Pak Sang Lee

Detection of gonioscopically occludable angles and primary angle closure glaucoma by estimation of limbal chamber depth in Asians: modified grading scheme

AIM To evaluate the performance of limbal chamber depth estimation as a means of detecting occludable drainage angles and primary angle closure, with or without glaucoma, in an east Asian population, and determine whether an augmented grading scheme would enhance test performance. METHOD A two phase, cross sectional, community based study was conducted on rural and urban areas of Hövsgöl and Ömnögobi provinces, Mongolia. 1800 subjects aged 40 to 93 years were selected and 1717 (95%) of these were examined. Depth of the anterior chamber at the temporal limbus was graded as a percentage fraction of peripheral corneal thickness. An “occludable” angle was one in which the trabecular meshwork was seen in less than 90° of the angle circumference by gonioscopy. Primary angle closure (PAC) was diagnosed in subjects with an occludable angle and either raised pressure or peripheral anterior synechiae. PAC with glaucoma (PACG) was diagnosed in cases with an occludable angle combined with glaucomatous optic neuropathy and consistent visual morbidity. RESULTS Occludable angles were identified in 140 subjects, 28 of these had PACG. The 15% grade (equivalent to the traditional “grade 1”) yielded sensitivity and specificity of 84% and 86% respectively for the detection of occludable angles. The 5% grade gave sensitivity of 91% and specificity of 93% for the detection of PACG. The interobserver agreement for this augmented grading scheme was good (weighted kappa 0.76). CONCLUSIONS The traditional limbal chamber depth grading scheme offers good performance for detecting occludable drainage angles in this population. The augmented scheme gives enhanced performance in detection of established PACG. The augmented scheme has potential for good interobserver agreement.

Prevalence of glaucoma in Thailand: a population based survey in Rom Klao District, Bangkok

Aim: To determine prevalence, demography, mechanism, and visual morbidity of glaucoma in urban Thai people. Methods: 790 subjects aged 50 years or older from Rom Klao district, Bangkok, Thailand, were enumerated in a population based cross sectional study. Each subject underwent the following investigations: visual acuity, visual field testing, slit lamp examination, applanation tonometry, gonioscopy, and an optic disc examination after mydriasis. Main outcome measures included visual acuity (logMAR), visual fields, intraocular pressure (IOP), gonioscopic characteristics, vertical cup/disc ratio (VCDR), prevalence of types of glaucoma. Glaucoma was diagnosed on the basis of optic disc appearance and visual field defects. In eyes in which the optic disc could not be examined, glaucoma was diagnosed when visual acuity was <3/60 and either IOP >99.5th percentile or there was evidence of previous glaucoma surgery. Results: 701 subjects were examined (response rate 88.7%). In eyes with “normal” suprathreshold visual fields, the mean IOP was 13.3 mm Hg (97.5th percentile = 20 mm Hg). The 97.5th and 99.5th percentiles of VCDR were 0.72 and 0.86 respectively. Of the 701 subjects examined in the clinic, 27 had glaucoma (3.8%, 95% CI: 2.5 to 5.6), 16 had primary open angle glaucoma (POAG, prevalence 2.3%, 95% CI: 1.3 to 3.7), six were primary angle closure glaucoma (PACG, prevalence 0.9%, 95% CI: 0.3 to 1.9), and five were secondary glaucoma (SecG, prevalence 0.7%, 95% CI: 0.2 to 1.7). Among the 43 unilaterally blind subjects, glaucoma was the cause in five subjects (12%). One subject was bilaterally blind due to glaucoma (prevalence 11%, 95% CI: 0.3 to 61.9). 28 people (4%) were glaucoma suspects on the basis of optic disc appearance and six on the basis of visual fields only. 98 subjects (14%) had “occludable angles” in either eye, 22 of whom had primary angle closure (PAC, prevalence 3.1%, 95% CI: 1.9 to 4.7); 14 had peripheral anterior synechiae in either eye and eight had ocular hypertension (OHT). Conclusions: POAG accounted for 67% of all glaucoma, PACG 21%, and secondary glaucomas 12%. Glaucoma was the second most common cause of severe unilateral visual loss.

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° 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 ⩽ grade 2 (approximately 20°) 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.

Trachoma in the Gambia

BACKGROUND As part of the second National Survey of Blindness and Low Vision in the Gambia carried out in 1996, all survey participants were examined for signs of trachoma. The findings were compared with the results of the first survey in 1986, which used the same sampling strategy. METHODS A multistage stratified cluster random sample, with proportional probability sampling, was obtained. Stratification included settlement size (less than 400 residents, and 400 and more residents). All subjects were examined for trachoma using the simplified WHO grading system. RESULTS Of the sample of 14 110 people, 13 047 (92.5%) were examined. Active inflammatory trachoma (grade TF or TI) was found in 3.0% of all age groups and 5.9% of children aged 0–9 years old. Trichiasis was found in 3.3% and trachomatous corneal opacities in 0.9% of adults aged 30 and over. The prevalence of blinding trachomatous corneal opacities was 0.02%, compared with 0.10% 10 years previously. CONCLUSION Compared with a previous national survey undertaken in 1986, prevalence of active trachoma has fallen by 54%. There has been an 80% relative reduction in blinding trachomatous corneal opacities over the 10 year period.

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 ⩾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 ⩾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 ⩽6/12 on presentation, 352 (23.5%) were the result of coincident disease, 800 (53.4%) refractive error and 320 (21.4%) operative complications. Eye camp surgery (OR 1.72, p = 0.002), ICCE (OR 3.78; p<0.001), rural residence (OR 1.36, p = 0.01), female gender (OR 1.55, p<0.001) and illiteracy (OR 2.44, p<0.001) were associated with VA of <6/18. More recent ICCE surgeries were associated with a poorer outcome. The ratio of ECCE+IOL:ICCE in the last 3 years was 1.2:1, compared with 1:3.3 ⩾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 Nigerian national blindness and visual impairment survey: Rationale, objectives and detailed methodology

BackgroundDespite having the largest population in Africa, Nigeria has no accurate population based data to plan and evaluate eye care services. A national survey was undertaken to estimate the prevalence and determine the major causes of blindness and low vision. This paper presents the detailed methodology used during the survey.MethodsA nationally representative sample of persons aged 40 years and above was selected. Children aged 10–15 years and individuals aged <10 or 16–39 years with visual impairment were also included if they lived in households with an eligible adult. All participants had their height, weight, and blood pressure measured followed by assessment of presenting visual acuity, refractokeratomery, A-scan ultrasonography, visual fields and best corrected visual acuity. Anterior and posterior segments of each eye were examined with a torch and direct ophthalmoscope. Participants with visual acuity of < = 6/12 in one or both eyes underwent detailed examination including applanation tonometry, dilated slit lamp biomicroscopy, lens grading and fundus photography. All those who had undergone cataract surgery were refracted and best corrected vision recorded. Causes of visual impairment by eye and for the individual were determined using a clinical algorithm recommended by the World Health Organization. In addition, 1 in 7 adults also underwent a complete work up as described for those with vision < = 6/12 for constructing a normative data base for Nigerians.DiscussionThe field work for the study was completed in 30 months over the period 2005–2007 and covered 305 clusters across the entire country. Concurrently persons 40+ years were examined to form a normative data base. Analysis of the data is currently underway.ConclusionThe methodology used was robust and adequate to provide estimates on the prevalence and causes of blindness in Nigeria. The survey would also provide information on barriers to accessing services, quality of life of visually impaired individuals and also provide normative data for Nigerian eyes.

Retinal manifestations of HIV-1 and HIV-2 infections among hospital patients in The Gambia, West Africa

Summary background In developed countries, 50–75% of AIDS patients develop retinal complications and about 20–40% acquire cytomegalavirus (CMV) retinitis. We conducted a cross‐sectional survey to determine prevalence of these in The Gambia where both HIV‐1 and HIV‐2 infection are present and the prevalence of HIV‐1 is rising.

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.

Physical activity and ocular perfusion pressure: the EPIC-Norfolk eye study.

PURPOSE To examine the relationship between physical activity and ocular perfusion pressure (OPP), a consistent risk factor for glaucoma. METHODS The relationship between previous physical activity and current OPP in 5650 participants aged 48 to 90 who attended the first (1993-1997) and third (2006-2010) health check as part of the European Prospective Investigation into Cancer (EPIC)-Norfolk study was examined. Usual combined physical activity at work and leisure was assessed using a validated instrument. Individuals were categorized as inactive, moderately inactive, moderately active, or active. Three IOP measurements were obtained (Ocular Response Analyzer [ORA]; Reichert, Inc., Depew, NY). Mean Goldmann correlated IOP (IOPg) from one eye was used in the analysis. Systolic and diastolic blood pressure (BP) were recorded as the mean of two measurements taken with a sphygmomanometer. Associations between physical activity and low (≤40 mm Hg) mean OPP (2/3 mean arterial pressure - IOP) and low (≤50 mm Hg) diastolic OPP (diastolic BP - IOP) were tested using logistic regression, adjusting for age, sex, body mass index, social class, IOP, and BP. RESULTS Active people had a lower risk of mean OPP ≤ 40 mm Hg and diastolic OPP ≤ 50 mm Hg after adjusting for age, sex, social class, and body mass index (odds ratio, 0.75; 95% confidence interval [CI], 0.60-0.93; P < 0.01) and (odds ratio, 0.73, 95% CI, 0.58-0.93; P = 0.01), respectively. The association between physical activity and perfusion pressure was independent of IOP, but largely mediated through diastolic BP. CONCLUSIONS Lower levels of physical activity were associated with lower OPP. Further research is needed to investigate the potential benefit of increased physical activity as a safe and simple method of modifying glaucoma risk.

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.