Biomedical subjects

Paul J Foster

Publications and source records attributed to Paul J Foster.

29 records · Page 2Linked to original sources

PubMed2004

Causes of blindness, low vision, and questionnaire-assessed poor visual function in Singaporean Chinese adults: The Tanjong Pagar Survey.

OBJECTIVE: To determine the prevalence rates and causes of low vision, blindness, and patient-assessed deficient visual function among Singaporean Chinese adults. DESIGN: Population-based cross-sectional survey. PARTICIPANTS: Singaporean Chinese adults 40 to 79 years old (n = 1152). METHODS: From an initial sampling frame of 40- to 79-year-old Chinese in the Tanjong Pagar district in Singapore, 2000 subjects were selected using a disproportionate, stratified, clustered, random-sampling method. Of 1717 eligible subjects, 1232 were examined (participation rate = 71.8%), and 80 adults who did not have visual acuity (VA) data were excluded from the analysis. MAIN OUTCOME MEASURES: Bilateral low vision was defined as best-corrected VA (BCVA) worse than 6/18 and 3/60 or better, and bilateral blindness as BCVA worse than 3/60 in the better eye or constriction of the visual field to within 10 degrees of fixation, in accordance with the World Health Organization criteria. Patient-assessed visual function was measured using a modified VF-14 questionnaire. RESULTS: The age- and gender-adjusted prevalence rates were 1.1% (95% confidence interval [CI], 0.6-1.8) for bilateral low vision and 0.5% (95% CI, 0.2-1.1) for bilateral blindness, and the mean visual function score was 98.6. The rates of bilateral low vision and blindness increased with age, whereas visual function scores decreased with age, even after adjusting for gender and education. Cataract accounted for 58.8% of bilateral low vision, 20.0% of bilateral blindness, and 52.0% of poor visual function (score<90). Glaucoma contributed to 60.0% of bilateral blindness. CONCLUSION: The age- and gender-adjusted rates of low vision and blindness were 1.1% and 0.5%, respectively. Glaucoma is a leading cause of blindness in Singaporean Chinese adults, in addition to well-recognized causes in the rest of Asia such as cataract.

Adult↗

PubMed2004

Undercorrected refractive error in Singaporean Chinese adults: the Tanjong Pagar survey.

OBJECTIVE: To study the prevalence of undercorrected refractive error and associated sociodemographic factors among Singaporean Chinese adults. DESIGN: Cross-sectional, population-based survey. PARTICIPANTS: Singaporean Chinese adults aged 40 to 79 years (n = 1152). METHODS: The Singapore electoral register of Tanjong Pagar was used as a sampling frame, and disproportionate, stratified, clustered, random sampling was performed. There were 1717 eligible adults and 1232 (71.8%) participated. Analysis was performed among 1152 adults with complete habitual and best-corrected visual acuity data. MAIN OUTCOME MEASURE: Undercorrected refractive error was defined as improvement of better eye visual acuity of at least 2 lines or more with best possible refractive correction. RESULTS: The age- and gender-adjusted rate of undercorrected refractive error standardized directly by age and gender was 17.3% (95% confidence interval, 15.0, 19.5). Undercorrected refractive error rates were more common in older adults who had completed fewer years of education and in those who had cataract. People who did not wear spectacles tended to have poorer vision. CONCLUSIONS: The undercorrected refractive error rate among Singaporean Chinese is relatively common compared with data from other populations.

Adult↗

PubMed2004

Systemic autonomic function in subjects with primary angle-closure glaucoma: a comparative study of symptomatic and asymptomatic disease presentation.

BACKGROUND: Autonomic dysfunction is thought to be a contributory factor in primary angle-closure glaucoma (PACG) by precipitating pupil block in anatomically predisposed eyes. This study aimed to compare systemic autonomic function between subjects who had suffered a previous episode of acute angle closure (symptomatic PACG), those who had asymptomatic PACG, and age and sex-matched controls. METHODS: Tests for systemic parasympathetic function included the heart-rate response to standing (30:15 ratio), heart-rate variation during deep breathing, and the ratio of the heart rate at phases IV and II of the Valsalva manoeuvre (Valsalva ratio). For assessment of the sympathetic nervous system, blood pressure was recorded supine and then after 2 and 5 min of standing. A modified sweat test, the sympathetic skin response, was recorded on the palm and sole. RESULTS: A total of 30 subjects were examined: eight previous symptomatic PACG, eight asymptomatic PACG and 14 control subjects. The mean ages were similar, and all except one subject were Chinese. None of the subjects had evidence of systemic dysautonomia. There was no significant difference found between the groups for the 30:15 ratio, heart-rate variation during deep respiration and the Valsalva ratio. No significant orthostatic hypotension was detected in subjects with PACG. Abnormal sympathetic skin response was not more common in PACG subjects compared to control subjects. CONCLUSIONS: This study identified no systemic autonomic dysfunction in people with PACG.

Autonomic Nervous System↗

PubMed2004

Ocular biometry and refraction in Mongolian adults.

OBJECTIVE: To describe the variation in ocular biometry and its association with refraction in adult Mongolians. METHODS: The study included 1800 subjects, aged 40 years or more, who were selected in two Mongolian provinces-Hövsgöl and Omnögobi-to participate in this population survey. Axial length (AL) and its components, as well as noncycloplegic autorefraction and corneal power (CP), were measured. RESULTS: Of those selected, 1617 subjects (90.0%) were examined. Mean +/- SD of AL was 23.13 +/- 1.15 mm. There was a very small but significant increase in mean AL with age (0.05 mm per decade, P = 0.03). Autorefraction was performed on 620 of 675 subjects of those examined in Omnögobi. The age and gender standardized prevalences of myopia (< -0.5 D), emmetropia, hyperopia (> +0.5 D), astigmatism (< -0.5 D of cylinder) and anisometropia (>1.0 D difference between eyes) were 17.2%, 49.9%, 32.9%, 40.9%, and 10.7%, respectively. Prevalence of myopia showed no clear trend with increasing age, whereas hyperopia, astigmatism, and anisometropia all increased monotonically. Multiple regression models revealed that AL (P < 0.001) and VCD (P < 0.001) were the strongest determinants of refractive error. CONCLUSIONS: In this cross-sectional study of adult Mongolians, a much lower prevalence of myopia was found than in other East Asian populations studied to date. The mean AL differed little between age groups, in marked contrast to data on Chinese people.

Adult↗

PubMed2003

Visual perception during phacoemulsification cataract surgery under topical and regional anaesthesia.

PURPOSE: To compare the subjective visual experiences of patients during phacoemulsification and intraocular lens (IOL) implantation using regional and topical anaesthesia. DESIGN: A prospective, cohort, questionnaire-based study. METHODS: The study cohort consisted of 247 patients without pre-existing ocular pathology who underwent routine phacoemulsification and IOL implantation. The mean age of the subjects was 75.4 +/- 9.4 years and 34.5% of them had a history of cataract surgery. Three different methods of local anaesthesia were used: 66 (26.7%) of the patients were given topical anaesthesia (TA); 74 (30.0%) were given sub-Tenon's anaesthesia (SA), and 107(43.3%) were given peribulbar anaesthesia (PA). The patients were interviewed immediately after surgery by theatre staff using a standardized questionnaire that investigated their intraoperative visual experiences. RESULTS: There was no significant difference between the three methods of anaesthesia regarding light perception during the surgery. However, patients undergoing surgery under TA experienced brighter light intensity levels (78.3%) than those given SA (50.0%) and PA (55.7%) (p = 0.02). A total of 69.6% of subjects who received TA reported visual perception of colours during surgery, as opposed to 56.8% of SA recipients and 49.0% of PA recipients (p = 0.02). In addition, patients under TA were more aware of surgical instruments (26.1%) than those under SA (10.8%) and PA (15.9%) (p = 0.08). The vast majority of patients in all three groups found the visual experience to be non-frightening. There were no associations between intraoperative visual impression and age or sex. Although not statistically significant (p = 0.06), prior cataract surgery appeared to alleviate some of the anxiety associated with the visual experience. CONCLUSION: Patients undergoing regional and topical anaesthesia experience a wide variety of visual sensations during surgery. The differences in visual impressions between the groups may reflect the varying degrees of optic nerve blockade that result from the different anaesthetics.

Aged↗

PubMed2003

Refractive errors, axial ocular dimensions, and age-related cataracts: the Tanjong Pagar survey.

PURPOSE: To describe the relationship of refractive errors and axial ocular dimensions and age-related cataract. METHODS: Population-based, cross-sectional survey of ocular diseases among Chinese men and women aged 40 to 81 years (n = 1232) living in the Tanjong Pagar district in Singapore. As part of the examination, refraction and corneal curvature were determined with an autorefractor, with refraction further refined subjectively. Ocular dimensions, including axial length, anterior chamber depth, lens thickness, and vitreous chamber depth, were measured with an A-mode ultrasound device. Lens opacity was graded clinically according to the Lens Opacity Classification System (LOCS) III system. Refraction, biometry, and cataract data on right (n = 989) and left (n = 995) eyes were analyzed separately. RESULTS: In analyses controlling for age, gender, education, diabetes, and cigarette smoking, nuclear cataract was associated with myopia (-1.35 D vs. -0.11 D, P < 0.001, comparing right eyes with and without nuclear cataract), but not with any specific biometric component. Cortical cataract was associated with thinner lenses (4.67 mm vs. 4.79 mm, P = 0.001, comparing right eyes with and without cortical cataract), but not with refraction and other biometric components. Posterior subcapsular cataract was associated with myopia (-1.80 D vs. -0.39 D, P < 0.001, comparing right eyes with and without posterior subcapsular cataract), deeper anterior chamber (3.00 mm vs. 2.89 mm, P = 0.02), thinner lens (4.62 mm vs. 4.77 mm, P = 0.001), and longer vitreous chamber (15.78 mm vs. 15.57 mm, P = 0.09), but not with overall axial length and corneal curvature. Adjustment for vitreous chamber depth attenuated the association between posterior subcapsular cataract and myopia by 65.5%, but did not substantially change the association between nuclear cataract and myopia. CONCLUSIONS: These population-based data support the associations between nuclear and posterior subcapsular cataracts and myopia reported in previous studies. Posterior subcapsular cataract is also associated with deeper anterior chamber, thinner lens, and longer vitreous chamber, with vitreous chamber depth explaining most of the association between posterior subcapsular cataract and myopia.

Adult↗

PubMed2003

Determinants of intraocular pressure and its association with glaucomatous optic neuropathy in Chinese Singaporeans: the Tanjong Pagar Study.

PURPOSE: To examine the relationship between intraocular pressure (IOP), anthropomorphic, demographic, socioeconomic, systemic, and ocular factors and glaucomatous optic neuropathy (GON) in Chinese people. METHODS: Chinese people (n = 2000), aged 40 to 79 years, were selected from the Singapore electoral register. Of the 1717 considered eligible for examination, 1232 participated, representing a response rate of 71.8%. IOP was estimated with Goldmann applanation tonometry. The drainage angle was assessed with static and dynamic gonioscopy. The optic nerve was examined at high magnification through a dilated pupil with a fundus contact lens or a +78-D lens. Static automated visual field testing was performed on subjects with suspected glaucoma. GON was diagnosed on the basis of structural and functional abnormalities of the optic nerve. RESULTS: The main independent determinants of higher IOP were higher systolic blood pressure (P < 0.001), quadrants of any peripheral anterior synechiae (PAS, P = 0.02) and width of the drainage angle (P = 0.049). A 100- micro m increase in corneal thickness was associated with an increase in mean IOP of 1.5 to 1.8 mm Hg (P < 0.001). Odds of GON increased 1.2 times per 1-mm Hg increase in screening IOP. A clear association between corneal thickness and GON was not identified. CONCLUSIONS: Clinical IOP estimates are related to systolic blood pressure and corneal thickness. Variation in IOP with angle width may suggest that trabecular compaction significantly contributes to causes of the increase in IOP, independent of angle-closure. GON is an IOP-related phenomenon among Chinese Singaporeans.

Adult↗

PubMed2002

The severity and spatial distribution of visual field defects in primary glaucoma: a comparison of primary open-angle glaucoma and primary angle-closure glaucoma.

OBJECTIVE: To compare the characteristics of visual field defects in primary angle-closure glaucoma (PACG) and primary open-angle glaucoma (POAG). METHODS: Subjects with primary glaucoma aged 30 years and older were prospectively considered for inclusion. Automated static white-on-white perimetry was performed. A minimum of 2 reliable tests was required with a mean deviation (MD) within 2 dB on 2 tests. Subjects with previous symptomatic angle-closure, normal-tension glaucoma, visually significant cataract, or previous intraocular surgery were excluded. RESULTS: Of 234 subjects assessed, 129 had POAG, and 105 had PACG. The MDs (POAG group, -13.3 dB; PACG group, -18.0 dB) indicated more severe visual loss in subjects with PACG. In subjects with POAG, the superior hemifield was more severely affected than the inferior. This was less pronounced in subjects with PACG. Following stratification by MD, the difference between hemifields was marked in the mild (-10 dB<or=MD) and moderate (-20 dB<or=MD<-10 dB) subgroups but was not present in the severe (MD<-20 dB) subgroup. We detected differences between POAG and PACG in retinal sensitivity between the superior and inferior hemifields, independent of severity of damage. CONCLUSIONS: The pattern of visual field loss was different in the 2 diseases. This may give insight into the pattern of visual loss in predominantly pressure-dependent glaucomatous optic neuropathy.

Aged↗

PubMed2002

Prevalence of lens opacity in Chinese residents of Singapore: the tanjong pagar survey.

OBJECTIVE: To determine the prevalence of lens opacity among Chinese residents of Singapore. DESIGN: Population-based, cross-sectional survey. PARTICIPANTS: Chinese men and women aged 40 years or more in Singapore. METHODS: A stratified, clustered, random sampling method, with more weights given to the older age groups, was used to initially select 2000 Chinese persons aged 40 to 79 years from the 1996 electoral register in the Tanjong Pagar district in Singapore. Eligible subjects (n = 1717) were invited for a comprehensive ocular examination at a centralized clinic, after which nonrespondents were examined in their homes with portable instruments. MAIN OUTCOME MEASURES: Lens opacity, as determined clinically at the slit lamp using a modification of the Lens Opacity Classification System III. Prevalence rates were age adjusted to the 1997 Singapore census population. RESULTS: Of the 1232 persons examined (71.8%), 1206 (70.2%) provided lens data for this analysis. The age-adjusted prevalence of any cataract surgery was 5.1% (95% confidence interval [CI], 3.6, 6.5), with similar rates between men and women. The age-adjusted prevalence of specific types of lens opacity was 22.6% (95% CI, 19.8, 25.4) for any nuclear opacity, 23.9% (95% CI, 21.0, 26.8) for any cortical opacity, and 7.0% (95% CI, 5.3, 8.8) for any posterior subcapsular opacity. The overall age-adjusted prevalence of any cataract or cataract surgery was 34.7% (95% CI, 31.5, 38.0), increasing from 7.0% in those 40 to 49 years and to 94.3% in those 70 years and older (P < 0.001, test for trend for age). When the prevalence of distinct types of lens opacity in an eye was considered, the most common was mixed (age-adjusted prevalence, 11.5%, based on right eye data), followed by nuclear only (9.7%), cortical only (8.3%), and posterior subcapsular only (0.6%). For all cataract types, the prevalence was similar in men and women and was higher in persons examined at their homes than in those examined at the study clinic. CONCLUSIONS: These population-based data suggest that cataract is common among adult Chinese residents in Singapore, despite ready access to cataract surgical services. Persons accepting the offer of free eye examinations were less likely to have cataract than those who did not take up this offer.

Adult↗

PubMed2002

The epidemiology of primary angle closure and associated glaucomatous optic neuropathy.

Angle closure glaucoma is emerging as a leading cause of blindness in the densely populated countries of Asia. It has a greater propensity to cause bilateral blindness than either primary open-angle glaucoma or secondary glaucoma. An estimated 9.4 million people in China aged 40 years and older have glaucomatous optic neuropathy. Approximately 5.2 million people (55%) would be blind in at least one eye. Around 1.7 million (18.1%) would be blind in both eyes. it is likely that PACG is responsible for the vast majority (91%) of bilateral glaucoma blindness in China. The number of Chinese people with an "occludable" drainage angle is in the region of 28.2 million, and of these 9.1 million have significant angle closure. There is a growing emphasis on a revised method of classifying the disease, which reserves the term "glaucoma" for cases with glaucomatous optic neuropathy. The term primary angle closure (PAC) is used in cases with a closed angle and peripheral anterior synechiae or raised intraocular pressure. Risk factors for PAC include older age, female gender, Chinese ethnicity, all of which are associated with anatomical risk factors of central and/or peripherally shallow anterior chambers (usually associated with a thicker, anteriorly-positioned lens), and a shorter axial length of the globe.

Biometry↗

PubMed2002

The definition and classification of glaucoma in prevalence surveys.

This review describes a scheme for diagnosis of glaucoma in population based prevalence surveys. Cases are diagnosed on the grounds of both structural and functional evidence of glaucomatous optic neuropathy. The scheme also makes provision for diagnosing glaucoma in eyes with severe visual loss where formal field testing is impractical, and for blind eyes in which the optic disc cannot be seen because of media opacities.

Cross-Sectional Studies↗