ABSTRACT
SXwgn > Purpose: To quantify the prevalence of cataract, the outcomes
O)\xElu of cataract surgery and the factors related to
yJ/m21f unoperated cataract in Australia.
E@0wt^ Methods: Participants were recruited from the Visual
P-7!\[];te Impairment Project: a cluster, stratified sample of more than
~
W52Mbf 5000 Victorians aged 40 years and over. At examination
_
&19OD% sites interviews, clinical examinations and lens photography
FT[wa-b were performed. Cataract was defined in participants who
yE{l
Xp; had: had previous cataract surgery, cortical cataract greater
j;VYF than 4/16, nuclear greater than Wilmer standard 2, or
'?_I-="
Mr posterior subcapsular greater than 1 mm2.
[9'5+RXw3 Results: The participant group comprised 3271 Melbourne
J4 !Z,- residents, 403 Melbourne nursing home residents and 1473
d0MX4bhZ rural residents.The weighted rate of any cataract in Victoria
y;;^o6Gnw was 21.5%. The overall weighted rate of prior cataract
sFC1PdSk4T surgery was 3.79%. Two hundred and forty-nine eyes had
43,-
t_jV had prior cataract surgery. Of these 249 procedures, 49
v:JFUn} (20%) were aphakic, 6 (2.4%) had anterior chamber
T_5 E intraocular lenses and 194 (78%) had posterior chamber
oJ{)0;<~L intraocular lenses.Two hundred and eleven of these operated
&y3_>!L eyes (85%) had best-corrected visual acuity of 6/12 or
a9FlzR better, the legal requirement for a driver’s license.Twentyseven
|Ro\2uSr (11%) had visual acuity of less than 6/18 (moderate
7:jSP$ vision impairment). Complications of cataract surgery
YjvqU /[3 caused reduced vision in four of the 27 eyes (15%), or 1.9%
{D1=TTr^ of operated eyes. Three of these four eyes had undergone
{7Dc(gNS intracapsular cataract extraction and the fourth eye had an
lJ}G"RTm opaque posterior capsule. No one had bilateral vision
`9zP{p impairment as a result of cataract surgery. Surprisingly, no
IL YS:c58= particular demographic factors (such as age, gender, rural
X k<X
:,T residence, occupation, employment status, health insurance
<9\_b6 status, ethnicity) were related to the presence of unoperated
JOenVepQ, cataract.
"W\
#d Conclusions: Although the overall prevalence of cataract is
D2>=^WP6+ quite high, no particular subgroup is systematically underserviced
axXAy5 in terms of cataract surgery. Overall, the results of
=qIJXV cataract surgery are very good, with the majority of eyes
rh$%*l achieving driving vision following cataract extraction.
z4UeUVfZ} Key words: cataract extraction, health planning, health
XImb"
7| services accessibility, prevalence
zcIZJVYA INTRODUCTION
,h8)5Mj/J Cataract is the leading cause of blindness worldwide and, in
R%7k<1d'` Australia, cataract extractions account for the majority of all
MJ}VNv|S ophthalmic procedures.1 Over the period 1985–94, the rate
f.rHX<%q9B of cataract surgery in Australia was twice as high as would be
O?8G expected from the growth in the elderly population.1
oVc_(NH- Although there have been a number of studies reporting
K
V 4>( the prevalence of cataract in various populations,2–6 there is
QVzLf+R~ little information about determinants of cataract surgery in
uysGOyi<u the population. A previous survey of Australian ophthalmologists
(doFYF~w showed that patient concern and lifestyle, rather
1eiH%{w than visual acuity itself, are the primary factors for referral
|_!xA/_U'T for cataract surgery.7 This supports prior research which has
Q\ro )r shown that visual acuity is not a strong predictor of need for
B1*%pjy cataract surgery.8,9 Elsewhere, socioeconomic status has
z@T;N'EM been shown to be related to cataract surgery rates.10
l ^\5Jr03 To appropriately plan health care services, information is
}tc,3>/ needed about the prevalence of age-related cataract in the
ZFz>" vt@ community as well as the factors associated with cataract
NpH)K:$#% surgery. The purpose of this study is to quantify the prevalence
r95$B6 of any cataract in Australia, to describe the factors
mIl^ related to unoperated cataract in the community and to
u )
fbR describe the visual outcomes of cataract surgery.
{PYN3\N, METHODS
|D`Zi>lv Study population
Ww)qBsi8 Details about the study methodology for the Visual
pS0-<-\R Impairment Project have been published previously.11
$~ zqt%} Briefly, cluster sampling within three strata was employed to
:^J(%zy recruit subjects aged 40 years and over to participate.
d3^LalAp Within the Melbourne Statistical Division, nine pairs of
F}i rCi47c census collector districts were randomly selected. Fourteen
36
&7J{MU nursing homes within a 5 km radius of these nine test sites
B\Rq0N]' M were randomly chosen to recruit nursing home residents.
%Cb8vYz~ Clinical and Experimental Ophthalmology (2000) 28, 77–82
UmInAH4 Original Article
\=,+we
Gw@ Operated and unoperated cataract in Australia
CaZEU(i Catherine A McCarty PhD, MPH, Mukesh B Nanjan PhD, Hugh R Taylor MD
m!E36ce} Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
(VwS9:` n Correspondence: Dr Cathy McCarty MPH, Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, 32 Gisborne Street, East Melbourne,
!=q {1\# Victoria 3002, Australia. Email:
cathy@cera.unimelb.edu.au w#XE!8` 78 McCarty et al.
K& 2p<\2 Finally, four pairs of census collector districts in four rural
P|_?{1eO2 Victorian communities were randomly selected to recruit rural
E(]yjZ/
residents. A household census was conducted to identify
OXA_E/F eligible residents aged 40 years and over who had been a
/KlA7MH 6 resident at that address for at least 6 months. At the time of
~iF*+\ the household census, basic information about age, sex,
i!YZF$| country of birth, language spoken at home, education, use of
>JCSOI corrective spectacles and use of eye care services was collected.
9c#9KCmc Eligible residents were then invited to attend a local
#; }IHAR examination site for a more detailed interview and examination.
wyAqrf The study protocol was approved by the Royal Victorian
7fnKe2MM Eye and Ear Hospital Human Research Ethics Committee.
vk;>#yoox Assessment of cataract
>Z<ym|(T* A standardized ophthalmic examination was performed after
8*6J\FE<p pupil dilatation with one drop of 10% phenylephrine
PX2Ejrwj hydrochloride. Lens opacities were graded clinically at the
U|U/B time of the examination and subsequently from photos using
hO{@!H$l the Wilmer cataract photo-grading system.12 Cortical and
CdTmL{Y1 posterior subcapsular (PSC) opacities were assessed on
B;W=61d retroillumination and measured as the proportion (in 1/16)
>`,v?<>+ of pupil circumference occupied by opacity. For this analysis,
&sx/qS#,VL cortical cataract was defined as 4/16 or greater opacity,
+u25>pX PSC cataract was defined as opacity equal to or greater than
O aF+Z@
s 1 mm2 and nuclear cataract was defined as opacity equal to
>2$Ehw:K^ or greater than Wilmer standard 2,12 independent of visual
K=`*cSU> acuity. Examples of the minimum opacities defined as cortical,
>KGQ#hnH nuclear and PSC cataract are presented in Figure 1.
vbwEX 6 Bilateral congenital cataracts or cataracts secondary to
;CAB.aB~ intraocular inflammation or trauma were excluded from the
B#EF/\5 analysis. Two cases of bilateral secondary cataract and eight
2(`2 f cases of bilateral congenital cataract were excluded from the
&\!-d%||) analyses.
hh: )"<[ A Topcon® SL5 photo slit-lamp (Topcon America Corp.,
rw+0<r3|K Paramus, NJ, USA) with a 0.1 mm slit beam of 9.0 mm in
TvI}yaCu/x height set to an incident angle of 30° was used for examinations.
`4;<\VYCr Ektachrome® 200 ASA colour slide film (Eastman
X8;03EW; Kodak Company, Rochester, NY, USA) was used to photograph
hc0VS3 k) the nuclear opacities. The cortical opacities were
:I<%.|8 photographed with an Oxford® retroillumination camera
O8dDoP\F2 (Marcher Enterprises Ltd, Hereford, UK) and T-MAX® 400
\dufKeiS&a film (Eastman Kodak). Photographs were graded separately
"OK(<x]3;> by two research assistants and discrepancies were adjudicated
Pfd FB
by an independent reviewer. Any discrepancies
4S"K%2'O between the clinical grades and the photograph grades were
o5Qlp5`:u resolved. Except in cases where photographs were missing,
jh8%Xu]t the photograph grades were used in the analyses. Photograph
Saz+GQ G grades were available for 4301 (84%) for cortical
Zjo9c{\ cataract, 4147 (81%) for nuclear cataract and 4303 (84%)
G]&:">&R for PSC cataract. Cataract status was classified according to
[$H8?J the severity of the opacity in the worse eye.
aty
K^*aX Assessment of risk factors
]$*N5
Y A standardized questionnaire was used to obtain information
(G$m}ng about education, employment and ethnic background.11
lbv, jS Specific information was elicited on the occurrence, duration
~r=TVHjqi and treatment of a number of medical conditions,
:;
??!V including ocular trauma, arthritis, diabetes, gout, hypertension
dYr# and mental illness. Information about the use, dose and
-@J;FjrXmP duration of tobacco, alcohol, analgesics and steriods were
cUy6/x9& collected, and a food frequency questionnaire was used to
u $sX6 determine current consumption of dietary sources of antioxidants
H56e#:[$ and use of vitamin supplements.
%8 4<@f&n] Data management and statistical analysis
%FF
S&vd Data were collected either by direct computer entry with a
u\t ; questionnaire programmed in Paradox© (Carel Corporation,
PK+][.6H Ottawa, Canada) with internal consistency checks, or
y>~KeUC on self-coding forms. Open-ended responses were coded at
.vT'hu
a later time. Data that were entered on the self-coded forms
_$=xa6YA were entered into a computer with double data entry and
=,0E3:X^ reconciliation of any inconsistencies. Data range and consistency
Ap97 Zcw checks were performed on the entire data set.
gV`:eNo* SAS© version 6.1 (SAS Institute, Cary, North Carolina) was
s;5PHweWf employed for statistical analyses.
txL5'mK Ninety-five per cent confidence limits around the agespecific
h_A}i2/{ rates were calculated according to Cochran13 to
WO}JIExy account for the effect of the cluster sampling. Ninety-five
Z;n}*^U per cent confidence limits around age-standardized rates
T`W FY
were calculated according to Breslow and Day.14 The strataspecific
kYR&t}jlCg data were weighted according to the 1996
%b!p{p Australian Bureau of Statistics census data15 to reflect the
?29
KvT;#] cataract prevalence in the entire Victorian population.
@9c^{x\4 Univariate analyses with Student’s t-tests and chi-squared
_nTjCN625 tests were first employed to evaluate risk factors for unoperated
L50`,,WF cataract. Any factors with P < 0.10 were then fitted
y'zEaL&SI@ into a backwards stepwise logistic regression model. For the
-)$)<k Figure 1. Minimum levels of cortical (a), nuclear (b), and posterior subcapsular (c) cataract.
h 1Q7(8=Eg final multivariate models, P < 0.05 was considered statistically
D(r|sw
significant. Design effect was assessed through the use
T+~~w'v0 of cluster-specific models and multivariate models. The
| z('yy$ design effect was assumed to be additive and an adjustment
Az)P&*2:'` made in the variance by adding the variance associated with
wvc?2~`
the design effect prior to constructing the 95% confidence
Gu%`__ limits.
>T(f RESULTS
0dgR;Dl(
Study population
Z,d/FC#y( A total of 3271 (83%) of the Melbourne residents, 403
-|3U0:'m (90%) Melbourne nursing home residents, and 1473 (92%)
5-C6; 7%: rural residents participated. In general, non-participants did
O=-|b kO not differ from participants.16 The study population was
;pU LJ}rDb representative of the Victorian population and Australia as
Xz5=fj& a whole.
P, Vq/Tt The Melbourne residents ranged in age from 40 to
F*NIs:3; 98 years (mean = 59) and 1511 (46%) were male. The
ZU:gNO0 Melbourne nursing home residents ranged in age from 46 to
o+ tY[UX 101 years (mean = 82) and 85 (21%) were men. The rural
"@
f`O residents ranged in age from 40 to 103 years (mean = 60)
qGh rJ6R! and 701 (47.5%) were men.
xApa+j6I Prevalence of cataract and prior cataract surgery
N..u<06j/ As would be expected, the rate of any cataract increases
"jpjBH:c$ dramatically with age (Table 1). The weighted rate of any
>Ek`PVPD cataract in Victoria was 21.5% (95% CL 18.1, 24.9).
.&[nS<~` Although the rates varied somewhat between the three
MP3E]T~: strata, they were not significantly different as the 95% confidence
IBuuZ.=j2h limits overlapped. The per cent of cataractous eyes
m?m,w$K with best-corrected visual acuity of less than 6/12 was 12.5%
@TH \hr] (65/520) for cortical cataract, 18% for nuclear cataract
cX&c% ~ (97/534) and 14.4% (27/187) for PSC cataract. Cataract
T&S<