ABSTRACT
6GAEQ] Purpose: To quantify the prevalence of cataract, the outcomes
VSO(DCr"L of cataract surgery and the factors related to
Bs3&yEq( unoperated cataract in Australia.
xGOmvn^lQ Methods: Participants were recruited from the Visual
OtAAzc!dQ Impairment Project: a cluster, stratified sample of more than
BSkmFd(* 5000 Victorians aged 40 years and over. At examination
v\(6uej^ sites interviews, clinical examinations and lens photography
q+qF;7dN@ were performed. Cataract was defined in participants who
v"Bm4+c&0 had: had previous cataract surgery, cortical cataract greater
uu-M7>+ than 4/16, nuclear greater than Wilmer standard 2, or
uQ
]ZMc posterior subcapsular greater than 1 mm2.
~mHrgx
Q- Results: The participant group comprised 3271 Melbourne
N:KM8PZ&~ residents, 403 Melbourne nursing home residents and 1473
w$]wd`N} rural residents.The weighted rate of any cataract in Victoria
1"t9x. was 21.5%. The overall weighted rate of prior cataract
mxH63$R surgery was 3.79%. Two hundred and forty-nine eyes had
)`<&~>qp had prior cataract surgery. Of these 249 procedures, 49
D0_CDdW%7 (20%) were aphakic, 6 (2.4%) had anterior chamber
non5e)w3@ intraocular lenses and 194 (78%) had posterior chamber
2.{zfr intraocular lenses.Two hundred and eleven of these operated
7#&Q-3\: eyes (85%) had best-corrected visual acuity of 6/12 or
4F -<j! better, the legal requirement for a driver’s license.Twentyseven
UZ-pN_!Z: (11%) had visual acuity of less than 6/18 (moderate
H7drDw vision impairment). Complications of cataract surgery
hZ|0<u caused reduced vision in four of the 27 eyes (15%), or 1.9%
=~
,2E;#X of operated eyes. Three of these four eyes had undergone
2#qcYU intracapsular cataract extraction and the fourth eye had an
#l* w=D? opaque posterior capsule. No one had bilateral vision
all2?neK impairment as a result of cataract surgery. Surprisingly, no
J
}bLp
Z particular demographic factors (such as age, gender, rural
%ol1WG 9 residence, occupation, employment status, health insurance
Oku7&L1 status, ethnicity) were related to the presence of unoperated
Q7zpu/5? cataract.
_K!)0p Conclusions: Although the overall prevalence of cataract is
z X+i2, quite high, no particular subgroup is systematically underserviced
gL@]p in terms of cataract surgery. Overall, the results of
y\9#"=+ cataract surgery are very good, with the majority of eyes
4kK_S.& achieving driving vision following cataract extraction.
^%\MOjSN Key words: cataract extraction, health planning, health
&-My[t services accessibility, prevalence
A^|~>9 INTRODUCTION
=<TJ[,h
et Cataract is the leading cause of blindness worldwide and, in
f"4w@X2F Australia, cataract extractions account for the majority of all
_$ 8:\[J ophthalmic procedures.1 Over the period 1985–94, the rate
ra@CouR^c{ of cataract surgery in Australia was twice as high as would be
`0+-:sXZ6
expected from the growth in the elderly population.1
pUu<0a^ Although there have been a number of studies reporting
w)R5@
@C* the prevalence of cataract in various populations,2–6 there is
g">^#^hBE little information about determinants of cataract surgery in
YPKB4p# the population. A previous survey of Australian ophthalmologists
,nV4%Aa showed that patient concern and lifestyle, rather
9.9B#? than visual acuity itself, are the primary factors for referral
%z~kHL for cataract surgery.7 This supports prior research which has
uA t{WDHm shown that visual acuity is not a strong predictor of need for
e)XnS ' cataract surgery.8,9 Elsewhere, socioeconomic status has
;R@D been shown to be related to cataract surgery rates.10
U+["b-c To appropriately plan health care services, information is
eq<!
needed about the prevalence of age-related cataract in the
yGV>22vv
M community as well as the factors associated with cataract
b9v<Jk surgery. The purpose of this study is to quantify the prevalence
v}IhO~`uEq of any cataract in Australia, to describe the factors
V:+z 3)qF related to unoperated cataract in the community and to
Pl2eDv-y describe the visual outcomes of cataract surgery.
y(^\]-fE METHODS
eYu 0") Study population
YJ~mcaw Details about the study methodology for the Visual
!*?9n^PaF Impairment Project have been published previously.11
N8J(RR9O Briefly, cluster sampling within three strata was employed to
y3PrLBTz recruit subjects aged 40 years and over to participate.
B`jq"[w]- Within the Melbourne Statistical Division, nine pairs of
ki1j~q census collector districts were randomly selected. Fourteen
9^nRwo
nursing homes within a 5 km radius of these nine test sites
7QoMroR were randomly chosen to recruit nursing home residents.
Bx5kqHp^1 Clinical and Experimental Ophthalmology (2000) 28, 77–82
]M'~uTf Original Article
]IzD` Operated and unoperated cataract in Australia
V\l@_%D[(v Catherine A McCarty PhD, MPH, Mukesh B Nanjan PhD, Hugh R Taylor MD
- leYR`P Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
Q7tvpU n Correspondence: Dr Cathy McCarty MPH, Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, 32 Gisborne Street, East Melbourne,
qOnGP{ Victoria 3002, Australia. Email:
cathy@cera.unimelb.edu.au ?zbW z=nq 78 McCarty et al.
.*.eY?,V Finally, four pairs of census collector districts in four rural
!+QfQghAT Victorian communities were randomly selected to recruit rural
qV/>d', residents. A household census was conducted to identify
Z_Y'#5o# eligible residents aged 40 years and over who had been a
PrA(==FX/ resident at that address for at least 6 months. At the time of
evNe6J3 the household census, basic information about age, sex,
/H3w7QU
country of birth, language spoken at home, education, use of
j2.7b1s corrective spectacles and use of eye care services was collected.
,LxkdV Eligible residents were then invited to attend a local
bX`Gv+ examination site for a more detailed interview and examination.
y\Utm$)j The study protocol was approved by the Royal Victorian
r9L--#=z Eye and Ear Hospital Human Research Ethics Committee.
PL
3hrI 5 Assessment of cataract
^H{YLO A standardized ophthalmic examination was performed after
=9,^Tu| pupil dilatation with one drop of 10% phenylephrine
a(ITv roM/ hydrochloride. Lens opacities were graded clinically at the
2gMG7%d time of the examination and subsequently from photos using
<V Rb the Wilmer cataract photo-grading system.12 Cortical and
=6"5kz10 posterior subcapsular (PSC) opacities were assessed on
zNdkwj p+ retroillumination and measured as the proportion (in 1/16)
(Cfb8\~ of pupil circumference occupied by opacity. For this analysis,
ela^L_N hF cortical cataract was defined as 4/16 or greater opacity,
"k{so',7z PSC cataract was defined as opacity equal to or greater than
:Jv5Flxl 1 mm2 and nuclear cataract was defined as opacity equal to
o[iN/ or greater than Wilmer standard 2,12 independent of visual
js@L%1r#L acuity. Examples of the minimum opacities defined as cortical,
79exZ7| nuclear and PSC cataract are presented in Figure 1.
8T6N
G!/ Bilateral congenital cataracts or cataracts secondary to
$~W5! m intraocular inflammation or trauma were excluded from the
#kq!{5, analysis. Two cases of bilateral secondary cataract and eight
3}F>t{FDk cases of bilateral congenital cataract were excluded from the
zyUS$g]& analyses.
6=;(~k&x9: A Topcon® SL5 photo slit-lamp (Topcon America Corp.,
H"6x/&s.=k Paramus, NJ, USA) with a 0.1 mm slit beam of 9.0 mm in
G8klW
ZAJ height set to an incident angle of 30° was used for examinations.
'wG1un;t Ektachrome® 200 ASA colour slide film (Eastman
"QxULiw Kodak Company, Rochester, NY, USA) was used to photograph
C&MqH.K the nuclear opacities. The cortical opacities were
Z?!AJY photographed with an Oxford® retroillumination camera
VN!nef
(Marcher Enterprises Ltd, Hereford, UK) and T-MAX® 400
Ui`{U film (Eastman Kodak). Photographs were graded separately
~uty<fP by two research assistants and discrepancies were adjudicated
HbsNF~;
by an independent reviewer. Any discrepancies
)`f-qTe between the clinical grades and the photograph grades were
>19s:+ resolved. Except in cases where photographs were missing,
"8ellKh the photograph grades were used in the analyses. Photograph
n9}BT^4 v grades were available for 4301 (84%) for cortical
_#:7S
sJ cataract, 4147 (81%) for nuclear cataract and 4303 (84%)
pTwzVz~ for PSC cataract. Cataract status was classified according to
BOw[*hM the severity of the opacity in the worse eye.
9$;5J Assessment of risk factors
sIgTSdk A standardized questionnaire was used to obtain information
T:X* about education, employment and ethnic background.11
`@],J Specific information was elicited on the occurrence, duration
otR7E+*3 and treatment of a number of medical conditions,
[07E-TT2U including ocular trauma, arthritis, diabetes, gout, hypertension
M?"4{ and mental illness. Information about the use, dose and
z}u`45W+ duration of tobacco, alcohol, analgesics and steriods were
ISs&1`Y collected, and a food frequency questionnaire was used to
t8EI"| determine current consumption of dietary sources of antioxidants
S
W%>8 and use of vitamin supplements.
D!,5j_,j% Data management and statistical analysis
Q:megU'u Data were collected either by direct computer entry with a
I!*P' {lh questionnaire programmed in Paradox© (Carel Corporation,
]A%3\)r Ottawa, Canada) with internal consistency checks, or
fGlvum on self-coding forms. Open-ended responses were coded at
mB_?N $K a later time. Data that were entered on the self-coded forms
EtN, were entered into a computer with double data entry and
a~0 ~Y y reconciliation of any inconsistencies. Data range and consistency
%u66H2 checks were performed on the entire data set.
M>
WWP3 SAS© version 6.1 (SAS Institute, Cary, North Carolina) was
q=5aHH% | employed for statistical analyses.
@e3+Gs Ninety-five per cent confidence limits around the agespecific
*mp:#' rates were calculated according to Cochran13 to
3Ji
zv
,? account for the effect of the cluster sampling. Ninety-five
&@oI/i&0B per cent confidence limits around age-standardized rates
q@bye4Ry%W were calculated according to Breslow and Day.14 The strataspecific
6I"KomJ9 data were weighted according to the 1996
/e>%yq<9B Australian Bureau of Statistics census data15 to reflect the
>o1dc* cataract prevalence in the entire Victorian population.
$TXiWW+ Univariate analyses with Student’s t-tests and chi-squared
g,JfT^ tests were first employed to evaluate risk factors for unoperated
qo3+=*"V cataract. Any factors with P < 0.10 were then fitted
pV ^+X} into a backwards stepwise logistic regression model. For the
M@{?#MkS% Figure 1. Minimum levels of cortical (a), nuclear (b), and posterior subcapsular (c) cataract.
ZcXAqep8' final multivariate models, P < 0.05 was considered statistically
H^n@9U;[K significant. Design effect was assessed through the use
.S54:vs of cluster-specific models and multivariate models. The
2(DhKHrF design effect was assumed to be additive and an adjustment
8C*@d_=q made in the variance by adding the variance associated with
bfz7t!A)A the design effect prior to constructing the 95% confidence
C7{VByxJ limits.
9$HKP9
G RESULTS
4u}Cki,vOK Study population
>b2!&dm A total of 3271 (83%) of the Melbourne residents, 403
]`$yY5 &W0 (90%) Melbourne nursing home residents, and 1473 (92%)
5wV J.B~s rural residents participated. In general, non-participants did
jXA/G%:[ not differ from participants.16 The study population was
*`+zf7-f representative of the Victorian population and Australia as
O +o)z6( a whole.
Y
]()v The Melbourne residents ranged in age from 40 to
9DA|;| 98 years (mean = 59) and 1511 (46%) were male. The
y-+W Melbourne nursing home residents ranged in age from 46 to
myfTztJ 101 years (mean = 82) and 85 (21%) were men. The rural
c0Ih$z residents ranged in age from 40 to 103 years (mean = 60)
bI
;I<Qa and 701 (47.5%) were men.
i24k
]F Prevalence of cataract and prior cataract surgery
`r SOt*< As would be expected, the rate of any cataract increases
VrRF2(Kn? dramatically with age (Table 1). The weighted rate of any
n{TWdC cataract in Victoria was 21.5% (95% CL 18.1, 24.9).
oH=?1~e Although the rates varied somewhat between the three
.*`^dt strata, they were not significantly different as the 95% confidence
"e"#k}z9 limits overlapped. The per cent of cataractous eyes
U2YY with best-corrected visual acuity of less than 6/12 was 12.5%
J*rYw5QB (65/520) for cortical cataract, 18% for nuclear cataract
ljK?2z> (97/534) and 14.4% (27/187) for PSC cataract. Cataract
5?$MZaT surgery also rose dramatically with age. The overall
v)O0i2 weighted rate of prior cataract surgery in Victoria was
E$
\l57 3.79% (95% CL 2.97, 4.60) (Table 2).
#@DJf Risk factors for unoperated cataract
!nl-}P, Cases of cataract that had not been removed were classified
~NIhS! as unoperated cataract. Risk factor analyses for unoperated
+TqrvI. cataract were not performed with the nursing home residents
TXi| as information about risk factor exposure was not
s\mA3t available for this cohort. The following factors were assessed
t4UK~ {gh in relation to unoperated cataract: age, sex, residence
}o:LwxNO (urban/rural), language spoken at home (a measure of ethnic
"T=j\/Q integration), country of birth, parents’ country of birth (a
({rcH.: measure of ethnicity), years since migration, education, use
`l]Lvk8O of ophthalmic services, use of optometric services, private
M#4;y,n<k health insurance status, duration of distance glasses use,
X8m-5(uW glaucoma, age-related maculopathy and employment status.
GkU_01C In this cross sectional study it was not possible to assess the
~v(c9I) level of visual acuity that would predict a patient’s having
05H:ZrUV cataract surgery, as visual acuity data prior to cataract
(!fx5&F surgery were not available.
-}<Ru) The significant risk factors for unoperated cataract in univariate
,Gv}N& analyses were related to: whether a participant had
"=DQ { (L ever seen an optometrist, seen an ophthalmologist or been
1f+A_k/@ diagnosed with glaucoma; and participants’ employment
ng+sK status (currently employed) and age. These significant
.b_ppieNY factors were placed in a backwards stepwise logistic regression
YZfi-35@g model. The factors that remained significantly related
=b*GV6b to unoperated cataract were whether participants had ever
TP#Ncqh seen an ophthalmologist, seen an optometrist and been
=LLpJ+ diagnosed with glaucoma. None of the demographic factors
~.x #ic were associated with unoperated cataract in the multivariate
(pCHj' model.
Sydl[c pH$ The per cent of participants with unoperated cataract
{f/]K GGk who said that they were dissatisfied or very dissatisfied with
axmq/8X Operated and unoperated cataract in Australia 79
`#iL'ND[ Table 1. Prevalence of any cataracta (excluding previous cataract surgery) by age, gender and cohort
Ju#j%
! Age group Sex Urban Rural Nursing home Weighted total
[ p,]/ ^ N (years) (%) (%) (%)
1d+Kn Jy 40–49 Male 2.56 4.04 0.00 3.00 (1.91, 4.08)
>y8>OJ?A7- Female 2.61 1.70 0.00 2.36 (1.61, 3.10)
e=h-}XRC 50–59 Male 7.69 6.94 0.00 7.47 (5.80, 9.15)
-cU bIbW Female 6.67 7.56 0.00 6.92 (5.60, 8.24)
>|Ro
LV 60–69 Male 20.7 25.0 10.0 22.0 (18.1, 26.0)
&V
7J5~_ Female 27.9 35.7 37.5 30.3 (26.0, 34.7)
JcYY*p 70–79 Male 43.1 58.7 39.1 48.1 (41.2, 55.1)
h{"SV*Xpk/ Female 58.6 66.2 55.6 61.0 (56.0, 65.9)
W2-l_{ 80–89 Male 74.0 89.3 92.0 79.3 (72.3, 86.3)
v(Kj6
' Female 91.9 97.0 80.2 92.6 (86.4, 98.8)
Ndl{f=sjX- 90 + Male 100.0 100.0 75.0 98.8 (96.2, 100.0)
vG6*[c8 Female 100.0 100.0 93.8 98.6 (97.0, 100.0)
,#BD/dF Age-standardized
"4xo,JUf (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)
=/j!S|P aCortical > 4/16, nuclear > standard 2, posterior subcapsular > 1 mm2
4E=QO!pVv their current vision was 30% (290/683), compared with 27%
dY.X/f (26/95) of participants with prior cataract surgery (chisquared,
0VQBm^$( 1 d.f. = 0.25, P = 0.62).
Zc38ht\r; Outcomes of cataract surgery
j*gZvbO;'L Two hundred and forty-nine eyes had undergone prior
^& *
;]S` cataract surgery. Of these 249 operated eyes, 49 (20%) were
"D>/#cY1/ left aphakic, 6 (2.4%) had anterior chamber intraocular
QsPg4y3?D lenses and 194 (78%) had posterior chamber intraocular
-4Dz98du lenses. The rate of capsulotomy in the eyes with intact
+68age;dM posterior capsules was 36% (73/202). Fifteen per cent of
^GYVRD eyes (17/114) with a clear posterior capsule had bestcorrected
J"h2"$v, visual acuity of less than 6/12 compared with 43%
1Hhr6T^) of eyes (6/14) with opaque capsules, and 15% of eyes
IC"ktv bHz (11/73) with prior capsulotomies (chi-squared, 2 d.f. = 7.21,
Ui"$A/ P = 0.027).
^^
SMr l The percentage of eyes with best-corrected visual acuity
IDF0nx] of 6/12 or better was 96% (302/314) for eyes without
~mvv
:u cataract, 88% (1417/1609) for eyes with prevalent cataract
'S74Ys=-0 and 85% (211/249) for eyes with operated cataract (chisquared,
K5bR7f: 2 d.f. = 22.3), P < 0.001). Twenty-seven of the
"WmsBdO operated eyes (11%) had visual acuities of less than 6/18
.L^j:2(L (moderate vision impairment) (Fig. 2). A cause of this
xh<{lZ)KJ moderate visual impairment (but not the only cause) in four
n]3'N58 (15%) eyes was secondary to cataract surgery. Three of these
c*axw%Us four eyes had undergone intracapsular cataract extraction
u f<%!=e and the fourth eye had an opaque posterior capsule. No one
3qu?q
D had bilateral vision impairment as a result of their cataract
@@R&OR surgery.
fTX|vy<EMI DISCUSSION
YsiH=x To our knowledge, this is the first paper to systematically
J?t(TW6E
assess the prevalence of current cataract, previous cataract
F 3q<j$y surgery, predictors of unoperated cataract and the outcomes
v^t oe of cataract surgery in a population-based sample. The Visual
)B-[Q#*A- Impairment Project is unique in that the sampling frame and
Z3Ww@&bU