To describe the relationship of refractive errors and axial ocular dimensions and age-related cataract.
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.
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.
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.
To examine the association between central corneal thickness (CCT) and glaucoma.
This was a nested case-control study using 1090 subjects from an eye disease population survey in Singapore and 243 ...participants from a hospital glaucoma surgery clinical trial in Singapore.
Mean CCT in 938 community subjects was 539 μm ± 32 μm, and in 12 community subjects with primary open angle glaucoma (POAG) the mean CCT was 545 μm ± 38 μm. In the hospital cohort, mean CCT was 552 μm ± 38 μm in 138 patients with POAG and 551 μm ± 33 μm in 105 patients with primary angle closure glaucoma (PACG). No individuals had undergone previous intraocular surgery or had other significant ocular pathology. Regression models showed POAG diagnosis was not associated with CCT (P = 0.42) or age (P = 0.062) in community subjects but was associated with IOP (P = 0.005). Similar analyses for hospital cases showed CCT to be significantly higher in both POAG and PACG (both P = 0.001), but this became nonsignificant after controlling for IOP and age (P = 0.26, POAG; P = 0.08, PACG). Both age (P = 0.043) and IOP (P = 0.001) were highly associated with hospital POAG; only IOP (P = 0.001) was associated with hospital PACG. Further regression analyses for community subjects showed diabetic status and pseudophakia had no significant effect on CCT (P = 0.33 and P = 0.11, respectively).
The authors found no evidence to support the previous observation that thinner corneas may be independently associated with POAG or PACG. Age and IOP are significantly associated with CCT, and this should be taken into account by future studies investigating CCT as an independent risk factor for glaucoma diagnosis.
To determine the relationship between peripapillary retinal nerve fiber layer (RNFL) thickness and myopia using optical coherence tomography (OCT).
Prospective observational case series.
One hundred ...thirty-two young males with myopia (spherical equivalent SE, -0.50 to -14.25 diopters) underwent ophthalmic examination of one randomly selected eye. Optical coherence tomography (OCT-1, version 4.1) was performed by a single operator using circular scans concentric with the optic disc with scan diameters of 3.40 mm, 4.50 mm, and 1.75 x vertical disc diameter (VDD). For each scan diameter, mean peripapillary RNFL thickness was calculated. Statistical analysis comprised repeated-measurements analysis and Pearson correlation.
Mean peripapillary RNFL thickness did not correlate with SE for the 3.40-mm (r = -0.11, P = 0.22), 4.50-mm (r = -0.103, P = 0.24), or 1.75xVDD (r = -0.08, P = 0.36) OCT scan diameters. Neither did mean peripapillary RNFL thickness correlate with axial length for the 3.40-mm (r = -0.04, P = 0.62), 4.50-mm (r = 0.03, P=0.75), or 1.75xVDD (r = -0.02, P = 0.78) scan diameters. Mean peripapillary RNFL thicknesses for the 3.40-mm, 4.50-mm, and 1.75xVDD scans were 101.1+/-8.2 microm (95% confidence interval CI, 99.4-102.8), 78.9+/-8.2 microm (95% CI, 77.5-80.3), and 97.5+/-10.9 microm (95% CI, 95.6-99.4), respectively.
Mean peripapillary RNFL thickness did not vary with myopic SE or axial length for any OCT scan diameter investigated. Retinal NFL thickness measurements may be a useful parameter to assess and monitor glaucoma damage in myopic subjects.
Aim: To compare anterior chamber depth measurements by three non-contact devices—the IOLMaster, scanning peripheral anterior chamber depth analyser (SPAC), and Visante anterior segment optical ...coherence tomography (AS-OCT) Methods: Prospective, cross sectional study of 497 phakic subjects over 50 years of age attending a community clinic in Singapore. Anterior chamber depth of the right eye was measured using all three techniques by the same investigator. Depth measurements were made from the corneal epithelium to the anterior lens surface. The values obtained were compared using Bland–Altman analysis. Results: 232 men and 265 women were examined (mean (SD) age, 63.4 (7.9) years). Mean anterior chamber depth was 3.08 (0.36) mm with IOLMaster, 3.10 (0.44) mm with SPAC, and 3.14 (0.34) mm with AS-OCT. A significant difference was present between the anterior chamber depth measurements recorded by the three devices (p<0.0001). Mean differences between the measurements were: AS-OCT v IOLMaster, 0.062 (0.007) mm (95% limits of agreement, −0.37 to 0.25 mm) (p<0.0001); AS-OCT v SPAC, 0.035 (0.011) mm (−0.44 to 0.51 mm) (p = 0.0001); SPAC v IOLMaster, 0.027 (0.012) mm (−0.57 to 0.50 mm) (p = 0.027). Conclusions: AS-OCT gave systematically deeper anterior chamber measurements than SPAC and IOL-Master. However, as the differences found were small they are unlikely to be clinically important.
To report the 8-year outcomes of Asian subjects who underwent trabeculectomy augmented by intraoperative 5-fluorouracil (5-FU) or placebo.
Retrospective review of a randomized controlled trial.
...Subjects with primary open-angle or angle-closure glaucoma.
Study subjects were prospectively followed up for 3 years. After the last subject recruited had completed 8 years of follow-up, the charts of all subjects were reviewed to capture data from the year 3 visit onward. Kaplan-Meier survival function with Cox regression was performed to identify risk factors associated with trabeculectomy failure at 8 years.
The primary outcome was trabeculectomy failure defined as intraocular pressure (IOP) >21 or <6 mmHg on 2 consecutive occasions after the first 6 weeks after surgery, repeat glaucoma surgery, or loss of light perception. Further end points were defined at IOP levels >17 and >14 mmHg. Secondary outcomes included IOP at 8 years and number of glaucoma medications. Complete success was defined using IOP end points ≤ 21, ≤ 17, or ≤ 14 mmHg at 8 years without medications.
Of the 243 enrolled subjects, 170 (70.0%) completed 8 years follow-up, 86 in the 5-FU and 84 in the placebo group. There was no significant difference in failure rates at 8 years for the failure definitions of IOP >21 mmHg (11.6% of the 5-FU group vs. 16.7% of the placebo group; P = 1.00), IOP >17 mmHg (23.3% of the 5-FU group vs. 31% of the placebo group; P = 0.78), and IOP >14 mmHg (46.5% of the 5-FU group vs. 58.3% of the placebo group; P = 0.37). Mean IOP at 8 years was 13.7 mmHg in the 5-FU versus 14.4 mmHg in the placebo group (P = 0.24). Mean number of medications was 0.65 drops in the 5-FU versus 0.93 drops in the placebo group (P = 0.06). Complete success with IOP ≤ 21 mmHg at 8 years was achieved in 48 subjects (55.8%) in the 5-FU and 33 subjects (39.3%) in the placebo group (P = 0.09). Absence of bleb microcysts at 1 year, preoperative IOP, and number of bleb needlings performed within the first year were significantly associated with failure.
There was no significant difference in IOP between the 5-FU and the placebo group at 8 years.
The author(s) have no proprietary or commercial interest in any materials discussed in this article.
Aim: To determine the changes in peripapillary atrophy after episodes of acute primary angle closure (APAC). Methods: Prospective observational study of 40 eyes in 38 patients of predominantly ...Chinese ethnicity. The mean (SD) intraocular pressure at the time of presentation was 51.7 (12) mm Hg (median, 55 mm Hg) and the mean duration of the symptoms was 37.7 (69.4) hours. A laser iridotomy was undertaken 3.2 (8.4) days after the APAC episode, leading to normalisation of intraocular pressure in all cases. Colour optic disc photographs taken at 2 and 16 weeks after APAC were examined morphometrically. Peripapillary atrophy was divided into α and β zones. Results: Comparing measurements at baseline with week 16, the minimum width of the α zone (0.013 (0.056) v 0.016 (0.001) arbitrary units; p = 0.23), the maximum width of the α zone (1.11 (1.31) v 1.31 (0.79) arbitrary units; p = 0.22), the minimum width of the β zone (0.030 (0.122) v 0.033 (0.166) arbitrary units; p = 0.93), and the maximum width of the β zone (0.62 (0.94) v 0.73 (0.98) arbitrary units; p = 0.42) did not vary significantly. The mean cup to disc ratio increased from 0.56 (0.05) to 0.62 (0.07) (p<0.0001) at the end of follow up. Conclusions: The α and β zones of peripapillary atrophy did not enlarge markedly in patients after APAC, despite an enlargement of the optic cup during a follow up of four months.
To evaluate changes in lens opacity in the first year after prophylactic laser peripheral iridotomy (LPI) performed in fellow eyes of subjects with acute primary angle closure (APAC).
Prospective ...observational case series.
Sixty Asian subjects with unilateral APAC.
All fellow eyes underwent prophylactic LPI within the first week of presentation, followed by 1 week of topical steroids. The degree of lens opacity was graded at the slit-lamp examination using the Lens Opacity Classification System III (LOCS III) with standard color photographs as the reference for grading of lens opacity. This was performed 2 weeks, 4 months, and 12 months after LPI. Progression in lens opacity was defined as an increase in LOCS III grade by 2 or more units in any lens region.
Lens Opacity Classification Sytem III grades in nuclear, cortical, and posterior subcapsular (PSC) regions.
Most patients were Chinese (85%) and female (63.3%), with an average age of 61.5 +/- 10.6 years. The mean baseline LOCS grades in the nuclear, cortical, and PSC regions were 3.58 +/- 0.74, 0.57 +/- 1.08, and 0.23 +/- 0.72, respectively. With 12 months of follow-up, 14 of the 60 eyes (23.3%; 95% confidence interval, 16.9-29.7%) showed significant progression in any lens region. Progression in the nuclear, cortical, and PSC regions was documented in 5%, 6.7%, and 16.7% of cases, respectively. By use of logistic regression, the following factors were not found to be significant for cataract progression in any lens region: age, race, gender, history of hypertension or diabetes, presence of peripheral anterior synechiae or angle width at baseline, and total laser energy delivered.
In fellow eyes of APAC, prophylactic LPI is complicated by significant cataract progression, mainly in the posterior subcapsular region. These findings may have implications for the role of prophylactic LPI in the prevention of angle-closure blindness.
To describe the variation in ocular biometry in adult Chinese individuals in Singapore.
This study was a population-based, cross-sectional survey of adult Chinese persons aged 40 to 81 years residing ...in Tanjong Pagar district, Singapore. Axial ocular dimensions, including axial length (AL), anterior chamber depth (ACD), lens thickness (LT), and vitreous chamber depth (VCD) were measured using an A-scan ultrasound device. Corneal curvature (CC) and noncycloplegic refraction were measured with an autorefractor, with refraction further refined subjectively. Lens nuclear opacity (NO) was graded clinically using the modified Lens Opacity Classification System III (LOCS III) score.
A total of 1717 subjects were eligible for the survey, of whom 1232 (71.8%) participated. Biometric and refraction data were available for 1004 (58.5%) phakic subjects. The AL, ACD, LT, VCD, CC, and LOCS III scores were 23.23 +/- 1.17 mm, 2.90 +/- 0.44 mm, 4.75 +/- 0.47 mm, 15.58 +/- 1.11 mm, 7.65 +/- 0.27 mm, and 3.2 +/- 0.9 (mean +/- SD), respectively. On average, people aged 40 to 49 years, when compared with those 70 to 81 years, had longer ALs (mean difference, +0.58 mm), deeper ACDs (+0.52 mm), longer VCDs (+0.72 mm), but thinner lenses (-0.70 mm) and less severe NO (-1.7 LOCS III score). CCs did not vary significantly with age. After controlling for age, women had shorter ALs and VCDs, shallower ACDs, but thicker lenses and steeper CCs than men. The variation in noncycloplegic refraction with age was nonlinear. Among people aged 40 to 59 years, a higher prevalence of hyperopia was seen in older compared with younger persons (on average, a difference of +1.3 D for every 10-year difference in age, P: < 0.001), explained principally by shorter AL (and VCD) in older persons. Among those 60 to 81 years, this pattern was not obvious (a difference of -0.03 D for every 10-year difference in age, P: = 0.12), as NO became an additional determinant of refraction, with greater degrees of NO in older person's driving refraction in the "minus" direction.
Ocular dimensions vary with age and gender in adult Chinese persons in Singapore. The variation in noncycloplegic refraction in people 40 years and older may be explained by differences in axial lengths (principally vitreous chamber depths) between older and younger persons and, from 60 years onwards, differences in lens nuclear opacification as well.
To determine the long-term outcome of the contralateral eye in Asian persons with a unilateral attack of acute primary angle closure (APAC).
Cross-sectional observational case series.
Seventy-nine ...individuals who were examined from 4 to 10 years after a unilateral episode of APAC at 2 Singapore hospitals.
All subjects underwent a complete eye examination. The optic discs were graded clinically and photographically for the presence of glaucomatous optic neuropathy, and automated visual field tests were assessed for damage. All visual fields and optic nerve photographs (when available) underwent a second evaluation by a masked glaucoma specialist, who assessed whether the changes were compatible with glaucoma.
Glaucomatous optic neuropathy, intraocular pressure (IOP), and visual impairment (defined as best-corrected visual acuity of worse than 6/12).
Ninety of 138 eligible patients (65.2%) with APAC were examined, 79 with unilateral attacks. Subjects were predominantly Chinese (n = 68; 86%). There were 54 females (68%), and mean age was 68.5+/-8.9 years (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. The contralateral eyes of 7 patients (8.9%) had definite or probable glaucoma, 2 of whom were felt to have glaucoma in that eye at the time of the attack. Three eyes had markedly cupped optic discs (cup-to-disc ratio > or = 0.9). Thirteen eyes (16.9%) had best-corrected vision worse than 6/12, due to cataract in almost half the cases. Only 1 eye had vision < 6/60, the cause of which was corneal decompensation. One other patient had only a central island remaining with vision of 6/12. Mean IOP of the study participants was 15.7+/-4.7 mmHg, with 6 subjects (7.6%) having undergone trabeculectomy.
Definite or probable glaucoma was present at the time of diagnosis in 2 (2.5%) fellow eyes and developed in an additional 5 (6.5%) with a mean follow-up of 6 years. More than 80% of this cohort retained good vision in the contralateral eye, in contrast to the eye that underwent APAC. Unoperated cataract accounted for most of the visual impairment in this group.
To determine the prevalence of lens opacity among Chinese residents of Singapore.
Population-based, cross-sectional survey.
Chinese men and women aged 40 years or more in Singapore.
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.
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.
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.
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.
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