A survey of visual impairment and blindness in children attending four schools for the blind in Cambodia

A 12-year follow up survey of childhood blindness at schools for the blind in Cambodia

BACKGROUND

Cambodia is a low-income country in South East Asia with a population of 15.5 million people of whom 4.9 million (38%) are under the age of 16. The causes of childhood blindness in Cambodia have not been investigated since the first survey of schools for the blind done in 2009 by our group. Given the large demographic and economic shifts in Cambodia since 2009 it is important to determine if these causes have changed in order to ensure intervention programmes are appropriately targeted. The purpose of the present study is to investigate the prevalence of causes of childhood blindness at schools for the blind in Cambodia.

METHODS

Students between the ages of 5 and 16 years who were attending schools for the blind in Cambodia were examined by a consultant paediatric ophthalmologist and had clinical photographs taken. Distance visual acuity was measured using a logMAR tumbling E chart and the WHO definitions of blindness and severe visual impairment were used. The examining ophthalmologist recorded the anatomical site and aetiology of vision loss using the WHO Prevention of Blindness eye examination record for children. Collected data were compared to a previous survey from 2009.

RESULTS

Data from 73 students were included for analysis. The most common anatomical location of abnormality causing vision loss was the cornea (n = 20, 33.9%) followed by the lens and retina (n = 11, 18.64% each). Hereditary factors (n = 29, 49.15%) and childhood diseases (n = 27, 45.76%) were the most common aetiological causes of childhood blindness. The majority (71.19%) of childhood blindness was avoidable. The present study did not demonstrate 0a significant difference in the causes of childhood blindness compared to 2009.

CONCLUSIONS

Corneal pathologies continue to represent the most common cause of vision loss amongst the surveyed population and the majority of causes of childhood blindness continue to be avoidable. These findings will facilitate the development of evidence-based targeted interventional programmes in Cambodia.

Inherited Retinal Dystrophy in Southeastern United States: Characterization of South Carolina Patients and Comparative Literature Review

Inherited retinal dystrophies (IRDs) are a group of rare diseases involving more than 340 genes and a variety of clinical phenotypes that lead to significant visual impairment. The aim of this study is to evaluate the rates and genetic characteristics of IRDs in the southeastern region of the United States (US). A retrospective chart review was performed on 325 patients with a clinical diagnosis of retinal dystrophy. Data including presenting symptoms, visual acuity, retinal exam findings, imaging findings, and genetic test results were compiled and compared to national and international IRD cohorts. The known ethnic groups included White (64%), African American or Black (30%), Hispanic (3%), and Asian (2%). The most prevalent dystrophies identified clinically were non-syndromic retinitis pigmentosa (29.8%), Stargardt disease (8.3%), Usher syndrome (8.3%), cone-rod dystrophy (8.0%), cone dystrophy (4.9%), and Leber congenital amaurosis (4.3%). Of the 101 patients (31.1%) with genetic testing, 54 (53.5%) had causative genetic variants identified. The most common pathogenic genetic variants were USH2A (n = 11), ABCA4 (n = 8), CLN3 (n = 7), and CEP290 (n = 3). Our study provides initial information characterizing IRDs within the diverse population of the southeastern US, which differs from national and international genetic and diagnostic trends with a relatively high proportion of retinitis pigmentosa in our African American or Black population and a relatively high frequency of USH2A pathogenic variants.

A survey of visual impairment and blindness in children attending eight schools for the blind in Myanmar: An update

Purpose:

To determine the causes of visual impairment (VI) and blindness among children in schools for the blind in Myanmar; to identify the avoidable causes of VI and blindness; to provide spectacles, low-vision aids, and ophthalmic treatment where indicated; to provide an update of the 2007 survey performed and identify any major epidemiological changes.

Methods:

Two hundred and ninety children under 16 years of age from all eight schools for the blind in Myanmar were examined and the data entered into the World Health Organization Prevention of Blindness Examination Record for Childhood Blindness.

Results:

In total, 271 children (93.4%) were blind (visual acuity [VA] <3/60 in the better eye) and 15 (5.17%) had severe visual impairment (SVI = VA <6/60 to 3/60 in the better eye). Most children had whole globe as the major anatomical site of SVI or blindness (105, 36.6%). The cause was unknown in the majority of these (155, 54.0%). One hundred and twelve children had avoidable causes of blindness and SVI (39.0%). Forty children (13.9%) required an optical device and 10.1% required surgical or medical attention, with a potential for visual improvement through intervention in 3.48%.

Conclusion:

In all, 39.0% of children had potentially avoidable causes of SVI and blindness with cataracts and measles being the commonest causes. This follow-up survey performed after the first one completed in Myanmar in 2007 demonstrates a change in the major site of abnormality from the cornea to whole globe and a reduction in avoidable blindness but highlights the ongoing burden of measles.

Causes of vision loss at China's largest blind school during a period of significant economic growth: 2008-2016

PURPOSE

To investigate the different causes of vision loss and school-based treatment regimens at Quanzhou Blind School (QBS), China's largest blind school, in 2008 and 2016.

METHODS

In 2008, 144 students received comprehensive eye examinations along with a complete family and ophthalmic history; in 2016, 125 students were examined. Vision loss was categorized into visual impairment and blindness classifications based on WHO guidelines. The etiologies of impairment and blindness in 2008 were compared to those in 2016 using the Fisher exact test. The prevalence and type of visual aids were also analyzed during this period.

RESULTS

The leading cause of visual impairment significantly shifted from corneal scarring in 2008 to retinopathy of prematurity (ROP) in 2016 (P = 0.020). Congenital cataracts remained the leading cause of blindness in 2008 and 2016. In 2016 there was a significant increase in the use of visual aids, with 63.2% of students using them in 2016 compared to 8.3% in 2008 (P = 0.0001).

CONCLUSIONS

Between 2008 and 2016, the leading cause of visual impairment shifted from corneal scarring to ROP, while congenital cataracts remained the leading cause of blindness.

An Ophthalmic Targeted Exome Sequencing Panel as a Powerful Tool to Identify Causative Mutations in Patients Suspected of Hereditary Eye Diseases

Purpose

We evaluate the power of a next-generation sequencing-based ophthalmic targeted sequencing panel (NGS-based OTSP) as a genetics-testing tool for patients suspected of a wide range of hereditary eye diseases.

Methods

NGS-based OTSP encompasses 126 genes with identified mutations that account for the majority of Chinese families with hereditary eye diseases. A total of 568 probands suspected of having hereditary eye diseases underwent genetic testing by OTSP with targeted phenotype-driven analysis.

Results

NGS-based OTSP detected 329 potential pathogenic variants in 62 genes. These mutations might represent the genetic cause in 52% (293/568) of probands suspected of having hereditary eye diseases. Within the disease subgroups, the detection rates were 61% (124/202) for retinal degeneration disease, 53% (35/66) for eye tumors, 49% (53/108) for retinal vessel disease, 46% (13/28) for retinal detachment, 33% (19/58) for significant refractive error, 35% (16/46) for optic atrophy, 48% (11/23) for anterior segment dysgenesis, and 59% (22/37) for other hereditary eye diseases. These detection rates are comparable to those obtained in our previous study performed with whole exome sequencing. Mutations in the same gene were detected in different forms of hereditary eye diseases. The average turnaround time for OTSP is 30 days, and the average cost is 139 USD per patient.

Conclusions

NGS-based OTSP is a powerful tool for routine clinical genetic diagnostic testing in patients suspected of having hereditary eye diseases.

Translational Relevance

NGS-based OTSP can be used as a routine clinical test to improve the genetic counseling and medical care of patients suspected of having hereditary eye diseases.

Identification of novel mutations causing pediatric cataract in Bhutan, Cambodia, and Sri Lanka

BACKGROUND

Pediatric cataract is an important cause of blindness and visual impairment in children. A large proportion of pediatric cataracts are inherited, and many genes have been described for this heterogeneous Mendelian disease. Surveys of schools for the blind in Bhutan, Cambodia, and Sri Lanka have identified many children with this condition and we aimed to identify the genetic causes of inherited cataract in these populations.

METHODS

We screened, in parallel, 51 causative genes for inherited cataracts in 33 probands by Ampliseq enrichment and sequencing on an Ion Torrent PGM. Rare novel protein coding variants were assessed for segregation in family members, where possible, by Sanger sequencing.

RESULTS

We identified 24 rare (frequency <1% in public databases) or novel protein coding variants in 12 probands and confirmed segregation of variants with disease in the extended family where possible. Of these, six are predicted to be the cause of disease in the patient, with four other variants also highly likely to be pathogenic.

CONCLUSION

This study found that 20%-30% of patients in these countries have a mutation in a known cataract causing gene, which is considerably lower than the 60%-70% reported in Caucasian cohorts. This suggests that additional cataract genes remain to be discovered in this cohort of Asian pediatric cataract patients.

Characterizing the "POAGome": A bioinformatics-driven approach to primary open-angle glaucoma

Primary open-angle glaucoma (POAG) is a genetically, physiologically, and phenotypically complex neurodegenerative disorder. This study addressed the expanding collection of genes associated with POAG, referred to as the "POAGome." We used bioinformatics tools to perform an extensive, systematic literature search and compiled 542 genes with confirmed associations with POAG and its related phenotypes (normal tension glaucoma, ocular hypertension, juvenile open-angle glaucoma, and primary congenital glaucoma). The genes were classified according to their associated ocular tissues and phenotypes, and functional annotation and pathway analyses were subsequently performed. Our study reveals that no single molecular pathway can encompass the pathophysiology of POAG. The analyses suggested that inflammation and senescence may play pivotal roles in both the development and perpetuation of the retinal ganglion cell degeneration seen in POAG. The TGF-β signaling pathway was repeatedly implicated in our analyses, suggesting that it may be an important contributor to the manifestation of POAG in the anterior and posterior segments of the globe. We propose a molecular model of POAG revolving around TGF-β signaling, which incorporates the roles of inflammation and senescence in this disease. Finally, we highlight emerging molecular therapies that show promise for treating POAG.

Causes of Severe Visual Impairment and Blindness: Comparative Data From Bhutanese and Laotian Schools for the Blind

PURPOSE

To determine and compare the major causes of childhood blindness and severe visual impairment in Bhutan and Laos.

DESIGN

Independent cross-sectional surveys.

METHODS

This survey consists of 2 cross-sectional observational studies. The Bhutanese component was undertaken at the National Institute for Vision Impairment, the only dedicated school for the blind in Bhutan. The Laotian study was conducted at the National Ophthalmology Centre and Vientiane School for the Blind. Children younger than age 16 were invited to participate. A detailed history and examination were performed consistent with the World Health Organization Prevention of Blindness Eye Examination Record.

RESULTS

Of the 53 children examined in both studies, 30 were from Bhutan and 23 were from Laos. Forty percent of Bhutanese and 87.1% of Laotian children assessed were blind, with 26.7% and 4.3%, respectively, being severely visually impaired. Congenital causes of blindness were the most common, representing 45% and 43.5% of the Bhutanese and Laotian children, respectively. Anatomically, the primary site of blinding pathology differed between the cohorts. In Bhutan, the lens comprised 25%, with whole globe at 20% and retina at 15%, but in Laos, whole globe and cornea equally contributed at 30.4%, followed by retina at 17.4%. There was an observable difference in the rates of blindness/severe visual impairment due to measles, with no cases observed in the Bhutanese children but 20.7% of the total pathologies in the Laotian children attributable to congenital measles infection.

CONCLUSIONS

Consistent with other studies, there is a high rate of blinding disease, which may be prevented, treated, or ameliorated.

Causes of visual impairment in children seen at a university-based hospital low vision service in Brazil

PURPOSE

To evaluate the epidemiologic characteristics of patients 0-7 years of age with visual impairment registered at a university hospital low vision service in Brazil.

METHODS

The medical records of visually impaired patients were retrospectively reviewed for sociodemographic characteristics and ocular and associated deficiencies. In addition to biographical information, the following data were collected: ocular disorders, diagnosis, affected anatomic region, etiology, and avoidable or unavoidable causes.

RESULTS

A total of 229 patients were included, 65% of whom were referred from rural health centers. The mean age at first appointment was 39.4 months. Associated nonophthalmic disorders were present in 47% of patients. The most prevalent disorders were congenital cataract (14%), toxoplasmosis (14%), and congenital glaucoma (13%). The most commonly affected anatomic regions were the retina (18%) and lens (15%); 33% had a normal-appearing globe. Using World Health Organization classifications, the most prevalent underlying etiologies were undetermined (43%), perinatal/neonatal factors (22%), and intrauterine factors (20%). Avoidable causes were found in 64% of the children.

CONCLUSIONS

The three leading causes of infant blindness in our patient cohort were congenital cataract, toxoplasmosis, and congenital glaucoma. The most commonly affected anatomic regions were retina, lens, and normal-appearing globe. The percentage of avoidable causes of impairment was high and the mean age at first appointment was late.

Causes of severe visual impairment and blindness in children in the Republic of Suriname

Aims

To determine the causes of severe visual impairment and blindness (SVI/BL) in children in Suriname (Dutch Guyana) and to identify preventable and treatable causes.

Methods

4643 children under 16 years of age were recruited from two locations: 33 children attending the only school for the blind were examined and 4610 medical records were analysed at an eye clinic. Data have been collected using the WHO Prevention of Blindness Programme eye examination record for children.

Results

65 children were identified with SVI/BL, 58.5% were blind and 41.5% were severely visually impaired (SVI). The major anatomical site of SVI/BL was the retina in 33.8%, lens in 15.4% and normal appearing globe in 15.4%. The major underlying aetiology of SVI/BL was undetermined in 56.9% (mainly cataract and abnormality since birth) and perinatal factors 21.5% (mainly retinopathy of prematurity (ROP)). Avoidable causes of SVI/BL accounted for 40% of cases; 7.7% were preventable and 32.3% were treatable with cataracts and ROP the most common causes (15.4% and 12.3%, respectively).

Conclusions

More than a third of the SVI/BL causes are potentially avoidable, with childhood cataract and ROP the leading causes. Corneal scarring from vitamin A deficiency does not seem to be a continuing issue in Suriname.

An update on progress and the changing epidemiology of causes of childhood blindness worldwide

PURPOSE

To summarize the available data on pediatric blinding disease worldwide and to present current information on childhood blindness in the United States.

METHODS

A systematic search of world literature published since 1999 was conducted. Data also were solicited from each state school for the blind in the United States.

RESULTS

In developing countries, 7% to 31% of childhood blindness and visual impairment is avoidable, 10% to 58% is treatable, and 3% to 28% is preventable. Corneal opacification is the leading cause of blindness in Africa, but the rate has decreased significantly from 56% in 1999 to 28% in 2012. There is no national registry of the blind in the United States, and most schools for the blind do not maintain data regarding the cause of blindness in their students. From those schools that do have such information, the top three causes are cortical visual impairment, optic nerve hypoplasia, and retinopathy of prematurity, which have not changed in past 10 years.

CONCLUSIONS

There are marked regional differences in the causes of blindness in children, apparently based on socioeconomic factors that limit prevention and treatment schemes. In the United States, the 3 leading causes of childhood blindness appear to be cortical visual impairment, optic nerve hypoplasia, and retinopathy of prematurity; a national registry of the blind would allow accumulation of more complete and reliable data for accurate determination of the prevalence of each.

Perspective on ophthalmic support in countries of the developing world

There are over 300 million people living in the world today who are visually impaired and a further 45 million who are blind. The large majority (90%) of these people live in developing countries, and up to 75% of blindness are avoidable. With cataracts being the major cause of blindness and visual impairment, many ophthalmic aid programmes are aimed at alleviating the enormous burden caused by this readily treatable disease. Having said that, caution should be exercised that short surgical visits to remote rural areas that are not coordinated with local national eye care managers should be discouraged because they do little for the development of sustainable eye care programmes. With this in view, it has become imperative to design blindness prevention and ophthalmic support programmes that are workable, comprehensive, economical and sustainable.

The trend of retinopathy of prematurity in Malaysia from 1992 to 2001 based on a nationwide blind schools study

Retinopathy of prematurity (ROP) is one of the most important causes of childhood blindness worldwide. The trend of ROP in Malaysia was unclear because there was no national registry before 2002. The purpose of this study is to analyze ROP students of different ages in the schools for the blind in Malaysia in order to evaluate the trend of ROP from 1992 to 2001. Data were obtained from a previous survey of 24 blind schools. It was found that 78 students or 17.4% were blind/severely visual impaired as a result of ROP. There was a significant surge in the number of ROP students who were born in 1994 when the use of synthetic surfactants was first introduced in Malaysia; otherwise there was no increasing trend in the number of students with ROP. However, the percentage of ROP in total was increasing, which indicates that ROP is becoming a more important cause of childhood blindness in this country.

Homozygous mutations in PXDN cause congenital cataract, corneal opacity, and developmental glaucoma

Anterior segment dysgenesis describes a group of heterogeneous developmental disorders that affect the anterior chamber of the eye and are associated with an increased risk of glaucoma. Here, we report homozygous mutations in peroxidasin (PXDN) in two consanguineous Pakistani families with congenital cataract-microcornea with mild to moderate corneal opacity and in a consanguineous Cambodian family with developmental glaucoma and severe corneal opacification. These results highlight the diverse ocular phenotypes caused by PXDN mutations, which are likely due to differences in genetic background and environmental factors. Peroxidasin is an extracellular matrix-associated protein with peroxidase catalytic activity, and we confirmed localization of the protein to the cornea and lens epithelial layers. Our findings imply that peroxidasin is essential for normal development of the anterior chamber of the eye, where it may have a structural role in supporting cornea and lens architecture as well as an enzymatic role as an antioxidant enzyme in protecting the lens, trabecular meshwork, and cornea against oxidative damage.