BioMed Central
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V BMC Ophthalmology
u.xnO cOH! Research article Open Access
Z"fJ`-- Comparison of age-specific cataract prevalence in two
^Xh^xL2cn population-based surveys 6 years apart
C1 *v,i Ava Grace Tan†, Jie Jin Wang*†, Elena Rochtchina† and Paul Mitchell†
1/J=uH Address: Centre for Vision Research, Westmead Millennium Institute, Department of Ophthalmology, University of Sydney, Westmead Hospital,
I9ep`X6Y Westmead, NSW, Australia
Qq|57X)P* Email: Ava Grace Tan -
ava_tan@wmi.usyd.edu.au; Jie Jin Wang* -
jiejin_wang@wmi.usyd.edu.au;
Oxd]y1 Elena Rochtchina -
elena_rochtchina@wmi.usyd.edu.au; Paul Mitchell -
paul_mitchell@wmi.usyd.edu.au -6B4sZpzD * Corresponding author †Equal contributors
7J<5f) Abstract
P\k#
>}} Background: In this study, we aimed to compare age-specific cortical, nuclear and posterior
oYH-wQ j subcapsular (PSC) cataract prevalence in two surveys 6 years apart.
DN:EB@ Methods: The Blue Mountains Eye Study examined 3654 participants (82.4% of those eligible) in
XZd,&YiaG cross-section I (1992–4) and 3509 participants (75.1% of survivors and 85.2% of newly eligible) in
?.BC#S)q1 cross-section II (1997–2000, 66.5% overlap with cross-section I). Cataract was assessed from lens
oXF.1f/h photographs following the Wisconsin Cataract Grading System. Cortical cataract was defined if
}&D32\ cortical opacity comprised ≥ 5% of lens area. Nuclear cataract was defined if nuclear opacity ≥
A~70 Wisconsin standard 4. PSC was defined if any present. Any cataract was defined to include persons
h~zT ydnH who had previous cataract surgery. Weighted kappa for inter-grader reliability was 0.82, 0.55 and
-(H0>Ap 0.82 for cortical, nuclear and PSC cataract, respectively. We assessed age-specific prevalence using
g`QEu
5v an interval of 5 years, so that participants within each age group were independent between the
TuaBm1S{f two surveys.
EXqE~afm2 Results: Age and gender distributions were similar between the two populations. The age-specific
e$rZ5X prevalence of cortical (23.8% in 1st, 23.7% in 2nd) and PSC cataract (6.3%, 6.0%) was similar. The
t"oeQ*d% prevalence of nuclear cataract increased slightly from 18.7% to 23.9%. After age standardization,
&{t,' [ u the similar prevalence of cortical (23.8%, 23.5%) and PSC cataract (6.3%, 5.9%), and the increased
L.JT[zOfb prevalence of nuclear cataract (18.7%, 24.2%) remained.
=@~Y12o?% Conclusion: In two surveys of two population-based samples with similar age and gender
' S/gmn distributions, we found a relatively stable cortical and PSC cataract prevalence over a 6-year period.
X#
^[<5 The increased prevalence of nuclear cataract deserves further study.
4BpZJ~(p Background
@f3E`8 Age-related cataract is the leading cause of reversible visual
eTcd"Kd/ impairment in older persons [1-6]. In Australia, it is
4{|"7/PE1 estimated that by the year 2021, the number of people
Ml-6
OvQ7g affected by cataract will increase by 63%, due to population
X 0+vXz{~g aging [7]. Surgical intervention is an effective treatment
DkDmE for cataract and normal vision (> 20/40) can usually
BnF^u5kv % be restored with intraocular lens (IOL) implantation.
+9sQZB# ( Cataract surgery with IOL implantation is currently the
>Cq<@$I2EB most commonly performed, and is, arguably, the most
5*u+q2\F cost effective surgical procedure worldwide. Performance
E|shs=I Published: 20 April 2006
) ;Y;Q BMC Ophthalmology 2006, 6:17 doi:10.1186/1471-2415-6-17
Dk5 1z@ Received: 14 December 2005
>Y@H4LF;1x Accepted: 20 April 2006
{(Es(Sb}c This article is available from:
http://www.biomedcentral.com/1471-2415/6/17 ~WF\ © 2006 Tan et al; licensee BioMed Central Ltd.
$U-0)4yf This is an Open Access article distributed under the terms of the Creative Commons Attribution License (
http://creativecommons.org/licenses/by/2.0),
Z*6IW7# which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
&m;*<}X BMC Ophthalmology 2006, 6:17
http://www.biomedcentral.com/1471-2415/6/17 42ge3> Page 2 of 7
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(page number not for citation purposes)
p!AAFmc of this surgical procedure has been continuously increasing
sU^1wB
Rj in the last two decades. Data from the Australian
a(ZcmYzXU Health Insurance Commission has shown a steady
@BMx!r5kn increase in Medicare claims for cataract surgery [8]. A 2.6-
\cM2k- fold increase in the total number of cataract procedures
lPAQ3t!, from 1985 to 1994 has been documented in Australia [9].
E2+`4g@{8< The rate of cataract surgery per thousand persons aged 65
&mM0AA'\?H years or older has doubled in the last 20 years [8,9]. In the
W[r>.7>?h Blue Mountains Eye Study population, we observed a onethird
W\V.r$? v increase in cataract surgery prevalence over a mean
$<[79al# 6-year interval, from 6% to nearly 8% in two cross-sectional
*lJxH8 \ population-based samples with a similar age range
bpa?C [10]. Further increases in cataract surgery performance
'dc#F3 would be expected as a result of improved surgical skills
7_[L o4_ and technique, together with extending cataract surgical
2MK-5Kg benefits to a greater number of older people and an
/G`]=@~ increased number of persons with surgery performed on
Y}KNKO; both eyes.
)=(kBWM Both the prevalence and incidence of age-related cataract
bcz:q/f}@ link directly to the demand for, and the outcome of, cataract
-trkA'ewZ surgery and eye health care provision. This report
0<*<$U aimed to assess temporal changes in the prevalence of cortical
?Z} &EH and nuclear cataract and posterior subcapsular cataract
\z ) %$#I (PSC) in two cross-sectional population-based
?gXp*>Kg[ surveys 6 years apart.
X5w$4Kj&4l Methods
asqV~
n The Blue Mountains Eye Study (BMES) is a populationbased
?\n>
AC cohort study of common eye diseases and other
V28M lP health outcomes. The study involved eligible permanent
o}{5iTg= residents aged 49 years and older, living in two postcode
W}ofAkF areas in the Blue Mountains, west of Sydney, Australia.
?&uu[y Participants were identified through a census and were
EiaW1Cs invited to participate. The study was approved at each
dgP
3@`YS stage of the data collection by the Human Ethics Committees
c[s4EUG of the University of Sydney and the Western Sydney
$Y
gue5{c Area Health Service and adhered to the recommendations
- !
S_ryL of the Declaration of Helsinki. Written informed consent
!TcJ)0
was obtained from each participant.
A/?7w
Details of the methods used in this study have been
3r1*m
+ described previously [11]. The baseline examinations
6E}qL8'5x (BMES cross-section I) were conducted during 1992–
V G~Vs@c( 1994 and included 3654 (82.4%) of 4433 eligible residents.
@KUWxFak Follow-up examinations (BMES IIA) were conducted
*n"{J(Jt` during 1997–1999, with 2335 (75.0% of BMES
ll?X@S cross section I survivors) participating. A repeat census of
t3^&;&[ the same area was performed in 1999 and identified 1378
W!(LF7_! newly eligible residents who moved into the area or the
9o!Bzy+_ eligible age group. During 1999–2000, 1174 (85.2%) of
]}X this group participated in an extension study (BMES IIB).
AwF:Iu^3n BMES cross-section II thus includes BMES IIA (66.5%)
L{Vqh0QD& and BMES IIB (33.5%) participants (n = 3509).
/_ajaz% Similar procedures were used for all stages of data collection
S0W||#Pr at both surveys. A questionnaire was administered
UR5`ue ; including demographic, family and medical history. A
J4U1t2@)9 detailed eye examination included subjective refraction,
pI<f) r slit-lamp (Topcon SL-7e camera, Topcon Optical Co,
1yY0dOoLG) Tokyo, Japan) and retroillumination (Neitz CT-R camera,
[=`q>|;pOv Neitz Instrument Co, Tokyo, Japan) photography of the
*DhiN lens. Grading of lens photographs in the BMES has been
}SCM I4\ previously described [12]. Briefly, masked grading was
Wh{tZ~c performed on the lens photographs using the Wisconsin
bi;1s'Y<D Cataract Grading System [13]. Cortical cataract and PSC
Rbv;?'O$L were assessed from the retroillumination photographs by
Z;)%%V%o estimating the percentage of the circular grid involved.
hehFEyx Cortical cataract was defined when cortical opacity
'@P^0+B!(. involved at least 5% of the total lens area. PSC was defined
}\k"n{!" when opacity comprised at least 1% of the total lens area.
#:%/(j Slit-lamp photographs were used to assess nuclear cataract
|#N&