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PubMed1990

3.8 million blinded by cataract each year: projections from the first epidemiological study of incidence of cataract blindness in India.

Data from a population based longitudinal study of randomly selected communities in Central India have for the first time provided direct estimates of age specific incidence of blindness from cataract. Person-time denominators have been used to compute age specific incidence rates (risk) of blindness from cataract for populations aged 35 and older. These age specific incidence measures have been applied to the 'population at risk' in each 5-year age class in order to estimate the total number of new cases of cataract blindness that occur in the country each year. The findings indicate that an estimated 3.8 million persons become blind from cataract each year in India (approximate 95% confidence limits: 3 to 4.5 million). The reasons why the estimates are considered as minima, and their implications concerning future national planning of ophthalmic services, are briefly discussed.

Adult↗

PubMed1993

Blindness in Africa: Zimbabwe schools for the blind survey.

An ophthalmic assessment survey of 430 students in Zimbabwe's two schools for the blind was conducted in 1988. Bilateral corneal opacity was found to be responsible for 75% of all blindness among institutionalised blind students. Thirteen per cent of the study patients could gain improved vision through either ocular surgical intervention or spectacle correction. Findings in this survey are similar to those from other schools for the blind elsewhere in Africa.

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↗

PubMed1995

Hereditary disease as a cause of childhood blindness: regional variation. Results of blind school studies undertaken in countries of Latin America, Asia and Africa.

There is evidence from developed countries that genetic disease is the major cause of childhood blindness. Little data are available from most developing and newly industrialised countries concerning the relative importance of hereditary diseases as a cause of childhood blindness. Children in schools for the blind in 13 countries of Africa, Latin America and Asia were examined between 1990 and 1994 using a standardised method The anatomical site of abnormality and underlying aetiology were analysed for children with a corrected acuity in the better eye of less than 6/60 (severe visual impairment and blindness, svi/BL). In these countries II-39% of svi/BL was attributed to genetic disease. Genetic diseases were responsible for a higher proportion of childhood visual loss in countries with higher levels of socio-economic development. An autosomal recessive mode of inheritance was reported in 22-52% of children with genetic disease. Retinal dystrophies were the commonest form of genetic eye disease (49-80%) in all countries apart from Thailand and the Philippines where cataract was the commonest (43.9%). The role of consanguinity, and opportunities for further research are discussed.

Africa↗

PubMed1975

Experimental production of elevated serum folate in dogs with intestinal blind loops. II. Nature of bacterially produced folate coenzymes in blind loop fluid.

Jejunal and ileal blind loops were constructed in separate groups of dogs and the folate coenzymes present in these loops were investigated. Although only those dogs with high blind loops had appreciably elevated folate levels active for Lactobacillus casei but not Streptococcus faecalis, every blind loop appeared to contain four folate compounds--5-formyltetrahydrofolic acid, 5-methyltetrahydrofolic acid, tetrahydrofolic acid and a compound tentatively identified as 5-formyltetrahydrofolic triglutamate. Why increased levels of 5-methyltetrahydrofolate alone are present in the serum of dogs with a high blind loop is discussed.

Animals↗

PubMed1992

Ultrastructural changes of the retina and the retinal pigment epithelium in Briard dogs with hereditary congenital night blindness and partial day blindness.

The offspring of two Briard dogs (brother and sister) with congenital, clinically stationary night blindness showed an aggravation of the disease with severe impairment of day vision in addition to night blindness. This ultrastructural study was performed on four such second generation puppies at the age of 4 months. The neuroretina and retinal pigment epithelium (RPE) from four locations were studied: the central area (immediately temporal to the optic disc); the centre of the tapetal area; the upper periphery (border of tapetal area); and the lower periphery (non-tapetal area). The RPE showed large inclusions, seemingly lipid in nature, mainly in the central and tapetal areas of the retina. Small, membrane bound, electron-dense inclusions were scattered in the RPE cytoplasm in all areas examined. The small inclusions were found to be less numerous in normal than in affected dogs and may be lysosomal in nature. Forty to fifty percent of the rod outer segments in the tapetal area showed disorientation of the disc membranes, whereas the corresponding figures were 20-40% in the central and lower peripheral areas and 6-25% in the upper peripheral area. No structural abnormalities were found in the rod inner segments or synaptic bodies. The cones were better preserved. The inner retina appeared normal. These electron microscopic findings seem to correspond to a previously published electrophysiologic evaluation, indicating a defective and delayed rod function (virtually no scotopic a- and b-waves), a better preserved cone function (photopic flicker responses present, although reduced) and impaired RPE activity (a prominent, slow negative potential of long latency at the site of the c-wave). It appears that these Briard dogs, showing structural changes of the rod outer segments in addition to pigment epithelial inclusions, mainly located in the posterior pole, comprise a pigment epitheliopathy and retinopathy morphologically different from other hereditary canine retinopathies that have been described earlier in the literature and different from animal models of congenital night blindness.

Animals↗

PubMed1991

Comparison of response rates to the angiotensin-converting enzyme inhibitor ramipril in mild-to-moderate hypertension in a double-blind, parallel-group study and an open single-blind study.

Appropriate clinical trial methodologies in general practice and suitable end points for dose-finding studies are discussed with reference to antihypertensive drugs in general and angiotensin-converting enzyme (ACE) inhibitors in particular. Two clinical studies were conducted with ramipril, a new nonsulfhydryl ACE inhibitor, to identify the minimum effective dose for the management of mild-to-moderate hypertension. Study 1 was a double-blind, parallel-group, randomized design with three treatment groups (placebo and 2.5 and 5 mg of ramipril), and study 2 was an open, single-blind design with individual dose titration from 2.5 to 5 mg of ramipril if the diastolic blood pressure (DBP) was greater than 90 mm Hg after 3 weeks. Response rates and DBP reductions with 2.5 mg of ramipril were similar in both studies, although overall response rates, DBP reductions, and side effect incidence appeared to be greater in the open, single-blind, dose-titration study. It is concluded that study methodology apparently influences efficacy and tolerability.

Angiotensin-Converting Enzyme Inhibitors↗

PubMedDate not supplied

Rod densitometry in night blindness: a review and two puzzling cases. Rod densitometry in night blindness.

Since the non-invasive technque of retinal densitometry became available in 1955, rhodopsin kinetics could be studied in vivo. It was obvious that with this new tool investigators focussed attention on the aetiology of night blindness in various diseases. A brief review about the clinical developments in the past two decades is given. Also three case-reports are presented, which suggest that in some cases of congenital stationary night blindness (CSNB) the night blindness might arise from the absence of rhodopsin. This is contrary to the standing opinion and present problems regarding the integrity of the retina.

Adolescent↗

PubMed1999

Acute onset of blindness during labor: report of a case of transient cortical blindness in association with HELLP syndrome.

The coincidence of HELLP syndrome and cortical blindness is an uncommon but very dramatic event, for the patient as well as the obstetrician. This report describes the first case of HELLP-syndrome-associated cortical blindness occuring suddenly in the third stage of labour. There were only modest correlates of cortical blindness in cerebral CT, MRI and angiography findings, but no signs of a posterior leucoencephalopathy syndrome. Mother and baby were discharged from hospital to outpatient care in good health on the 12th day.

Adult↗

PubMed1991

How "blind" are double-blind studies?

Psychopharmacological studies usually attempt to eliminate "nonspecific" influences on outcome by double-blind designs. In a randomized, double-blind comparison of alprazolam, imipramine, and placebo, the great majority of panic disorder patients (N = 59) and their physicians were able to rate accurately whether active drug or placebo had been given. Moreover, physicians could distinguish between the two types of active drugs. Inasmuch as correct rating was possible halfway through treatment, concerns about the internal validity of the double-blind strategy arise.

Adult↗

PubMed2002

How blind is double-blind? A study of fish oil versus placebo.

The distinctive aftertaste associated with fish oil preparations used in clinical trials of omega-3 fatty acids may weaken the double-blind. This double-blind pilot study was designed to examine whether normal subjects could correctly 'guess' if they were receiving capsules containing concentrated fish oil or capsules of pure olive oil. The informed consent was designed to give subjects ambiguous expectations about what oil they might be receiving to examine whether this would influence their guess. Despite a marked difference in taste experience, there was no significant difference in correct guesses between the two groups. The results suggest that altering subjects' expectations could further improve the validity of the double-blind.

Adult↗

PubMed1995

How "blind" are double-blind placebo-controlled trials of benzodiazepine hypnotics?

This study examined the accuracy of insomnia patients and their treating physicians in rating whether an active hypnotic drug or a placebo was given in treatment. Forty older adults with primary insomnia were randomly assigned to either an active (temazepam) or a placebo condition using a double-blind strategy. Ratings of treatment conditions were obtained at 1 week (early treatment), 4 weeks (midtreatment), and 8 weeks (late treatment). Patients were able to accurately discriminate (beyond chance levels) between the active and placebo medications at the early (76.9% accuracy) and late treatment assessment timepoints (78.1% accuracy), but not at midtreatment (51.5% accuracy). Therapists, however, were able to make accurate discriminations at the late treatment assessment timepoint only (80% accuracy); early (69.2% accuracy) and midtreatment (47.2% accuracy) ratings did not exceed chance levels. Patients who had used hypnotic drugs prior to this trial were more accurate in their judgments of treatment conditions than those without prior exposure. The findings raise an important issue about the internal validity of the double-blind strategy, which may in fact be only a single-blind procedure.

Aged↗

PubMed1988

Long day photoperiods and temperature of 20 degrees C induce spermatogenesis in blinded and non-blinded marbled newts during the period of testicular quiescence.

Adult male marbled newts (Triturus marmoratus) were collected at the end of the spermatogenesis period and exposed to different photoperiods (natural-daylength-simulated photoperiod, total darkness, 8L:16D, 12L:12D, 16L:8D, and continuous light) for 3 mo. Temperature was maintained at 20 degrees C. Two additional groups of newts were blinded and exposed to either the natural-simulated photoperiod and to 16 h of light per day respectively. Quantitative histologic studies on testicular development and germ cell volume per testis were performed. The newts captured in the field at the beginning (initial controls) or at the end of the experiments (final controls) were in the period of testicular quiescence. Newts kept in total darkness or exposed to a short photoperiod (8L:16D) showed germ cell development up to primary spermatocytes, whereas germ cell development in the newts exposed to long photoperiods (12L:12D or 16L:8D) progressed to elongated spermatids. The newts exposed either to intermediate photoperiods (natural-simulated photoperiod) or to constant light showed an intermediate degree of germ cell development (up to round spermatids). No significant differences between non-blinded and blinded animals were found. These results suggest that (1) mild temperature initiates testicular development in the period of testicular quiescence, (2) long photoperiods associated with mild temperatures produce spermatogenesis in this period, (3) complete darkness or constant light are less effective than some intermediate photoperiod, and (4) the effect of photoperiod on testicular function in newts is not related to ocular photoreception.

Animals↗

PubMed2003

Prospective, randomized, open-label, blinded-endpoint (PROBE) designed trials yield the same results as double-blind, placebo-controlled trials with respect to ABPM measurements.

OBJECTIVE: This meta-analysis aimed to determine whether ambulatory blood pressure monitoring (ABPM) results from double-blind, placebo-controlled (DBPC) and prospective, randomized, open-label, blinded-endpoint (PROBE) hypertension trials are statistically comparable. METHODS: Two DBPC and three PROBE parallel-group studies were selected from an angiotensin II receptor blocker clinical programme. These were fixed-dose studies involving similar mild to moderate hypertensive patient populations. All used SpaceLabs 90207 ABPM devices, and each comprised a 4-week placebo period and a 4-8-week treatment period. Data from patients receiving telmisartan 80 mg were used to compare the results of DBPC (126 patients) and PROBE (734 patients) trials. The analysis had approximately 87% power to show equivalence between the two design types in terms of ruling out differences of >or= 3 mmHg in SBP and >or= 2 mmHg in DBP. Office blood pressure was also compared. RESULTS: The change from baseline in mean 24-h ambulatory SBP was -12.2 mmHg in DBPC trials and -12.3 mmHg in PROBE trials, a rounded difference of 0.2 mmHg [95% confidence interval (CI): -1.8, 2.1]. The change from baseline in mean 24-h ambulatory DBP was -7.7 mmHg in DBPC trials versus -7.9 mmHg in PROBE trials, a difference of 0.2 mmHg (95% CI: -1.1, 1.5). Ambulatory pulse pressure results were identical. CONCLUSIONS: Thus, changes in mean 24-h ambulatory blood pressure from the DBPC and PROBE trials in this meta-analysis are statistically equivalent in terms of ruling out a difference of >or= 3 mmHg in SBP and >or= 2 mmHg in DBP. This supports the validity of the PROBE design in assessing antihypertensive efficacy based on blinded ABPM measurements.

Antihypertensive Agents↗

PubMed1980

Childhood blindness in Iceland. A study of legally blind and partially seeing children in Iceland 1978.

In 1978, a study was made of legally blind (corrected visual acuity 6/60 or less) and partially seeing (CVA 6/18 to 6/60) children under 15 years of age in Iceland. A total of 43 children were found, of whom 23 were legally blind and 20 partially seeing. The prevalence rates, expressed as the number per 100,000, children of similar age, 36.4 for legal blindness and 31.6 for partial sight. In all 43 children, the visual loss was attributable to heritable, congenital, or developmental defects. The most common causes of visual loss were optic nerve atrophy and cataracts. Other causes are listed and discussed. No cases of acquired visual loss were found. In addition to visual loss, other congenital birth defects were found in 24 of the children. CNS affection was found in 20 of the children, and of these, 15 were mentally retarded.

Abnormalities, Multiple↗

PubMed1981

Do the blind hear better? Investigations on auditory processing in congenital or early acquired blindness. I. Peripheral functions.

18 normally hearing blind students and 18 matched normal-sighted students were compared with regard to differential auditory sensitivity and acoustic reflex thresholds. Evaluation of interaural time differences for directional hearing and acoustic reflex thresholds showed no differences between the groups. The difference limen for intensity when interpreted by the SISI test, and the difference limen for frequency revealed a slightly optimizing trend in the blind group. However, differences missed statistical significance as to difference limen for intensity and, in the 3-orange, also as to difference limen for frequency. Any superior hearing of the blind was not mirrored by a corresponding superiority in peripheral supraliminal performance.

Adult↗

PubMed1988

Acute idiopathic blind spot enlargement. A big blind spot syndrome without optic disc edema.

We examined seven patients who had a syndrome of symptomatic monocular blind spot enlargement without optic disc edema. Two patients had previous blind spot enlargement that resolved over several months. The scotoma in each patients was absolute, measured 15 degrees to 20 degrees in diameter, had steep geographic margins, and extended to within 5 degrees to 10 degrees of fixation. Typically, patients had normal visual acuity, color vision, pupillary responses, and ophthalmoscopic findings. Photostress recovery, tested in two patients, was prolonged in the affected eye. Fluorescein angiography showed no abnormalities corresponding to the scotoma. Orbital computed tomographic scans in three patients and visual evoked responses in one patient were normal. Multifocal electroretinography, performed in two patients, showed loss of retinal waveforms in a large region surrounding the optic disc. Our findings suggest that retinal dysfunction produces this big blind spot syndrome, but we do not know its cause.

Acute Disease↗

PubMed2002

False predictions about the detectability of visual changes: the role of beliefs about attention, memory, and the continuity of attended objects in causing change blindness blindness.

Recently, a number of experiments have emphasized the degree to which subjects fail to detect large changes in visual scenes. This finding, referred to as "change blindness," is often considered surprising because many people have the intuition that such changes should be easy to detect. documented this intuition by showing that the majority of subjects believe they would notice changes that are actually very rarely detected. Thus subjects exhibit a metacognitive error we refer to as "change blindness blindness." Here, we test whether CBB is caused by a misestimation of the perceptual experience associated with visual changes and show that it persists even when the pre- and postchange views are separated by long delays. In addition, subjects overestimate their change detection ability both when the relevant changes are illustrated by still pictures, and when they are illustrated using videos showing the changes occurring in real time. We conclude that CBB is a robust phenomenon that cannot be accounted for by failure to understand the specific perceptual experience associated with a change.

Adult↗