BioMed Central
8ap%? Page 1 of 7
YwjKAyLU (page number not for citation purposes)
Yp^rR }N BMC Ophthalmology
rE.;g^4p Research article Open Access
]H+8rY%+ Comparison of age-specific cataract prevalence in two
klT@cO-9 population-based surveys 6 years apart
.uMn0PE Ava Grace Tan†, Jie Jin Wang*†, Elena Rochtchina† and Paul Mitchell†
2{H@(Vgpbr Address: Centre for Vision Research, Westmead Millennium Institute, Department of Ophthalmology, University of Sydney, Westmead Hospital,
c7x
~{V8 Westmead, NSW, Australia
*Doa*wQ Email: Ava Grace Tan -
ava_tan@wmi.usyd.edu.au; Jie Jin Wang* -
jiejin_wang@wmi.usyd.edu.au;
RAgg:
3^ Elena Rochtchina -
elena_rochtchina@wmi.usyd.edu.au; Paul Mitchell -
paul_mitchell@wmi.usyd.edu.au Ch<[l8;K * Corresponding author †Equal contributors
BBwy,\o# Abstract
1W^taJH] Background: In this study, we aimed to compare age-specific cortical, nuclear and posterior
1mOh{:1u subcapsular (PSC) cataract prevalence in two surveys 6 years apart.
nrub*BuA Methods: The Blue Mountains Eye Study examined 3654 participants (82.4% of those eligible) in
e> e}vZlX cross-section I (1992–4) and 3509 participants (75.1% of survivors and 85.2% of newly eligible) in
Nfrw0b cross-section II (1997–2000, 66.5% overlap with cross-section I). Cataract was assessed from lens
>UiYL}'br6 photographs following the Wisconsin Cataract Grading System. Cortical cataract was defined if
K
*LlW@ cortical opacity comprised ≥ 5% of lens area. Nuclear cataract was defined if nuclear opacity ≥
ib#KpEk Wisconsin standard 4. PSC was defined if any present. Any cataract was defined to include persons
Z>:NPZODf who had previous cataract surgery. Weighted kappa for inter-grader reliability was 0.82, 0.55 and
CQF:Rnb 0.82 for cortical, nuclear and PSC cataract, respectively. We assessed age-specific prevalence using
Lt?lv2k=L an interval of 5 years, so that participants within each age group were independent between the
~=M7 3U# two surveys.
qouhuH_WtJ Results: Age and gender distributions were similar between the two populations. The age-specific
,8U&?8l prevalence of cortical (23.8% in 1st, 23.7% in 2nd) and PSC cataract (6.3%, 6.0%) was similar. The
x<tb
prevalence of nuclear cataract increased slightly from 18.7% to 23.9%. After age standardization,
wh$sn:J the similar prevalence of cortical (23.8%, 23.5%) and PSC cataract (6.3%, 5.9%), and the increased
UZ\u;/} prevalence of nuclear cataract (18.7%, 24.2%) remained.
V_:1EBzz Conclusion: In two surveys of two population-based samples with similar age and gender
+%yfcyZ. distributions, we found a relatively stable cortical and PSC cataract prevalence over a 6-year period.
4tRYw0f47 The increased prevalence of nuclear cataract deserves further study.
Xv ]W(f1 Background
N)uSG&S: Age-related cataract is the leading cause of reversible visual
I0D(F
i impairment in older persons [1-6]. In Australia, it is
i1ixi\P{0 estimated that by the year 2021, the number of people
'N (:@]4N affected by cataract will increase by 63%, due to population
|mxDjgq aging [7]. Surgical intervention is an effective treatment
<=zQ NBtx for cataract and normal vision (> 20/40) can usually
u^@f&BIG]: be restored with intraocular lens (IOL) implantation.
h5*JkRm Cataract surgery with IOL implantation is currently the
hgYZOwQ most commonly performed, and is, arguably, the most
&FMc?wq cost effective surgical procedure worldwide. Performance
+nrbShV Published: 20 April 2006
PS)4 I&;U BMC Ophthalmology 2006, 6:17 doi:10.1186/1471-2415-6-17
7OcWC-< Received: 14 December 2005
*'Sd/%8{ Accepted: 20 April 2006
%<\vGqsM This article is available from:
http://www.biomedcentral.com/1471-2415/6/17 N({MPO9 © 2006 Tan et al; licensee BioMed Central Ltd.
DrKP%BnS This is an Open Access article distributed under the terms of the Creative Commons Attribution License (
http://creativecommons.org/licenses/by/2.0),
F&4rO\aC"/ which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
}
MJy
+Z8& BMC Ophthalmology 2006, 6:17
http://www.biomedcentral.com/1471-2415/6/17 hQ,ch[j' Page 2 of 7
[<Mx2<8f (page number not for citation purposes)
ne>pOK<vZ of this surgical procedure has been continuously increasing
>!eAM ) in the last two decades. Data from the Australian
((YMVe Health Insurance Commission has shown a steady
RD!&LFz/} increase in Medicare claims for cataract surgery [8]. A 2.6-
LC,F
<>w1 fold increase in the total number of cataract procedures
pj\u9
L_
from 1985 to 1994 has been documented in Australia [9].
29;?I3<
* The rate of cataract surgery per thousand persons aged 65
H*d9l2,KZS years or older has doubled in the last 20 years [8,9]. In the
[T8WThs Blue Mountains Eye Study population, we observed a onethird
N H[kNi' increase in cataract surgery prevalence over a mean
1T"`vtR 6-year interval, from 6% to nearly 8% in two cross-sectional
Yz<3JRw population-based samples with a similar age range
]0Y4U7W [10]. Further increases in cataract surgery performance
Y>dF5&(kb would be expected as a result of improved surgical skills
3atBX5 and technique, together with extending cataract surgical
5#HW2"7 benefits to a greater number of older people and an
.M qP_Z', increased number of persons with surgery performed on
;;!
yC both eyes.
J4k=A7^N Both the prevalence and incidence of age-related cataract
P}Gj%4/G link directly to the demand for, and the outcome of, cataract
R|6Cv3: surgery and eye health care provision. This report
tZ]?^_Y1 aimed to assess temporal changes in the prevalence of cortical
)MtF23k)g and nuclear cataract and posterior subcapsular cataract
b:U$x20n$ (PSC) in two cross-sectional population-based
Xc =Y surveys 6 years apart.
:">!r.Q Methods
pd:WEI
, The Blue Mountains Eye Study (BMES) is a populationbased
K%,2=. cohort study of common eye diseases and other
@D]5c ivm_ health outcomes. The study involved eligible permanent
<ykU6=
residents aged 49 years and older, living in two postcode
b(,M1.[qt areas in the Blue Mountains, west of Sydney, Australia.
j@AIK+0Qc Participants were identified through a census and were
@bi}W` invited to participate. The study was approved at each
=-0/k;^ stage of the data collection by the Human Ethics Committees
9>=;FY of the University of Sydney and the Western Sydney
G'nmllB`] Area Health Service and adhered to the recommendations
034iK[ib" of the Declaration of Helsinki. Written informed consent
TtK[nP was obtained from each participant.
#oS<E1 Details of the methods used in this study have been
KKb,d0T[ described previously [11]. The baseline examinations
L 8c0lx}Nn (BMES cross-section I) were conducted during 1992–
6,^>mNm 1994 and included 3654 (82.4%) of 4433 eligible residents.
a1g,@0s Follow-up examinations (BMES IIA) were conducted
](Xb_xMf during 1997–1999, with 2335 (75.0% of BMES
ML}J\7R cross section I survivors) participating. A repeat census of
\Q {m9fE the same area was performed in 1999 and identified 1378
[xK3F+ newly eligible residents who moved into the area or the
'S20\hwt- eligible age group. During 1999–2000, 1174 (85.2%) of
6gkV*|U,e this group participated in an extension study (BMES IIB).
1Rt33\1J0 BMES cross-section II thus includes BMES IIA (66.5%)
48J@CvU and BMES IIB (33.5%) participants (n = 3509).
'<gI8W</ Similar procedures were used for all stages of data collection
*zaQx+L at both surveys. A questionnaire was administered
:W"~
{~#? including demographic, family and medical history. A
`A,-@`p detailed eye examination included subjective refraction,
t DO=P
c slit-lamp (Topcon SL-7e camera, Topcon Optical Co,
3>3 Kwc~E Tokyo, Japan) and retroillumination (Neitz CT-R camera,
Ij 79~pn Neitz Instrument Co, Tokyo, Japan) photography of the
l.(v^3:X lens. Grading of lens photographs in the BMES has been
FK^p")i previously described [12]. Briefly, masked grading was
FW;m\vu performed on the lens photographs using the Wisconsin
OP;v bZ Cataract Grading System [13]. Cortical cataract and PSC
j9m_jv were assessed from the retroillumination photographs by
u6J8"<
-W estimating the percentage of the circular grid involved.
W4t;{b Cortical cataract was defined when cortical opacity
nI[os involved at least 5% of the total lens area. PSC was defined
;Y)w@
bNt@ when opacity comprised at least 1% of the total lens area.
#`~C)=- Slit-lamp photographs were used to assess nuclear cataract
r^2p*nr} using the Wisconsin standard set of four lens photographs
@MoKWfc [13]. Nuclear cataract was defined when nuclear opacity
.[YuRLGz was at least as great as the standard 4 photograph. Any cataract
Plc-4y1 was defined to include persons who had previous
&g#@3e1> cataract surgery as well as those with any of three cataract
"x%Htq@ types. Inter-grader reliability was high, with weighted
%J#YM'g kappa 0.82 for cortical cataract, 0.55 (simple kappa 0.75)
pD(j'[ for nuclear cataract and 0.82 for PSC grading. The intragrader
5b5x!do reliability for nuclear cataract was assessed with
L]yS[UN$ simple kappa 0.83 for the senior grader who graded
1v#%Ei$6`t nuclear cataract at both surveys. All PSC cases were confirmed
Cwr~HY by an ophthalmologist (PM).
5CuuG<0 In cross-section I, 219 persons (6.0%) had missing or
{baq+ ungradable Neitz photographs, leaving 3435 with photographs
U1Q:= yD available for cortical cataract and PSC assessment,
vp1941P while 1153 (31.6%) had randomly missing or ungradable
6e (Qwt Topcon photographs due to a camera malfunction, leaving
rW<KKGsRWQ 2501 with photographs available for nuclear cataract
ysJQb~2q assessment. Comparison of characteristics between participants
)S3\,S-. with and without Neitz or Topcon photographs in
{]*c
29b> cross-section I showed no statistically significant differences
:1 ^LsLr5 between the two groups, as reported previously
,ZaRy$? [12]. In cross-section II, 441 persons (12.5%) had missing
czA5n or ungradable Neitz photographs, leaving 3068 for cortical
N1Ng^aY0 cataract and PSC assessment, and 648 (18.5%) had
v>:Ur}u!D missing or ungradable Topcon photographs, leaving 2860
imo$-}A for nuclear cataract assessment.
(
)2I# Data analysis was performed using the Statistical Analysis
7X`l&7IXP System (SAS, SAS Institute, Cary, NC, USA). Age-adjusted
~Uj=^leYO prevalence was calculated using direct standardization of
:Hn6b$Vy8 the cross-section II population to the cross-section I population.
i=ea
?eT` We assessed age-specific prevalence using an
5:\},n+VE interval of 5 years, so that participants within each age
C\\~E9+ group were independent between the two cross-sectional
>/g#lS 5 surveys.
Z.c'Hs+; BMC Ophthalmology 2006, 6:17
http://www.biomedcentral.com/1471-2415/6/17 d<% z
1Dj2 Page 3 of 7
"76]u) (page number not for citation purposes)
%u? ># Results
?iPC* Characteristics of the two survey populations have been
//*
fSF previously compared [14] and showed that age and sex
l-fi%Z7C distributions were similar. Table 1 compares participant
|)nZ^Cc characteristics between the two cross-sections. Cross-section
7zA'ri3w II participants generally had higher rates of diabetes,
={_C&57N1 hypertension, myopia and more users of inhaled steroids.
~F7-HaQJ Cataract prevalence rates in cross-sections I and II are
mi
ik%7>W shown in Figure 1. The overall prevalence of cortical cataract
fg
s!v7 was 23.8% and 23.7% in cross-sections I and II,
f) zn TJL respectively (age-sex adjusted P = 0.81). Corresponding
gaQdG=G8$ prevalence of PSC was 6.3% and 6.0% for the two crosssections
?u-|>N> (age-sex adjusted P = 0.60). There was an
7/!8e.M\ increased prevalence of nuclear cataract, from 18.7% in
5)FJ
:1- cross-section I to 23.9% in cross-section II over the 6-year
io _1Y]N period (age-sex adjusted P < 0.001). Prevalence of any cataract
x8wD0D
(including persons who had cataract surgery), however,
Vc_'hz]Z was relatively stable (46.9% and 46.8% in crosssections
FQm`~rA~zt I and II, respectively).
V}bjK8$$ After age-standardization, these prevalence rates remained
j!_;1++q stable for cortical cataract (23.8% and 23.5% in the two
A$<.a'&T! surveys) and PSC (6.3% and 5.9%). The slightly increased
&{ay=Mj prevalence of nuclear cataract (from 18.7% to 24.2%) was
./,/y"x not altered.
qo p^;~ Table 2 shows the age-specific prevalence rates for cortical
GO8GJ;B-U cataract, PSC and nuclear cataract in cross-sections I and
, 0imiv II. A similar trend of increasing cataract prevalence with
os,* 3WO increasing age was evident for all three types of cataract in
y603$Cv both surveys. Comparing the age-specific prevalence
/~}}"zx& between the two surveys, a reduction in PSC prevalence in
~$ng^D cross-section II was observed in the older age groups (≥ 75
?6Jx@ Sh years). In contrast, increased nuclear cataract prevalence
Ai:BEPKe in cross-section II was observed in the older age groups (≥
]gm
exa=(i 70 years). Age-specific cortical cataract prevalence was relatively
:ZTc7} consistent between the two surveys, except for a
wLmhy, reduction in prevalence observed in the 80–84 age group
plUZ"Tr and an increasing prevalence in the older age groups (≥ 85
b6}H$Sx~ years).
?kWC}k{ Similar gender differences in cataract prevalence were
uxW~uEh observed in both surveys (Table 3). Higher prevalence of
WP?TX b`5 cortical and nuclear cataract in women than men was evident
hn^<;av= but the difference was only significant for cortical
{6"Ph(I1 cataract (age-adjusted odds ratio, OR, for women 1.3,
eAXc:222 95% confidence intervals, CI, 1.1–1.5 in cross-section I
(&}i`}v_ and OR 1.4, 95% CI 1.1–1.6 in cross-section II). In con-
AmaT0tzJC Table 1: Participant characteristics.
'ixwD^x Characteristics Cross-section I Cross-section II
x97
j n % n %
,
8:(OB|a Age (mean) (66.2) (66.7)
e<=cdze 50–54 485 13.3 350 10.0
iM
I lZ 55–59 534 14.6 580 16.5
/4c\K-Z; 60–64 638 17.5 600 17.1
:,Pn3xl 65–69 671 18.4 639 18.2
My<snmr2d 70–74 538 14.7 572 16.3
<%maDM^_\( 75–79 422 11.6 407 11.6
[21=5S
80–84 230 6.3 226 6.4
99}(~B 85–89 100 2.7 110 3.1
gUxP>hB 90+ 36 1.0 24 0.7
t"
k*PA Female 2072 56.7 1998 57.0
E0u~i59Z Ever Smokers 1784 51.2 1789 51.2
U4gF(Q Use of inhaled steroids 370 10.94 478 13.8^
(@t(?Js History of:
\<y`!"c
Diabetes 284 7.8 347 9.9^
q0$
!y!~ Hypertension 1669 46.0 1825 52.2^
_acE
:H Emmetropia* 1558 42.9 1478 42.2
)^4\,u\@ Myopia* 442 12.2 495 14.1^
11<Qxu$rL Hyperopia* 1633 45.0 1532 43.7
Z0 o~+Ct$ n = number of persons affected
}&n<uUD H * best spherical equivalent refraction correction
x/;bu W- ^ P < 0.01
P5
K' p5}# BMC Ophthalmology 2006, 6:17
http://www.biomedcentral.com/1471-2415/6/17 bKrhIU[ Page 4 of 7
Z$0uH* h (page number not for citation purposes)
GG@md_ t
x9;gT&@H rast, men had slightly higher PSC prevalence than women
}RHn)}+ in both cross-sections but the difference was not significant
(xVsDAp=@ (OR 1.1, 95% CI 0.8–1.4 for men in cross-section I
Q(<)KZIK and OR 1.2, 95% 0.9–1.6 in cross-section II).
^go7_y Discussion
F8;dKyT?q Findings from two surveys of BMES cross-sectional populations
7VMvF/ap]u with similar age and gender distribution showed
&_~+( that the prevalence of cortical cataract and PSC remained
\>CYC| stable, while the prevalence of nuclear cataract appeared
B>GE9y5 to have increased. Comparison of age-specific prevalence,
&_"]5/"( with totally independent samples within each age group,
hO';
{Nl/$ confirmed the robustness of our findings from the two
|1b_3?e survey samples. Although lens photographs taken from
]3g?hM6
the two surveys were graded for nuclear cataract by the
GDD '[; same graders, who documented a high inter- and intragrader
tQH+)* reliability, we cannot exclude the possibility that
q-c=nkN3 variations in photography, performed by different photographers,
Y=?yhAw may have contributed to the observed difference
,t`Kv1 in nuclear cataract prevalence. However, the overall
co9 .wB@ Table 2: Age-specific prevalence of cataract types in cross sections I and II.
~ug=
{b Cataract type Age (years) Cross-section I Cross-section II
E;1Jh(58)b n % (95% CL)* n % (95% CL)*
{W]=~*w Cortical 50–54 473 4.4 (2.6–6.3) 338 7.4 (4.6–10.2)
Sp}tD<V 55–59 522 9.2 (6.7–11.7) 542 9.0 (6.6–11.5)
F0:A]`| 60–64 615 16.4 (13.5–19.4) 556 16.7 (13.6–19.8)
cOPB2\, 65–69 653 26.2 (22.8–29.6) 581 23.6 (20.1–27.0)
lKlU-4 70–74 516 31.2 (27.2–35.2) 514 35.4 (31.3–39.6)
/r-aPJX 75–79 366 40.2 (35.1–45.2) 332 39.8 (34.5–45.1)
$dA-2e10 80–84 194 58.8 (51.8–65.8) 163 42.9 (35.3–50.6)
cCa|YW^j 85–89 74 52.7 (41.1–64.4) 73 54.8 (43.1–66.5)
kI:}| _ 90+ 22 68.2 (47.0–89.3) 14 78.6 (54.0–103.2)
vq!_^F< PSC 50–54 474 2.7 (1.3–4.2) 338 2.4 (0.7–4.0)
M?[h0{
^K 55–59 522 2.9 (1.4–4.3) 541 2.6 (1.3–3.9)
Tp0bS 60–64 616 4.6 (2.9–6.2) 548 5.7 (3.7–7.6)
SF5@Vg 65–69 655 6.3 (4.4–8.1) 573 4.5 (2.8–6.3)
$2u 'N:o 70–74 517 6.8 (4.6–8.9) 505 9.7 (7.1–12.3)
A0Zt8>w 75–79 367 11.4 (8.2–14.7) 327 9.5 (6.3–12.7)
8
O 67 80–84 196 12.2 (7.6–16.9) 155 10.3 (5.5–15.2)
H6&J;yT} 85–89 74 18.9 (9.8–28.1) 69 11.6 (3.9–19.4)
\TF!S"V 90+ 23 21.7 (3.5–40.0) 11 0.0
!YP@m~ Nuclear 50–54 323 1.6 (0.2–2.9) 331 0.9 (–0.2–1.9)
L
a@
+> 55–59 386 2.3 (0.8–3.8) 507 3.6 (1.9–5.2)
V=lfl1Ev0J 60–64 453 5.3 (3.2–7.4) 501 11.6 (8.8–14.4)
r)i>06Hd 65–69 478 17.2 (13.8–20.1) 534 18.5 (15.2–21.9)
U-:ieao@ 70–74 392 27.6 (23.1–32.0) 453 36.0 (31.6–40.4)
QjC22lW- 75–79 255 45.1 (39.0–51.3) 302 55.6 (50.0–61.3)
J@OB`2?Zv 80–84 146 54.1 (45.9–62.3) 147 73.5 (66.3–80.7)
m~dC3}e8/? 85–89 50 64.0 (50.2–77.8) 70 80.0 (70.4–89.6)
(%U@3._ 90+ 18 72.2 (49.3–95.1) 15 73.3 (48.0–98.7)
06Gt&_Q n = number of persons
e#B#B * 95% Confidence Limits
qVdwfT{1J Cataract FMioguunrtea i1n ps rEeyvea lSetnucdey in cross-sections I and II of the Blue
7^M9qTEHp Cataract prevalence in cross-sections I and II of the Blue
>/#KI~}'N Mountains Eye Study.
%J8|zKT5t 0
@rHK(25+d 10
;3
F"TH
20
IJJ%$%F/ 30
u-1;'a 40
(708H_ 50
fi+R2p~vs cortical PSC nuclear any
1lsLJ4P cataract
5'Q|EIL Cataract type
KE1ao9H8wR %
.^bft P\ Cross-section I
o0ZM[0@j Cross-section II
qClHP)< BMC Ophthalmology 2006, 6:17
http://www.biomedcentral.com/1471-2415/6/17 0A:n0[V:] Page 5 of 7
QaGlR`Y (page number not for citation purposes)
OgcHS? prevalence of any cataract (including cataract surgery) was
uHIiH@S relatively stable over the 6-year period.
QW_agm Although different population-based studies used different
[Px'\nVf grading systems to assess cataract [15], the overall
%hN.ktZ/s prevalence of the three cataract types were similar across
\]9.zlB different study populations [12,16-23]. Most studies have
W-
$a
Y2 suggested that nuclear cataract is the most prevalent type
cE iu)2*e of cataract, followed by cortical cataract [16-20]. Ours and
\ j.x0/; other studies reported that cortical cataract was the most
1 ^g
t1o prevalent type [12,21-23].
=&dW(uyzY Our age-specific prevalence data show a reduction of
$^ 'aCU0C 15.9% in cortical cataract prevalence for the 80–84 year
AOp/d(vx5i age group, concordant with an increase in cataract surgery
=TP(
UJ prevalence by 9% in those aged 80+ years observed in the
O g
%U same study population [10]. Although cortical cataract is
j%V["?) thought to be the least likely cataract type leading to a cataract
GFk1/ F surgery, this may not be the case in all older persons.
.bD_R7Bi6 A relatively stable cortical cataract and PSC prevalence
-xg2q
V\c over the 6-year period is expected. We cannot offer a
>\<*4J$PZ definitive explanation for the increase in nuclear cataract
}%TSGC4{ prevalence. A possible explanation could be that a moderate
S>q>K"j^! level of nuclear cataract causes less visual disturbance
JIO$=+p than the other two types of cataract, thus for the oldest age
utlpY1#q/ groups, persons with nuclear cataract could have been less
JM.XH7k
likely to have surgery unless it is very dense or co-existing
he+#Q6 with cortical cataract or PSC. Previous studies have shown
"k$JP that functional vision and reading performance were high
<uP^-bv;( in patients undergoing cataract surgery who had nuclear
m+$ @'TbP cataract only compared to those with mixed type of cataract
_ia! mT< (nuclear and cortical) or PSC [24,25]. In addition, the
T:asm1BC[ overall prevalence of any cataract (including cataract surgery)
']ood! was similar in the two cross-sections, which appears
UFn8kBk to support our speculation that in the oldest age group,
FZpKFsPx nuclear cataract may have been less likely to be operated
[LM^),J? than the other two types of cataract. This could have
IxDWJ#k resulted in an increased nuclear cataract prevalence (due
R@T6U:1 to less being operated), compensated by the decreased
BRG|Asg( prevalence of cortical cataract and PSC (due to these being
1D([@)^ more likely to be operated), leading to stable overall prevalence
E^ h=!RW{ of any cataract.
6er(% 4! Possible selection bias arising from selective survival
T9y;OG among persons without cataract could have led to underestimation
~bA,GfSn0 of cataract prevalence in both surveys. We
#$'"cfRxc assume that such an underestimation occurred equally in
? S=W& both surveys, and thus should not have influenced our
Ln#a<Rx.E7 assessment of temporal changes.
\94j rr Measurement error could also have partially contributed
V`a+Hi<P\ to the observed difference in nuclear cataract prevalence.
17UK1Jx, Assessment of nuclear cataract from photographs is a
,qFA\cO* potentially subjective process that can be influenced by
?H;{~n? variations in photography (light exposure, focus and the
zDBD .5R; slit-lamp angle when the photograph was taken) and
ddpl Pzm# grading. Although we used the same Topcon slit-lamp
?KN:r E camera and the same two graders who graded photos
KHj6Tg;) from both surveys, we are still not able to exclude the possibility
m^Lj+=Z" of a partial influence from photographic variation
j64 4V|z on this result.
MR9/Y:Nm A similar gender difference (women having a higher rate
}N3`gCy9eN than men) in cortical cataract prevalence was observed in
]
VG?+ both surveys. Our findings are in keeping with observations
A]y*so!)> from the Beaver Dam Eye Study [18], the Barbados
z&'f/w8 Eye Study [22] and the Lens Opacities Case-Control
#Q6w+" Group [26]. It has been suggested that the difference
B\<ydN could be related to hormonal factors [18,22]. A previous
1i?=JAFfM study on biochemical factors and cataract showed that a
Yw"P)Zp lower level of iron was associated with an increased risk of
L{PH0Jf cortical cataract [27]. No interaction between sex and biochemical
m6so]xr factors were detected and no gender difference
Y1r,2 k was assessed in this study [27]. The gender difference seen
V/H@vKN2 in cortical cataract could be related to relatively low iron
@l,{x|00 levels and low hemoglobin concentration usually seen in
gX/NtO% women [28]. Diabetes is a known risk factor for cortical
k:0P+d Table 3: Gender distribution of cataract types in cross-sections I and II.
r{ "uv=,` Cataract type Gender Cross-section I Cross-section II
rt.[,m n % (95% CL)* n % (95% CL)*
9.8,q Cortical Male 1496 21.1 (19.0–23.1) 1328 20.4 (18.2–22.6)
M.k|bh8 Female 1939 25.9 (23.9–27.8) 1785 26.2 (24.2–28.3)
G2@KI- PSC Male 1500 6.5 (5.2–7.7) 1314 6.4 (5.1–7.7)
d^SE)/j Female 1944 6.2 (5.1–7.2) 1753 5.7 (4.6–6.7)
C={mi#G[/ Nuclear Male 1106 17.6 (15.4–19.9) 1225 22.5 (20.1–24.8)
h]}`@M" Female 1395 19.5 (17.4–21.6) 1635 25.0 (22.9–27.1)
%c0z)R~ n = number of persons
E4m:1=Nd~] * 95% Confidence Limits
]PVto\B= BMC Ophthalmology 2006, 6:17
http://www.biomedcentral.com/1471-2415/6/17 $'u\B Page 6 of 7
nt`<y0ta (page number not for citation purposes)
Qdm(q:w cataract but in this particular population diabetes is more
?d,M.o{0] prevalent in men than women in all age groups [29]. Differential
XW:%vJu^` exposures to cataract risk factors or different dietary
V.fp/jhj or lifestyle patterns between men and women may
4(sttd_ also be related to these observations and warrant further
$[w|oAwi study.
H
oS|f0 Conclusion
aZxO/b^j In summary, in two population-based surveys 6 years
k) 3s? apart, we have documented a relatively stable prevalence
Wa}"SqYr h of cortical cataract and PSC over the period. The observed
HYFN?~G overall increased nuclear cataract prevalence by 5% over a
$$~a=q,P[ 6-year period needs confirmation by future studies, and
x {vIT- f reasons for such an increase deserve further study.
/[L)tj7B Competing interests
ytob/tc The author(s) declare that they have no competing interests.
Ir>2sTrm Authors' contributions
mR!rn^<l AGT graded the photographs, performed literature search
#\0TxG5'QA and wrote the first draft of the manuscript. JJW graded the
Jbkt'Z(&J photographs, critically reviewed and modified the manuscript.
PgTDjEo ER performed the statistical analysis and critically
i
U,/!IQ reviewed the manuscript. PM designed and directed the
e+x*psQ study, adjudicated cataract cases and critically reviewed
cPm~`
Zd and modified the manuscript. All authors read and
b<8q 92F approved the final manuscript.
CBIT`k.+ Acknowledgements
z=[l.Af_ This study was supported by the Australian National Health & Medical
wyNC|P;j$g Research Council, Canberra, Australia (Grant Nos 974159, 991407). The
,Z?m`cx abstract was presented at the Association for Research in Vision and Ophthalmology
(A2U~j?Ry} (ARVO) meeting in Fort Lauderdale, Florida, USA, May 2005.
` -yhl3si References
OoE9W 1. Congdon N, O'Colmain B, Klaver CC, Klein R, Munoz B, Friedman
G}s;JJax DS, Kempen J, Taylor HR, Mitchell P: Causes and prevalence of
#*+;B93) visual impairment among adults in the United States. Arch
TdNsyr}JG Ophthalmol 2004, 122(4):477-485.
1x8(I&i 2. Rahmani B, Tielsch JM, Katz J, Gottsch J, Quigley H, Javitt J, Sommer
<Ak:8&$O A: The cause-specific prevalence of visual impairment in an
eS*
*L3 urban population. The Baltimore Eye Survey. Ophthalmology
W3"vTZJF 1996, 103:1721-1726.
9x4wk*z 3. Keeffe JE, Konyama K, Taylor HR: Vision impairment in the
MkkA{p Pacific region. Br J Ophthalmol 2002, 86:605-610.
i_|h{JK) 4. Reidy A, Minassian DC, Vafidis G, Joseph J, Farrow S, Wu J, Desai P,
D\ n>*x Connolly A: Prevalence of serious eye disease and visual
;g&7*1E impairment in a north London population: population based,
LH bZjZ2 cross sectional study. BMJ 1998, 316:1643-1646.
is64)2F]( 5. Resnikoff S, Pascolini D, Etya'ale D, Kocur I, Pararajasegaram R,
]aREQ?ma&z Pokharel GP, Mariotti SP: Global data on visual impairment in
q$bHO the year 2002. Bull World Health Organ 2004, 82:844-851.
)J{.Cx<E 6. Pascolini D, Mariotti SP, Pokharel GP, Pararajasegaram R, Etya'ale D,
aeLBaS Negrel AD, Resnikoff S: 2002 global update of available data on
[^h/(a` visual impairment: a compilation of population-based prevalence
6-D%)Z( studies. Ophthalmic Epidemiol 2004, 11:67-115.
hgF21Oj9 7. Rochtchina E, Mukesh BN, Wang JJ, McCarty CA, Taylor HR, Mitchell
=ltbS f7 P: Projected prevalence of age-related cataract and cataract
<{3q{VW* surgery in Australia for the years 2001 and 2021: pooled data
0=3FO}[u from two population-based surveys. Clin Experiment Ophthalmol
wa9'2a1? 2003, 31:233-236.
y.L|rRe@P 8. Medicare Benefits Schedule Statistics [
http://www.medicar 9OE_?R0c! eaustralia.gov.au/statistics/dyn_mbs/forms/mbs_tab4.shtml]
r0rJ.}! 9. Keeffe JE, Taylor HR: Cataract surgery in Australia 1985–94.
T3=-UYx] Aust N Z J Ophthalmol 1996, 24:313-317.
gvow\9{|C 10. Tan AG, Wang JJ, Rochtchina E, Jakobsen K, Mitchell P: Increase in
B iVd
ka cataract surgery prevalence from 1992–1994 to 1997–2000:
ZE5-i@1 Analysis of two population cross-sections. Clin Experiment Ophthalmol
KfJ c 2004, 32:284-288.
(:tTx>V# 11. Mitchell P, Smith W, Attebo K, Wang JJ: Prevalence of age-related
S
jC)6mo maculopathy in Australia. The Blue Mountains Eye Study.
V\e13cL] Ophthalmology 1995, 102:1450-1460.
<z~2
d 12. Mitchell P, Cumming RG, Attebo K, Panchapakesan J: Prevalence of
O c^6u cataract in Australia: the Blue Mountains eye study. Ophthalmology
8u7K$Q 1997, 104:581-588.
v@}1WGY 13. Klein BEK, Magli YL, Neider MW, Klein R: Wisconsin system for classification
S)Ub/`f{s of cataracts from photographs (protocol) Madison, WI; 1990.
Kt/+PS 14. Foran S, Wang JJ, Mitchell P: Causes of visual impairment in two
3Vb=6-| older population cross-sections: the Blue Mountains Eye
USHlb#* Study. Ophthalmic Epidemiol 2003, 10:215-225.
Q]2sj: 15. Congdon N, Vingerling JR, Klein BE, West S, Friedman DS, Kempen J,
&deZ O'Colmain B, Wu SY, Taylor HR: Prevalence of cataract and
P!>{>r4 pseudophakia/aphakia among adults in the United States.
U_N5~#9 Arch Ophthalmol 2004, 122:487-494.
JsWq._O{/ 16. Sperduto RD, Hiller R: The prevalence of nuclear, cortical, and
GDNh?R posterior subcapsular lens opacities in a general population
8VAYIxRv sample. Ophthalmology 1984, 91:815-818.
5;sQ@ 17. Adamsons I, Munoz B, Enger C, Taylor HR: Prevalence of lens
e$FAhwpo
n opacities in surgical and general populations. Arch Ophthalmol
^J*G%*
1991, 109:993-997.
ib""Fv7{ 18. Klein BE, Klein R, Linton KL: Prevalence of age-related lens
p'uqh
e X opacities in a population. The Beaver Dam Eye Study. Ophthalmology
+UpMMh q 1992, 99:546-552.
>TQBRA;' 19. West SK, Munoz B, Schein OD, Duncan DD, Rubin GS: Racial differences
yjM@/b in lens opacities: the Salisbury Eye Evaluation (SEE)
^!v} project. Am J Epidemiol 1998, 148:1033-1039.
a|6x!p2X 20. Congdon N, West SK, Buhrmann RR, Kouzis A, Munoz B, Mkocha H:
zvK5Zxl Prevalence of the different types of age-related cataract in
|)72E[lL an African population. Invest Ophthalmol Vis Sci 2001,
KWn1 %oGJ 42:2478-2482.
_:fO)gs|1 21. Livingston PM, Guest CS, Stanislavsky Y, Lee S, Bayley S, Walker C,
GJ^]ER-K McKean C, Taylor HR: A population-based estimate of cataract
9,EaN{GM prevalence: the Melbourne Visual Impairment Project experience.
L->f=
8L Dev Ophthalmol 1994, 26:1-6.
dbq{a 22. Leske MC, Connell AM, Wu SY, Hyman L, Schachat A: Prevalence
]zwqG A of lens opacities in the Barbados Eye Study. Arch Ophthalmol
wMPw/a; 1997, 115:105-111. published erratum appears in Arch Ophthalmol
mZ0oa-Iy 1997 Jul;115(7):931
mJDKxgGK 23. Seah SK, Wong TY, Foster PJ, Ng TP, Johnson GJ: Prevalence of
BtNW5'^ lens opacity in Chinese residents of Singapore: the tanjong
]Re~V{uh pagar survey. Ophthalmology 2002, 109:2058-2064.
mP$G
9R 24. Stifter E, Sacu S, Weghaupt H, Konig F, Richter-Muksch S, Thaler A,
V.gY1
Velikay-Parel M, Radner W: Reading performance depending on
P
VkN3J the type of cataract and its predictability on the visual outcome.
64\5v?C J Cataract Refract Surg 2004, 30:1259-1267.
`j!2uRFe> 25. Stifter E, Sacu S, Weghaupt H: Functional vision with cataracts of
`2(R}zUHN different morphologies: comparative study. J Cataract Refract
Va
|9)m Surg 2004, 30:1883-1891.
ZV q 26. Leske MC, Chylack LT Jr, Wu SY: The Lens Opacities Case-Control
_9-D3_P[3 Study. Risk factors for cataract. Arch Ophthalmol 1991,
,8"[ /@ 109:244-251.
c>i*HN}Z| 27. Leske MC, Wu SY, Hyman L, Sperduto R, Underwood B, Chylack LT,
^B!?;\4IM Milton RC, Srivastava S, Ansari N: Biochemical factors in the lens
u g:G9vjQ opacities. Case-control study. The Lens Opacities Case-Control
j.'"CU Study Group. Arch Ophthalmol 1995, 113:1113-1119.
=Wy`X0h 28. Yip R, Johnson C, Dallman PR: Age-related changes in laboratory
F/od,w9_ values used in the diagnosis of anemia and iron deficiency.
-^jLU
FC Am J Clin Nutr 1984, 39:427-436.
hHl-;%# 29. Mitchell P, Smith W, Wang JJ, Cumming RG, Leeder SR, Burnett L:
CygV_q Diabetes in an older Australian population. Diabetes Res Clin
x^O2Lj,w\ Pract 1998, 41:177-184.
~B*\k^t` Pre-publication history
;{q) |GRF The pre-publication history for this paper can be accessed
X>GY*XU here:
AUjTcu>i Publish with BioMed Central and every
Y7V&zF{ scientist can read your work free of charge
%V1T!< "BioMed Central will be the most significant development for
8(/f!~ disseminating the results of biomedical research in our lifetime."
OZ14-}Lr5 Sir Paul Nurse, Cancer Research UK
yqb<<4I Your research papers will be:
zu*G4?]~h available free of charge to the entire biomedical community
6N+)LF}P b peer reviewed and published immediately upon acceptance
g#%FY1xp cited in PubMed and archived on PubMed Central
r\ Yur yours — you keep the copyright
dlzamoS@AR Submit your manuscript here:
/N{@g.edL http://www.biomedcentral.com/info/publishing_adv.asp Cl.T'A$ BioMedcentral
A}Dpw[Q2@8 BMC Ophthalmology 2006, 6:17
http://www.biomedcentral.com/1471-2415/6/17 EM
w(%}8w Page 7 of 7
5"~^;O (page number not for citation purposes)
]bE?n.NwZ http://www.biomedcentral.com/1471-2415/6/17/prepub