BioMed Central
~E2
KZm Page 1 of 7
',JinE95 (page number not for citation purposes)
] Zy5%gI BMC Ophthalmology
KUlp"{a`,K Research article Open Access
w"Gm;
B4 Comparison of age-specific cataract prevalence in two
8c9*\S population-based surveys 6 years apart
-"'j7t: Ava Grace Tan†, Jie Jin Wang*†, Elena Rochtchina† and Paul Mitchell†
I
8`VNA&b Address: Centre for Vision Research, Westmead Millennium Institute, Department of Ophthalmology, University of Sydney, Westmead Hospital,
3q\,$*D. Westmead, NSW, Australia
^:^9l1] Email: Ava Grace Tan -
ava_tan@wmi.usyd.edu.au; Jie Jin Wang* -
jiejin_wang@wmi.usyd.edu.au;
iTgt}]L Elena Rochtchina -
elena_rochtchina@wmi.usyd.edu.au; Paul Mitchell -
paul_mitchell@wmi.usyd.edu.au aBNc(?ri * Corresponding author †Equal contributors
Q ayPo]O Abstract
_E@2ZnD2 Background: In this study, we aimed to compare age-specific cortical, nuclear and posterior
f!Y?S subcapsular (PSC) cataract prevalence in two surveys 6 years apart.
Yg%I? Methods: The Blue Mountains Eye Study examined 3654 participants (82.4% of those eligible) in
r*2+xDoEi cross-section I (1992–4) and 3509 participants (75.1% of survivors and 85.2% of newly eligible) in
f
e\$@- cross-section II (1997–2000, 66.5% overlap with cross-section I). Cataract was assessed from lens
"O3tq=Q photographs following the Wisconsin Cataract Grading System. Cortical cataract was defined if
nP$Ky1y G cortical opacity comprised ≥ 5% of lens area. Nuclear cataract was defined if nuclear opacity ≥
qouhuH_WtJ Wisconsin standard 4. PSC was defined if any present. Any cataract was defined to include persons
&^ 1$^= who had previous cataract surgery. Weighted kappa for inter-grader reliability was 0.82, 0.55 and
!Xf5e*1IS 0.82 for cortical, nuclear and PSC cataract, respectively. We assessed age-specific prevalence using
H1|?t+oP an interval of 5 years, so that participants within each age group were independent between the
_.tVSVp two surveys.
}~e8e Results: Age and gender distributions were similar between the two populations. The age-specific
]!?;@$wx prevalence of cortical (23.8% in 1st, 23.7% in 2nd) and PSC cataract (6.3%, 6.0%) was similar. The
<wN}X#M prevalence of nuclear cataract increased slightly from 18.7% to 23.9%. After age standardization,
:~"CuB/ the similar prevalence of cortical (23.8%, 23.5%) and PSC cataract (6.3%, 5.9%), and the increased
`i3NG1
v0 prevalence of nuclear cataract (18.7%, 24.2%) remained.
P+@/O Conclusion: In two surveys of two population-based samples with similar age and gender
n{n52][J] distributions, we found a relatively stable cortical and PSC cataract prevalence over a 6-year period.
_hAcJ{Y The increased prevalence of nuclear cataract deserves further study.
3`t#UY).F Background
hZ?Rof Age-related cataract is the leading cause of reversible visual
o[Q MT P impairment in older persons [1-6]. In Australia, it is
Y2N>HK0 estimated that by the year 2021, the number of people
H%qsjB^ affected by cataract will increase by 63%, due to population
>*~L28Fyn aging [7]. Surgical intervention is an effective treatment
sEp"D+f for cataract and normal vision (> 20/40) can usually
`06;
be restored with intraocular lens (IOL) implantation.
K
-nF lPm\ Cataract surgery with IOL implantation is currently the
Z3"%`*Tmq- most commonly performed, and is, arguably, the most
fiK6@, cost effective surgical procedure worldwide. Performance
n,vct<&z@ Published: 20 April 2006
Qf~vZtJ+J BMC Ophthalmology 2006, 6:17 doi:10.1186/1471-2415-6-17
sXLq*b? Received: 14 December 2005
bkOv2tZ Accepted: 20 April 2006
-]0OKE& This article is available from:
http://www.biomedcentral.com/1471-2415/6/17 F+YZE[h% © 2006 Tan et al; licensee BioMed Central Ltd.
?&8^&brwG This is an Open Access article distributed under the terms of the Creative Commons Attribution License (
http://creativecommons.org/licenses/by/2.0),
e>} s;H, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
l5S aT,% BMC Ophthalmology 2006, 6:17
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QyEnpZ8?a (page number not for citation purposes)
z Xg3[orF of this surgical procedure has been continuously increasing
zU5v /'h>d in the last two decades. Data from the Australian
R5N%e%[ Health Insurance Commission has shown a steady
Lu?C-
$a C increase in Medicare claims for cataract surgery [8]. A 2.6-
k0OYJ/ fold increase in the total number of cataract procedures
-$pzl,^ h from 1985 to 1994 has been documented in Australia [9].
;,hwZZA The rate of cataract surgery per thousand persons aged 65
!EvAB+`jLI years or older has doubled in the last 20 years [8,9]. In the
XQY#716) Blue Mountains Eye Study population, we observed a onethird
\o z#l'z increase in cataract surgery prevalence over a mean
TJ10s%,V 6-year interval, from 6% to nearly 8% in two cross-sectional
I,E?h?6Y population-based samples with a similar age range
Tr_
w]' [10]. Further increases in cataract surgery performance
y*4=c_Z
would be expected as a result of improved surgical skills
GSoX<*i and technique, together with extending cataract surgical
GA$V0YQX benefits to a greater number of older people and an
W,K;6TZhh increased number of persons with surgery performed on
_zR+i]9 both eyes.
(of#(I[m7 Both the prevalence and incidence of age-related cataract
!44/sr' link directly to the demand for, and the outcome of, cataract
Lm iOhx surgery and eye health care provision. This report
Xe3U`P7( aimed to assess temporal changes in the prevalence of cortical
{0L1X6eg and nuclear cataract and posterior subcapsular cataract
T.])diuvj- (PSC) in two cross-sectional population-based
`fA@hK
surveys 6 years apart.
d?y4GkK Methods
jte.Xy~g The Blue Mountains Eye Study (BMES) is a populationbased
q;B4WL} cohort study of common eye diseases and other
?j'7l=94A health outcomes. The study involved eligible permanent
oK9( /v residents aged 49 years and older, living in two postcode
S4Pxc
]! areas in the Blue Mountains, west of Sydney, Australia.
EGGWrl}1 Participants were identified through a census and were
GF"hx`zyJ invited to participate. The study was approved at each
P9/q|>F stage of the data collection by the Human Ethics Committees
kI,yU}<Fq of the University of Sydney and the Western Sydney
r7RIRg_ Area Health Service and adhered to the recommendations
0%3
2=k7O[ of the Declaration of Helsinki. Written informed consent
s,"]aew was obtained from each participant.
mu\6z_e Details of the methods used in this study have been
7!evm;A described previously [11]. The baseline examinations
ADz ^\ (BMES cross-section I) were conducted during 1992–
Ja|5 @ 1994 and included 3654 (82.4%) of 4433 eligible residents.
\Q {m9fE Follow-up examinations (BMES IIA) were conducted
I
)~GZ during 1997–1999, with 2335 (75.0% of BMES
P:hBt\5B cross section I survivors) participating. A repeat census of
6gkV*|U,e the same area was performed in 1999 and identified 1378
1Rt33\1J0 newly eligible residents who moved into the area or the
48J@CvU eligible age group. During 1999–2000, 1174 (85.2%) of
'<gI8W</ this group participated in an extension study (BMES IIB).
g!|=%(G= BMES cross-section II thus includes BMES IIA (66.5%)
<3oWEm and BMES IIB (33.5%) participants (n = 3509).
el&
0}`K Similar procedures were used for all stages of data collection
Z< 1 at both surveys. A questionnaire was administered
S~<$Hy*kh including demographic, family and medical history. A
99]R$eT8 detailed eye examination included subjective refraction,
kF3k7,.8& slit-lamp (Topcon SL-7e camera, Topcon Optical Co,
'Y?"{HZ Tokyo, Japan) and retroillumination (Neitz CT-R camera,
1]d!~ Neitz Instrument Co, Tokyo, Japan) photography of the
&U{#Kt5q lens. Grading of lens photographs in the BMES has been
@hl.lq previously described [12]. Briefly, masked grading was
ajve~8
/& performed on the lens photographs using the Wisconsin
32(^Te]: Cataract Grading System [13]. Cortical cataract and PSC
]v?@g:iE were assessed from the retroillumination photographs by
Z/G
ev"p estimating the percentage of the circular grid involved.
t
Cw<Ip Cortical cataract was defined when cortical opacity
52Yq involved at least 5% of the total lens area. PSC was defined
+<'Ev~ when opacity comprised at least 1% of the total lens area.
"N;`1ce Slit-lamp photographs were used to assess nuclear cataract
B[qzUD*P_n using the Wisconsin standard set of four lens photographs
!d'GE`w T [13]. Nuclear cataract was defined when nuclear opacity
f<GhkDPm>? was at least as great as the standard 4 photograph. Any cataract
[]D&bYpv was defined to include persons who had previous
UJ%R
cataract surgery as well as those with any of three cataract
pD(j'[ types. Inter-grader reliability was high, with weighted
5b5x!do kappa 0.82 for cortical cataract, 0.55 (simple kappa 0.75)
L]yS[UN$ for nuclear cataract and 0.82 for PSC grading. The intragrader
1v#%Ei$6`t reliability for nuclear cataract was assessed with
Cwr~HY simple kappa 0.83 for the senior grader who graded
5CuuG<0 nuclear cataract at both surveys. All PSC cases were confirmed
a,Sw4yJ!Q by an ophthalmologist (PM).
y+Ra4G#/} In cross-section I, 219 persons (6.0%) had missing or
}pDqe;a{ ungradable Neitz photographs, leaving 3435 with photographs
8."]//V available for cortical cataract and PSC assessment,
a@8v^G while 1153 (31.6%) had randomly missing or ungradable
v/@^Q1G/: Topcon photographs due to a camera malfunction, leaving
"33Fv9C#bK 2501 with photographs available for nuclear cataract
%) /s; Q, assessment. Comparison of characteristics between participants
[v7F1@6b with and without Neitz or Topcon photographs in
Q_1:tW
& cross-section I showed no statistically significant differences
'SO %)B between the two groups, as reported previously
&\#sI9 [12]. In cross-section II, 441 persons (12.5%) had missing
@X%C>iYa9 or ungradable Neitz photographs, leaving 3068 for cortical
j_/>A=OD cataract and PSC assessment, and 648 (18.5%) had
-^K"Z
P1 missing or ungradable Topcon photographs, leaving 2860
z-BXd for nuclear cataract assessment.
9"NF/)_ Data analysis was performed using the Statistical Analysis
%fc!2E9| System (SAS, SAS Institute, Cary, NC, USA). Age-adjusted
8G9s<N}5&u prevalence was calculated using direct standardization of
Bz^jw>1b the cross-section II population to the cross-section I population.
67VL@ ] We assessed age-specific prevalence using an
h mvfw:Nq4 interval of 5 years, so that participants within each age
&[_g6OL group were independent between the two cross-sectional
G"klu surveys.
y.anl BMC Ophthalmology 2006, 6:17
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hM@
H A Results
:Uz| 3gq Characteristics of the two survey populations have been
|^0XYBxQ previously compared [14] and showed that age and sex
ccB&O _ distributions were similar. Table 1 compares participant
+GG9^:<yr characteristics between the two cross-sections. Cross-section
Y}x>t* I II participants generally had higher rates of diabetes,
46$._h
P hypertension, myopia and more users of inhaled steroids.
2!0c4a^z Cataract prevalence rates in cross-sections I and II are
yaD~1"GA'O shown in Figure 1. The overall prevalence of cortical cataract
<_h~w} was 23.8% and 23.7% in cross-sections I and II,
:imW\@u respectively (age-sex adjusted P = 0.81). Corresponding
)n+Lo&C< prevalence of PSC was 6.3% and 6.0% for the two crosssections
s2teym,uG (age-sex adjusted P = 0.60). There was an
hq%?=2'9? increased prevalence of nuclear cataract, from 18.7% in
uH/J]zKR cross-section I to 23.9% in cross-section II over the 6-year
%kv0Wefs period (age-sex adjusted P < 0.001). Prevalence of any cataract
Qr1 "Tk7s (including persons who had cataract surgery), however,
Cf TfL3(J was relatively stable (46.9% and 46.8% in crosssections
ADS9DiX/ I and II, respectively).
M}d_I+ After age-standardization, these prevalence rates remained
AB=daie stable for cortical cataract (23.8% and 23.5% in the two
A$<.a'&T! surveys) and PSC (6.3% and 5.9%). The slightly increased
X59:C3c prevalence of nuclear cataract (from 18.7% to 24.2%) was
Q7*SE%H not altered.
qo p^;~ Table 2 shows the age-specific prevalence rates for cortical
&7<TAo;O cataract, PSC and nuclear cataract in cross-sections I and
RLw;(*(g II. A similar trend of increasing cataract prevalence with
{ WIJC',Y increasing age was evident for all three types of cataract in
}B8IBveu both surveys. Comparing the age-specific prevalence
YwteZSbp6M between the two surveys, a reduction in PSC prevalence in
1HXjN~XF cross-section II was observed in the older age groups (≥ 75
oz AS[B6 years). In contrast, increased nuclear cataract prevalence
8WtsKOno in cross-section II was observed in the older age groups (≥
@HQ`~C#Z' 70 years). Age-specific cortical cataract prevalence was relatively
{kp"nl$< consistent between the two surveys, except for a
pi /g H reduction in prevalence observed in the 80–84 age group
Nd`%5%':: and an increasing prevalence in the older age groups (≥ 85
}'""(,2 years).
D&/kCi= R Similar gender differences in cataract prevalence were
t0o`-d( observed in both surveys (Table 3). Higher prevalence of
.l>77zM6 cortical and nuclear cataract in women than men was evident
X*M#FT- but the difference was only significant for cortical
}E0,z cataract (age-adjusted odds ratio, OR, for women 1.3,
*FC=X) _&W 95% confidence intervals, CI, 1.1–1.5 in cross-section I
PK;*u,V and OR 1.4, 95% CI 1.1–1.6 in cross-section II). In con-
Anscr Table 1: Participant characteristics.
K
AC6Snu1 Characteristics Cross-section I Cross-section II
<Fi%iA n % n %
vI2^tX9 Age (mean) (66.2) (66.7)
$>GgB`
50–54 485 13.3 350 10.0
_9Jh
L:cY 55–59 534 14.6 580 16.5
6I1,:nLL< 60–64 638 17.5 600 17.1
(5R?#vj 65–69 671 18.4 639 18.2
7[I}*3Q' 70–74 538 14.7 572 16.3
X}tVmO? 75–79 422 11.6 407 11.6
$UgA0]qn 80–84 230 6.3 226 6.4
3D`YZ#M 85–89 100 2.7 110 3.1
Q,p}:e 90+ 36 1.0 24 0.7
Kz>3
ic$I
Female 2072 56.7 1998 57.0
?*E'^~,H) Ever Smokers 1784 51.2 1789 51.2
<1FC%f/ Use of inhaled steroids 370 10.94 478 13.8^
&GlwC%$S History of:
'@p['#\uI Diabetes 284 7.8 347 9.9^
o>/YAX:.!T Hypertension 1669 46.0 1825 52.2^
/x5rf Emmetropia* 1558 42.9 1478 42.2
#gp,V#T Myopia* 442 12.2 495 14.1^
*8#i$w11M Hyperopia* 1633 45.0 1532 43.7
p$h4u_ n = number of persons affected
{.QEc0- * best spherical equivalent refraction correction
.Jt[(; ^ P < 0.01
lD"(MQV@0 BMC Ophthalmology 2006, 6:17
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TYJ:! (page number not for citation purposes)
T{Sb^-H#X t
`0P$
#5? rast, men had slightly higher PSC prevalence than women
kMtwiB|7j in both cross-sections but the difference was not significant
2_zp:v (OR 1.1, 95% CI 0.8–1.4 for men in cross-section I
Xb{
[c+. and OR 1.2, 95% 0.9–1.6 in cross-section II).
|P -8HlOr Discussion
VJdIHsI Findings from two surveys of BMES cross-sectional populations
jFA{+Yr1 with similar age and gender distribution showed
^@qvl%j that the prevalence of cortical cataract and PSC remained
\|E^v6E%0 stable, while the prevalence of nuclear cataract appeared
-PS#Z0> to have increased. Comparison of age-specific prevalence,
G8r``{C! with totally independent samples within each age group,
n@
U n confirmed the robustness of our findings from the two
:{IO=^D=$ survey samples. Although lens photographs taken from
HYD"#m'TkB the two surveys were graded for nuclear cataract by the
R
}lsnX< same graders, who documented a high inter- and intragrader
NGOqy+Ty{f reliability, we cannot exclude the possibility that
|!"2fI variations in photography, performed by different photographers,
q|8{@EMT may have contributed to the observed difference
iVd.f
A in nuclear cataract prevalence. However, the overall
df
n9!h Table 2: Age-specific prevalence of cataract types in cross sections I and II.
0#ClWynjRO Cataract type Age (years) Cross-section I Cross-section II
x\J#]d. n % (95% CL)* n % (95% CL)*
Hd,
p!_ Cortical 50–54 473 4.4 (2.6–6.3) 338 7.4 (4.6–10.2)
Db6om7N 55–59 522 9.2 (6.7–11.7) 542 9.0 (6.6–11.5)
'A:x/iv}^ 60–64 615 16.4 (13.5–19.4) 556 16.7 (13.6–19.8)
`;>= '"O!\ 65–69 653 26.2 (22.8–29.6) 581 23.6 (20.1–27.0)
DSt]{fl`P 70–74 516 31.2 (27.2–35.2) 514 35.4 (31.3–39.6)
tUgEeh6 75–79 366 40.2 (35.1–45.2) 332 39.8 (34.5–45.1)
NMww>80 80–84 194 58.8 (51.8–65.8) 163 42.9 (35.3–50.6)
~M\I;8ne 85–89 74 52.7 (41.1–64.4) 73 54.8 (43.1–66.5)
v@wb"jdFi$ 90+ 22 68.2 (47.0–89.3) 14 78.6 (54.0–103.2)
7^Ns&Q PSC 50–54 474 2.7 (1.3–4.2) 338 2.4 (0.7–4.0)
?c7*_<W
5 55–59 522 2.9 (1.4–4.3) 541 2.6 (1.3–3.9)
KyzFnVH3) 60–64 616 4.6 (2.9–6.2) 548 5.7 (3.7–7.6)
?}m']4p 65–69 655 6.3 (4.4–8.1) 573 4.5 (2.8–6.3)
jq+A-T}@ 70–74 517 6.8 (4.6–8.9) 505 9.7 (7.1–12.3)
dlG=Vq&Y 75–79 367 11.4 (8.2–14.7) 327 9.5 (6.3–12.7)
jiYmb8Q4D 80–84 196 12.2 (7.6–16.9) 155 10.3 (5.5–15.2)
!>>f(t4 85–89 74 18.9 (9.8–28.1) 69 11.6 (3.9–19.4)
;\[(- )f!= 90+ 23 21.7 (3.5–40.0) 11 0.0
1c;6xc,ub Nuclear 50–54 323 1.6 (0.2–2.9) 331 0.9 (–0.2–1.9)
&[At`Nw71 55–59 386 2.3 (0.8–3.8) 507 3.6 (1.9–5.2)
YSj+\Z$(
60–64 453 5.3 (3.2–7.4) 501 11.6 (8.8–14.4)
-CRQp1] 65–69 478 17.2 (13.8–20.1) 534 18.5 (15.2–21.9)
Y;)dct 70–74 392 27.6 (23.1–32.0) 453 36.0 (31.6–40.4)
ixV0|P8,c 75–79 255 45.1 (39.0–51.3) 302 55.6 (50.0–61.3)
}=|!:k
iE 80–84 146 54.1 (45.9–62.3) 147 73.5 (66.3–80.7)
!H2QjW 85–89 50 64.0 (50.2–77.8) 70 80.0 (70.4–89.6)
uio@r^Xz 90+ 18 72.2 (49.3–95.1) 15 73.3 (48.0–98.7)
:Dd$i_3= n = number of persons
(%U@3._ * 95% Confidence Limits
Z(9u< Cataract FMioguunrtea i1n ps rEeyvea lSetnucdey in cross-sections I and II of the Blue
!o>H1#2l Cataract prevalence in cross-sections I and II of the Blue
rvyrxw%[ Mountains Eye Study.
e{KByFl 0
F
{B\kq8 10
7#~+@'Oe 20
3 ( ]M{4j 30
p2N:;lXM 40
Cn_$l> 50
wP57Pf0 cortical PSC nuclear any
Hk7q{`:N cataract
5P .qXA"D Cataract type
*-12VIG'H %
iL=
m{ Cross-section I
@m?QR(LJ Cross-section II
'<R>E:5 BMC Ophthalmology 2006, 6:17
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ms_ VM>l (page number not for citation purposes)
HK)cKzG[s! prevalence of any cataract (including cataract surgery) was
O'GG Ti]e relatively stable over the 6-year period.
KvQ,;A Although different population-based studies used different
-AYA~O(& grading systems to assess cataract [15], the overall
XM<KF&pVB prevalence of the three cataract types were similar across
ez3Z3t` different study populations [12,16-23]. Most studies have
kGkA:g: suggested that nuclear cataract is the most prevalent type
l/
y]nw of cataract, followed by cortical cataract [16-20]. Ours and
iU+nqY' other studies reported that cortical cataract was the most
~dHM4lGY prevalent type [12,21-23].
WS2osBc Our age-specific prevalence data show a reduction of
q@hp.(V 15.9% in cortical cataract prevalence for the 80–84 year
39 Y(!q age group, concordant with an increase in cataract surgery
z
NSu prevalence by 9% in those aged 80+ years observed in the
<As9>5|% same study population [10]. Although cortical cataract is
'<iK*[NW thought to be the least likely cataract type leading to a cataract
/?/#B ` surgery, this may not be the case in all older persons.
+KEkmXZ A relatively stable cortical cataract and PSC prevalence
k#}g,0@ over the 6-year period is expected. We cannot offer a
@^ ik[9^H definitive explanation for the increase in nuclear cataract
~^)^q
8 prevalence. A possible explanation could be that a moderate
jy2IZ o level of nuclear cataract causes less visual disturbance
+~nzii3 than the other two types of cataract, thus for the oldest age
Xj+q~4{|vt groups, persons with nuclear cataract could have been less
02AI%OOH likely to have surgery unless it is very dense or co-existing
3}1ssU"T with cortical cataract or PSC. Previous studies have shown
s|bM%!$1 that functional vision and reading performance were high
EA<}[4#jS in patients undergoing cataract surgery who had nuclear
!.5),2 cataract only compared to those with mixed type of cataract
7@%'wy&A (nuclear and cortical) or PSC [24,25]. In addition, the
IO.<q,pP!_ overall prevalence of any cataract (including cataract surgery)
! o,5h|\ was similar in the two cross-sections, which appears
S\NL+V?7h to support our speculation that in the oldest age group,
~:sE:9$z nuclear cataract may have been less likely to be operated
;/AG@$) than the other two types of cataract. This could have
J?:[$ C5 resulted in an increased nuclear cataract prevalence (due
YJ7V`Np to less being operated), compensated by the decreased
|I[7,`C~ prevalence of cortical cataract and PSC (due to these being
pF=g||gS more likely to be operated), leading to stable overall prevalence
7_KhV of any cataract.
:
//U^sFL Possible selection bias arising from selective survival
{GqXP0' among persons without cataract could have led to underestimation
t]_S of cataract prevalence in both surveys. We
K3$`
Kv>I assume that such an underestimation occurred equally in
J>S3sP both surveys, and thus should not have influenced our
2C+(":=} assessment of temporal changes.
$. e) Measurement error could also have partially contributed
~0tdfK0c to the observed difference in nuclear cataract prevalence.
8LM#WIm? Assessment of nuclear cataract from photographs is a
(
76{2 potentially subjective process that can be influenced by
j^u[F" variations in photography (light exposure, focus and the
&
&RA4 slit-lamp angle when the photograph was taken) and
ij)Cm]4(2 grading. Although we used the same Topcon slit-lamp
nTnRGf\T camera and the same two graders who graded photos
s^|\9%WD from both surveys, we are still not able to exclude the possibility
KjR4=9MD of a partial influence from photographic variation
,a(O`##Bn on this result.
m3
IP7h' A similar gender difference (women having a higher rate
eO4)|tW than men) in cortical cataract prevalence was observed in
j]> uZalr both surveys. Our findings are in keeping with observations
F,Fo}YQX from the Beaver Dam Eye Study [18], the Barbados
:k"rhI Eye Study [22] and the Lens Opacities Case-Control
1i?=JAFfM Group [26]. It has been suggested that the difference
7!d$M{0" could be related to hormonal factors [18,22]. A previous
X=_Z(;<& study on biochemical factors and cataract showed that a
X5E
'*W lower level of iron was associated with an increased risk of
Zq?_dIX
% cortical cataract [27]. No interaction between sex and biochemical
X ]s"5ju|t factors were detected and no gender difference
nP_=GI was assessed in this study [27]. The gender difference seen
kEAhTh&g* in cortical cataract could be related to relatively low iron
%h* 5xB]Tt levels and low hemoglobin concentration usually seen in
0BC`iql5 women [28]. Diabetes is a known risk factor for cortical
Ow3a0cF[9 Table 3: Gender distribution of cataract types in cross-sections I and II.
kMS5h~D[ Cataract type Gender Cross-section I Cross-section II
ONWO`XD n % (95% CL)* n % (95% CL)*
8t``NZ[ Cortical Male 1496 21.1 (19.0–23.1) 1328 20.4 (18.2–22.6)
YC)hX'A\ Female 1939 25.9 (23.9–27.8) 1785 26.2 (24.2–28.3)
R~c1)[[E PSC Male 1500 6.5 (5.2–7.7) 1314 6.4 (5.1–7.7)
#:W%,$9\P Female 1944 6.2 (5.1–7.2) 1753 5.7 (4.6–6.7)
B! `\L! Nuclear Male 1106 17.6 (15.4–19.9) 1225 22.5 (20.1–24.8)
:0dfB&7 Female 1395 19.5 (17.4–21.6) 1635 25.0 (22.9–27.1)
{y/-:=S)A n = number of persons
%gTVW!q * 95% Confidence Limits
51/sTx<Z} BMC Ophthalmology 2006, 6:17
http://www.biomedcentral.com/1471-2415/6/17 _S<?t9mS Page 6 of 7
\*9Ua/H (page number not for citation purposes)
7kM4Ei cataract but in this particular population diabetes is more
y*|L:! prevalent in men than women in all age groups [29]. Differential
&G=0 exposures to cataract risk factors or different dietary
W^|J/Y48 or lifestyle patterns between men and women may
4g'}h`kh
also be related to these observations and warrant further
LH.%\TMN$ study.
.' IeHh Conclusion
6'vi68 In summary, in two population-based surveys 6 years
QB9A-U<J apart, we have documented a relatively stable prevalence
|P~q/Wff of cortical cataract and PSC over the period. The observed
EFv4=OWB overall increased nuclear cataract prevalence by 5% over a
N=<=dp( 6-year period needs confirmation by future studies, and
5"e+& zU~f reasons for such an increase deserve further study.
QP<FCmt8 Competing interests
1::LN(`< The author(s) declare that they have no competing interests.
~RCg.&[ou Authors' contributions
7>KQRLw AGT graded the photographs, performed literature search
+|M{I= 8 and wrote the first draft of the manuscript. JJW graded the
$BaK'7=3* photographs, critically reviewed and modified the manuscript.
m/KjJ"s, ER performed the statistical analysis and critically
fxOE]d8v reviewed the manuscript. PM designed and directed the
\E~Q1eAJT study, adjudicated cataract cases and critically reviewed
`TkbF9N+ and modified the manuscript. All authors read and
p^Agh
approved the final manuscript.
M!-q}5' ; Acknowledgements
m.Twgin This study was supported by the Australian National Health & Medical
4xp j< Research Council, Canberra, Australia (Grant Nos 974159, 991407). The
H[Cj7{V abstract was presented at the Association for Research in Vision and Ophthalmology
nc
-Qz (ARVO) meeting in Fort Lauderdale, Florida, USA, May 2005.
{dDq*s
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