Chromium and manganese levels in biological samples of normal and night blindness children of age groups (3-7) and (8-12) years

This study was designed to compare the levels of chromium (Cr) and manganese (Mn) in scalp hair, blood, and urine of night blindness in children age ranged (3-7) and (8-12) years of both genders, comparing them to sex- and age-matched controls. A microwave-assisted wet acid digestion procedure, was developed as a sample pretreatment, for the determination of Cr and Mn in biological samples of night blindness children. The proposed method was validated by using conventional wet digestion and certified reference samples of hair, blood and urine. The digests of all biological samples were analyzed for Cr and Mn by electrothermal atomic absorption spectrometry. The results indicated significantly higher levels of Cr, whilst low level of Mn in the biological samples (blood and scalp hair) of male and female night blindness children, compared with control subjects of both genders. These data present guidance to clinicians and other professional investigating deficiency of Mn and excessive level of Cr in biological samples (scalp hair and blood) of night blindness children.

Evaluation of essential trace and toxic elements in biological samples of normal and night blindness children of age groups 3-7 and 8-12 years

The most common cause of blindness in developing countries is vitamin A deficiency. The World Health Organization estimates 13.8 million children to have some degree of visual loss related to vitamin A deficiency. The causes of night blindness in children are multifactorial, and particular consideration has been given to childhood nutritional deficiency, which is the most common problem found in underdeveloped countries. Such deficiency can result in physiological and pathological processes that in turn influence biological samples composition. Vitamin and mineral deficiency prevents more than two billion people from achieving their full intellectual and physical potential. This study was designed to compare the levels of Zn, Mg, Ca, K, Na, As, Cd, and Pb in scalp hair, blood, and urine of night blindness children age ranged 3-7 and 8-12 years of both genders, comparing them to sex- and age-matched controls. A microwave-assisted wet acid digestion procedure was developed as a sample pretreatment, for the determination of As, Ca, Cd, K, Pb, Mg, Na, and Zn in biological samples of night blindness children. The proposed method was validated by using conventional wet digestion and certified reference samples of hair, blood, and urine. The concentrations of trace and toxic elements were measured by atomic absorption spectrophotometer prior to microwave-assisted acid digestion. The results of this study showed that the mean values of As, Cd, Na, and Pb were significantly higher in scalp hair, blood, and urine samples of male and female night blindness children than in referents (p < 0.001), whereas the concentrations of Zn, Ca, K, and Mg were lower in the scalp hair and blood but higher in the urine samples of night blindness children. These data present guidance to clinicians and other professional investigating deficiency of essential mineral elements in biological samples (scalp hair and blood) of night blindness children.

Evaluation of status of zinc, copper, and iron levels in biological samples of normal children and children with night blindness with age groups of 3-7 and 8-12 years

The causes of night blindness in children are multifactorial, and particular consideration has been given to childhood nutritional deficiency, which is the most common problem found in underdeveloped countries. Such deficiency can result in physiological and pathological processes that in turn influence hair composition. This study was designed to compare the levels of zinc (Zn), copper (Cu), and iron (Fe) in scalp hair, blood, and urine of both genders of children with night blindness with age range of 3-7 and 8-12 years, comparing them to sex- and age-matched controls. A microwave-assisted wet acid digestion procedure was developed as a sample pretreatment, for the determination of zinc, copper, and iron in biological samples of children with night blindness. The proposed method was validated by using conventional wet digestion and certified reference samples of hair, blood, and urine. The digests of all biological samples were analyzed for Cu, Fe, and Zn by flame atomic absorption spectrometry using an air/acetylene flame. The results indicated significantly lower levels of Fe, Cu, and Zn in the biological samples (blood and scalp hair) of male and female children with night blindness, compared with control subjects of both genders. These data present guidance to clinicians and other professionals investigating the deficiency of essential trace metals in biological samples (scalp hair and blood) of children with night blindness.

Evaluation of status of cadmium, lead, and nickel levels in biological samples of normal and night blindness children of age groups 3-7 and 8-12 years

The causes of night blindness in children are multifactorial, and particular consideration has been given to childhood trace metals toxicity, which is the most common problem found in underdeveloped countries. This study was designed to compare the levels of cadmium (Cd), lead (Pb), and nickel (Ni) in scalp hair, blood, and urine of night blindness children age ranged 3-7 and 8-12 years of both genders, comparing them to sex- and age-matched controls. A microwave-assisted wet acid digestion procedure was developed as a sample pretreatment, for the determination of Cd, Pb, and Ni in biological samples of night blindness children. The proposed method was validated by using conventional wet digestion and certified reference samples of hair, blood, and urine. The digests of all biological samples were analyzed for Cd, Pb, and Ni by electrothermal atomic absorption spectrometry. The results indicated significantly higher levels of Cd, Pb, and Ni in the biological samples (blood, scalp hair, and urine) of male and female night blindness children, compared with control subjects of both genders. These data present guidance to clinicians and other professional investigating toxicity of trace metals in biological samples of night blindness children.

Supplementation with iron and riboflavin enhances dark adaptation response to vitamin A-fortified rice in iron-deficient, pregnant, nightblind Nepali women

BACKGROUND

Nightblindness affects 16-52% of pregnant women in areas of Nepal and in some cases persists after vitamin A treatment. Iron and riboflavin affect vitamin A utilization and photoreceptor function, respectively, and pilot data in the study population showed a high prevalence of iron and riboflavin deficiencies.

OBJECTIVE

The objective was to assess the effect of supplemental iron and riboflavin on pupillary threshold (PT) and plasma retinol in nightblind, pregnant Nepali women given vitamin A-fortified rice.

DESIGN

Nightblind pregnant women were randomly assigned to receive, 6 d/wk under supervision for 6 wk, a vitamin A-fortified rice curry dish providing 850 microg retinal activity equivalents/d with either a 30-mg Fe and 6-mg riboflavin (FeR + VA) capsule or a placebo control (VA only) capsule. Hemoglobin, erythrocyte riboflavin, and plasma ferritin and retinol were measured before and after the intervention. Dark adaptation was assessed by PT score.

RESULTS

Women who were iron deficient at baseline (n=38) had significantly greater improvement in PT score with iron and riboflavin supplementation than without (P=0.05). Iron and riboflavin supplements significantly reduced the prevalences of riboflavin deficiency (from 60% to 6%; P<0.0001), iron deficiency anemia (from 35% to 15%; P<0.007), and abnormal PT (from 87% to 30%; P<0.05) from baseline. Mean increases in erythrocyte riboflavin (P<0.0001) and plasma ferritin (P=0.01) were greater in the FeR + VA group than in the VA only group.

CONCLUSIONS

Iron deficiency may limit the efficacy of vitamin A to normalize dark adaptation in pregnant Nepali women. Further studies are needed to assess the effect of simultaneous delivery of iron and vitamin A for the treatment of nightblindness.

Improvement of scotopic electroretinograms and night blindness with recovery of serum zinc levels

BACKGROUND

We sought to determine the cause of reduced scotopic and photopic electroretinograms (ERGs) and night blindness in a 46-year-old man with liver dysfunction but no history of alcoholism.

CASE

A 46-year-old Japanese man with a complaint of visual difficulties in dim light for 1 month.

OBSERVATIONS

By electrophysiological investigation, the patient was found to have low levels of serum zinc and vitamin A on admission. The rod b wave was unrecordable, and the bright-flash ERGs were reduced, with the a wave > b wave. The amplitudes of the cone and 30-Hz flicker responses were also reduced, and their implicit times were prolonged. Three weeks after admission, the patient's serum zinc level recovered to normal levels, but his serum vitamin A level was still low. The symptoms of night blindness were gone, and the rod ERGs and single bright-flash responses were within normal limits. However, the cone ERGs and 30-Hz flicker responses were still depressed.

CONCLUSIONS

The recovery of scotopic function together with the recovery of zinc but not vitamin A levels suggests that the ERG changes were most likely related to low zinc levels.

Association between gestational night blindness and serum retinol in mother/newborn pairs in the city of Rio de Janeiro, Brazil

OBJECTIVE

Gestational night blindness (XN) is associated with increased risk of reproductive morbidity and mortality. This study investigated the prevalence of gestational XN among postpartum women treated in a public maternity hospital in the city of Rio de Janeiro, Brazil and evaluated its association with maternal and neonatal (cord blood) serum retinol concentrations.

METHODS

XN was evaluated retrospectively, using an interview according to guidelines of the World Health Organization, in 222 postpartum women (< or = 6 h after delivery) after singleton births who had low obstetric risk. Serum retinol concentrations were measured according to the modified Bessey method, with a cutoff point lower than 1.05 micromol/L for inadequate serum retinol concentration.

RESULTS

Prevalence of gestational XN was 18%, and inadequate maternal and cord blood serum retinol concentrations were found in 24.4% and 45.5% of samples, respectively. The results associated gestational XN with inadequate maternal serum retinol concentration (P = 0.000), and an association was observed between maternal and neonatal serum retinol concentrations (P = 0.000). A poor association was observed between maternal XN and serum levels of retinol in newborn children (P = 0.06).

CONCLUSIONS

The results suggest that prevalence of gestational XN and inadequate serum retinol concentration among postpartum women and newborns is a concern, calling attention to the need for studies in other parts of Brazil. In addition, the risk of inadequate serum retinol in newborns was significantly higher among infants of postpartum women with serum retinol levels below 1.05 micromol/L. Gestational XN was associated with inadequate levels of maternal serum retinol, and the results suggest a poor relation between maternal XN and vitamin A nutritional status of newborns.

The night vision threshold test is a better predictor of low serum vitamin A concentration than self-reported night blindness in pregnant urban Nepalese women

This study was conducted to validate the night vision threshold test (NVTT) as an indicator of night blindness. A total of 1401 pregnant women from the National Maternity Hospital participated in this study. Women were queried about night blindness and took the NVTT using standardized procedures after 10 min of dark adaptation. Sixteen percent failed the NVTT, but only 6.4% reported having night blindness. Blood samples from women who failed the NVTT (cases) and matched controls indicated the serum vitamin A (SVA) concentration was lower (P < 0.05) in cases (1.19 +/- 0.03 micromol/L) than in controls (1.29 +/- 0.03 micromol/L). The SVA concentrations did not differ between women who reported and did not report night blindness. The SVA concentration was correlated (r = 0.22, P < 0.001) with the NVTT scores. Twenty-five percent of women with an SVA < 0.35 micromol/L reported night blindness while 100% failed the NVTT. Nineteen percent of women with an SVA < 0.70 micromol/L reported night blindness while 73% failed the NVTT. A receiver operating characteristics analysis indicated that the NVTT had greater sensitivity (0.73 vs. 0.19) and less specificity (0.51 vs. 0.87) compared with reported night blindness for women with SVA < 0.70 micromol/L and greater sensitivity (100.0 vs. 0.73) and similar specificity (0.51 vs. 0.50) for women with SVA < 0.35 micromol/L. The NVTT identified women with low SVA and self-reported night blindness was misleading. We provide a preliminary algorithm to predict the population of women with low SVA concentrations.

Validation of night blindness reports among children and women in a vitamin A deficient population in rural Tanzania

OBJECTIVE

This study validates different definitions of reported night blindness (XN) in a vitamin A deficient African population with no local term for XN.

DESIGN

Case-control study with follow-up after treatment.

SETTING

Eight primary schools and health centres in rural Tanzania.

SUBJECTS

A total of 1214 participants were screened for reported XN and other eye signs of xerophthalmia: 461 children aged 24-71 months, 562 primary school-age children and 191 pregnant or breast-feeding women. All 152 cases of reported XN were selected for the validation study and group matched with 321 controls who did not complain of XN. XN reports were validated against serum retinol concentrations and pupillary dark adaptation measurements in cases and controls.

INTERVENTION

All children and women who reported XN or had other signs of active xerophthalmia were treated with vitamin A and followed up 3-4 weeks later. Half of the untreated control group who had their serum retinol examined in the baseline examination were also followed up.

RESULTS

The overall prevalence of reported XN was 12.5%. At baseline, mean pupillary threshold (-1.52 vs -1.55 log cd/m(2), P=0.501) and median serum retinol concentrations (0.95 vs 0.93 micromol/l, P=0.734) were not significantly different in cases and controls either overall or in each population group. More restricted case definitions reduced the prevalence of reported XN to 5.5% (P<0.001), but there was still no significant difference between cases and controls although the results were in the expected direction. After treatment, the median serum retinol concentration improved significantly only in the most deficient group, the young children. Dark adaptation improved in all the subgroups but the difference was only significant for young children and primary school-age children when the restricted case definitions were used.

CONCLUSIONS

XN reports are a poor indicator of vitamin A deficiency in this population.

SPONSORSHIP

Task Force Sight and Life, Basel, Switzerland.

Current status of vitamin A deficiency and the National Vitamin A Control Program in Nepal: results of the 1998 National Micronutrient Status Survey

The overall objective of the Nepal Micronutrient Status Survey (NMSS) was to assess the distribution and severity of micronutrient malnutrition, and to measure the progress achieved by different interventions. Data presented in this paper concern the prevalence of vitamin A deficiency (VAD) and the outreach and coverage of the National Vitamin A Supplementation activity. A multi-stage cluster sample design was employed that provided statistically representative data for each of thirteen eco-development strata (because of low population density, the West Mountains, Mid-west Mountains and Far-west Mountains were combined into a single stratum). The design allowed for aggregate estimates to be made at the national and ecological zone level. The survey showed a significant improvement in the status of clinical vitamin A deficiency in Nepal. The prevalence of both Bitot's spots and night-blindness among preschool children decreased from levels observed in surveys conducted in the previous twenty years. However, the prevalence of night-blindness was found to be 5% among women, and over 1% among school-aged children, which indicates that the entire population is vulnerable to VAD. These observations support findings from other surveys that have noted a high prevalence of maternal night-blindness in Nepal. Biochemical data collected as part of the survey indicated a high prevalence of low serum retinol (< 0.70 mumol/l), particularly among preschool children. Almost one of every three children (32.3%) and one of every six women (16.6%) had low serum retinol values. Low serum retinol among preschool children was associated with young age (6-11 months), rural location, wasting, presence of night-blindness and Bitot's spots, and residence in the Terai or Mountains. Similarly, sub-clinical VAD in women was associated with age (less than 20 years), pregnancy, the presence of night-blindness and residence in the Terai or Mountains. In the 42 districts covered by the National Vitamin A Programme (NVAP), more than 87% of preschool children were reached with vitamin A capsules. In addition to this, the National Immunisation Day (NID) provided oral polio vaccine drops to an estimated 95.7% of children 12-59 months. Awareness of the importance of vitamin A was, however, much higher in the NVAP districts than in non-programme districts. As would be expected, clinical VAD was most prevalent among children who had not received vitamin A during the most recent vitamin A capsule distribution. Indeed, the data show that vitamin A capsule receipt among children conferred a 59% protective effect for night-blindness and a 51% effect for Bitot's spots. These results point to significant progress having been achieved by the NVAP and NID capsule distribution activities.

Hyporetinolemia and acute phase proteins in children with and without xerophthalmia

BACKGROUND

The relations among hyporetinolemia, acute phase proteins, and vitamin A status in children are unclear.

OBJECTIVE

The objective was to examine the relations between acute phase proteins and plasma retinol concentrations in children with and without clinical vitamin A deficiency (Bitot spots and night blindness).

DESIGN

The study was a nonconcurrent analysis of acute phase protein concentrations and other data from a previous clinical trial. Preschool children, 3-6 y of age, with (n = 118) and without (n = 118) xerophthalmia were assigned to receive oral vitamin A (60 mg retinol equivalent) or placebo and were seen at 5 wk. All children received oral vitamin A (60 mg retinol equivalent) at 5 wk.

RESULTS

At baseline, alpha(1)-acid glycoprotein (AGP) was elevated in 42.9% and 23.5% (P < 0.003) and C-reactive protein (CRP) was elevated in 17.7% and 13.7% (NS) of children with and without xerophthalmia, respectively. Hyporetinolemia (retinol < 0.7 micromol/L) occurred in 61.0% and 47.4% (P < 0.04) of children with and without xerophthalmia, respectively. A history of fever, a history of cough, and nasal discharge noted on examination were each associated with elevated acute phase proteins. Vitamin A supplementation increased plasma retinol at 5 wk but had no significant effect on concentrations of acute phase proteins.

CONCLUSIONS

Elevated acute phase protein concentrations and infectious disease morbidity are closely associated during vitamin A deficiency.

Hyporetinolemia, illness symptoms, and acute phase protein response in pregnant women with and without night blindness

We examined the association among elevations in acute phase proteins, reported illness, and hyporetinolemia in 234 pregnant Nepali women with (cases) and without (controls) night blindness. Serum alpha1-acid glycoprotein (AGP) and C-reactive protein (CRP) were inversely associated with serum retinol concentrations. Elevations in the concentration of CRP in both cases and controls and of AGP in cases were associated with significant reductions (approximately 0.2-0.3 micromol/L) in serum retinol. The risk of a low serum retinol concentration (< 0.7 micromol/L) with elevated AGP (> or = 1 g/L) and CRP (> or = 5 mg/L) concentrations was significantly higher in cases (odds ratios = 8.6 and 4.3, respectively) than in controls (odd ratios = 1.9 and 2.4, respectively). A 7-d morbidity history indicated that cases were significantly more likely than controls to report symptoms of infections of the urinary, reproductive, and gastrointestinal tracts. Only a few of these symptoms (diarrhea, nausea, and vomiting) were significantly associated with low serum retinol concentrations. Illness in the previous week and elevated CRP or AGP concentrations were synergistically associated with lower serum retinol. For example, the reduction in serum retinol in women with diarrhea and elevated AGP was 0.54 micromol/L, compared with a reduction of 0.03 micromol/L in those with diarrhea only. AGP and CRP may provide useful information about the effect of reported illness on hyporetinolemia in pregnancy. Infection-related hyporetinolemia may predispose women to night blindness during pregnancy in Nepal.

Night blindness of pregnancy in rural Nepal--nutritional and health risks

BACKGROUND

Night blindness (XN) is the most common clinical symptom of vitamin A deficiency among children in developing countries. Yet little is known about the aetiology or associated risks of maternal XN. Emerging evidence from South East Asia suggests that it may be more frequent than previously thought in women of reproductive age, especially during pregnancy.

METHODS

A population-based, case-control study was conducted to reveal the epidemiology of XN among pregnant Nepali women. Night blind cases were identified by history through a weekly community surveillance system. Controls were randomly selected from a pool of pregnant women without XN and pair-matched for gestational age of the cases. A home-based assessment was done within a week of selection, at which 7-day food frequency and morbidity histories were collected, anthropometry measured, and capillary blood drawn for serum retinol, beta-carotene and haemoglobin (Hb) estimation.

RESULTS

Cases and controls did not differ by age or number of previous pregnancies. However, cases were more likely to be from the lower castes, be illiterate, live in poorer quality homes, and own no land. The mean serum retinol level of cases was approximately 0.30 mumol/l lower than controls (P < 0.001), indicating a low vitamin A status of night blind pregnant women. Mean Hb level was significantly lower (by 0.7 g/dl, P < 0.004), and the risk of severe anaemia (Hb < 7.0 g/dl) higher among cases than controls (odds ratio = 3.0, 95% CI: 1.25-7.23). Cases were more under-nourished than controls reflected by lower mean weight (-2.6 kg), body mass index (-0.8), arm circumference (-0.9 cm) and triceps skinfold (-0.8 mm). Night blindness was associated with less frequent consumption of preformed vitamin A (milk products, fish and meat) and provitamin A (dark green leafy vegetables and mangoes) foods, especially in summer. Night blind women were 2-3 times more likely to report symptoms of urinary/reproductive tract infections such as lower abdominal pain, painful and burning urination, or vaginal discharge, symptoms of diarrhoea/dysentery, of pre-eclampsia or eclampsia, and of nausea, vomiting or poor appetite throughout pregnancy than controls.

CONCLUSION

Women who experience XN during pregnancy have a low vitamin A status, although several other risk factors appear to cluster among these women as well. Night blind women are also more likely to be anaemic, ill, and acutely under-nourished, and to be consuming a nutritionally poorer diet in pregnancy than non-night blind pregnant women. A simple history of XN can identify women at high risk during pregnancy who may require special nutritional support, antenatal care and counselling.

Ocular findings in cystic fibrosis patients receiving vitamin A supplementation

BACKGROUND

Vitamin A deficiency with eye symptoms has been reported in patients with cystic fibrosis who received the recommended daily intake of vitamin A.

METHODS

We measured serum retinol, dark adaptation, contrast sensitivity, and dry eye status in 35 adult cystic fibrosis patients to ascertain whether they had ocular signs or symptoms.

RESULTS

Median serum retinol concentration was 1.95 mumol/l, range 1.08-4.01 mumol/l, with no values indicating vitamin A deficiency. Retinal light sensitivity was normal. Nineteen patients had reduced contrast sensitivity. Conjunctival imprints all showed plenty of goblet cells, but were characteristic of dry eye in 42% of patients (n = 14). Decreased tear film stability was found in 49% (n = 17), tear production was low in 31% (n = 11), and 23% (n = 8) showed an increased amount of dying epithelial cells. Nine patients (26%) had keratoconjunctivitis sicca according to the Copenhagen criteria.

CONCLUSION

Our patients had no biochemical or clinical signs of vitamin A deficiency. We speculate that the high incidence of dry eye could be a primary manifestation of cystic fibrosis.

Diagnosis of night blindness and serum vitamin A level: a population-based study

In a cross-sectional survey of 5420 children in northern Bangladesh, 124 were reported to have night blindness by their parents. Of these, 105 cases along with controls matched for age, sex, and neighbourhood had their scotopic vision examined under standard condition using a luxometer, underwent an ophthalmological examination, and had their serum vitamin A level determined. The mean serum vitamin A level was lowest among children identified as night blind by both their parents and the investigators (16.3 micrograms/dl; 95% confidence interval (CI), 13.9-18.7) and highest among those identified as not night blind by both their parents and the investigators (23.6 micrograms/dl; 95% CI, 21.3-25.9). The results show that parents' report of their children's night blindness had low sensitivity compared with diagnosis using standard observations of scotopic vision with a luxometer.

A prevalence study of vitamin A deficiency and xerophthalmia in northeastern Thailand

An epidemiologic survey of the prevalence of xerophthalmia and vitamin A deficiency was conducted in May and June 1985 in a multistage random sample of 1,772 children 1-8 years of age from 16 rural villages and the capital city of the Sakon Nakhon province in northeastern Thailand. Data of clinical eye examinations were available for 92% (n = 903) of the eligible children aged 1-5 years (n = 982); history of night blindness was obtained from a reliable source from 93% (n = 1,644) of the whole sample; and biochemical data were available for 60% (1,060) of the children examined. The distribution of clinical signs of xerophthalmia and serum retinol levels differed between the rural and urban areas. In the urban area, no signs of xerophthalmia or deficient serum retinol levels were found in the preschool children examined. The prevalence of night blindness in the rural area was 1.3% in children aged 1-5 years (95% confidence interval (Cl) 0.7-1.9); Bitot's spots were seen in 0.4% (95% Cl 0.1-1.0); 12.7% (95% Cl 9.9-15.5) showed deficient serum retinol levels (less than 0.35 mumol/liter). Of the children aged 1-8 years, 9.6% (95% Cl 7.8-11.4) showed deficient serum retinol levels. In the rural area, the prevalence of night blindness, Bitot's spots, and deficient serum retinol levels indicates a problem of public health importance according to World Health Organization criteria.

Nyctalopia and conjunctival xerosis indicating vitamin A deficiency in cystic fibrosis

Thirty-one Cystic Fibrosis patients were investigated for clinical and biochemical evidence of Vitamin A deficiency. All had been prescribed oral pancreatic enzyme replacements and twice the recommended daily requirement of Vitamin A (5000IU). None were aware of any ocular symptoms, but 3 out of 31 (10 per cent) were found to have frank conjunctival xerosis and six (19 per cent) to have abnormal dark adaptation. There was no correlation between the above findings and abnormal liver function or clinical disease severity. All patients with cystic fibrosis should have regular Vitamin A estimations with ophthalmological assessment if serum levels fall below 30 microgram/dl.

Dark adaptation compared with electrooculography in primary biliary cirrhosis

In a series of asymptomatic patients with primary biliary cirrhosis there was a significant impairment of dark adaptation thresholds as compared with a control group. Vitamin A levels were abnormally low in only two of the patients and these two both showed high dark adaptation thresholds. The electrooculogram was reduced in only the most severely affected case. It is suggested that visual function tests should be performed alongside vitamin A level measurements before deciding on treatment.

A simple field test for identification of night-blindness

A simple and replicable field test to measure dark adaptation time has been developed. It required a darkened room with a 5 watt bulb covered with a piece of black cloth, a spherical white object of 22 cm diameter suspended vertically from a horizontal string, a stool, a black curtain, a Maxwell electronic photographic flash unit and a stop-watch. The spherical object behind the closed curtain was hung 1.5 m away from the subject either to his left or right, or in the centre of the room. The seated subject was then exposed to 3 consecutive flashes, the curtain drawn, and the time taken to identify the position of the object was noted on the stop-watch. The test was conducted for 3 consecutive days on non-night blind young adult girls (n = 46) of the high income group (PC); underprivileged school-age children (n = 44) with a positive history of night-blindness (NB), and their age/sex pair-matched (n = 44) non-night-blind controls (NNB). The NB group had a significantly higher mean dark adaptation time as compared to the NNB and PC groups (14.9 sec vs 11.9 and 11.3 sec respectively). The mean serum vitamin A levels of NB, NNB and PC groups (15.8, 17.5 and 29.5 micrograms/dl respectively) were correlated with the dark adaptation times.