ABSTRACT
yh.WTgcW Purpose: To quantify the prevalence of cataract, the outcomes
BqtN= of cataract surgery and the factors related to
CW+g
Z! unoperated cataract in Australia.
2%)~E50U Methods: Participants were recruited from the Visual
Ti>}To}B5 Impairment Project: a cluster, stratified sample of more than
(t,mtdD#1 5000 Victorians aged 40 years and over. At examination
h7AO5"6 sites interviews, clinical examinations and lens photography
UI*&@!%bzp were performed. Cataract was defined in participants who
GK#D R/OM had: had previous cataract surgery, cortical cataract greater
ypx`!2Q$ than 4/16, nuclear greater than Wilmer standard 2, or
M%s!qC+ posterior subcapsular greater than 1 mm2.
SBY0
L. Results: The participant group comprised 3271 Melbourne
97pnq1b residents, 403 Melbourne nursing home residents and 1473
{*nE8+..A rural residents.The weighted rate of any cataract in Victoria
W >|'4y) was 21.5%. The overall weighted rate of prior cataract
Y@+9
Ukd/ surgery was 3.79%. Two hundred and forty-nine eyes had
z2q!_ ~ had prior cataract surgery. Of these 249 procedures, 49
!04^E (20%) were aphakic, 6 (2.4%) had anterior chamber
61*b|.sl'# intraocular lenses and 194 (78%) had posterior chamber
H7f
Xg intraocular lenses.Two hundred and eleven of these operated
5Hs!s+ eyes (85%) had best-corrected visual acuity of 6/12 or
Bo
??1y better, the legal requirement for a driver’s license.Twentyseven
e'|c59E (11%) had visual acuity of less than 6/18 (moderate
]NKz5[9D vision impairment). Complications of cataract surgery
nWUau:% caused reduced vision in four of the 27 eyes (15%), or 1.9%
!"'@c of operated eyes. Three of these four eyes had undergone
l>)+HoD intracapsular cataract extraction and the fourth eye had an
|WW'qg]Uu opaque posterior capsule. No one had bilateral vision
x[$:^5V impairment as a result of cataract surgery. Surprisingly, no
m*v@L4t(1 particular demographic factors (such as age, gender, rural
UN:cRH{?* residence, occupation, employment status, health insurance
NU[Wj uLG status, ethnicity) were related to the presence of unoperated
T%**:@}+ cataract.
Htep3Ol3 Conclusions: Although the overall prevalence of cataract is
d!"gb,ec quite high, no particular subgroup is systematically underserviced
;9qwB in terms of cataract surgery. Overall, the results of
Sf
t,
$ cataract surgery are very good, with the majority of eyes
!@>:k3DC& achieving driving vision following cataract extraction.
YW"nPZNPy~ Key words: cataract extraction, health planning, health
>,f5 5 services accessibility, prevalence
mHNqzdaa INTRODUCTION
SnoEi~Da Cataract is the leading cause of blindness worldwide and, in
u#0EZ2># Australia, cataract extractions account for the majority of all
7QaZ|\c ophthalmic procedures.1 Over the period 1985–94, the rate
pH0MVu(W of cataract surgery in Australia was twice as high as would be
r6kQMFA expected from the growth in the elderly population.1
i^eDM.#X Although there have been a number of studies reporting
%3q7i`AZ the prevalence of cataract in various populations,2–6 there is
M,SIs
3 little information about determinants of cataract surgery in
,km`-6.2? the population. A previous survey of Australian ophthalmologists
Qq\hD@Z| showed that patient concern and lifestyle, rather
+b{tk=Q: than visual acuity itself, are the primary factors for referral
:Z]\2(x for cataract surgery.7 This supports prior research which has
S|_lbMZM shown that visual acuity is not a strong predictor of need for
xic&m5j
m cataract surgery.8,9 Elsewhere, socioeconomic status has
&I/C^/F& been shown to be related to cataract surgery rates.10
wA6<BujD To appropriately plan health care services, information is
XMpE|M!c needed about the prevalence of age-related cataract in the
S#|5&SR community as well as the factors associated with cataract
wr2F]1bh@ surgery. The purpose of this study is to quantify the prevalence
kk
aS&r> of any cataract in Australia, to describe the factors
u~27\oj, related to unoperated cataract in the community and to
_"qX6Jc describe the visual outcomes of cataract surgery.
d'p@[1/ METHODS
`R:HMO[ow Study population
>orDw3xC Details about the study methodology for the Visual
QkY;O<Y_ Impairment Project have been published previously.11
$p.0[A(N Briefly, cluster sampling within three strata was employed to
AkBEE recruit subjects aged 40 years and over to participate.
ffh3okyW0 Within the Melbourne Statistical Division, nine pairs of
y-vBC3 census collector districts were randomly selected. Fourteen
5
~xv"S(E} nursing homes within a 5 km radius of these nine test sites
{IQCA-AI were randomly chosen to recruit nursing home residents.
*iujJi Clinical and Experimental Ophthalmology (2000) 28, 77–82
9X87" Original Article
~H`(z zk Operated and unoperated cataract in Australia
$lAhKpdlW Catherine A McCarty PhD, MPH, Mukesh B Nanjan PhD, Hugh R Taylor MD
G+jcR; s Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
_<;westq n Correspondence: Dr Cathy McCarty MPH, Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, 32 Gisborne Street, East Melbourne,
YN5p@b=FX Victoria 3002, Australia. Email:
cathy@cera.unimelb.edu.au m-}6DN 78 McCarty et al.
OEj%cB! Finally, four pairs of census collector districts in four rural
Dq~D4| Victorian communities were randomly selected to recruit rural
l|~SVk| residents. A household census was conducted to identify
1
$rrfg eligible residents aged 40 years and over who had been a
kG]FB.@bG resident at that address for at least 6 months. At the time of
"%{J$o the household census, basic information about age, sex,
Z<6Fq*I country of birth, language spoken at home, education, use of
Lw #vHNf6 corrective spectacles and use of eye care services was collected.
L9(!L$ Eligible residents were then invited to attend a local
7%Ii:5Bp examination site for a more detailed interview and examination.
8i?h{G IMV The study protocol was approved by the Royal Victorian
'P<T,:z? Eye and Ear Hospital Human Research Ethics Committee.
dnUiNs8 Assessment of cataract
P
:D6w){ A standardized ophthalmic examination was performed after
\H$j[
"3 pupil dilatation with one drop of 10% phenylephrine
<)$b=z hydrochloride. Lens opacities were graded clinically at the
@mrGG F time of the examination and subsequently from photos using
G[!Y6c3 the Wilmer cataract photo-grading system.12 Cortical and
5qx$=6PT posterior subcapsular (PSC) opacities were assessed on
4GTB82V$ retroillumination and measured as the proportion (in 1/16)
>\c"U1%E
of pupil circumference occupied by opacity. For this analysis,
^\zf8kPti cortical cataract was defined as 4/16 or greater opacity,
9a0ibN6m PSC cataract was defined as opacity equal to or greater than
;NeN2 |I] 1 mm2 and nuclear cataract was defined as opacity equal to
8q#Be1u<s2 or greater than Wilmer standard 2,12 independent of visual
YXWlg%s acuity. Examples of the minimum opacities defined as cortical,
5(sWV:_2 nuclear and PSC cataract are presented in Figure 1.
A('_.J= Bilateral congenital cataracts or cataracts secondary to
nI6[y)j intraocular inflammation or trauma were excluded from the
>
:
;*3 analysis. Two cases of bilateral secondary cataract and eight
dF/HKBJ cases of bilateral congenital cataract were excluded from the
!K$qh{n analyses.
>*aqYNft A Topcon® SL5 photo slit-lamp (Topcon America Corp.,
XY1eeB- Paramus, NJ, USA) with a 0.1 mm slit beam of 9.0 mm in
E)=X8y height set to an incident angle of 30° was used for examinations.
pZv>{=2hOS Ektachrome® 200 ASA colour slide film (Eastman
)mVpJYt; Kodak Company, Rochester, NY, USA) was used to photograph
!{,
`h< the nuclear opacities. The cortical opacities were
oTqv$IzqP photographed with an Oxford® retroillumination camera
*3>$f.QU (Marcher Enterprises Ltd, Hereford, UK) and T-MAX® 400
BRg(h3 ED film (Eastman Kodak). Photographs were graded separately
M)1?$'Aq by two research assistants and discrepancies were adjudicated
7CKh?> by an independent reviewer. Any discrepancies
T+y3Ph--^ between the clinical grades and the photograph grades were
bq<DW/ resolved. Except in cases where photographs were missing,
#nS
the photograph grades were used in the analyses. Photograph
jg_##Oha grades were available for 4301 (84%) for cortical
6GZzNhz cataract, 4147 (81%) for nuclear cataract and 4303 (84%)
C/{tvY /o for PSC cataract. Cataract status was classified according to
M!
e$h?vB the severity of the opacity in the worse eye.
qd7 86~ Assessment of risk factors
1|c\^;cTkt A standardized questionnaire was used to obtain information
X-&U-S; about education, employment and ethnic background.11
!}gC0dJ Specific information was elicited on the occurrence, duration
Jn>6y:s and treatment of a number of medical conditions,
eaI!}#>R+ including ocular trauma, arthritis, diabetes, gout, hypertension
' N@1+v= and mental illness. Information about the use, dose and
6H\apgHm duration of tobacco, alcohol, analgesics and steriods were
A$9^JF0$ collected, and a food frequency questionnaire was used to
+Xg]@IS-eg determine current consumption of dietary sources of antioxidants
SbLx`]rI and use of vitamin supplements.
l$_Yl&!q$ Data management and statistical analysis
`n#
{} % Data were collected either by direct computer entry with a
S]7RGzFe questionnaire programmed in Paradox© (Carel Corporation,
MU ;
L
7^ Ottawa, Canada) with internal consistency checks, or
R0n#FL^E on self-coding forms. Open-ended responses were coded at
V_&>0P{q a later time. Data that were entered on the self-coded forms
g)<t=+a were entered into a computer with double data entry and
U/e$.K3v reconciliation of any inconsistencies. Data range and consistency
?~;8Y
=O checks were performed on the entire data set.
~
cKmf] SAS© version 6.1 (SAS Institute, Cary, North Carolina) was
jORU+g employed for statistical analyses.
<4gT8kQ$x Ninety-five per cent confidence limits around the agespecific
Wn(pz)+Y rates were calculated according to Cochran13 to
ccUq!1 account for the effect of the cluster sampling. Ninety-five
=+T$
1 per cent confidence limits around age-standardized rates
;_.%S *W\ were calculated according to Breslow and Day.14 The strataspecific
R).?lnS data were weighted according to the 1996
M>pcG.6V Australian Bureau of Statistics census data15 to reflect the
/e^q>>z cataract prevalence in the entire Victorian population.
gg>O:np8 Univariate analyses with Student’s t-tests and chi-squared
rKR2v(c tests were first employed to evaluate risk factors for unoperated
#PzRhanX cataract. Any factors with P < 0.10 were then fitted
[>IAS> into a backwards stepwise logistic regression model. For the
: GZx- Figure 1. Minimum levels of cortical (a), nuclear (b), and posterior subcapsular (c) cataract.
nQ/R,+6h final multivariate models, P < 0.05 was considered statistically
-.8 nEO3 significant. Design effect was assessed through the use
U*.
Wx0QM of cluster-specific models and multivariate models. The
d]JiJgfa% design effect was assumed to be additive and an adjustment
3|=9aM^ x^ made in the variance by adding the variance associated with
.^<4] the design effect prior to constructing the 95% confidence
Y <'T;@ limits.
Gz]p2KBg RESULTS
r sf +dC Study population
-lKk.Y.}r A total of 3271 (83%) of the Melbourne residents, 403
(x{6N^J.t (90%) Melbourne nursing home residents, and 1473 (92%)
ggr\nY rural residents participated. In general, non-participants did
<,%qt_
! not differ from participants.16 The study population was
N`FgjnQ` representative of the Victorian population and Australia as
Y
)kO" a whole.
#
$&!)13 The Melbourne residents ranged in age from 40 to
1epj/bB&