BioMed Central
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BJB'o BMC Ophthalmology
PZ
AyHXY Research article Open Access
qI5_@[S* Comparison of age-specific cataract prevalence in two
'>@evrG population-based surveys 6 years apart
Z ZX|MA! Ava Grace Tan†, Jie Jin Wang*†, Elena Rochtchina† and Paul Mitchell†
l]uF!']f Address: Centre for Vision Research, Westmead Millennium Institute, Department of Ophthalmology, University of Sydney, Westmead Hospital,
wHEt;rc( Westmead, NSW, Australia
OLXG0@ Email: Ava Grace Tan -
ava_tan@wmi.usyd.edu.au; Jie Jin Wang* -
jiejin_wang@wmi.usyd.edu.au;
9V9K3xWn Elena Rochtchina -
elena_rochtchina@wmi.usyd.edu.au; Paul Mitchell -
paul_mitchell@wmi.usyd.edu.au hDSt6O4za * Corresponding author †Equal contributors
R]/3`X9!d> Abstract
J)"2^?!&B Background: In this study, we aimed to compare age-specific cortical, nuclear and posterior
sV%<U-X subcapsular (PSC) cataract prevalence in two surveys 6 years apart.
B#OnooJI Methods: The Blue Mountains Eye Study examined 3654 participants (82.4% of those eligible) in
|'aGj cross-section I (1992–4) and 3509 participants (75.1% of survivors and 85.2% of newly eligible) in
Uz} #. cross-section II (1997–2000, 66.5% overlap with cross-section I). Cataract was assessed from lens
Wj(
O_2
photographs following the Wisconsin Cataract Grading System. Cortical cataract was defined if
)R(kXz=M cortical opacity comprised ≥ 5% of lens area. Nuclear cataract was defined if nuclear opacity ≥
gp`$/ci Wisconsin standard 4. PSC was defined if any present. Any cataract was defined to include persons
K7 -AVMY who had previous cataract surgery. Weighted kappa for inter-grader reliability was 0.82, 0.55 and
HQCxO? 0.82 for cortical, nuclear and PSC cataract, respectively. We assessed age-specific prevalence using
!D!~4h) an interval of 5 years, so that participants within each age group were independent between the
a`
s2 z two surveys.
nm`[\3R Results: Age and gender distributions were similar between the two populations. The age-specific
#^|y0:
prevalence of cortical (23.8% in 1st, 23.7% in 2nd) and PSC cataract (6.3%, 6.0%) was similar. The
,.A@U*j prevalence of nuclear cataract increased slightly from 18.7% to 23.9%. After age standardization,
/Nt#|C> the similar prevalence of cortical (23.8%, 23.5%) and PSC cataract (6.3%, 5.9%), and the increased
MxQhkY-= prevalence of nuclear cataract (18.7%, 24.2%) remained.
WYSqnmi Conclusion: In two surveys of two population-based samples with similar age and gender
Ti$G2dBO distributions, we found a relatively stable cortical and PSC cataract prevalence over a 6-year period.
%UT5KYd!=N The increased prevalence of nuclear cataract deserves further study.
-K eoq Background
:tBIo7 Age-related cataract is the leading cause of reversible visual
#.L9/b(
impairment in older persons [1-6]. In Australia, it is
b"H
c==` estimated that by the year 2021, the number of people
f>!)y- 7 affected by cataract will increase by 63%, due to population
kw{dvE\K aging [7]. Surgical intervention is an effective treatment
xvw @'| for cataract and normal vision (> 20/40) can usually
n_QSuh/Wn be restored with intraocular lens (IOL) implantation.
_N)/X|=~s Cataract surgery with IOL implantation is currently the
m#1>y} most commonly performed, and is, arguably, the most
'5V}Z3zJ/ cost effective surgical procedure worldwide. Performance
\kWL:uU Published: 20 April 2006
Pt5"q3ec{T BMC Ophthalmology 2006, 6:17 doi:10.1186/1471-2415-6-17
]8@s+N Received: 14 December 2005
fE`p Accepted: 20 April 2006
E+z),"QA This article is available from:
http://www.biomedcentral.com/1471-2415/6/17 Q\Wh]=} © 2006 Tan et al; licensee BioMed Central Ltd.
C 2t] This is an Open Access article distributed under the terms of the Creative Commons Attribution License (
http://creativecommons.org/licenses/by/2.0),
ncTPFv
H5 which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
f euAT
L] BMC Ophthalmology 2006, 6:17
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43wm_4C!H of this surgical procedure has been continuously increasing
$40G$w in the last two decades. Data from the Australian
^AhV1rBB Health Insurance Commission has shown a steady
5PY4PT=G increase in Medicare claims for cataract surgery [8]. A 2.6-
6-E>-9]'E fold increase in the total number of cataract procedures
@TJxU from 1985 to 1994 has been documented in Australia [9].
5
w-Pq&q The rate of cataract surgery per thousand persons aged 65
J.;!l years or older has doubled in the last 20 years [8,9]. In the
='A VI-go5 Blue Mountains Eye Study population, we observed a onethird
Es<& 6 increase in cataract surgery prevalence over a mean
b~$8<\ 6-year interval, from 6% to nearly 8% in two cross-sectional
e5AZU7%. population-based samples with a similar age range
h"0)g:\ [10]. Further increases in cataract surgery performance
[KQ#b would be expected as a result of improved surgical skills
!;3hN$5 and technique, together with extending cataract surgical
A"tE~m;"7 benefits to a greater number of older people and an
6Y`rQ/F increased number of persons with surgery performed on
E3hXs6P both eyes.
LZtO Q__B) Both the prevalence and incidence of age-related cataract
C'~Eq3 link directly to the demand for, and the outcome of, cataract
lvAKL>qX surgery and eye health care provision. This report
;n q"jm aimed to assess temporal changes in the prevalence of cortical
R ;k1(p and nuclear cataract and posterior subcapsular cataract
%i6/=
'u (PSC) in two cross-sectional population-based
\@[Y~: surveys 6 years apart.
!'eh@BU; Methods
d>gQgQ;g The Blue Mountains Eye Study (BMES) is a populationbased
}}qY,@eeX cohort study of common eye diseases and other
.],:pL9d health outcomes. The study involved eligible permanent
HV&i! M@T residents aged 49 years and older, living in two postcode
;il+C!6zpf areas in the Blue Mountains, west of Sydney, Australia.
k4d;4D? Participants were identified through a census and were
p;qFMzyS9 invited to participate. The study was approved at each
(A )f
r4 stage of the data collection by the Human Ethics Committees
XXw>h4hl of the University of Sydney and the Western Sydney
7{tU'`P> Area Health Service and adhered to the recommendations
eZ]>;5 of the Declaration of Helsinki. Written informed consent
<(t{C8>g% was obtained from each participant.
:q >)c] Details of the methods used in this study have been
u9{SG^ described previously [11]. The baseline examinations
`PZ\3SC'i (BMES cross-section I) were conducted during 1992–
SdF+b+P] 1994 and included 3654 (82.4%) of 4433 eligible residents.
cA+T-A] Follow-up examinations (BMES IIA) were conducted
p//mVH% during 1997–1999, with 2335 (75.0% of BMES
|!81M|H cross section I survivors) participating. A repeat census of
GkxQEL the same area was performed in 1999 and identified 1378
d/3bE*gr
newly eligible residents who moved into the area or the
6i;q=N$' eligible age group. During 1999–2000, 1174 (85.2%) of
Py?e+[cN this group participated in an extension study (BMES IIB).
ay
=B<|! BMES cross-section II thus includes BMES IIA (66.5%)
L=<$^ m and BMES IIB (33.5%) participants (n = 3509).
R, #szTu Similar procedures were used for all stages of data collection
B8unF=u at both surveys. A questionnaire was administered
m70AWG including demographic, family and medical history. A
'pyIMB?x detailed eye examination included subjective refraction,
f,kV slit-lamp (Topcon SL-7e camera, Topcon Optical Co,
<00nu'Ex1v Tokyo, Japan) and retroillumination (Neitz CT-R camera,
-'}#j\ Neitz Instrument Co, Tokyo, Japan) photography of the
\PD%=~ lens. Grading of lens photographs in the BMES has been
2I3H?Lrx!m previously described [12]. Briefly, masked grading was
)6B
ySk performed on the lens photographs using the Wisconsin
h@]{j_$u Cataract Grading System [13]. Cortical cataract and PSC
L8f_^
*, were assessed from the retroillumination photographs by
W0;QufV estimating the percentage of the circular grid involved.
]N,'3`&:: Cortical cataract was defined when cortical opacity
uP$i2Cy involved at least 5% of the total lens area. PSC was defined
x[fp7*TiG when opacity comprised at least 1% of the total lens area.
<Qr*!-Kc6 Slit-lamp photographs were used to assess nuclear cataract
M?Fv'YE using the Wisconsin standard set of four lens photographs
A
k~|r#@ [13]. Nuclear cataract was defined when nuclear opacity
C8do8$ was at least as great as the standard 4 photograph. Any cataract
4`'Rm/) was defined to include persons who had previous
mKE'l'9A_ cataract surgery as well as those with any of three cataract
EiP N44( types. Inter-grader reliability was high, with weighted
lYS " kappa 0.82 for cortical cataract, 0.55 (simple kappa 0.75)
nET<u; for nuclear cataract and 0.82 for PSC grading. The intragrader
S|;}]6p reliability for nuclear cataract was assessed with
oiM['iDK simple kappa 0.83 for the senior grader who graded
FI[]#
nuclear cataract at both surveys. All PSC cases were confirmed
J*zQ8\f=} by an ophthalmologist (PM).
S;/pm$?/ In cross-section I, 219 persons (6.0%) had missing or
s0CDp"uJY ungradable Neitz photographs, leaving 3435 with photographs
"r8N-
h/P available for cortical cataract and PSC assessment,
_,v>P2) while 1153 (31.6%) had randomly missing or ungradable
3g56[;Up? Topcon photographs due to a camera malfunction, leaving
I~E&::, 2501 with photographs available for nuclear cataract
T!pA$eE assessment. Comparison of characteristics between participants
+;*4.} with and without Neitz or Topcon photographs in
J9f]=1` cross-section I showed no statistically significant differences
![eY%2;< between the two groups, as reported previously
L^PBcfg [12]. In cross-section II, 441 persons (12.5%) had missing
>6W #v[ or ungradable Neitz photographs, leaving 3068 for cortical
EY.m,@{ cataract and PSC assessment, and 648 (18.5%) had
{%RwZ'
missing or ungradable Topcon photographs, leaving 2860
b\kA for nuclear cataract assessment.
&OkPO| Data analysis was performed using the Statistical Analysis
}7K~- System (SAS, SAS Institute, Cary, NC, USA). Age-adjusted
]3Ibl^J prevalence was calculated using direct standardization of
C[l5[DpH the cross-section II population to the cross-section I population.
kY9$ M8b We assessed age-specific prevalence using an
3hEbM'L interval of 5 years, so that participants within each age
hBifn\dFr group were independent between the two cross-sectional
dB QCr{7 surveys.
yMmUOIxk\ BMC Ophthalmology 2006, 6:17
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I47sq z7 (page number not for citation purposes)
5{IbKj| Results
r%>7n,+o Characteristics of the two survey populations have been
7{k?"NF previously compared [14] and showed that age and sex
fP8bWZ{ distributions were similar. Table 1 compares participant
Po.by~| characteristics between the two cross-sections. Cross-section
1zCgPiAem II participants generally had higher rates of diabetes,
dQAF;L hypertension, myopia and more users of inhaled steroids.
QF22_D<.}J Cataract prevalence rates in cross-sections I and II are
^X"x,8}&V shown in Figure 1. The overall prevalence of cortical cataract
5`i+aH( was 23.8% and 23.7% in cross-sections I and II,
'z=d&K respectively (age-sex adjusted P = 0.81). Corresponding
*Uf>Xr& prevalence of PSC was 6.3% and 6.0% for the two crosssections
YM
. (age-sex adjusted P = 0.60). There was an
mgodvX increased prevalence of nuclear cataract, from 18.7% in
6TXTJ]er cross-section I to 23.9% in cross-section II over the 6-year
^ ]+vtk period (age-sex adjusted P < 0.001). Prevalence of any cataract
[9F (including persons who had cataract surgery), however,
tbfwgK was relatively stable (46.9% and 46.8% in crosssections
I=
cayR I and II, respectively).
^V]IPGV After age-standardization, these prevalence rates remained
LW9F%?e!> stable for cortical cataract (23.8% and 23.5% in the two
b?,=|H surveys) and PSC (6.3% and 5.9%). The slightly increased
K*p3#iB prevalence of nuclear cataract (from 18.7% to 24.2%) was
4AF.KX7 not altered.
k%aJ%( Table 2 shows the age-specific prevalence rates for cortical
e5'U[bQm cataract, PSC and nuclear cataract in cross-sections I and
X/m
~^ II. A similar trend of increasing cataract prevalence with
f9)0OHa increasing age was evident for all three types of cataract in
_?eT[!oO8 both surveys. Comparing the age-specific prevalence
M~+DxnJ= between the two surveys, a reduction in PSC prevalence in
CW.T`F cross-section II was observed in the older age groups (≥ 75
#3A|Z=,5 years). In contrast, increased nuclear cataract prevalence
$e{}SQ;fW in cross-section II was observed in the older age groups (≥
jx
?"`;a 70 years). Age-specific cortical cataract prevalence was relatively
~)6EH`- consistent between the two surveys, except for a
MN:LL
< reduction in prevalence observed in the 80–84 age group
(Ap?ixrR_ and an increasing prevalence in the older age groups (≥ 85
,K|UUosS-# years).
/a6i` Similar gender differences in cataract prevalence were
\eRct_ observed in both surveys (Table 3). Higher prevalence of
1y,/|
Y cortical and nuclear cataract in women than men was evident
k)W&ZY but the difference was only significant for cortical
}XqC'z cataract (age-adjusted odds ratio, OR, for women 1.3,
ofPv?_@ 95% confidence intervals, CI, 1.1–1.5 in cross-section I
i)$<j!L and OR 1.4, 95% CI 1.1–1.6 in cross-section II). In con-
W! J@30 Table 1: Participant characteristics.
z*9 ke Characteristics Cross-section I Cross-section II
S6fbwZZMG n % n %
5du xW>D Age (mean) (66.2) (66.7)
6qWWfm/6 50–54 485 13.3 350 10.0
jdx T662q 55–59 534 14.6 580 16.5
MIh\z7gW 60–64 638 17.5 600 17.1
Jb-.x_Bf 65–69 671 18.4 639 18.2
Pw5[X5.DX 70–74 538 14.7 572 16.3
Ch:EL-L 75–79 422 11.6 407 11.6
*dPbV.HCl 80–84 230 6.3 226 6.4
;V?d;O4u 85–89 100 2.7 110 3.1
2.
v<pqn 90+ 36 1.0 24 0.7
{Byh:-e< Female 2072 56.7 1998 57.0
{w7/M]m- Ever Smokers 1784 51.2 1789 51.2
IIAmx[ b Use of inhaled steroids 370 10.94 478 13.8^
4yjIR? History of:
aPQxpK? Diabetes 284 7.8 347 9.9^
%Y>E
Hypertension 1669 46.0 1825 52.2^
!SIk9~rJ Emmetropia* 1558 42.9 1478 42.2
W!Fc60>p@f Myopia* 442 12.2 495 14.1^
[AA}P/iW Hyperopia* 1633 45.0 1532 43.7
5L_`Fw\l n = number of persons affected
Yy6$q\@rV * best spherical equivalent refraction correction
II!~"-WH ^ P < 0.01
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l5\V4 t
EdkIT|c{ rast, men had slightly higher PSC prevalence than women
G=SMz+z in both cross-sections but the difference was not significant
b&dv("e
4 (OR 1.1, 95% CI 0.8–1.4 for men in cross-section I
iRbe$v&N and OR 1.2, 95% 0.9–1.6 in cross-section II).
't5`Ni Discussion
"Mhn?PTq Findings from two surveys of BMES cross-sectional populations
U4<c![Pp. with similar age and gender distribution showed
6U.|0mG[ that the prevalence of cortical cataract and PSC remained
z?( b|v stable, while the prevalence of nuclear cataract appeared
I~&9c/& to have increased. Comparison of age-specific prevalence,
qZ&~&f|>e with totally independent samples within each age group,
i^V(LGQF confirmed the robustness of our findings from the two
D W^Zuu/) survey samples. Although lens photographs taken from
M.r7^9 P the two surveys were graded for nuclear cataract by the
ZfK[o{9> same graders, who documented a high inter- and intragrader
,?k1if(0[ reliability, we cannot exclude the possibility that
{]Hv*{ ] variations in photography, performed by different photographers,
OZnKJ< may have contributed to the observed difference
&i.sSqSI5 in nuclear cataract prevalence. However, the overall
CxZh^V8LP Table 2: Age-specific prevalence of cataract types in cross sections I and II.
G\TO]c Cataract type Age (years) Cross-section I Cross-section II
^gZ,A]
n % (95% CL)* n % (95% CL)*
nSC2wTH!1 Cortical 50–54 473 4.4 (2.6–6.3) 338 7.4 (4.6–10.2)
?Ve IlD 55–59 522 9.2 (6.7–11.7) 542 9.0 (6.6–11.5)
K +3=gBU*w 60–64 615 16.4 (13.5–19.4) 556 16.7 (13.6–19.8)
3RT\G0?8f 65–69 653 26.2 (22.8–29.6) 581 23.6 (20.1–27.0)
13`Mt1R 70–74 516 31.2 (27.2–35.2) 514 35.4 (31.3–39.6)
v{fcQb 75–79 366 40.2 (35.1–45.2) 332 39.8 (34.5–45.1)
;}"Eqq: 80–84 194 58.8 (51.8–65.8) 163 42.9 (35.3–50.6)
m<#12#D 85–89 74 52.7 (41.1–64.4) 73 54.8 (43.1–66.5)
]|+M0:2? 90+ 22 68.2 (47.0–89.3) 14 78.6 (54.0–103.2)
kuV7nsXiQ PSC 50–54 474 2.7 (1.3–4.2) 338 2.4 (0.7–4.0)
F!wz{i6\h 55–59 522 2.9 (1.4–4.3) 541 2.6 (1.3–3.9)
n=vDEX:' 60–64 616 4.6 (2.9–6.2) 548 5.7 (3.7–7.6)
f
zQR0
65–69 655 6.3 (4.4–8.1) 573 4.5 (2.8–6.3)
~~Ezt*lH 70–74 517 6.8 (4.6–8.9) 505 9.7 (7.1–12.3)
\/o$io,kV 75–79 367 11.4 (8.2–14.7) 327 9.5 (6.3–12.7)
5$D "uAp<V 80–84 196 12.2 (7.6–16.9) 155 10.3 (5.5–15.2)
5;U Iz@BJ 85–89 74 18.9 (9.8–28.1) 69 11.6 (3.9–19.4)
*_o(~5w-K 90+ 23 21.7 (3.5–40.0) 11 0.0
HdJ g Nuclear 50–54 323 1.6 (0.2–2.9) 331 0.9 (–0.2–1.9)
,_I
rE 55–59 386 2.3 (0.8–3.8) 507 3.6 (1.9–5.2)
U`mX
f#D 60–64 453 5.3 (3.2–7.4) 501 11.6 (8.8–14.4)
P<<+;'] 65–69 478 17.2 (13.8–20.1) 534 18.5 (15.2–21.9)
"J 1A9| 70–74 392 27.6 (23.1–32.0) 453 36.0 (31.6–40.4)
89g
a+#7 75–79 255 45.1 (39.0–51.3) 302 55.6 (50.0–61.3)
VTM* 1uXS> 80–84 146 54.1 (45.9–62.3) 147 73.5 (66.3–80.7)
|JxVfX8^ 85–89 50 64.0 (50.2–77.8) 70 80.0 (70.4–89.6)
!i^"3!.l,] 90+ 18 72.2 (49.3–95.1) 15 73.3 (48.0–98.7)
pO
c2V n = number of persons
4a+gM._+O * 95% Confidence Limits
f
+{=##'0 Cataract FMioguunrtea i1n ps rEeyvea lSetnucdey in cross-sections I and II of the Blue
alaL/p{O Cataract prevalence in cross-sections I and II of the Blue
$Es\ld Mountains Eye Study.
/I=|;FGq 0
5@w6pda 10
w={q@.
g% 20
c\{N:S> 30
sFTAE1| 40
Z8#nu 50
\yr9j$ cortical PSC nuclear any
XB7Aa) cataract
0Z1ksfLU Cataract type
""0Y^M2I %
|Vx[ Cross-section I
"GO!^ZG] Cross-section II
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_O`p (6 (page number not for citation purposes)
P R
%)3 prevalence of any cataract (including cataract surgery) was
xsZG(Tz relatively stable over the 6-year period.
:?6HG_9X Although different population-based studies used different
,8@<sFB' grading systems to assess cataract [15], the overall
J:@gmo`M;V prevalence of the three cataract types were similar across
k pgA2u7 different study populations [12,16-23]. Most studies have
L 4j#0I]lq suggested that nuclear cataract is the most prevalent type
E>bkEm of cataract, followed by cortical cataract [16-20]. Ours and
r1L@p[> other studies reported that cortical cataract was the most
7;EDU prevalent type [12,21-23].
:#YC_
id Our age-specific prevalence data show a reduction of
Q,KNZxT,
q 15.9% in cortical cataract prevalence for the 80–84 year
w2
Y%yjCV age group, concordant with an increase in cataract surgery
46>rvy.r prevalence by 9% in those aged 80+ years observed in the
Msqqjhoy same study population [10]. Although cortical cataract is
*9\j1Nd thought to be the least likely cataract type leading to a cataract
xt^1,V4Ei~ surgery, this may not be the case in all older persons.
ZmsYRk~@- A relatively stable cortical cataract and PSC prevalence
IuXgxR% over the 6-year period is expected. We cannot offer a
QX=T
uyO definitive explanation for the increase in nuclear cataract
%1i:*~g prevalence. A possible explanation could be that a moderate
^~~Rto)Y level of nuclear cataract causes less visual disturbance
fd'kv than the other two types of cataract, thus for the oldest age
<=.6Z*x+ groups, persons with nuclear cataract could have been less
rfwJLl/
likely to have surgery unless it is very dense or co-existing
Y_%:%J with cortical cataract or PSC. Previous studies have shown
<XLae'R that functional vision and reading performance were high
xS|9Gk in patients undergoing cataract surgery who had nuclear
^Q8yb*MN cataract only compared to those with mixed type of cataract
u@_|4Bp," (nuclear and cortical) or PSC [24,25]. In addition, the
Ey=2zo^F overall prevalence of any cataract (including cataract surgery)
c(Dp`f, was similar in the two cross-sections, which appears
wkp2A18n to support our speculation that in the oldest age group,
~@'wqGTp nuclear cataract may have been less likely to be operated
/|v4]t-
than the other two types of cataract. This could have
</25J(( resulted in an increased nuclear cataract prevalence (due
D6VdgU| to less being operated), compensated by the decreased
p"0#G&- prevalence of cortical cataract and PSC (due to these being
w9|
x{B more likely to be operated), leading to stable overall prevalence
.n7@$kq of any cataract.
V(`]hH0;T Possible selection bias arising from selective survival
T_*inPf among persons without cataract could have led to underestimation
[<XYU,{R of cataract prevalence in both surveys. We
Vlx.C~WYn assume that such an underestimation occurred equally in
6_`Bo% both surveys, and thus should not have influenced our
R'gd/.[e assessment of temporal changes.
_[[0rn$ Measurement error could also have partially contributed
V?EX`2S to the observed difference in nuclear cataract prevalence.
`4K|L6 Assessment of nuclear cataract from photographs is a
U`6|K$@ potentially subjective process that can be influenced by
6Q :Wo)^! variations in photography (light exposure, focus and the
sK#)k\w> slit-lamp angle when the photograph was taken) and
a_Xwi:e< grading. Although we used the same Topcon slit-lamp
1]/;qNEv camera and the same two graders who graded photos
$NR[U+ from both surveys, we are still not able to exclude the possibility
JMB#KzvN[ of a partial influence from photographic variation
HGYTh"R on this result.
1{N+B#*<[X A similar gender difference (women having a higher rate
0`E G-Hw than men) in cortical cataract prevalence was observed in
f&CQn.K" both surveys. Our findings are in keeping with observations
ec; from the Beaver Dam Eye Study [18], the Barbados
3@
" :& Eye Study [22] and the Lens Opacities Case-Control
M0$MK> Group [26]. It has been suggested that the difference
[RXLR# could be related to hormonal factors [18,22]. A previous
T+L=GnYl study on biochemical factors and cataract showed that a
#e@NV4q lower level of iron was associated with an increased risk of
E
3 % ~!ZC cortical cataract [27]. No interaction between sex and biochemical
t"B3?<?] factors were detected and no gender difference
~Eg]Auk7 was assessed in this study [27]. The gender difference seen
vb[
0H{TT2 in cortical cataract could be related to relatively low iron
jSpj6:@B levels and low hemoglobin concentration usually seen in
w1I07 ( women [28]. Diabetes is a known risk factor for cortical
Z5xQ
-T` Table 3: Gender distribution of cataract types in cross-sections I and II.
"SN*hzs"]` Cataract type Gender Cross-section I Cross-section II
+.~K=.O) n % (95% CL)* n % (95% CL)*
81EEYf Cortical Male 1496 21.1 (19.0–23.1) 1328 20.4 (18.2–22.6)
v7pu Female 1939 25.9 (23.9–27.8) 1785 26.2 (24.2–28.3)
Z7bJ<TpZ PSC Male 1500 6.5 (5.2–7.7) 1314 6.4 (5.1–7.7)
(d#&m+
g] Female 1944 6.2 (5.1–7.2) 1753 5.7 (4.6–6.7)
x1Gx9z9 Nuclear Male 1106 17.6 (15.4–19.9) 1225 22.5 (20.1–24.8)
oJD]h/fQs Female 1395 19.5 (17.4–21.6) 1635 25.0 (22.9–27.1)
x_~_/&X5 n = number of persons
,Vq$>T@z * 95% Confidence Limits
oz=V|7
, BMC Ophthalmology 2006, 6:17
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\i+AMduAo (page number not for citation purposes)
_FOIMjh%N cataract but in this particular population diabetes is more
6/ 5c| prevalent in men than women in all age groups [29]. Differential
(W#CDw<ja exposures to cataract risk factors or different dietary
uD(C jHM> or lifestyle patterns between men and women may
qRaPh:Q' also be related to these observations and warrant further
eGT&&Y study.
Ye]K 74M. Conclusion
.u\$wJ9Ai In summary, in two population-based surveys 6 years
{X<g93 apart, we have documented a relatively stable prevalence
G>"n6v'^d of cortical cataract and PSC over the period. The observed
5/Qu5/ overall increased nuclear cataract prevalence by 5% over a
0S:&wb 6-year period needs confirmation by future studies, and
2OpA1$n6 reasons for such an increase deserve further study.
x"sbm Competing interests
O[= L#wi The author(s) declare that they have no competing interests.
lv?`+tU2_ Authors' contributions
4L:O0Ggz} AGT graded the photographs, performed literature search
?{aC-3VAT and wrote the first draft of the manuscript. JJW graded the
&[{sA; photographs, critically reviewed and modified the manuscript.
OIj.K@Kr ER performed the statistical analysis and critically
Z$INmo6 reviewed the manuscript. PM designed and directed the
Q9AvNj>X study, adjudicated cataract cases and critically reviewed
sN8pwRj b and modified the manuscript. All authors read and
bvJ@H
Z$
approved the final manuscript.
,mx\
-lWFy Acknowledgements
e YP^.U) This study was supported by the Australian National Health & Medical
= r/8~~= Research Council, Canberra, Australia (Grant Nos 974159, 991407). The
2]?=\_T abstract was presented at the Association for Research in Vision and Ophthalmology
59{X; (ARVO) meeting in Fort Lauderdale, Florida, USA, May 2005.
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