BioMed Central
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mP(3[a_Q BMC Ophthalmology
<AHpk5Sn{ Research article Open Access
$`=p] Comparison of age-specific cataract prevalence in two
3dShznlf_* population-based surveys 6 years apart
R$awg SE Ava Grace Tan†, Jie Jin Wang*†, Elena Rochtchina† and Paul Mitchell†
Zo9
<96I& Address: Centre for Vision Research, Westmead Millennium Institute, Department of Ophthalmology, University of Sydney, Westmead Hospital,
Kz4S6N c Westmead, NSW, Australia
29R-Up!SVN Email: Ava Grace Tan -
ava_tan@wmi.usyd.edu.au; Jie Jin Wang* -
jiejin_wang@wmi.usyd.edu.au;
90}{4&C.^ Elena Rochtchina -
elena_rochtchina@wmi.usyd.edu.au; Paul Mitchell -
paul_mitchell@wmi.usyd.edu.au N0U/u'J!g * Corresponding author †Equal contributors
wucdXj{% Abstract
cPGlT" Background: In this study, we aimed to compare age-specific cortical, nuclear and posterior
15$xa_w}L
subcapsular (PSC) cataract prevalence in two surveys 6 years apart.
(}"D x3K Methods: The Blue Mountains Eye Study examined 3654 participants (82.4% of those eligible) in
s:`i~hjq cross-section I (1992–4) and 3509 participants (75.1% of survivors and 85.2% of newly eligible) in
H#-3 cross-section II (1997–2000, 66.5% overlap with cross-section I). Cataract was assessed from lens
Z
O}Og&% photographs following the Wisconsin Cataract Grading System. Cortical cataract was defined if
3:%k
pnO cortical opacity comprised ≥ 5% of lens area. Nuclear cataract was defined if nuclear opacity ≥
@u3`lhUcT Wisconsin standard 4. PSC was defined if any present. Any cataract was defined to include persons
.u`[|:K who had previous cataract surgery. Weighted kappa for inter-grader reliability was 0.82, 0.55 and
2pS<;k` 0.82 for cortical, nuclear and PSC cataract, respectively. We assessed age-specific prevalence using
LzygupxY! an interval of 5 years, so that participants within each age group were independent between the
OfsP5*d two surveys.
o3ZN0j69| Results: Age and gender distributions were similar between the two populations. The age-specific
]AP1+
&9fN prevalence of cortical (23.8% in 1st, 23.7% in 2nd) and PSC cataract (6.3%, 6.0%) was similar. The
Zw]`z*,yRA prevalence of nuclear cataract increased slightly from 18.7% to 23.9%. After age standardization,
$o6/dEKQ the similar prevalence of cortical (23.8%, 23.5%) and PSC cataract (6.3%, 5.9%), and the increased
IS C.~q2 prevalence of nuclear cataract (18.7%, 24.2%) remained.
BT_]=
\zi Conclusion: In two surveys of two population-based samples with similar age and gender
TyxIlI4" distributions, we found a relatively stable cortical and PSC cataract prevalence over a 6-year period.
vccWe7rh The increased prevalence of nuclear cataract deserves further study.
!`ol&QQ# Background
_iwG'a[` Age-related cataract is the leading cause of reversible visual
jA? #!lx_ impairment in older persons [1-6]. In Australia, it is
T.q2tC[bR estimated that by the year 2021, the number of people
fV:15!S[ affected by cataract will increase by 63%, due to population
pA7-B>Y aging [7]. Surgical intervention is an effective treatment
PN}+LOD<t for cataract and normal vision (> 20/40) can usually
vwR_2u be restored with intraocular lens (IOL) implantation.
$QX$r N Cataract surgery with IOL implantation is currently the
dQut8>0& most commonly performed, and is, arguably, the most
|5@Ra@0 cost effective surgical procedure worldwide. Performance
,|%KlHo^ Published: 20 April 2006
G1:}{a5i_ BMC Ophthalmology 2006, 6:17 doi:10.1186/1471-2415-6-17
D?|D)"?qb Received: 14 December 2005
[hJ1]RW8 Accepted: 20 April 2006
/iW+<@Mas This article is available from:
http://www.biomedcentral.com/1471-2415/6/17 r}U6LE?> © 2006 Tan et al; licensee BioMed Central Ltd.
M!mL/*G@YE This is an Open Access article distributed under the terms of the Creative Commons Attribution License (
http://creativecommons.org/licenses/by/2.0),
'Kelq$dn# which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
_S!^=9bJ BMC Ophthalmology 2006, 6:17
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&lc@]y8 (page number not for citation purposes)
X<ex
>sM of this surgical procedure has been continuously increasing
N,t9X7G& in the last two decades. Data from the Australian
F)P:lvp<r Health Insurance Commission has shown a steady
o'Bd. B increase in Medicare claims for cataract surgery [8]. A 2.6-
1nVQYqT_ fold increase in the total number of cataract procedures
Po>6I0y from 1985 to 1994 has been documented in Australia [9].
t@KTiJI
] The rate of cataract surgery per thousand persons aged 65
oRfb4+H& years or older has doubled in the last 20 years [8,9]. In the
g 2Fg Blue Mountains Eye Study population, we observed a onethird
;H$Cq'
I increase in cataract surgery prevalence over a mean
cIug~ x> 6-year interval, from 6% to nearly 8% in two cross-sectional
&9jJ\+:7 population-based samples with a similar age range
X[z;P!U [10]. Further increases in cataract surgery performance
}gSoBu would be expected as a result of improved surgical skills
pEB3qGA and technique, together with extending cataract surgical
ra^</o/
benefits to a greater number of older people and an
_KRnx- increased number of persons with surgery performed on
e9acI>^w both eyes.
s>9I#_4] Both the prevalence and incidence of age-related cataract
K^{j$ link directly to the demand for, and the outcome of, cataract
01Jav~WR surgery and eye health care provision. This report
'!>9j,BJ aimed to assess temporal changes in the prevalence of cortical
%Tp9GGt and nuclear cataract and posterior subcapsular cataract
vbJ<|#|r- (PSC) in two cross-sectional population-based
81RuNs] surveys 6 years apart.
}$?
FR Methods
,~L*N*ML
The Blue Mountains Eye Study (BMES) is a populationbased
l@Lk+-[D cohort study of common eye diseases and other
iBE|6+g~Cj health outcomes. The study involved eligible permanent
piIZ*@' residents aged 49 years and older, living in two postcode
St
;9&A areas in the Blue Mountains, west of Sydney, Australia.
+;,{`*W+N Participants were identified through a census and were
LM<*VhX invited to participate. The study was approved at each
4'faE="1)S stage of the data collection by the Human Ethics Committees
s:<y\1Ay of the University of Sydney and the Western Sydney
;&lXgC^* Area Health Service and adhered to the recommendations
(4Db%Iw of the Declaration of Helsinki. Written informed consent
hu-]SGb6 was obtained from each participant.
Zl_sbIY Details of the methods used in this study have been
~#gc{C@ described previously [11]. The baseline examinations
8] LF{Obz[ (BMES cross-section I) were conducted during 1992–
CXUF=IE 1994 and included 3654 (82.4%) of 4433 eligible residents.
S1k*">< Follow-up examinations (BMES IIA) were conducted
m.P
F'_)/ during 1997–1999, with 2335 (75.0% of BMES
u`EK^\R cross section I survivors) participating. A repeat census of
uNewWtUb( the same area was performed in 1999 and identified 1378
'
!huU newly eligible residents who moved into the area or the
t{,$?} eligible age group. During 1999–2000, 1174 (85.2%) of
-cUW,>E this group participated in an extension study (BMES IIB).
JKKp5~_~ BMES cross-section II thus includes BMES IIA (66.5%)
4=MVn and BMES IIB (33.5%) participants (n = 3509).
I
N
@ ~~ Similar procedures were used for all stages of data collection
J^t0M\ at both surveys. A questionnaire was administered
fq1w <e including demographic, family and medical history. A
zt2#K detailed eye examination included subjective refraction,
wgDA
b#Zuk slit-lamp (Topcon SL-7e camera, Topcon Optical Co,
'"Cqq{* Tokyo, Japan) and retroillumination (Neitz CT-R camera,
j gV^{8qG Neitz Instrument Co, Tokyo, Japan) photography of the
[1~3\-Y lens. Grading of lens photographs in the BMES has been
|
{zka.sJ
previously described [12]. Briefly, masked grading was
0gyvRM@ x[ performed on the lens photographs using the Wisconsin
4JBfA, Cataract Grading System [13]. Cortical cataract and PSC
/&?ei*z were assessed from the retroillumination photographs by
~#EXb?#uS estimating the percentage of the circular grid involved.
D _\HX9 Cortical cataract was defined when cortical opacity
K[SzE{5=P involved at least 5% of the total lens area. PSC was defined
zCq6k7u when opacity comprised at least 1% of the total lens area.
7d{xXJ- Slit-lamp photographs were used to assess nuclear cataract
=PU@'OG using the Wisconsin standard set of four lens photographs
57 Vn- [13]. Nuclear cataract was defined when nuclear opacity
h1)+QLI was at least as great as the standard 4 photograph. Any cataract
q89yW)XG was defined to include persons who had previous
vr>J$
(F cataract surgery as well as those with any of three cataract
j%vxCs> types. Inter-grader reliability was high, with weighted
M/[9ZgDc kappa 0.82 for cortical cataract, 0.55 (simple kappa 0.75)
?`
*`A9@ for nuclear cataract and 0.82 for PSC grading. The intragrader
/|Gz<nSc reliability for nuclear cataract was assessed with
B_r:da CS: simple kappa 0.83 for the senior grader who graded
#.j:P# nuclear cataract at both surveys. All PSC cases were confirmed
Rlr[uU_ by an ophthalmologist (PM).
.<P@6Jq In cross-section I, 219 persons (6.0%) had missing or
[woxCfSA ungradable Neitz photographs, leaving 3435 with photographs
'u[cT$ available for cortical cataract and PSC assessment,
RvW>kATb_F while 1153 (31.6%) had randomly missing or ungradable
5o|u!#6 Topcon photographs due to a camera malfunction, leaving
7
dG_E]& 2501 with photographs available for nuclear cataract
Dx3Sf}G
` assessment. Comparison of characteristics between participants
t/"9LMKs? with and without Neitz or Topcon photographs in
w68VOymD/ cross-section I showed no statistically significant differences
RML'C
:1 between the two groups, as reported previously
z
:$TW{%M [12]. In cross-section II, 441 persons (12.5%) had missing
YAF0I%PYU or ungradable Neitz photographs, leaving 3068 for cortical
K)oN^ cataract and PSC assessment, and 648 (18.5%) had
%8L5uMx missing or ungradable Topcon photographs, leaving 2860
RA62Z&W3 for nuclear cataract assessment.
7w"YCRKh Data analysis was performed using the Statistical Analysis
XN'X&J System (SAS, SAS Institute, Cary, NC, USA). Age-adjusted
#lm1"~`5 prevalence was calculated using direct standardization of
j@s,5:;[ the cross-section II population to the cross-section I population.
1<9m^9_ro We assessed age-specific prevalence using an
p&\x*~6u interval of 5 years, so that participants within each age
2|^bDg;W+u group were independent between the two cross-sectional
w3IU'(|G surveys.
o;:a6D`
BMC Ophthalmology 2006, 6:17
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CD0SXNi"zH Results
Ec]cC
LB Characteristics of the two survey populations have been
g'b)] Q previously compared [14] and showed that age and sex
dTP$7nfe distributions were similar. Table 1 compares participant
`Uw^,r characteristics between the two cross-sections. Cross-section
bsmnh_YRj II participants generally had higher rates of diabetes,
(iiyptJ hypertension, myopia and more users of inhaled steroids.
4d3PF`,H` Cataract prevalence rates in cross-sections I and II are
]urcA,a shown in Figure 1. The overall prevalence of cortical cataract
[w)6OT was 23.8% and 23.7% in cross-sections I and II,
Z)(C7,Xu respectively (age-sex adjusted P = 0.81). Corresponding
G>{;@u prevalence of PSC was 6.3% and 6.0% for the two crosssections
.,x08M
(age-sex adjusted P = 0.60). There was an
@ B3@M increased prevalence of nuclear cataract, from 18.7% in
: C;=<$ cross-section I to 23.9% in cross-section II over the 6-year
ziy~~J period (age-sex adjusted P < 0.001). Prevalence of any cataract
Oox5${#^ (including persons who had cataract surgery), however,
4 ITSDx was relatively stable (46.9% and 46.8% in crosssections
1}!f.cWV( I and II, respectively).
(N43?i
v( After age-standardization, these prevalence rates remained
$0K9OF9$ stable for cortical cataract (23.8% and 23.5% in the two
crC];LMl/ surveys) and PSC (6.3% and 5.9%). The slightly increased
c{#lKD<7 prevalence of nuclear cataract (from 18.7% to 24.2%) was
Xf9VW}`*8 not altered.
$X-,6* Table 2 shows the age-specific prevalence rates for cortical
;LH?Qu;e cataract, PSC and nuclear cataract in cross-sections I and
8F4#E
U II. A similar trend of increasing cataract prevalence with
)r1Z}X(#d increasing age was evident for all three types of cataract in
P5vM y'1X both surveys. Comparing the age-specific prevalence
8N8B${X between the two surveys, a reduction in PSC prevalence in
JCaT^KLz cross-section II was observed in the older age groups (≥ 75
^#%$?w>wI years). In contrast, increased nuclear cataract prevalence
0 x"3 in cross-section II was observed in the older age groups (≥
P/Sv^d5=e 70 years). Age-specific cortical cataract prevalence was relatively
|2c '0Ibu consistent between the two surveys, except for a
o *I-~k reduction in prevalence observed in the 80–84 age group
F/RV{} 17E and an increasing prevalence in the older age groups (≥ 85
}
"y{d@ years).
rxCuV Similar gender differences in cataract prevalence were
l=
!KZaH observed in both surveys (Table 3). Higher prevalence of
~"}-cl, cortical and nuclear cataract in women than men was evident
R^_/iy but the difference was only significant for cortical
bEy j8=P; cataract (age-adjusted odds ratio, OR, for women 1.3,
p#J}@a 95% confidence intervals, CI, 1.1–1.5 in cross-section I
g4j?E{M? and OR 1.4, 95% CI 1.1–1.6 in cross-section II). In con-
2f I?P Table 1: Participant characteristics.
eyl+D sK Characteristics Cross-section I Cross-section II
uj;-HN)6 n % n %
@oug^]a Age (mean) (66.2) (66.7)
MWsBZJRr 50–54 485 13.3 350 10.0
+~02j1Jx 55–59 534 14.6 580 16.5
CQzJ_aSJ( 60–64 638 17.5 600 17.1
0P\)L`cG 65–69 671 18.4 639 18.2
0 Co_," 70–74 538 14.7 572 16.3
VwHTtZ 75–79 422 11.6 407 11.6
2Wq)y1R<T 80–84 230 6.3 226 6.4
m/%sBw\rx 85–89 100 2.7 110 3.1
RP z0WP 90+ 36 1.0 24 0.7
)5)S8~Oc Female 2072 56.7 1998 57.0
gn#4az3@e> Ever Smokers 1784 51.2 1789 51.2
,S}[48$ Use of inhaled steroids 370 10.94 478 13.8^
UFm E`|le History of:
TQ.d|{B[ Diabetes 284 7.8 347 9.9^
?7/n s>} Hypertension 1669 46.0 1825 52.2^
"f(iQI Emmetropia* 1558 42.9 1478 42.2
q
A#!3< Myopia* 442 12.2 495 14.1^
#:w/vk Hyperopia* 1633 45.0 1532 43.7
XQ%*U=)s n = number of persons affected
dBX%/ * best spherical equivalent refraction correction
D%Hz'G0| ^ P < 0.01
DU4NPys]y BMC Ophthalmology 2006, 6:17
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,X)0+DNsq (page number not for citation purposes)
g(>;Z@Y
t
=sPY+~<o rast, men had slightly higher PSC prevalence than women
C5\bnk{ in both cross-sections but the difference was not significant
+kd88Fx (OR 1.1, 95% CI 0.8–1.4 for men in cross-section I
_}EGk4E and OR 1.2, 95% 0.9–1.6 in cross-section II).
_hMMm6a| Discussion
e 9U\48 Findings from two surveys of BMES cross-sectional populations
LwZBM#_g with similar age and gender distribution showed
5qGRz"\p~ that the prevalence of cortical cataract and PSC remained
,i;kAy) stable, while the prevalence of nuclear cataract appeared
c_)vWU to have increased. Comparison of age-specific prevalence,
bBW(#
Q_a with totally independent samples within each age group,
iKu[j)F confirmed the robustness of our findings from the two
M6jP>fbV* survey samples. Although lens photographs taken from
z%Op_Ddp the two surveys were graded for nuclear cataract by the
tV9BVsN same graders, who documented a high inter- and intragrader
B)Hs>Mh|W reliability, we cannot exclude the possibility that
E%:!* 9 variations in photography, performed by different photographers,
Vrf2%$g may have contributed to the observed difference
#?k$0|60 in nuclear cataract prevalence. However, the overall
HIcx "y Table 2: Age-specific prevalence of cataract types in cross sections I and II.
U59uP
7n Cataract type Age (years) Cross-section I Cross-section II
&n|#jo(gS n % (95% CL)* n % (95% CL)*
/tikLJ Cortical 50–54 473 4.4 (2.6–6.3) 338 7.4 (4.6–10.2)
yK+76\} I 55–59 522 9.2 (6.7–11.7) 542 9.0 (6.6–11.5)
t48(, 60–64 615 16.4 (13.5–19.4) 556 16.7 (13.6–19.8)
!u.{<51b
65–69 653 26.2 (22.8–29.6) 581 23.6 (20.1–27.0)
?D/r1%Z 70–74 516 31.2 (27.2–35.2) 514 35.4 (31.3–39.6)
h6}oRz9=g 75–79 366 40.2 (35.1–45.2) 332 39.8 (34.5–45.1)
E
j@M\ 80–84 194 58.8 (51.8–65.8) 163 42.9 (35.3–50.6)
S
U~vS 85–89 74 52.7 (41.1–64.4) 73 54.8 (43.1–66.5)
[CGvM{ 90+ 22 68.2 (47.0–89.3) 14 78.6 (54.0–103.2)
/7De.O~H PSC 50–54 474 2.7 (1.3–4.2) 338 2.4 (0.7–4.0)
DKqFe5rw 55–59 522 2.9 (1.4–4.3) 541 2.6 (1.3–3.9)
.r)WDR 60–64 616 4.6 (2.9–6.2) 548 5.7 (3.7–7.6)
6*Qn9Q%p- 65–69 655 6.3 (4.4–8.1) 573 4.5 (2.8–6.3)
NDglse 70–74 517 6.8 (4.6–8.9) 505 9.7 (7.1–12.3)
c5>&~^~>Tx 75–79 367 11.4 (8.2–14.7) 327 9.5 (6.3–12.7)
s/0-DHd 80–84 196 12.2 (7.6–16.9) 155 10.3 (5.5–15.2)
`W
e M 85–89 74 18.9 (9.8–28.1) 69 11.6 (3.9–19.4)
lb2mWsg" 90+ 23 21.7 (3.5–40.0) 11 0.0
O?p.kf{b Nuclear 50–54 323 1.6 (0.2–2.9) 331 0.9 (–0.2–1.9)
=L{lt9qQz 55–59 386 2.3 (0.8–3.8) 507 3.6 (1.9–5.2)
#dE#w#=r 60–64 453 5.3 (3.2–7.4) 501 11.6 (8.8–14.4)
TKvUBy 65–69 478 17.2 (13.8–20.1) 534 18.5 (15.2–21.9)
zNuiBLxDs 70–74 392 27.6 (23.1–32.0) 453 36.0 (31.6–40.4)
%gSqc
}v* 75–79 255 45.1 (39.0–51.3) 302 55.6 (50.0–61.3)
FjRJSMwO, 80–84 146 54.1 (45.9–62.3) 147 73.5 (66.3–80.7)
8Y3c,p/gS> 85–89 50 64.0 (50.2–77.8) 70 80.0 (70.4–89.6)
`0uKJFg 90+ 18 72.2 (49.3–95.1) 15 73.3 (48.0–98.7)
H@bra~k- n = number of persons
kEf}yTy * 95% Confidence Limits
`sQ\j Nu Cataract FMioguunrtea i1n ps rEeyvea lSetnucdey in cross-sections I and II of the Blue
-`n>q^A7e Cataract prevalence in cross-sections I and II of the Blue
E^zgYkZO Mountains Eye Study.
p<Wb^BE 0
kXzm 10
B]ul~FX 20
J:dF^3Y 30
8jd<|nYnfc 40
xyj)W 50
A@bWlwfl cortical PSC nuclear any
&{9'ylv-B) cataract
l
" pCxA Cataract type
0{F"b'h %
Jy@cMq2 Cross-section I
FXV=D_G} Cross-section II
@k<RX'~q BMC Ophthalmology 2006, 6:17
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+ L;[-]E8 (page number not for citation purposes)
q~p,A>K prevalence of any cataract (including cataract surgery) was
zwR@^ 5^6 relatively stable over the 6-year period.
D;Fvd: Although different population-based studies used different
V]L$`7G grading systems to assess cataract [15], the overall
-b~MQ/,2 prevalence of the three cataract types were similar across
%}%D8-d}G different study populations [12,16-23]. Most studies have
fU@}]& suggested that nuclear cataract is the most prevalent type
Jc~^32 of cataract, followed by cortical cataract [16-20]. Ours and
b5Rjn1@ other studies reported that cortical cataract was the most
1)?^N`xF prevalent type [12,21-23].
@I\
Z2-J Our age-specific prevalence data show a reduction of
{.bLh0 15.9% in cortical cataract prevalence for the 80–84 year
"8ILV`[ age group, concordant with an increase in cataract surgery
%2^C prevalence by 9% in those aged 80+ years observed in the
-))>7skc same study population [10]. Although cortical cataract is
iN*d84KTP thought to be the least likely cataract type leading to a cataract
U(-9xp+ surgery, this may not be the case in all older persons.
tirw{[X0n A relatively stable cortical cataract and PSC prevalence
V:6#IL over the 6-year period is expected. We cannot offer a
KD$ P\(5# definitive explanation for the increase in nuclear cataract
7
tF1g=\ prevalence. A possible explanation could be that a moderate
aBr%"&Z.MG level of nuclear cataract causes less visual disturbance
idGkX
? than the other two types of cataract, thus for the oldest age
6ecr]=Cv groups, persons with nuclear cataract could have been less
^4Tr
@g#]" likely to have surgery unless it is very dense or co-existing
tH5f;mY, with cortical cataract or PSC. Previous studies have shown
$LAaG65V that functional vision and reading performance were high
wC!(STu
in patients undergoing cataract surgery who had nuclear
174H@ cataract only compared to those with mixed type of cataract
miuJ!Kr' (nuclear and cortical) or PSC [24,25]. In addition, the
q]<Xx{_ overall prevalence of any cataract (including cataract surgery)
g0rdF was similar in the two cross-sections, which appears
3=t}py7M to support our speculation that in the oldest age group,
k:7UU4M
5 nuclear cataract may have been less likely to be operated
(z2)<_bXJ than the other two types of cataract. This could have
GK95=?f~8; resulted in an increased nuclear cataract prevalence (due
RduA0@g0 to less being operated), compensated by the decreased
)#ic"UtR prevalence of cortical cataract and PSC (due to these being
)K@ 20Q+0K more likely to be operated), leading to stable overall prevalence
RK'3b/T of any cataract.
s]L`&fY]O Possible selection bias arising from selective survival
BTjF^&` among persons without cataract could have led to underestimation
3(^9K2.s} of cataract prevalence in both surveys. We
&HFMF
)NA assume that such an underestimation occurred equally in
T]Tz<w W( both surveys, and thus should not have influenced our
:U?P~HI assessment of temporal changes.
&9o @x]) @ Measurement error could also have partially contributed
SjlkKulMF to the observed difference in nuclear cataract prevalence.
Mk@ _uPm Assessment of nuclear cataract from photographs is a
,"h$!k"$g potentially subjective process that can be influenced by
deHBY4@ variations in photography (light exposure, focus and the
5? c4aAn slit-lamp angle when the photograph was taken) and
5 Nl>4d` grading. Although we used the same Topcon slit-lamp
hJFQ/(
camera and the same two graders who graded photos
bnD>/z]E from both surveys, we are still not able to exclude the possibility
F{l,Tl"Jw of a partial influence from photographic variation
$|(roC( on this result.
gP/]05$e A similar gender difference (women having a higher rate
*ZN"+wf\ than men) in cortical cataract prevalence was observed in
EVb'x Zr both surveys. Our findings are in keeping with observations
kZz;l(?0 from the Beaver Dam Eye Study [18], the Barbados
c?q#?K
aF Eye Study [22] and the Lens Opacities Case-Control
z W+wtYV4 Group [26]. It has been suggested that the difference
O "{o
( could be related to hormonal factors [18,22]. A previous
4`Fbl]Q study on biochemical factors and cataract showed that a
'J!P:.=a> lower level of iron was associated with an increased risk of
1ed#nB% cortical cataract [27]. No interaction between sex and biochemical
^gb2=gWZ< factors were detected and no gender difference
v+Mt/8 was assessed in this study [27]. The gender difference seen
cG"jrQ in cortical cataract could be related to relatively low iron
A
\4Gq levels and low hemoglobin concentration usually seen in
*l7
ojv women [28]. Diabetes is a known risk factor for cortical
0CTI=<; Table 3: Gender distribution of cataract types in cross-sections I and II.
g@nE7H1V Cataract type Gender Cross-section I Cross-section II
Yq1 ~"he8 n % (95% CL)* n % (95% CL)*
.'X$SF` Cortical Male 1496 21.1 (19.0–23.1) 1328 20.4 (18.2–22.6)
4=q\CK2 ^A Female 1939 25.9 (23.9–27.8) 1785 26.2 (24.2–28.3)
xss D2*
l PSC Male 1500 6.5 (5.2–7.7) 1314 6.4 (5.1–7.7)
-O(.J'=8 Female 1944 6.2 (5.1–7.2) 1753 5.7 (4.6–6.7)
q=96Ci _a Nuclear Male 1106 17.6 (15.4–19.9) 1225 22.5 (20.1–24.8)
eQC`e#% Female 1395 19.5 (17.4–21.6) 1635 25.0 (22.9–27.1)
_Z8zD[l n = number of persons
C
#TS * 95% Confidence Limits
zH|!O!3"4 BMC Ophthalmology 2006, 6:17
http://www.biomedcentral.com/1471-2415/6/17 JNMZn/ Page 6 of 7
gVZ~OcB!W (page number not for citation purposes)
s
\kkD* cataract but in this particular population diabetes is more
:T'"%_d5 prevalent in men than women in all age groups [29]. Differential
T}4RlIZF exposures to cataract risk factors or different dietary
lIOLR-:4j or lifestyle patterns between men and women may
:L\@+}{(c also be related to these observations and warrant further
6.K)uQgjmv study.
B d\p!f< Conclusion
L0uN|?} In summary, in two population-based surveys 6 years
FQ O6w' apart, we have documented a relatively stable prevalence
eb+[=nmP of cortical cataract and PSC over the period. The observed
L*L3;y| overall increased nuclear cataract prevalence by 5% over a
6'*?zZrz 6-year period needs confirmation by future studies, and
501|Y6ptl reasons for such an increase deserve further study.
u^:!!Suo Competing interests
QF\NHV The author(s) declare that they have no competing interests.
srC'!I=s>8 Authors' contributions
TQnMPELh" AGT graded the photographs, performed literature search
^*R
r x and wrote the first draft of the manuscript. JJW graded the
mtJI#P photographs, critically reviewed and modified the manuscript.
qFvtqv2 ER performed the statistical analysis and critically
}HXNhv-K reviewed the manuscript. PM designed and directed the
/<y-pFTg study, adjudicated cataract cases and critically reviewed
sFB; /*C and modified the manuscript. All authors read and
J^1w& 40 approved the final manuscript.
pspV~9, Acknowledgements
V&NOp This study was supported by the Australian National Health & Medical
>mh:OJH45 Research Council, Canberra, Australia (Grant Nos 974159, 991407). The
(wvDiW5 abstract was presented at the Association for Research in Vision and Ophthalmology
[\.
ho9 (ARVO) meeting in Fort Lauderdale, Florida, USA, May 2005.
TQbhK^] References
U7
Z_ 1. Congdon N, O'Colmain B, Klaver CC, Klein R, Munoz B, Friedman
knF *~O :y DS, Kempen J, Taylor HR, Mitchell P: Causes and prevalence of
Vk>aU3\c visual impairment among adults in the United States. Arch
*crpM3fO> Ophthalmol 2004, 122(4):477-485.
QbpRSdxy`$ 2. Rahmani B, Tielsch JM, Katz J, Gottsch J, Quigley H, Javitt J, Sommer
K+Ehj(eF A: The cause-specific prevalence of visual impairment in an
N6yqA)z?; urban population. The Baltimore Eye Survey. Ophthalmology
G4AX8@;U 1996, 103:1721-1726.
;>|:I(l; 3. Keeffe JE, Konyama K, Taylor HR: Vision impairment in the
f{5)yZ`J* Pacific region. Br J Ophthalmol 2002, 86:605-610.
2{**bArV 4. Reidy A, Minassian DC, Vafidis G, Joseph J, Farrow S, Wu J, Desai P,
g2 4)GjDi Connolly A: Prevalence of serious eye disease and visual
sDWX} NV impairment in a north London population: population based,
=s1"<hH}O) cross sectional study. BMJ 1998, 316:1643-1646.
Wc03Sv&FZ 5. Resnikoff S, Pascolini D, Etya'ale D, Kocur I, Pararajasegaram R,
hGD7/qTN Pokharel GP, Mariotti SP: Global data on visual impairment in
+<@7x16 the year 2002. Bull World Health Organ 2004, 82:844-851.
Qn<J@% 6. Pascolini D, Mariotti SP, Pokharel GP, Pararajasegaram R, Etya'ale D,
Vx-HW;, Negrel AD, Resnikoff S: 2002 global update of available data on
b*r1Jn"h visual impairment: a compilation of population-based prevalence
fd*=`+P studies. Ophthalmic Epidemiol 2004, 11:67-115.
<k}>eGn 7. Rochtchina E, Mukesh BN, Wang JJ, McCarty CA, Taylor HR, Mitchell
kw|bEL9!u P: Projected prevalence of age-related cataract and cataract
<}N0y*m surgery in Australia for the years 2001 and 2021: pooled data
L=4?vs from two population-based surveys. Clin Experiment Ophthalmol
j08|zUe 2003, 31:233-236.
pg*'2AT 8. Medicare Benefits Schedule Statistics [
http://www.medicar LDr!d1A eaustralia.gov.au/statistics/dyn_mbs/forms/mbs_tab4.shtml]
BeaX 0#\ 9. Keeffe JE, Taylor HR: Cataract surgery in Australia 1985–94.
+z;xl-*[ Aust N Z J Ophthalmol 1996, 24:313-317.
k
s
sXi6^ 10. Tan AG, Wang JJ, Rochtchina E, Jakobsen K, Mitchell P: Increase in
SM![ yC cataract surgery prevalence from 1992–1994 to 1997–2000:
09%q/-$ Analysis of two population cross-sections. Clin Experiment Ophthalmol
Z(*nZT, 2004, 32:284-288.
HSp*lHU 11. Mitchell P, Smith W, Attebo K, Wang JJ: Prevalence of age-related
@l>\vs< maculopathy in Australia. The Blue Mountains Eye Study.
fZxZ):7i Ophthalmology 1995, 102:1450-1460.
9%kY8#%SV 12. Mitchell P, Cumming RG, Attebo K, Panchapakesan J: Prevalence of
^*%p]r cataract in Australia: the Blue Mountains eye study. Ophthalmology
w*#TS8
\ 1997, 104:581-588.
xgsD<3 13. Klein BEK, Magli YL, Neider MW, Klein R: Wisconsin system for classification
6<sB of cataracts from photographs (protocol) Madison, WI; 1990.
>UWLT;N/W 14. Foran S, Wang JJ, Mitchell P: Causes of visual impairment in two
burEo.= older population cross-sections: the Blue Mountains Eye
wC'KI8- Study. Ophthalmic Epidemiol 2003, 10:215-225.
sB-c'`,w` 15. Congdon N, Vingerling JR, Klein BE, West S, Friedman DS, Kempen J,
=u${2= O'Colmain B, Wu SY, Taylor HR: Prevalence of cataract and
8y~
Jn~t pseudophakia/aphakia among adults in the United States.
.;iXe Arch Ophthalmol 2004, 122:487-494.
' OdZ[AN 16. Sperduto RD, Hiller R: The prevalence of nuclear, cortical, and
PIB|&I|p posterior subcapsular lens opacities in a general population
u0w2v+ sample. Ophthalmology 1984, 91:815-818.
m*CIbkDsZ 17. Adamsons I, Munoz B, Enger C, Taylor HR: Prevalence of lens
G*\wu&7! opacities in surgical and general populations. Arch Ophthalmol
A<y3Tc?Q 1991, 109:993-997.
W4|1wd}.t 18. Klein BE, Klein R, Linton KL: Prevalence of age-related lens
8[(c'rl|)| opacities in a population. The Beaver Dam Eye Study. Ophthalmology
X[h=UlF 1992, 99:546-552.
6"-LGK: 19. West SK, Munoz B, Schein OD, Duncan DD, Rubin GS: Racial differences
[3t
N-aj
[ in lens opacities: the Salisbury Eye Evaluation (SEE)
)&se/x+ project. Am J Epidemiol 1998, 148:1033-1039.
C&zgt
:q6} 20. Congdon N, West SK, Buhrmann RR, Kouzis A, Munoz B, Mkocha H:
f ,K1 a9. Prevalence of the different types of age-related cataract in
R:0Fv9bwS an African population. Invest Ophthalmol Vis Sci 2001,
e0(loWq] 42:2478-2482.
Rk2ZdNc\ 21. Livingston PM, Guest CS, Stanislavsky Y, Lee S, Bayley S, Walker C,
ehOF@IA_ McKean C, Taylor HR: A population-based estimate of cataract
zu*0uL prevalence: the Melbourne Visual Impairment Project experience.
Q(oWaG Dev Ophthalmol 1994, 26:1-6.
fG0rUi(8 22. Leske MC, Connell AM, Wu SY, Hyman L, Schachat A: Prevalence
cV&(L]k>` of lens opacities in the Barbados Eye Study. Arch Ophthalmol
:*1|ERGoay 1997, 115:105-111. published erratum appears in Arch Ophthalmol
g3e\'B' 1997 Jul;115(7):931
0N_Ma')i 23. Seah SK, Wong TY, Foster PJ, Ng TP, Johnson GJ: Prevalence of
azF"tke lens opacity in Chinese residents of Singapore: the tanjong
wV W+~DJ pagar survey. Ophthalmology 2002, 109:2058-2064.
W{=>c/ 24. Stifter E, Sacu S, Weghaupt H, Konig F, Richter-Muksch S, Thaler A,
O0WzDD
Velikay-Parel M, Radner W: Reading performance depending on
qGl+KI the type of cataract and its predictability on the visual outcome.
XHlPjw J Cataract Refract Surg 2004, 30:1259-1267.
n KDX=73 25. Stifter E, Sacu S, Weghaupt H: Functional vision with cataracts of
|+cyb<(V J different morphologies: comparative study. J Cataract Refract
\hv*`ukF Surg 2004, 30:1883-1891.
>6r&VZu*n 26. Leske MC, Chylack LT Jr, Wu SY: The Lens Opacities Case-Control
)nQpO"+M Study. Risk factors for cataract. Arch Ophthalmol 1991,
"%qGcC8 109:244-251.
e,`+6qP{ 27. Leske MC, Wu SY, Hyman L, Sperduto R, Underwood B, Chylack LT,
6>Lr Milton RC, Srivastava S, Ansari N: Biochemical factors in the lens
g2 :^Z== opacities. Case-control study. The Lens Opacities Case-Control
Kdik7jL/J Study Group. Arch Ophthalmol 1995, 113:1113-1119.
)h2wwq0] 28. Yip R, Johnson C, Dallman PR: Age-related changes in laboratory
S
7E
:&E& values used in the diagnosis of anemia and iron deficiency.
Q4CxtY Am J Clin Nutr 1984, 39:427-436.
*1Nz
VV 29. Mitchell P, Smith W, Wang JJ, Cumming RG, Leeder SR, Burnett L:
pYceMZ$ Diabetes in an older Australian population. Diabetes Res Clin
i,<TaW*I Pract 1998, 41:177-184.
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