ABSTRACT
aR2Vvo Purpose: To quantify the prevalence of cataract, the outcomes
'
1jG?D of cataract surgery and the factors related to
e\[z Q
2Z3 unoperated cataract in Australia.
kzK4i!} Methods: Participants were recruited from the Visual
2$fFl,v!z Impairment Project: a cluster, stratified sample of more than
/|)VO?*D 5000 Victorians aged 40 years and over. At examination
Zs(I]^w;d sites interviews, clinical examinations and lens photography
vLc7RL were performed. Cataract was defined in participants who
n )n>|w_ had: had previous cataract surgery, cortical cataract greater
n0nvp@?7bJ than 4/16, nuclear greater than Wilmer standard 2, or
}Sxuc/%: posterior subcapsular greater than 1 mm2.
iut[?#f^ Results: The participant group comprised 3271 Melbourne
qG=>eRR residents, 403 Melbourne nursing home residents and 1473
D)]U+Qk rural residents.The weighted rate of any cataract in Victoria
/z0X was 21.5%. The overall weighted rate of prior cataract
pZYcCc>6& surgery was 3.79%. Two hundred and forty-nine eyes had
T;4& ^5n had prior cataract surgery. Of these 249 procedures, 49
=&5^[:ksB (20%) were aphakic, 6 (2.4%) had anterior chamber
h6yXW!8 intraocular lenses and 194 (78%) had posterior chamber
9i&(VzY[= intraocular lenses.Two hundred and eleven of these operated
DaA9fJ7a
eyes (85%) had best-corrected visual acuity of 6/12 or
/|kR=
~ better, the legal requirement for a driver’s license.Twentyseven
l@h|os (11%) had visual acuity of less than 6/18 (moderate
M_:_(y>l vision impairment). Complications of cataract surgery
SRUg2)d caused reduced vision in four of the 27 eyes (15%), or 1.9%
?$ft3p} of operated eyes. Three of these four eyes had undergone
ke+3J\;> intracapsular cataract extraction and the fourth eye had an
0ESxsba opaque posterior capsule. No one had bilateral vision
4(h19-V impairment as a result of cataract surgery. Surprisingly, no
b`lLqV<[cB particular demographic factors (such as age, gender, rural
y@T0
jI residence, occupation, employment status, health insurance
S
.KZ) status, ethnicity) were related to the presence of unoperated
?4[IIX- cataract.
!XJvhsKX y Conclusions: Although the overall prevalence of cataract is
lBYc(cr quite high, no particular subgroup is systematically underserviced
?!uj8&yyf in terms of cataract surgery. Overall, the results of
oHW:s96e cataract surgery are very good, with the majority of eyes
E#0_
y4 achieving driving vision following cataract extraction.
:EkhF6B/ Key words: cataract extraction, health planning, health
2 SJN;A~} services accessibility, prevalence
[i9.#* INTRODUCTION
;Nd,K
C0k Cataract is the leading cause of blindness worldwide and, in
+K@wh Australia, cataract extractions account for the majority of all
{mkD{2)KQ ophthalmic procedures.1 Over the period 1985–94, the rate
'l&),]|$) of cataract surgery in Australia was twice as high as would be
cnm*&1EzV expected from the growth in the elderly population.1
o>#ue<Bc6 Although there have been a number of studies reporting
Xcy Xju#"p the prevalence of cataract in various populations,2–6 there is
Ai~j
q little information about determinants of cataract surgery in
^L,Uz:[J the population. A previous survey of Australian ophthalmologists
zL%ruWNG showed that patient concern and lifestyle, rather
<%SG
<|t than visual acuity itself, are the primary factors for referral
^z _m<&r for cataract surgery.7 This supports prior research which has
'Avp16zg shown that visual acuity is not a strong predictor of need for
jQV.U~25Q cataract surgery.8,9 Elsewhere, socioeconomic status has
:Sd"~\N+ been shown to be related to cataract surgery rates.10
)R- e^Cb To appropriately plan health care services, information is
HRG2sv T4t needed about the prevalence of age-related cataract in the
Jtv~n community as well as the factors associated with cataract
W/
\M9
surgery. The purpose of this study is to quantify the prevalence
4e0/Q!o, of any cataract in Australia, to describe the factors
RyN}Gz/YN related to unoperated cataract in the community and to
vhEXtjL describe the visual outcomes of cataract surgery.
WlF}R\N! METHODS
-!ARVf * Study population
K,$
Ro@! Details about the study methodology for the Visual
s (hJ * Impairment Project have been published previously.11
X`+8rO[ Briefly, cluster sampling within three strata was employed to
8etNS~^ recruit subjects aged 40 years and over to participate.
.O1Kwu Within the Melbourne Statistical Division, nine pairs of
vz*'1ugaA census collector districts were randomly selected. Fourteen
%"C%pA nursing homes within a 5 km radius of these nine test sites
NmH:/xU?^ were randomly chosen to recruit nursing home residents.
.Jvy0B} B Clinical and Experimental Ophthalmology (2000) 28, 77–82
6%^9`|3 Original Article
^]_5oFRIj Operated and unoperated cataract in Australia
rmq^P;At Catherine A McCarty PhD, MPH, Mukesh B Nanjan PhD, Hugh R Taylor MD
5{.g~3" Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
br[n5 n Correspondence: Dr Cathy McCarty MPH, Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, 32 Gisborne Street, East Melbourne,
g3h:oQCS Victoria 3002, Australia. Email:
cathy@cera.unimelb.edu.au WNa#X]*E) 78 McCarty et al.
8YLS/dN0 w Finally, four pairs of census collector districts in four rural
\qA^3L~;5 Victorian communities were randomly selected to recruit rural
Cr;d
!= residents. A household census was conducted to identify
}vof| (Yh eligible residents aged 40 years and over who had been a
h]w5N2$}? resident at that address for at least 6 months. At the time of
ss4<s
5:y the household census, basic information about age, sex,
w~S~ country of birth, language spoken at home, education, use of
@0qDhv s corrective spectacles and use of eye care services was collected.
~|!f6= Eligible residents were then invited to attend a local
=I6u*$9< examination site for a more detailed interview and examination.
->0OqVQA The study protocol was approved by the Royal Victorian
B*,Qw_3dG Eye and Ear Hospital Human Research Ethics Committee.
sO;]l"{< Assessment of cataract
2TZ+R7B? A standardized ophthalmic examination was performed after
Z,ZebS@yG pupil dilatation with one drop of 10% phenylephrine
M)T {6w hydrochloride. Lens opacities were graded clinically at the
/U1 jCLR' time of the examination and subsequently from photos using
h=`1sfz the Wilmer cataract photo-grading system.12 Cortical and
d O' apey posterior subcapsular (PSC) opacities were assessed on
j1hx{P' retroillumination and measured as the proportion (in 1/16)
|AS`MsbI9 of pupil circumference occupied by opacity. For this analysis,
w*3DIVlxL cortical cataract was defined as 4/16 or greater opacity,
I$#)k^Q PSC cataract was defined as opacity equal to or greater than
Ac@zTK6> 1 mm2 and nuclear cataract was defined as opacity equal to
} F; Nh7? or greater than Wilmer standard 2,12 independent of visual
GSh~j-C' acuity. Examples of the minimum opacities defined as cortical,
-1P*4H2a nuclear and PSC cataract are presented in Figure 1.
Jc74A=sT Bilateral congenital cataracts or cataracts secondary to
6d%|yl intraocular inflammation or trauma were excluded from the
*?Pbk+}% analysis. Two cases of bilateral secondary cataract and eight
1}$GVb%i cases of bilateral congenital cataract were excluded from the
M^$liS.D analyses.
;&9A
Yh. A Topcon® SL5 photo slit-lamp (Topcon America Corp.,
~LKX2Q:S Paramus, NJ, USA) with a 0.1 mm slit beam of 9.0 mm in
6'^Gh B height set to an incident angle of 30° was used for examinations.
?V>\9?zb Ektachrome® 200 ASA colour slide film (Eastman
e=<%{M& Kodak Company, Rochester, NY, USA) was used to photograph
nYF *f the nuclear opacities. The cortical opacities were
FKN!*}3 photographed with an Oxford® retroillumination camera
YhzDi>hob (Marcher Enterprises Ltd, Hereford, UK) and T-MAX® 400
YV 5kzq film (Eastman Kodak). Photographs were graded separately
4XprVB by two research assistants and discrepancies were adjudicated
nU6WT | by an independent reviewer. Any discrepancies
TP5?%SlJ between the clinical grades and the photograph grades were
Gw;[maM!%` resolved. Except in cases where photographs were missing,
yye(^ the photograph grades were used in the analyses. Photograph
M-B - grades were available for 4301 (84%) for cortical
o@d+<6Um cataract, 4147 (81%) for nuclear cataract and 4303 (84%)
b)eKa40Z for PSC cataract. Cataract status was classified according to
\AT]$`8@_ the severity of the opacity in the worse eye.
U/|H%b Assessment of risk factors
6.!3g(w A standardized questionnaire was used to obtain information
: cmQ
w about education, employment and ethnic background.11
y.LJ5K$&a Specific information was elicited on the occurrence, duration
q hPvU(
, and treatment of a number of medical conditions,
iSZiJ4AUq including ocular trauma, arthritis, diabetes, gout, hypertension
<KFE.\*Z4 and mental illness. Information about the use, dose and
bwm?\l.A duration of tobacco, alcohol, analgesics and steriods were
Y\qiYra collected, and a food frequency questionnaire was used to
gyI(O>e determine current consumption of dietary sources of antioxidants
f.o,VVYi and use of vitamin supplements.
#()u=) Data management and statistical analysis
[;Q8xvVZ' Data were collected either by direct computer entry with a
b$24${*' questionnaire programmed in Paradox© (Carel Corporation,
B~_='0Gm[ Ottawa, Canada) with internal consistency checks, or
=!G3YZ on self-coding forms. Open-ended responses were coded at
g*NKY`, a later time. Data that were entered on the self-coded forms
NjCdkT&g were entered into a computer with double data entry and
J#0oL_xY# reconciliation of any inconsistencies. Data range and consistency
,=9e]pQ checks were performed on the entire data set.
&~u=vuX SAS© version 6.1 (SAS Institute, Cary, North Carolina) was
I$Q%iZ{ employed for statistical analyses.
,_ XDCu @ Ninety-five per cent confidence limits around the agespecific
H:X=v+W rates were calculated according to Cochran13 to
H<M
ggs- account for the effect of the cluster sampling. Ninety-five
'8NKrI per cent confidence limits around age-standardized rates
ob were calculated according to Breslow and Day.14 The strataspecific
$XqfwlUu/4 data were weighted according to the 1996
h^P>,dy0 Australian Bureau of Statistics census data15 to reflect the
OXC7
m cataract prevalence in the entire Victorian population.
A2o;YyF Univariate analyses with Student’s t-tests and chi-squared
L%8>deE>;D tests were first employed to evaluate risk factors for unoperated
^|6%~jkD5 cataract. Any factors with P < 0.10 were then fitted
lD!o4ZAo into a backwards stepwise logistic regression model. For the
;SzOa7 Figure 1. Minimum levels of cortical (a), nuclear (b), and posterior subcapsular (c) cataract.
V|> u, final multivariate models, P < 0.05 was considered statistically
*f~X wy" significant. Design effect was assessed through the use
GNXQD}L?b? of cluster-specific models and multivariate models. The
_/"m0/, design effect was assumed to be additive and an adjustment
td@F%* made in the variance by adding the variance associated with
IKM=Q.
7j the design effect prior to constructing the 95% confidence
=|n NC limits.
|X9YVZC RESULTS
=KwG;25hX Study population
?op6_a-wm A total of 3271 (83%) of the Melbourne residents, 403
"v-\nAu (90%) Melbourne nursing home residents, and 1473 (92%)
im^G
{3z rural residents participated. In general, non-participants did
22L#\qVkl not differ from participants.16 The study population was
o<e AZ representative of the Victorian population and Australia as
EA4aZ6% a whole.
Vtm5&- The Melbourne residents ranged in age from 40 to
x%ZjGDF m 98 years (mean = 59) and 1511 (46%) were male. The
"k\W2,q[ Melbourne nursing home residents ranged in age from 46 to
2.Ym 101 years (mean = 82) and 85 (21%) were men. The rural
|b'fp1<