BioMed Central
Zk4( Page 1 of 7
-5Km9X8 (page number not for citation purposes)
\40d?N#D BMC Ophthalmology
O+o4E?} Research article Open Access
qC%[J:RwF Comparison of age-specific cataract prevalence in two
m#(tBfH[ population-based surveys 6 years apart
zJp@\Yo+ Ava Grace Tan†, Jie Jin Wang*†, Elena Rochtchina† and Paul Mitchell†
\*_@`1m Address: Centre for Vision Research, Westmead Millennium Institute, Department of Ophthalmology, University of Sydney, Westmead Hospital,
XgfaTX* Westmead, NSW, Australia
P0En&g+~ Email: Ava Grace Tan -
ava_tan@wmi.usyd.edu.au; Jie Jin Wang* -
jiejin_wang@wmi.usyd.edu.au;
G|p3NhLgO= Elena Rochtchina -
elena_rochtchina@wmi.usyd.edu.au; Paul Mitchell -
paul_mitchell@wmi.usyd.edu.au g8_C|lVZi * Corresponding author †Equal contributors
W:8*Z8?7 Abstract
||lI_B Background: In this study, we aimed to compare age-specific cortical, nuclear and posterior
]vPa
A subcapsular (PSC) cataract prevalence in two surveys 6 years apart.
Cyb-}l Methods: The Blue Mountains Eye Study examined 3654 participants (82.4% of those eligible) in
q]\bJV^/U cross-section I (1992–4) and 3509 participants (75.1% of survivors and 85.2% of newly eligible) in
O>E2G]K]\ cross-section II (1997–2000, 66.5% overlap with cross-section I). Cataract was assessed from lens
MBbycI, photographs following the Wisconsin Cataract Grading System. Cortical cataract was defined if
4)BPrWea1 cortical opacity comprised ≥ 5% of lens area. Nuclear cataract was defined if nuclear opacity ≥
#>|l"1 Wisconsin standard 4. PSC was defined if any present. Any cataract was defined to include persons
K$H>/*&'~ who had previous cataract surgery. Weighted kappa for inter-grader reliability was 0.82, 0.55 and
\k=.w 0.82 for cortical, nuclear and PSC cataract, respectively. We assessed age-specific prevalence using
sI
u{_b an interval of 5 years, so that participants within each age group were independent between the
hm%'k~ two surveys.
$>3/6(bW Results: Age and gender distributions were similar between the two populations. The age-specific
Sv7_-#SW<( prevalence of cortical (23.8% in 1st, 23.7% in 2nd) and PSC cataract (6.3%, 6.0%) was similar. The
M1MpR+7S prevalence of nuclear cataract increased slightly from 18.7% to 23.9%. After age standardization,
(;V=A4F-D the similar prevalence of cortical (23.8%, 23.5%) and PSC cataract (6.3%, 5.9%), and the increased
?/_8zpW prevalence of nuclear cataract (18.7%, 24.2%) remained.
LvJ')HG Conclusion: In two surveys of two population-based samples with similar age and gender
0x}8} distributions, we found a relatively stable cortical and PSC cataract prevalence over a 6-year period.
VOYuog 5o The increased prevalence of nuclear cataract deserves further study.
S^@I4Z Background
# $:ddOY Age-related cataract is the leading cause of reversible visual
uA?_\z? impairment in older persons [1-6]. In Australia, it is
*-timVlaE estimated that by the year 2021, the number of people
jb' hqz affected by cataract will increase by 63%, due to population
8t$a8 PE aging [7]. Surgical intervention is an effective treatment
?-g=Rfpag for cataract and normal vision (> 20/40) can usually
PMJe6*(x/ be restored with intraocular lens (IOL) implantation.
+w-UK[p Cataract surgery with IOL implantation is currently the
<qzHMyAi most commonly performed, and is, arguably, the most
`x"0 cost effective surgical procedure worldwide. Performance
Jy'ge4]3 Published: 20 April 2006
R|T_9/#) BMC Ophthalmology 2006, 6:17 doi:10.1186/1471-2415-6-17
D<[4}og&] Received: 14 December 2005
f[n#Eu} Accepted: 20 April 2006
'#SacJ\L7
This article is available from:
http://www.biomedcentral.com/1471-2415/6/17 DRD%pm( © 2006 Tan et al; licensee BioMed Central Ltd.
D-.XSIEMu This is an Open Access article distributed under the terms of the Creative Commons Attribution License (
http://creativecommons.org/licenses/by/2.0),
"
D7*en which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
H&65X BMC Ophthalmology 2006, 6:17
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w$H=GF?" (page number not for citation purposes)
@]Ye36v0#L of this surgical procedure has been continuously increasing
byM/LE7) in the last two decades. Data from the Australian
J<:qzwh Health Insurance Commission has shown a steady
>9D=PnHnD increase in Medicare claims for cataract surgery [8]. A 2.6-
WKZ9i2hcdf fold increase in the total number of cataract procedures
M_V\mYC8I from 1985 to 1994 has been documented in Australia [9].
tFvti5 The rate of cataract surgery per thousand persons aged 65
#;U_ L`q years or older has doubled in the last 20 years [8,9]. In the
65RWaz;| Blue Mountains Eye Study population, we observed a onethird
VAc-RaA increase in cataract surgery prevalence over a mean
6OMywGI[Z 6-year interval, from 6% to nearly 8% in two cross-sectional
pB{QO4qn population-based samples with a similar age range
p"/1Kwqx [10]. Further increases in cataract surgery performance
(F_Wys=6 would be expected as a result of improved surgical skills
<tAn2e! and technique, together with extending cataract surgical
*&>1A A benefits to a greater number of older people and an
)cB00*/ increased number of persons with surgery performed on
.l5y!? both eyes.
3A]Y=gfa Both the prevalence and incidence of age-related cataract
xfqgK D> link directly to the demand for, and the outcome of, cataract
5xP\6Nx6&5 surgery and eye health care provision. This report
,T_HE3 K aimed to assess temporal changes in the prevalence of cortical
'OSZ'F3PV and nuclear cataract and posterior subcapsular cataract
~f2H@# (PSC) in two cross-sectional population-based
{) 4D1 surveys 6 years apart.
lu_ y 9o^ Methods
Q4-d2I>0 The Blue Mountains Eye Study (BMES) is a populationbased
.Xh ^L cohort study of common eye diseases and other
_S/bwPj|~y health outcomes. The study involved eligible permanent
~!j1</$_ residents aged 49 years and older, living in two postcode
Yul-.X areas in the Blue Mountains, west of Sydney, Australia.
Bm"jf] Participants were identified through a census and were
&fq-U5zH invited to participate. The study was approved at each
Nqp%Z7G stage of the data collection by the Human Ethics Committees
}m/aigA[1 of the University of Sydney and the Western Sydney
,ju 1:` Area Health Service and adhered to the recommendations
5 |{0|mP of the Declaration of Helsinki. Written informed consent
lh3%2Dq$ was obtained from each participant.
;^lVIS%&{ Details of the methods used in this study have been
,SuF1&4 described previously [11]. The baseline examinations
4vPQuk! (BMES cross-section I) were conducted during 1992–
C78YHjy 1994 and included 3654 (82.4%) of 4433 eligible residents.
:}FMauHh Follow-up examinations (BMES IIA) were conducted
37x2fnC during 1997–1999, with 2335 (75.0% of BMES
lyfLkBF cross section I survivors) participating. A repeat census of
KnbT2 the same area was performed in 1999 and identified 1378
c^}gJ newly eligible residents who moved into the area or the
F N;X"it. eligible age group. During 1999–2000, 1174 (85.2%) of
8V`r*:\ this group participated in an extension study (BMES IIB).
E {4/$} BMES cross-section II thus includes BMES IIA (66.5%)
Vd4x!Vk and BMES IIB (33.5%) participants (n = 3509).
}:5r#Cd Similar procedures were used for all stages of data collection
DoX#+
07u4 at both surveys. A questionnaire was administered
GfD!Z3 including demographic, family and medical history. A
{$bAs9L detailed eye examination included subjective refraction,
!FZb3U@ slit-lamp (Topcon SL-7e camera, Topcon Optical Co,
0Q_AF`" Tokyo, Japan) and retroillumination (Neitz CT-R camera,
%L}9nc%~eP Neitz Instrument Co, Tokyo, Japan) photography of the
#q9jFW8 lens. Grading of lens photographs in the BMES has been
`Q<hL {AH previously described [12]. Briefly, masked grading was
IX']s;b performed on the lens photographs using the Wisconsin
UMpC2)5 Cataract Grading System [13]. Cortical cataract and PSC
;t:B:4r(j were assessed from the retroillumination photographs by
}ARWR.7Cc estimating the percentage of the circular grid involved.
yDWzsA/X Cortical cataract was defined when cortical opacity
l131^48U involved at least 5% of the total lens area. PSC was defined
F4M<5Yi when opacity comprised at least 1% of the total lens area.
(\e,,C%; Slit-lamp photographs were used to assess nuclear cataract
R#`hT using the Wisconsin standard set of four lens photographs
Uxn_nh [13]. Nuclear cataract was defined when nuclear opacity
@E{c P%fv was at least as great as the standard 4 photograph. Any cataract
79n,bb5 was defined to include persons who had previous
MM3
X!
tq cataract surgery as well as those with any of three cataract
Z`o}xV types. Inter-grader reliability was high, with weighted
`][~0\Y3m kappa 0.82 for cortical cataract, 0.55 (simple kappa 0.75)
,u-i9`B for nuclear cataract and 0.82 for PSC grading. The intragrader
Mou>|U1e" reliability for nuclear cataract was assessed with
1>c`c]s3 simple kappa 0.83 for the senior grader who graded
~!E%GCyFy nuclear cataract at both surveys. All PSC cases were confirmed
z|=l^u6uS by an ophthalmologist (PM).
cAM1\3HWT" In cross-section I, 219 persons (6.0%) had missing or
&"BmCDOq ungradable Neitz photographs, leaving 3435 with photographs
mLd=+&M available for cortical cataract and PSC assessment,
X4!`
V? while 1153 (31.6%) had randomly missing or ungradable
br.jj Topcon photographs due to a camera malfunction, leaving
Fx~=mYU 2501 with photographs available for nuclear cataract
e-sMU assessment. Comparison of characteristics between participants
)7<JGzBZ1 with and without Neitz or Topcon photographs in
x|<rt966A cross-section I showed no statistically significant differences
;eI,1
[_ between the two groups, as reported previously
eh2 w7@7Q [12]. In cross-section II, 441 persons (12.5%) had missing
n,hHh=.Fu or ungradable Neitz photographs, leaving 3068 for cortical
SouPk/-B80 cataract and PSC assessment, and 648 (18.5%) had
/k|y \'< missing or ungradable Topcon photographs, leaving 2860
^*#5iT8/ for nuclear cataract assessment.
K%P$#a Data analysis was performed using the Statistical Analysis
vg &Dr System (SAS, SAS Institute, Cary, NC, USA). Age-adjusted
|y)R lb#d prevalence was calculated using direct standardization of
..UmbJJ.u the cross-section II population to the cross-section I population.
i=OPl We assessed age-specific prevalence using an
6AKH0t|4 interval of 5 years, so that participants within each age
mk~&>\ group were independent between the two cross-sectional
q]T{g*lT surveys.
8fKt6T BMC Ophthalmology 2006, 6:17
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%Ui&SZ\ (page number not for citation purposes)
{" S"V Results
wASgdGoy Characteristics of the two survey populations have been
Ki(qA(r previously compared [14] and showed that age and sex
fdc
?`4 distributions were similar. Table 1 compares participant
`*mctjSN characteristics between the two cross-sections. Cross-section
j2\bCGY II participants generally had higher rates of diabetes,
V0q./NuO hypertension, myopia and more users of inhaled steroids.
8VQJUwf; Cataract prevalence rates in cross-sections I and II are
Qu,W
3d shown in Figure 1. The overall prevalence of cortical cataract
G7yCGT)vQ was 23.8% and 23.7% in cross-sections I and II,
X1?7}VO respectively (age-sex adjusted P = 0.81). Corresponding
/{vv n prevalence of PSC was 6.3% and 6.0% for the two crosssections
WF,<7mx=- (age-sex adjusted P = 0.60). There was an
|b7v(Hx increased prevalence of nuclear cataract, from 18.7% in
4|YCBXWh cross-section I to 23.9% in cross-section II over the 6-year
)8VrGg? period (age-sex adjusted P < 0.001). Prevalence of any cataract
|=L~>G (including persons who had cataract surgery), however,
:IlRn`9X` was relatively stable (46.9% and 46.8% in crosssections
c ]M!4. I and II, respectively).
fgIzT!fyz After age-standardization, these prevalence rates remained
8z0j}xY% stable for cortical cataract (23.8% and 23.5% in the two
<^q4^Q[ surveys) and PSC (6.3% and 5.9%). The slightly increased
OFJ49X prevalence of nuclear cataract (from 18.7% to 24.2%) was
/tR@J8pV not altered.
iU"jV*P] Table 2 shows the age-specific prevalence rates for cortical
1)yEx1 cataract, PSC and nuclear cataract in cross-sections I and
>
2_xRn<P II. A similar trend of increasing cataract prevalence with
^kJ(bBY increasing age was evident for all three types of cataract in
r'0IAJ-; both surveys. Comparing the age-specific prevalence
lx_jy>$}r between the two surveys, a reduction in PSC prevalence in
`>KB8SY:qK cross-section II was observed in the older age groups (≥ 75
p
xP,cS years). In contrast, increased nuclear cataract prevalence
c-3-,pyM_T in cross-section II was observed in the older age groups (≥
2L"$p? 70 years). Age-specific cortical cataract prevalence was relatively
LA &W@ consistent between the two surveys, except for a
"P.H reduction in prevalence observed in the 80–84 age group
1AMxZ (e and an increasing prevalence in the older age groups (≥ 85
dd1CuOd6(1 years).
gS{hfDpk,h Similar gender differences in cataract prevalence were
_RI`I}&9Z observed in both surveys (Table 3). Higher prevalence of
)y>o;^5' cortical and nuclear cataract in women than men was evident
A+Uil\% but the difference was only significant for cortical
u&{}hv&FY cataract (age-adjusted odds ratio, OR, for women 1.3,
L3}n(KAJj 95% confidence intervals, CI, 1.1–1.5 in cross-section I
);EW(7KeL
and OR 1.4, 95% CI 1.1–1.6 in cross-section II). In con-
^w]N#%k\H Table 1: Participant characteristics.
]^aOYtKX Characteristics Cross-section I Cross-section II
yQ$
Q{,S9 n % n %
$Ro]]NUz| Age (mean) (66.2) (66.7)
tF lLKziU 50–54 485 13.3 350 10.0
B=)&43)\ 55–59 534 14.6 580 16.5
;Q*=AW 60–64 638 17.5 600 17.1
)}ygzKEa 65–69 671 18.4 639 18.2
uWm,mGd9 70–74 538 14.7 572 16.3
`| nC r 75–79 422 11.6 407 11.6
2cv!85 80–84 230 6.3 226 6.4
*B<Ig^c 85–89 100 2.7 110 3.1
kpF")0qr 90+ 36 1.0 24 0.7
Gg'sgn
Female 2072 56.7 1998 57.0
+
=.>9 Ever Smokers 1784 51.2 1789 51.2
YY{0WWua Use of inhaled steroids 370 10.94 478 13.8^
BY*{j&^ History of:
PSCzeR Diabetes 284 7.8 347 9.9^
RP!!6A6: Hypertension 1669 46.0 1825 52.2^
R#"LP7\ Emmetropia* 1558 42.9 1478 42.2
VTS7K2lBvX Myopia* 442 12.2 495 14.1^
~yX8p7qr Hyperopia* 1633 45.0 1532 43.7
K
jw==5)} n = number of persons affected
VkFvV><" * best spherical equivalent refraction correction
%E<.\\^% ^ P < 0.01
MH wjJ BMC Ophthalmology 2006, 6:17
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]|H`?L (page number not for citation purposes)
c#)!-5E~H t
5Z8Zb. rast, men had slightly higher PSC prevalence than women
uUhqj.::<Y in both cross-sections but the difference was not significant
f$7Xh~
(OR 1.1, 95% CI 0.8–1.4 for men in cross-section I
aNt+;M7g` and OR 1.2, 95% 0.9–1.6 in cross-section II).
)GT*HJR(vc Discussion
8-JOfq}s Findings from two surveys of BMES cross-sectional populations
7LFJi@*8 with similar age and gender distribution showed
i`nmA-Zj[ that the prevalence of cortical cataract and PSC remained
wOMrUWB0 stable, while the prevalence of nuclear cataract appeared
|\}&mBR to have increased. Comparison of age-specific prevalence,
96(3ilAt with totally independent samples within each age group,
W?>C$_p C confirmed the robustness of our findings from the two
DPWt=IFU survey samples. Although lens photographs taken from
c*m7'\ the two surveys were graded for nuclear cataract by the
9V'ok.B.x same graders, who documented a high inter- and intragrader
JJQS7
,vG reliability, we cannot exclude the possibility that
dCb7sqJ% variations in photography, performed by different photographers,
qsT@aSIo9 may have contributed to the observed difference
=~D QX\ in nuclear cataract prevalence. However, the overall
hR4\:s+[ Table 2: Age-specific prevalence of cataract types in cross sections I and II.
$q|-9B Cataract type Age (years) Cross-section I Cross-section II
|#b]e|aP n % (95% CL)* n % (95% CL)*
DXa!"ZU Cortical 50–54 473 4.4 (2.6–6.3) 338 7.4 (4.6–10.2)
>eC>sTPQ{ 55–59 522 9.2 (6.7–11.7) 542 9.0 (6.6–11.5)
w=QlQ\ 60–64 615 16.4 (13.5–19.4) 556 16.7 (13.6–19.8)
BNw};.lO 65–69 653 26.2 (22.8–29.6) 581 23.6 (20.1–27.0)
i8h^~d2" 70–74 516 31.2 (27.2–35.2) 514 35.4 (31.3–39.6)
t?aOZps 75–79 366 40.2 (35.1–45.2) 332 39.8 (34.5–45.1)
{i^F4A@=Z 80–84 194 58.8 (51.8–65.8) 163 42.9 (35.3–50.6)
tH)fu%:p 85–89 74 52.7 (41.1–64.4) 73 54.8 (43.1–66.5)
PY@BgL=/ 90+ 22 68.2 (47.0–89.3) 14 78.6 (54.0–103.2)
2JhE`EVH PSC 50–54 474 2.7 (1.3–4.2) 338 2.4 (0.7–4.0)
`x:
O&2 55–59 522 2.9 (1.4–4.3) 541 2.6 (1.3–3.9)
D#k ~lEPub 60–64 616 4.6 (2.9–6.2) 548 5.7 (3.7–7.6)
;Tec)Fl 65–69 655 6.3 (4.4–8.1) 573 4.5 (2.8–6.3)
BO,xA -+ 70–74 517 6.8 (4.6–8.9) 505 9.7 (7.1–12.3)
] :SbvsPm 75–79 367 11.4 (8.2–14.7) 327 9.5 (6.3–12.7)
wVm
QE 80–84 196 12.2 (7.6–16.9) 155 10.3 (5.5–15.2)
g7;OZ#\ 85–89 74 18.9 (9.8–28.1) 69 11.6 (3.9–19.4)
]~@uStHn 90+ 23 21.7 (3.5–40.0) 11 0.0
98rO]
rg Nuclear 50–54 323 1.6 (0.2–2.9) 331 0.9 (–0.2–1.9)
JKF/z@Vbe\ 55–59 386 2.3 (0.8–3.8) 507 3.6 (1.9–5.2)
YD,<]q% 60–64 453 5.3 (3.2–7.4) 501 11.6 (8.8–14.4)
E*vh<C 65–69 478 17.2 (13.8–20.1) 534 18.5 (15.2–21.9)
?dyt!>C 70–74 392 27.6 (23.1–32.0) 453 36.0 (31.6–40.4)
|vPU]R>6 75–79 255 45.1 (39.0–51.3) 302 55.6 (50.0–61.3)
}F';"ybrU) 80–84 146 54.1 (45.9–62.3) 147 73.5 (66.3–80.7)
C({r1l4[D 85–89 50 64.0 (50.2–77.8) 70 80.0 (70.4–89.6)
:I2spBx 90+ 18 72.2 (49.3–95.1) 15 73.3 (48.0–98.7)
mM2DZ^"j( n = number of persons
'[vCC' * 95% Confidence Limits
.^wBv
'Y Cataract FMioguunrtea i1n ps rEeyvea lSetnucdey in cross-sections I and II of the Blue
^8=e8O Cataract prevalence in cross-sections I and II of the Blue
.1f!w!ltVR Mountains Eye Study.
J6mUU3F9f 0
jG%J.u^k 10
Dn48?A[v 20
AHzm9U @ 30
s_P[lbHt. 40
}\QXPU{UVd 50
(\%J0kR3[ cortical PSC nuclear any
-FS!v^ cataract
kvN<o-B Cataract type
N>w+YFM %
sWKv>bx Cross-section I
*rVI[kL Cross-section II
qOAhBZ~ BMC Ophthalmology 2006, 6:17
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LhSXz>AX (page number not for citation purposes)
j:$Z-s prevalence of any cataract (including cataract surgery) was
W~5gTiBZ] relatively stable over the 6-year period.
2RdpVNx\y Although different population-based studies used different
Bk
B9u&s^ grading systems to assess cataract [15], the overall
!1mAq+q! prevalence of the three cataract types were similar across
A:\_ \B%< different study populations [12,16-23]. Most studies have
s>=$E~qq suggested that nuclear cataract is the most prevalent type
!Pu7%nV. of cataract, followed by cortical cataract [16-20]. Ours and
E O
" other studies reported that cortical cataract was the most
F.D6O[pZ prevalent type [12,21-23].
b/4gs62{k Our age-specific prevalence data show a reduction of
_)~|Z~ 15.9% in cortical cataract prevalence for the 80–84 year
Q'[~$~&` age group, concordant with an increase in cataract surgery
I#xhmsF prevalence by 9% in those aged 80+ years observed in the
3*R(&O6} same study population [10]. Although cortical cataract is
=H"%{VeC5 thought to be the least likely cataract type leading to a cataract
wKJK!P surgery, this may not be the case in all older persons.
V /)3d A relatively stable cortical cataract and PSC prevalence
\rCdsN 2H over the 6-year period is expected. We cannot offer a
}dSFv
definitive explanation for the increase in nuclear cataract
(CE2]Nv9") prevalence. A possible explanation could be that a moderate
`KE(R8y level of nuclear cataract causes less visual disturbance
Koz0Xy than the other two types of cataract, thus for the oldest age
O>ZJOKe groups, persons with nuclear cataract could have been less
HPK}Z|Vl likely to have surgery unless it is very dense or co-existing
tOPkx( with cortical cataract or PSC. Previous studies have shown
5d|+ c< that functional vision and reading performance were high
|h:3BV_ in patients undergoing cataract surgery who had nuclear
+@PZ3
[s cataract only compared to those with mixed type of cataract
NmN:x&/ (nuclear and cortical) or PSC [24,25]. In addition, the
[ HjGdC overall prevalence of any cataract (including cataract surgery)
,=P0rbtK was similar in the two cross-sections, which appears
v=H!Y"; to support our speculation that in the oldest age group,
U7G|4( nuclear cataract may have been less likely to be operated
6.4,Qae9E than the other two types of cataract. This could have
98WJ"f_ # resulted in an increased nuclear cataract prevalence (due
F#{PJ# to less being operated), compensated by the decreased
|nO}YU\E prevalence of cortical cataract and PSC (due to these being
Et
B56FU\ more likely to be operated), leading to stable overall prevalence
^[zF
IO of any cataract.
`RE1q)o}8M Possible selection bias arising from selective survival
PvdR)ZEm among persons without cataract could have led to underestimation
g/,O51f' of cataract prevalence in both surveys. We
NO)vk+ assume that such an underestimation occurred equally in
_d<\@Tkw both surveys, and thus should not have influenced our
Ia)
^ assessment of temporal changes.
vGPaW YV Measurement error could also have partially contributed
:Ee5:S to the observed difference in nuclear cataract prevalence.
d>7bwG+k Assessment of nuclear cataract from photographs is a
i@d@~M7/ potentially subjective process that can be influenced by
-OP5v8c
f variations in photography (light exposure, focus and the
~
.Eln+N slit-lamp angle when the photograph was taken) and
cl-i6[F grading. Although we used the same Topcon slit-lamp
>Y/1%Hp9 camera and the same two graders who graded photos
/7
zy5
from both surveys, we are still not able to exclude the possibility
N,_ej@L8 of a partial influence from photographic variation
Afa{f}st on this result.
VbX$i!>8 A similar gender difference (women having a higher rate
)+9D$m=P; than men) in cortical cataract prevalence was observed in
E]Hl&t/} both surveys. Our findings are in keeping with observations
M>k7
'@
G from the Beaver Dam Eye Study [18], the Barbados
}Mo9r4} Eye Study [22] and the Lens Opacities Case-Control
i]LK,' Group [26]. It has been suggested that the difference
Xc5[d`] could be related to hormonal factors [18,22]. A previous
U^0vLyqW^5 study on biochemical factors and cataract showed that a
#(*WxVE lower level of iron was associated with an increased risk of
.]H]H *wC cortical cataract [27]. No interaction between sex and biochemical
iVu+ct-iv factors were detected and no gender difference
@+X}O/74 was assessed in this study [27]. The gender difference seen
qc'tK6=jp in cortical cataract could be related to relatively low iron
y!!+IeReS levels and low hemoglobin concentration usually seen in
n8G#TQrAE women [28]. Diabetes is a known risk factor for cortical
O x$|ZEh Table 3: Gender distribution of cataract types in cross-sections I and II.
p
go\(K0 Cataract type Gender Cross-section I Cross-section II
X-{:.9 n % (95% CL)* n % (95% CL)*
Sc~kO4 Cortical Male 1496 21.1 (19.0–23.1) 1328 20.4 (18.2–22.6)
HIa$0g0J Female 1939 25.9 (23.9–27.8) 1785 26.2 (24.2–28.3)
M9OFK\) PSC Male 1500 6.5 (5.2–7.7) 1314 6.4 (5.1–7.7)
dju&Ku
Female 1944 6.2 (5.1–7.2) 1753 5.7 (4.6–6.7)
b);}x1L.T Nuclear Male 1106 17.6 (15.4–19.9) 1225 22.5 (20.1–24.8)
D[#\Y+N Female 1395 19.5 (17.4–21.6) 1635 25.0 (22.9–27.1)
l*:p== n = number of persons
cT0g, ^& * 95% Confidence Limits
N~ozyIP, BMC Ophthalmology 2006, 6:17
http://www.biomedcentral.com/1471-2415/6/17 1aT$07G0 Page 6 of 7
+%Gm2e;_u (page number not for citation purposes)
F_Pd\Aq8 cataract but in this particular population diabetes is more
>SGSn/AJi prevalent in men than women in all age groups [29]. Differential
pq&c]8H exposures to cataract risk factors or different dietary
7=AKQ7BB>b or lifestyle patterns between men and women may
4QVd{ also be related to these observations and warrant further
N+V-V-PVk study.
N_DgnZ7* Conclusion
\~H"!vj In summary, in two population-based surveys 6 years
QE}@|H9xs apart, we have documented a relatively stable prevalence
o <'gM]$ of cortical cataract and PSC over the period. The observed
|#B"j1D,H overall increased nuclear cataract prevalence by 5% over a
qpeK><o 6-year period needs confirmation by future studies, and
~<U3KB
reasons for such an increase deserve further study.
YBO53S]= Competing interests
p{J_d,JH The author(s) declare that they have no competing interests.
Y"jDZG? Authors' contributions
"J1ar.li AGT graded the photographs, performed literature search
>8tuLd*T and wrote the first draft of the manuscript. JJW graded the
_YS+{0
Vq% photographs, critically reviewed and modified the manuscript.
M5V1j(URE ER performed the statistical analysis and critically
A!kyga6F5 reviewed the manuscript. PM designed and directed the
f.$o|R=v study, adjudicated cataract cases and critically reviewed
t_rDXhM and modified the manuscript. All authors read and
gsp7N approved the final manuscript.
<.B s`P Acknowledgements
J4g;~#_19 This study was supported by the Australian National Health & Medical
zFr} $ Research Council, Canberra, Australia (Grant Nos 974159, 991407). The
j#f&!&G5<& abstract was presented at the Association for Research in Vision and Ophthalmology
`RcNqPY#S (ARVO) meeting in Fort Lauderdale, Florida, USA, May 2005.
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