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Clinical guidelines

National guide to a preventive health assessment for Aboriginal and Torres Strait Islander people Second edition

Visual acuity

Author Dr Jacki Mein
Expert reviewer Professor Hugh Taylor

Background

Good eye health is critical to quality of life. Impaired vision, which is defined as a visual acuity (VA) <6/12,1 often goes unrecognised and contributes significantly to morbidity.2 Visual impairment is a risk factor for falls.3 In the elderly, untreated cataracts increase the risk of multiple falls,4 social isolation and depression.5 The 2009 National Indigenous Eye Health Survey included a sample of Aboriginal and Torres Strait Islander adults in urban, regional and remote settings.1 The age adjusted prevalence of low vision was 8.6%, 2.8 times higher than rates for non-Indigenous adults. Low vision prevalence is higher in remote and very remote areas, ranging from 9.5–12.7%. The sampling adjusted prevalence of blindness (VA <6/60 in the better eye, and/or combined both eyes visual field of less than 10 degrees – in normal sighted people this is 170 degrees6) was 1.8%. The major causes of blindness are cataract (32%), optic atrophy (14%), refractive error (14%), diabetes (9%) and trachoma (9%).1 The rate of blindness was 6.2 times higher than in non-Indigenous Australians.

The dominant cause of low vision is refractive error (54%) with prevalence rates around five times higher than for non-Indigenous adults. Over a third of National Indigenous Eye Health Survey participants (39%) could not read normal size print, and 62% reported they normally wore reading glasses for near-work (eg. reading, sewing). Other important causes of low vision include cataract 27% and diabetic retinopathy (12%).

Risk factors for cataract include ocular exposure to ultraviolet light,7,8 diabetes and poor diabetic control,9 and smoking. In a recent Australian study, ‘ever smokers’ had a 41% increased risk of developing nuclear cataract compared to never smokers.10 Reduction of ocular sun exposure with sunglasses may assist. Although exposure to sunlight accounts for only 10% of cataracts in an urban non-tropical Australian population,7 this risk factor may be more important in northern Australian populations.

The National Indigenous Eye Health Survey found 37.4% of Aboriginal and Torres Strait Islander adults reported having diabetes with a similar prevalence across all the regions sampled. Of these, 12% had low vision and only 20% reported an eye examination in the past 12 months. A total of 2.5% had proliferative retinopathy, 0.4% severe non-proliferative retinopathy, and 25% mild/moderate non-proliferative retinopathy. Of these, only 39% had received some laser treatment.1 Although diabetes is a risk factor for cataract there is no robust evidence that improved diabetic treatment prevents or delays lens opacity.11 

Evidence for the effectiveness of preventive interventions

Recommendations for the school based screening of visual acuity in children in non-trachoma endemic areas lack a research base for evidence of effectiveness. An Australian based expert group suggests screening for age problems on at least three occasions: birth and 3–6 months, both to pick up serious congenital conditions; and screening at 4 years to check visual acuity and refer if either eye is worse than 6/9, or if there is a two-line difference in results for both eyes.12

Visual acuity screening is advocated in older adults because refractive errors are correctable with eyeglasses and have good outcomes with refractive surgery if available.13 The US Preventive Services Task Force concludes that there is insufficient evidence to assess benefits and harms of screening for visual acuity in adults over 65 years of age.14 However, given the substantially higher prevalence of low vision in Aboriginal and Torres Strait Islander communities, there is a reasonable justification for visual acuity screening at younger ages. Vision assessments are components of Medicare health assessments for all age groups. The CARPA standard treatment manual recommends visual acuity screening in Aboriginal and Torres Strait Islander populations aged 50 years or more,15 while the Queensland chronic disease guidelines recommend screening as part of Aboriginal and Torres Strait Islander health assessments from 40 years.16

The Snellen eye chart is a highly sensitive and specific recommended screening test for visual acuity testing and is more sensitive than screening questions.17 The E-test visual acuity charts for near and distance vision are useful for people who cannot read and were used routinely in the National Indigenous Eye Health Survey.1 However, of even greater importance is the need to test near or ‘reading’ vision, especially in those aged over 40 years. The National Indigenous Eye Health Survey found that 40% of Aboriginal and Torres Strait Islander adults could not see normal sized print. Near vision test cards or any printed matter can be used to test near vision and E-tests for near vision can also be used for people who cannot read.

Cataract surgery has been shown to improve vision17,18 and quality of life.18 It has also been associated with fewer vehicle accidents after cataract surgery.19 The National Indigenous Eye Health Survey found evidence of disparities in access to cataract surgery, with only 65% of Aboriginal and Torres Strait Islander adults with vision loss from cataract having received surgery with more remote people having less operations, compared with 89% of non-Indigenous adults.1 One study showed an increased risk of death in those not having cataract surgery.20 A case record audit in the Northern Territory found cataract surgery had a beneficial effect on visual acuity and quality of life for Aboriginal and Torres Strait Islander people.21 While most people in this cohort were legally blind, surgery should be performed when visual acuity is worse than 6/12 or when patient function is impaired, although there are questions in the urban Australian context about patient selection for cataract surgery to maximise good outcomes.22

For people with diabetes, an annual visual acuity assessment and dilated fundus/retinal camera examination by a trained examiner is recommended for routine diabetic retinopathy screening.23 Early laser photocoagulation treatment can prevent progression and save sight.24 In fact 98% of the blindness due to diabetes can be prevented and yet only 20% of those with diabetes had had the required annual eye examination in the National Indigenous Eye Health Survey. Good glycaemic, lipid and blood pressure control and early treatment of any diabetic retinopathy remain the cornerstone of primary prevention and delay of progression of diabetic retinopathy.25,26 

Recommendations: Visual acuity
Preventive intervention typeWho is at risk?What should be done?How often?Level/strength of evidence
Screening Infants aged <6 months Conduct a general eye examination. Refer if red eye reflex absent or other abnormality found As part of a newborn and 3–6 month health assessment GPP12
Children aged 4–5 years Screen for visual acuity (VA) (use E chart if required)
Refer if VA is less than 6/9 or there is a two line difference between eyes
Opportunistic and once only at routine health assessment GPP12
All adults aged >40 years
People with poor near-vision (presbyopia)
Near and far visual acuity assessment is recommended to detect visual loss due to presbyopia or cataract Annually as part of an adult health assessment GPP15–17,27
The use of near test material and Snellen chart (and E chart if required) is recommended for testing visual acuity
If unable to see normal sized print (type) refer to optometrist or ophthalmologist for assessment and probable reading glasses
Snellen IC
E chart IIIC
People with cataract If visual acuity is worse than 6/12 or when function is impaired refer to an ophthalmologist for assessment and possible cataract surgery Opportunistic GPP22
People with diabetes Undertake visual acuity and retinal assessment by trained assessor as indicated in diabetic management guidelines  Annually IA26
Retinal photography by trained primary care staff combined with external review by an ophthalmologist is a useful strategy for comprehensive screening GPP26,28
Behavioural Current smokers Advise smoking cessation to reduce the risk of developing cataracts (see Chapter 1: Lifestyle, section on smoking) Opportunistic IIIC10
All people Recommend reduced ocular exposure to UV-B light to reduce risk of cataract (eg. wearing sunglasses) Opportunistic IIIC7,8

References

  1. National Indigenous Eye Health Survey Team. Minum Barreng (tracking eyes) full report: National Indigenous Eye Health Survey, version 2. NIEHS, 2009. Cited October 2011. Available at www.iehu.unimelb.edu.au/ publications/the_national_indigenous _eye_health_survey.
  2. United States Preventive Services Task Force. Guide to clinical preventive services. Report of the USPSTF, 2nd edn. Baltimore: Williams and Wilkins, 1996.
  3. Nevitt M, Cummings SR, Hudes ES. Risk factors for injurious falls: a prospective study. J Gerontol 1991;46:M164–70.
  4. Ivers R, Cumming RG, Mitchell P, Attebo K. Visual impairment and falls in older adults: The Blue Mountains eye study. J Am Geriatr Soc 1998;46:58–64.
  5. Taylor HR, Pitkin J, Cass DT. Updates in medicine: ophthalmology. Med J Aust 2002;176(29).
  6. Retina Australia. Legal blindness Australian definition. Retina Australia, 2009. Cited October 2011. Available at www.retinaaustralia.com.au/ legal_blindness.htm.
  7. McCarty CA, Taylor HR. A review of the epidemiologic evidence linking ultraviolet radiation and cataracts. Dev Ophthalmol 2002;35:21–31.
  8. West S. Ocular ultraviolet B exposure and lens opacities: a review. J Epidemiol 1999;(6 Suppl):S97-101.
  9. Robman L, Taylor HR. External factors in the development of cataract. Eye 2005;19(10):1074–82.
  10. Tan JS, Wang JJ, Younan C, Cumming RG, Rochtchina E, Mitchell P. Smoking and the long-term incidence of cataract: the Blue Mountains Eye Study. Ophthalmic Epidemiol 2008;15(3):155–61.
  11. Congdon NG. Prevention strategies for age related cataract: present limitations and future possibilities. Br J Ophthalmol 2001;85(5):516–20.
  12. Centre for Community Child Health. National Children’s Vision Screening Project discussion paper. Melbourne: Centre for Community Child Health, 2008.
  13. Murray A, Jones L, Milne A, Fraser C, Lourenço T, Burr J. A systematic review of the safety and efficacy of elective photorefractive surgery for the correction of refractive error. Aberdeen: Health Services Research Unit, University of Aberdeen, 2005. Cited October 2011. Available at www.nice.org.uk/ nicemedia/live/11251/31559/31559.pdf.
  14. US Preventive Services Task Force. Screening for impaired visual acuity in older adults: recommendation statement. Ann Intern Med 2009;151:37–43.
  15. Central Australian Rural Practitioners Association. CARPA standard treatment manual, 5th edn. Alice Springs, NT: CARPA, 2009.
  16. Queensland Health and the Royal Flying Doctor Service (Queensland Section). Chronic disease guidelines, 2nd edn. Brisbane: Queensland Health, 2007.
  17. Chou R, Dana T, Bougatsos C. Screening for visual impairment in older adults: systematic review to update the 1996 US Preventive Services Task Force Recommendation. Evidence Synthesis no. 71. AHRQ Publication No. 09-05135-EF-1. Rockville: Agency for Healthcare Research and Quality, 2009.
  18. Powe NR, Schein OD, Gieser SC, et al. Synthesis of the literature on visual acuity and complications following cataract extraction with intraocular lens implantation. Cataract Patient Outcome Research Team. Arch Ophthalmol 1994;112:239–52.
  19. Owsley C, McGwin G Jr, Sloane M, Wells J, Stalvey BT, Gauthreaux S. Impact of cataract surgery on motor vehicle crash involvement by older adults. JAMA 2002;288:841–9.
  20. McGwin G Jr, Owsley C, Gauthreaux S. The association between cataract and mortality among older adults. Ophthalmic Epidemiol 2003;10:107–19.
  21. Hewitt A, Verman N, Gruen R. Visual outcomes for remote Australian Aboriginal people after cataract surgery. Clin Experiment ophthalmol 2001;29(2):68–74.
  22. Pager CK, McCluskey PJ, Retsas C. Cataract surgery in Australia: a profile of patient-centred outcomes. Clin Experiment ophthalmol 2004;32(4):388–92.
  23. Centre for Eye Research Australia. Diabetic retinopathy. Melbourne: CCERA, 2008. Cited October 2011. Available at www.cera.org.au/ uploads/CERA_factsheet_ DiabeticRetinopathy.pdf.
  24. Mohamed Q, Gillies MC, Wong TY. Management of diabetic retinopathy: a systematic review. JAMA 2007;298(8):902–16.
  25. Klein R, Klein BE, Moss SE, Davis MD, DeMets DL. Glycosylated hemoglobin predicts the incidence and progression of diabetic retinopathy. JAMA 1988;260:2864–71.
  26. National Health and Medical Research Council. Guidelines for the management of diabetic retinopathy. Canberra: Commonwealth of Australia, 2008.
  27. Keeffe JE, Lovie-Kitchin JE, Maclean H, Taylor HR. A simplified screening test for identifying people with low vision in developing countries. Bull World Health Organ 1996;74(5):525–32.
  28. Murray RB MS, Lewis PM, Mein JK, McAllister IL. Sustaining remote-area programs: retinal camera use by Aboriginal health workers and nurses in a Kimberley partnership. Med J Aust 2005;182(10):520–3.
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