ABSTRACT
w$j{Hp6m Purpose: To quantify the prevalence of cataract, the outcomes
RNTa XR+Zn of cataract surgery and the factors related to
yHNuU)Ft unoperated cataract in Australia.
1a$IrQE Methods: Participants were recruited from the Visual
r?p[3JJ;mG Impairment Project: a cluster, stratified sample of more than
(WRMaI72( 5000 Victorians aged 40 years and over. At examination
+~Tu0?{Z 0 sites interviews, clinical examinations and lens photography
?^9BMQ+ were performed. Cataract was defined in participants who
B>z?ClH$R had: had previous cataract surgery, cortical cataract greater
o0ZBi|U\4 than 4/16, nuclear greater than Wilmer standard 2, or
zrRFn `B posterior subcapsular greater than 1 mm2.
h?Nek+1' Results: The participant group comprised 3271 Melbourne
l{$[}< residents, 403 Melbourne nursing home residents and 1473
(}smW_`5 rural residents.The weighted rate of any cataract in Victoria
83 I-X95 was 21.5%. The overall weighted rate of prior cataract
>2b`\Q*< surgery was 3.79%. Two hundred and forty-nine eyes had
`G!M>h@ had prior cataract surgery. Of these 249 procedures, 49
^lj7( (20%) were aphakic, 6 (2.4%) had anterior chamber
Wd8Ru/ intraocular lenses and 194 (78%) had posterior chamber
>&U@f intraocular lenses.Two hundred and eleven of these operated
=']3(6* eyes (85%) had best-corrected visual acuity of 6/12 or
Y$<D9fs3 better, the legal requirement for a driver’s license.Twentyseven
iWA|8$u4gm (11%) had visual acuity of less than 6/18 (moderate
kWhr1wR1 vision impairment). Complications of cataract surgery
~#PLAP3- caused reduced vision in four of the 27 eyes (15%), or 1.9%
!'G~k+ of operated eyes. Three of these four eyes had undergone
J !HjeZ intracapsular cataract extraction and the fourth eye had an
*?t%0){ opaque posterior capsule. No one had bilateral vision
Kj3?ve~ impairment as a result of cataract surgery. Surprisingly, no
hyg8wI particular demographic factors (such as age, gender, rural
=0qpVFvU residence, occupation, employment status, health insurance
,q#0hy%5/ status, ethnicity) were related to the presence of unoperated
A+getdr cataract.
g}x(hF
Conclusions: Although the overall prevalence of cataract is
-WJ?:?' quite high, no particular subgroup is systematically underserviced
?K_
'@ in terms of cataract surgery. Overall, the results of
X4|4QgY cataract surgery are very good, with the majority of eyes
-0C@hM,wm achieving driving vision following cataract extraction.
T-_"|-k}P% Key words: cataract extraction, health planning, health
2]cRXJ7h services accessibility, prevalence
p-GAe,2q INTRODUCTION
z (?=Iv3 Cataract is the leading cause of blindness worldwide and, in
-7
U|a/ Australia, cataract extractions account for the majority of all
&;&ho+qD ophthalmic procedures.1 Over the period 1985–94, the rate
8s{?v&p of cataract surgery in Australia was twice as high as would be
lQ' GX9hN@ expected from the growth in the elderly population.1
v\tEVhm Although there have been a number of studies reporting
kF"@Ngv. the prevalence of cataract in various populations,2–6 there is
9iUr nG* little information about determinants of cataract surgery in
)3Z ^h<"j the population. A previous survey of Australian ophthalmologists
RTh`ENCKR showed that patient concern and lifestyle, rather
h:Gu`+D>W than visual acuity itself, are the primary factors for referral
G+UMBn for cataract surgery.7 This supports prior research which has
eqw0]U\pv shown that visual acuity is not a strong predictor of need for
l
vMlL5t cataract surgery.8,9 Elsewhere, socioeconomic status has
L>yJ been shown to be related to cataract surgery rates.10
x^4xq#Bb7 To appropriately plan health care services, information is
(0YZZ93 needed about the prevalence of age-related cataract in the
.sC?7O= community as well as the factors associated with cataract
Y2o?gug surgery. The purpose of this study is to quantify the prevalence
7Mb#O_eh of any cataract in Australia, to describe the factors
(q+)'H%iK related to unoperated cataract in the community and to
S}p4iE"n describe the visual outcomes of cataract surgery.
/x_o!<M METHODS
4RSHZAJg Study population
h$4Hw+Yxs] Details about the study methodology for the Visual
%?e& WLS Impairment Project have been published previously.11
*%{gYpn Briefly, cluster sampling within three strata was employed to
h4q|lA6!k8 recruit subjects aged 40 years and over to participate.
.pvi!NnL- Within the Melbourne Statistical Division, nine pairs of
8GvJ0Jq}U census collector districts were randomly selected. Fourteen
j@YU|-\qh nursing homes within a 5 km radius of these nine test sites
f7m%|v! were randomly chosen to recruit nursing home residents.
!O `(JSoG Clinical and Experimental Ophthalmology (2000) 28, 77–82
yzqVz_Fi*W Original Article
uc;8 K,[t Operated and unoperated cataract in Australia
:xtXQza"- Catherine A McCarty PhD, MPH, Mukesh B Nanjan PhD, Hugh R Taylor MD
N5a*7EJv+ Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
c-B
cA n Correspondence: Dr Cathy McCarty MPH, Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, 32 Gisborne Street, East Melbourne,
-r-k_6QP Victoria 3002, Australia. Email:
cathy@cera.unimelb.edu.au W[Ls|<Q 78 McCarty et al.
qWQ/'M Finally, four pairs of census collector districts in four rural
C?lcGt!H Victorian communities were randomly selected to recruit rural
9I6a"PGDb residents. A household census was conducted to identify
.Y&)4+ckL eligible residents aged 40 years and over who had been a
;M)Q
wF1 resident at that address for at least 6 months. At the time of
r"P|dlV- the household census, basic information about age, sex,
r>o63Q: country of birth, language spoken at home, education, use of
*MKO
I' corrective spectacles and use of eye care services was collected.
vEJWFoeEFm Eligible residents were then invited to attend a local
C
uB`CI examination site for a more detailed interview and examination.
-*1J f& The study protocol was approved by the Royal Victorian
@7IIM{ Eye and Ear Hospital Human Research Ethics Committee.
KrQ1GepJ Assessment of cataract
s.$3j$vT 8 A standardized ophthalmic examination was performed after
E7rDa1 pupil dilatation with one drop of 10% phenylephrine
<0Xf9a8> hydrochloride. Lens opacities were graded clinically at the
E|iQc8gr& time of the examination and subsequently from photos using
.+$Q<L the Wilmer cataract photo-grading system.12 Cortical and
9Z4nAc posterior subcapsular (PSC) opacities were assessed on
]s<[D$ <, retroillumination and measured as the proportion (in 1/16)
p M4 :#%V of pupil circumference occupied by opacity. For this analysis,
|-:()yxs cortical cataract was defined as 4/16 or greater opacity,
h9}+l PSC cataract was defined as opacity equal to or greater than
]Sf]J4eQ 1 mm2 and nuclear cataract was defined as opacity equal to
(A9Fhun or greater than Wilmer standard 2,12 independent of visual
+^60T$ acuity. Examples of the minimum opacities defined as cortical,
]cHgleHQ nuclear and PSC cataract are presented in Figure 1.
]d$8f
Bilateral congenital cataracts or cataracts secondary to
j()7_ intraocular inflammation or trauma were excluded from the
ZMQZs~;~d analysis. Two cases of bilateral secondary cataract and eight
6'k<+IR cases of bilateral congenital cataract were excluded from the
{$0mwAOH " analyses.
<cps2*' A Topcon® SL5 photo slit-lamp (Topcon America Corp.,
Ni9/}bb
Paramus, NJ, USA) with a 0.1 mm slit beam of 9.0 mm in
*#,7d"6W5 height set to an incident angle of 30° was used for examinations.
-*1d! Ektachrome® 200 ASA colour slide film (Eastman
UXJeAE- Kodak Company, Rochester, NY, USA) was used to photograph
=W(Q34 the nuclear opacities. The cortical opacities were
$*^7iT4q_t photographed with an Oxford® retroillumination camera
'$i:
2mn, (Marcher Enterprises Ltd, Hereford, UK) and T-MAX® 400
D+rxT:
d film (Eastman Kodak). Photographs were graded separately
X-bcQ@Oj by two research assistants and discrepancies were adjudicated
|mZxfI by an independent reviewer. Any discrepancies
KI"#f$2& between the clinical grades and the photograph grades were
~[t[y~Hup resolved. Except in cases where photographs were missing,
h79}qU the photograph grades were used in the analyses. Photograph
Vr3Zu{&2 grades were available for 4301 (84%) for cortical
"Wct({n cataract, 4147 (81%) for nuclear cataract and 4303 (84%)
W: z6Koc0 for PSC cataract. Cataract status was classified according to
j\eI0b @* the severity of the opacity in the worse eye.
'g}! Assessment of risk factors
sA+ }TNhq A standardized questionnaire was used to obtain information
Yj&F;_~ about education, employment and ethnic background.11
k
R?qb6 Specific information was elicited on the occurrence, duration
>xN
.F/[K and treatment of a number of medical conditions,
) ;EBz including ocular trauma, arthritis, diabetes, gout, hypertension
on4HKeO and mental illness. Information about the use, dose and
`aOFs+<) duration of tobacco, alcohol, analgesics and steriods were
s
n8Q
k=K collected, and a food frequency questionnaire was used to
D(~U6SR determine current consumption of dietary sources of antioxidants
f[]dfLS"W and use of vitamin supplements.
.#EF
LXs Data management and statistical analysis
!Lu2 Data were collected either by direct computer entry with a
Pd8![Z3 questionnaire programmed in Paradox© (Carel Corporation,
n*h)'8`Ut Ottawa, Canada) with internal consistency checks, or
4j* on self-coding forms. Open-ended responses were coded at
W~)}xy a later time. Data that were entered on the self-coded forms
&eJfGt5 were entered into a computer with double data entry and
%[GsD9_- reconciliation of any inconsistencies. Data range and consistency
^vZS
UfS checks were performed on the entire data set.
91/Q9xY SAS© version 6.1 (SAS Institute, Cary, North Carolina) was
\<bx[,? employed for statistical analyses.
&w\{TZ{ Ninety-five per cent confidence limits around the agespecific
9p]QM)M rates were calculated according to Cochran13 to
Usvl}{L[ account for the effect of the cluster sampling. Ninety-five
-uS!\ per cent confidence limits around age-standardized rates
YqscZ(L:y were calculated according to Breslow and Day.14 The strataspecific
9i:L&d
N data were weighted according to the 1996
Y_liA Australian Bureau of Statistics census data15 to reflect the
7^avpf)> cataract prevalence in the entire Victorian population.
-E[Kml~U Univariate analyses with Student’s t-tests and chi-squared
O2
V tests were first employed to evaluate risk factors for unoperated
jRa43ck cataract. Any factors with P < 0.10 were then fitted
PrqlTT}Px into a backwards stepwise logistic regression model. For the
&$+AXzn Figure 1. Minimum levels of cortical (a), nuclear (b), and posterior subcapsular (c) cataract.
x>K Or,f final multivariate models, P < 0.05 was considered statistically
1C+13LE$U significant. Design effect was assessed through the use
2DA]i5
of cluster-specific models and multivariate models. The
A
I2)
g1m design effect was assumed to be additive and an adjustment
D\v+wp. made in the variance by adding the variance associated with
}FROB/ the design effect prior to constructing the 95% confidence
2k~l$p>CN! limits.
z(O Nv#}p RESULTS
&u
."A3( Study population
T=DbBy0- A total of 3271 (83%) of the Melbourne residents, 403
qz_7%c]K[ (90%) Melbourne nursing home residents, and 1473 (92%)
_;S-x rural residents participated. In general, non-participants did
k=$TGqQY? not differ from participants.16 The study population was
,L2ZinU: representative of the Victorian population and Australia as
|l^uEtG a whole.
XT%nbh&y The Melbourne residents ranged in age from 40 to
CZwXTHe 98 years (mean = 59) and 1511 (46%) were male. The
#lo6c;*m5 Melbourne nursing home residents ranged in age from 46 to
Y1\ }5k{> 101 years (mean = 82) and 85 (21%) were men. The rural
B:Oa}/H
residents ranged in age from 40 to 103 years (mean = 60)
|*xA8&/ and 701 (47.5%) were men.
WDYeOtc Prevalence of cataract and prior cataract surgery
}0*@fO As would be expected, the rate of any cataract increases
`g?Negt\v dramatically with age (Table 1). The weighted rate of any
xj)F55e? cataract in Victoria was 21.5% (95% CL 18.1, 24.9).
O/(`S<iip Although the rates varied somewhat between the three
R%WCH?B<} strata, they were not significantly different as the 95% confidence
k
.;
j limits overlapped. The per cent of cataractous eyes
wU36sCo with best-corrected visual acuity of less than 6/12 was 12.5%
Q$W (65/520) for cortical cataract, 18% for nuclear cataract
SHxNr(wJ<Q (97/534) and 14.4% (27/187) for PSC cataract. Cataract
eQm1cgMdz surgery also rose dramatically with age. The overall
;8&3 dm] weighted rate of prior cataract surgery in Victoria was
|Zpfq63W 3.79% (95% CL 2.97, 4.60) (Table 2).
(,\+tr8r8 Risk factors for unoperated cataract
Jt<_zn_FG Cases of cataract that had not been removed were classified
.VJMz4$]
O as unoperated cataract. Risk factor analyses for unoperated
-Cpl?Io`r5 cataract were not performed with the nursing home residents
Yl
Q=5u^+ as information about risk factor exposure was not
=o(5_S.u; available for this cohort. The following factors were assessed
X7MM2V in relation to unoperated cataract: age, sex, residence
{6|G@""O (urban/rural), language spoken at home (a measure of ethnic
HZB>{O
integration), country of birth, parents’ country of birth (a
2;`1h[,-^ measure of ethnicity), years since migration, education, use
[ ({nj` of ophthalmic services, use of optometric services, private
2#]#sZmk health insurance status, duration of distance glasses use,
^zmG0EH, glaucoma, age-related maculopathy and employment status.
/4V#C- In this cross sectional study it was not possible to assess the
J?1 uKR level of visual acuity that would predict a patient’s having
wk D^r(hiH cataract surgery, as visual acuity data prior to cataract
jXx<`I+] surgery were not available.
rQs
)O<jl The significant risk factors for unoperated cataract in univariate
[A~xy'T analyses were related to: whether a participant had
.t-4o<7 3 ever seen an optometrist, seen an ophthalmologist or been
BLdvyVFx diagnosed with glaucoma; and participants’ employment
%6,SKg p status (currently employed) and age. These significant
qvsd5P eCO factors were placed in a backwards stepwise logistic regression
OA1uY83" model. The factors that remained significantly related
Ecefi
pG to unoperated cataract were whether participants had ever
\;3~a9q% seen an ophthalmologist, seen an optometrist and been
py!|\00} diagnosed with glaucoma. None of the demographic factors
NjScc%@y were associated with unoperated cataract in the multivariate
Ad8n<zt| model.
bKY7/w<dP The per cent of participants with unoperated cataract
wC+u73599 who said that they were dissatisfied or very dissatisfied with
XGWSdPJLr Operated and unoperated cataract in Australia 79
a=9:[ Table 1. Prevalence of any cataracta (excluding previous cataract surgery) by age, gender and cohort
4<Utmr Age group Sex Urban Rural Nursing home Weighted total
VcO0sa f` (years) (%) (%) (%)
)e+>w=t 40–49 Male 2.56 4.04 0.00 3.00 (1.91, 4.08)
F=e8 IUr Female 2.61 1.70 0.00 2.36 (1.61, 3.10)
zuad~%D<I 50–59 Male 7.69 6.94 0.00 7.47 (5.80, 9.15)
?m}s4a Female 6.67 7.56 0.00 6.92 (5.60, 8.24)
m)t;9J5 60–69 Male 20.7 25.0 10.0 22.0 (18.1, 26.0)
]"hFC<w Female 27.9 35.7 37.5 30.3 (26.0, 34.7)
KNvZm;Q6 70–79 Male 43.1 58.7 39.1 48.1 (41.2, 55.1)
@ $ ;q; Female 58.6 66.2 55.6 61.0 (56.0, 65.9)
U0y% u 80–89 Male 74.0 89.3 92.0 79.3 (72.3, 86.3)
:'-/NtV)o? Female 91.9 97.0 80.2 92.6 (86.4, 98.8)
Eqd<