BioMed Central
?@U7tNI Page 1 of 7
jd9GueV*( (page number not for citation purposes)
h_K(8{1 BMC Ophthalmology
=%,;=4w Research article Open Access
)3_I-Ia Comparison of age-specific cataract prevalence in two
!r:X`~\a population-based surveys 6 years apart
=`f6@4H Ava Grace Tan†, Jie Jin Wang*†, Elena Rochtchina† and Paul Mitchell†
tETT\y|' Address: Centre for Vision Research, Westmead Millennium Institute, Department of Ophthalmology, University of Sydney, Westmead Hospital,
pK=$)<I"6 Westmead, NSW, Australia
wB6ILTu1 Email: Ava Grace Tan -
ava_tan@wmi.usyd.edu.au; Jie Jin Wang* -
jiejin_wang@wmi.usyd.edu.au;
'p=5hsG Elena Rochtchina -
elena_rochtchina@wmi.usyd.edu.au; Paul Mitchell -
paul_mitchell@wmi.usyd.edu.au mzufl:-= * Corresponding author †Equal contributors
c\i`=>%b@ Abstract
q\Cg2[nn2 Background: In this study, we aimed to compare age-specific cortical, nuclear and posterior
v)|[= subcapsular (PSC) cataract prevalence in two surveys 6 years apart.
l[=7<F Methods: The Blue Mountains Eye Study examined 3654 participants (82.4% of those eligible) in
t^0^He$Ot cross-section I (1992–4) and 3509 participants (75.1% of survivors and 85.2% of newly eligible) in
l4+!H\2 cross-section II (1997–2000, 66.5% overlap with cross-section I). Cataract was assessed from lens
Pl_4;q!$ photographs following the Wisconsin Cataract Grading System. Cortical cataract was defined if
rrK&XP& cortical opacity comprised ≥ 5% of lens area. Nuclear cataract was defined if nuclear opacity ≥
4`F(RweGx Wisconsin standard 4. PSC was defined if any present. Any cataract was defined to include persons
ahi lp$v who had previous cataract surgery. Weighted kappa for inter-grader reliability was 0.82, 0.55 and
?bc-?<Xk 0.82 for cortical, nuclear and PSC cataract, respectively. We assessed age-specific prevalence using
>AsD6]
an interval of 5 years, so that participants within each age group were independent between the
`oP<mLxle two surveys.
Ad)Po Results: Age and gender distributions were similar between the two populations. The age-specific
h^klP: Q prevalence of cortical (23.8% in 1st, 23.7% in 2nd) and PSC cataract (6.3%, 6.0%) was similar. The
|cpBoU prevalence of nuclear cataract increased slightly from 18.7% to 23.9%. After age standardization,
cjzhuH/y the similar prevalence of cortical (23.8%, 23.5%) and PSC cataract (6.3%, 5.9%), and the increased
>$,A [|R prevalence of nuclear cataract (18.7%, 24.2%) remained.
}} cz95 Conclusion: In two surveys of two population-based samples with similar age and gender
Bw-<xwD distributions, we found a relatively stable cortical and PSC cataract prevalence over a 6-year period.
.<zW(PW The increased prevalence of nuclear cataract deserves further study.
M<Mr
L[*j Background
NpV#zzE Age-related cataract is the leading cause of reversible visual
x2p}0N impairment in older persons [1-6]. In Australia, it is
8hWBTUN estimated that by the year 2021, the number of people
n:JWu0
,h affected by cataract will increase by 63%, due to population
IXb]\ ) aging [7]. Surgical intervention is an effective treatment
mG4myQ?$ for cataract and normal vision (> 20/40) can usually
:uhU<H<,f be restored with intraocular lens (IOL) implantation.
x`8rR;N! Cataract surgery with IOL implantation is currently the
P3|_RHIb most commonly performed, and is, arguably, the most
.kpL?_ cost effective surgical procedure worldwide. Performance
SS?^-BI Published: 20 April 2006
lz>YjK: BMC Ophthalmology 2006, 6:17 doi:10.1186/1471-2415-6-17
6?y<F4
Received: 14 December 2005
4;anoqiG\ Accepted: 20 April 2006
/DOV/>@5% This article is available from:
http://www.biomedcentral.com/1471-2415/6/17 noY~fq/U © 2006 Tan et al; licensee BioMed Central Ltd.
j8p</gd This is an Open Access article distributed under the terms of the Creative Commons Attribution License (
http://creativecommons.org/licenses/by/2.0),
""cnZZ5) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
? b;_T,S[ BMC Ophthalmology 2006, 6:17
http://www.biomedcentral.com/1471-2415/6/17 6&~
8TH Page 2 of 7
Rh!B4oB4 (page number not for citation purposes)
.!uXhF' of this surgical procedure has been continuously increasing
O;RsYs9 in the last two decades. Data from the Australian
e~#;ux Health Insurance Commission has shown a steady
@c&}\#; increase in Medicare claims for cataract surgery [8]. A 2.6-
hLYy fold increase in the total number of cataract procedures
D$C
>ZF from 1985 to 1994 has been documented in Australia [9].
8U,VpuQ: The rate of cataract surgery per thousand persons aged 65
RTN?[` years or older has doubled in the last 20 years [8,9]. In the
sywSvnPuYZ Blue Mountains Eye Study population, we observed a onethird
\Fd6Q_
increase in cataract surgery prevalence over a mean
VyQ@. Lm 6-year interval, from 6% to nearly 8% in two cross-sectional
;pk4Voo$ population-based samples with a similar age range
#-76E [10]. Further increases in cataract surgery performance
5`su^ would be expected as a result of improved surgical skills
}yQ&[Mt and technique, together with extending cataract surgical
!*2cK>` benefits to a greater number of older people and an
ZL!,s# increased number of persons with surgery performed on
@.IGOh both eyes.
=Uy;8et Both the prevalence and incidence of age-related cataract
:H9\nU1
link directly to the demand for, and the outcome of, cataract
xJCMxt2Y surgery and eye health care provision. This report
R _#x aimed to assess temporal changes in the prevalence of cortical
x`7Ch3`4} and nuclear cataract and posterior subcapsular cataract
;E,^bt<U (PSC) in two cross-sectional population-based
I,[njlO: surveys 6 years apart.
OS$
}ej\ Methods
tX'`4!{@+ The Blue Mountains Eye Study (BMES) is a populationbased
d|I_SI
1 cohort study of common eye diseases and other
i}&&
rr health outcomes. The study involved eligible permanent
b/#SkxW#S residents aged 49 years and older, living in two postcode
p\;\hHai areas in the Blue Mountains, west of Sydney, Australia.
}%8 :8_Ke Participants were identified through a census and were
x*`S>_j27= invited to participate. The study was approved at each
9Hu;CKs stage of the data collection by the Human Ethics Committees
"0*yD[2 of the University of Sydney and the Western Sydney
!
qVuhad. Area Health Service and adhered to the recommendations
m!22tpb of the Declaration of Helsinki. Written informed consent
'iY~F 0U was obtained from each participant.
]e
t
]Vkg Details of the methods used in this study have been
.j
et0w described previously [11]. The baseline examinations
-JKl\ E (BMES cross-section I) were conducted during 1992–
R"wBDWs 1994 and included 3654 (82.4%) of 4433 eligible residents.
<mrvuWg0 Follow-up examinations (BMES IIA) were conducted
7$"A2x during 1997–1999, with 2335 (75.0% of BMES
n%faD cross section I survivors) participating. A repeat census of
gg0rkg
the same area was performed in 1999 and identified 1378
@d&JtA newly eligible residents who moved into the area or the
f: 9bq}vH eligible age group. During 1999–2000, 1174 (85.2%) of
TdU'L:<4l this group participated in an extension study (BMES IIB).
|D% O`[k+ BMES cross-section II thus includes BMES IIA (66.5%)
\DiAfx<Ub and BMES IIB (33.5%) participants (n = 3509).
bcR";cE Similar procedures were used for all stages of data collection
QkF
B\v at both surveys. A questionnaire was administered
~xa yGk including demographic, family and medical history. A
.Ei#mG-=}& detailed eye examination included subjective refraction,
8aqH;|fG} slit-lamp (Topcon SL-7e camera, Topcon Optical Co,
dfA2G<Uc Tokyo, Japan) and retroillumination (Neitz CT-R camera,
dc dVB>D Neitz Instrument Co, Tokyo, Japan) photography of the
j%U'mGx lens. Grading of lens photographs in the BMES has been
DL*&e|:q previously described [12]. Briefly, masked grading was
'uW&ADp performed on the lens photographs using the Wisconsin
w61*jnvi@ Cataract Grading System [13]. Cortical cataract and PSC
{ v [ were assessed from the retroillumination photographs by
0iAQ;<*xi estimating the percentage of the circular grid involved.
N!//m?} Cortical cataract was defined when cortical opacity
M?d (-en involved at least 5% of the total lens area. PSC was defined
]IclA6 when opacity comprised at least 1% of the total lens area.
o
zMn8@R Slit-lamp photographs were used to assess nuclear cataract
uhm3}mWv using the Wisconsin standard set of four lens photographs
S^x?<kYQau [13]. Nuclear cataract was defined when nuclear opacity
<^w4+5sT/ was at least as great as the standard 4 photograph. Any cataract
K8JshFIe was defined to include persons who had previous
~_F <"40 cataract surgery as well as those with any of three cataract
Lng@'Yr types. Inter-grader reliability was high, with weighted
l[6lXR&| kappa 0.82 for cortical cataract, 0.55 (simple kappa 0.75)
Zg4kO;r08 for nuclear cataract and 0.82 for PSC grading. The intragrader
z?Cez*.h> reliability for nuclear cataract was assessed with
z.~jqxA9 simple kappa 0.83 for the senior grader who graded
'-BD.^!! nuclear cataract at both surveys. All PSC cases were confirmed
'si{6t| by an ophthalmologist (PM).
2BO&OX|X In cross-section I, 219 persons (6.0%) had missing or
S"/-)_{ ungradable Neitz photographs, leaving 3435 with photographs
]G~Z'fs<( available for cortical cataract and PSC assessment,
cAn
_:^ while 1153 (31.6%) had randomly missing or ungradable
v"l8[:: Topcon photographs due to a camera malfunction, leaving
*
*.g^Pyc 2501 with photographs available for nuclear cataract
PDS?>Jg( assessment. Comparison of characteristics between participants
MnP+L'| with and without Neitz or Topcon photographs in
%R<xe.X cross-section I showed no statistically significant differences
\cdns; between the two groups, as reported previously
0$_WIk [12]. In cross-section II, 441 persons (12.5%) had missing
8 q> or ungradable Neitz photographs, leaving 3068 for cortical
j XYr&F cataract and PSC assessment, and 648 (18.5%) had
k3T374t1b missing or ungradable Topcon photographs, leaving 2860
rYM@e for nuclear cataract assessment.
K,,'{j2#f Data analysis was performed using the Statistical Analysis
VNs3. System (SAS, SAS Institute, Cary, NC, USA). Age-adjusted
buDz]ec
b prevalence was calculated using direct standardization of
pjma
<
^|F the cross-section II population to the cross-section I population.
>[ g=G We assessed age-specific prevalence using an
qYQ
vjp interval of 5 years, so that participants within each age
!R![:T\, group were independent between the two cross-sectional
B
h&dV%' surveys.
O"#/>hmv- BMC Ophthalmology 2006, 6:17
http://www.biomedcentral.com/1471-2415/6/17 #8$"84&N. Page 3 of 7
R\-]$\1D (page number not for citation purposes)
TkVqv v Results
mNsd&Rk' Characteristics of the two survey populations have been
TuC previously compared [14] and showed that age and sex
7nsovWp distributions were similar. Table 1 compares participant
Tv9\`F[ characteristics between the two cross-sections. Cross-section
-`NzBuV$2, II participants generally had higher rates of diabetes,
_M^^0kf hypertension, myopia and more users of inhaled steroids.
\uO^wJ} Cataract prevalence rates in cross-sections I and II are
vOq N=bp shown in Figure 1. The overall prevalence of cortical cataract
wB:<ICm was 23.8% and 23.7% in cross-sections I and II,
^9><qKbO respectively (age-sex adjusted P = 0.81). Corresponding
\Yn0|j> prevalence of PSC was 6.3% and 6.0% for the two crosssections
pK ^$^*# (age-sex adjusted P = 0.60). There was an
(/E@.z[1 increased prevalence of nuclear cataract, from 18.7% in
4K 8 (H9( cross-section I to 23.9% in cross-section II over the 6-year
D G|v'# period (age-sex adjusted P < 0.001). Prevalence of any cataract
qC5IV}9` (including persons who had cataract surgery), however,
;%k C?Vzi was relatively stable (46.9% and 46.8% in crosssections
P#V}l'j(<a I and II, respectively).
>x6)AH. After age-standardization, these prevalence rates remained
+"1-W>HV stable for cortical cataract (23.8% and 23.5% in the two
T^{=c
x9x9 surveys) and PSC (6.3% and 5.9%). The slightly increased
{ `xC~B h prevalence of nuclear cataract (from 18.7% to 24.2%) was
CSz+cS not altered.
bkz/V/ Y Table 2 shows the age-specific prevalence rates for cortical
y.s\MWvv>u cataract, PSC and nuclear cataract in cross-sections I and
rHuzGSX54 II. A similar trend of increasing cataract prevalence with
#N%j9 increasing age was evident for all three types of cataract in
i|xz
both surveys. Comparing the age-specific prevalence
QjD=JC+ between the two surveys, a reduction in PSC prevalence in
!}5rd\ cross-section II was observed in the older age groups (≥ 75
IM,4Si2 years). In contrast, increased nuclear cataract prevalence
;.b^&h in cross-section II was observed in the older age groups (≥
-%Rbd0gVH\ 70 years). Age-specific cortical cataract prevalence was relatively
~)zxIO! consistent between the two surveys, except for a
TQPrOs? reduction in prevalence observed in the 80–84 age group
Qc=-M'9 and an increasing prevalence in the older age groups (≥ 85
PS=q):R| years).
f0R+Mz8{ Similar gender differences in cataract prevalence were
0{u%J%; observed in both surveys (Table 3). Higher prevalence of
7 toI
bC# cortical and nuclear cataract in women than men was evident
5:#|Op N but the difference was only significant for cortical
$RunGaX!=N cataract (age-adjusted odds ratio, OR, for women 1.3,
\
H#" 95% confidence intervals, CI, 1.1–1.5 in cross-section I
=-&h@mB;G and OR 1.4, 95% CI 1.1–1.6 in cross-section II). In con-
>
_ G'o Table 1: Participant characteristics.
=''b `T$ Characteristics Cross-section I Cross-section II
,el[A`b n % n %
U0iV
E+)Bt Age (mean) (66.2) (66.7)
/ {[p?7x> 50–54 485 13.3 350 10.0
FMhuCl
2 55–59 534 14.6 580 16.5
<M}O&?N
8x 60–64 638 17.5 600 17.1
!H<%X~|, 65–69 671 18.4 639 18.2
YU!s;h 70–74 538 14.7 572 16.3
4i5b.bU$ 75–79 422 11.6 407 11.6
|`s:&<W+kp 80–84 230 6.3 226 6.4
Aon.Y Z 85–89 100 2.7 110 3.1
-WR<tkK 90+ 36 1.0 24 0.7
[7g-M/jvY Female 2072 56.7 1998 57.0
N9y+Psh
Ever Smokers 1784 51.2 1789 51.2
wXKt)3dm u Use of inhaled steroids 370 10.94 478 13.8^
Zb|a\z8 ? History of:
5tzO=gO[ Diabetes 284 7.8 347 9.9^
j)Kd'Va Hypertension 1669 46.0 1825 52.2^
TIR Is1 Emmetropia* 1558 42.9 1478 42.2
8G9( )UF. Myopia* 442 12.2 495 14.1^
}$r]\v Hyperopia* 1633 45.0 1532 43.7
xU6dRjYhH9 n = number of persons affected
+P,ic*Kq* * best spherical equivalent refraction correction
zr_L
V_e ^ P < 0.01
3K/'K[~ BMC Ophthalmology 2006, 6:17
http://www.biomedcentral.com/1471-2415/6/17 s.n:;8RibP Page 4 of 7
E*fa&G~s ) (page number not for citation purposes)
@Y>PtA&w* t
H*P+>j& rast, men had slightly higher PSC prevalence than women
:i@
$s/ in both cross-sections but the difference was not significant
:XPat93w (OR 1.1, 95% CI 0.8–1.4 for men in cross-section I
{XUSw8W' and OR 1.2, 95% 0.9–1.6 in cross-section II).
W}}
ZP]; Discussion
3Co1bY: Findings from two surveys of BMES cross-sectional populations
HDKY7Yr with similar age and gender distribution showed
%
}Y&qT? that the prevalence of cortical cataract and PSC remained
>!{8)ti stable, while the prevalence of nuclear cataract appeared
wL^x9O|`p9 to have increased. Comparison of age-specific prevalence,
i[{*(Y$L
with totally independent samples within each age group,
%L7DC`
confirmed the robustness of our findings from the two
\Y!=O=za] survey samples. Although lens photographs taken from
~Fl\
c- the two surveys were graded for nuclear cataract by the
ITi#p% same graders, who documented a high inter- and intragrader
,Mi'NO reliability, we cannot exclude the possibility that
l @@pXg3 variations in photography, performed by different photographers,
@ PhAg may have contributed to the observed difference
,#
.12Q! in nuclear cataract prevalence. However, the overall
&jQqlQ j Table 2: Age-specific prevalence of cataract types in cross sections I and II.
3u
^wK Cataract type Age (years) Cross-section I Cross-section II
%W| Sl n % (95% CL)* n % (95% CL)*
-eS r Cortical 50–54 473 4.4 (2.6–6.3) 338 7.4 (4.6–10.2)
R~hIo aiN 55–59 522 9.2 (6.7–11.7) 542 9.0 (6.6–11.5)
a|3+AWL% 60–64 615 16.4 (13.5–19.4) 556 16.7 (13.6–19.8)
=?wDQ: 65–69 653 26.2 (22.8–29.6) 581 23.6 (20.1–27.0)
},G
rg~l 70–74 516 31.2 (27.2–35.2) 514 35.4 (31.3–39.6)
0Q,Tc
j 75–79 366 40.2 (35.1–45.2) 332 39.8 (34.5–45.1)
B9cWxe4R# 80–84 194 58.8 (51.8–65.8) 163 42.9 (35.3–50.6)
/d Ua 85–89 74 52.7 (41.1–64.4) 73 54.8 (43.1–66.5)
Nlwt}7 90+ 22 68.2 (47.0–89.3) 14 78.6 (54.0–103.2)
\_(0V" PSC 50–54 474 2.7 (1.3–4.2) 338 2.4 (0.7–4.0)
eoQt87VCU 55–59 522 2.9 (1.4–4.3) 541 2.6 (1.3–3.9)
p} eO 60–64 616 4.6 (2.9–6.2) 548 5.7 (3.7–7.6)
\VW":+ 65–69 655 6.3 (4.4–8.1) 573 4.5 (2.8–6.3)
o54=^@>O<j 70–74 517 6.8 (4.6–8.9) 505 9.7 (7.1–12.3)
/7,@q?v 75–79 367 11.4 (8.2–14.7) 327 9.5 (6.3–12.7)
$*P+ 80–84 196 12.2 (7.6–16.9) 155 10.3 (5.5–15.2)
Jcs
/i 85–89 74 18.9 (9.8–28.1) 69 11.6 (3.9–19.4)
,nP nH1vb 90+ 23 21.7 (3.5–40.0) 11 0.0
3!QXzT$E Nuclear 50–54 323 1.6 (0.2–2.9) 331 0.9 (–0.2–1.9)
aM,g@'.= 55–59 386 2.3 (0.8–3.8) 507 3.6 (1.9–5.2)
v~._]f$: 60–64 453 5.3 (3.2–7.4) 501 11.6 (8.8–14.4)
vMn$lT@ 65–69 478 17.2 (13.8–20.1) 534 18.5 (15.2–21.9)
een62-` 70–74 392 27.6 (23.1–32.0) 453 36.0 (31.6–40.4)
Fy$C._C$ 75–79 255 45.1 (39.0–51.3) 302 55.6 (50.0–61.3)
.N\t3\9} 80–84 146 54.1 (45.9–62.3) 147 73.5 (66.3–80.7)
X`eX+9 85–89 50 64.0 (50.2–77.8) 70 80.0 (70.4–89.6)
dpt P(H 90+ 18 72.2 (49.3–95.1) 15 73.3 (48.0–98.7)
oq1wU@n n = number of persons
^U,C])n * 95% Confidence Limits
By}Z
HK94I Cataract FMioguunrtea i1n ps rEeyvea lSetnucdey in cross-sections I and II of the Blue
78?{;iNv Cataract prevalence in cross-sections I and II of the Blue
\X]I: 0^j Mountains Eye Study.
>!o!rs 0
dI=&gz 10
B/3xV:Gy 20
d+ $:u 30
k{ZQM 40
A4;~+L :M 50
@KZW*-" cortical PSC nuclear any
3k8.5W cataract
!Ow
M-t Cataract type
c5i7mx:. %
3qV\XC+ Cross-section I
9uX15a Cross-section II
RcO.1@2 BMC Ophthalmology 2006, 6:17
http://www.biomedcentral.com/1471-2415/6/17 ^ ~Tn[w W_ Page 5 of 7
W}(T5D" 3x (page number not for citation purposes)
65RD68a prevalence of any cataract (including cataract surgery) was
;MlPP)*k relatively stable over the 6-year period.
bV#j@MJ~0 Although different population-based studies used different
@XcrHnH9 grading systems to assess cataract [15], the overall
nKTi"2dm prevalence of the three cataract types were similar across
Wm)Id_ different study populations [12,16-23]. Most studies have
?D_}',Wx suggested that nuclear cataract is the most prevalent type
yy3`E}vX7 of cataract, followed by cortical cataract [16-20]. Ours and
\y7Gi}nI other studies reported that cortical cataract was the most
xKepZ prevalent type [12,21-23].
KWi|7z(L=
Our age-specific prevalence data show a reduction of
C 8d9(u 15.9% in cortical cataract prevalence for the 80–84 year
L,,*8 age group, concordant with an increase in cataract surgery
plNw>rFa prevalence by 9% in those aged 80+ years observed in the
`sd
H
q same study population [10]. Although cortical cataract is
ZHj7^y@P thought to be the least likely cataract type leading to a cataract
r& :v( surgery, this may not be the case in all older persons.
XuU>.T$] c A relatively stable cortical cataract and PSC prevalence
Fa #5a'}I over the 6-year period is expected. We cannot offer a
#wh[F"zX definitive explanation for the increase in nuclear cataract
GQE7P()
prevalence. A possible explanation could be that a moderate
Kc>
Rd level of nuclear cataract causes less visual disturbance
0 r;tI" than the other two types of cataract, thus for the oldest age
-KqMSf&9 groups, persons with nuclear cataract could have been less
J DOs.w likely to have surgery unless it is very dense or co-existing
X7MA>j3m with cortical cataract or PSC. Previous studies have shown
;YBk.}
% that functional vision and reading performance were high
W{ZJ^QAq/ in patients undergoing cataract surgery who had nuclear
^Q!A4qOQ cataract only compared to those with mixed type of cataract
7--E$!9O, (nuclear and cortical) or PSC [24,25]. In addition, the
C7&L9k~jf overall prevalence of any cataract (including cataract surgery)
ykxAm\O was similar in the two cross-sections, which appears
$bZ5@)E to support our speculation that in the oldest age group,
| "eC0u nuclear cataract may have been less likely to be operated
5mm&l+N) than the other two types of cataract. This could have
SkU9iW(k resulted in an increased nuclear cataract prevalence (due
81)i>] to less being operated), compensated by the decreased
&uf|Le4 prevalence of cortical cataract and PSC (due to these being
\+C0Rv^^ more likely to be operated), leading to stable overall prevalence
OA[fQH#{lX of any cataract.
7De BeY Possible selection bias arising from selective survival
+.xK`_[M among persons without cataract could have led to underestimation
acj-*I of cataract prevalence in both surveys. We
M L7 vP assume that such an underestimation occurred equally in
!d95gq<=> both surveys, and thus should not have influenced our
)X8N|W>vh assessment of temporal changes.
V&lx0Dy Measurement error could also have partially contributed
(!9+QXb' to the observed difference in nuclear cataract prevalence.
H9WXp& Assessment of nuclear cataract from photographs is a
1buO&q!vn potentially subjective process that can be influenced by
-N
A2+]. variations in photography (light exposure, focus and the
]y"=/Nu-Ja slit-lamp angle when the photograph was taken) and
0*AXd=)"* grading. Although we used the same Topcon slit-lamp
]q&NO(:kbq camera and the same two graders who graded photos
R
pT7Nr from both surveys, we are still not able to exclude the possibility
&{ZUY3 of a partial influence from photographic variation
1r3}
V7 on this result.
nL[G@1nR A similar gender difference (women having a higher rate
F]s:`4 than men) in cortical cataract prevalence was observed in
Uyd' uC both surveys. Our findings are in keeping with observations
J_9[xmM from the Beaver Dam Eye Study [18], the Barbados
mo&9=TaG Eye Study [22] and the Lens Opacities Case-Control
'p[B`Ft3F Group [26]. It has been suggested that the difference
g
oJ'z|)) could be related to hormonal factors [18,22]. A previous
>G As&\4hs study on biochemical factors and cataract showed that a
CW]
Th-xc lower level of iron was associated with an increased risk of
6-+wfrN2 cortical cataract [27]. No interaction between sex and biochemical
m!]J{OGG: factors were detected and no gender difference
#G=AD
/z was assessed in this study [27]. The gender difference seen
DD`DU^o< in cortical cataract could be related to relatively low iron
^$[
iLX levels and low hemoglobin concentration usually seen in
8i)9ho< women [28]. Diabetes is a known risk factor for cortical
1X9J[5|ll Table 3: Gender distribution of cataract types in cross-sections I and II.
vb}c)w
dp? Cataract type Gender Cross-section I Cross-section II
mmy/YP) n % (95% CL)* n % (95% CL)*
.bj:tmz Cortical Male 1496 21.1 (19.0–23.1) 1328 20.4 (18.2–22.6)
=r3g:j/>q Female 1939 25.9 (23.9–27.8) 1785 26.2 (24.2–28.3)
6;;2e> e PSC Male 1500 6.5 (5.2–7.7) 1314 6.4 (5.1–7.7)
VmRfnH" Female 1944 6.2 (5.1–7.2) 1753 5.7 (4.6–6.7)
m7i(0
jd
+ Nuclear Male 1106 17.6 (15.4–19.9) 1225 22.5 (20.1–24.8)
):y^
g: Female 1395 19.5 (17.4–21.6) 1635 25.0 (22.9–27.1)
n^*,JL9@ n = number of persons
pWP1$;8 * 95% Confidence Limits
>7~,w1t BMC Ophthalmology 2006, 6:17
http://www.biomedcentral.com/1471-2415/6/17 m;
L3c(r. Page 6 of 7
)g}G{9M^ (page number not for citation purposes)
[70 5[ cataract but in this particular population diabetes is more
a2/Mf
prevalent in men than women in all age groups [29]. Differential
Gl[1K/,* exposures to cataract risk factors or different dietary
{dn:1IcN or lifestyle patterns between men and women may
H({m1v ~R also be related to these observations and warrant further
KVUub'k study.
~$hR:I1 Conclusion
k!'+7
K. In summary, in two population-based surveys 6 years
T8Q_JQ apart, we have documented a relatively stable prevalence
i
^2A:6}? of cortical cataract and PSC over the period. The observed
E&5S[n9{3 overall increased nuclear cataract prevalence by 5% over a
-Q&@P3x 6-year period needs confirmation by future studies, and
0rm(i*Q reasons for such an increase deserve further study.
TQ0ZBhd Competing interests
5
HE5$S The author(s) declare that they have no competing interests.
P ?nk> Authors' contributions
1LAd5X AGT graded the photographs, performed literature search
%d%?\jV b and wrote the first draft of the manuscript. JJW graded the
E> $_
$' photographs, critically reviewed and modified the manuscript.
lP*=4Jh ER performed the statistical analysis and critically
G6G-qqXy6 reviewed the manuscript. PM designed and directed the
65*Hf3~~ study, adjudicated cataract cases and critically reviewed
NJV kn~<
and modified the manuscript. All authors read and
P
#`M8k approved the final manuscript.
u3E =r Acknowledgements
r/"^{0;F{W This study was supported by the Australian National Health & Medical
kqxq'Aq)d Research Council, Canberra, Australia (Grant Nos 974159, 991407). The
X%kJ3
{ abstract was presented at the Association for Research in Vision and Ophthalmology
>]C/ Q6 (ARVO) meeting in Fort Lauderdale, Florida, USA, May 2005.
z;Fz3s7 References
S
Jc~E$5< 1. Congdon N, O'Colmain B, Klaver CC, Klein R, Munoz B, Friedman
>VQLC&u( DS, Kempen J, Taylor HR, Mitchell P: Causes and prevalence of
PAtv#)h visual impairment among adults in the United States. Arch
~TeOl|!lE+ Ophthalmol 2004, 122(4):477-485.
\ym^~ Q| 2. Rahmani B, Tielsch JM, Katz J, Gottsch J, Quigley H, Javitt J, Sommer
\Q1&w2mw A: The cause-specific prevalence of visual impairment in an
);6f8H@G urban population. The Baltimore Eye Survey. Ophthalmology
b-#lKWso 1996, 103:1721-1726.
"5O>egt 3. Keeffe JE, Konyama K, Taylor HR: Vision impairment in the
}#%Ye CA? Pacific region. Br J Ophthalmol 2002, 86:605-610.
z,7;+6*=L 4. Reidy A, Minassian DC, Vafidis G, Joseph J, Farrow S, Wu J, Desai P,
(Z[c7 Connolly A: Prevalence of serious eye disease and visual
%#eQN
~ impairment in a north London population: population based,
&=$f\O1Ty cross sectional study. BMJ 1998, 316:1643-1646.
_~ei1
G.R 5. Resnikoff S, Pascolini D, Etya'ale D, Kocur I, Pararajasegaram R,
'@h Pokharel GP, Mariotti SP: Global data on visual impairment in
XMT@<'fI the year 2002. Bull World Health Organ 2004, 82:844-851.
j
s"5{w& 6. Pascolini D, Mariotti SP, Pokharel GP, Pararajasegaram R, Etya'ale D,
%dq%+yw{%m Negrel AD, Resnikoff S: 2002 global update of available data on
d|7LCW+HW visual impairment: a compilation of population-based prevalence
ID!S}D studies. Ophthalmic Epidemiol 2004, 11:67-115.
e@TwZ6l 7. Rochtchina E, Mukesh BN, Wang JJ, McCarty CA, Taylor HR, Mitchell
S-Vj$asv! P: Projected prevalence of age-related cataract and cataract
3oH/34jj surgery in Australia for the years 2001 and 2021: pooled data
N[Ei%I from two population-based surveys. Clin Experiment Ophthalmol
JJSE@$",\ 2003, 31:233-236.
~9vK6;0 8. Medicare Benefits Schedule Statistics [
http://www.medicar nqUnDnP2c eaustralia.gov.au/statistics/dyn_mbs/forms/mbs_tab4.shtml]
|pWu|M _' 9. Keeffe JE, Taylor HR: Cataract surgery in Australia 1985–94.
Ddg!1SF Aust N Z J Ophthalmol 1996, 24:313-317.
X#JUorGp 10. Tan AG, Wang JJ, Rochtchina E, Jakobsen K, Mitchell P: Increase in
|Rkw/5 cataract surgery prevalence from 1992–1994 to 1997–2000:
E?P>s T3B Analysis of two population cross-sections. Clin Experiment Ophthalmol
r~f
;g9I 2004, 32:284-288.
NW`.7'aWT 11. Mitchell P, Smith W, Attebo K, Wang JJ: Prevalence of age-related
OW\vbWX maculopathy in Australia. The Blue Mountains Eye Study.
=mZYBm,I
Q Ophthalmology 1995, 102:1450-1460.
jaKW[@< 12. Mitchell P, Cumming RG, Attebo K, Panchapakesan J: Prevalence of
$`/UG0rdC cataract in Australia: the Blue Mountains eye study. Ophthalmology
;
YQB 1997, 104:581-588.
[R%*C9Y d 13. Klein BEK, Magli YL, Neider MW, Klein R: Wisconsin system for classification
)?(Ux1:
w) of cataracts from photographs (protocol) Madison, WI; 1990.
EC[]L'IL 14. Foran S, Wang JJ, Mitchell P: Causes of visual impairment in two
&;P\e older population cross-sections: the Blue Mountains Eye
js <Up/1 Study. Ophthalmic Epidemiol 2003, 10:215-225.
WH1" HO 15. Congdon N, Vingerling JR, Klein BE, West S, Friedman DS, Kempen J,
GU2TQx{V O'Colmain B, Wu SY, Taylor HR: Prevalence of cataract and
J@_^] pseudophakia/aphakia among adults in the United States.
Q*ELMib Arch Ophthalmol 2004, 122:487-494.
,
ftJw 16. Sperduto RD, Hiller R: The prevalence of nuclear, cortical, and
$9Bzq_! posterior subcapsular lens opacities in a general population
K&NH? sample. Ophthalmology 1984, 91:815-818.
1@t.J> 17. Adamsons I, Munoz B, Enger C, Taylor HR: Prevalence of lens
;NdH]a{ opacities in surgical and general populations. Arch Ophthalmol
.-tR <{
g 1991, 109:993-997.
=wDXlAQ 18. Klein BE, Klein R, Linton KL: Prevalence of age-related lens
+<F3}]] opacities in a population. The Beaver Dam Eye Study. Ophthalmology
$u~ui@kB 1992, 99:546-552.
X5J )1rL 19. West SK, Munoz B, Schein OD, Duncan DD, Rubin GS: Racial differences
L@AFt)U in lens opacities: the Salisbury Eye Evaluation (SEE)
L{F]uz_[x project. Am J Epidemiol 1998, 148:1033-1039.
9]IZ3
fQX 20. Congdon N, West SK, Buhrmann RR, Kouzis A, Munoz B, Mkocha H:
2h51zG#qd Prevalence of the different types of age-related cataract in
|au`ph5 an African population. Invest Ophthalmol Vis Sci 2001,
"ufSHrZv 42:2478-2482.
LS<+V+o2% 21. Livingston PM, Guest CS, Stanislavsky Y, Lee S, Bayley S, Walker C,
67Pmnad McKean C, Taylor HR: A population-based estimate of cataract
_p0Yhju? prevalence: the Melbourne Visual Impairment Project experience.
[=jZP,b&), Dev Ophthalmol 1994, 26:1-6.
L$OZ]
22. Leske MC, Connell AM, Wu SY, Hyman L, Schachat A: Prevalence
Y"8@\73(R of lens opacities in the Barbados Eye Study. Arch Ophthalmol
]ASw%Lw) 1997, 115:105-111. published erratum appears in Arch Ophthalmol
W1"N
Kg~4 1997 Jul;115(7):931
HLV8_~gQPf 23. Seah SK, Wong TY, Foster PJ, Ng TP, Johnson GJ: Prevalence of
A
9BoH[is7 lens opacity in Chinese residents of Singapore: the tanjong
dyn)KDS pagar survey. Ophthalmology 2002, 109:2058-2064.
*'8q?R?7g 24. Stifter E, Sacu S, Weghaupt H, Konig F, Richter-Muksch S, Thaler A,
Fik;hB Velikay-Parel M, Radner W: Reading performance depending on
RNB&!NC
the type of cataract and its predictability on the visual outcome.
61kSCu J Cataract Refract Surg 2004, 30:1259-1267.
t.;._' 25. Stifter E, Sacu S, Weghaupt H: Functional vision with cataracts of
aanS^t0 different morphologies: comparative study. J Cataract Refract
Wgte.K> / Surg 2004, 30:1883-1891.
PsNrCe%e 26. Leske MC, Chylack LT Jr, Wu SY: The Lens Opacities Case-Control
Y3[KS;_fr9 Study. Risk factors for cataract. Arch Ophthalmol 1991,
-d4v:Jab 109:244-251.
6?M/71 27. Leske MC, Wu SY, Hyman L, Sperduto R, Underwood B, Chylack LT,
=L#&`s@)_ Milton RC, Srivastava S, Ansari N: Biochemical factors in the lens
5Q8 H8!^
opacities. Case-control study. The Lens Opacities Case-Control
\v-I<":: Study Group. Arch Ophthalmol 1995, 113:1113-1119.
sv%E5@ 28. Yip R, Johnson C, Dallman PR: Age-related changes in laboratory
Sq,>^|v4&e values used in the diagnosis of anemia and iron deficiency.
FNL
S=4 Am J Clin Nutr 1984, 39:427-436.
eJ45:]_%I@ 29. Mitchell P, Smith W, Wang JJ, Cumming RG, Leeder SR, Burnett L:
}gXhN" Diabetes in an older Australian population. Diabetes Res Clin
Iv Pract 1998, 41:177-184.
&)Qq%\EP4 Pre-publication history
e'$[PF The pre-publication history for this paper can be accessed
Rf`_q7fm
here:
ZPE- Publish with BioMed Central and every
d*Mqs}8 scientist can read your work free of charge
Wm-$
l "BioMed Central will be the most significant development for
<v -YMk@ disseminating the results of biomedical research in our lifetime."
tc`3-goX Sir Paul Nurse, Cancer Research UK
n7;jME/! Your research papers will be:
b6k_u9m^E available free of charge to the entire biomedical community
;Z0&sFm peer reviewed and published immediately upon acceptance
#
lqH/>`> cited in PubMed and archived on PubMed Central
:atd_6 yours — you keep the copyright
a_S`$(7k Submit your manuscript here:
&'k(v(>n, http://www.biomedcentral.com/info/publishing_adv.asp .^=I&X/P BioMedcentral
`qmwAT BMC Ophthalmology 2006, 6:17
http://www.biomedcentral.com/1471-2415/6/17 c"kB @P
Page 7 of 7
c.LRS$o/j (page number not for citation purposes)
`.JW_F)1 http://www.biomedcentral.com/1471-2415/6/17/prepub