ABSTRACT
$k%
2J9O Purpose: To quantify the prevalence of cataract, the outcomes
*Kgks 4 of cataract surgery and the factors related to
/nNN,hz unoperated cataract in Australia.
HC
s?iJ Methods: Participants were recruited from the Visual
1};Stai'
Impairment Project: a cluster, stratified sample of more than
d.d/< 5000 Victorians aged 40 years and over. At examination
M`!H"R 7 sites interviews, clinical examinations and lens photography
IY\5@PVZ were performed. Cataract was defined in participants who
6j]0R*B7`Q had: had previous cataract surgery, cortical cataract greater
kfY}S than 4/16, nuclear greater than Wilmer standard 2, or
VU]`&`~J posterior subcapsular greater than 1 mm2.
K!Y71_# Results: The participant group comprised 3271 Melbourne
!``,gExH residents, 403 Melbourne nursing home residents and 1473
#gs`#6 ,' rural residents.The weighted rate of any cataract in Victoria
[<yaXQxl was 21.5%. The overall weighted rate of prior cataract
O-
hAFKx surgery was 3.79%. Two hundred and forty-nine eyes had
DA,?} had prior cataract surgery. Of these 249 procedures, 49
_8UU'1d
(20%) were aphakic, 6 (2.4%) had anterior chamber
A]oV"`f intraocular lenses and 194 (78%) had posterior chamber
>@_^fw) intraocular lenses.Two hundred and eleven of these operated
`l[c_%Bm eyes (85%) had best-corrected visual acuity of 6/12 or
v^*K:#<Q! better, the legal requirement for a driver’s license.Twentyseven
<<5(0#y# (11%) had visual acuity of less than 6/18 (moderate
} (73Syl# vision impairment). Complications of cataract surgery
SO'vpz{ caused reduced vision in four of the 27 eyes (15%), or 1.9%
&@OT*pNna of operated eyes. Three of these four eyes had undergone
;h intracapsular cataract extraction and the fourth eye had an
7[XRd9a5( opaque posterior capsule. No one had bilateral vision
jm/`iXnMf impairment as a result of cataract surgery. Surprisingly, no
e6$W Qd`O particular demographic factors (such as age, gender, rural
\Uq(Zga4) residence, occupation, employment status, health insurance
I,vJbvvl! status, ethnicity) were related to the presence of unoperated
~=l;=7 T cataract.
`|&O*` Conclusions: Although the overall prevalence of cataract is
R-d:j^:f quite high, no particular subgroup is systematically underserviced
3;]H1
1 in terms of cataract surgery. Overall, the results of
c,+:i1IAy cataract surgery are very good, with the majority of eyes
,w4V?>l achieving driving vision following cataract extraction.
>!1-lfa8 Key words: cataract extraction, health planning, health
n9ej7oj services accessibility, prevalence
sS'm
!7*(3 INTRODUCTION
.Vvx,>>D Cataract is the leading cause of blindness worldwide and, in
'e'cb>GnA Australia, cataract extractions account for the majority of all
$5%SNzzl ophthalmic procedures.1 Over the period 1985–94, the rate
jasy<IqT!{ of cataract surgery in Australia was twice as high as would be
/!XVHkX[ expected from the growth in the elderly population.1
tW}'g:s Although there have been a number of studies reporting
-k
"/X8 the prevalence of cataract in various populations,2–6 there is
O5T{eBo\ little information about determinants of cataract surgery in
Yufc{M00 the population. A previous survey of Australian ophthalmologists
"b3"TPfK showed that patient concern and lifestyle, rather
aHK}sr,U than visual acuity itself, are the primary factors for referral
8P&:_T! for cataract surgery.7 This supports prior research which has
0*{%=M shown that visual acuity is not a strong predictor of need for
Ok=hT|}Y cataract surgery.8,9 Elsewhere, socioeconomic status has
Vp@?^
imL been shown to be related to cataract surgery rates.10
_L=h0H l To appropriately plan health care services, information is
AFE~
v\Gz needed about the prevalence of age-related cataract in the
NyNXP_8 community as well as the factors associated with cataract
:&."ttf= surgery. The purpose of this study is to quantify the prevalence
ds[| of any cataract in Australia, to describe the factors
j*r{2f4Rt related to unoperated cataract in the community and to
c(s.5p ^ describe the visual outcomes of cataract surgery.
J<jy2@"tXo METHODS
s|r3Gv|G Study population
4~Q/"hMSkO Details about the study methodology for the Visual
{;6`_-As% Impairment Project have been published previously.11
~oY^;/ j Briefly, cluster sampling within three strata was employed to
&&>ekG9@ recruit subjects aged 40 years and over to participate.
v):Or'$~M Within the Melbourne Statistical Division, nine pairs of
WNrk}LFof census collector districts were randomly selected. Fourteen
w ;^ra<*<+ nursing homes within a 5 km radius of these nine test sites
I9ep`X6Y were randomly chosen to recruit nursing home residents.
k@W1-D? Clinical and Experimental Ophthalmology (2000) 28, 77–82
[MY|T<q Original Article
%n9aaoD Operated and unoperated cataract in Australia
6(ol1
(U Catherine A McCarty PhD, MPH, Mukesh B Nanjan PhD, Hugh R Taylor MD
$*fMR,~t& Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
mc\"yC^s n Correspondence: Dr Cathy McCarty MPH, Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, 32 Gisborne Street, East Melbourne,
r*Ca}Z Victoria 3002, Australia. Email:
cathy@cera.unimelb.edu.au HN|%9{VeB 78 McCarty et al.
\bw2u! Finally, four pairs of census collector districts in four rural
v`
1lxX'* Victorian communities were randomly selected to recruit rural
P/_['7 residents. A household census was conducted to identify
brUF6rQ eligible residents aged 40 years and over who had been a
pYf-S?Y/V resident at that address for at least 6 months. At the time of
/mzlH the household census, basic information about age, sex,
P5ywhw- country of birth, language spoken at home, education, use of
>~0Z& d corrective spectacles and use of eye care services was collected.
Pe3o;mx Eligible residents were then invited to attend a local
M9%$lCl
examination site for a more detailed interview and examination.
h<<v^+m The study protocol was approved by the Royal Victorian
T]~xj4 Eye and Ear Hospital Human Research Ethics Committee.
x7 ,5 Assessment of cataract
AFwdJte9e A standardized ophthalmic examination was performed after
63IM]J pupil dilatation with one drop of 10% phenylephrine
FfT`;j hydrochloride. Lens opacities were graded clinically at the
SXP]%{@R/ time of the examination and subsequently from photos using
DZ
tsy!xA the Wilmer cataract photo-grading system.12 Cortical and
KF:78C posterior subcapsular (PSC) opacities were assessed on
inp7K41 retroillumination and measured as the proportion (in 1/16)
/od@!/ of pupil circumference occupied by opacity. For this analysis,
&mS^ZyG cortical cataract was defined as 4/16 or greater opacity,
;#< 0< PSC cataract was defined as opacity equal to or greater than
8'y$M] e9n 1 mm2 and nuclear cataract was defined as opacity equal to
")p\q:z6 or greater than Wilmer standard 2,12 independent of visual
*MW\^PR? acuity. Examples of the minimum opacities defined as cortical,
&s>Jb?_5Mx nuclear and PSC cataract are presented in Figure 1.
)MT}+ai Bilateral congenital cataracts or cataracts secondary to
^E>3|du]O intraocular inflammation or trauma were excluded from the
]JQ
ULE) analysis. Two cases of bilateral secondary cataract and eight
s_p!43\J cases of bilateral congenital cataract were excluded from the
nQ3A~ () analyses.
V0 a3<6@4 A Topcon® SL5 photo slit-lamp (Topcon America Corp.,
~6md !o%i Paramus, NJ, USA) with a 0.1 mm slit beam of 9.0 mm in
{R{=+2K!|k height set to an incident angle of 30° was used for examinations.
P@~yx#G Ektachrome® 200 ASA colour slide film (Eastman
gbD KE{ Kodak Company, Rochester, NY, USA) was used to photograph
SUK?z!f<i the nuclear opacities. The cortical opacities were
=($xG#g` photographed with an Oxford® retroillumination camera
9%obq/Lb (Marcher Enterprises Ltd, Hereford, UK) and T-MAX® 400
vW@=<aS Z film (Eastman Kodak). Photographs were graded separately
?:9"X$XR by two research assistants and discrepancies were adjudicated
*|HY>U. by an independent reviewer. Any discrepancies
}c:M^Ff between the clinical grades and the photograph grades were
[()koU#w. resolved. Except in cases where photographs were missing,
.*Qx\, the photograph grades were used in the analyses. Photograph
u_Z+;{]Pj grades were available for 4301 (84%) for cortical
`\ol,B_l cataract, 4147 (81%) for nuclear cataract and 4303 (84%)
O^rD HFj, for PSC cataract. Cataract status was classified according to
_,*r_D61S the severity of the opacity in the worse eye.
RT8 ?7xFc Assessment of risk factors
7
a}k A standardized questionnaire was used to obtain information
;5Ac
FB about education, employment and ethnic background.11
3PF_H$`oJ Specific information was elicited on the occurrence, duration
|k9
C/ and treatment of a number of medical conditions,
-D:b*D including ocular trauma, arthritis, diabetes, gout, hypertension
I]_5}[I and mental illness. Information about the use, dose and
PZzMHK?hP duration of tobacco, alcohol, analgesics and steriods were
!bP@n collected, and a food frequency questionnaire was used to
TkF[x%o determine current consumption of dietary sources of antioxidants
IAyp 2
and use of vitamin supplements.
l}P=/#</T Data management and statistical analysis
lk =<A"^S Data were collected either by direct computer entry with a
vw@S>GlGg questionnaire programmed in Paradox© (Carel Corporation,
EhBKj |y Ottawa, Canada) with internal consistency checks, or
HE\K@3- on self-coding forms. Open-ended responses were coded at
H%{+QwzZ[j a later time. Data that were entered on the self-coded forms
#s9aI_ were entered into a computer with double data entry and
CNx8]
_2 reconciliation of any inconsistencies. Data range and consistency
[PbOfxxgA checks were performed on the entire data set.
51.%;aY~z SAS© version 6.1 (SAS Institute, Cary, North Carolina) was
;O#>Y employed for statistical analyses.
]JR +ayk7 Ninety-five per cent confidence limits around the agespecific
yF/j Fn rates were calculated according to Cochran13 to
N
Zz 8j^ account for the effect of the cluster sampling. Ninety-five
V^~:F per cent confidence limits around age-standardized rates
7o}J%z were calculated according to Breslow and Day.14 The strataspecific
cl/_JQ& data were weighted according to the 1996
7>*vI7O0l Australian Bureau of Statistics census data15 to reflect the
Dum9lj cataract prevalence in the entire Victorian population.
?Ss!
e$jf Univariate analyses with Student’s t-tests and chi-squared
{(?4!rh tests were first employed to evaluate risk factors for unoperated
SZCze"`[ cataract. Any factors with P < 0.10 were then fitted
PTV:IzoW into a backwards stepwise logistic regression model. For the
h
zn6kbv Figure 1. Minimum levels of cortical (a), nuclear (b), and posterior subcapsular (c) cataract.
/2VJX@h final multivariate models, P < 0.05 was considered statistically
;]:@n;c\ significant. Design effect was assessed through the use
1m0c|ckb of cluster-specific models and multivariate models. The
[=`q>|;pOv design effect was assumed to be additive and an adjustment
ZSm3 XXk made in the variance by adding the variance associated with
+x}<IS8 the design effect prior to constructing the 95% confidence
g<
.qUBPKX limits.
[)X\|pO& RESULTS
B4 }bVjs Study population
[z9Z5sLO A total of 3271 (83%) of the Melbourne residents, 403
y1L,0 ] (90%) Melbourne nursing home residents, and 1473 (92%)
)@bQu~Y rural residents participated. In general, non-participants did
Pj%|\kbNs not differ from participants.16 The study population was
koi^l`B$ representative of the Victorian population and Australia as
)whA<lC a whole.
QkC
(uS The Melbourne residents ranged in age from 40 to
;gr9/Vl 98 years (mean = 59) and 1511 (46%) were male. The
L_iFt! Melbourne nursing home residents ranged in age from 46 to
]e@Oiq 101 years (mean = 82) and 85 (21%) were men. The rural
-A!%*9Z residents ranged in age from 40 to 103 years (mean = 60)
P7/X|M z and 701 (47.5%) were men.
M\Kx'N Prevalence of cataract and prior cataract surgery
3=ymm^ As would be expected, the rate of any cataract increases
SasJic2M dramatically with age (Table 1). The weighted rate of any
65^9 cataract in Victoria was 21.5% (95% CL 18.1, 24.9).
<2qr}K{'A Although the rates varied somewhat between the three
lHX72s|V strata, they were not significantly different as the 95% confidence
cYt!n5w~W limits overlapped. The per cent of cataractous eyes
A3@6N( with best-corrected visual acuity of less than 6/12 was 12.5%
3m)y|$R (65/520) for cortical cataract, 18% for nuclear cataract
0lR5<^B (97/534) and 14.4% (27/187) for PSC cataract. Cataract
'`KY!]L surgery also rose dramatically with age. The overall
M/K5#8Arj weighted rate of prior cataract surgery in Victoria was
6NHX2Ja 3.79% (95% CL 2.97, 4.60) (Table 2).
b SU~XGPB Risk factors for unoperated cataract
7Jho}5J Cases of cataract that had not been removed were classified
ixD)VcD-f as unoperated cataract. Risk factor analyses for unoperated
kPLxEwl cataract were not performed with the nursing home residents
:6\qpex as information about risk factor exposure was not
CizX<Cr} available for this cohort. The following factors were assessed
Jz e:[MYS in relation to unoperated cataract: age, sex, residence
) hfpwdQ (urban/rural), language spoken at home (a measure of ethnic
0KOgw*>_ integration), country of birth, parents’ country of birth (a
Q$@I"V&G. measure of ethnicity), years since migration, education, use
TbW38\>.R of ophthalmic services, use of optometric services, private
@6
T/Tdz health insurance status, duration of distance glasses use,
|8tilOqI glaucoma, age-related maculopathy and employment status.
j#q-^h3H In this cross sectional study it was not possible to assess the
pg)WKbV level of visual acuity that would predict a patient’s having
G*P#]eO cataract surgery, as visual acuity data prior to cataract
cHt#us surgery were not available.
wi6
~}~% The significant risk factors for unoperated cataract in univariate
)|=j`jCC analyses were related to: whether a participant had
HRf
Yl,S, ever seen an optometrist, seen an ophthalmologist or been
?+}_1x` diagnosed with glaucoma; and participants’ employment
b2&0Hx status (currently employed) and age. These significant
RdRp.pb8 factors were placed in a backwards stepwise logistic regression
338k?nHxv model. The factors that remained significantly related
l)l^[2 to unoperated cataract were whether participants had ever
X?qK0fS seen an ophthalmologist, seen an optometrist and been
LuvY<~u diagnosed with glaucoma. None of the demographic factors
.jjG(
L were associated with unoperated cataract in the multivariate
fHd#u%63K model.
[j/9neaye The per cent of participants with unoperated cataract
aE$[52 who said that they were dissatisfied or very dissatisfied with
R|87%&6'] Operated and unoperated cataract in Australia 79
S k\K4 Table 1. Prevalence of any cataracta (excluding previous cataract surgery) by age, gender and cohort
|"CZ T# Age group Sex Urban Rural Nursing home Weighted total
DAr1
C+Dy
(years) (%) (%) (%)
}Sh?S]]` 40–49 Male 2.56 4.04 0.00 3.00 (1.91, 4.08)
V#gK$uv Female 2.61 1.70 0.00 2.36 (1.61, 3.10)
eiaFaYe\ 50–59 Male 7.69 6.94 0.00 7.47 (5.80, 9.15)
!Pfr,a Female 6.67 7.56 0.00 6.92 (5.60, 8.24)
m'=Crei 60–69 Male 20.7 25.0 10.0 22.0 (18.1, 26.0)
=|y9UlsD Female 27.9 35.7 37.5 30.3 (26.0, 34.7)
E,x+JeKV 70–79 Male 43.1 58.7 39.1 48.1 (41.2, 55.1)
h( u8&MHx Female 58.6 66.2 55.6 61.0 (56.0, 65.9)
A&Usddcp 80–89 Male 74.0 89.3 92.0 79.3 (72.3, 86.3)
6wjw ^m0 Female 91.9 97.0 80.2 92.6 (86.4, 98.8)
LxSpctiNx 90 + Male 100.0 100.0 75.0 98.8 (96.2, 100.0)
h_3E)jc Female 100.0 100.0 93.8 98.6 (97.0, 100.0)
%axh`xK# Age-standardized
V1`o%;j (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)
?(F6#"/E aCortical > 4/16, nuclear > standard 2, posterior subcapsular > 1 mm2
)e=D(qd their current vision was 30% (290/683), compared with 27%
' ;FnIZ (26/95) of participants with prior cataract surgery (chisquared,
S3*`jF>q 1 d.f. = 0.25, P = 0.62).
m6\E$;` Outcomes of cataract surgery
+YKi, Two hundred and forty-nine eyes had undergone prior
}9# r0Vja cataract surgery. Of these 249 operated eyes, 49 (20%) were
P90yI left aphakic, 6 (2.4%) had anterior chamber intraocular
eFTpnG lenses and 194 (78%) had posterior chamber intraocular
?*1uN=oI{* lenses. The rate of capsulotomy in the eyes with intact
;yLu
R posterior capsules was 36% (73/202). Fifteen per cent of
{
Vf XsI eyes (17/114) with a clear posterior capsule had bestcorrected
Ls$D$/:q? visual acuity of less than 6/12 compared with 43%
%G/hD of eyes (6/14) with opaque capsules, and 15% of eyes
lH x^D;m6 (11/73) with prior capsulotomies (chi-squared, 2 d.f. = 7.21,
t?-n*9,#S P = 0.027).
j<99FW"@e The percentage of eyes with best-corrected visual acuity
*ebSq) of 6/12 or better was 96% (302/314) for eyes without
#@9/
g cataract, 88% (1417/1609) for eyes with prevalent cataract
b_#m}yZ6 and 85% (211/249) for eyes with operated cataract (chisquared,
oim9<_ 2 d.f. = 22.3), P < 0.001). Twenty-seven of the
,c$_t+ operated eyes (11%) had visual acuities of less than 6/18
9~5uaP$S (moderate vision impairment) (Fig. 2). A cause of this
RK'\C\gMDu moderate visual impairment (but not the only cause) in four
"$Z= %.3Q (15%) eyes was secondary to cataract surgery. Three of these
a LroD$# four eyes had undergone intracapsular cataract extraction
EyD=q! ZVZ and the fourth eye had an opaque posterior capsule. No one
jk; clwyz/ had bilateral vision impairment as a result of their cataract
@uqd.Q surgery.
b8`)y<