Gus Gazzard

The LiGHT trial (Laser-1st versus Drops-1st for Glaucoma and Ocular Hypertension Trial) is a multicentre randomised controlled trial of two treatment pathways for patients who are newly diagnosed with open-angle glaucoma (OAG) and ocular hypertension (OHT). The main hypothesis for the trial is that lowering intraocular pressure (IOP) with selective laser trabeculoplasty (SLT) as the primary treatment ('Laser-1st') leads to a better health-related quality of life than for those started on IOP-lowering drops as their primary treatment ('Medicine-1st') and that this is associated with reduced costs and improved tolerability of treatment. This paper describes the statistical analysis plan for the study. The LiGHT trial is an unmasked, multi-centre randomised controlled trial. A total of 718 patients (359 per arm) are being randomised to two groups: medicine-first or laser-first treatment. Outcomes are recorded at baseline and at 6-month intervals up to 36 months. The pri...

To describe the optic disc, visual field and ocular characteristics of a consecutive cohort of Asian patients with chronic primary angle-closure glaucoma (CPACG), and compare them with those having primary open-angle glaucoma (POAG). In a prospective comparative case series of new patients with POAG or CPACG in Singapore, all patients underwent visual acuity assessment, slit-lamp examination, tonometry, gonioscopy, refraction, Heidelberg Retina Tomograph (HRT) and Humphrey visual field (HVF) assessment. 98 patients were enrolled (POAG n = 48; CPACG n = 50). CPACG patients were significantly older (66.5 ± 9.2 years vs. 64.1 ± 13.5 years; p = 0.027) and mostly female (p = 0.004). CPACG eyes had significantly higher intraocular pressure (26.9 ± 6.9 mmHg vs. 24.5 ± 3.3 mmHg; p = 0.03), shorter axial length (22.89 ± 0.97 mm vs. 24.26 ± 1.79 mm; p < 0.001) and shallower anterior chamber depth (2.60 ± 0.25 mm vs. 3.16 ± 0.48 mm; p < 0.001). HVF mean deviation or pattern standard deviation (PSD) did not differ significantly between POAG and CPACG eyes, but the latter had a lower PSD for a given mean deviation. HRT parameters between the two groups were not significantly different. In this study, CPACG eyes had significantly higher presenting intraocular pressure than POAG eyes, but there were no significant differences in optic disc topography. A majority of the patients in both groups had moderate field defects at the time of presentation, followed by severe and then mild defects. The field loss in CPACG eyes was more diffuse than that in POAG eyes.

To assess the interventions to treat acute angle closure (AAC) and primary angle closure (PAC) with or without glaucomatous optic neuropathy. Primary angle closure is one of the leading causes of blindness in East Asia. At present, there are few clinical guidelines on the optimal treatment of AAC or PAC in the affected or contralateral eye. All randomized clinical trials, prospective controlled clinical trials, nonprospective controlled clinical trials, and retrospective case series with >50 cases that evaluated treatments for AAC or PAC were included. Studies published in the English language were identified from MEDLINE, PubMed, EMBASE, and the Cochrane Collaborations, as well as by a hand search of the reference lists of important articles. Nine randomized clinical trials and 24 nonrandomized clinical trials and large case series were evaluated. Laser peripheral iridotomy (LPI) has been found to be as effective as surgical peripheral iridectomy in randomized clinical trials of the affected and contralateral eyes of AAC or PAC patients with or without evidence of glaucoma. In another randomized clinical trial, latanoprost was found to decrease intraocular pressure (IOP) more than timolol for PAC in patients for whom LPI alone failed. This review suggests that LPI should be recommended for the treatment of affected and contralateral eyes of AAC patients. In patients with PAC and insufficient treatment with LPI, latanoprost eye drops may decrease IOP more than timolol. There is still insufficient evidence about other interventions for the treatment of AAC and PAC.

To evaluate the measurement of optic disc morphology using Heidelberg Retinal Tomography (HRT) with and without the aid of optic disc photos. One hundred three children (aged 11 and 12 y, 52 boys) were selected randomly from the Singapore Cohort study of Risk Factors for Myopia. Optic nerve head topography and retinal nerve fiber layer thickness measurements were assessed using the HRT-II (Heidelberg, Germany) scanning laser ophthalmoscope. All contour lines were drawn by the same researcher on 2 occasions. The first drawing was made without optic disc photographs but using the 3-dimensional rotation assessment. The second drawing was made with the additional aid of digital monoscopic optic disc photographs. There was a high correlation between the measurements taken with and without optic disc photographs. For the global disc area, the difference between the mean readings was 0.67 mm and the intraclass correlation (ICC) was 0.81 [95% confidence interval (CI) 0.73-0.86]. The mean difference for the global cup-to-disc ratio was 0.03 [ICC 0.86 (95% CI 0.80-0.90)]. The ICCs were high across almost all of the readings except rim volume, in which the ICC was 0.57 (95% CI 0.43-0.69). This study shows minimal differences in HRT measured optic disc parameters when optic disc photos are used to aid in the definition of the scleral ring. Omitting the use of disc photographs in measuring HRT outputs may translate into significant savings in time and logistics in simultaneously obtaining HRT and optic disc photographs in large population-based studies.

Methods The study population was taken from all children in grades 1 to 3 of a single junior school in Singapore in 2001, with an 80.2% participation rate. Children with congenital eye disorders were excluded. We conducted a cross-sectional analysis of this cohort in May ...

To systematically examine the association between ocular biometry and retinal vascular caliber in Singapore Chinese preschoolers aged 48 to 72 months. A total of 469 Singapore Chinese children aged 48 to 72 months were recruited through the Strabismus, Amblyopia and Refractive Error Study in Singaporean Chinese Preschoolers (STARS) from 2006 to 2008. According to standardized protocols, cycloplegic autorefraction, ocular biometry measurements, and retinal photography were performed. Retinal vascular caliber was measured quantitatively and was summarized as the central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE), respectively. Ocular magnification was corrected by using the Bengtsson formula. The mean retinal arteriolar and venular calibers were 156.08 μm and 219.55 μm in boys, and 161.96 μm and 224.25 μm in girls, respectively. In multiple linear regression adjusted for age, sex, father's education, parental myopia history, mean arterial blood pressure, body mass index, and spherical equivalent, each 1.0 mm increase in axial length was associated with a 3.52 μm decrease in retinal arteriolar caliber (P = 0.023) and a 5.55 μm decrease in retinal venular caliber (P = 0.008). Each 1.00 mm increase in corneal curvature was associated with a 13.79 μm decrease (P = 0.004) in retinal venular caliber. In very young children aged 48 to 72 months, narrower retinal arteriolar and venular caliber was associated with elongated axial length. Narrower retinal venular caliber was associated with larger corneal curvature. This suggests that the major structural correlate of myopia might have an effect on retinal microvasculature from early childhood.

To examine the relationship between corneal biomechanical properties and retinal vascular caliber in Singaporean children in a cross-sectional study of 257 healthy subjects from the Singapore Cohort Study of Risk Factors for Myopia. Corneal hysteresis (CH), corneal resistance factor (CRF), central corneal thickness (CCT), and corneal compensated intraocular pressure (IOP(CC)) were measured with a patented dynamic bi-directional applanation device. Digital retinal photography was performed, and retinal vascular caliber was measured with custom software. The central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) were calculated, representing the average arteriolar and venular calibers. Spherical equivalent (SE) refraction, axial length, height, weight, and mean arterial blood pressure (MABP) were measured. Mean values of this study were as follows: age of study subjects, 13.97 +/- 0.90 years; CH, 11.80 +/- 1.55 mm Hg; CRF, 11.83 +/- 1.72 mm Hg; CCT, 578.76 +/- 34.47 microm; IOP(CC), 15.12 +/- 2.84 mm Hg; CRAE, 151.70 +/- 15.54 microm; CRVE, 227.51 +/- 22.82 microm. After controlling for age, sex, ethnicity, body mass index, father's educational level, MABP, IOP, and SE, there was a significant increase in CRAE by 1.40 microm (95% CI: 0.17-2.61; P = 0.03) for every 1.55 mm Hg increase in CH and by 1.68 microm (95% CI: 0.21-3.15; P = 0.03) for every 1.72 mm Hg increase in CRF. There were no significant associations between CRVE and CH, CRF, CCT, or IOP. Lower CH and CRF are associated with narrower retinal arterioles in Singaporean children.

Peripheral hyperopia was hypothesized to stimulate axial elongation. This study describes peripheral refraction and its associations with central refractive error in young Singapore Chinese children. Two hundred fifty children aged 40 months or older recruited from the Strabismus, Amblyopia, and Refractive Error in Young Singapore Children study were included in this analysis. Peripheral refraction was measured after pupil dilation using an infrared autorefractor. A total of five measurements were captured: central visual axis and 15° and 30° eccentricities in the nasal and temporal visual fields. The mean age of the participants recruited was 83 ± 36 months. There were 37 children with high and moderate myopia (≤-3 D; 14.8%), 81 with low myopia (-2.99 to -0.5 D; 32.4%), 84 with emmetropia (-0.49 to 1.0 D; 33.6%), and 47 with hyperopia (>1.0 D; 18.8%). Compared with the central axis, children with high and moderate myopia had relative hyperopia at all peripheral eccentricities (P < 0.001), whereas children with low myopia had relative hyperopia only at the temporal and nasal 30° (P < 0.001), but not at the nasal and temporal 15°. Children with emmetropia and hyperopia had peripheral relative myopia at all eccentricities (P < 0.001). A significant correlation between the nasal and temporal refractive error at 30° was noted (Spearson's correlation coefficient = 0.85, P < 0.001). Young myopic Singapore Chinese children had relative hyperopia in the periphery. This study substantiates previous studies in older children and in Caucasian subjects.

1. Eye (Lond). 2001 Apr;15(Pt 2):234-5. Surgical exploration minimised by ultrasound biomicroscopy localisation of intraocular foreign body. Looi AL, Gazzard G, Tan DT. PMID: 11339601 [PubMed - indexed for MEDLINE]. Publication Types: Case Reports; Letter. MeSH ...

Purpose To determine the corneal biomechanical parameters measured with the Reichert Ocular Response Analyser (ORA) in Singaporean children, and to assess their correlations with refractive error and biometry Methods This was a cross sectional study of 271 subjects from the Singapore Cohort Study of Risk Factors for Myopia (SCORM). Corneal hysteresis (CH), corneal resistance factor (CRF), central corneal thickness (CCT) and intraocular pressure (IOPcc) were measured with the ORA. Spherical equivalent refraction, axial ...

To compare the characteristics of visual field defects in primary angle-closure glaucoma (PACG) and primary open-angle glaucoma (POAG). 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. 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. 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.

To determine the prevalence rates and causes of low vision, blindness, and patient-assessed deficient visual function among Singaporean Chinese adults. Population-based cross-sectional survey. Singaporean Chinese adults 40 to 79 years old (n = 1152). 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. 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. 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. 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.

To determine the long-term outcome of Asian eyes with an acute attack of primary angle closure (APAC) and to identify risk factors at presentation associated with the development of glaucomatous optic nerve damage. Cross-sectional observational case series. Ninety individuals who were initially seen with APAC 4 to 10 years previously at 2 Singapore hospitals. All subjects underwent a complete eye examination, including visual acuity, visual field testing, dilated eye examination, and optic nerve head photography. The optic discs were judged clinically and photographically as to whether there was glaucomatous optic neuropathy present, and visual fields were assessed for corresponding visual field loss. All visual fields and optic nerve photographs underwent a second evaluation by an experienced, but masked, glaucoma specialist, who assessed whether the changes were compatible with glaucoma. The main outcome measures were blindness (defined as best-corrected visual acuity worse than 6/60 and/or central visual field of less than 20 degrees in the attack eye) and glaucomatous optic neuropathy (GON). A total of 90 of 170 eligible subjects (65.2%) were examined. All subjects were Asian and were predominantly Chinese (78 subjects [86.7%]). There were 61 females (67.8%), and the age of the subjects was 62.0+/-9.0 years (mean +/- standard deviation) at the time of APAC, with a mean duration of 6.3+/-1.5 years from the time of the APAC episode to the study examination. Sixteen (17.8%) subjects were blind in the attack eye; half of the cases of blindness were caused by glaucoma. Forty-three subjects (47.8%) had GON, with 13 eyes (15.5%) having markedly cupped optic discs (cup-to-disc ratio >0.9). Thirty-eight eyes (58%) had best-corrected vision worse than 6/9, with cataract responsible for close to half the cases of poor vision. There were no identifiable risk factors related to the APAC episode that were significantly associated with the presence of GON. Several years after being seen with APAC, 17.8% of subjects examined were blind in the attack eye, and almost half had glaucomatous optic nerve damage. Vision was also reduced in a large number of individuals, largely from unoperated cataract. Subjects with APAC would benefit from regular follow-up to monitor for visual field decline and glaucoma development.

To evaluate the possible associations between dietary factors and myopia. Cross-sectional study. Eight hundred fifty-one Chinese schoolchildren from the Singapore Cohort Study of Risk Factors for Myopia. Diet was assessed using a semiquantitative food-frequency questionnaire. Spherical equivalent (SE) refraction was assessed with an autorefractometer, and axial length (AL) by contact ultrasound A-scan biometry. Myopia was defined as SE< or =-0.5 diopters (D). Spherical equivalent and AL were analyzed by quartile groups. The mean age (+/-standard deviation) was 12.81+/-0.83 years, approximately half were male (422 children [49.6%]), and 653 (73.8%) children had myopia. In multivariate models, AL was longest in the highest quartile group of total cholesterol intake compared with the lowest (adjusted mean [95% confidence interval], 24.66 [24.62-24.71] mm vs. 24.32 [24.27-24.36] mm; P = 0.026, for trend) and was longest in the highest quartile group of saturated fat intake compared with the lowest (24.65 [24.60-24.70] vs. 24.36 [24.32-24.41] mm; P = 0.039, for trend). None of the nutrients was associated with SE or a diagnosis of myopia. Higher saturated fat and cholesterol intake are associated with longer AL in otherwise healthy Singapore Chinese schoolchildren.

This study compares the repeatability of IOLMaster (Zeiss, Oberkochen, Germany) axial dimension measurements and conventional ultrasonography in children. A series of IOLMaster (partial coherence interferometry, optical pachometry) and Echoscan (US 800, Nidek, Tokyo, Japan) (ultrasound) measurements were taken on 179 Chinese children (mean age, 10.6 +/- 0.8 years) taking part in a longitudinal study of myopia development, and the measurements were repeated on 37 of these subjects. IOLMaster axial length measurements showed better repeatability (95% limits of agreement for repeatability, -0.047 to 0.038 mm) than Echoscan axial length measurements (95% limits of agreement for repeatability, -0.85 to 0.67 mm). IOLMaster anterior chamber depth measurements also showed better repeatability (95% limits of agreement for repeatability, -0.053 to 0.073 mm) than Echoscan anterior chamber depth measurements (95% limits of agreement for repeatability, -0.57 to 0.49 mm). IOLMaster measurements were, on average, slightly larger than Echoscan measurements for axial length (by 0.14 mm) and anterior chamber depth (0.09 mm). Partial coherence interferometry techniques, such as that used by IOLMaster, should be considered as the standard technique for axial length measurement in children because they are noninvasive, highly precise, and easy to use.

PURPOSE: To evaluate the changes in retinal nerve fiber layer (RNFL) thickness in the first 16 weeks after acute primary angle closure (APAC) using scanning laser polarimetry (SLP). DESIGN: Prospective, observational case series. PARTICIPANTS: Thirty-seven Asian ...

To determine the intermediate-term efficacy and safety of Baerveldt glaucoma implants in Asian eyes with complicated glaucoma. Retrospective, nonrandomized, comparative trial. One hundred twenty-four Asian patients (124 eyes) with complicated glaucoma. Implantation of 54 250-mm(2) and 70 350-mm(2) Baerveldt glaucoma drainage implants at Singapore National Eye Center from 1994 through 1999. Intraocular pressure, number of glaucoma medications, and complications. The mean follow-up period was 33.4 +/- 14.4 months (mean +/- SD; range, 12-72 months). Intraocular pressure (IOP) was reduced from a mean preoperative IOP of 36.5 +/- 10.7 mmHg (range, 21-80 mmHg) to 15.3 +/- 6.0 mmHg (range, 1-34 mmHg), and the number of glaucoma medications decreased from 2.6 +/- 0.6 (range, 1-5) before the time of surgery to 0.5 +/- 0.9 (range, 0-4) medications at last follow-up. Overall, there were 67 eyes (54%) that were classified as complete successes, 27 eyes (22%) that were qualified successes, and 30 eyes that failed (24%). Postoperative complications occurred in 43 eyes (34.7%), and 21 eyes (17%) required further surgical intervention and revision. There was no statistically significant difference between the 250-mm(2) and 350-mm(2) type of implants in terms of success rates, final IOP, number of medications, and rates of complications. After adjusting for gender, preoperative IOP, and length of follow-up, increasing age (odds ratio [OR], 1.05; 95% confidence interval [CI], 1.01-1.09; P = 0.02) and the number of previous operations performed before implant surgery (OR, 1.57; 95% CI, 1.07-2.31; P = 0.01) were found to be correlated positively with failure. In Asian eyes with complicated glaucoma, Baerveldt glaucoma implants achieve stable and satisfactory IOP reduction with low incidence of complications in the intermediate term after surgery.

To study the prevalence of undercorrected refractive error and associated sociodemographic factors among Singaporean Chinese adults. Cross-sectional, population-based survey. Singaporean Chinese adults aged 40 to 79 years (n = 1152). 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. Undercorrected refractive error was defined as improvement of better eye visual acuity of at least 2 lines or more with best possible refractive correction. 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. The undercorrected refractive error rate among Singaporean Chinese is relatively common compared with data from other populations.

To examine early myopia-related optic disc and retinal changes in a Singapore Chinese adolescent sample without confounding ocular or systemic disease. Population-based cross-sectional study. Children aged 12 to 16 years at a follow-up visit for Singapore Cohort Study of Risk Factors for Myopia. Detailed eye examinations, including cycloplegic autorefraction and contact biometry, were performed. Retinal photographs were acquired using nonmydriatic retinal photography among children who attended follow-up examinations in 2006, and were graded for myopia-related optic disc signs and macular changes by a single experienced grader. Optic nerve head parameters were measured adjusting for camera and ocular magnification with appropriate formulae. Optic disc changes (tilt, beta peripapillary atrophy [β-PPA], and optic nerve parameters) and macular changes (staphyloma, lacquer cracks, Fuchs' spot, and chorioretinal atrophy). Retinal photography data were available for 1227 children (median age, 14 years; range 12-16). Tilted optic discs were found in 454 subjects (37%), and were associated with myopic spherical equivalent refractions (-3.6 diopters [D] vs -1.3 D; P<0.0001), higher cylindrical error (0.9 vs 0.7 D; P = 0.0001) and longer axial length (24.93 vs 23.96 mm; P<0.0001). The pattern of distribution of the axes of the tilted discs and corneal curvature were similar (P = 0.4). All linear optic nerve parameters, except vertical disc diameter (P = 0.15), were significantly smaller in eyes with than without tilted discs (P <0.001) after adjusting for confounders. Apart from 20 cases, all eyes with tilted optic discs had associated β-PPA. We identified only 1 case each (0.1% prevalence) of staphyloma and lacquer cracks in this sample. In this Asian adolescent population, tilted optic discs were highly prevalent, in contrast with the lower prevalence reported in Caucasian populations. Eyes with tilted discs tended to have smaller optic cups with smaller cup-to-disc ratios, and were associated with myopic refraction, higher astigmatism, and longer axial length. There were similar patterns of distribution between the axis of disc tilt and the axis of corneal curvature, which could have embryologic origins. In contrast with optic disc changes, myopic macular changes were rare in this age group, suggesting that these changes may develop later in life. The authors have no proprietary or commercial interest in any of the materials discussed in this article.