A comparison of the causes of blindness certifications in England and Wales in working age adults ...

A comparison of the causesof blindness certications in Englandand Wales in working age adults(1664 years), 19992000 with 20092010

Gerald Liew,1,2 Michel Michaelides,1,3 Catey Bunce4

To cite: Liew G,Michaelides M, Bunce C. Acomparison of the causesof blindness certifications inEngland and Wales inworking age adults(1664 years), 19992000with 20092010. BMJ Open2014;4:e004015.doi:10.1136/bmjopen-2013-004015

Prepublication history forthis paper is available online.To view these files pleasevisit the journal online(http://dx.doi.org/10.1136/bmjopen-2013-004015).

Received 12 September 2013Revised 5 December 2013Accepted 24 January 2014

For numbered affiliations seeend of article.

Correspondence toDr Gerald Liew;[email protected]

ABSTRACTObjectives: To report on the causes of blindnesscertifications in England and Wales in working ageadults (1664 years) in 20092010; and to comparethese with figures from 1999 to 2000.Design: Analysis of the national database of blindnesscertificates of vision impairment (CVIs) received by theCertifications Office.Setting and participants: Working age (1664 years) population of England and Wales.Main outcome measures: Number and cause ofblindness certifications.Results: The Certifications Office received 1756 CVIs forblindness from persons aged between 16 and 64inclusive between 1 April 2009 and 31 March 2010. Themain causes of blindness certifications were hereditaryretinal disorders (354 certifications comprising 20.2% ofthe total), diabetic retinopathy/maculopathy (253persons, 14.4%) and optic atrophy (248 persons,14.1%). Together, these three leading causes accountedfor almost 50% of all blindness certifications. Between 1April 1999 and 31 March 2000, the leading causes ofblindness certification were diabetic retinopathy/maculopathy (17.7%), hereditary retinal disorders(15.8%) and optic atrophy (10.1%).Conclusions: For the first time in at least five decades,diabetic retinopathy/maculopathy is no longer the leadingcause of certifiable blindness among working age adults inEngland and Wales, having been overtaken by inheritedretinal disorders. This change may be related to factorsincluding the introduction of nationwide diabetic retinopathyscreening programmes in England and Wales and improvedglycaemic control. Inherited retinal disease, nowrepresenting the commonest cause of certification in theworking age population, has clinical and researchimplications, including with respect to the provision of care/resources in the NHS and the allocation of research funding.

INTRODUCTIONEngland and Wales have collected data onthe number of blind people in the countrysince 1851.1 2 From 1930 until 2003, thecauses of blindness have also been collected

through use of a designated certicate, theBD8, which was completed by the examiningophthalmologist.2 The BD8 was replaced inEngland in September 2005 by the certicateof vision impairment (CVI), and in Wales inApril 2007 by the equivalent form, theCVI-W. One copy each of the CVI and CVI-Wis then sent to the Certications Ofce,London for anonymised epidemiologicalanalysis. The Certications Ofce is currentlyfunded by the Royal National Institute forthe Blind (RNIB) and operates under theauspices of the Royal College ofOphthalmologists with CVI data underCrown copyright, meaning the copyright isowned by the British Government.Although not compulsory, certication

allows patients to be registered (ie, placed onan ofcial local council register) as eitherseverely sight impaired (blind) or sightimpaired (partially sighted), which thenpermits access to certain state benets andsocial service provisions. There is hence anincentive for patients to be certied andcounted, providing an estimate, albeit imper-fect,3 4 of the causes and burden of blindnessin England and Wales. The importance ofthese data is highlighted by the fact that cer-tication gures have recently been adoptedin 2012 as an indicator for preventable sightloss and included in the Public HealthOutcomes Framework.5 In this report, wepresent the ndings from an analysis ofworking age blindness certications from

Strengths and limitations of this study

Strengths of the data include nationwide cover-age, collection of uniform data fields with pre-specified tick boxes, and clear and consistentdefinitions of sight impairment.

Limitations include comparisons across twoslightly different data collection forms.

Liew G, Michaelides M, Bunce C. BMJ Open 2014;4:e004015. doi:10.1136/bmjopen-2013-004015 1

Open Access Research

group.bmj.com on April 27, 2014 - Published by bmjopen.bmj.comDownloaded from

2009 to 2010 and compare these with gures from 1999to 2000.6 Major changes in leading causes of blindnesscertication in this age group have occurred over thisperiod; subsequent publications will report on ndingsin persons of other age groups.

METHODSDetails of data entry, collections and transmission havebeen reported previously.68 Between 1 April 2009 and 31March 2010, data were obtained from CVI forms, whereasbetween 1 April 1999 and 31 March 2000, data wereobtained from BD8 forms. With regard to CVI forms, datawere transcribed from these paper-based forms into a data-base at the Certication Ofce. Part C of the CVI form col-lects information on the causes of visual loss and requiresthe completing ophthalmologist to select from a list ofcommon diagnoses. More than one cause of visual losscan be selected in which case the main cause should behighlighted using either an asterisk or a circle. Guidelinesare provided to assist with this process when the maincause is not evident. Multiple causes are used where theophthalmologist completing the form has not indicated asingle main cause. Possible reasons for this selectioninclude differing causes in the two eyes, or more than onecause within one eye, and the ophthalmologist is unable todetermine which contributes the most to the visual loss.Causes for visual impairment were coded using theInternational Classication of Diseases (ICD)-9 codes andgrouped into disease categories as in previous reports.68

For 19992000, data were extracted from paper-basedBD8 forms in a similar fashion.6 Part 5 of the BD8 formhas 16 elds for medical information including one forthe main cause of visual loss and ve for each eye for con-tributory causes. For records where the main cause wasnot lled, this eld was imputed wherever possible usingan algorithm published previously.8 In short, this algo-rithm brought forward as the main cause the contributingcause if any were so listed; if more than one contributorycause was listed, the patient was listed as having multiplecauses. The main difference between data collected fromthe CVI and BD8 forms is the number of certicationswith multiple causes of visual impairment, which washigher in the CVI forms.7 We have previously minimisedbias from this source by re-examining the certicates withmultiple causes, extracting the contributory causes listedand tabulating them with the main causes.7 We follow thesame procedure in this report.Blindness was dened according to criteria previously

described on the BD8 and CVI forms as either best cor-rected visual acuity in the better eye of either (1) worsethan 3/60 or (2) worse than 6/60 with severely con-stricted visual elds or (3) better than 6/60 with severelyconstricted visual elds, particularly the inferior eld.

AnalysesData regarding the main cause of visual impairmentwere extracted from the forms and grouped into disease

categories as previously described.68 For CVI data, thosewith multiple causes or no information on maincause of visual impairment had contributory causesextracted and listed, which were later combined with themain causes. Pie and bar charts were used to graphicallyillustrate the distribution of the main causes of visualimpairment. Proportions of blindness registrations dueto each cause are presented rather than adjusted inci-dence rates in order to indicate the relative contributionof each condition to the pool of vision impairment.Currently, almost every grant application for diabetic ret-inopathy projects starts with a statement that diabeticretinopathy is the most common cause of visual loss inthe working age populationwe present proportions ofblindness registrations to determine if this statementremains valid. 2 tests were performed to test differencesin proportions.

RESULTSFor the period 1 April 2009 to 31 March 2010, theCertications Ofce received 1756 CVIs for blindnessfrom persons aged between 16 and 64 inclusive. Thiscompares with 1637 BD8 forms for blindness receivedbetween 1 April 1999 and 31 March 2000, details ofwhich have been reported previously.8 Table 1 shows thenumber of persons certied blind for each of thedisease categories. Hereditary retinal disorders, includ-ing Stargardt disease and retinitis pigmentosa, formedthe largest category with 354 certications comprising20.2% of the total. Diabetic retinopathy/maculopathywas the second largest cause of certiable blindness with253 persons (14.4%), followed by optic atrophy with 248persons (14.1%). Together, these three leading causesaccounted for almost 50% of all blindness certicationsin the working age group. Glaucoma was responsible for104 (5.9%) blindness certications, followed by congeni-tal abnormalities of the eye, which included congenitalcataracts and retinopathy of prematurity (89 certica-tions, 5.1%). Multiple pathologies were listed for 242persons (13.8%) and no information on the main causewas listed for 42 persons (2.4%). When these categorieswere examined for contributory causes, the mostcommon contributory causes recorded were glaucoma(60 persons), diabetic retinopathy/maculopathy (56persons) and optic atrophy (46 persons). Combiningthe main and contributory causes resulted in smallchanges in the overall proportion of certications due tospecic causes, but did not change the relative rankingsof the top six causes of blindness (table 1). Other con-ditions comprised 150 certications (8.5%), of whichthe most common were malignant neoplasms of thebrain and nervous system (27 persons, 1.5%) and retinaldetachments (24 persons, 1.4%). Figure 1 shows the dis-tribution of the causes of blindness certications graph-ically in a pie chart.We next compared the main causes of blindness certi-

cations from 1999 to 2000 (n=1637) with the gures

2 Liew G, Michaelides M, Bunce C. BMJ Open 2014;4:e004015. doi:10.1136/bmjopen-2013-004015

Open Access


above from 2009 to 2010 (n=1756). The results areshown graphically in gure 2. From 1999 to 2000, theleading cause of blindness certication was diabetic ret-inopathy/maculopathy, which accounted for 290 certi-cations (17.7%). By 20092010, this gure haddecreased to 253 (14.4%), and diabetic retinopathy/

maculopathy was now the second leading cause of blind-ness certication. This difference was statistically signi-cant (p=0.009). In contrast, hereditary retinal disorders,which were the second leading cause of blindness certi-cation in 19992000, accounting for 258 cases (15.8% oftotal), had increased to 354 cases (20.2%) by 20092010and have now become the leading cause of certiableblindness in the working age group in England andWales. Optic atrophy remained the third leading causein 19992000 and 20092010 with an increase from 165cases (10.1%) to 248 cases (14.1%), respectively.A notable nding was that degeneration of the maculaand posterior pole, which accounted for 7.7% of blind-ness registration in 19992000, had dropped in percent-age terms and now accounted for only 3% by20092010. Other causes of blindness registrationremained roughly similar for the two time periods.

DISCUSSIONThis report provides updated estimates on the causes ofcertiable blindness in England and Wales in workingage adults. Three main diseases were responsible forhalf of all certicationshereditary retinal disorders(20.2%), diabetic retinopathy/maculopathy (14.4%)and optic atrophy (14.1%). A marked change hasoccurred in the relative importance of these maincauses of blindness certications since the last majoranalysis in 19992000,6 with diabetic retinopathy/macu-lopathy now no longer the leading cause of blindness inworking age adults. Since at least 1963,9 diabetic retinop-athy/maculopathy has been the leading cause of

Table 1 Numbers of working age adults (age 1664) with severe sight impairment (blindness) in England and Wales:certifications 20092010

ICD-9codes Diagnosis

Main cause(% total)

Contributory cause(% total)

Combined(% total)

362.7 Hereditary retinal disorders 354 (20.2) 29 (6.6) 383 (20.0)362/34 000 Diabetic retinopathy/maculopathy 253 (14.4) 56 (12.8) 309 (16.2)377.1 Optic atrophy 248 (14.1) 46 (10.5) 294 (15.4)365 Glaucoma 104 (5.9) 60 (13.7) 164 (8.6)743760 Congenital abnormalities of the eye 89 (5.1) 32 (7.3) 121 (6.3)377.7 Disorders of the visual cortex 72 (4.1) 24 (5.5) 96 (5.0)430438 Cerebrovascular disease 56 (3.2) 21 (4.8) 77 (4.0)362.5 Degeneration of the macula and posterior

pole52 (3.0) 14 (3.2) 66 (3.5)

360.2 Myopia 49 (2.8) 23 (5.2) 72 (3.8)370371 Corneal disorders 45 (2.6) 34 (7.7) 79 (4.1) Multiple pathology 242 (13.8) - - Other conditions 150 (8.5) 100 (22.8) 250 (13.1) No information on main cause 42 (2.4) Total 1756 439* 1911*The Main cause column lists the number of certifications with the corresponding diagnosis; the Contributory cause column lists thecontributory causes in certifications from the Multiple pathology and No Information on main cause categories.ICD, the International Classification of Disease.*Including contributory causes. The total number of contributory causes is greater than the sum of Multiple pathology and No informationon main cause categories because persons can have between one and four contributory causes documented.

Figure 1 Main causes of severe sight impairment(blindness) in England and Wales in working age adults (age1664): certifications 20092010.


Open Access


blindness among working age adults in England andWales; a similar situation exists in other developed coun-tries such as the USA.10 Over the past decade, the pro-portion of certications for hereditary retinal disordershas risen slowly,8 while that for diabetic retinopathy/maculopathy has reduced, resulting in the two condi-tions swapping rankings.This report is not designed to identify the reasons

behind these changes or estimate the incidence of blind-ness from diabetes. The prevalence of diabetes in the UKis not known with certainty, with several limited generalpractice surveys suggesting a range of between 1% and 2%of the general population1114; we are thus not able to esti-mate the incidence of blindness from diabetes.Nonetheless, available data suggest that the prevalence ofdiabetes in England and Wales has increased over theperiod in question,11 13 which would be expected to leadto increased rates of blindness if other factors remainedconstant. In this context, we speculate that several inter-vening public health developments may have contributedto the reduction in absolute and proportional rates ofregistrable blindness from diabetes among working ageadults. Between 2003 and 2008, England and Wales intro-duced nationwide diabetic retinopathy screening serviceswith the aim of reducing the incidence of blindness fromdiabetic eye disease. These are known as the NationalHealth Service (NHS) Diabetic Eye Screening Program(England)15 and Diabetic Retinopathy Screening ServiceWales (DRSSW),16 and these programmes annually screenalmost 2 million and 150 000 patients with diabetes,respectively. Concurrent with these screening

programmes, in 2004 the Quality and OutcomesFramework17 was introduced to incentivise general practi-tioners in the UK to improve primary care management ofseveral conditions including diabetes. Several studies havedocumented an improvement in the quality of care for dia-betes since this was introduced,18 19 and the effort mayhave contributed to the improvement in glycaemic controldocumented since the late 1990s.17 20 The decline in theabsolute number and relative proportion of blindness cer-tications due to diabetic retinopathy/maculopathyamong working age adults since the introduction of thesepublic health measures may be an indicator of their effect-iveness. Nonetheless, this remains speculative at present,and such explanations should be read with caution.Whether increased numbers of certication for inher-

ited eye diseases reect improved certication of existingsight impairment or a true increase in incidence ofthese disorders is unclear. The progress made over thelast decade in molecular genetics/diagnostics and theincreasing avenues of research/clinical trials for inher-ited retinal disease with widespread media coverage mayplausibly have resulted in higher community awarenessand increased clinic visits and thereby registration,4

without a true increase in incidence rates. An observa-tion in favour of this scenario is that the numbers ofblindness certication for optic atrophy have alsoincreased over the last decade, in tandem with those forinherited retinal disease, while those for other non-inherited conditions such as glaucoma have remainedfairly constant. Hereditary retinal diseases occur morefrequently in communities with a higher rate of

Figure 2 Ten-year change incauses of severe sightimpairment (blindness) inEngland and Wales in workingage adults (age 1664):certifications 19992000 and20092010.


Open Access


consanguinity, and it is conceivable that increased ratesof immigration from countries where consanguinity ismore prevalent may have contributed to these ndings,though at this stage this remains speculative. Anotherpossibility is that diagnostic transfer or misclassicationmay have occurred, for example, where some cases ofhereditary retinal disorders may have been mislabelledas degeneration of macula and posterior pole. In orderto explain the increase in hereditary retinal disorders,this would have had to occur preferentially in 19992000versus 20092010. However, misclassication of diabeticretinopathy/maculopathy as hereditary retinal disordersis unlikely to occur given how different the conditionsare, and so would not explain the absolute reduction inthe number of certications for blindness due todiabetes.These ndings have implications for clinical care and

research budget allocation. A prolonged focus on preven-tion and treatment of diabetic eye disease has most likelycontributed to the decline in blindness certications fromthis disorder among working age adults, and the rate isexpected to decline further with the recent NationalInstitute for Clinical Excellence (NICE) approval of ranibi-zumab for treatment of diabetic maculopathy. Now thathereditary retinal diseases comprise the leading cause ofblindness certications in working age adults, an increasedfocus on clinical management of these conditions (eg,with low vision aids and visual rehabilitation) and greaterallocation of research funding to study these disordersmay be appropriate. Funding bodies may need to reassesstheir funding priorities.

Strengths and limitationsData from BD8 and CVI registrations represent some ofthe best available epidemiological data on sight impair-ment in England and Wales and are regarded as a majorpublic health indicator.5 Strengths of the data includenationwide coverage, collection of uniform data eldswith prespecied tick boxes, and clear and consistentdenitions of sight impairment.Limitations that should be highlighted include the fact

that blindness certications are not equivalent to blindnessrates. This has been discussed previously,3 4 and it is esti-mated that up to 53% of eligible patients may not be regis-tered blind despite consultation with an ophthalmologist.7

However, arguments have been advanced that in time,most patients eligible to be registered will in fact do so,7

and studies have shown a major increase in registrationrates with increasing clinic visits.4

Another caveat to these results is that some patientswho are certied blind may not always satisfy all of theofcial criteria, with one study suggesting an inappropri-ate blindness certication rate of 23%.3 Suchinappropriate certications may inate the numberssomewhat, but it should be borne in mind that the aimof certication is not to identify persons meeting rigidclinical criteria but to identify and count those with sig-nicant visual impairment who may benet from state

assistance. Indeed, current guidelines for completion ofCVI forms state that the criteria should be interpretedin the context of the patients functional status ratherthan as strict cut-offs. Another precaution when inter-preting these results is that the gures for the two timeperiods were collated from different forms. The differ-ences in these forms are discussed elsewhere,7 and oneof the main complications in comparing temporaltrends is the increase in the number of forms where amain cause has not been identied. In the 19992000dataset, which was derived from BD8, approximately 4%of forms had multiple pathology; in the 20092010dataset derived from CVI, this had increased to 14%.This raised the possibility that diabetic retinopathy/maculopathy may have been under-reported for the20092010 period. We attempted to address this byexamining the contributory causes in those without amain cause recorded and using these in place of themissing main cause; this analysis resulted in only smallchanges to the percentage of blindness due to eachcause and did not change the overall ranking of the topsix causes. This suggests that the rate of under-reportingof main causes was similar for most categories and notresponsible for the shift in the leading causes of blind-ness certications.In summary, this report found that three main causes

were responsible for half of all blindness certicationsamong working age adults in England and Wales from2009 to 2010hereditary retinal disorders (20.2%), fol-lowed by diabetic retinopathy/maculopathy (14.4%) andoptic atrophy (14.1%). This marks the rst time inalmost ve decades that diabetic retinopathy/maculopa-thy is no longer the leading cause of blindness inworking age adults, which may be related to the intro-duction of nationwide public health measures inEngland and Wales. The results have implications forresource allocations for clinical care delivery andresearch.

Author affiliations1Moorfields Eye Hospital NHS Foundation Trust, London, UK2Centre for Vision Research, Westmead Millennium Institute, University ofSydney, Sydney, Australia3Department of Genetics, University College London, Institute ofOphthalmology, London, UK4National Institute for Health Research Biomedical Research Centre atMoorfields Eye Hospital NHS Foundation Trust and UCL Institute ofOphthalmology

Contributors GL, MM and CB have contributed to (1) conception and design,acquisition of data, and analysis and interpretation of data; (2) drafting of thearticle and revising it critically for important intellectual content and (3) givenfinal approval of the version to be published.

Funding This study was supported by grants from the RNIB and the NationalInstitute for Health Research Biomedical Research Centre at Moorfields EyeHospital NHS Foundation Trust and UCL Institute of Ophthalmology. The datacaptured by CVI are DH copyright and this work was made possible bycollaboration with the Royal College of Ophthalmologists.

Competing interests MM is a recipient of a Foundation Fighting BlindnessCareer Development Award.


Open Access


Provenance and peer review Not commissioned; externally peer reviewed.

Data sharing statement Technical appendix, statistical code and datasetavailable from the corresponding author or at the Dryad repository, which willprovide a permanent, citable and open access home for the database.

Open Access This is an Open Access article distributed in accordance withthe Creative Commons Attribution Non Commercial (CC BY-NC 3.0) license,which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, providedthe original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/3.0/

REFERENCES1. Sorsby A. The causes of blindness in England 1948-50. London,

HMSO, 1953.2. Sorsby A. The incidence and causes of blindness in England and

Wales 1948-1962. 178. 1966. London, HM Stationery Office.Reports on Public Health and Medical Subjects No. 114.

3. Barry RJ, Murray PI. Unregistered visual impairment: is registration afailing system? Br J Ophthalmol 2005;89:9958.

4. Robinson R, Deutsch J, Jones HS, et al. Unrecognised andunregistered visual impairment. Br J Ophthalmol 1994;78:73640.

5. UK Department of Health. Healthy lives, healthy people: improvingoutcomes and supporting transparency. 2012.

6. Bunce C, Wormald R. Causes of blind certifications in England andWales: April 1999-March 2000. Eye 2008;22:90511.

7. Bunce C, Wormald R. Leading causes of certification for blindnessand partial sight in England & Wales. BMC Public Health 2006;6:58.

8. Bunce C, Xing W, Wormald R. Causes of blind and partial sightcertifications in England and Wales: April 2007-March 2008. Eye2010;24:16929.

9. Sorsby A. The incidence and causes of blindness tn England andWales 19631968. 1972. London: HM Stationary Office. DHSSreports on public health and medical subjects No 128.

10. Centers for Disease Control and Prevention. http://www.cdc.gov/visionhealth/basic_information/eye_disorders.htm [2013 (cited 2013Jul 20).

11. Lusignan S, Sismanidis C, Carey IM, et al. Trends in the prevalenceand management of diagnosed type 2 diabetes 1994-2001 inEngland and Wales. BMC Fam Pract 2005;6:13.

12. Khunti K, Goyder E, Baker R. Collation and comparison ofmulti-practice audit data: prevalence and treatment of knowndiabetes mellitus. Br J Gen Pract 1999;49:3759.

13. Holman N, Forouhi NG, Goyder E, et al. The Association of PublicHealth Observatories (APHO) Diabetes Prevalence Model:estimates of total diabetes prevalence for England, 2010-2030.Diabet Med 2011;28:57582.

14. Forouhi NG, Merrick D, Goyder E, et al. Diabetes prevalence inEngland, 2001estimates from an epidemiological model. DiabetMed 2006;23:18997.

15. NHS Diabetic Eye Screening Programme 2013. http://diabeticeye.screening.nhs.uk/about

16. Diabetic Retinopathy Screening Service Wales 2013. http://www.cardiffandvaleuhb.wales.nhs.uk/drssw

17. Calvert M, Shankar A, McManus RJ, et al. Effect of the quality andoutcomes framework on diabetes care in the United Kingdom:retrospective cohort study. BMJ 2009;338:b1870.

18. Campbell SM, Reeves D, Kontopantelis E, et al. Effects of pay forperformance on the quality of primary care in England. N Engl JMed 2009;361:36878.

19. Millett C, Saxena S, Ng A, et al. Socio-economic status, ethnicityand diabetes management: an analysis of time trends using thehealth survey for England. J Public Health (Oxf ) 2007;29:41319.

20. Oluwatowoju I, Abu E, Wild SH, et al. Improvements in glycaemiccontrol and cholesterol concentrations associated with the Qualityand Outcomes Framework: a regional 2-year audit of diabetes carein the UK. Diabet Med 2010;27:3549.


Open Access


doi: 10.1136/bmjopen-2013-004015 2014 4: BMJ Open

Gerald Liew, Michel Michaelides and Catey Bunce

2010with 20092000years), 1999 64working age adults (16

certifications in England and Wales in A comparison of the causes of blindness

http://bmjopen.bmj.com/content/4/2/e004015.full.htmlUpdated information and services can be found at:

These include:

References http://bmjopen.bmj.com/content/4/2/e004015.full.html#ref-list-1

This article cites 13 articles, 5 of which can be accessed free at:

Open Access

non-commercial. See: http://creativecommons.org/licenses/by-nc/3.0/terms, provided the original work is properly cited and the use iswork non-commercially, and license their derivative works on different license, which permits others to distribute, remix, adapt, build upon thisCreative Commons Attribution Non Commercial (CC BY-NC 3.0) This is an Open Access article distributed in accordance with the

serviceEmail alerting

the box at the top right corner of the online article.Receive free email alerts when new articles cite this article. Sign up in

CollectionsTopic

(626 articles)Public health (36 articles)Ophthalmology

Articles on similar topics can be found in the following collections

Notes

http://group.bmj.com/group/rights-licensing/permissionsTo request permissions go to:

http://journals.bmj.com/cgi/reprintformTo order reprints go to:

http://group.bmj.com/subscribe/To subscribe to BMJ go to:


A comparison of the causes of blindness certifications in England and Wales in working age adults (1664 years), 19992000 with 20092010AbstractIntroductionMethodsAnalyses

ResultsDiscussionStrengths and limitations

References

A comparison of the causes of blindness certifications in England and Wales in working age adults ...

Documents

Transcript of A comparison of the causes of blindness certifications in England and Wales in working age adults ...