease encodes retinoschisin, a 224 amino acid protein containing a discoidin domain as the major structural unit, an N-terminal cleavable signal sequence, and regions responsible for subunit oligomerization. Retinoschisin is secreted from retinal cells as a disulphide-linked homo-octameric complex which binds to the surface of photoreceptors and bipolar cells to help maintain the integrity of the retina. Over 190 disease-causing mutations in the RS1 gene are known with most mutations occurring as non-synonymous changes in the discoidin domain. Cell expression studies have shown that disease-associated missense mutations in the discoidin domain cause severe protein misfolding and retention in the endoplasmic reticulum, mutations in the signal sequence result in aberrant protein synthesis, and mutations in regions flanking the discoidin domain cause defective disulphide-linked subunit assembly, all of which produce a non-functional protein. Knockout mice deficient in retinoschisin have been generated and shown to display most of the characteristic features found in XLRS patients. Recombinant adeno-associated virus (rAAV) mediated delivery of the normal RS1 gene to the retina of young knockout mice result in long-term retinoschisin expression and rescue of retinal structure and function providing a 'proof of concept' that gene therapy may be an effective treatment for XLRS.

[X linked retinoschisis, unusual presentation: strabismus]

CASE REPORT

X linked retinoschisis is a recessively inherited degenerative retinopathy. We report two cases that debuted with an unusual presentation (strabismus) in early childhood (months). Both of them presented with vitreous veils in the retinal periphery. Mutation in the XLRS1 gene was detected in both cases.

DISCUSSION

X linked retinoschisis is one of the leading causes of macular degeneration in male children. Clinical features include a stellate foveal schisis, with or without peripheral retinoschisis. Clinical diagnosis is often difficult because of a high degree of phenotype variability. Furthermore, ERG and OCT may be normal in early stages of the disease. In our opinion, the XLRS1 gene mutation screening provides a powerful clinical tool for evaluating clinically ambiguous cases of X linked retinoschisis.

Surgical treatment for complications of congenital retinoschisis

This study examined the clinical features of complications of congenital retinoschisis and the clinical efficacy of vitreoretinal surgery in the treatment of these complications. The clinical efficacy of surgical treatments was retrospectively analyzed in 10 patients with congenital retinoschisis (10 eyes) complicated with rhegmatogenous retinal detachment (n=5), vitreous hemorrhage (n=2) and macula- involving schisis (n=1). All the patients suffered foveal and peripheral schisis. They were treated with scleral buckling (n=1) or vitrectomy (n=9). After the surgical treatment, the retina was reattached in patients with rhegmatogenous retinal detachment; the refractive media became transparent in those with vitreous hemorrhage; the visual acuity in 80% of patients was improved; no remarkable progression of schisis was found; no severe operative complications occurred. It was concluded that vitreoretinal surgery in the treatment of complications of congenital retinoschisis is safe and effective, and helps improve and maintain the visual function.

Optical imaging in vivo with a focus on paediatric disease: technical progress, current preclinical and clinical applications and future perspectives

To obtain information on the occurrence and location of molecular events as well as to track target-specific probes such as antibodies or peptides, drugs or even cells non-invasively over time, optical imaging (OI) technologies are increasingly applied. Although OI strongly contributes to the advances made in preclinical research, it is so far, with the exception of optical coherence tomography (OCT), only very sparingly applied in clinical settings. Nevertheless, as OI technologies evolve and improve continuously and represent relatively inexpensive and harmful methods, their implementation as clinical tools for the assessment of children disease is increasing. This review focuses on the current preclinical and clinical applications as well as on the future potential of OI in the clinical routine. Herein, we summarize the development of different fluorescence and bioluminescence imaging techniques for microscopic and macroscopic visualization of microstructures and biological processes. In addition, we discuss advantages and limitations of optical probes with distinct mechanisms of target-detection as well as of different bioluminescent reporter systems. Particular attention has been given to the use of near-infrared (NIR) fluorescent probes enabling observation of molecular events in deeper tissue.