Primary angle closure glaucoma in East Asia: educational attainment as a protective factor.

PURPOSE: To examine the relationship between education, other risk factors and incident primary angle closure glaucoma (PACG). METHOD: Glaucoma was excluded in a group of 4597 Mongolian volunteers in 1999. After 6 years, 1892 traced participants had full ophthalmic examination, dilated disc photographs and agreed to complete a questionnaire on socio-economic status. PACG was diagnosed using both structural and functional evidence from objective grading of paired disc photographs, follow up visual fields and clinical examination. Ophthalmic examination included van Herick grading, Goldmann intraocular pressure (IOP), gonioscopy, lens opacity grading and dilated disc examination. Central anterior chamber depth, lens thickness and axial length were recorded using ultrasound A scan mounted on a slitlamp. Education level was assessed using national census categories. RESULTS: PACG was diagnosed in 29 participants (6 year incidence = 1.53%, 95% confidence interval (CI) = 1.03-2.19%). In univariate analysis, risk factors for incident PACG included presence of refractive error, narrow van Herick grading of ≤15%, narrower average Shaffer grading, higher IOP, larger cup disc ratio and lower levels of education. In multivariate analysis, adjusted for age, sex, Shaffer grading, refractive error and IOP, those with no formal education were approximately 7 times more likely to develop PACG compared to those with >8 years of formal schooling (OR = 7.27, 95% CI = 2.73-19.38). CONCLUSIONS: People with lower levels of education have a higher risk of incident PACG, independent of age, sex, IOP and axial length.

Randomised controlled trial of screening and prophylactic treatment to prevent primary angle closure glaucoma.

AIMS: To determine if screening with an ultrasound A-scan and prophylactic treatment of primary angle closure (PAC) with laser peripheral iridotomy (LPI) can reduce the incidence of primary angle closure glaucoma (PACG) in Mongolia. METHODS: A single-masked randomised controlled trial was initiated in 1999. 4725 volunteer Mongolian participants ≥ 50 years old from the capital Ulaanbaatar or the rural province of Bayankhongor were recruited, of which 128 were excluded with glaucoma. 4597 were randomly allocated to the control, no-screening arm or screening with ultrasound central anterior chamber depth (cACD), with the cut-off set at < 2.53 mm. 685 screen-positive participants were examined and angle closure was identified by gonioscopy in 160, of which 156 were treated with prophylactic LPI. Primary outcome of incident PACG was determined using both structural and functional evidence from objective grading of paired disc photographs from baseline and follow-up, objective grading of follow-up visual fields and clinical examination. RESULTS: Six years later, 801 (17.42%) participants were known to have died, and a further 2047 (53.92%) were traced and underwent full ophthalmic examination. In an intention to treat analysis using available data, PACG was diagnosed in 33 participants (1.61%, 95% CI 1.11% to 2.25%), of which 19 were in the screened group and 14 in the non-screened group (OR 1.29, 95% CI 0.65 to 2.60, p = 0.47), indicating no difference between groups. CONCLUSIONS: We were not able to identify a reduction in the 6 year incidence of PACG after screening with cACD < 2.53 mm and prophylactic treatment of PAC.

Comparison of central corneal thickness using anterior segment optical coherence tomography vs ultrasound pachymetry.

PURPOSE: To determine if there is a systematic difference in central corneal thickness (CCT) measured using anterior segment optical coherence tomography (AS-OCT) as compared with ultrasound pachymetry. DESIGN: Prospective observational study. METHODS: Consecutive subjects with clinically normal corneas underwent CCT measurement by both ultrasound and AS-OCT while participating in a population-based study in Ghana, West Africa. One eye of each subject was randomly selected for analysis. Two measurements were taken and averaged. Agreement and interobserver variability were also analyzed. RESULTS: One hundred and fifty-five subjects of African ethnicity and average age 57 years (standard deviation [SD] 12; range, 40 to 98 years) were included. Measurements by AS-OCT and US were taken a mean of 15 days (maximum, six weeks) apart. The mean (SD) [range] US CCT was 525.3 microm (33.5) [422, 653] and 499.0 microm (32.0) [428, 613] with AS-OCT. Measurements by the two modalities were strongly correlated (r(2) = 0.82; P < .001), and a significant difference was observed between mean US and AS-OCT CCT (SD) [range] of 26.3 microm (14.2) [-63, 12] (P < .001). The width of the limits of agreement was 28 microm, about 6% of the average pachymetry reading. In 50 eyes randomly remeasured with OCT by a second observer, the intraclass correlation coefficient was 0.91. There was a small but significant systematic difference between observers (mean 6.9 microm, SD 10.9 microm), or 1.4% (P < .001), increasing the difference noted above. CONCLUSION: There is a reproducible systematic difference between CCT measurements taken with ultrasound and OCT. It is important to note in clinical practice, that measurements acquired by these two modalities are not directly interchangeable.

Outcomes of cataract surgery in Pakistan: results from The Pakistan National Blindness and Visual Impairment Survey.

AIM: To evaluate the outcomes of cataract surgery in Pakistan. METHODS: Cross-sectional, nationally representative sample of 16 507 adults (aged >or=30 years). Each underwent interview, logarithm of the minimum angle of resolution visual acuity (VA), autorefraction, examination of optic disc. Those with <6/12 VA on presentation underwent best-corrected VA and dilated biomicroscopic ocular examination. RESULTS: 1317 subjects (633 men) had undergone surgery in one or both eyes. Of the 1788 operated eyes, 1099 (61%) had undergone intracapsular cataract extraction (ICCE) and 607 (34%) extracapsular surgery with an intraocular lens (ECCE+IOL). Presenting VA: 275 (15.4%) eyes: 6/12 or better; 253 (14.1) <6/12 >or=6/18; 632 (35.3%) 6/18 to 6/60; 85 (4.8%): 6/60 to 3/60; 528 (29.5%): <3/60. With "best" refractive correction, these values were: 563 (31.5%), 332 (18.6%), 492 (27.5%), 61 (3.4%), 334 (18.7%), respectively. Of the 1498 eyes with VA or=4 years before the survey. CONCLUSION: Almost a third of cataract operations result in a presenting VA of <6/60, which could be halved by appropriate refractive correction. This study highlights the need for an improvement in quality of surgery with a more balanced distribution of services.

The Pakistan national blindness and visual impairment survey--research design, eye examination methodology and results of the pilot study.

PURPOSE: To establish age- and sex-specific prevalence rates and causes of blindness and low vision in children aged 10 to 15 years and adults aged 30 years and older in Pakistan. METHODS: Multi-stage, stratified (rural/urban), cluster random sampling, with probability proportional-to-size procedures, was utilised to select a cross-sectional, nationally representative sample of adults (16,600 subjects) and children (6,000 subjects). Each subject underwent: interview, visual acuity (logMAR), autorefraction and optic disc examination. Those that saw < 6/12 in either eye underwent corrected visual acuity and dilated posterior segment examination. RESULTS: The results of a pilot survey are reported in this paper. In the two rural pilot sites, 159 subjects (including 47 children) were examined; 50% were male. Thirty seven adults (23.3%) but no children saw worse than 6/12 in either eye. Two subjects were blind (corrected visual acuity) in the better eye, and 11 were visually impaired. Refractive error was the main cause (in 22 eyes (39% of the total of 56 eyes)) of < 6/12 visual acuity, followed by cataract (12 eyes), uncorrected aphakia (6 eyes) and age-related macular disease (3 eyes). CONCLUSIONS: The pilot survey demonstrated that the proposed examination process for the main survey is feasible. Particular strengths of this survey include the use of logMAR visual acuity testing and autorefraction of all subjects, a dilated posterior segment examination, and the use of a 'less than 6/12' threshold for further examination. This lower threshold addresses the burden of refractive error, which, with cataract, are two of the diseases specifically targeted by Vision 2020.