Anterior Chamber Depth in Elderly Chinese The Liwan Eye Study Mingguang He, MD, PhD,1,2 Wenyong Huang, MD,1 Yingfeng Zheng, MD,1 Poul Helge Alsbirk, MD, Dr Med,3 Paul J. Foster, PhD, FRCS(Ed)2,4 Purpose: To assess the anterior chamber depth (ACD) and its variation with age, gender, and angle width in elderly Chinese in an urban area of southern China. Design: Cross-sectional study. Participants: Adults 50 and older were identified using cluster random sampling in Liwan District, Guangzhou. Methods: Gonioscopy was performed before ACD measurements to estimate the geometric angle width according to the Shaffer system. ACD was measured using optical pachymetry. True ACD was calculated by subtracting central corneal thickness from the distance between the anterior corneal epithelium and the anterior lens capsule. Data were presented for the right phakic eyes. Main Outcome Measures: Anterior chamber depth and gonioscopy. Results: Among 1405 participants in the study, data from 1248 right eyes were available for analysis. The mean ACD values for men and women were 2.59 mm (95% confidence interval [CI], 2.56 –2.62; 25th–75th percentile, 2.37–2.82) and 2.42 mm (95% CI, 2.39 –2.44; 25th–75th percentile, 2.21–2.63). Mean ACD declined by 0.09 mm (95% CI, ⫺0.011 to ⫺0.008) per decade (adjusted for gender) and was 0.18 mm (95% CI, ⫺0.213 to ⫺0.141) shallower in women than men (adjusted for age). The ACD was found to be monotonically associated with gonioscopic angle width, decreasing from 2.73 mm (standard deviation [SD], 0.26) in Shaffer grade 4 to 1.94 mm (SD, 0.27) in Shaffer grade 0. There was also a relationship between ACD and refractive error; mean spherical equivalent decreased by 0.030 mm ACD per diopter. Conclusions: This study confirms an inverse association between ACD and age, female gender, and spherical refractive error. Eyes with shallower ACDs had narrower angles. Ophthalmology 2008;115:1286 –1290 © 2008 by the American Academy of Ophthalmology.
Anterior chamber depth (ACD) is a major and important risk factor for primary angle closure (PAC).1– 8 An inverse association of prevalence of PAC with the ACD was consistently suggested in most of studies in the populations of Greenlandic and North American Inuit, Chinese, Mongolians, and European-derived people (e.g., Swedes, white Americans).4,7,9 –11 Congdon et al12 have challenged this observation; using ultrasound biometry for measurement, the distributions of ACD were found not significantly different among Chinese, whites, and blacks. He then proposed that mechanisms other than pupil block (although associated with a shallow anterior
Originally received: August 13, 2007. Final revision: December 1, 2007. Accepted: December 4, 2007. Available online: May 9, 2008. Manuscript no. 2007-1067. 1 State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, China. 2
University College London Institute of Ophthalmology, London, United Kingdom.
3
Department of Ophthalmology, Hillerød Hospital, Hillerød, Denmark.
4
Glaucoma Research Unit, Moorfields Eye Hospital, London, United Kingdom.
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© 2008 by the American Academy of Ophthalmology Published by Elsevier Inc.
chamber) are responsible for the relatively higher rates of primary angle-closure glaucoma in Chinese people.12 We performed a population-based survey in Liwan District, Guangzhou, China, in 2003. Among 1405 subjects selected by random cluster sampling, the prevalence of PAC glaucoma, PAC, and PAC suspects were found to be 1.6%, 2.4%, and 6.2%, respectively.13 The current study seeks to report the distribution of ACD and its association with age, gender, refraction, and gonioscopic findings in adult Chi-
Dr He is recipient of a University College London (London, United Kingdom) Graduate School Research Scholarship and Overseas Research Scholarship (no. 2001061054) and grants from Scientific and Technology Foundation of Guangdong Province, Guangzhou, China (no. 2005B30901008), and Sun Yat-sen University Clinical Research 5010 Project, Guangzhou, China. Dr Foster receives support from the Medical Research Council, London, United Kingdom (grant no. G0401527); Wellcome Trust, London, United Kingdom (grant no. 075110); and Richard Desmond Charitable Foundation, London, United Kingdom (via Fight for Sight). No author has any financial or intellectual conflicts of interest in the material presented. Correspondence to Mingguang He, MD, PhD, Department of Preventive Ophthalmology, Zhongshan Ophthalmic Center, Guangzhou 510060, China. E-mail:
[email protected]. ISSN 0161-6420/08/$–see front matter doi:10.1016/j.ophtha.2007.12.003
He et al 䡠 Anterior Chamber Depth in Elderly Chinese nese people using newly available population data from a glaucoma survey in Guangzhou.
Materials and Methods Ethical approval was obtained from the Zhongshan University Ethical Review Board, the Ethical Committee of Zhongshan Ophthalmic Center, and the Research Governance Committee of Moorfields Eye Hospital. The study was conducted in accordance with the Tenets of the World Medical Association’s Declaration of Helsinki. Examination of the subjects for the cross-sectional survey was carried out from September 2003 to February 2004. Detailed study protocol has been reported elsewhere.13 In brief, subjects were enrolled from a population-based study conducted for residents aged ⱖ50 years using cluster random sampling in Liwan District, Guangzhou. The subjects with previous cataract surgery were excluded but those with established PAC or PAC glaucoma were included. A handheld autorefractor (ARK-30; Nidek Corp, Gamagori, Japan) was used to measure noncycloplegic refraction. Gonioscopy was carried out before any other biometric measurement so that the gonioscopist would not be biased by other biometric results. Gonioscopy was performed with a Goldmann-style one-mirror lens (Model 902; Haag Streit, Bern, Switzerland) at ⫻25 magnification with low ambient illumination. A narrow vertical beam 1 mm in length was offset horizontally for superior and inferior quadrants and vertically for nasal and temporal quadrants. Care was taken to avoid light falling on the pupil. Small movement of the lens was allowed to visualize the drainage angle, but large movements were avoided owing to the possibility of indentation. Geometric angle width was estimated in the superior and inferior quadrants as the angle (in degrees) between a tangent to the surface of the trabecular meshwork and a tangent to the peripheral third of the iris. It was then recorded as 1 of 5 categories (0, 10, 20, 30, and ⬎40 degrees).13 To represent the eye, the average of Shaffer grades in superior and inferior quadrants were taken, and reclassified this into grade 0 ⫽ 0; grade 1 ⫽ 0.5–1.0; grade 2 ⫽ 1.5–2.0; grade 3 ⫽ 2.5–3.0; ad grade 4 ⫽ 3.5– 4.0. The optical pachymetry device (Device I and II, Haag-Streit) was mounted on a slit lamp (Model 900, Haag-Streit) and used to measure the central ACD and central corneal thickness by another ophthalmologist (YZ). The “touch” method of measurement was used throughout. The subject was instructed to gaze in the primary position. The brightest, narrowest illumination beam was used. The visual axis in ACD and central corneal thickness measurements was approximated by referencing the pupil margin. Central corneal thickness was measured with Device I at ⫻1.6 objective magnification with a ⫹2.5-diopter eyepiece addition, read to the nearest 0.01 mm. The ACD (anterior corneal epithelial surface to the anterior lens capsule) was measured to the nearest 0.05 mm using Device II at ⫻1 objective magnification and a ⫹6-diopter eyepiece addition. Three measurements were carried out and the median of the 3 readings was recorded. The “true” ACD from the endothelial surface of the cornea to the anterior lens capsule was calculated by subtracting the corneal thickness from the ACD initial values. No correction was made for the corneal curvature. All data are presented for the right phakic eyes only. Because the ACD data displayed an approximately normal distribution (S-K test for normality, P for skewness ⫽ 0.575; P for kurtosis ⫽ 0.031), a linear regression model was used to explore the association of age and gender with ACD. The confidence interval was calculated assuming a normal distribution. Data analysis was performed using Stata Package (Stata 8.0; Stata Corp., College Station, TX).
Figure 1. Distribution of optical anterior chamber depth (mean, 2.49 mm; standard deviation, 0.34 mm) on the phakic right eyes.
Results Among the 1405 participants, 1248 subjects had ACD data on the right eye available for analysis. The ACD data were missing in 110 right eyes, mainly because this examination was not performed for every subject in the first 3 days of the examination period; data were also missing from a few subjects who could not be examined by optical pachymetry (because of severe corneal opacity, enucleated globe, Parkinson syndrome, paralysis). An additional 47 aphakic and pseudophakic eyes were also excluded. Table 1 (available at http://aaojournal.org) shows the demographics of those with and without ACD data with minor heterogeneities for age, education level, and refraction. The ACD approximates to a normal distribution (Fig 1). The mean ACD values for men and women were significantly different: 2.59 mm (95% confidence interval [CI], 2.56 – 2.62) and 2.42 mm (95% CI, 2.39 –2.44) respectively (t test; P⬍0.001; Table 2). Older people had shallower ACDs, seen in both men and women. Multiple linear regression of ACD on age and gender (r2 ⫽ 0.14; P⬍0.001) suggested that mean ACD declined by 0.009 mm (95% CI, 0.008 – 0.011) per year (adjusted for gender) and was 0.18 mm (95% CI, 0.14 – 0.21) shallower in women than men (adjusted for age). The regression coefficients of ACD with age in males and females were ⫺0.010 (P⬍0.001) and ⫺0.009 (P⬍0.001) mm per year, respectively. Adding the spherical equivalent value of refraction to the regression model led to a better explanation of the variation in ACD, with a higher r2 of 0.21 and a regression coefficient for spherical equivalent of ⫺0.030 mm per diopter (95% CI, ⫺0.036 to ⫺0.023). Figure 2 (available at http:// aaojournal.org) shows a Lowess curve (representing the central tendency of the data without a specific mathematical model being imposed) for both genders, suggesting a similar crosssectional pattern of decrease in ACD values with age. Anterior chamber depth was found to be monotonically associated with gonioscopic angle width (Fig 3): the deeper ACD, the wider angle width (Spearman correlation coefficient, 0.70; P⬍0.001). At a given angle width, men tended to have a deeper ACD than women, except in those with very narrow angle widths (grade 0 or 1; Table 3).
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Ophthalmology Volume 115, Number 8, August 2008 Table 2. Anterior Chamber Depth in Phakic Subjects (Optical Pachymetry—Right Eyes)*
Men (age) 50–59 60–69 70–79 80–93 All Women (age) 50–59 60–69 70–79 80–93 All Men and women (age) 50–59 60–69 70–79 80–93 All
n
Mean (95% CI)
SD
Range
25th Percentile
50th Percentile
75th Percentile
Missing
193 162 154 32 541
2.72 (2.67–2.76) 2.58 (2.52–2.63) 2.49 (2.43–2.54) 2.43 (2.30–2.57) 2.59 (2.56–2.62)
0.31 0.37 0.34 0.38 0.36
1.94–3.82 1.27–3.88 1.49–3.36 1.44–3.12 1.27–3.88
2.53 2.33 2.24 2.28 2.37
2.71 2.60 2.49 2.50 2.61
2.90 2.83 2.72 2.68 2.82
17 8 19 9 53
247 213 200 47 707
2.53 (2.49–2.57) 2.39 (2.35–2.43) 2.34 (2.29–2.38) 2.27 (2.19–2.34) 2.42 (2.39–2.44)
0.30 0.29 0.33 0.26 0.32
1.75–3.31 1.32–3.26 1.29–3.26 1.74–2.76 1.29–3.31
2.30 2.21 2.11 2.05 2.21
2.50 2.38 2.35 2.29 2.41
2.73 2.60 2.52 2.46 2.63
15 11 19 12 57
440 375 354 79 1248
2.61 (2.58–2.64) 2.47 (2.43–2.51) 2.40 (2.37–2.44) 2.33 (2.26–2.41) 2.49 (2.47–2.51)
0.32 0.34 0.34 0.32 0.34
1.75–3.82 1.27–3.88 1.29–3.36 1.44–3.12 1.27–3.88
2.40 2.24 2.16 2.05 2.26
2.62 2.45 2.39 2.39 2.48
2.81 2.71 2.61 2.53 2.72
32 19 38 21 110
CI ⫽ confidence interval; SD ⫽ standard deviation. Figures represent distance between anterior lens capsule and corneal endothelium in the pupillary axis.
Discussion The current study is the first published population-based data documenting the ACD in elderly Chinese based on a cohort from mainland China. A previous clinic-based work in Beijing reported ACD distribution in 266 “normal” eyes and 639 “primary glaucoma” eyes.7 Our study has the advantage of being population based and therefore gives a
cross-sectional picture of the ACD in the community at large. The mean of ACD measured by optical pachymetry in this Chinese cohort aged ⱖ50 was 2.49 mm (standard deviation, 0.32 mm). The mean ACD was found to be shallower in older subjects, dropping from 2.61 mm in 50to 59-year-olds to 2.33 mm in 80- to 93-year-olds. Using the same measurement method by the same group of researchers, age, and gender-specific values of ACD in Guangzhou were found to be deeper than in Mongolians and probably similar to the level in the Singaporean Chinese population (Fig 4 [available at http://aaojournal.org]). Mean difference between ACDs of men and women was 0.18 mm (M⬎F), and was similar to that of 0.15 mm found in Eskimos, 0.12 mm in Mongolians, and 0.17 mm in Singaporeans.4,11,14 Our results further support that the notion that the racial difference in the prevalence of PAC is associated with the ACD variation in various populations: shallower ACDs are Table 3. Association of Anterior Chamber Depth and Gonioscopic Angle Width Angle Width*
Figure 3. Distribution of anterior chamber depth in various Shaffer angle width grades. Each box extends from the 25th to the 75th percentiles of the distribution in each Shaffer angle width grade; the bar inside each box represents the median. The whiskers extend to the lower and upper extremes, defined as the 25th percentile minus 1.5 times the interquartile range and 75th percentile plus 1.5 times the interquartile range. The average of Shaffer grades in superior and inferior quadrants were taken to represent the eye and reclassified this into grade 0, 0; grade 1.0, 0.5 to 1; grade 2, 1.5 to 2.0; grade 3, 2.5 to 3.0; and grade 4, 3.5 to 4.0.
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0 1 2 3 4
Men (n ⴝ 535)
Women (n ⴝ 699)
All† (n ⴝ 1234)
n
Mean (SD)
n
Mean (SD)
n
Mean (SD)
13 43 57 147 275
1.89 (0.24) 2.10 (0.22) 2.33 (0.29) 2.55 (0.26) 2.78 (0.26)
37 97 137 201 227
1.96 (0.28) 2.10 (0.18) 2.30 (0.22) 2.44 (0.20) 2.67 (0.25)
50 140 194 348 502
1.94 (0.27) 2.10 (0.19) 2.31 (0.24) 2.49 (0.23) 2.73 (0.26)
SD ⫽ standard deviation. *The average of Shaffer grades in superior and inferior quadrants were taken and reclassified this into grade 0 ⫽ 0; grade 1 ⫽ 0.5–1.0; grade 2 ⫽ 1.5–2.0; grade 3 ⫽ 2.5–3.0; and grade 4 ⫽ 3.5– 4.0. † A further 14 eyes had missing gonioscopy data.
He et al 䡠 Anterior Chamber Depth in Elderly Chinese normally found in populations with a higher rate of PAC (Fig 5 [available at http://aaojournal.org]).4,9 –11 However, Congdon et al challenged this theory. They examined 531 Chinese (from a Taiwanese population survey with a low [10%] response rate), 170 whites, and 188 blacks (from an outpatient clinic in Baltimore), all aged ⱖ40 years, using ultrasound biometry for ACD and axial length.12 The mean values of ACD and axial length were not significantly different between these 3 ethnic groups, with means of about 3.0 mm for ACD. Adjustment for refractive error was not made in the mean value calculations. The only ethnic difference was a smaller radius of corneal curvature in Chinese eyes. However, several issues, including the low participation rate in the Taiwanese cohort, may weaken the case they propose. For instance, selection bias seems to have resulted in a large proportion of 40- to 49-year-old Chinese subjects being enrolled (137 of 531 vs 17 of 170 whites), thus accentuating the distribution of ACD toward deeper values in the younger age cohort of Chinese in whom more myopia was more prevalent. Caucasian and Chinese values seem to show an expected variation in those aged ⱖ60, with lower ACD mean values in Chinese. Measurement errors attributable to the handheld ultrasound technique might also have affected the validity of ACD measurements. Furthermore, a similar cohort effect and secular trend was observed among Alaskan Inuit by the same group.15 There is no simple explanation for the variation in ACD between different ethnic groups, and even among the same Mongoloid–Chinese group living in Mongolia, Guangzhou, and Singapore who probably share the similar ancestry. “True” ACD is the distance between the posterior surface of cornea and the anterior surface of the lens along the visual axis and is determined by the height of the corneal dome and the position of the anterior lens surface. The ACD distributions are associated with axial length, and are directly influenced by the position and thickness of the lens and probably corneal curvature. A higher rate of myopia may explain the higher values of axial length and ACD in Singaporean Chinese and Japanese, whereas elderly Inuit and Mongolian populations present the opposite—a low rate of myopia with a shorter eye. Stature was also found to be associated with axial length and ACD: taller people are more likely to have longer globes, deeper anterior chambers, thinner lenses, and flatter corneas.16,17 This may in part explain the deeper ACD in European eyes. However, the myopia rate and axial length of the population alone cannot satisfactorily explain the difference between Chinese and Europeans when the rate of myopia is lower (He, unpublished data) but ACD are deeper in Europeans. The ACD is determined by the position and thickness of the lens. Lowe18 concluded that 35% of the variation in ACD was attributable to lens thickness, and the remaining 65% was due to a more anteriorly positioned lens based on a case-control study in Australian Caucasians. Another study in Singaporean Chinese found that lens thickness was a major determinant, only a small difference (4%) on relative lens position when comparing the contralateral eyes of acute PAC and normal controls.19 The mechanism behind the thicker and anteriorly positioned lenses in Chinese is
largely unknown and often attributed to “ethnic difference” or genetic variation.20,21 Heritability study shows that the age- and gender-independent ACD variation gives heritability estimates around h2 ⫽ 0.7, that is, at a level found also in several other ocular biometric traits.16 The paucity of biometric data in European elderly population further hinders a valid comparison. Gonioscopic angle width is a measure of the likelihood of angle closure. Gonioscopy is commonly used as the definitive diagnostic tool for identifying angles with increasing risk of angle closure. However, gonioscopy is very skilled task and equipment dependent, and is not suitable for widespread use in screening initiatives. Therefore, ACD has been suggested as a screening tool in the community, based on the acknowledged association between a shallow ACD and closure of the drainage angle.22,23 Our study demonstrates the monotonic association of ACD values with angle width grades, which supports the usage of ACD as surrogate measurement for gonioscopy in community screening. Chandler24 and Lowe25 suggested that pupil block is the consequence of contact between the iris and the anterior surface of the lens and is exacerbated when the anterior lens surface lies anterior to the plane of the iris root. The narrowing of drainage angles predominated by a nonpupil block mechanism is likely due to variations of iris insertion, profile, thickness at the iris root, and anterior position or displacement of the ciliary body.26 Therefore, the monotonic association of ACD and drainage angle may suggest that the narrowing of the drainage angle in our Chinese cohort is predominantly the result of increasing pupil block. However, our angle width data were derived from Shaffer grades in gonioscopic examination and therefore are ordinal data. This monotonic association may need to be confirmed by quantitative angle width data obtained by an anterior chamber imaging system (ultrasound biomicroscopy or anterior segment optical coherence tomography). In summary, our study provides the first detailed epidemiologic data on the ACD characteristics in an elderly population from an urban area of mainland China. We confirm that the mean ACD of the adults in southern China is between that of Mongolian and Singaporean populations. The patterns (slope) of the ACD changes with age in these 3 populations are in fact very similar. The comparison of our data with that obtained in other populations further confirms that the ACD tends to be shallower in populations with higher rates of angle-closure. The monotonic association between ACD and gonioscopic angle width seems to suggest that the pupil block mechanism is predominant in this Chinese cohort and highlights the need to use ACD estimation as a screening tool for identifying persons at risk with narrow angles in community screening settings.
References 1. Alsbirk PH. Anterior chamber depth in Greenland Eskimos. I. A population study of variation with age and sex. Acta Ophthalmol (Copenh) 1974;52:551– 64. 2. Barrett BT, McGraw PV, Murray LA, Murgatroyd P. Anterior chamber depth measurement in clinical practice. Optom Vis Sci 1996;73:482– 6.
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Ophthalmology Volume 115, Number 8, August 2008 3. Cohen JS, Tilton T. Technique for slit lamp comparison of anterior chamber depth. Ophthalmic Surg 1988;19:58 –9. 4. Foster PJ, Alsbirk PH, Baasanhu J, et al. Anterior chamber depth in Mongolians: variation with age, sex, and method of measurement. Am J Ophthalmol 1997;124:53– 60. 5. Gawdat I. Measurement of the depth of anterior chamber using Jaeger micrometer and gonioscopic studies of the angle in normotensive Egyptian eyes. Bull Ophthalmol Soc Egypt 1976;69:189 –201. 6. Lu DP. Depth of the anterior chamber in normal eyes and eyes with primary glaucoma [in Chinese]. Zhonghua Yan Ke Za Zhi 1986;22:93– 6. 7. Zhang SF. Measurement of the depth of the anterior chamber in primary glaucoma and its clinical application [in Chinese]. Zhonghua Yan Ke Za Zhi 1983;19:12– 6. 8. Zhao JL. Relation between the depth of the anterior chamber and anterior chamber angle in primary angle closure glaucoma [in Chinese]. Zhonghua Yan Ke Za Zhi 1986;22:19 –23. 9. Tornquist R. Shallow anterior chamber in acute angle-closure: a clinical and genetic study. Acta Ophthalmol Suppl 1953;39:1–74. 10. Koenig SB. Myopic shift in refraction after penetrating keratoplasty with pediatric donor tissue. Am J Ophthalmol 1986; 101:740 –1. 11. Alsbirk PH. Limbal and axial chamber depth variations: a population study in Eskimos. Acta Ophthalmol (Copenh) 1986;64:593– 600. 12. Congdon NG, Youlin Q, Quigley H, et al. Biometry and primary angle-closure glaucoma among Chinese, white, and black populations. Ophthalmology 1997;104:1489 –95. 13. He M, Foster PJ, Ge J, et al. Prevalence and clinical characteristics of glaucoma in adult Chinese: a population-based study in Liwan District, Guangzhou. Invest Ophthalmol Vis Sci 2006;47:2782– 8. 14. Foster PJ. The epidemiology of glaucoma in East Asian people [dissertation]. London: University College London; 2002. 15. Wojciechowski R, Congdon N, Anninger W, Teo Broman A. Age, gender, biometry, refractive error, and the anterior chamber angle among Alaskan Eskimos. Ophthalmology 2003;110: 365–75.
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16. Alsbirk PH. Anterior chamber of the eye: a genetic and anthropological study in Greenland Eskimos. Hum Hered 1975;25:418 –27. 17. Wong TY, Foster PJ, Johnson GJ, et al. The relationship between ocular dimensions and refraction with adult stature: the Tanjong Pagar Survey. Invest Ophthalmol Vis Sci 2001; 42:1237– 42. 18. Lowe RF. Causes of shallow anterior chamber in primary angle closure glaucoma: ultrasonic biometry of normal and angle-closure eyes. Am J Ophthalmol 1969;67:87–93. 19. Friedman DS, Gazzard G, Foster P, et al. Ultrasonographic biomicroscopy, Scheimpflug photography, and novel provocative tests in contralateral eyes of Chinese patients initially seen with acute angle closure. Arch Ophthalmol 2003;121: 633– 42. 20. Alsbirk PH. Anterior chamber depth and primary angleclosure glaucoma. II. A genetic study. Acta Ophthalmol (Copenh) 1975;53:436 – 49. 21. Lowe RF. Primary angle-closure glaucoma: family histories and anterior chamber depths. Br J Ophthalmol 1964;48: 191–5. 22. Devereux JG, Foster PJ, Baasanhu J, et al. Anterior chamber depth measurement as a screening tool for primary angleclosure glaucoma in an East Asian population. Arch Ophthalmol 2000;118:257– 63. 23. Congdon NG, Quigley HA, Hung PT, et al. Screening techniques for angle-closure glaucoma in rural Taiwan. Acta Ophthalmol Scand 1996;74:113–9. 24. Chandler PA. Peripheral iridectomy. Arch Ophthalmol 1964; 72:804 –7. 25. Lowe RF. Angle-closure, pupil dilatation, and pupil block. Br J Ophthalmol 1966;50:385–9. 26. He M, Foster PJ, Ge J, et al. Gonioscopy in adult Chinese: the Liwan Eye Study. Invest Ophthalmol Vis Sci 2006;47: 4772–9. 27. Weekers R, Delmarcelle Y, Collignon J, Luyckx J. Optical measurement of the depth of the anterior chamber: clinical applications [in French]. Doc Ophthalmol 1973;34:413–34.
He et al 䡠 Anterior Chamber Depth in Elderly Chinese
Figure 2. Lowess curve for axial anterior chamber depth by age in males and females.
Figure 4. Anterior chamber depth (ACD) variation with age by gender in Mongolia,4 Singapore,14 and Guangzhou.
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Figure 5. Interethnic anterior chamber depth (ACD) variations, based on Haag Streit pachymetry measurements. Belgians27; Japanese includes Kitazawa (unpublished data); Mongolians4; Singaporeans14; Inuit1; Chinese in Liwan.
Table 1. Demographics of and Refraction in the Subjects Included and Excluded from Analysis Characteristic Age (yrs) 50–59 60–69 70–79 ⱖ80 Gender Male Female Education No formal Primary Junior high Senior high College Refraction (diopters, right eye)§ ⱕ⫺4 ⬎⫺4 and ⱕ⫺2 ⬎⫺2 and ⱕ⫺0.5 ⬎⫺0.5 and ⬍⫹2 ⱖ⫹2 and ⬍⫹4 ⱖ⫹4
Included* Excluded*† (n ⴝ 1248) (n ⴝ 157)
P Value‡
35.3 30.1 28.4 6.3
22.3 17.8 41.4 18.5
⬍0.001
56.7 43.3
54.1 45.9
0.550
18.2 27.1 39.9 10.4 4.4
34.4 32.8 23.0 4.9 4.9
0.006
8.1 7.8 18.0 59.3 6.6 0.3
5.9 10.8 26.5 52.0 2.9 2.0
0.865
*Data are given as percentage proportions by column. Excluding 47 right aphakic or pseudophakic eyes. Reasons for other missing data included home visit, unable to undergo testing (corneal opacity, Parkinsonism, paralysis) and that during the first 3 days optical pachymetry was not performed for every subject. ‡ Given by t test for age and refraction variables and by chi square test for gender and education variables. § The right eyes in the included and excluded group were chosen for comparison. †
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