Blindness and visual impairment in a region endemic for onchocerciasis in the Central African Republic

AIMS—A population based survey of blindness and visual impairment was conducted in the district of Bossangoa, Central African Republic.
Methods—A total of 48 communities were randomly selected, and 6086 people examined.
RESULTS—The prevalence of blindness (visual acuity in the better eye less than 3/60) was 2.2%, and visual impairment 3.0% (6/24 to 3/60 in the better eye). The major causes of blindness were onchocerciasis (73.1%), cataract (16.4%), trachoma (4.5%), and glaucoma (2.2%).
CONCLUSION—Around 95.5% of all blindness could potentially have been prevented or treated. Ivermectin mass distribution is hoped to prevent 50% of all forms of visual loss in the future.

     

Prevalence of blindness and cataract surgery in Nepal

BACKGROUND—A national eye care programme was launched in Nepal in the early 1980s. The impact of this programme on blindness and cataract surgery prevalence was evaluated in two geographic zones.
METHODS—People aged 45 years and older were sampled using a stratified cluster design. Within randomly selected clusters, door to door enumeration was followed by visual acuity measurement and eye examinations at conveniently located sites. The full survey was preceded by a pilot study where operational methods were refined and quality assurance measures carried out.
RESULTS—Of the 5112 enumerated individuals 90% were examined. Blindness, defined as presenting visual acuity less than 6/60 in both eyes, was found in 5.3% (95% CI 3.6, 6.8) of individuals examined, with cataract being the principal cause in at least one eye in 78% of cases. Considering both cataract operated and unoperated cataract blind cases, surgical coverage was approximately 42%.
CONCLUSION—The findings suggest that blindness prevalence may have decreased slightly from that estimated in a 1981 national survey, both overall and cataract related. Similarly, cataract surgical coverage may have increased somewhat. None of these changes, however, are at statistically significant levels. Accordingly, the blindness problem remains challengingly high.

Keywords: blindness prevalence, cataract blindness, aphakia/pseudophakia     

A clinic based survey of blindness and eye disease in Cambodia

AIMS—To survey the spectrum of eye disease presenting to rural eye clinics in Cambodia.
METHODS—A total of 1381 patients seen consecutively at 13 eye clinics were examined and the findings recorded.
RESULTS—231 (16.7%) were bilaterally blind (visual acuity <3/60 in both eyes); 263 (19%) were unilaterally blind, and 169 (12%) had low vision (visual acuity <6/18 in the better eye). Cataract was the commonest cause of visual loss in all three categories and was responsible respectively in 69%, 40%, and 55% of each group. Trachoma was diagnosed in 13% of patients. Thirty three of them needed lid surgery for trichiasis.
CONCLUSION—With the difficult practical and political situation in Cambodia there seems little prospect of making substantial inroads into the backlog of avoidable blindness in the near future.

     

Epidemic optic neuropathy in primary school children in Dar es Salaam, Tanzania

BACKGROUND—An epidemic of bilateral optic neuropathy is affecting large numbers of people aged between 10 and 40 in Dar es Salaam, the capital city of Tanzania. The disease is characterised by acute onset of bilateral visual impairment, bilateral impairment of colour vision, and a characteristic temporal pallor of the optic discs. The disease often occurs in association with peripheral neuropathy and sensorineural hearing loss. This report presents the first data on disease prevalence in adolescents, based on a rapid assessment of schoolchildren.
METHODS—Three schools in Dar es Salaam were visited and all children aged between 10 and 16 were screened for the disease.
RESULTS—The prevalence of bilateral optic neuropathy among the schoolchildren is estimated to be 1.0% (95% CI 0.5-1.4%). This suggests that 5000 children (95% CI 2600-7300) aged 10-16 in Dar es Salaam may have the disease.
CONCLUSION—The results of this rapid assessment indicate this epidemic is a major public health problem. The prevalence of the disease in the community is likely to be far higher than found in this survey because children with the disease may have withdrawn from school. As the disease predominantly affects young adults, resulting in impaired vision and hearing, the economic and social consequences are enormous.

Keywords: optic neuropathy; schoolchildren; Tanzania     

Diabetic retinopathy in people aged 70 years or older. The Oulu Eye Study

AIMS—To evaluate the presence and severity of diabetic retinopathy and the value of retinopathy screening in people aged 70 years or older.
METHODS—In a population based study on 500 of 560 eligible (89%) people aged 70 years or older, signs of diabetic retinopathy were evaluated through dilated pupils by an ophthalmologist using photographic and/or ophthalmoscopic methods.
RESULTS—23% of the study population (113/500) had diabetes mellitus. Signs of diabetic retinopathy were found in 24 people (21% of the diabetic population). Retinopathy changes were graded as mild to moderate non-proliferative retinopathy (NPDR) in 40 eyes (18 people), severe NPDR (preproliferative) in five eyes (four people), and proliferative in three eyes (two people). Preproliferative or proliferative changes were present in four people (3.5% of the diabetic population) and diabetic maculopathy was diagnosed in nine (8% of the diabetic population). Laser treatment was considered to be indicated in seven people for maculopathy, and in two for proliferative changes. In four people the visual acuity was reduced to a low vision level as a result of diabetic retinopathy.
CONCLUSION—In spite of the high prevalence of diabetes mellitus in the elderly population, the prevalence of vision threatening diabetic retinopathy, particularly proliferative retinopathy, is low. Ophthalmoscopically, reliable information on fundus changes could be obtained in 94%, but photographs were gradable in only 76% of the diabetic population. Therefore, the value of photographic screening for diabetic retinopathy in this age group is poor in comparison with younger age groups.

     

Long term clinical outcome of a randomised controlled trial of anterior chamber lenses after high volume intracapsular cataract surgery

BACKGROUND—Age related cataract remains the major cause of blindness throughout the world. In many countries, the majority of cataract surgery continues to be done by the intracapsular cataract extraction (ICCE) method. The results of a large randomised controlled trial of multiflex open loop anterior chamber intraocular lenses (ACIOL) were reported from a busy eye hospital in Nepal.
METHODS—There was a randomised controlled trial of 2000 people with bilateral cataract reducing vision to less than 6/36. Interventions were ICCE with an ACIOL compared with ICCE with aphakic spectacles (+11 dioptres). Participants were followed at discharge, 6 weeks, 1 year, and 11/2-5 years after surgery. Visual acuity and clinical outcome were measured. A poor outcome was defined as vision <6/60.
RESULTS—Visual outcome was comparable in the two groups. More of the control group experienced functional blindness due to loss of aphakic spectacles at 1 year. The majority of cases of poor outcome occurred in the first year after surgery. There was no indication of any lens related problems after 1 year.
CONCLUSION—Multiflex open loop anterior chamber lenses are safe for up to 1 year of follow up when used by experienced surgeons, and the available evidence of 2-5 years of follow up suggests that the complication rate is reasonably low. An ACIOL at the time of cataract surgery offers benefits over routine ICCE surgery with aphakic spectacle correction as it avoids the problem of replacing lost and broken spectacles.

     

Visual functioning and quality of life outcomes among cataract operated and unoperated blind populations in Nepal

BACKGROUND—Visual acuity and vision related quality of life outcomes in cataract surgery were evaluated in a population based survey in two geographic zones in Nepal.
METHODS—Case finding was based on random sampling using a stratified cluster design with door to door enumeration of people aged 45 years followed by eye examinations at village sites. All aphakics/pseudophakics, those with visual acuity less than 6/60 in either eye, and a sample of those with normal visual acuity were administered visual functioning (VF) and quality of life (QOL) questionnaires.
RESULTS—15% of the 159 cataract operated cases had presenting visual acuity 6/18 in both eyes, 38% with best corrected visual acuity. 21% were still blind with presenting visual acuity <6/60 in both eyes, 7% with best correction. On a 0-100 scale, mean VF and QOL scores were 87.2 and 93.9 respectively in normally sighted unoperated individuals, dropping to 15.6 and 29.5 for those severely blind (<3/60). Among the cataract operated, mean VF and QOL scores were 47.5 and 55.4, respectively. VF and QOL scores correlated with vision status at statistically significant levels (p <0.0001)
CONCLUSION—Cataract surgery outcomes, whether measured by traditional visual acuity or by patient reported VF/QOL, are at levels many would consider unacceptably low. It is apparent that in the quest to reduce cataract blindness much more attention must be given to improving surgery outcomes.

Keywords: cataract surgery; visual acuity; visual functioning; quality of life     

The contribution of low birth weight to severe vision loss in a geographically defined population

AIMS—To describe the birthweight specific rate of severe vision loss among babies born between 1 January 1984 and 31 December 1987 to mothers resident in a geographically defined area, to classify the causes of vision loss by time of origin, and to describe the associated sensory and motor impairments and disabilities.
METHODS—Cases were identified from a population register of children with early childhood impairment, which uses multiple sources of ascertainment. Further clinical information was retrieved from hospital records and by asking ophthalmologists caring for the children.
RESULTS—166 (1.25/1000 live births) children with severe vision loss diagnosed by the age of 5 years were identified. The rate among babies born weighing less than 1500 g at birth was 26 times higher than the rate for babies between 2500 g and 3499 g. These very low birthweight babies contribute 17.5% of all severely visually impaired children. Almost two thirds of children with severe vision loss have a lesion of prenatal origin. Other sensory or motor deficits are present in 69% of the children. Retinopathy of prematurity accounted for 5.4% of all visually impaired children and seven of the 166 children met the criteria for perinatal asphyxia.
CONCLUSIONS—Although the contribution made by babies with a low birth weight to overall severe vision loss in the community is small, many of these children have additional impairments and probably place considerable demands on health and educational services and families. Reduction in the frequency of vision problems in the preschool population as a whole is unlikely to occur until there are major advances in the understanding of the aetiology and prevention of eye conditions of genetic, prenatal, and developmental origin.

     

Trachoma in the Gambia

BACKGROUND—As part of the second National Survey of Blindness and Low Vision in the Gambia carried out in 1996, all survey participants were examined for signs of trachoma. The findings were compared with the results of the first survey in 1986, which used the same sampling strategy.
METHODS—A multistage stratified cluster random sample, with proportional probability sampling, was obtained. Stratification included settlement size (less than 400 residents, and 400 and more residents). All subjects were examined for trachoma using the simplified WHO grading system.
RESULTS—Of the sample of 14 110 people, 13 047 (92.5%) were examined. Active inflammatory trachoma (grade TF or TI) was found in 3.0% of all age groups and 5.9% of children aged 0-9 years old. Trichiasis was found in 3.3% and trachomatous corneal opacities in 0.9% of adults aged 30 and over. The prevalence of blinding trachomatous corneal opacities was 0.02%, compared with 0.10% 10 years previously.
CONCLUSION—Compared with a previous national survey undertaken in 1986, prevalence of active trachoma has fallen by 54%. There has been an 80% relative reduction in blinding trachomatous corneal opacities over the 10 year period.

Keywords: trachoma; corneal opacity; sample survey; Gambia     

Prevalence and causes of low vision and blindness in an urban population: The Chennai Glaucoma Study

Aim:

To evaluate the prevalence and causes of low vision and blindness in an urban south Indian population.

Settings and Design:

Population-based cross-sectional study. Exactly 3850 subjects aged 40 years and above from Chennai city were examined at a dedicated facility in the base hospital.

Materials and Methods:

All subjects had a complete ophthalmic examination that included best-corrected visual acuity. Low vision and blindness were defined using World Health Organization (WHO) criteria. The influence of age, gender, literacy, and occupation was assessed using multiple logistic regression.

Statistical Analysis:

Chi-square test, t-test, and multivariate analysis were used.

Results:

Of the 4800 enumerated subjects, 3850 subjects (1710 males, 2140 females) were examined (response rate, 80.2%). The prevalence of blindness was 0.85% (95% CI 0.6–1.1%) and was positively associated with age and illiteracy. Cataract was the leading cause (57.6%) and glaucoma was the second cause (16.7%) for blindness. The prevalence of low vision was 2.9% (95% CI 2.4–3.4%) and visual impairment (blindness + low vision) was 3.8% (95% CI 3.2–4.4%). The primary causes for low vision were refractive errors (68%) and cataract (22%).

Conclusions:

In this urban population based study, cataract was the leading cause for blindness and refractive error was the main reason for low vision.     

Increased expression of angiogenic growth factors in age-related maculopathy

AIMS/BACKGROUND—The late stages of age-related maculopathy (ARM), especially neovascular macular degeneration (ARMD), can severely affect central vision and are the main cause of blindness in the elderly in the Western world. It has been shown that angiogenic growth factors are present in neovascular membranes in ARMD. However, it is not known if angiogenic growth factors play a role in the onset of neovascularisation.
METHODS—In order to elucidate the involvement of angiogenic growth factors in the initiation of neovascularisation in early stages of ARM, the expression patterns of VEGF, TGF-β, b-FGF, and PDGF-AA on 18 human maculae with ARM, and on 11 control specimens were investigated immunohistochemically.
RESULTS—A significantly increased expression of VEGF (p=0.00001) and TGF-β (p=0.019) was found in the retinal pigment epithelium (RPE) of maculae with ARM compared with control maculae. Furthermore, an increased expression of VEGF and PDGF was found in the outer nuclear layer of maculae with ARM.
CONCLUSION—These results demonstrate an increased expression of VEGF in the RPE, and in the outer nuclear layer in maculae with ARM, that could be involved in the pathogenesis of neovascular macular degeneration. Furthermore, enhanced TGF-β expression in the RPE cells of maculae with early stages of ARM was shown.

     

Normal S cone electroretinogram b-wave in Oguchi's disease

AIM—The short wavelength sensitive (S) cone electroretinograms (ERGs) were examined in two patients with Oguchi's disease to study S cone function.
METHODS—Ganzfeld colour flashes under bright white background illumination were used to elicit S cone, and mixed long (L) and middle (M) wavelength sensitive cone ERGs.
RESULTS—The S cone ERG b-wave was normal with short wavelength stimuli with normal L and M cone responses in both patients.
CONCLUSIONS—These ERG results indicate that the S cone system as well as the L and M cone system is not defective in Oguchi's disease, while the S cone responses are not detectable in the complete type of congenital stationary night blindness as reported previously. The results imply that there is a significant difference in the way the S cone system is affected in different forms of stationary night blindness, and that the S cone and rod do not share the same arrestin system.

     

Optical coherence tomography of pneumatic displacement of optic disc pit maculopathy

BACKGROUND—The authors have previously concluded that fluid from an optic disc pit creates an inner layer separation (ILS) of the retina. An outer layer detachment (OLD) centred on the macula is a secondary phenomenon that causes a dense central scotoma. Pneumatic displacement of the OLD effects an improvement in central vision. Pathology to confirm these conclusions is lacking. Intraretinal images obtained by optical coherence tomography (OCT), however, are confirmatory.
METHODS—Three patients with optic disc pit maculopathy were studied with stereoscopic photographs, visual fields, and OCT before and after intravitreal gas was injected to displace the central retinal elevation to below the inferior temporal vascular arcade.
RESULTS—Preoperatively, OCT demonstrated an ILS that connected with the optic disc pit. External to it was an OLD that centred on the fovea and did not connect with the optic disc pit. Pneumatic displacement of the OLD was accompanied by an improvement in central vision. Long term follow up indicates that the effect of displacement may be temporary.
CONCLUSION—OCT confirmed the two layer structure of optic disc pit maculopathy and that the improvement in central vision after pneumatic displacement coincides with a reattachment of the OLD in the macula. It also supports the hypothesis that the ILS, which persists, provides a conduit for the continuous flow of fluid from the pit to the displaced retinal elevation.

Keywords: optical coherence tomography; optic disc pit maculopathy; intraocular gas; retinoschisis     

BD8 certification of visually impaired people

BACKGROUND—There is debate as to the completeness of the blind and partial sight registers in England and Wales. The purpose of this study was to estimate the proportion of eligible visually impaired people attending the hospital eye service who have a BD8 certificate and to identify factors associated with not being certified.
METHODS—Cross sectional survey of patients attending outpatients by medical record review analysed by multiple logistic regression.
RESULTS—51% (43%, 58%) of patients identified as eligible for registration did not have a BD8 certificate. The severity of visual impairment and the main diagnosis in terms of requirements for treatment, permanence of visual loss, and visual field loss were independently associated with non-certification. A partially sighted patient is estimated to be three times more likely to not have a BD8 certificate as a blind patient of similar diagnosis (adj OR: 3.4 (95% CI: 1.7, 6.8)). A patient whose impairment is due to abnormal visual fields is estimated to be greater than three times more likely to be non-certified than one with low visual acuity of similar severity and cause (adj OR: 3.6 (95% CI: 1.0, 12.7)). People whose impairment is potentially reversible are estimated to be eight times ( 8.3 (2.2, 31.4)) more likely not to have a certificate compared with people who had permanent non-treatable visual loss; and in those with permanent visual loss, a requirement for ongoing treatment was found to be associated with a lower odds of certification.
CONCLUSIONS—These data strongly suggest that epidemiological data collected during registration are biased towards permanent, non-treatable causes of visual loss and those which affect central rather than peripheral vision. Certain subgroups of the visually impaired are likely to be at greater risk of non-certification. BD8 guidelines need to be simplified.

Keywords: registration; BD8 certification; data collection; visual impairment     

Diabetic retinopathy in Down's syndrome

AIM—To determine the prevalence of diabetic retinopathy in patients with Down's syndrome and diabetes mellitus.
METHOD—Nine patients with Down's syndrome and diabetes mellitus were assessed. Factors recorded included type and duration of diabetes, level of diabetic control, blood pressure, urinalysis, and results of ophthalmological examination.
RESULTS—The duration of diabetes ranged from 8 to 41 years (mean 17.6 years). All had satisfactory glycaemic control and blood pressure measurements on the low side of normal (mean 106.6/70 mm Hg). One patient had early background diabetic retinopathy. The remainder had no evidence of diabetic retinopathy.
CONCLUSION—The low prevalence of diabetic retinopathy in these Down's syndrome patients, despite the long duration, is an interesting finding. It suggests some inherent protective factor against the development of diabetic retinopathy in this patient subgroup.

Keywords: Down's syndrome; retinopathy; diabetes; hypertension     

Primary association of HLA-B51 with Behçet's disease in Ireland

AIMS/BACKGROUND—While a primary association of HLA-B51 with Behçet's disease (BD) in Japanese and Mediterranean patients supports an immunogenetic predisposition, this link is unclear in north western Europe. This study assessed HLA associations with BD, and HLA-B51 with certain clinical characteristics, in the Republic of Ireland, which has an ethnically homogeneous population.
METHODS—HLA-A, HLA-B, and HLA-DR typing was performed in 24 BD patients, conforming to International Study Group criteria, and in blood donors, as controls. Patient records were retrospectively reviewed and patients reassessed clinically.
RESULTS—A highly significant HLA-B51 association (corrected exact p value = 0.002, relative risk = 6.3) with BD was determined, despite a low B51 prevalence (25%) in patients. No other HLA type was associated. There was a significant B51 link with male sex in BD patients but no association with age at first manifestation/diagnosis, eye involvement, cyclosporin A therapy, or poor visual acuity was determined.
CONCLUSIONS—This study supports a HLA-B51 immunogenetic predisposition, similar to Japanese patients, in Irish BD in an ethnically homogeneous population in north western Europe. However, owing to a low prevalence of B51 positivity in BD patients in Ireland, a multifactorial pathogenesis is suggested.

     

Partial reversal of protan and tritan colour defects with inhaled oxygen in insulin dependent diabetic subjects

AIMS—Abnormalities in colour perception occur early in the development of diabetic retinopathy. Whether these changes can be influenced by increasing circulating oxygen saturation was studied in comparison with non-diabetic controls.
METHODS—Protan and tritan colour thresholds were measured using a computer graphics system in 37 insulin dependent diabetic subjects, with no or minimal background retinopathy, and 27 matched controls. Colour thresholds were performed after subjects inhaled either gaseous air or 100% oxygen for a minimum of 5 minutes.
RESULTS—Diabetic subjects had higher colour vision thresholds when inhaling air when compared with controls (protan (mean 3.93 (SEM 0.39), v 2.36 (0.16), p<0.0002) and tritan (8.15 (0.62) v 5.42 (0.31), p <0.002)). The colour vision thresholds observed in diabetic subjects inhaling air fell when they inhaled oxygen (protan (3.93 (0.39) v 3.57 (0.33), p <0.025) and tritan (8.15 (0.62) v 7.35 (0.59), p<0.005)). No fall in colour thresholds was seen in non-diabetic controls who inhaled oxygen.
CONCLUSION—A small improvement in the colour vision thresholds was observed using computer graphics in diabetic subjects, with minimal or no retinopathy, who inhaled oxygen. This study supports a hypothesis that reduced retinal oxygenation contributes to the colour vision defects in diabetes.

     

Improvements in clinical and functional vision and perceived visual disability after first and second eye cataract surgery

AIMS—To determine the improvements in clinical and functional vision and perceived visual disability after first and second eye cataract surgery.
METHODS—Clinical vision (monocular and binocular high and low contrast visual acuity, contrast sensitivity, and disability glare), functional vision (face identity and expression recognition, reading speed, word acuity, and mobility orientation), and perceived visual disability (Activities of Daily Vision Scale) were measured in 25 subjects before and after uncomplicated cataract surgery (10 first eye surgery and 15 second eye surgery) and in 10 age matched controls.
RESULTS—Significant improvements were found after surgery in clinical and functional vision and perceived visual disability. Greater improvements were found after first eye surgery than after second eye surgery. However, first eye surgery did not return all scores to age matched normal levels. There were significant improvements in several of the tests measured after second eye surgery, and all postoperative values were similar to those from age matched normals.
CONCLUSIONS—Significant improvements in clinical, functional, and perceived vision are obtained by cataract surgery. The improvements in objective measures of functional vision found in this study support previous findings of improvements in patients' perceived functional vision. In addition, these data provide support to the necessity of second eye surgery in some patients to improve certain aspects of visual function to age matched normal levels.

     

Visual outcome after paediatric cataract surgery: is age a major factor?

AIMS—To determine functional results after unilateral and bilateral cataract surgery in children with different aphakic optical correction.
METHODS—In this retrospective study, we evaluated visual acuity and binocular vision in 107 children who underwent cataract surgery during the 10 year period from 1985 to 1995. Aphakia was corrected by an intracapsular intraocular lens (IOL), spectacles or contact lenses.
RESULTS—Mean visual acuity was >20/40 (<0.3 log MAR) with normal binocular vision in 58 children over 7 months of age operated on for bilateral cataracts. Pseudophakic eyes regained visual acuity >20/63 (<0.5 log MAR) more often (90%) than aphakic eyes (46%) (p<0.001). Binocular vision was also achieved more often after IOL implantation (p<0.001). Visual outcome of early bilateral cataracts was less satisfactory in children with abnormal foveolar function. For 49 children who had surgery for unilateral cataracts, prognosis was poor when surgery was performed before the age of 7 months. For cataract surgery in older children (7 months) mean visual acuities were better with IOL implantation (p<0.05).
CONCLUSION—Cataract surgery with unilateral and bilateral IOL implantation can provide a beneficial effect on final visual outcome in children who are operated on before abnormal foveolar function develops.

Keywords: binocular vision; intraocular lens; paediatric cataract; visual outcome     

A new colour vision arrangement test to detect functional changes in diabetic macular oedema

AIM—A study was undertaken to investigate the correlation between colour discrimination tests and the presence of macular oedema in patients with type I diabetes to find a sensitive diagnostic tool for the detection of early functional changes.
METHODS—The study was performed in 39 type I diabetic patients, 10 with and 29 without macular oedema. The examination included biomicroscopy, fundus photography of the macula, videofluorescein angiography, the LogMAR visual acuity chart, Farnsworth-Lanthony desaturated D-15 test, and the new Mollon-Reffin "Minimalist" test for colour vision deficiencies version 6.0.
RESULTS—A highly significant correlation was found between the tritan value of the Mollon test and the presence of clinically significant macular oedema (p<0.0015), with a high sensitivity (88.9%) and specificity (93.3%). The DD-15 test was not significant (p=0.345) and showed low sensitivity for the presence of macular oedema (36%). All variables concerning the grading of macular oedema showed a highly significant association with the tritan values of the Mollon test (p<0.0001).
CONCLUSION—The results suggest that the Mollon-Reffin "Minimalist" test version 6.0 is the best colour discrimination test for detecting macular oedema, with higher specificity and sensitivity than the other methods used in the study.