Ocular biometry and determinants of refractive error in rural Myanmar: the Meiktila Eye Study

OBJECTIVE

To describe the ocular biometry and determinants of refractive error in an adult population in Myanmar.

METHODS

A cross-sectional, population-based survey of the inhabitants 40 years of age and over from villages in the Meiktila District was performed; 2481 eligible participants were identified, and 2076 participated in the study. Biometric components including axial length (AL), anterior chamber depth (ACD), vitreous chamber depth (VCD), lens thickness (LT) and corneal curvature (CC) were measured. Lens opalescence was measured using the Lens Opacity Grading System III. Non-cycloplegic refraction was measured with an autorefractor.

RESULTS

Complete biometric, refractive and lenticular data were available on 1498 participants. Men had longer ALs, ACDs, VCDs and steeper CCs than women. There was an increase in LT, nuclear opalescence (NO) and myopic shift with increasing age, with no significant change in AL with age. In the 40-59 year age group, VCD was a significant predictor of refractive error, but LT (p<0.001) and NO (p<0.001) were stronger predictors. In the 60+ age group, NO (p<0.001) was also the dominant predictor of refractive error.

CONCLUSION

This Burmese population, particularly women, has a relatively short AL and ACD. NO is the strongest predictor of refractive error across all age groups in this population.

Anisometropia in an adult population in rural myanmar: the Meiktila Eye Study

PURPOSE

To determine the prevalence and risk factors for anisometropia in a rural adult population in central Myanmar.

METHODS

A population-based ophthalmic survey was conducted in rural villages in central Myanmar. Ansiometropia was assessed in subjects with phakic eyes. The severity of anisometropia was defined as the absolute difference of the spherical equivalent between the two eyes.

RESULTS

Prevalence of anisometropia (> or =1.0 D) in all participants was 35.3% (95% CI 32.7-37.9%); severe anisometropia (> or =2.0 D) was present in 18.9 % (95% CI 16.8-21.0%). There was no significant gender difference in anisometropia prevalence or severity. Prevalence and severity of anisometropia were significantly associated with age. Multiple logistic regression analysis revealed that cataract, myopia, but not age, were associated with anisometropia. The between-eye differences in axial length (r = 0.15, p < 0.001) and corneal curvature (r = 0.19, p < 0.001) were significantly correlated with the severity of anisometropia.

CONCLUSIONS

Prevalence of anisometropia is relatively high in this rural adult population in Myanmar. Myopia and cataract, but not increasing age, are the potential risk factors of anisometropia in this population.

Education, socio-economic status and age-related macular degeneration in Asians: the Singapore Malay Eye Study

BACKGROUND/AIMS

Low socio-economic status is increasingly being identified as a risk marker for chronic diseases, but few studies have investigated the link between socio-economic factors and age-related macular degeneration (AMD). The present study aimed to assess the association between socio-economic status and the prevalence of AMD.

METHODS

A population-based cross-sectional study of 3280 (78.7% response rate) Malay adults aged 40-80 years residing in 15 south-western districts of Singapore. AMD was graded from retinal photographs at a central reading centre using the modified Wisconsin AMD scale. Early and late AMD signs were graded from retinal photographs following the Wisconsin grading system. Socio-economic status including education, housing type and income were determined from a detailed interview.

RESULTS

Of the participants, 3265 had photographs of sufficient quality for grading of AMD. Early AMD was present in 168 (5.1%) and late AMD in 21 (0.6%). After adjusting for age, gender, smoking, hypertension, diabetes and body mass index, participants with lower educational levels were significantly more likely to have early AMD (multivariate OR 2.2, 95% CI 1.2 to 4.0). This association was stronger in persons who had never smoked (multivariate OR 3.6, 95% confidence CI 1.4 to 9.4). However, no association with housing type or income was seen.

CONCLUSIONS

Low educational level is associated with a higher prevalence of early AMD signs in our Asian population, independent of age, cardiovascular risk factors and cigarette smoking.

Cataract in rural Myanmar: prevalence and risk factors from the Meiktila Eye Study

AIMS

To determine the prevalence of and risk factors for cataracts in a rural region of central Myanmar.

METHODS

A cross-sectional, population-based survey of inhabitants >or=40 years of age from villages of central Myanmar; 2076 participated, and 2044 (82.3%) had an examinable lens in at least one eye. Data recording included smoking history, occupation, education level, betel-nut chewing, height and weight, and dilated lens assessment using Lens Opacities Classification System III grading: nuclear (>or=4), cortical (>or=2) and posterior subcapsular (>or=2) cataracts. Aphakic and pseudophakic eyes were included as operated cataracts for statistical analysis.

RESULTS

The prevalence of any cataract including operated eyes was 40.39% (95% CI 37.30 to 43.48%): 27.35% nuclear, 20.91% cortical and 11.34% posterior subcapsular cataracts. No significant association was found between cataract and betel-nut use, gender, smoking or outdoor occupation. The likelihood of all cataract types increased with age (multivariate analysis including operated eyes: OR 1.154, CI 1.13 to 1.18, p<0.001). Low level of education and low body mass index were associated with nuclear cataracts. Large village size was associated with increased risk for nuclear cataract (OR 3.23, CI 1.989 to 5.250, p<0.001) and decreased risk for cortical cataract (OR 0.20, CI 0.08 to 0.47, p<0.001).

CONCLUSIONS

The prevalence of cataract in rural Myanmar is similar to that in other developing Asian regions. Cataracts are strongly associated with increasing age, and are more common in those with lower education and lower body mass index.

The high prevalence of unrecognized anaemia in patients with diabetes and chronic kidney disease: a population-based study

BACKGROUND

Anaemia occurs early in the course of diabetes-related chronic kidney disease (CKD). There is little evidence about the prevalence of anaemia in people with diabetes. The aim of this study was to assess the prevalence of anaemia, by stage of CKD, in the general diabetic population.

METHODS

Haemoglobin (Hb) was measured on all glycated haemoglobin (HbA1c) samples and the most recent (< 4 months) estimated glomerular filtration rate (eGFR) was obtained. Anaemia (at treatment level) was defined as Hb < 110 g/l or the use of erythropoetic stimulating agents (ESA).

RESULTS

Twelve per cent (10-14%) of people had Hb < 110 g/l. The prevalence of anaemia increased progressively with worsening CKD. People with CKD stage 3 accounted for the largest number of people with anaemia; 18% (95% CI 13-24%) had Hb < 110 g/l. Those with eGFR < 60 ml/min/1.73 m2 and not on ESA or dialysis were four (2-7) times more likely than patients with better renal function to have Hb < 110 g/l. The relation between Hb and eGFR became approximately linear below an eGFR of 83 ml/min/1.73 m2, where, for every 1 ml/min/1.73 m2 fall in eGFR, there was a 0.4 (0.3-0.5) g/l fall in haemoglobin.

CONCLUSIONS

This study demonstrates that anaemia, at levels where treatment is indicated, occurs commonly in people with diabetes and CKD stage 3 or worse. The screening for anaemia in current diabetes management should be extended.

Prevalence of refractive error in rural Myanmar: the Meiktila Eye Study

OBJECTIVE

To determine the prevalence of refractive error and associated risk factors in the Meiktila District of central rural Myanmar.

DESIGN

Population-based cross-sectional study.

PARTICIPANTS

Randomized stratified cluster sampling of the inhabitants 40 years or older from villages in Meiktila was performed; 2481 eligible participants were identified, 2076 participated in the study, and adequate refractive data were obtained on 1863 individuals (75.1%).

METHODS

Demographic data including age, gender, and education level were obtained from all participants. The ophthalmic examination included autorefraction, nuclear opalescence (NO) grading at the slit lamp, and applanation tonometry.

MAIN OUTCOME MEASURES

Refractive errors were classified by type of ametropia and their prevalence was determined. Univariate and multivariate analyses were performed and odds ratios were calculated for the predictors of refractive error within the statistical models.

RESULTS

Mean refractive error measured -1.3 diopters (D) (standard deviation [SD], 2.9) and mean cylindrical error measured 1.1 D (SD, 1.5). Myopia of >-1.0 and >-6.0 D occurred in 42.7% (95% confidence interval [CI], 40.4%-44.9%) and 6.5% (95% CI, 5.4%-7.6%) of subjects, respectively. Myopic refractive error was associated significantly with a higher degree of NO (P<0.001) and age. Hypermetropia of >+1.0 D occurred in 15% (95% CI, 5.4%-7.6%) of the population and was associated with higher education levels (P<0.001). Astigmatism worse than 1.0 D occurred in 30.6% (95% CI, 28.5%-32.7%) of the population and was associated with age (P<0.001) and NO (P<0.001).

CONCLUSION

Myopia was more prevalent in older subjects and in those with increased NO. The prevalence rates of myopia in the > or =40 age group are higher than those found in other Asian regions and are likely to contribute to visual impairment.

Gonioscopy findings and prevalence of occludable angles in a Burmese population: the Meiktila Eye Study

AIM

To determine the prevalence of preglaucomatous angle-closure disease in central Myanmar.

METHODS

A population-based survey of inhabitants >or=40 years in the Meiktila District was carried out; 2481 subjects were identified, 2076 participated and 2060 underwent gonioscopy of at least one eye. Eyes with angles traditionally described as "occludable" were recorded as primary angle-closure suspects (PACS); eyes with PACS and peripheral anterior synechiae (PAS), or an increased intraocular pressure but without primary angle-closure glaucoma, were recorded as primary angle closure (PAC).

RESULTS

The prevalence of PACS in at least one eye was 5.7% (95% CI 4.72 to 6.62); prevalence increased with age and was more common in women (p<0.001). The prevalence of PAC in at least one eye was 1.50% (95% CI 1.47 to 1.53). All participants with PAS had at least 90 degrees of closure (range 90-360 degrees).

CONCLUSION

The prevalence of preglaucomatous angle-closure disease (PACS and PAC) in this population was 5.7% and 1.5%, respectively. PACS was more common in women, and its prevalence increased with age.

Prevalence of glaucoma in rural Myanmar: the Meiktila Eye Study

AIM

To determine the prevalence of glaucoma in the Meiktila district of central, rural Myanmar.

METHODS

A cross-sectional, population-based survey of inhabitants > or =40 years of age from villages in Meiktila district, Myanmar, was performed; 2481 eligible participants were identified and 2076 participated in the study. The ophthalmic examination included Snellen visual acuity, slit-lamp examination, tonometry, gonioscopy, dilated stereoscopic fundus examination and full-threshold perimetry. Glaucoma was classified into clinical subtypes and categorised into three levels according to diagnostic evidence.

RESULTS

Glaucoma was diagnosed in 1997 (80.5%) participants. The prevalence of glaucoma of any category in at least one eye was 4.9% (95% CI 4.1 to 5.7; n = 101). The overall prevalence of primary angle-closure glaucoma (PACG) was 2.5% (95% CI 1.5 to 3.5) and of primary open-angle glaucoma (POAG) was 2.0% (95% CI 0.9 to 3.1). PACG accounted for 84% of all blindness due to glaucoma, with the majority due to acute angle-closure glaucoma (AACG).

CONCLUSION

The prevalence of glaucoma in the population aged > or =40 years in rural, central Myanmar was 4.9%. The ratio of PACG to POAG was approximately 1.25:1. PACG has a high visual morbidity and AACG is visually devastating in this community. Screening programmes should be directed at PACG, and further study of the underlying mechanisms of PACG is needed in this population.

Degree of angle closure and extent of peripheral anterior synechiae: an anterior segment OCT study

AIMS

To evaluate the relationship between angle width as determined by anterior segment optical coherence tomography (AS-OCT) and the presence of peripheral anterior synechiae (PAS).

METHODS

This was a prospective observational case series in which 203 subjects with primary angle closure or open angles were recruited. Images of the nasal, temporal and inferior angles were obtained with AS-OCT in dark conditions. Subjects then underwent gonioscopy by an independent examiner who was masked to the AS-OCT findings. PAS were identified by gonioscopy and defined as abnormal adhesions of the iris to the angle that were at least half a clock hour in width and present to the level of the anterior trabecular meshwork or higher. The total clock hours of PAS were recorded.

RESULTS

Sixty-eight subjects (33.5%) were PACS, 76 subjects (37.4%) had PAC/PACG, 14 (6.9%) had primary open angle glaucoma, and 45 (22.2%) subjects were normal with open angles. There was a weak but significant correlation between the angle opening distance (AOD), trabecular iris space area (TISA) and angle recess area (ARA) with clock hours of PAS (Spearman's correlation coefficients = -0.30, -0.32 and -0.32, respectively, p<0.001). The mean values of the AOD, TISA and ARA in the nasal, temporal and inferior quadrants were significantly less in eyes with PAS compared with those without (p<0.001, Mann-Whitney U test). Analysis by quadrant showed that these parameters were smaller in the nasal and temporal quadrants in eyes with PAS (p<0.01).

CONCLUSIONS

Angle width determined by AS-OCT and the extent of PAS were weakly correlated, and angle width was significantly smaller in eyes with PAS.

Prevalence and causes of visual impairment in rural myanmar: the Meiktila Eye Study

OBJECTIVE

To determine the prevalence and causes of visual impairment in the Meiktila district of central, rural Myanmar.

DESIGN

Population-based cross-sectional study.

PARTICIPANTS

Random, stratified, cluster sampling of the inhabitants 40 years of age and older from villages in the Meiktila district was performed; 2481 eligible participants were identified and 2076 participated in the study.

METHODS

The ophthalmic examination included presenting and pinhole Snellen visual acuity with an illiterate E chart, slit-lamp examination of the anterior segment, and dilated stereoscopic fundus examination. The principal cause of visual impairment was recorded.

MAIN OUTCOME MEASURES

Visual impairment and blindness were defined by both presenting and corrected visual acuity according to World Health Organization criteria: better eye < 6/18 and < 3/60, respectively.

RESULTS

Comprehensive examinations, including Snellen visual acuity, were performed on 2073 participants (83.6%) The prevalence estimate of presenting visual impairment was 40.4% (95% confidence interval [CI], 36.1-44.7) and of presenting blindness was 8.1% (95% CI, 6.5-9.9). After pinhole correction, the corresponding prevalences were 26.8% (95% CI, 23.5-30.1) and 5.3% (95% CI, 4.0-6.6). Cataract, uncorrected refractive error, and glaucoma were the most common causes of visual impairment.

CONCLUSIONS

Visual impairment and blindness remain major public health problems in rural Myanmar. Specific programs directed toward reducing the cataract burden need to be implemented.

Socioeconomic status, systolic blood pressure and intraocular pressure: the Tanjong Pagar Study

BACKGROUND

Lower socioeconomic status (SES) is associated with higher morbidity and mortality in many countries. Present evidence suggests that glaucoma has similar risk factors to major chronic diseases such as cardiovascular disease. This study investigates the association between SES and intraocular pressure (IOP), an important risk factor for glaucoma.

METHODS

The Tanjong Pagar Study was a population-based cross-sectional survey of Chinese people aged 40-79 years, who were randomly selected from the Singapore electoral register. Of the 2000 people selected, 1717 were considered eligible and 1090 were examined in clinic and included in the present study. IOP was measured using applanation tonometry. SES was assessed using a standardised questionnaire; education and income were used as the main explanatory variables. The effect of systolic blood pressure (SBP) was also examined.

RESULTS

Participants with lower levels of education and income had higher mean IOP (both p<0.01). These associations remained after adjusting for age and central corneal thickness, a strong independent predictor. SBP was strongly associated with both SES and IOP (both p<0.01). Adjusting for SBP attenuated the association between SES and IOP.

CONCLUSION

Participants with lower education and income have a higher mean IOP. This effect may be mediated, in part, by an association of education and income with SBP. This is the first study to suggest that there is a social gradient in the distribution of the only major modifiable risk factor for glaucoma. Increasing similarities exist between the causation models of chronic diseases and that of glaucoma.

Central corneal thickness and its relationship to myopia in Chinese adults

AIM

To investigate the association between central corneal thickness (CCT) and the degree of myopia among Chinese.

METHODS

In this prospective observational study, 714 consecutive patients were recruited from a refractive surgery clinic. CCT was measured in both eyes of each patient using the Orbscan (Bausch and Lomb, Rochester, New York, USA), and data of the right eye were selected for analysis. CCT was correlated with the degree of myopia in dioptres (D) using Pearson's correlation coefficient and Dunnett's t test with multiple comparisons.

RESULTS

The age of the patients ranged from 15 to 59 years. The mean CCT was 534.5 microm, with a standard deviation (SD) of 38.1 (range 305-684) microm. The mean (SD) myopic spherical equivalent was 5.30 (2.74) D, range -17.5--0.625 D. No correlation was found between CCT and the degree of myopia (r = -0.13, p = 0.719).

CONCLUSIONS

Among Chinese with myopia, CCT was distributed over a large range but did not correlate with the degree of myopia.

Visual acuity after acute primary angle closure and considerations for primary lens extraction

BACKGROUND/AIM

Primary lens extraction has been advocated for acute primary angle closure (APAC), but it is not known if this is warranted in all cases. The aim of this study was to investigate the visual acuity (VA) of APAC eyes shortly after resolution of the acute episode in order to assess the appropriateness of performing such surgery in this condition.

METHODS

This was a prospective observational case series. As part of a randomised controlled trial comparing phacoemulsification and laser iridotomy, 135 consecutive APAC subjects over a 2 year period underwent subjective refraction and measurement of Snellen VA once the acute episode had resolved with reduction of intraocular pressure (IOP) and improved corneal clarity.

RESULTS

Subjects were predominantly Chinese (95.6%) and female (79.3%), with a mean age of 63.6 (SD 9.6) years. When assessed 1.7 (2.7) days after presentation, the majority of APAC cases (50.4%) had good VA (6/12 or better), with more than a quarter of cases having VA of 6/7.5 or better. Poor VA was associated with duration of symptoms (p = 0.04, OR = 4.1, 95% CI 1.1 to 15.7) and time taken to resolution of APAC (p = 0.04, OR = 2.2, 95% CI 1.02 to 4.6), but not with sex (p = 0.31), age (p = 0.26), duration from presentation to measurement of visual acuity (p = 0.53), or presenting IOP (p = 0.73).

CONCLUSION

Within days after APAC, more than half of APAC affected eyes had good VA (6/12 or better). The role of lens extraction in the management of APAC warrants further debate, especially for eyes with good VA.

Choroidal expansion as a mechanism for acute primary angle closure: an investigation into the change of biometric parameters in the first 2 weeks

BACKGROUND/AIM

Choroidal expansion with anterior movement of the lens was recently proposed as a mechanism for acute primary angle closure (APAC). The aim of this study was to compare the biometric parameters, central anterior chamber depth, limbal chamber depth, lens thickness, and lens position, within 24 hours of presentation and 2 weeks later in eyes with APAC.

METHODS

This was a prospective observational case series of 41 subjects with APAC. Subjects who presented with APAC were treated with medical therapy followed by laser iridotomy (LI) in both eyes once the acute attack was broken. Ocular biometry was performed in affected and fellow eyes before LI (baseline) and then 2 weeks later. Optical pachymetry was used to measure central anterior chamber depth (ACD) and the limbal chamber depth (LCD) was graded at the slit lamp. A-scan ultrasound was used to measure lens thickness (LT) and axial length (AL). Lens position (LP) was defined as ACD +(1/2)LT.

RESULTS

The majority of subjects were Chinese (83%) and female (61%), and the mean age was 60.4 (SD 10.3) years. In affected eyes, the ACD was 1.81 (0.29) mm before and 1.80 (0.28) mm 2 weeks after LI (p = 0.63), while in fellow eyes, the ACD was 1.83 (0.29) mm and 1.81 (0.38) mm, respectively (p = 0.21). There was no significant change in lens position, relative lens position, or axial length in both affected and fellow eyes over the 2 weeks.

CONCLUSIONS

There was no change observed in central anterior chamber depth, lens thickness, or lens position at the time of the acute attack compared to 2 weeks later in both APAC affected and fellow eyes. The findings do not support the hypothesis of lens movement due to choroidal expansion in APAC.

Effect of barometric pressure on sea level variations in the Pacific region

Barometric pressure and sea level data sets from the South Pacific Sea Level and Climate Monitoring Project funded by AusAID were analysed for twelve Tropical Pacific island countries. During mid-1997 and 1998 pressure anomalies over the Pacific region were strongly positive and sea level dropped significantly. As a consequence, sea level trends in the Pacific region suddenly changed from positive to negative. It was believed that the delayed effect of the 1997 strong El Ni�o episode was directly linked to these positive pressure anomalies. The same observations were made in 2002 and 2003 during another El Ni�o episode which was however not as strong as the previous one. The La Ni�a episode which followed the 1997-98 El Ni�o in 1999 had opposite effects. The pressure anomalies were negative and the sea level anomalies were positive. While the thermal effect due to global warming is still the cause of sea level rise in the Pacific region, it is clearly evident that the barometric pressure effect on sea level is more abrupt and it can overshadow the other effects at least temporarily.

Defining "occludable" angles in population surveys: drainage angle width, peripheral anterior synechiae, and glaucomatous optic neuropathy in east Asian people

BACKGROUND

/aim: A current consensus in epidemiological studies of primary angle closure (PAC) is to diagnose the condition only if the posterior (usually pigmented) trabecular meshwork is seen for less than 90 degrees of the angle circumference, termed an "occludable angle." The authors sought to assess the validity of this epidemiological classification by exploring the relation between drainage angle width, peripheral anterior synechiae (PAS) and glaucomatous optic neuropathy (GON).

METHODS

918 Mongolians and 995 Chinese Singaporeans, both groups aged 40 years and older were examined in two population based surveys. Gonioscopic angle width was graded in five categories (0 = closed to 4 = wide open) according the scheme described by Shaffer. Cases with secondary PAS were excluded.

RESULTS

The rate of PAS was between 0.3% and 1.7% in people with wide angles (grades 3 and 4). In those with grade 2 angles, PAS were seen in between 8% of eyes. In eyes with grade 1 angles, the rate rose to 17% in Chinese Singaporeans, and 31% in Mongolians. The odds of PAS were higher in people with narrower angles. However, there was a greater absolute number of people with PAS whose drainage angles were classified as "not occludable" than those classified "occludable."

CONCLUSIONS

The traditional view that primary angle closure becomes a significant possibility in drainage angles of < or = grade 2 (approximately 20 degrees ) is valid in east Asians. The definition of an "occludable" angle examined here excludes many people with PAS. This probably serves to underemphasise the role of PAC in population surveys of glaucoma prevalence in Asian people.