BioMed Central
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_tQM<~Y]u\ BMC Ophthalmology
+lf`Dd3 Research article Open Access
$}0\sj% Comparison of age-specific cataract prevalence in two
i
UqD>OV population-based surveys 6 years apart
T=g2gmo9 Ava Grace Tan†, Jie Jin Wang*†, Elena Rochtchina† and Paul Mitchell†
$o)}@TC Address: Centre for Vision Research, Westmead Millennium Institute, Department of Ophthalmology, University of Sydney, Westmead Hospital,
eG.s|0` Westmead, NSW, Australia
Wk
}}f|O0 Email: Ava Grace Tan -
ava_tan@wmi.usyd.edu.au; Jie Jin Wang* -
jiejin_wang@wmi.usyd.edu.au;
srKEtd" Elena Rochtchina -
elena_rochtchina@wmi.usyd.edu.au; Paul Mitchell -
paul_mitchell@wmi.usyd.edu.au ,~Lx7 5{ * Corresponding author †Equal contributors
`C^0YGO% Abstract
'@^mesMG Background: In this study, we aimed to compare age-specific cortical, nuclear and posterior
ArT@BqWd subcapsular (PSC) cataract prevalence in two surveys 6 years apart.
$
B]_^ Methods: The Blue Mountains Eye Study examined 3654 participants (82.4% of those eligible) in
? a/\5`gnN cross-section I (1992–4) and 3509 participants (75.1% of survivors and 85.2% of newly eligible) in
q1rD>n&d cross-section II (1997–2000, 66.5% overlap with cross-section I). Cataract was assessed from lens
N{a=CaYi+ photographs following the Wisconsin Cataract Grading System. Cortical cataract was defined if
Juk'eH2^s cortical opacity comprised ≥ 5% of lens area. Nuclear cataract was defined if nuclear opacity ≥
Ju"c!vu~ Wisconsin standard 4. PSC was defined if any present. Any cataract was defined to include persons
P_.AqEH who had previous cataract surgery. Weighted kappa for inter-grader reliability was 0.82, 0.55 and
7H,)heA 0.82 for cortical, nuclear and PSC cataract, respectively. We assessed age-specific prevalence using
;
2gO( an interval of 5 years, so that participants within each age group were independent between the
Dh68=F0 two surveys.
pMf
?'l Results: Age and gender distributions were similar between the two populations. The age-specific
m:9|5W prevalence of cortical (23.8% in 1st, 23.7% in 2nd) and PSC cataract (6.3%, 6.0%) was similar. The
u!FF
{~5cs prevalence of nuclear cataract increased slightly from 18.7% to 23.9%. After age standardization,
-^< t%{d the similar prevalence of cortical (23.8%, 23.5%) and PSC cataract (6.3%, 5.9%), and the increased
Y/L*0M.< prevalence of nuclear cataract (18.7%, 24.2%) remained.
}E&: Conclusion: In two surveys of two population-based samples with similar age and gender
xi)$t#K" distributions, we found a relatively stable cortical and PSC cataract prevalence over a 6-year period.
?YF2Uc8z%2 The increased prevalence of nuclear cataract deserves further study.
j.\0p-, Background
]i>,oxBWe Age-related cataract is the leading cause of reversible visual
tLP
Er@ impairment in older persons [1-6]. In Australia, it is
8\+DSA estimated that by the year 2021, the number of people
MIqH%W.ru affected by cataract will increase by 63%, due to population
sDBwD%sb aging [7]. Surgical intervention is an effective treatment
\0FwxsL for cataract and normal vision (> 20/40) can usually
>Udq{<]#r be restored with intraocular lens (IOL) implantation.
x-b}S1@ Cataract surgery with IOL implantation is currently the
D"IxQ2}k most commonly performed, and is, arguably, the most
TQQh:y cost effective surgical procedure worldwide. Performance
60WlC0Y~u Published: 20 April 2006
n8i
: /ypB BMC Ophthalmology 2006, 6:17 doi:10.1186/1471-2415-6-17
@c).&7 Received: 14 December 2005
*Xh#W7,< Accepted: 20 April 2006
4,BJK`{ This article is available from:
http://www.biomedcentral.com/1471-2415/6/17 .Y^pDR12 © 2006 Tan et al; licensee BioMed Central Ltd.
BQ B<+o' This is an Open Access article distributed under the terms of the Creative Commons Attribution License (
http://creativecommons.org/licenses/by/2.0),
Y3SV6""y/ which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
#oN}DP BMC Ophthalmology 2006, 6:17
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C 1)+^{7ef of this surgical procedure has been continuously increasing
$UpWlYwG in the last two decades. Data from the Australian
Qv
J29 Health Insurance Commission has shown a steady
?A-f_0<0 increase in Medicare claims for cataract surgery [8]. A 2.6-
**.23<n^W fold increase in the total number of cataract procedures
E%a&6W from 1985 to 1994 has been documented in Australia [9].
K#VGG,h7Y The rate of cataract surgery per thousand persons aged 65
p[)yn%uh years or older has doubled in the last 20 years [8,9]. In the
q#\B}'I{ Blue Mountains Eye Study population, we observed a onethird
t3=K>Y@w increase in cataract surgery prevalence over a mean
Iz>\qC} 6-year interval, from 6% to nearly 8% in two cross-sectional
at1oxmy population-based samples with a similar age range
U~dqxR"Q [10]. Further increases in cataract surgery performance
,k(B>O ~o would be expected as a result of improved surgical skills
c{ qTVi5e and technique, together with extending cataract surgical
md|I?vk benefits to a greater number of older people and an
</R@)_' increased number of persons with surgery performed on
D[4%CQ1m both eyes.
GB,ub*| Both the prevalence and incidence of age-related cataract
5JhpBx/>o= link directly to the demand for, and the outcome of, cataract
u`Kc\B
Sn surgery and eye health care provision. This report
LLMGs: [ aimed to assess temporal changes in the prevalence of cortical
/+WC6& and nuclear cataract and posterior subcapsular cataract
f"^t~q[VS (PSC) in two cross-sectional population-based
o@C|*TXN surveys 6 years apart.
ch0cFF^] Methods
$-<yX<. The Blue Mountains Eye Study (BMES) is a populationbased
NG
ZtlNvh cohort study of common eye diseases and other
RN;#H_
q health outcomes. The study involved eligible permanent
~{N#JO
Y}Z residents aged 49 years and older, living in two postcode
NdRE,HWd?$ areas in the Blue Mountains, west of Sydney, Australia.
Ok}e|b[D Participants were identified through a census and were
M. _5mZ{ invited to participate. The study was approved at each
|:u5R% stage of the data collection by the Human Ethics Committees
L:Faq1MG of the University of Sydney and the Western Sydney
ETR7%0$r Area Health Service and adhered to the recommendations
!~j9Oc^ of the Declaration of Helsinki. Written informed consent
Zjs,R{ was obtained from each participant.
IWwOP{ <ZQ Details of the methods used in this study have been
>,rzPc)
described previously [11]. The baseline examinations
%O{FZgi%wA (BMES cross-section I) were conducted during 1992–
>!c Ff$2' 1994 and included 3654 (82.4%) of 4433 eligible residents.
U8%IpI; Follow-up examinations (BMES IIA) were conducted
h,K&R8S during 1997–1999, with 2335 (75.0% of BMES
R/6
v#9m7 cross section I survivors) participating. A repeat census of
r\y\]AmF the same area was performed in 1999 and identified 1378
$lJ!
f newly eligible residents who moved into the area or the
e"Z,!Q^-L eligible age group. During 1999–2000, 1174 (85.2%) of
ur]WNk8bN this group participated in an extension study (BMES IIB).
?pA_/wwp BMES cross-section II thus includes BMES IIA (66.5%)
")fgQ3XZ and BMES IIB (33.5%) participants (n = 3509).
2"o<>d Similar procedures were used for all stages of data collection
sr~VvciIy at both surveys. A questionnaire was administered
qzk]9`i1: including demographic, family and medical history. A
hG}/o&}U detailed eye examination included subjective refraction,
#!rH}A>n+ slit-lamp (Topcon SL-7e camera, Topcon Optical Co,
h5^We"}+ Tokyo, Japan) and retroillumination (Neitz CT-R camera,
g](&H$g Neitz Instrument Co, Tokyo, Japan) photography of the
*LvdrPxU= lens. Grading of lens photographs in the BMES has been
}E)
t,T> previously described [12]. Briefly, masked grading was
BpF}H^V- performed on the lens photographs using the Wisconsin
lDs C>L-F Cataract Grading System [13]. Cortical cataract and PSC
uYd_5
nw were assessed from the retroillumination photographs by
zS?DXE estimating the percentage of the circular grid involved.
ikPr> Cortical cataract was defined when cortical opacity
UG<<.1JL involved at least 5% of the total lens area. PSC was defined
2$gFiZ when opacity comprised at least 1% of the total lens area.
AP?m,nd6 Slit-lamp photographs were used to assess nuclear cataract
>EgMtZ88.< using the Wisconsin standard set of four lens photographs
==bT0-M.~ [13]. Nuclear cataract was defined when nuclear opacity
Lf8{']3 was at least as great as the standard 4 photograph. Any cataract
tTJ$tx was defined to include persons who had previous
CTc#*LJx>j cataract surgery as well as those with any of three cataract
_cbXzSYq& types. Inter-grader reliability was high, with weighted
AgdU@&^ kappa 0.82 for cortical cataract, 0.55 (simple kappa 0.75)
0LP>3"Sm for nuclear cataract and 0.82 for PSC grading. The intragrader
1mx;b)4t reliability for nuclear cataract was assessed with
JOki4N simple kappa 0.83 for the senior grader who graded
*(VwD)* nuclear cataract at both surveys. All PSC cases were confirmed
QO|jdlg by an ophthalmologist (PM).
4o@^._-R In cross-section I, 219 persons (6.0%) had missing or
ab<7jfFIa ungradable Neitz photographs, leaving 3435 with photographs
mS]soYTQ available for cortical cataract and PSC assessment,
j,N,WtE while 1153 (31.6%) had randomly missing or ungradable
.r-kH&)"GU Topcon photographs due to a camera malfunction, leaving
OEHw% 2501 with photographs available for nuclear cataract
B 5va4@ assessment. Comparison of characteristics between participants
?&.Eg^a" with and without Neitz or Topcon photographs in
'ExQG$t cross-section I showed no statistically significant differences
vn96o]n between the two groups, as reported previously
0U:9&jP, [12]. In cross-section II, 441 persons (12.5%) had missing
0"`|f0}c or ungradable Neitz photographs, leaving 3068 for cortical
QWK\6 cataract and PSC assessment, and 648 (18.5%) had
~"vRH missing or ungradable Topcon photographs, leaving 2860
=,LhMy for nuclear cataract assessment.
O,7*dniH Data analysis was performed using the Statistical Analysis
luO4ap]* System (SAS, SAS Institute, Cary, NC, USA). Age-adjusted
w;T?m," prevalence was calculated using direct standardization of
K_BF=C.k the cross-section II population to the cross-section I population.
k#/%#rQM We assessed age-specific prevalence using an
,SoqVboRl interval of 5 years, so that participants within each age
<(2,@_~@r group were independent between the two cross-sectional
Jgf=yri surveys.
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?rv5Z^D' Results
J"]P"`/ Characteristics of the two survey populations have been
Kyq/o- previously compared [14] and showed that age and sex
'B$qq[l]S distributions were similar. Table 1 compares participant
$ ~2qEe.h characteristics between the two cross-sections. Cross-section
VtC1TZ3-7 II participants generally had higher rates of diabetes,
t0gLz
J hypertension, myopia and more users of inhaled steroids.
(8OaXif Cataract prevalence rates in cross-sections I and II are
"]D2}E>U; shown in Figure 1. The overall prevalence of cortical cataract
NhA_dskvo was 23.8% and 23.7% in cross-sections I and II,
06S-3bis respectively (age-sex adjusted P = 0.81). Corresponding
B*
j
AD2 prevalence of PSC was 6.3% and 6.0% for the two crosssections
/I3>u (age-sex adjusted P = 0.60). There was an
WD,iY_'7u^ increased prevalence of nuclear cataract, from 18.7% in
Jri"Toz0 cross-section I to 23.9% in cross-section II over the 6-year
Up kw.`D` period (age-sex adjusted P < 0.001). Prevalence of any cataract
H
{3A6fb< (including persons who had cataract surgery), however,
5n'C6q " was relatively stable (46.9% and 46.8% in crosssections
VXtW{*{" I and II, respectively).
4RV5:&ALLS After age-standardization, these prevalence rates remained
DU/WB stable for cortical cataract (23.8% and 23.5% in the two
h tn?iLq surveys) and PSC (6.3% and 5.9%). The slightly increased
vo_m$ /O prevalence of nuclear cataract (from 18.7% to 24.2%) was
O0i[GCtP5 not altered.
N\OeWjA F Table 2 shows the age-specific prevalence rates for cortical
H%:~&_D cataract, PSC and nuclear cataract in cross-sections I and
1
]uHaI( II. A similar trend of increasing cataract prevalence with
/HmD/
E\ increasing age was evident for all three types of cataract in
n-7|{1U both surveys. Comparing the age-specific prevalence
7#BpGQJQ between the two surveys, a reduction in PSC prevalence in
K2glkGK cross-section II was observed in the older age groups (≥ 75
cR+9^DzA years). In contrast, increased nuclear cataract prevalence
;nbUbRb in cross-section II was observed in the older age groups (≥
_ ecKX</Q 70 years). Age-specific cortical cataract prevalence was relatively
cDS6RO? consistent between the two surveys, except for a
]#N~r&hmQ reduction in prevalence observed in the 80–84 age group
*h
p3w and an increasing prevalence in the older age groups (≥ 85
jz_\B(m9% years).
[C]u!\(IF Similar gender differences in cataract prevalence were
csV.AN'obq observed in both surveys (Table 3). Higher prevalence of
4Y[uqn[ cortical and nuclear cataract in women than men was evident
_T 5ZL but the difference was only significant for cortical
a~_5N&~pi cataract (age-adjusted odds ratio, OR, for women 1.3,
vt" 7[!O 95% confidence intervals, CI, 1.1–1.5 in cross-section I
V3'QA1$ and OR 1.4, 95% CI 1.1–1.6 in cross-section II). In con-
:6 ?&L Table 1: Participant characteristics.
_-^Lr
/`G! Characteristics Cross-section I Cross-section II
7ZbnG@s7 n % n %
T=|oZ Age (mean) (66.2) (66.7)
[WDtr8L 50–54 485 13.3 350 10.0
gu[3L 55–59 534 14.6 580 16.5
C%8jWc 60–64 638 17.5 600 17.1
uX-]z3+ 65–69 671 18.4 639 18.2
e'I13)
70–74 538 14.7 572 16.3
>W=
0N( 75–79 422 11.6 407 11.6
T.vkGB=QZ% 80–84 230 6.3 226 6.4
*7'}"@@ 85–89 100 2.7 110 3.1
1k2+eI 90+ 36 1.0 24 0.7
kETu@la} Female 2072 56.7 1998 57.0
iEG`+h' Ever Smokers 1784 51.2 1789 51.2
XY]|OZ7( Use of inhaled steroids 370 10.94 478 13.8^
0s"g%gq| History of:
n%lY7.z8d Diabetes 284 7.8 347 9.9^
tl |Qw";I Hypertension 1669 46.0 1825 52.2^
N'nI
^= Emmetropia* 1558 42.9 1478 42.2
gw0b>E8gZ& Myopia* 442 12.2 495 14.1^
LEoL6ga Hyperopia* 1633 45.0 1532 43.7
H]5%"(h n = number of persons affected
u:r'jb~@ * best spherical equivalent refraction correction
iq> PN:mr ^ P < 0.01
$~xY6"_}!! BMC Ophthalmology 2006, 6:17
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^NB@wuf7 (page number not for citation purposes)
Iy\{)+}aS t
<S'5`-& rast, men had slightly higher PSC prevalence than women
sM)n-Yy#9 in both cross-sections but the difference was not significant
m&xyw9a (OR 1.1, 95% CI 0.8–1.4 for men in cross-section I
` V}e$ and OR 1.2, 95% 0.9–1.6 in cross-section II).
|EuWzhNAO Discussion
@#q>(Ox% Findings from two surveys of BMES cross-sectional populations
?ic 7M with similar age and gender distribution showed
LFHV~>d that the prevalence of cortical cataract and PSC remained
KlbL<9P> stable, while the prevalence of nuclear cataract appeared
Sr1xG%;|/ to have increased. Comparison of age-specific prevalence,
E5.3wOE with totally independent samples within each age group,
\(Uw.ri confirmed the robustness of our findings from the two
o:u *E survey samples. Although lens photographs taken from
2x-67_BHY= the two surveys were graded for nuclear cataract by the
J_A+)_ same graders, who documented a high inter- and intragrader
+qsNz*@p" reliability, we cannot exclude the possibility that
_w8iPL5: variations in photography, performed by different photographers,
#Aox$[|@ may have contributed to the observed difference
z
mvF#o in nuclear cataract prevalence. However, the overall
n!5 :I#B Table 2: Age-specific prevalence of cataract types in cross sections I and II.
GaMiu!|, Cataract type Age (years) Cross-section I Cross-section II
"*O(3L.c- n % (95% CL)* n % (95% CL)*
.K>rao' Cortical 50–54 473 4.4 (2.6–6.3) 338 7.4 (4.6–10.2)
>gqM|-uY 55–59 522 9.2 (6.7–11.7) 542 9.0 (6.6–11.5)
7Pu.<b} 60–64 615 16.4 (13.5–19.4) 556 16.7 (13.6–19.8)
4%/iu)nx 65–69 653 26.2 (22.8–29.6) 581 23.6 (20.1–27.0)
I_s4Pf[l 70–74 516 31.2 (27.2–35.2) 514 35.4 (31.3–39.6)
||TKo967] 75–79 366 40.2 (35.1–45.2) 332 39.8 (34.5–45.1)
Jsf-t 80–84 194 58.8 (51.8–65.8) 163 42.9 (35.3–50.6)
yD6lzuk{X 85–89 74 52.7 (41.1–64.4) 73 54.8 (43.1–66.5)
1DPgiIG~ 90+ 22 68.2 (47.0–89.3) 14 78.6 (54.0–103.2)
]i\C4* PSC 50–54 474 2.7 (1.3–4.2) 338 2.4 (0.7–4.0)
,zmGKn#n2 55–59 522 2.9 (1.4–4.3) 541 2.6 (1.3–3.9)
sV{M#UF2 60–64 616 4.6 (2.9–6.2) 548 5.7 (3.7–7.6)
b=<xzvy 65–69 655 6.3 (4.4–8.1) 573 4.5 (2.8–6.3)
V$O{s~@ti 70–74 517 6.8 (4.6–8.9) 505 9.7 (7.1–12.3)
~Y^
UP 75–79 367 11.4 (8.2–14.7) 327 9.5 (6.3–12.7)
qE73M5L& 80–84 196 12.2 (7.6–16.9) 155 10.3 (5.5–15.2)
n~xh
%r; 85–89 74 18.9 (9.8–28.1) 69 11.6 (3.9–19.4)
/L,VZ?CmtK 90+ 23 21.7 (3.5–40.0) 11 0.0
6X{RcX]/ Nuclear 50–54 323 1.6 (0.2–2.9) 331 0.9 (–0.2–1.9)
sG{hUsPa 55–59 386 2.3 (0.8–3.8) 507 3.6 (1.9–5.2)
pq0F!XmU 60–64 453 5.3 (3.2–7.4) 501 11.6 (8.8–14.4)
M5DW!^ 65–69 478 17.2 (13.8–20.1) 534 18.5 (15.2–21.9)
W~sP7&sp 70–74 392 27.6 (23.1–32.0) 453 36.0 (31.6–40.4)
|1vikG8 75–79 255 45.1 (39.0–51.3) 302 55.6 (50.0–61.3)
$7%e|0jC 80–84 146 54.1 (45.9–62.3) 147 73.5 (66.3–80.7)
F.:B_t 85–89 50 64.0 (50.2–77.8) 70 80.0 (70.4–89.6)
qF!oP 90+ 18 72.2 (49.3–95.1) 15 73.3 (48.0–98.7)
Gb]t%\ n = number of persons
}r`m(z$z * 95% Confidence Limits
]<\FtH Cataract FMioguunrtea i1n ps rEeyvea lSetnucdey in cross-sections I and II of the Blue
__Ei;%cV Cataract prevalence in cross-sections I and II of the Blue
}lZfZ?oAz Mountains Eye Study.
vMOI&_[\z 0
I@x^`^+l 10
fz
H$`X'M 20
XI#1) 30
P9j[
NEV 40
BfmSM9 50
"p<B| cortical PSC nuclear any
'urn5[i cataract
=bt/2nPV Cataract type
'xO5Le(=M %
o5(`7XV6D Cross-section I
{%WQQs Cross-section II
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n_}=G
RR (page number not for citation purposes)
(7 i@@ prevalence of any cataract (including cataract surgery) was
c#lW ? relatively stable over the 6-year period.
OV)J Although different population-based studies used different
y_bb//IAG grading systems to assess cataract [15], the overall
7v9l+OX,6 prevalence of the three cataract types were similar across
L`v7|! X different study populations [12,16-23]. Most studies have
DQ'yFPE suggested that nuclear cataract is the most prevalent type
YKF5|;} of cataract, followed by cortical cataract [16-20]. Ours and
d51.Tbt#%7 other studies reported that cortical cataract was the most
<3aiS?i.h prevalent type [12,21-23].
o[C,fh,$ Our age-specific prevalence data show a reduction of
7GN>o@ t 15.9% in cortical cataract prevalence for the 80–84 year
nW1Obu8x| age group, concordant with an increase in cataract surgery
ILsw' prevalence by 9% in those aged 80+ years observed in the
<=m@Sg{o same study population [10]. Although cortical cataract is
gmG
M[c \
thought to be the least likely cataract type leading to a cataract
Uy8r
!9O surgery, this may not be the case in all older persons.
oqu;
D'8 A relatively stable cortical cataract and PSC prevalence
>fCz,.L over the 6-year period is expected. We cannot offer a
_ ^5w f definitive explanation for the increase in nuclear cataract
C'4gve 7! prevalence. A possible explanation could be that a moderate
O3Jp:.ps level of nuclear cataract causes less visual disturbance
DI/yHs than the other two types of cataract, thus for the oldest age
@9yY`\"ed groups, persons with nuclear cataract could have been less
?!PpooYK likely to have surgery unless it is very dense or co-existing
ZbS*zKEW with cortical cataract or PSC. Previous studies have shown
Ns^[Hb[b' that functional vision and reading performance were high
!3Xu#^Xxj in patients undergoing cataract surgery who had nuclear
)`u)#@x cataract only compared to those with mixed type of cataract
fU@{!;|Pz (nuclear and cortical) or PSC [24,25]. In addition, the
$9_yD&& overall prevalence of any cataract (including cataract surgery)
tvh)N{j was similar in the two cross-sections, which appears
Q]9g
to support our speculation that in the oldest age group,
1trk nuclear cataract may have been less likely to be operated
&<Gs@UX~w than the other two types of cataract. This could have
eVDO]5? resulted in an increased nuclear cataract prevalence (due
FQc8j:' to less being operated), compensated by the decreased
:i
;iSrKy prevalence of cortical cataract and PSC (due to these being
gpo+-NnG more likely to be operated), leading to stable overall prevalence
OQ,KQ\ of any cataract.
2m$\]\kCUv Possible selection bias arising from selective survival
Rh%c<</`0s among persons without cataract could have led to underestimation
})zYo 7 of cataract prevalence in both surveys. We
t-, =sV
assume that such an underestimation occurred equally in
_z`g@[m
:t both surveys, and thus should not have influenced our
.fZ*N/ assessment of temporal changes.
pA
,xDs@37 Measurement error could also have partially contributed
!N, Oe< to the observed difference in nuclear cataract prevalence.
BQ We8D Assessment of nuclear cataract from photographs is a
Lm-yTMNPn potentially subjective process that can be influenced by
F;I % 9-R variations in photography (light exposure, focus and the
8efQ-^b. slit-lamp angle when the photograph was taken) and
Klw\ grading. Although we used the same Topcon slit-lamp
X>0$zE@0 camera and the same two graders who graded photos
4P1<Zi+< from both surveys, we are still not able to exclude the possibility
R~=_,JUW of a partial influence from photographic variation
-!p +^wC on this result.
QX1rnVzg0 A similar gender difference (women having a higher rate
5)IJ|"]y than men) in cortical cataract prevalence was observed in
G-54D_ 4 both surveys. Our findings are in keeping with observations
G4VdJ(_ from the Beaver Dam Eye Study [18], the Barbados
mJj
[f8 Eye Study [22] and the Lens Opacities Case-Control
-#9Hb.Q
; Group [26]. It has been suggested that the difference
J.R|Xd could be related to hormonal factors [18,22]. A previous
'G6M:IXno study on biochemical factors and cataract showed that a
#u<^ lower level of iron was associated with an increased risk of
'dkKBLsx cortical cataract [27]. No interaction between sex and biochemical
+{qX, factors were detected and no gender difference
@xO?SjH was assessed in this study [27]. The gender difference seen
_kgGz@/p in cortical cataract could be related to relatively low iron
:^G;`T`L levels and low hemoglobin concentration usually seen in
2l7Sbs7 women [28]. Diabetes is a known risk factor for cortical
hI&ugdf Table 3: Gender distribution of cataract types in cross-sections I and II.
k|O?qE1hP Cataract type Gender Cross-section I Cross-section II
0n'~wz"wB n % (95% CL)* n % (95% CL)*
efK3{
Cortical Male 1496 21.1 (19.0–23.1) 1328 20.4 (18.2–22.6)
t *8k3" Female 1939 25.9 (23.9–27.8) 1785 26.2 (24.2–28.3)
yMJY6$Ct PSC Male 1500 6.5 (5.2–7.7) 1314 6.4 (5.1–7.7)
cz2guUu Female 1944 6.2 (5.1–7.2) 1753 5.7 (4.6–6.7)
aMUy^>
Nuclear Male 1106 17.6 (15.4–19.9) 1225 22.5 (20.1–24.8)
4 ^=qc99 Female 1395 19.5 (17.4–21.6) 1635 25.0 (22.9–27.1)
[(hB%x_" n = number of persons
Hy?+p{{G * 95% Confidence Limits
#[4Mw M3 BMC Ophthalmology 2006, 6:17
http://www.biomedcentral.com/1471-2415/6/17 01/? Page 6 of 7
o(2tRDT\_b (page number not for citation purposes)
|L@9qwF cataract but in this particular population diabetes is more
oicj3xkw? prevalent in men than women in all age groups [29]. Differential
;yc|=I^ exposures to cataract risk factors or different dietary
ZL0':7 or lifestyle patterns between men and women may
K2W$I H:. also be related to these observations and warrant further
&oA p[] study.
8-A *Jc Conclusion
&$'=SL(Z In summary, in two population-based surveys 6 years
|o:[*2- apart, we have documented a relatively stable prevalence
#rE#lHo of cortical cataract and PSC over the period. The observed
HjX!a29Wf overall increased nuclear cataract prevalence by 5% over a
[lSQ? 6-year period needs confirmation by future studies, and
!A. Kb74 reasons for such an increase deserve further study.
b),_rr Competing interests
Ww{|:>j The author(s) declare that they have no competing interests.
Is87
9_Z Authors' contributions
:6^8Q,C1@ AGT graded the photographs, performed literature search
w|"cf{$^x and wrote the first draft of the manuscript. JJW graded the
|;L%hIR[
photographs, critically reviewed and modified the manuscript.
)$#
Ku2X ER performed the statistical analysis and critically
o9tvf|+z reviewed the manuscript. PM designed and directed the
JD\:bI study, adjudicated cataract cases and critically reviewed
jh3LD6|s} and modified the manuscript. All authors read and
STC'j1U
approved the final manuscript.
{kLL&`ii Acknowledgements
w% Ug9 This study was supported by the Australian National Health & Medical
..ig jc#UF Research Council, Canberra, Australia (Grant Nos 974159, 991407). The
.js@F/Hp abstract was presented at the Association for Research in Vision and Ophthalmology
(I?CW~3# (ARVO) meeting in Fort Lauderdale, Florida, USA, May 2005.
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