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Biomedical subjects

C E Gilbert

Publications and source records attributed to C E Gilbert.

At least 37 records · Page 2Linked to original sources
PubMed1997

The importance of prenatal factors in childhood blindness in India.

The causes of visual loss in 1411 children attending schools for the blind in different geographical areas in India are described. Ninety-three percent (1318) of the children were severely visually impaired (SVI) or blind (i.e. corrected acuity in the better eye of <20/200 [<6/60]). In 60% of SVI/blind children vision loss was attributable to factors operating in the prenatal period, in 47% the prenatal factors were known and definite, and in 13% prenatal factors were the most probable causes. Hereditary retinal dystrophies and albinism were seen in 19% of SVI/blind children and 23% had congenital ocular anomalies. There were variations in the relative importance of different causes by state. The observed pattern of causes of visual loss is intermediate between those seen in industrialised countries and in the poorest developing countries. This suggests that strategies to combat childhood blindness in India need to address concurrently both preventable and treatable causes. The need for aetiological studies, particularly on anophthalmos and microphthalmos, is highlighted.

Abnormalities, Multiple↗
PubMed1995

Childhood blindness in India: causes in 1318 blind school students in nine states.

It is estimated that at least 200,000 children in India have severe visual impairment or blindness and approximately 15,000 are in schools for the blind. Although this represents a small percentage of the estimated 5 million blind in India, it is significant in terms of 'blind-years'. Strategies to combat childhood blindness require accurate data on the causes to allocate resources to appropriate preventive and curative services. Since socio-economic factors vary in different areas of this industrializing country data should be representative of the country as a whole. This is the first multi-state study to be undertaken in India using the Record for Children with Blindness and Low Vision from the World Health Organization/PBL Programme. A total of 1411 children in 22 schools from nine states in different geographical zones were examined by an ophthalmologist and optometrist. Of these, 1318 children were severely visually impaired or blind (SVI/BL). The major causes of SVI/BL in this study were: (1) corneal staphyloma, scar and phthisis bulbi (mainly attributable to vitamin A deficiency) in 26.4%; (2) microphthalmos, anophthalmos and coloboma in 20.7%; (3) retinal dystrophies and albinism in 19.3%; and (4) cataract, uncorrected aphakia and amblyopia in 12.3%. This mixed pattern of causes lies in an intermediate position between the patterns seen in developing countries and those seen in industrialised countries. The causes identified indicate the importance both of preventive public health strategies and of specialist paediatric ophthalmic and optical services in the management of childhood blindness in India.

Adolescent↗
PubMed1995

Childhood blindness due to vitamin A deficiency in India: regional variations.

OBJECTIVES: To investigate the importance of vitamin A deficiency as a cause of childhood blindness and severe visual impairment (SVI) in India. DESIGN AND SETTING: Cross sectional survey of children with visual acuity less than 6/60 in the better eye (SVI/blindness), attending 22 schools for the blind in nine states of India. MAIN OUTCOME MEASURE: Proportion of children with blindness or SVI from corneal scarring attributable to vitamin A deficiency. RESULTS: 245 of 1318 (18.6%) of children had SVI/blindness attributable to vitamin A deficiency. The proportion of SVI/blindness due to vitamin A deficiency ranged from 7.5% (7/93) in Kerala to 26.7% (27/101) in Madhya Pradesh. In Tamil Nadu, 7.5% (9/120) of children in the capital city blind school had SVI/blindness due to vitamin A deficiency, compared with 30.4% (51/168) in a blind school in a rural area of the same state. CONCLUSION: Overall, vitamin A deficiency is the single most important cause of childhood blindness and SVI in India. There are marked variations by state and also between urban and rural locations.

Adolescent↗
PubMed1995

Causes of childhood blindness in Sri Lanka: results from children attending six schools for the blind.

AIM: The survey aimed to identify the major treatable or preventable causes of visual loss in children attending blind schools in Sri Lanka so that appropriate control measures can be implemented. METHOD: A total of 226 children with blindness (BL) or severe visual impairment (SVI) attending six schools for the blind were examined and details recorded using the WHO standard reporting form. RESULTS: Cataract was responsible for 17% of BL/SVI and was the commonest 'avoidable' cause of childhood blindness. Bilateral microphthalmos accounted for one quarter of BL/SVI. Vitamin A deficiency was not a significant cause of visual morbidity. CONCLUSION: The pattern of childhood blindness seen in this study is typical of a growing number of south east Asian countries which are developing rapidly. Childhood cataract is a major avoidable cause that can benefit from future intervention strategies.

Adolescent↗
PubMed1995

Low vision in east African blind school students: need for optical low vision services.

AIMS: There is increasing awareness of the needs of children with low vision, particularly in developing countries where programmes of integrated education are being developed. However, appropriate low vision services are usually not available or affordable. The aims of this study were, firstly, to assess the need for spectacles and optical low vision devices in students with low vision in schools for the blind in Kenya and Uganda; secondly, to evaluate inexpensive locally produced low vision devices; and, finally, to evaluate simple methods of identifying those low vision students who could read N5 to N8 print after low vision assessment. METHODS: A total of 230 students were examined (51 school and 16 university students in Uganda and 163 students in Kenya, aged 5-22 years), 147 of whom had a visual acuity of less than 6/18 to perception of light in the better eye at presentation. After refraction seven of the 147 achieved 6/18 or better. Eighty two (58.6%) of the 140 students with low vision (corrected visual acuity in the better eye of less than 6/18 to light perception) had refractive errors of more than 2 dioptres in the better eye, and 38 (27.1%) had more than 2 dioptres of astigmatism. RESULTS: Forty six per cent of students with low vision (n = 64) could read N5-N8 print unaided or with spectacles, as could a further 33% (n = 46) with low vision devices. Low vision devices were indicated in a total of 50 students (35.7%). The locally manufactured devices could meet two thirds of the need. CONCLUSION: A corrected distance acuity of 1/60 or better had a sensitivity of 99.1% and a specificity of 56.7% in predicting the ability to discern N8 print or better. The ability to perform at least two of the three simple tests of functional vision had a sensitivity of 95.5% and a specificity of 63.3% in identifying the students able to discern N8 or better.

Adolescent↗
PubMed1995

Causes of childhood blindness in east Africa: results in 491 pupils attending 17 schools for the blind in Malawi, Kenya and Uganda.

Pupils attending 12 schools for the blind in Malawi, 3 schools in Kenya and 2 schools in Uganda were examined to determine the causes of severe visual impairment or blindness (visual acuity in the better eye of less than 6/60). A total of 491 pupils aged 3-22 years was examined. Visual acuity was measured in each eye using a Snellen E chart. The anatomical site of abnormality and underlying cause of visual loss were determined by clinical examination for each eye, and for the child. Information was recorded on a standard reporting form (the WHO/PBL Eye Examination Record for Children with Blindness and Low Vision). Data were analysed for those aged less than 16 years using a database which accompanies the form. Preventable and treatable causes were identified. 260 pupils aged 5-20 years were examined in Malawi, 163 pupils aged 3-19 years were examined in Kenya and 68 pupils aged 6-22 years were examined in Uganda. Of the 491 students included in the study 309 (62.9%) were blind (BL) and 69 (14.1%) were severely visually impaired (SVI). 244 were aged less than 16 years and had SVI/BL. In these 244 children 35.2% of visual loss was due to corneal pathology, 13.5% was due to cataract and 14.8% to diseases of the retina. Corneal pathology, attributed to vitamin A deficiency and measles infection in the majority, was responsible for proportionally more SVI/BL in students in Malawi than in Uganda or Kenya.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Causes of blindness and severe visual impairment in children in Chile.

Three hundred and eighteen of 421 children (76 per cent) registered in Chile's 10 schools for the blind were examined. 84 per cent of these had severe visual loss (severe visual impairment or blindness), which was attributable to hereditary factors in 29.6 per cent, intra-uterine factors in 8.2 per cent, perinatal factors in 22.5 per cent and childhood factors in 11.2 per cent. The aetiology could not be determined in 28.5 per cent. Retinopathy of prematurity (ROP) accounted for 17.6 per cent of all children with severe visual loss; analysis of data by age-group suggested that ROP is becoming an increasingly important cause of blindness. It is estimated that one-half of the children with severe visual loss in Chile have avoidable causes of blindness. The findings are discussed in the light of possible control strategies.

Blindness↗
PubMed1993

Lack of total independence of uncertainty factors (UFs): implications for the size of the total uncertainty factor.

This paper assesses the fundamental assumption that multiple uncertainty factors (UFs) are independent of each other and therefore may be combined through a multiplicative scheme. It is argued that a lack of independence is seen in several cases such as that between the interindividual and less-than-lifetime UFs with respect to an age component and results in an error in double counting of UFs. The paper proposes revised UF values based on the concept of the relationship of independent and interdependent UFs. This uncertainty factor revision is then applied to a large number of contaminants for which EPA either has or has proposed MCLs or DWELs.

Age Factors↗
PubMed1993

Causes of childhood blindness: results from west Africa, south India and Chile.

Using World Health Organization definitions of visual loss and a standardised methodology, 905 children were examined in Chile, West Africa and South India. Of these 806 (89%) suffered from blindness (BL) or severe visual impairment (SVI). Causes of SVI and BL were classified anatomically and aetiologically, and avoidable causes identified. In W. Africa (n = 284) the major anatomical cause of SVI/BL was corneal scar/phthisis bulbi (35.9%). Retinal disease accounted for 20.4%, cataract 15.5% and glaucoma 13.0%. Aetiologically 33.8% of SVI/BL was due to childhood factors and 21.1% to hereditary disease. In S. India (n = 305) the major anatomical cause of SVI/BL was corneal scar/phthisis bulbi (38.4%). Retinal disease accounted for 22.6%, cataract 7.4% and glaucoma 3%. Aetiologically 37.0% of SVI/BL was due to childhood factors and 29.8% to hereditary disease. In Chile (n = 217) the major anatomical cause of SVI/BL was retinal disease (47.0%). Cataract accounted for 9.2%, glaucoma 8.3% and 6.9% was due to corneal pathology. Aetiologically 30.4% of SVI/BL was due to hereditary factors, and 20.8% to perinatal factors of which four-fifths (16.6%) was due to retinopathy of prematurity. Avoidable conditions accounted for 70%, 47% and 54% of cases in W. Africa, S. India and Chile respectively.

Adolescent↗
PubMed1993

Visual loss in an onchocerciasis endemic community in Sierra Leone.

The visual acuities of 1625 individuals recruited to a community-based clinical trial of ivermectin in southern Sierra Leone were measured, and the prevalence of visual loss in this rural population where onchocerciasis is hyperendemic was determined. Ocular examination was performed before treatment to establish the cause of visual loss. Using WHO definitions, 1.3% were blind (less than 3/60 in both eyes), 4.3% were visually impaired (between 6/24 and 3/60 in the better eye), and a further 3.4% were uniocularly blind (less than 3/60 in one eye and better than 6/24 in the other). Cataract and onchocerciasis were the major causes of visual loss in this population. More than half of the ocular morbidity was preventable or treatable by public health measures or basic curative medicine. These findings are discussed in the light of the available health and eye care services.

Blindness↗
PubMed1993

Immunologic cross-reactivity in the pathogenesis of ocular onchocerciasis.

PURPOSE: Onchocerca volvulus, a filarial worm, is a major cause of infectious blindness and inflammatory eye disease. An autoimmune cause for ocular onchocerciasis has been suggested since the identification of a recombinant antigen of O. volvulus that shows immunologic cross-reactivity with a host ocular component of 44,000 M(r). The aim of this study was to establish the distribution of the cross-reactive antigens in both host tissues and the parasite, and to determine if significant autoantibody responses to the host antigen could be detected in infected persons. METHODS: The tissue and organ distribution of the 44,000 M(r) antigen was determined by immunocytochemistry and Western blot analysis. Human autoantibody responses to the ocular antigen were demonstrated by Western blot analysis using sera collected from persons with onchocerciasis, with and without posterior segment pathology, Bancroftian filariasis, and Europeans with no filarial infection. RESULTS: The tissue distribution of the 44,000 M(r) antigen correlates with the sites of pathology in onchocerciasis and antibody reactivity against this antigen could be detected in all persons with onchocerciasis and posterior segment pathology. The antigen is also recognized by sera from persons with Bancroftian filariasis, but not from normal persons. CONCLUSIONS: A role is proposed for immunologic cross-reactivity in the pathogenesis of onchocerciasis and it is suggested that intraocular presentation of the cross-reactive parasite antigen by microfilariae is essential for the development of disease.

Adult↗
PubMed1991

Effects of repeated doses of ivermectin on ocular onchocerciasis: community-based trial in Sierra Leone.

Ivermectin seems to be a safe and effective treatment for onchocerciasis when given in a single dose, but less is known about the effects of repeated doses. Also, there seem to be differences in its effectiveness in anterior and posterior segment ocular disease. The ocular effects of ivermectin were studied in 586 villagers who were taking part in a double-blind, placebo-controlled, randomised trial in Sierra Leone. Only those who had received four doses, with 6-month intervals, of ivermectin or placebo were eligible. The 296 ivermectin-treated subjects and the 272 who received placebo were comparable with respect to age, sex, Onchocerca infection, blindness, and visual impairment before treatment. After treatment, the ivermectin group had less anterior segment disease than the placebo group, with significantly lower prevalences of microfilariae in the anterior chamber and cornea, and punctate keratitis (all p less than 0.001), and iritis (p less than 0.05). There was no significant difference in the prevalence of sclerosing keratitis, optic atrophy, or chorioretinitis between the groups. Visual acuities tended to be better in the ivermectin group, but the difference was not significant. There was a small but significant (p less than 0.01) excess of vascular sheathing in the ivermectin group. These differences persisted when subjects who were blind or visually impaired at baseline were excluded from analysis. The long-term effects of ivermectin, particularly on posterior segment disease, need further evaluation. In the mean time, the mass distribution of ivermectin should be promoted for all communities with hyperendemic onchocerciasis at risk of anterior segment disease.

Adolescent↗
PubMed1991

Immunological crossreactivity between a cloned antigen of Onchocerca volvulus and a component of the retinal pigment epithelium.

Onchocerciasis (river blindness) is a major blinding disease in Africa, Central America, and South America. Loss of vision can be due to corneal change, optic atrophy, or chorioretinal disease. It has been suggested that autoimmunological reactions resulting from crossreactivity between parasite antigens and components of eye tissues contribute to development of ocular pathology. Using sera collected from onchocerciasis patients as a screening reagent, a cDNA clone (Ov39) has been isolated from a lambda gt11 expression library of Onchocerca volvulus. This antigen exhibits immunological crossreactivity with a component of retinal pigment epithelium cells (RPE). Antiserum raised against this recombinant peptide immunoprecipitates a 22,000 Mr antigen of adult O. volvulus and recognizes a 44,000 Mr component of bovine RPE by Western blotting. A 44,000 Mr antigen of cultured human RPE metabolically labeled with 35S-methionine can be immunoprecipitated with the same antiserum. An antigen of the same size is recognized by a rabbit antiserum raised against whole O. volvulus extract. Immunocytochemical studies on cryostat sections of the bovine eye using the antirecombinant sera localizes this antigen to the RPE.

Amino Acid Sequence↗
PubMed1991

Evidence of soil-pica behaviour and quantification of soil ingested.

A previously published report on soil ingestion in children, revealed evidence that one of the subjects, a 3.5-year-old female, displayed soil-pica behaviour. Soil ingestion estimates for this child ranged from approximately 5 to 7 g d-1 for seven of eight soil tracers employed. The present paper revealed that the soil-pica behaviour occurred only in the second of the two weeks of observation, during which daily soil ingestion rates ranged from 10 to 13 g d-1. Tracer recovery studies displayed acceptable precision (i.e. 100% less than +/- 30%) for six of the eight tracers during the soil-pica episode (week 2). Evaluation of the weekly soil ingestion values of the remaining 63 subjects indicated no convincing evidence of soil-pica behaviour in this group of children aged 1-4.

Child Behavior↗
PubMed1990

Preliminary adult soil ingestion estimates: results of a pilot study.

Six adults were evaluated for the extent to which they ingest soil. This study was originally part of a large childhood soil ingestion study and was used to validate part of the analytical methodology used in that larger study. The adult study followed the soil tracer methodology of the children's study. The principal findings of the adult study revealed that the four most reliable tracer elements based on recovery studies in a mass balance assessment [aluminum (Al), silicon (Si), yttrium (Y), and zirconium (Zr)] yielded the following mean daily adult soil ingestion estimations: Al (77 mg), Si (5 mg), Y (53 mg), and Zr (22 mg). The median daily soil ingestion estimations based on these same tracer elements were: Al (57 mg), Si (1 mg), Y (65 mg), and Zr (-4 mg). These findings represent the first published quantitative estimates of soil ingestion by adults.

Adult↗
PubMed1989

How much soil do young children ingest: an epidemiologic study.

Sixty-four children aged 1-4 years were evaluated for the extent to which they ingest soil. The study followed the soil tracer methodology of S. Binder, D. Sokal, and D. Maughan (1986, Arch. Environ. Health, 41, 341-345). However, the present study included a number of modifications from the Binder et al. study. The principal new features were (1) increasing the tracer elements from three to eight; (2) using a mass-balance approach so that the contribution of food and medicine ingestion would be considered; (3) extending the period of observation from 3 days to 8 days; and (4) validating the methodology by having adult volunteers ingest known amounts of soil in a mass-balance validation study. The principal findings reveal the following. (1) The adult study confirmed the validity of the tracer methodology to estimate soil ingestion. (2) Of the eight tracers employed in the adult study, only Al, Si, and Y provided sufficient recovery data that was directly acceptably stable and reliable. (3) If food ingestion determinations were taken into consideration, the median estimates of soil ingestion from the eight tracers ranged from a low of 9 mg/day (Y) to a high of 96 mg/day (V); the median values of Al, Si, and Y, the three most reliable tracers, ranged from 9 mg/day to 40 mg/day. (4) One child had soil ingestion values ranging from 5 to 8 g/day, depending on the tracer. (5) If food ingestion had not been considered, the estimates of soil ingestion would have increased about two- to sixfold, depending on the tracer with Ti and Y being most affected by food intake. (6) Since soil and dust samples did not significantly differ in their levels of tracer elements, no reliable differentiation between the contribution of ingestion of dust and soil could be made. (7) These findings are generally consistent with the previously reported findings of Binder et al. (1986) and P. Clausing, B. Brunekreff, and J.H. van Wijnen (1987, Int. Arch. Occup. Med., 59, 73) if these latter studies are corrected for ingestion of tracers in food and medicine. The findings also account for the apparent discrepancy between the estimates from Al and Si and estimates based on Ti in previous studies. Thus the elevated estimates of soil ingestion by Ti were substantially reduced when food ingestion is considered.

Adult↗