Visual impairment in Nordic children. V. X-linked juvenile retinoschisis

Prospective Evaluation of Patients With X-Linked Retinoschisis During 18 Months

Purpose

Prospective evaluation of patients with X-linked retinoschisis (XLRS).

Methods

Fifty-six males XLRS patients, age ≥7 years, had retinal structure and function tests performed every 6 months during an 18-month period.

Results

Best corrected visual acuity (BCVA) was abnormal (mean ± SD logMAR 0.57 ± 0.32 OD and 0.50 ± 0.27 OS), with weak correlation between visual acuity and age (R = -0.24, P = 0.0095). Mean cyst cavity volume (CCV) determined on optical coherence tomography showed weak correlation with age (R = -0.33, P = 0.0009) and no correlation with visual acuity. Subjects had modest reduction in mean kinetic and static perimetry results, reduced b-wave amplitude on electroretinography, abnormal reading speed results, and decreased visual function quality of life scores. Contrast sensitivity results were normal in 85 of 99 eyes tested. Most subjects had no meaningful change in BCVA during follow-up. Subjects who started carbonic anhydrase inhibitor (CAI) treatment at enrollment had improved BCVA (mean ± SD change 3.15 ± 7.8 ETDRS letters, with increase of ≥15 ETDRS letters at 8 of 110 visits [in 3 subjects]). There were no significant changes in other parameters tested.

Conclusions

Structural and functional results were stable during the 18-month follow-up period. Some patients starting CAI treatment at the baseline visit showed improvement in BCVA that was not correlated with changes in CCV. Natural history data such as these will be important for comparisons to the changes in measures of retinal structure and function following gene replacement therapy in patients with XLRS.

Genetic isolates in ophthalmic diseases

In recent years, noteworthy gains have been made in unravelling the genetic contribution to some complex ocular diseases, principally age-related macular degeneration. Yet, a relatively poor understanding of the genetic aetiology for many other heritable blinding diseases, such as glaucoma, keratoconus and myopia, remains. Genetic isolates, populations with varying degrees of geographical or cultural seclusion, provide an effective means for investigating the molecular mechanisms involved in human diseases. This is particularly true for rare diseases in which founded alleles can be rapidly driven to a high frequency due to restriction of gene flow in the population. Recent success in complex gene mapping has resulted from the widened linkage disequilibrium (LD) in the genome of genetically isolated populations. An improved understanding of the predisposing genetic risk factors allows for enhanced screening modalities and paves the foundations for the translation of genomic technology into the clinic. This review focuses on the role population isolates have had in the investigation of genes underlying complex eye diseases and discusses their likely usefulness given the expansion of large-scale case-control association studies.

A novel method of notification to profile childhood visual impairment in Scotland to meet the needs of children with visual impairment

The purpose of this study is to pilot a new notification system for children with visual impairment (VI) and describe the initial summary findings. A system of notification of children in Scotland with VI was established. Information concerning this system was distributed to professionals working with visually impaired children to forward to parents. Parents, teachers and health professionals were all encouraged to notify children with VI. 975 families with children with (VI) were notified and received information and support from Visual Impairment Scotland (VIS). For this review, the data from 850 parents were included in the analysis. The provision of a range of support services for parents and children with VI has led to a wide range of children being notified to VIS. The causes of VI can be recorded as well as other useful demographic information. The methods used could be applied across the range of low incidence childhood disabilities.

Visual impairment in children born at full term from 1972 through 1989 in Finland

OBJECTIVE

To investigate the incidence, prevalence, and causes of visual impairment in children born at full term and to determine conditions and factors associated with visual impairment.

DESIGN

Retrospective, cross-sectional, population-based study.

PARTICIPANTS

All visually impaired individuals from 0 to 17 years of age who were born at full term from 1972 through 1989 in Finland and recorded in the Finnish Register of Visual Impairment (n = 556) were eligible for this study.

METHODS

Data in the Finnish Register of Visual Impairment relating to 556 subjects were supplemented with data from hospital records and other national registers (Register of Births, Register of Congenital Malformations, Finnish Care Register, and Finnish Cancer Register). Data relating to the children born at full term were compared with Finnish perinatal and vital statistics and with data concerning children born prematurely. The chi-square test (Mantel-Haenszel) and stepwise logistic regression analysis were used in statistical analysis of the data.

MAIN OUTCOME MEASURES

Visual acuity, time of onset of visual impairment, ophthalmic diagnosis of visual impairment, systemic disease, multiple handicap, 5-minute Apgar score, prenatal disorders, perinatal disorders, disorders arising during infancy and childhood, and treatment.

RESULTS

Four hundred thirty-one of the 556 individuals with visual impairment (78%) had been born at full term. Visual impairment was predominantly associated with genetic (53%) and prenatal (34%) factors. Ocular malformations (34%), retinal diseases (31%), and neuro-ophthalmologic disorders (26%) were the main ophthalmic diagnoses. Optic nerve atrophy (20%) and congenital cataract (13%) were the most common single diagnoses. The occurrence of blindness, systemic disease, and multiple handicap was 40%, 43%, and 45%, respectively.

CONCLUSIONS

The incidence of visual impairment in children born at full term did not decline during the 2 decades covered by this study. The findings reflected the lack of treatment for genetic eye diseases. The results also confirmed an obvious need for further understanding of mechanisms underlying congenital anomalies of the human visual system.

X-linked retinoschisis: A clinical and molecular genetic review

X-linked retinoschisis is a leading cause of macular degeneration in male children. It is characterized by a high degree of clinical variability. Clinical features include a stellate foveal retinoschisis, with or without peripheral retinoschisis. The schisis occurs within the inner retina, primarily at the level of the nerve fiber layer. The disease-causing gene, X-linked retinoschisis 1, has recently been identified, and is expressed in photoreceptor and bipolar cells. This gene codes for retinoschisin, a secreted protein containing a discoidin domain which may be involved in cellular adhesion or cell-cell interactions. The identification of this gene allows for improved diagnosis and contributes to the understanding of this condition. Visual prognosis is variable, as X-linked retinoschisis exhibits a high degree of phenotypic variability. Although there is no treatment to halt the progressive maculopathy, clinical management is directed toward treatment of amblyopia and surgical correction of certain complications. X-linked retinoschisis is an important condition to study, both to improve the clinical management of this disorder, and to better understand retinal function and development. Herein, we review the clinical, histopathologic, and molecular genetic and treatment options of X-linked retinoschisis.

X-linked retinoschisis: report of a family with a rare deletion in the XLRS1 gene

PURPOSE

To describe the clinical features and identify the disease causing mutation in a family with X-linked retinoschisis.

DESIGN

Cohort study.

METHODS

Genealogical investigation and mutation screening of the XLRS1 gene were performed in a four generation family of Icelandic ancestry. Three affected family members were evaluated clinically over a 29-year period.

RESULTS

A rarely reported, four base pair deletion (375- 378 del AGAT) in exon 5 of the XLRS1 gene was found in all affected males. A high degree of intrafamilial variability was observed in the progression of the disorder over 29 years.

CONCLUSIONS

Identification of the disease causing mutation in this family allows for the diagnosis of individuals at risk for this inherited macular degeneration. Furthermore, the long-term follow-up of subjects with identical mutations helps to better characterize the highly variable clinical course of this disorder.

Visual impairment in Swedish children. II. Etiological factors

The analysis of etiological factors in a group of visually impaired children is of considerable importance when trying to find guidelines for possible preventive work. In this study we present etiological data on 2373 Swedish children. Data have been obtained by reviewing medical records on all known children with visual impairment throughout the country. In accordance with similar studies from industrialised countries, the group with prenatal etiology was the predominant, comprising 64% of the material. Within this group, half the patients had a disease of genetic origin. A total of 50% of all patients with prenatal etiology had an additional impairment, but in the group with diseases of genetic origin this proportion was smaller, only 40%. On the other hand, many children with additional impairments were found among those with an unspecified prenatal influence. Peri-/neonatal etiologies were found in 20% of the patients. In this group as many as 83% had additional impairments. This was even more pronounced among children delivered at term. The group with infantile/juvenile etiologies was small, 7%, with additional impairments in 66%. In 9% of all patients the etiology was classified as unknown. Among these, 80% had additional impairments. The visual impairment tended to be more pronounced, the later the disease was acquired. A male preponderance was seen in most etiological subgroups and in the material as a whole.

X linked retinoschisis

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