ABSTRACT
Hw]E#S Purpose: To quantify the prevalence of cataract, the outcomes
CJ\a7=*i of cataract surgery and the factors related to
-`~qmRpqY unoperated cataract in Australia.
&J6`Q<U! Methods: Participants were recruited from the Visual
D*%am|QL Impairment Project: a cluster, stratified sample of more than
bQt:=> 5000 Victorians aged 40 years and over. At examination
4k;FZo]S sites interviews, clinical examinations and lens photography
#{8IFA were performed. Cataract was defined in participants who
pbzFzLal had: had previous cataract surgery, cortical cataract greater
W%!(kN&d than 4/16, nuclear greater than Wilmer standard 2, or
$N=&D_Q posterior subcapsular greater than 1 mm2.
:(n<c Results: The participant group comprised 3271 Melbourne
|h]V9= residents, 403 Melbourne nursing home residents and 1473
vA/SrX. rural residents.The weighted rate of any cataract in Victoria
G]'ah1W was 21.5%. The overall weighted rate of prior cataract
#d-({blo< surgery was 3.79%. Two hundred and forty-nine eyes had
5*YoK)2J had prior cataract surgery. Of these 249 procedures, 49
@t9HRL?T~ (20%) were aphakic, 6 (2.4%) had anterior chamber
uY&1[(Pb intraocular lenses and 194 (78%) had posterior chamber
M~:_^B intraocular lenses.Two hundred and eleven of these operated
*-T.xo eyes (85%) had best-corrected visual acuity of 6/12 or
<7^
|@L
6 better, the legal requirement for a driver’s license.Twentyseven
E\[B E<y (11%) had visual acuity of less than 6/18 (moderate
o1.~g'!^ vision impairment). Complications of cataract surgery
3B1\-ry1M caused reduced vision in four of the 27 eyes (15%), or 1.9%
]01`r/->\ of operated eyes. Three of these four eyes had undergone
\Ow
F!~& intracapsular cataract extraction and the fourth eye had an
F9r.DG$} opaque posterior capsule. No one had bilateral vision
;
I>nA6A impairment as a result of cataract surgery. Surprisingly, no
2*NPK} particular demographic factors (such as age, gender, rural
S<nF>JRJa residence, occupation, employment status, health insurance
t+?Bb7p,H status, ethnicity) were related to the presence of unoperated
5|H;%T3_ cataract.
$C[z]}iOi Conclusions: Although the overall prevalence of cataract is
k~tEUsv quite high, no particular subgroup is systematically underserviced
)4g_S?l= in terms of cataract surgery. Overall, the results of
,->ihxf cataract surgery are very good, with the majority of eyes
OgF[= achieving driving vision following cataract extraction.
8+'}` Key words: cataract extraction, health planning, health
J6Ilg@}\ services accessibility, prevalence
Px_8lB/; INTRODUCTION
1w>[ Cataract is the leading cause of blindness worldwide and, in
_^<vp Australia, cataract extractions account for the majority of all
jX7K-L ophthalmic procedures.1 Over the period 1985–94, the rate
fQoAdw of cataract surgery in Australia was twice as high as would be
4E''pW]8 expected from the growth in the elderly population.1
TK5$-6k Although there have been a number of studies reporting
M^kaik the prevalence of cataract in various populations,2–6 there is
FWW4n_74 little information about determinants of cataract surgery in
392V\qtS the population. A previous survey of Australian ophthalmologists
7F"ljkN1S showed that patient concern and lifestyle, rather
>k
@t.PeoV than visual acuity itself, are the primary factors for referral
st w@@GQ for cataract surgery.7 This supports prior research which has
lU1SN/'zx shown that visual acuity is not a strong predictor of need for
#]Vw$X_S cataract surgery.8,9 Elsewhere, socioeconomic status has
|gk*{3~y been shown to be related to cataract surgery rates.10
Q
8]X To appropriately plan health care services, information is
Ec7xwPk needed about the prevalence of age-related cataract in the
?wtKi#k'v# community as well as the factors associated with cataract
\%r#>8c8 surgery. The purpose of this study is to quantify the prevalence
]D6<6OB of any cataract in Australia, to describe the factors
$
DN. related to unoperated cataract in the community and to
,.Gp_BI describe the visual outcomes of cataract surgery.
g!0
j1 METHODS
IsE&k2 SD Study population
B}
qRz Details about the study methodology for the Visual
hTBJ\1
- Impairment Project have been published previously.11
P0UR{tK Briefly, cluster sampling within three strata was employed to
n^'d8Y( recruit subjects aged 40 years and over to participate.
!KV!Tkx h Within the Melbourne Statistical Division, nine pairs of
l"8g9z census collector districts were randomly selected. Fourteen
1XS~b-St nursing homes within a 5 km radius of these nine test sites
2K~v`c*4 were randomly chosen to recruit nursing home residents.
$(&uaDYv Clinical and Experimental Ophthalmology (2000) 28, 77–82
-Ua5anz
B Original Article
)+FnwW Operated and unoperated cataract in Australia
v0'z''KM! Catherine A McCarty PhD, MPH, Mukesh B Nanjan PhD, Hugh R Taylor MD
0Cc3NNdz Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
1drg5 n Correspondence: Dr Cathy McCarty MPH, Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, 32 Gisborne Street, East Melbourne,
}r04*P( Victoria 3002, Australia. Email:
cathy@cera.unimelb.edu.au qRT5|\l 78 McCarty et al.
?r;F'%N= Finally, four pairs of census collector districts in four rural
65B&>`H~ Victorian communities were randomly selected to recruit rural
w[2E
:Nj residents. A household census was conducted to identify
.WglLUJ:Z eligible residents aged 40 years and over who had been a
s#~VN;-I resident at that address for at least 6 months. At the time of
E=.J*7 the household census, basic information about age, sex,
8hV4l'Pa72 country of birth, language spoken at home, education, use of
=>*}qen corrective spectacles and use of eye care services was collected.
9Eh*r@> Eligible residents were then invited to attend a local
w_@6!zm examination site for a more detailed interview and examination.
ml~)7J The study protocol was approved by the Royal Victorian
;&b=>kPlZ Eye and Ear Hospital Human Research Ethics Committee.
*{fZA;<R Assessment of cataract
lz).=N}m A standardized ophthalmic examination was performed after
_=w=!U&W pupil dilatation with one drop of 10% phenylephrine
<95*z @ hydrochloride. Lens opacities were graded clinically at the
"t{D5{q|[k time of the examination and subsequently from photos using
FN0<iL the Wilmer cataract photo-grading system.12 Cortical and
B)DtJf posterior subcapsular (PSC) opacities were assessed on
>wV2` 6 retroillumination and measured as the proportion (in 1/16)
-z/>W+k of pupil circumference occupied by opacity. For this analysis,
&I(3/u cortical cataract was defined as 4/16 or greater opacity,
ZYl*-i&~? PSC cataract was defined as opacity equal to or greater than
uCFpH5> 1 mm2 and nuclear cataract was defined as opacity equal to
(.M &nN'Ce or greater than Wilmer standard 2,12 independent of visual
E-rGOm" m acuity. Examples of the minimum opacities defined as cortical,
(
Qk*B nuclear and PSC cataract are presented in Figure 1.
L{1PCs36c Bilateral congenital cataracts or cataracts secondary to
k1^&;}/f: intraocular inflammation or trauma were excluded from the
!"^//2N+, analysis. Two cases of bilateral secondary cataract and eight
|>p?Cm cases of bilateral congenital cataract were excluded from the
yzCamm4~0 analyses.
6$+F5T A Topcon® SL5 photo slit-lamp (Topcon America Corp.,
^^*dHWHn< Paramus, NJ, USA) with a 0.1 mm slit beam of 9.0 mm in
!_1RQ5]^ height set to an incident angle of 30° was used for examinations.
pu+jw
<7 Ektachrome® 200 ASA colour slide film (Eastman
~p/1
9/ Kodak Company, Rochester, NY, USA) was used to photograph
o7@81QA!e the nuclear opacities. The cortical opacities were
v+2t;PJd2 photographed with an Oxford® retroillumination camera
&14Er,K (Marcher Enterprises Ltd, Hereford, UK) and T-MAX® 400
tsTCZ);( film (Eastman Kodak). Photographs were graded separately
&Sp2['a! by two research assistants and discrepancies were adjudicated
/4-6V
d"8 by an independent reviewer. Any discrepancies
)1!*N)$ between the clinical grades and the photograph grades were
OM7EmMa; resolved. Except in cases where photographs were missing,
|Xk>a7X the photograph grades were used in the analyses. Photograph
h>'Mh;+ grades were available for 4301 (84%) for cortical
V> @+&q cataract, 4147 (81%) for nuclear cataract and 4303 (84%)
4Q(GX.5 for PSC cataract. Cataract status was classified according to
D~JrO]mi the severity of the opacity in the worse eye.
CrI:TB>/" Assessment of risk factors
Tf?|*P A standardized questionnaire was used to obtain information
qUtlh,4) about education, employment and ethnic background.11
c'~6 1HA< Specific information was elicited on the occurrence, duration
:HQQ8uQfb and treatment of a number of medical conditions,
5QUL-*t including ocular trauma, arthritis, diabetes, gout, hypertension
,O/ t6' and mental illness. Information about the use, dose and
N3g\X duration of tobacco, alcohol, analgesics and steriods were
KI{B<S3*Z collected, and a food frequency questionnaire was used to
E#m|Sq determine current consumption of dietary sources of antioxidants
e2l!L*[g and use of vitamin supplements.
{]6Pd`- Data management and statistical analysis
1MnT*w Data were collected either by direct computer entry with a
f/NfvLi(AU questionnaire programmed in Paradox© (Carel Corporation,
%ryYa Ottawa, Canada) with internal consistency checks, or
E1-BB on self-coding forms. Open-ended responses were coded at
'6zD
`Q a later time. Data that were entered on the self-coded forms
L1J~D?q were entered into a computer with double data entry and
{
vOr'j@ reconciliation of any inconsistencies. Data range and consistency
yvp$s checks were performed on the entire data set.
YA[\|I33 SAS© version 6.1 (SAS Institute, Cary, North Carolina) was
QlCs,bT employed for statistical analyses.
r0fxEYze& Ninety-five per cent confidence limits around the agespecific
6_wj,7 rates were calculated according to Cochran13 to
KJ;;825? account for the effect of the cluster sampling. Ninety-five
5:sk&0:@U per cent confidence limits around age-standardized rates
qzt.k^'-^
were calculated according to Breslow and Day.14 The strataspecific
`8sC>)lrwu data were weighted according to the 1996
7uW=f kxT Australian Bureau of Statistics census data15 to reflect the
Ods/1 KW cataract prevalence in the entire Victorian population.
nkAS]sC Univariate analyses with Student’s t-tests and chi-squared
vQ",rP% tests were first employed to evaluate risk factors for unoperated
ev"f@y9Do cataract. Any factors with P < 0.10 were then fitted
bs9X4n5 into a backwards stepwise logistic regression model. For the
j}fu|- Figure 1. Minimum levels of cortical (a), nuclear (b), and posterior subcapsular (c) cataract.
3yw`%$d5 final multivariate models, P < 0.05 was considered statistically
I->
BDNk significant. Design effect was assessed through the use
gql^Inx< of cluster-specific models and multivariate models. The
z
iTE*rNJ design effect was assumed to be additive and an adjustment
BDiN*.w5 made in the variance by adding the variance associated with
/fDXO;tN the design effect prior to constructing the 95% confidence
.Gq]Mrim9G limits.
= Y`e?\#` RESULTS
G~nQR
qv Study population
VSLi{=# A total of 3271 (83%) of the Melbourne residents, 403
,|G~PC8 (90%) Melbourne nursing home residents, and 1473 (92%)
6O0CF}B* rural residents participated. In general, non-participants did
RoYwZX~ not differ from participants.16 The study population was
wx[Y2lUh6 representative of the Victorian population and Australia as
G A+#'R
a whole.
LzGSN The Melbourne residents ranged in age from 40 to
i8|0z
I 98 years (mean = 59) and 1511 (46%) were male. The
ZXH{9hxd Melbourne nursing home residents ranged in age from 46 to
dk>qTY+j5 101 years (mean = 82) and 85 (21%) were men. The rural
XkRPD residents ranged in age from 40 to 103 years (mean = 60)
h6~H5X and 701 (47.5%) were men.
'gv~M_ Prevalence of cataract and prior cataract surgery
26B+qXEt As would be expected, the rate of any cataract increases
9gQ
]!Oq dramatically with age (Table 1). The weighted rate of any
q>f|1Pf cataract in Victoria was 21.5% (95% CL 18.1, 24.9).
L <W2a( Although the rates varied somewhat between the three
2`P=ekF] strata, they were not significantly different as the 95% confidence
v4Mn@e_#c limits overlapped. The per cent of cataractous eyes
_MxKfah' with best-corrected visual acuity of less than 6/12 was 12.5%
`/RcE.5n\@ (65/520) for cortical cataract, 18% for nuclear cataract
|{ TVW (97/534) and 14.4% (27/187) for PSC cataract. Cataract
/5N`Euw surgery also rose dramatically with age. The overall
J7FzOwd1h weighted rate of prior cataract surgery in Victoria was
|* v w( 3.79% (95% CL 2.97, 4.60) (Table 2).
qW
2'?B3< Risk factors for unoperated cataract
n7VQi+i' Cases of cataract that had not been removed were classified
xua
E\*m as unoperated cataract. Risk factor analyses for unoperated
RH~I/4e cataract were not performed with the nursing home residents
AR3v,eOs as information about risk factor exposure was not
wq:"/2p1 available for this cohort. The following factors were assessed
=O??W8u in relation to unoperated cataract: age, sex, residence
iCIU'yI (urban/rural), language spoken at home (a measure of ethnic
rcUJOI integration), country of birth, parents’ country of birth (a
?.Lq
`~T` measure of ethnicity), years since migration, education, use
&`I 7aP| of ophthalmic services, use of optometric services, private
):Pzsz7 health insurance status, duration of distance glasses use,
ypLt6(1j% glaucoma, age-related maculopathy and employment status.
uWjEyxPv{ In this cross sectional study it was not possible to assess the
^SWV!rrg level of visual acuity that would predict a patient’s having
)R6-]TkA_ cataract surgery, as visual acuity data prior to cataract
]S7>=S surgery were not available.
FO{?Z%& ; The significant risk factors for unoperated cataract in univariate
QC<O=<$Q[ analyses were related to: whether a participant had
P2fiK ever seen an optometrist, seen an ophthalmologist or been
kzmw1*J diagnosed with glaucoma; and participants’ employment
EI8KK o * status (currently employed) and age. These significant
a St:G*a" factors were placed in a backwards stepwise logistic regression
O&evv8 6L model. The factors that remained significantly related
X86r`} to unoperated cataract were whether participants had ever
~S~4pK seen an ophthalmologist, seen an optometrist and been
qCy
SL lp0 diagnosed with glaucoma. None of the demographic factors
E_-g<Cw were associated with unoperated cataract in the multivariate
_j2q model.
K;*B$2Z#k The per cent of participants with unoperated cataract
ImsyyeY] who said that they were dissatisfied or very dissatisfied with
q$kx/6=k Operated and unoperated cataract in Australia 79
$fAZ^ Table 1. Prevalence of any cataracta (excluding previous cataract surgery) by age, gender and cohort
Np@
RK1} Age group Sex Urban Rural Nursing home Weighted total
hH_\C.bL (years) (%) (%) (%)
09J,!NN 40–49 Male 2.56 4.04 0.00 3.00 (1.91, 4.08)
sI`oz|$ Female 2.61 1.70 0.00 2.36 (1.61, 3.10)
G;AJBs>Y} 50–59 Male 7.69 6.94 0.00 7.47 (5.80, 9.15)
]23+ d/ Female 6.67 7.56 0.00 6.92 (5.60, 8.24)
#D^(dz* 60–69 Male 20.7 25.0 10.0 22.0 (18.1, 26.0)
AZva Female 27.9 35.7 37.5 30.3 (26.0, 34.7)
y*T@_on5 70–79 Male 43.1 58.7 39.1 48.1 (41.2, 55.1)
5`)[FCQ Female 58.6 66.2 55.6 61.0 (56.0, 65.9)
nU/x,W[} 80–89 Male 74.0 89.3 92.0 79.3 (72.3, 86.3)
uQ3W = Female 91.9 97.0 80.2 92.6 (86.4, 98.8)
;aDYw [ 90 + Male 100.0 100.0 75.0 98.8 (96.2, 100.0)
zcOG[- Female 100.0 100.0 93.8 98.6 (97.0, 100.0)
/2Bf6 Age-standardized
"@L|Z6U( (95% CL) Combined 19.7 (16.3, 23.1) 23.2 (16.1, 30.2) 16.5 (2.06, 30.9) 21.5 (18.1, 25.0)
vu3zZMl aCortical > 4/16, nuclear > standard 2, posterior subcapsular > 1 mm2
dG)}H_ their current vision was 30% (290/683), compared with 27%
+kx#"L: (26/95) of participants with prior cataract surgery (chisquared,
4okZ 1 d.f. = 0.25, P = 0.62).
/J!~0~F Outcomes of cataract surgery
v,c;dlg_ Two hundred and forty-nine eyes had undergone prior
/gP"X1. cataract surgery. Of these 249 operated eyes, 49 (20%) were
u(~( +1W left aphakic, 6 (2.4%) had anterior chamber intraocular
p*|Ct lenses and 194 (78%) had posterior chamber intraocular
9G)fJr[c lenses. The rate of capsulotomy in the eyes with intact
BP=<TRp. posterior capsules was 36% (73/202). Fifteen per cent of
\N.Bx
eyes (17/114) with a clear posterior capsule had bestcorrected
=W"9
a\m visual acuity of less than 6/12 compared with 43%
vY]7oX+ of eyes (6/14) with opaque capsules, and 15% of eyes
D:XjJMW3r (11/73) with prior capsulotomies (chi-squared, 2 d.f. = 7.21,
8[x{]l[ P = 0.027).
O7yIFqI=/ The percentage of eyes with best-corrected visual acuity
n8o(>?Kw of 6/12 or better was 96% (302/314) for eyes without
y)T|1) cataract, 88% (1417/1609) for eyes with prevalent cataract
s$xm and 85% (211/249) for eyes with operated cataract (chisquared,
1(qL),F; 2 d.f. = 22.3), P < 0.001). Twenty-seven of the
5)i+x- operated eyes (11%) had visual acuities of less than 6/18
zZiga q" (moderate vision impairment) (Fig. 2). A cause of this
du&9mOrr moderate visual impairment (but not the only cause) in four
hz rS_v (15%) eyes was secondary to cataract surgery. Three of these
BoofJm four eyes had undergone intracapsular cataract extraction
%
{A%SDh and the fourth eye had an opaque posterior capsule. No one
t^7}j4lk had bilateral vision impairment as a result of their cataract
9%DLdc\z; surgery.
-Hg,:re2 DISCUSSION
#./8inbG To our knowledge, this is the first paper to systematically
h/7_I uD assess the prevalence of current cataract, previous cataract
OGPrjL+ surgery, predictors of unoperated cataract and the outcomes
[~k!wipK of cataract surgery in a population-based sample. The Visual
\
+)AQ!E Impairment Project is unique in that the sampling frame and
{#&j