ABSTRACT
cD%_+@GaU Purpose: To quantify the prevalence of cataract, the outcomes
.S_7R/2(? of cataract surgery and the factors related to
K]{x0A unoperated cataract in Australia.
cj64.C Methods: Participants were recruited from the Visual
{py"Ob_ Impairment Project: a cluster, stratified sample of more than
4\_~B{kzZ 5000 Victorians aged 40 years and over. At examination
X7~^D[X sites interviews, clinical examinations and lens photography
ZLGglT'EW> were performed. Cataract was defined in participants who
o*t4zF&n had: had previous cataract surgery, cortical cataract greater
d :vuRK4+ than 4/16, nuclear greater than Wilmer standard 2, or
mXPA1#qo posterior subcapsular greater than 1 mm2.
5r` x\ Results: The participant group comprised 3271 Melbourne
#iiXJnG residents, 403 Melbourne nursing home residents and 1473
<-h[I&." rural residents.The weighted rate of any cataract in Victoria
KY'x;\0
g was 21.5%. The overall weighted rate of prior cataract
`9Rj;^NJ surgery was 3.79%. Two hundred and forty-nine eyes had
"?M)2,:A had prior cataract surgery. Of these 249 procedures, 49
'lMDlTU O (20%) were aphakic, 6 (2.4%) had anterior chamber
3Fg{?C_l intraocular lenses and 194 (78%) had posterior chamber
lD#S:HX intraocular lenses.Two hundred and eleven of these operated
iBt<EM]U/ eyes (85%) had best-corrected visual acuity of 6/12 or
$vLGX>H better, the legal requirement for a driver’s license.Twentyseven
rU
|% (11%) had visual acuity of less than 6/18 (moderate
0aqq*e'c vision impairment). Complications of cataract surgery
+Ym#!" caused reduced vision in four of the 27 eyes (15%), or 1.9%
rNoCmNm of operated eyes. Three of these four eyes had undergone
LL_@nvu}M intracapsular cataract extraction and the fourth eye had an
ELZ@0, opaque posterior capsule. No one had bilateral vision
$YiG0GK<" impairment as a result of cataract surgery. Surprisingly, no
Vz]yJ: particular demographic factors (such as age, gender, rural
<64#J9T^ residence, occupation, employment status, health insurance
RDOV+2K status, ethnicity) were related to the presence of unoperated
8
+mW cataract.
=bOMtQ] Conclusions: Although the overall prevalence of cataract is
2t;3_C quite high, no particular subgroup is systematically underserviced
C'6c, in terms of cataract surgery. Overall, the results of
m>^vr7 cataract surgery are very good, with the majority of eyes
;qs^+ achieving driving vision following cataract extraction.
ujLje:Yc Key words: cataract extraction, health planning, health
5^Ny6t services accessibility, prevalence
.\+c{ INTRODUCTION
wAo6:) Cataract is the leading cause of blindness worldwide and, in
v)
aV(Oa Australia, cataract extractions account for the majority of all
E
<N% ophthalmic procedures.1 Over the period 1985–94, the rate
Ch)E:Dvq
6 of cataract surgery in Australia was twice as high as would be
{8556> \~ expected from the growth in the elderly population.1
r_MP[]f|0 Although there have been a number of studies reporting
5`QfysR5 the prevalence of cataract in various populations,2–6 there is
nK`H;k little information about determinants of cataract surgery in
L>pSE'} the population. A previous survey of Australian ophthalmologists
xLP8*lvy showed that patient concern and lifestyle, rather
c_ u7O
\ than visual acuity itself, are the primary factors for referral
v8TNBsEL for cataract surgery.7 This supports prior research which has
65GC7 >[ shown that visual acuity is not a strong predictor of need for
"?6R"Vk?: cataract surgery.8,9 Elsewhere, socioeconomic status has
Li+|%a been shown to be related to cataract surgery rates.10
cqp^**s To appropriately plan health care services, information is
}tJMnq/m($ needed about the prevalence of age-related cataract in the
?4t~z 1.f community as well as the factors associated with cataract
Pr,C
)uch surgery. The purpose of this study is to quantify the prevalence
knzQ)iv&& of any cataract in Australia, to describe the factors
KP!7hJhw related to unoperated cataract in the community and to
eGUe#(I / describe the visual outcomes of cataract surgery.
'.e5Ku METHODS
F#
o{/u?T Study population
iig&O(, Details about the study methodology for the Visual
[-\DC*6 Impairment Project have been published previously.11
v%QCp Briefly, cluster sampling within three strata was employed to
xzRC % recruit subjects aged 40 years and over to participate.
[n +( Within the Melbourne Statistical Division, nine pairs of
ZRUA w,T * census collector districts were randomly selected. Fourteen
s%?<:9 nursing homes within a 5 km radius of these nine test sites
Si|8xq$E; were randomly chosen to recruit nursing home residents.
fVZ_*'v Clinical and Experimental Ophthalmology (2000) 28, 77–82
!)c0 Original Article
tOPkx( Operated and unoperated cataract in Australia
5d|+ c< Catherine A McCarty PhD, MPH, Mukesh B Nanjan PhD, Hugh R Taylor MD
|h:3BV_ Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
+@PZ3
[s n Correspondence: Dr Cathy McCarty MPH, Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, 32 Gisborne Street, East Melbourne,
NmN:x&/ Victoria 3002, Australia. Email:
cathy@cera.unimelb.edu.au Fh)YNW@ 78 McCarty et al.
i{PX= Finally, four pairs of census collector districts in four rural
hy:K) _
Victorian communities were randomly selected to recruit rural
dRTpGz residents. A household census was conducted to identify
6:\z8fYD eligible residents aged 40 years and over who had been a
'`p0T%w resident at that address for at least 6 months. At the time of
H{;8i7% the household census, basic information about age, sex,
,qlFk|A| country of birth, language spoken at home, education, use of
%;G!gJeE
corrective spectacles and use of eye care services was collected.
P
+3)Y
O1C Eligible residents were then invited to attend a local
!i6 aA1' examination site for a more detailed interview and examination.
~K|o@LK The study protocol was approved by the Royal Victorian
+z\
O"zlj Eye and Ear Hospital Human Research Ethics Committee.
F^');8~L Assessment of cataract
m<22E0=g A standardized ophthalmic examination was performed after
Xgm9>/y pupil dilatation with one drop of 10% phenylephrine
Y'%_-- hydrochloride. Lens opacities were graded clinically at the
U0S}O(Ptr time of the examination and subsequently from photos using
fI0L\^b% the Wilmer cataract photo-grading system.12 Cortical and
3!B3C(g posterior subcapsular (PSC) opacities were assessed on
Xq%!(YD| retroillumination and measured as the proportion (in 1/16)
O~&l.>?? of pupil circumference occupied by opacity. For this analysis,
RwwX;I"o% cortical cataract was defined as 4/16 or greater opacity,
UJF
}Ye PSC cataract was defined as opacity equal to or greater than
:ui1]its4 1 mm2 and nuclear cataract was defined as opacity equal to
kLqFh< or greater than Wilmer standard 2,12 independent of visual
-.WVuc` acuity. Examples of the minimum opacities defined as cortical,
h Tn^:%( nuclear and PSC cataract are presented in Figure 1.
mwTn}h3N Bilateral congenital cataracts or cataracts secondary to
G8?<(.pi@ intraocular inflammation or trauma were excluded from the
ss3fq} analysis. Two cases of bilateral secondary cataract and eight
(jY
s_8; cases of bilateral congenital cataract were excluded from the
c#;LH5KI analyses.
M !OI :v A Topcon® SL5 photo slit-lamp (Topcon America Corp.,
F]?$Q'U Paramus, NJ, USA) with a 0.1 mm slit beam of 9.0 mm in
+CNRSq" height set to an incident angle of 30° was used for examinations.
z_l3=7R Ektachrome® 200 ASA colour slide film (Eastman
(*fsv
g~ Kodak Company, Rochester, NY, USA) was used to photograph
NI s
4v(! the nuclear opacities. The cortical opacities were
7<^D7 photographed with an Oxford® retroillumination camera
.Na>BR\F
(Marcher Enterprises Ltd, Hereford, UK) and T-MAX® 400
,em6wIq, film (Eastman Kodak). Photographs were graded separately
D+o.9I/{ by two research assistants and discrepancies were adjudicated
v
V^ GIWK by an independent reviewer. Any discrepancies
TcfBfscU between the clinical grades and the photograph grades were
Dfhs@ z resolved. Except in cases where photographs were missing,
UXk8nH the photograph grades were used in the analyses. Photograph
.DvAX(2v grades were available for 4301 (84%) for cortical
f|^f^Hu:{ cataract, 4147 (81%) for nuclear cataract and 4303 (84%)
2aje
$w- for PSC cataract. Cataract status was classified according to
V_W=MWs&+ the severity of the opacity in the worse eye.
l*m|b""].u Assessment of risk factors
49zp@a A standardized questionnaire was used to obtain information
"\=_- ` about education, employment and ethnic background.11
`A^} X Specific information was elicited on the occurrence, duration
\%Smp2K and treatment of a number of medical conditions,
]Ojt3)fB including ocular trauma, arthritis, diabetes, gout, hypertension
Hf-F-~E and mental illness. Information about the use, dose and
zn~m;0Xi duration of tobacco, alcohol, analgesics and steriods were
kv4J@ collected, and a food frequency questionnaire was used to
4#YklVm determine current consumption of dietary sources of antioxidants
y d$37G|n and use of vitamin supplements.
5y'Yosy: Data management and statistical analysis
v:0i5h&M Data were collected either by direct computer entry with a
KE3v3g< questionnaire programmed in Paradox© (Carel Corporation,
HY:@=%R Ottawa, Canada) with internal consistency checks, or
F3'X on self-coding forms. Open-ended responses were coded at
W%W.
+f a later time. Data that were entered on the self-coded forms
D{l((t3=T were entered into a computer with double data entry and
T7Ac4LA reconciliation of any inconsistencies. Data range and consistency
mN*P2* checks were performed on the entire data set.
mC7Y * SAS© version 6.1 (SAS Institute, Cary, North Carolina) was
<<1oc{i employed for statistical analyses.
FTfA\/tl(; Ninety-five per cent confidence limits around the agespecific
VfwD{+5 rates were calculated according to Cochran13 to
Nw2 bn account for the effect of the cluster sampling. Ninety-five
.'1j5Y-l`N per cent confidence limits around age-standardized rates
,H?p9L; qp were calculated according to Breslow and Day.14 The strataspecific
]`XuE-Uh data were weighted according to the 1996
9-^p23.@[j Australian Bureau of Statistics census data15 to reflect the
dL`
+^E> cataract prevalence in the entire Victorian population.
]EnaZWyO] Univariate analyses with Student’s t-tests and chi-squared
o4;Nb|kk9+ tests were first employed to evaluate risk factors for unoperated
wVOL7vh cataract. Any factors with P < 0.10 were then fitted
+CT$/k into a backwards stepwise logistic regression model. For the
? ^CGJ1 Figure 1. Minimum levels of cortical (a), nuclear (b), and posterior subcapsular (c) cataract.
(O2HB-<rY final multivariate models, P < 0.05 was considered statistically
tl5IwrF6; significant. Design effect was assessed through the use
RKkI/ Z0 of cluster-specific models and multivariate models. The
!f-o,RJ design effect was assumed to be additive and an adjustment
|q2lTbJ made in the variance by adding the variance associated with
%}
,G(> the design effect prior to constructing the 95% confidence
I uj=d~|> limits.
B7MW"
y RESULTS
1qe^rz| Study population
znO00qX A total of 3271 (83%) of the Melbourne residents, 403
IJY5wP1" (90%) Melbourne nursing home residents, and 1473 (92%)
{7>CA'> rural residents participated. In general, non-participants did
!(K{*7|h not differ from participants.16 The study population was
!<zzP LC representative of the Victorian population and Australia as
d$rUxqB. a whole.
D(6x'</>? The Melbourne residents ranged in age from 40 to
<]^;/2.B 98 years (mean = 59) and 1511 (46%) were male. The
(iOCzZ6S Melbourne nursing home residents ranged in age from 46 to
IW
o~s 101 years (mean = 82) and 85 (21%) were men. The rural
lp-Zx[#`}C residents ranged in age from 40 to 103 years (mean = 60)
Jx$#GUl#j and 701 (47.5%) were men.
NJf(,Mr*| Prevalence of cataract and prior cataract surgery
1bZiPG{ As would be expected, the rate of any cataract increases
Au} ;z6k dramatically with age (Table 1). The weighted rate of any
Rgfhs[Z cataract in Victoria was 21.5% (95% CL 18.1, 24.9).
:n9xH Although the rates varied somewhat between the three
1DLG]-j} strata, they were not significantly different as the 95% confidence
| 58!A] limits overlapped. The per cent of cataractous eyes
p;=kH{uu with best-corrected visual acuity of less than 6/12 was 12.5%
b]<HhU (65/520) for cortical cataract, 18% for nuclear cataract
Ogke*qM (97/534) and 14.4% (27/187) for PSC cataract. Cataract
9jR[:[
surgery also rose dramatically with age. The overall
pl x/}ah8 weighted rate of prior cataract surgery in Victoria was
$7n#\h 3.79% (95% CL 2.97, 4.60) (Table 2).
[s{r$!Gl Risk factors for unoperated cataract
"Z 2Tc) Cases of cataract that had not been removed were classified
{jM<
t as unoperated cataract. Risk factor analyses for unoperated
P%+or * cataract were not performed with the nursing home residents
w"a 9'r as information about risk factor exposure was not
dxn0HXU available for this cohort. The following factors were assessed
_TOi
[GT in relation to unoperated cataract: age, sex, residence
ri<'-w i (urban/rural), language spoken at home (a measure of ethnic
|Sr\jUIWn integration), country of birth, parents’ country of birth (a
i6F:C
&. measure of ethnicity), years since migration, education, use
] `B,L*m6 of ophthalmic services, use of optometric services, private
GL5^_`n health insurance status, duration of distance glasses use,
D#d8 ^U glaucoma, age-related maculopathy and employment status.
VPM|Rj:d In this cross sectional study it was not possible to assess the
L8:]`MQ0 level of visual acuity that would predict a patient’s having
s`#ntset0 cataract surgery, as visual acuity data prior to cataract
wrQydI surgery were not available.
13.{Y) The significant risk factors for unoperated cataract in univariate
Eg`R|CF analyses were related to: whether a participant had
2{mY:\ ever seen an optometrist, seen an ophthalmologist or been
@1<omsl diagnosed with glaucoma; and participants’ employment
9V=<| 2 status (currently employed) and age. These significant
X:G&5 factors were placed in a backwards stepwise logistic regression
B:O+*3j model. The factors that remained significantly related
%Lp2jyv. to unoperated cataract were whether participants had ever
1 [fo'M seen an ophthalmologist, seen an optometrist and been
5ys#L&q'Z diagnosed with glaucoma. None of the demographic factors
C~ZE95g were associated with unoperated cataract in the multivariate
'bB>$E model.
&<gUFcw7Ui The per cent of participants with unoperated cataract
0 NQ7#A who said that they were dissatisfied or very dissatisfied with
W
il{FcHY Operated and unoperated cataract in Australia 79
-l-AToO4 Table 1. Prevalence of any cataracta (excluding previous cataract surgery) by age, gender and cohort
6sYV7w,'@ Age group Sex Urban Rural Nursing home Weighted total
>"cr-LB (years) (%) (%) (%)
UvPp~N7, 40–49 Male 2.56 4.04 0.00 3.00 (1.91, 4.08)
x1Nme%%& Female 2.61 1.70 0.00 2.36 (1.61, 3.10)
s8t f@H4r 50–59 Male 7.69 6.94 0.00 7.47 (5.80, 9.15)
$Q8P@L)[ Female 6.67 7.56 0.00 6.92 (5.60, 8.24)
z@!^ow)`J 60–69 Male 20.7 25.0 10.0 22.0 (18.1, 26.0)
D3%l4.h Female 27.9 35.7 37.5 30.3 (26.0, 34.7)
,3:QB_ 70–79 Male 43.1 58.7 39.1 48.1 (41.2, 55.1)
y
Dd=&
T
Female 58.6 66.2 55.6 61.0 (56.0, 65.9)
gWFL 80–89 Male 74.0 89.3 92.0 79.3 (72.3, 86.3)
U:qF/%w Female 91.9 97.0 80.2 92.6 (86.4, 98.8)
GS}0;x 90 + Male 100.0 100.0 75.0 98.8 (96.2, 100.0)
/"(b.& Female 100.0 100.0 93.8 98.6 (97.0, 100.0)
)*!1bgXQ Age-standardized
,q8(]n4 (95% CL) Combined 19.7 (16.3, 23.1) 23.2 (16.1, 30.2) 16.5 (2.06, 30.9) 21.5 (18.1, 25.0)
M|U';2hZN: aCortical > 4/16, nuclear > standard 2, posterior subcapsular > 1 mm2
Ru)(dvk}S their current vision was 30% (290/683), compared with 27%
Qn*
6D (26/95) of participants with prior cataract surgery (chisquared,
DZJeup?Z 1 d.f. = 0.25, P = 0.62).
DeA @0HOxh Outcomes of cataract surgery
5+`=t07^et Two hundred and forty-nine eyes had undergone prior
LlU'_}> cataract surgery. Of these 249 operated eyes, 49 (20%) were
`Gf{z%/ left aphakic, 6 (2.4%) had anterior chamber intraocular
y0;,dv] lenses and 194 (78%) had posterior chamber intraocular
=Wj{]&` lenses. The rate of capsulotomy in the eyes with intact
#De(*&y2 posterior capsules was 36% (73/202). Fifteen per cent of
m6-76ma,hi eyes (17/114) with a clear posterior capsule had bestcorrected
P!5Z]+B# visual acuity of less than 6/12 compared with 43%
o1U}/y+R\ of eyes (6/14) with opaque capsules, and 15% of eyes
U%L
-NMe (11/73) with prior capsulotomies (chi-squared, 2 d.f. = 7.21,
\kxh#{$z? P = 0.027).
T4e
WbNSs The percentage of eyes with best-corrected visual acuity
9-b 8`|s of 6/12 or better was 96% (302/314) for eyes without
N9pwWg&<+ cataract, 88% (1417/1609) for eyes with prevalent cataract
FK6K6wU52m and 85% (211/249) for eyes with operated cataract (chisquared,
rmoJ
=.' 2 d.f. = 22.3), P < 0.001). Twenty-seven of the
rxs8De operated eyes (11%) had visual acuities of less than 6/18
'v\j.j/i (moderate vision impairment) (Fig. 2). A cause of this
\Y9I~8\gB moderate visual impairment (but not the only cause) in four
gd
K*"U (15%) eyes was secondary to cataract surgery. Three of these
w3d34*0$ four eyes had undergone intracapsular cataract extraction
oQ{cSThj and the fourth eye had an opaque posterior capsule. No one
/V#7=,, had bilateral vision impairment as a result of their cataract
V(r`.
75 surgery.
f -7S:, DISCUSSION
5:$Xtq To our knowledge, this is the first paper to systematically
Mo_$b8i assess the prevalence of current cataract, previous cataract
w?_`/oqd| surgery, predictors of unoperated cataract and the outcomes
IYLZ
+> of cataract surgery in a population-based sample. The Visual
^Wm*-4 Impairment Project is unique in that the sampling frame and
zXjwnep high response rate have ensured that the study population is
"ct58Y@ representative of Australians aged 40 years and over. Therefore,
^(DL+r, these data can be used to plan age-related cataract
C;ptir1G; services throughout Australia.
2
^oGwx @ We found the rate of any cataract in those over the age
8A!'I<S1 of 40 years to be 22%. Although relatively high, this rate is
~{$L9;x significantly less than was reported in a number of previous
R1Yqz $# studies,2,4,6 with the exception of the Casteldaccia Eye
6P^hN%0 Study.5 However, it is difficult to compare rates of cataract
<