BioMed Central
>0I\w$L Page 1 of 7
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w (page number not for citation purposes)
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cJ BMC Ophthalmology
N@R?<a Research article Open Access
|. LE` Comparison of age-specific cataract prevalence in two
z&Lcl{<MA population-based surveys 6 years apart
#)( D_* Ava Grace Tan†, Jie Jin Wang*†, Elena Rochtchina† and Paul Mitchell†
iTJE:[W"y Address: Centre for Vision Research, Westmead Millennium Institute, Department of Ophthalmology, University of Sydney, Westmead Hospital,
_yc&'Wq Westmead, NSW, Australia
A(wuRXnVWK Email: Ava Grace Tan -
ava_tan@wmi.usyd.edu.au; Jie Jin Wang* -
jiejin_wang@wmi.usyd.edu.au;
DQ= /Jr~ Elena Rochtchina -
elena_rochtchina@wmi.usyd.edu.au; Paul Mitchell -
paul_mitchell@wmi.usyd.edu.au u-HBmL * Corresponding author †Equal contributors
w~WW2w Abstract
r*t\F&D Background: In this study, we aimed to compare age-specific cortical, nuclear and posterior
'<&rMn subcapsular (PSC) cataract prevalence in two surveys 6 years apart.
qp2&Z8S\D Methods: The Blue Mountains Eye Study examined 3654 participants (82.4% of those eligible) in
O
718s\# cross-section I (1992–4) and 3509 participants (75.1% of survivors and 85.2% of newly eligible) in
FuFA/R=x/ cross-section II (1997–2000, 66.5% overlap with cross-section I). Cataract was assessed from lens
3/4r\%1b+ photographs following the Wisconsin Cataract Grading System. Cortical cataract was defined if
OLyl.#J cortical opacity comprised ≥ 5% of lens area. Nuclear cataract was defined if nuclear opacity ≥
Ogp@! Wisconsin standard 4. PSC was defined if any present. Any cataract was defined to include persons
1ika' who had previous cataract surgery. Weighted kappa for inter-grader reliability was 0.82, 0.55 and
!Bn,f
2 0.82 for cortical, nuclear and PSC cataract, respectively. We assessed age-specific prevalence using
gtRs|| an interval of 5 years, so that participants within each age group were independent between the
]xN)>A2 two surveys.
U t.#h=" Results: Age and gender distributions were similar between the two populations. The age-specific
.@3bz
prevalence of cortical (23.8% in 1st, 23.7% in 2nd) and PSC cataract (6.3%, 6.0%) was similar. The
Oq*=oz^~1 prevalence of nuclear cataract increased slightly from 18.7% to 23.9%. After age standardization,
3}2a3) the similar prevalence of cortical (23.8%, 23.5%) and PSC cataract (6.3%, 5.9%), and the increased
]%I|C++0 prevalence of nuclear cataract (18.7%, 24.2%) remained.
CL<m+dW%* Conclusion: In two surveys of two population-based samples with similar age and gender
TV*@h2C"i distributions, we found a relatively stable cortical and PSC cataract prevalence over a 6-year period.
28
7)\FU;3 The increased prevalence of nuclear cataract deserves further study.
uui3jZ: Background
)G@/E^ySM Age-related cataract is the leading cause of reversible visual
|RZI]H% impairment in older persons [1-6]. In Australia, it is
&,C;_3
estimated that by the year 2021, the number of people
FmC
[u affected by cataract will increase by 63%, due to population
T/TMi&:?. aging [7]. Surgical intervention is an effective treatment
><"0GPxrx for cataract and normal vision (> 20/40) can usually
{Q
AV be restored with intraocular lens (IOL) implantation.
esK0H<] Cataract surgery with IOL implantation is currently the
+~eybm; most commonly performed, and is, arguably, the most
*#Hw6N0# cost effective surgical procedure worldwide. Performance
t B Kra Published: 20 April 2006
(bON[6OGm BMC Ophthalmology 2006, 6:17 doi:10.1186/1471-2415-6-17
IHvrx:7
Received: 14 December 2005
B),Z*lpC Accepted: 20 April 2006
0:qR,NW^# This article is available from:
http://www.biomedcentral.com/1471-2415/6/17 @"'$e_jj" © 2006 Tan et al; licensee BioMed Central Ltd.
0=V
-
{ This is an Open Access article distributed under the terms of the Creative Commons Attribution License (
http://creativecommons.org/licenses/by/2.0),
<^fvTb &* which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
c`xgz#
]v BMC Ophthalmology 2006, 6:17
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^Bu55q (page number not for citation purposes)
,BE4z2a of this surgical procedure has been continuously increasing
=Bw2{]w in the last two decades. Data from the Australian
Ym$=^f]- Health Insurance Commission has shown a steady
FgTWym_ increase in Medicare claims for cataract surgery [8]. A 2.6-
5;q{9wvqO fold increase in the total number of cataract procedures
g
~]?6;uu from 1985 to 1994 has been documented in Australia [9].
D%!GY1wdn The rate of cataract surgery per thousand persons aged 65
sG8G}f years or older has doubled in the last 20 years [8,9]. In the
)Rr0f 8 Blue Mountains Eye Study population, we observed a onethird
>S'IrnH'! increase in cataract surgery prevalence over a mean
sX,S]:X 6-year interval, from 6% to nearly 8% in two cross-sectional
MyaJhA6c population-based samples with a similar age range
OS sYmF [10]. Further increases in cataract surgery performance
xvTz|Y would be expected as a result of improved surgical skills
}B@44HdY and technique, together with extending cataract surgical
,f^ICM benefits to a greater number of older people and an
R/Z
zmb{ increased number of persons with surgery performed on
MkX=34oc^ both eyes.
|ZtNCB5{^j Both the prevalence and incidence of age-related cataract
MZ"|Jn link directly to the demand for, and the outcome of, cataract
tZan1C%p> surgery and eye health care provision. This report
][`% vj9r aimed to assess temporal changes in the prevalence of cortical
{.o@XP,. and nuclear cataract and posterior subcapsular cataract
}va>jfy (PSC) in two cross-sectional population-based
4}F~h surveys 6 years apart.
ppzQh1 Methods
cUC!'+L The Blue Mountains Eye Study (BMES) is a populationbased
/_</m?&.U& cohort study of common eye diseases and other
tR(nD UHV5 health outcomes. The study involved eligible permanent
r$W%d[pB
residents aged 49 years and older, living in two postcode
%jn)=;\ areas in the Blue Mountains, west of Sydney, Australia.
v"-K-AQjB Participants were identified through a census and were
0t7vg#v| invited to participate. The study was approved at each
\IZY\WU}2 stage of the data collection by the Human Ethics Committees
vKBijmE of the University of Sydney and the Western Sydney
n50WHlMtt Area Health Service and adhered to the recommendations
SM\qd4 of the Declaration of Helsinki. Written informed consent
ZQ{-6VCjl was obtained from each participant.
nXw98; Details of the methods used in this study have been
'^M.;Giz described previously [11]. The baseline examinations
|=AaGJx (BMES cross-section I) were conducted during 1992–
`IT]ZAem`/ 1994 and included 3654 (82.4%) of 4433 eligible residents.
GglGFXOL- Follow-up examinations (BMES IIA) were conducted
n x{MUN7 during 1997–1999, with 2335 (75.0% of BMES
}:57Ym)7w cross section I survivors) participating. A repeat census of
B>g(i=E the same area was performed in 1999 and identified 1378
EB VG@ newly eligible residents who moved into the area or the
?AK`M #M eligible age group. During 1999–2000, 1174 (85.2%) of
9}5o> iR this group participated in an extension study (BMES IIB).
glLoYRTi
BMES cross-section II thus includes BMES IIA (66.5%)
9g]%}+D and BMES IIB (33.5%) participants (n = 3509).
6V*,nocL_+ Similar procedures were used for all stages of data collection
-iL:D<!Cb_ at both surveys. A questionnaire was administered
me@)kQ8M including demographic, family and medical history. A
SDB \6[D detailed eye examination included subjective refraction,
4:5M,p slit-lamp (Topcon SL-7e camera, Topcon Optical Co,
G.`},c;A- Tokyo, Japan) and retroillumination (Neitz CT-R camera,
UE/JV_/S; Neitz Instrument Co, Tokyo, Japan) photography of the
:w+vi7l$ lens. Grading of lens photographs in the BMES has been
zK&1ti@wln previously described [12]. Briefly, masked grading was
*2pf
>UzL performed on the lens photographs using the Wisconsin
5RAhm0Op~. Cataract Grading System [13]. Cortical cataract and PSC
@dx8 {oQ were assessed from the retroillumination photographs by
u /]
P estimating the percentage of the circular grid involved.
[!4xInS Cortical cataract was defined when cortical opacity
"YaT1`Kr involved at least 5% of the total lens area. PSC was defined
;dPaWS1D
when opacity comprised at least 1% of the total lens area.
+(PUiiP'"v Slit-lamp photographs were used to assess nuclear cataract
n}t9Nf_ using the Wisconsin standard set of four lens photographs
*@p" [13]. Nuclear cataract was defined when nuclear opacity
JJmW%%]i was at least as great as the standard 4 photograph. Any cataract
k%X
$@NP was defined to include persons who had previous
mP Hto-=fB cataract surgery as well as those with any of three cataract
.$7RF!p types. Inter-grader reliability was high, with weighted
;
0Q" [[J kappa 0.82 for cortical cataract, 0.55 (simple kappa 0.75)
*5.wwV for nuclear cataract and 0.82 for PSC grading. The intragrader
7B=VH r reliability for nuclear cataract was assessed with
`a83bF35 simple kappa 0.83 for the senior grader who graded
%S%I
W nuclear cataract at both surveys. All PSC cases were confirmed
@6|<
c by an ophthalmologist (PM).
W=3#oX.GsU In cross-section I, 219 persons (6.0%) had missing or
g$^-WmX\m ungradable Neitz photographs, leaving 3435 with photographs
/#
]eVD
available for cortical cataract and PSC assessment,
Hy1$Kvub while 1153 (31.6%) had randomly missing or ungradable
tjt^R$[ @ Topcon photographs due to a camera malfunction, leaving
`g3AM%3 2501 with photographs available for nuclear cataract
DH%PkGn assessment. Comparison of characteristics between participants
R~T} with and without Neitz or Topcon photographs in
b>VV/j4!/ cross-section I showed no statistically significant differences
=Y81h- between the two groups, as reported previously
sv?Fx;d [12]. In cross-section II, 441 persons (12.5%) had missing
q)L4*O or ungradable Neitz photographs, leaving 3068 for cortical
sYBmL]Hr cataract and PSC assessment, and 648 (18.5%) had
>h)kbsSU0z missing or ungradable Topcon photographs, leaving 2860
eA86~M?<o for nuclear cataract assessment.
Er%&y Data analysis was performed using the Statistical Analysis
hPSMPbI System (SAS, SAS Institute, Cary, NC, USA). Age-adjusted
xYCJO(& prevalence was calculated using direct standardization of
E&
i (T2c the cross-section II population to the cross-section I population.
n"T ^ We assessed age-specific prevalence using an
cI'n[G interval of 5 years, so that participants within each age
'fl< ac,. group were independent between the two cross-sectional
-f&vH_eK surveys.
%K4M`R
|2] BMC Ophthalmology 2006, 6:17
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! e$ZOYe (page number not for citation purposes)
p$9Aadi] Results
Lm~<BBp. Characteristics of the two survey populations have been
,\iHgsZ previously compared [14] and showed that age and sex
(Fon!_$: distributions were similar. Table 1 compares participant
sdZ$3oE. characteristics between the two cross-sections. Cross-section
17Cb{Q II participants generally had higher rates of diabetes,
qsp.`9! hypertension, myopia and more users of inhaled steroids.
rhbz|Uq Cataract prevalence rates in cross-sections I and II are
p"p~Bx shown in Figure 1. The overall prevalence of cortical cataract
'~&W'='b; was 23.8% and 23.7% in cross-sections I and II,
2$5">%? respectively (age-sex adjusted P = 0.81). Corresponding
>-I <`y-H prevalence of PSC was 6.3% and 6.0% for the two crosssections
Cjr]l! (age-sex adjusted P = 0.60). There was an
KhfADqji| increased prevalence of nuclear cataract, from 18.7% in
Bk~C$'x4 cross-section I to 23.9% in cross-section II over the 6-year
o13jd NQ- period (age-sex adjusted P < 0.001). Prevalence of any cataract
|T""v_q (including persons who had cataract surgery), however,
]
5"k%v| was relatively stable (46.9% and 46.8% in crosssections
"jum*<QZz I and II, respectively).
hJ{u!:4 After age-standardization, these prevalence rates remained
=WT$\KYGv
stable for cortical cataract (23.8% and 23.5% in the two
z;>$["t]6 surveys) and PSC (6.3% and 5.9%). The slightly increased
*uyP+f2O prevalence of nuclear cataract (from 18.7% to 24.2%) was
d-_V*rYU not altered.
+_7a/3kh Table 2 shows the age-specific prevalence rates for cortical
HXa[0VOx cataract, PSC and nuclear cataract in cross-sections I and
:E.a.- II. A similar trend of increasing cataract prevalence with
{1OxJn1hd increasing age was evident for all three types of cataract in
jG[Vp b both surveys. Comparing the age-specific prevalence
tRdf:F\X
between the two surveys, a reduction in PSC prevalence in
X!Z)V)@J8 cross-section II was observed in the older age groups (≥ 75
9O3 #d years). In contrast, increased nuclear cataract prevalence
.Z[4:TS in cross-section II was observed in the older age groups (≥
#-;W|ib%z 70 years). Age-specific cortical cataract prevalence was relatively
6#+&/ "* consistent between the two surveys, except for a
GP%V(HhN reduction in prevalence observed in the 80–84 age group
bXnUz?1!d and an increasing prevalence in the older age groups (≥ 85
F<I*?
${[ years).
\ZLi Y Similar gender differences in cataract prevalence were
*2X~NJCt observed in both surveys (Table 3). Higher prevalence of
o0R?vnA= cortical and nuclear cataract in women than men was evident
[LnPV2@e but the difference was only significant for cortical
<==uK>pET cataract (age-adjusted odds ratio, OR, for women 1.3,
jhm3:;Z 95% confidence intervals, CI, 1.1–1.5 in cross-section I
'Bue* and OR 1.4, 95% CI 1.1–1.6 in cross-section II). In con-
.#QE*<T)] Table 1: Participant characteristics.
$t;:"i> Characteristics Cross-section I Cross-section II
S $p>sItO n % n %
a* cWj}u Age (mean) (66.2) (66.7)
+\T8`iCFB 50–54 485 13.3 350 10.0
uy
hh"[
55–59 534 14.6 580 16.5
vkE`T5?? 60–64 638 17.5 600 17.1
k9x[(
# 65–69 671 18.4 639 18.2
4^W!,@W 70–74 538 14.7 572 16.3
VP#KoX85 75–79 422 11.6 407 11.6
MI`qzC*% 80–84 230 6.3 226 6.4
`}?;Ow&2CY 85–89 100 2.7 110 3.1
3lp'U&3`5 90+ 36 1.0 24 0.7
T>B'T3or Female 2072 56.7 1998 57.0
aoey
5hts Ever Smokers 1784 51.2 1789 51.2
L(;$(k-/( Use of inhaled steroids 370 10.94 478 13.8^
zTa5N History of:
w#b@6d Diabetes 284 7.8 347 9.9^
hBX*02p Hypertension 1669 46.0 1825 52.2^
VgNB^w Emmetropia* 1558 42.9 1478 42.2
@ual+=L Myopia* 442 12.2 495 14.1^
w,p'$WC* Hyperopia* 1633 45.0 1532 43.7
gQPw+0w n = number of persons affected
<<0sv9qw1 * best spherical equivalent refraction correction
d=vuy
^ P < 0.01
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r:bJU1P1$s (page number not for citation purposes)
Z5vdH5?!r t
}:2##<"\t rast, men had slightly higher PSC prevalence than women
T[SK>z in both cross-sections but the difference was not significant
;stjqTd (OR 1.1, 95% CI 0.8–1.4 for men in cross-section I
-P}A26qB and OR 1.2, 95% 0.9–1.6 in cross-section II).
8* A%k1+ Discussion
@-sWXz*W Findings from two surveys of BMES cross-sectional populations
!h.hJt with similar age and gender distribution showed
aZb\uMePK that the prevalence of cortical cataract and PSC remained
iN&oSpQ stable, while the prevalence of nuclear cataract appeared
AXlVH%' to have increased. Comparison of age-specific prevalence,
H7Q$k4\l with totally independent samples within each age group,
q
\@Zf} confirmed the robustness of our findings from the two
\E?3nQM survey samples. Although lens photographs taken from
X]=eC6M}:V the two surveys were graded for nuclear cataract by the
O(/~cQ same graders, who documented a high inter- and intragrader
yP{ 52%|+ reliability, we cannot exclude the possibility that
I;w! variations in photography, performed by different photographers,
-FJ3;fP& may have contributed to the observed difference
M 2hZ' in nuclear cataract prevalence. However, the overall
A`uHZCwJ5 Table 2: Age-specific prevalence of cataract types in cross sections I and II.
ID_4M_G Cataract type Age (years) Cross-section I Cross-section II
o-@01_j
n % (95% CL)* n % (95% CL)*
ZPH_s^ Cortical 50–54 473 4.4 (2.6–6.3) 338 7.4 (4.6–10.2)
@*y4uI6& 55–59 522 9.2 (6.7–11.7) 542 9.0 (6.6–11.5)
K;6#v% 60–64 615 16.4 (13.5–19.4) 556 16.7 (13.6–19.8)
:GIBB=D9 65–69 653 26.2 (22.8–29.6) 581 23.6 (20.1–27.0)
`^[k8Z( 70–74 516 31.2 (27.2–35.2) 514 35.4 (31.3–39.6)
N~,
Ipf 75–79 366 40.2 (35.1–45.2) 332 39.8 (34.5–45.1)
Q` u# 80–84 194 58.8 (51.8–65.8) 163 42.9 (35.3–50.6)
}? _KZ)
85–89 74 52.7 (41.1–64.4) 73 54.8 (43.1–66.5)
VNTbjn]
90+ 22 68.2 (47.0–89.3) 14 78.6 (54.0–103.2)
7Vy_Cec1 PSC 50–54 474 2.7 (1.3–4.2) 338 2.4 (0.7–4.0)
+ALrHFG 55–59 522 2.9 (1.4–4.3) 541 2.6 (1.3–3.9)
bJIYe ld 60–64 616 4.6 (2.9–6.2) 548 5.7 (3.7–7.6)
9I/l+IS"X 65–69 655 6.3 (4.4–8.1) 573 4.5 (2.8–6.3)
-W9DH^EL< 70–74 517 6.8 (4.6–8.9) 505 9.7 (7.1–12.3)
?(gha 75–79 367 11.4 (8.2–14.7) 327 9.5 (6.3–12.7)
xfeE D^? 80–84 196 12.2 (7.6–16.9) 155 10.3 (5.5–15.2)
Q2 !GWz$ 85–89 74 18.9 (9.8–28.1) 69 11.6 (3.9–19.4)
HF*0 90+ 23 21.7 (3.5–40.0) 11 0.0
3*<@PXpK& Nuclear 50–54 323 1.6 (0.2–2.9) 331 0.9 (–0.2–1.9)
kf'(u..G 55–59 386 2.3 (0.8–3.8) 507 3.6 (1.9–5.2)
@/^<9 60–64 453 5.3 (3.2–7.4) 501 11.6 (8.8–14.4)
$0 .6No_| 65–69 478 17.2 (13.8–20.1) 534 18.5 (15.2–21.9)
d` ttWWPw 70–74 392 27.6 (23.1–32.0) 453 36.0 (31.6–40.4)
q~}oU5 75–79 255 45.1 (39.0–51.3) 302 55.6 (50.0–61.3)
w( V%EEk 80–84 146 54.1 (45.9–62.3) 147 73.5 (66.3–80.7)
i?!9%U!z4 85–89 50 64.0 (50.2–77.8) 70 80.0 (70.4–89.6)
]jD\4\M} 90+ 18 72.2 (49.3–95.1) 15 73.3 (48.0–98.7)
.jD!+wv{9 n = number of persons
oYN"L * 95% Confidence Limits
O8 .iP+ Cataract FMioguunrtea i1n ps rEeyvea lSetnucdey in cross-sections I and II of the Blue
W+a/>U Cataract prevalence in cross-sections I and II of the Blue
'etA1]<N Mountains Eye Study.
JlnmG<WLT 0
lC#wh2B6 10
J+t51B(a 20
rhkKK_ 30
-u@ ^P7 40
-7&ywgxl 50
I-^sJ@V; cortical PSC nuclear any
1 |{s8[;8 cataract
>s5}pkAv|e Cataract type
/V*SI!C<f %
{LjzkXs Cross-section I
4tkT\. Cross-section II
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Z5TA4Q+Q (page number not for citation purposes)
7V5c`:" prevalence of any cataract (including cataract surgery) was
9xbT?$^ relatively stable over the 6-year period.
FQ
0&{ulb Although different population-based studies used different
KWo Ps%G grading systems to assess cataract [15], the overall
LC]0c)v# prevalence of the three cataract types were similar across
=!L}/Dl different study populations [12,16-23]. Most studies have
1av#u:jy~> suggested that nuclear cataract is the most prevalent type
SLEOcOAmD of cataract, followed by cortical cataract [16-20]. Ours and
?<jWEz= other studies reported that cortical cataract was the most
60|PVsmDm prevalent type [12,21-23].
K9ia|2f Our age-specific prevalence data show a reduction of
EHq;eF 15.9% in cortical cataract prevalence for the 80–84 year
Mlc_w19C9 age group, concordant with an increase in cataract surgery
O\f`+Q`0 prevalence by 9% in those aged 80+ years observed in the
OB9E30 same study population [10]. Although cortical cataract is
sxr,]@ thought to be the least likely cataract type leading to a cataract
itNuY<" surgery, this may not be the case in all older persons.
MH)V=xU|) A relatively stable cortical cataract and PSC prevalence
DNZ,rL:h over the 6-year period is expected. We cannot offer a
b;D definitive explanation for the increase in nuclear cataract
B?&0NpVD prevalence. A possible explanation could be that a moderate
e1XKlgl level of nuclear cataract causes less visual disturbance
\dU.#^ryp than the other two types of cataract, thus for the oldest age
;@k=9o]A groups, persons with nuclear cataract could have been less
.aO6Y+Y likely to have surgery unless it is very dense or co-existing
iLv
-*%% with cortical cataract or PSC. Previous studies have shown
tJu:N'=Dy that functional vision and reading performance were high
S -mpob) in patients undergoing cataract surgery who had nuclear
R\ 8[6H cataract only compared to those with mixed type of cataract
P9m (nuclear and cortical) or PSC [24,25]. In addition, the
!X: TieyVu overall prevalence of any cataract (including cataract surgery)
yCR8 c,'8 was similar in the two cross-sections, which appears
?J+jv to support our speculation that in the oldest age group,
-q9m@!L nuclear cataract may have been less likely to be operated
=Pn"nkpML than the other two types of cataract. This could have
UTE6U6 resulted in an increased nuclear cataract prevalence (due
m{ani/bt to less being operated), compensated by the decreased
Hd;NvNS prevalence of cortical cataract and PSC (due to these being
Tv'1
IE more likely to be operated), leading to stable overall prevalence
DjaXJ?' of any cataract.
075IW"p' Possible selection bias arising from selective survival
,7cw%mQA among persons without cataract could have led to underestimation
):4)8@]5M of cataract prevalence in both surveys. We
5"40{3 assume that such an underestimation occurred equally in
!21G$[H both surveys, and thus should not have influenced our
CLZj=J2 assessment of temporal changes.
y`$qcEw Measurement error could also have partially contributed
sF)$<[w to the observed difference in nuclear cataract prevalence.
vv)w@A:Vn) Assessment of nuclear cataract from photographs is a
uP
cx6X3] potentially subjective process that can be influenced by
#t1? *4.p variations in photography (light exposure, focus and the
`K0.6i [p slit-lamp angle when the photograph was taken) and
~)$R'= grading. Although we used the same Topcon slit-lamp
*;Q#UH camera and the same two graders who graded photos
% + from both surveys, we are still not able to exclude the possibility
rZ.=Lq of a partial influence from photographic variation
+ W1l9n* on this result.
(&)uWjq
` A similar gender difference (women having a higher rate
/ QL<>g than men) in cortical cataract prevalence was observed in
X`&Us both surveys. Our findings are in keeping with observations
Xo(W\Pes from the Beaver Dam Eye Study [18], the Barbados
RF6]_-
Eye Study [22] and the Lens Opacities Case-Control
9`/ywt3Y Group [26]. It has been suggested that the difference
G,Yctv could be related to hormonal factors [18,22]. A previous
:-+][ [ study on biochemical factors and cataract showed that a
~FI} [6Dd lower level of iron was associated with an increased risk of
uCW}q.
@4 cortical cataract [27]. No interaction between sex and biochemical
|@b|Q, factors were detected and no gender difference
OmK0-fa/ was assessed in this study [27]. The gender difference seen
V^D1:9i in cortical cataract could be related to relatively low iron
V#1v5mWVx levels and low hemoglobin concentration usually seen in
|C+
5 women [28]. Diabetes is a known risk factor for cortical
FDFVhcr Table 3: Gender distribution of cataract types in cross-sections I and II.
xXV15%& Cataract type Gender Cross-section I Cross-section II
wN0?~ n % (95% CL)* n % (95% CL)*
e6gj'GmY Cortical Male 1496 21.1 (19.0–23.1) 1328 20.4 (18.2–22.6)
3\<(!yY8 Female 1939 25.9 (23.9–27.8) 1785 26.2 (24.2–28.3)
bX`]<$dr3 PSC Male 1500 6.5 (5.2–7.7) 1314 6.4 (5.1–7.7)
aeLIs SEx Female 1944 6.2 (5.1–7.2) 1753 5.7 (4.6–6.7)
M
S|1Q@S9 Nuclear Male 1106 17.6 (15.4–19.9) 1225 22.5 (20.1–24.8)
RKs_k`N0 Female 1395 19.5 (17.4–21.6) 1635 25.0 (22.9–27.1)
j\.pS^+ n = number of persons
hA~5,K0b * 95% Confidence Limits
CS"k0V44}
BMC Ophthalmology 2006, 6:17
http://www.biomedcentral.com/1471-2415/6/17 %HZ!s
`w_ Page 6 of 7
;P|v'NNI (page number not for citation purposes)
[nsTO5G$u cataract but in this particular population diabetes is more
h2]GV- prevalent in men than women in all age groups [29]. Differential
^&c|z35F exposures to cataract risk factors or different dietary
]=0D~3o3 or lifestyle patterns between men and women may
x4_FG{AIu also be related to these observations and warrant further
Ce3
study.
ybm&g( -\ Conclusion
~65lDFY/ In summary, in two population-based surveys 6 years
@(tiPV apart, we have documented a relatively stable prevalence
##NowO of cortical cataract and PSC over the period. The observed
!. ={p8X-x overall increased nuclear cataract prevalence by 5% over a
!3at(+4 6-year period needs confirmation by future studies, and
b(g?X
(& reasons for such an increase deserve further study.
^UpwVKdP Competing interests
oU~ e| The author(s) declare that they have no competing interests.
PmE2T\{s! Authors' contributions
[Hp"a^~r| AGT graded the photographs, performed literature search
F
a'2i< and wrote the first draft of the manuscript. JJW graded the
<~qhy{hRn photographs, critically reviewed and modified the manuscript.
|a Ht6F ER performed the statistical analysis and critically
lhV'Q]s@6 reviewed the manuscript. PM designed and directed the
?r6uEZ study, adjudicated cataract cases and critically reviewed
_9zydtw and modified the manuscript. All authors read and
v:]
AS: approved the final manuscript.
[R[Suf Acknowledgements
#
OQ(oyT This study was supported by the Australian National Health & Medical
x-{awP Research Council, Canberra, Australia (Grant Nos 974159, 991407). The
s8N\cOd#i abstract was presented at the Association for Research in Vision and Ophthalmology
m)9qO7P (ARVO) meeting in Fort Lauderdale, Florida, USA, May 2005.
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