Diabetic retinopathy and the major causes of vision loss in Aboriginals from remote Western...

Original Article

Diabetic retinopathy and the major causes ofvision loss in Aboriginals from remoteWestern Australia_ 475..482

Antony Clark MBBS(Hons),1,2,3 William H Morgan FRANZCO PhD,1,3,4,5 Sam Kain FRANZCO,5

Hussein Farah MBBS,6 Kiele Armstrong MIH GradDipPH,6 David Preen BSc(Hons) PhD,2,3

James B Semmens MSc PhD1,3 and Dao-Yi Yu MD PhD4

1Centre for Population Health Research, Curtin Health Innovation Research Institute, Curtin University of Technology, 2Centre forHealth Services Research, School of Population Health, The University of Western Australia, 3Eye and Vision Epidemiology ResearchGroup, 4Centre for Ophthalmology and Visual Science, University of Western Australia, 5Department of Ophthalmology, Royal PerthHospital, Perth, and 6Population Health, WA Country Health Service – Goldfields, Kalgoorlie, Western Australia, Australia

ABSTRACT

Purpose: To report on diabetic retinopathy (DR) andthe major causes of vision loss and blindness inAboriginals in the Eastern Goldfields region ofWestern Australia between 1995 and 2007.

Methods: Aboriginals (>16 years old) diagnosed withdiabetes or eye problems from 11 communities inthe Eastern Goldfields region of Western Australiawere examined annually from 1995 to 2007. Datacollected from prospective clinical examinationincluded; visual acuity (VA), causes of vision loss,and whether DR was present. Severity of DR wasgraded according to the Early Treatment of DiabeticRetinopathy Study modified Airlie House gradingsystem.

Results: A total of 920 Aboriginals underwent 1331examinations over the study period. There were 246eyes with vision loss (best-corrected VA < 6/12) in159 Aboriginals, of whom five were bilaterally blind.The four major known causes of vision loss werecataract (n = 53, 30.1%), DR (n = 44, 25.0%), uncor-rected refractive error (n = 31, 17.6%) and trauma(n = 19, 10.8%). Aboriginals who had diabetes werefar more likely to have vision loss (odds ratio = 8.5,95% confidence interval 5.7–12.6, P < 0.0001). Ofthe 329 Aboriginals with diabetes, 82 (24.9%)

had DR, and 32 (9.7%) had vision-threateningretinopathy. Of those with diabetes, 94 (42.5%)returned for follow-up examination on an average of3.2 visits with a median time between visits of2 years.

Conclusion: The four major causes of vision loss inAboriginals from the Eastern Goldfields are largelypreventable and/or readily treated. DR and otherdiabetes-related eye conditions are a major cause ofvision loss in Aboriginals, representing a significanthealth challenge for health services and cliniciansinto the future.

Key words: Aboriginal Australian, blindness, diabeticretinopathy, epidemiology, low vision.

INTRODUCTION

The National Trachoma and Eye Health Program(NTEHP) brought awareness to Australian Aborigi-nal eye health in the mid 1970s.1 They reported theprevalence of eye disease among Aboriginal Austra-lians compared with the general population was upto 10 times more common and blindness twiceas common, and that the majority of vision loss wasdue to preventable or treatable conditions.2 Recentstudies have shown little has changed and thatvision loss in Aboriginal people is still due to pre-ventable or treatable conditions including cataract,

� Correspondence: Professor William H Morgan, Centre for Ophthalmology and Vision Science, 2 Verdun Street, Nedlands, WA 6007, Australia. Email:

[email protected]

Received 2 September 2009; accepted 25 January 2010.

Clinical and Experimental Ophthalmology 2010; 38: 475–482 doi: 10.1111/j.1442-9071.2010.02278.x

© 2010 The AuthorsJournal compilation © 2010 Royal Australian and New Zealand College of Ophthalmologists

diabetic retinopathy (DR), uncorrected refractiveerror, trachoma and trauma.3–8

The inclusion of DR as an important cause ofvision loss in Aboriginal communities is new sincethe NTEHP when no cases were reported.1 Diabeteshas become particularly concerning for eye health inAustralian Aboriginals due to its dramatic rise inprevalence in recent decades. Up to 20% of Austra-lian Aboriginals have diabetes compared with 7% inthe general community,9,10 with 25% having somesigns of DR.11 The implications for Aboriginal eyehealth are significant not only due to the expectedincrease in DR but also due to the increase inother diabetes-related eye conditions, for example,cataract, retinal vascular disease and neovascularglaucoma.

Most data on Australian Aboriginal eye healthhave been derived from short-lived cross-sectionalsurveys of remote communities.7,8,12–15 One major dif-ficulty of these surveys is variable ascertainment dueto the transient nature of remote Aboriginal people.The Goldfields Eye Health Survey (GEHS) began in1992 as a yearly public health screening initiative toevaluate and manage eye health problems, namelytrachoma, in Aboriginal communities in the Gold-fields region of Western Australia (WA) (Fig. 1).16 Werealized that repeated examinations of these remotecommunities, whose population is highly mobile,would allow more complete ascertainment of variousdiseases over time. In 1995, DR screening was com-menced and DR grades recorded for all Aboriginals

with diabetes examined. After 16 years, the GEHS isthe longest running Aboriginal eye health survey inAustralia. The aim of this paper is to report on datacollected in the GEHS on DR and the major causes ofvision loss over 12 years in Aboriginals from theEastern Goldfields region of WA.

METHODS

The goldfields eye health survey

All residents of the Eastern Goldfields communitiesvisited in each year were eligible to attend the visit-ing eye clinics. The communities visited are isolatedand scattered across the region and included Kal-goorlie, Coolgardie, Norseman, Coonana, CosmoNewberry, Laverton, Leonora, Menzies, Mt Margaret,Tjuntjunjarra and Wiluna (Fig. 1). The average resi-dent Aboriginal population in the region over thestudy period was 3980 (range 3645–4372) of which1384 resided in remote communities (EpidemiologyBranch, Health Information Collection, Departmentof Health of Western Australia).

The visiting ophthalmology team comprised anophthalmologist, a training ophthalmology registrarand a nurse. Local community nurses and AboriginalHealth Workers (AHW) also assisted during eachvisit. Those who had an eye complaint, visionproblem or who were diabetic were particularlysought out by the visiting team and were transportedto the local community health centre to be examined.

Figure 1. The Eastern Goldfields Eye Health Survey Area, Western Australia.

476 Clark et al.


Those unable to attend, such as the frail or elderly,were seen in their homes.

Where possible all subjects had their visual acuity(VA) measured (with current spectacles if they wereworn); and dilated indirect and direct ophthalmos-copy was performed to examine the posteriorsegment and ocular media. Those with a VA worsethan 6/12 were refracted before dilation.

The logistics of ensuring maximal service deliveryare significant given the size of the area and tran-sience of the local Aboriginal population. The visit-ing team worked very closely with the regionalPublic Health Department and community AHWsand nurses to select the most suitable time to visit.Precise timing was chosen closer to each visit toavoid local ceremonies or cultural events that werelikely to diminish the Aboriginal population avail-able for screening.

Data collection

Clinical information was recorded prospectivelybetween 1995 and 2007 inclusive, except 2000 whenno survey was conducted for logistical reasons. In2003, clinical information was entered into an elec-tronic database and all subsequent survey visitswere recorded on this database. This allowed peoplediagnosed with diabetes in the communities tobe identified in subsequent visits and a reviewinitiated. Approval was obtained from local Aborigi-nal Community Councils in the region for the use,analysis and reporting of the data collected.

Definitions

The presenting VA was that defined as that measuredat the time of each visit on a standard Snellen chart.If spectacles were worn then the VA with the currentcorrection was recorded. Vision impairment (VI) wasdefined as a presenting VA worse than 6/12. Blind-ness was defined as a presenting VA worse than6/60. VI was attributed to refractive error if the best-corrected VA was better than or equal to 6/12. Simi-larly, blindness was attributed to refractive error ifthe best-corrected VA was better than or equal to6/60.

The cause of vision loss in eyes was attributed tothe major disease present. Where two or more dis-eases were present the cause was attributed to thatwhich was felt to be the greatest contributor to visionloss.

The simplified World Health Organization tra-choma grading scheme was used to grade trachoma.17

DR was graded according to the Early Treatment ofDiabetic Retinopathy Study modified Airlie Housegrading system.15 Peripheral DR was graded as

‘mild’, ‘moderate’ or ‘severe’ non-proliferative retin-opathy, and proliferative DR (PDR). Diabetic macu-lopathy was graded as Grade 1 (hard exudateswithin 1 disc diameter of the centre of the macula),Grade 2 (hard exudates or retinal thickening within500 microns of the centre of the macula) or Grade 3(hard exudates or retinal thickening beneath thecentre of the macula). For clinical simplicity, Grade1 maculopathy was categorized as diabetic macu-lar oedema not significant, and Grades 2 and 3 con-sidered together as clinically significant macularoedema (CSME). Patients were considered to havevision-threatening retinopathy (VTR) if severe non-proliferative retinopathy, PDR or CSME was present.

Communities visited were grouped into remoteand non-remote on the basis of their distance fromKalgoorlie (the major centre within the Goldfieldsregion). We considered communities outside a radiusof 250 km from Kalgoorlie as remote, whereas allothers were considered non-remote.

Data analysis

Data were analysed using Stata (Release 10; StataCorporation, College Station, TX, USA). Populationcharacteristics and the major causes of VI were sum-marized using simple descriptive statistics. Categori-cal variables were compared using the chi-squaredstatistic, and Fisher’s exact test where categorieswere less than five. Mean ages at initial visit werecompared using the Student t-test. Trends over timein DR severity and the median time to follow-upwere assessed using the Spearman rank correlationcoefficient.

RESULTS

Study population characteristics are summarized inTable 1. There were 1331 examinations performedon 920 Aboriginals between 1995 and 2007 includ-ing 592 examinations on 329 people with diabetes.The mean age of all participants at their first visitwas 42 years (range 16–89 years), with malesbeing slightly older than females (Mean difference2.4 years, 95% confidence interval [CI] 0.02–4.9,P < 0.05) and diabetics significantly older than non-diabetics (Mean difference 10.7 years, 95% CI 9.72–14.10, P < 0.001.

There were 159 Aboriginals who had one or moreVI or blind eyes (246 eyes), of whom five had bin-ocular blindness (Table 2). In 70 eyes (28.4%) thecauses of VI or blindness was unknown or notrecorded and were excluded from analysis. Impor-tantly, we found no significant difference in theage or sex distribution of this group of patients com-pared with those whose diagnosis was known.

Vision loss and blindness in Aboriginals 477


Aboriginals who had diabetes accounted for 76.1%of patients with vision loss and were significantlymore likely to have vision loss compared with thosewho did not have diabetes (odds ratio = 8.5, 95% CI5.7–12.6, P < 0.001).

The major causes of vision loss are summarized inTable 2. Cataract (28.6%, 95% CI 20.7–35.3), DR (28.6%, 95% CI 20.7–35.3), uncorrected refractive error(21.1%, 95% CI 14.4–27.6) and trauma (5.4%, 95%CI 1.8–9.0) made up the top four causes. There wereonly three vision impaired eyes due to trachoma.There was no significant difference in the causes ofvision loss for men and women.

Trauma accounted for 13 blind eyes (31.0%, 95%CI 16.1–43.9) and was the second most commoncause of blindness after cataract (18 eyes, 38.1%,95% CI 23.3–52.7). DR accounted for seven blindeyes (16.7%, 95% CI 4.9–27.1). There was one blindeye due to trachoma seen in 1997 and none foundsince that time. In those five people who had bin-ocular blindness; two were due to bilateral cataracts,one due to cataract and DR, and one due to trauma inone eye and cataract in the other. The cause of bin-ocular blindness in the last person was not recorded.

The severity of DR in diabetic Aboriginals seen ineach year is summarized in Table 3. Over one-third(35.8%, 95% CI 32.7–38.9) of all patients examinedhad diabetes, with 82 (24.9%, 95% CI 20.3–29.6)showing signs of DR and 32 (9.7%, 95% CI 6.5–2.9)signs of VTR at least once since 1995. The trend inthe proportion who had DR, VTR and CSME showedno significant change over time (Spearman RankP > 0.1) (Fig. 2). Two cases of PDR were seen in1995, and one case in 1997 and 2006. At their firstvisit, 18% (95% CI 14.1–22.4) of diabetics had DR,whereas 7% (95% CI 4.2–9.8) had VTR. Two patientshad PDR at their first visit.

Ninety-four (42.5%, 95% CI 36.0–49.0) Aborigi-nal diabetics from remote communities returned forfollow-up examination at least once over the studyperiod, on an average of 3.2 occasions. Follow-uptime varied across the years (Fig. 3) with the overallmedian time between examinations being 2.0 years(0.7–10.3 years). Less than half (47.9%) of follow-upexaminations occurred within 2 years of the previousexam.

DISCUSSION

There is a relative paucity of recent data regardingthe causes of vision loss in Aboriginal Australians.

Table 1. Characteristics of Aboriginals (>16 years) seen in the Eastern Goldfields Eye Health Survey 1995–2007

All participants(n = 920)

Diabetics(n = 329)

P-value†

Examinations (n) 1331 592Age (years)‡

Male (mean � SD) 43.1 � 15.0 48.5 � 12.2 <0.001Female (mean � SD) 40.7 � 14.7 47.7 � 13.4 <0.001

Female n, (%) 500 (54.4) 195 (59.3) 0.05Remote community n, (%) 520 (56.5) 221 (67.2) <0.001Vision loss n, (%)§ 159 (17.3) 121 (36.8) <0.001

Monocular vision impairment 88 70Monocular blindness 24 22Binocular vision impairment 79 57Binocular blindness 5 5

†P-values are derived from Student’s t-test for continuous variables and chi-squared test for categorical variables comparing thediabetic to non-diabetic population. ‡Age was only available for 595 participants. §Persons may contribute to more than one categoryover the study period.

Table 2. Known causes of blind and VI eyes in Aboriginalsexamined in the Eastern Goldfields Eye Health Survey 1995–2007†

Cause VI eyesn (%)

Blind eyesn (%)

Total eyes‡

n (%)

Cataract 42 (28.6) 16 (38.1) 53 (30.1)Diabetic retinopathy 42 (28.6) 7 (16.7) 44 (25.0)Refractive error 31 (21.1) 0 (0.0) 31 (17.6)Trauma 8 (5.4) 13 (31.0) 19 (10.8)Other 10 (6.8) 3 (7.1) 12 (6.8)Trachoma 3 (2.0) 1 (2.4) 4 (2.3)Pterygium 4 (2.7) 0 (0.0) 4 (2.3)Amblyopia 2 (1.4) 1 (2.4) 3 (1.7)Retinal detachment 2 (1.4) 0 (0.0) 2 (1.1)Retinitis pigmentosa 2 (1.4) 0 (0.0) 2 (1.1)Secondary glaucoma 0 (0.0) 1 (2.4) 1 (0.6)Surgical complication 1 (0.7) 0 (0.0) 1 (0.6)Total 147 (100) 42 (100) 176 (100)

†The cause of vision loss was not recorded for 70 eyes (threeVI eyes, and 68 blind eyes). ‡Eyes may contribute to more thanone category over the study period, for example, VI eyes thathave progressed to blindness. VI < 6/12, �6/60; blind < 6/60. VI,vision impaired.

478 Clark et al.


0.4

0.3

0.2

0.1

0.0

1995 1996 1997 1999 1999 2000 2001 2002 2003 2004 2005 2006 2007Year

Pro

port

ion

of A

borig

inal

s w

ithdi

abet

es m

ellit

us

Figure 2. Trend in the propor-tion of adult Aboriginals with dia-betes with diabetic retinopathyseen in the Eastern GoldfieldEye Health Survey 1995–2007. ( ),any diabetic retinopathy; ( ),vision-threatening retinopathy. (Nosurvey was conducted in 2000.)

10

8

6

4

2

0

Yea

rs s

ince

last

see

n

1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

Year

Figure 3. A Box and whisker plotshowing the trend in follow-up timein Aboriginals with diabetes fromremote communities in the EasternGoldfields Eye Health Survey 1995–2007. Whiskers mark the upperand lower 5% values; ( ) outliers.

Table 3. Severity of DR in Aboriginals with diabetes seen in the Eastern Goldfields Eye Health Survey 1995–2007 (n; %)

Period n DR Severity of diabetic retinopathy

Macula Oedema NPDR

VTRCSME DMENS Mild Mod Severe PDR

1995–1997 152 44 (28.9) 14 (9.2) 7 (4.6) 21 (13.8) 13 (8.6) 4 (2.6) 3 (2.0) 21 (13.8)1998–2001 156 24 (15.4) 6 (3.8) 6 (3.8) 11 (7.1) 6 (3.8) 2 (1.3) 0 (0.0) 8 (5.1)2002–2004 131 29 (22.1) 2 (1.5) 7 (5.3) 20 (15.3) 3 (2.3) 4 (3.1) 0 (0.0) 6 (4.6)2005–2007 118 19 (16.1) 7 (5.9) 2 (1.7) 7 (5.9) 6 (5.1) 4 (3.4) 1 (0.8) 12 (10.2)Whole period 329 82 (24.9) 27 (8.2) 20 (6.1) 49 (14.2) 24 (7.3) 13 (4.0) 3 (0.9) 32 (9.7)At presentation 329 60 (18.2) 19 (5.8) 8 (2.4) 31 (9.4) 15 (4.6) 6 (1.8) 2 (0.6) 23 (7.0)

CSME, clinically significant macular oedema; DMENS, diabetic macular oedema not significant; DR, diabetic retinopathy; NPDR,non-proliferative diabetic retinopathy; PDR, proliferative diabetic retinopathy; VTR, vision-threatening retinopathy (CSME or severe NPRDor PDR).



Ours is the first study to report on the major causes ofvision loss and blindness in an Australian Aborigi-nal population since 1994 and is the first to havecollated these data over a period greater than10 years.

The major causes of VI and blindness in Aborigi-nals in the Goldfields region differ from previousreports between 15–40 years ago.2,4,12 In particular,we found a greater association of vision loss withdiabetes and a lesser association with trachoma.Some similarities remain especially concerning cata-ract, which is a significant cause of vision loss,accounting for nearly one-third of VI eyes and con-tributing substantially to blindness (38%). Althoughthis is an improvement from previous reports, where40–50% of all blindness was due to cataract,2,4 it isstill over twice that reported in the wider Australianpopulation.18 These findings reinforce the impor-tance of continuing cataract surgery delivery to thesecommunities where significant barriers to attendingsurgery are known to exist.19,20

It was encouraging that we found few cases ofvision loss due to trachoma given its prevalence inprevious studies and that it is still endemic in manyremote Australian communities,2–4,12,16,21–23 We havenot seen any new blind eyes due to trachoma since1997, and saw few vision impaired eyes. This repre-sents a significant improvement since the 1970sNTEHP where nearly 10% of Aboriginals had tra-chomatous monocular or binocular blindness.2 Thisis perhaps a reflection of an improvement in livingconditions, better community education regardinghygiene and improved access to antibiotics in theregion.16

Trauma accounted for a significant proportion ofblind eyes examined (>1/3) and changed little overthe study period. Our findings indicate an improve-ment from those of Mann who found trauma was thesecond most common cause of blindness in eyesseen in the Eastern Goldfields region in 1954.12

However, it is higher than reports from otherregions, where approximately one-quarter of blindeyes were due to trauma,2,4 and may be reflectiveof increased interpersonal violence reported inAboriginal communities.24,25

Our study confirms the importance of diabetes as amajor health issue among Australian Aboriginals.We found over 75% of Aboriginals from the EasternGoldfields with vision loss also had diabetes, andthat having diabetes was associated with an 8.5-foldincrease in risk of vision loss from any cause. Interms of DR, a quarter of Aboriginals with diabeteshad signs of DR, which contributed to VI in 20%of eyes. This is higher than previously reported inother Aboriginal communities (Table 4) and is sig-nificantly higher than in the general Australianpopulation.7,8,13–15,18 Our observation of 10% withsigns of VTR at least once over the study period issimilar to that seen in other communities. It is con-cerning that almost 20% diabetics had signs of DRand a third had VTR at their first visit to the eyeclinic. These findings strongly reinforce the need forearly and regular ophthalmic review of all diabeticsin remote Aboriginal communities.

Less than half of all diabetic patients returned forfollow-up and, among those who did, only half wereseen within the recommended 2 years.26 This wasdespite efforts to recall all diabetic patients using ourclinical database. It is possible that these peoplechose not to attend or were elsewhere at the time theclinic visited. The mobile nature of Aboriginal popu-lations is well described,27 whether those whoweren’t in the community at the time of each surveyengaged health services elsewhere is not known.Although we found the use of a clinical database toinitiate patient recall was a useful tool, as it allowedbetter monitoring of known diabetic patients, theimplementation of such a system on a larger scalecould further assist clinicians and health workers inmonitoring patients across different health services.28

Interestingly, there were no cases of primary openangle closure glaucoma or age-related maculardegeneration (ARMD). This compares favourablywith the wider Australian community whereglaucoma and ARMD contribute significantly toblindness.29,30 It could be explained by the relativelyyoung study population and the reduced life expect-ancy of Aboriginal Australians,31 although it sug-gests that there may be reduced susceptibility toglaucoma and ARMD among Aboriginals.

Table 4. Proportion of diabetics seen with DR and VTR in other Aboriginal communities

Author Location Year DR VTR

Durkin et al.11 Remote, South Australia 1999–2004 21% 12%Murray et al.12 Kimberly region, Western Australia 1999–2004 21% 3.5%Diamond et al.13 Pilbara region, Western Australia 1997 23% –Jaross et al.9,10 Katherine region, Northern Territory 1996 21% 8.5%

1993 18% 6.7%Our study Goldfields region, Western Australia 1995–2007 25% 9.7%

DR, diabetic retinopathy; VTR, vision-threatening retinopathy.

480 Clark et al.


Some study limitations exist. We examined 920(~23%) of the approximately 3980 Aboriginals resi-dent in the WA communities visited. Our ascertain-ment of cases was unlikely to be complete at everyvisit since our assessment relied upon voluntaryattendances. The mobility of the Aboriginal commu-nities may have also diminished our ability tocapture the total population at risk.27 The data pre-sented may also be subject to selection bias sinceAboriginal people who had diabetes or had visionproblems were specifically targeted. Therefore, ourdata may over estimate the contribution of diabetes-related eye disease (e.g. cataract and DR). For thesereasons, questions regarding prevalence and trendsover time for the major causes of vision loss could notbe properly answered from our data. However, therepeated annual surveys over 12 years and the use oflocal community health workers to find and bringpatients have likely maximized case ascertainmentwithin each community.

Our findings reinforce those of previous cross-sectional Aboriginal eye health surveys indicatingthe main causes of vision loss in Aboriginal eyes arestill treatable or preventable. There is a clearly a needto assess ophthalmic services provide to these com-munities given readily treated conditions, such ascataract and refractive error, remain important causesof vision loss. We are particularly concerned by thethreat of diabetes to Aboriginal eye health because ofthe strong association with vision loss and that nodemonstrable improvement in retinopathy was seen,even with large local efforts to encourage reviewexaminations. However, it is encouraging to seesignificantly reduced rates of trachoma associatedvision loss compared with reports from 15 or moreyears ago.1,2,4,12

ACKNOWLEDGEMENTS

The authors acknowledge the support received fromthe AHWs, nursing staff and the Aboriginal peoplefrom throughout the Eastern Goldfields communi-ties. We also acknowledge the support and dedica-tion of Dr Charles Douglas from the KalgoorliePublic Health Unit.

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