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Screening and early referral: Essential elements in the management of macular degeneration

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Macular degeneration is the number one cause of vision loss in the world today.1 It accounts for approximately 50% of visual impairment globally and is associated with a range of visual problems, most often manifesting with difficulty conducting tasks that require sharp focus.2 Early recognition of the signs and symptoms as well as prompt referral are vital in order to determine the course of management and improve visual outcomes.1

Macular degeneration: One name for several types

Macular degeneration is an overarching term that refers to several different conditions classified according to the disease process.

Dry macular degeneration is the most common type and typically follows a slow course. Often a gradual progression of vision loss over several years is reported.3

Wet, or exudative, macular degeneration is the other main type. This form is characterised by choroidal neovascularisation and leakage of the new vessels, resulting in subretinal fluid, haemorrhage and ultimately scarring with loss of vision. Typically, this process occurs much more rapidly than the dry form, and while it is far less common, it accounts for over 90% of the total vision loss caused by macular degeneration.3

Diabetic maculopathy is another type of macular degeneration. It occurs when a person has diabetic retinopathy that extends to affect the macular region of the retina.4

Just like global trends, macular degeneration in Australia is the leading cause of severe visual impairment in the elderly.5 It is estimated that 15% of the total population over 50 years of age are affected by early changes at the macular.6


Understanding the risk factors

Extensive studies have been done on why some people develop macular degeneration over others. We now know that there are a number of factors influencing the development macular degeneration. Knowledge of some of these factors may help to target preventative strategies.

Julie Heraghty, Macular Degeneration Foundation CEO, said:

“Smoking is a key modifiable risk factor for macular degeneration. Studies have shown that those who smoke are three times more likely to develop MD, and smokers may also develop the disease ten years earlier than non-smokers. Patients who smoke should be educated in this matter, not only so they can be screened for the disease but to encourage their cessation of smoking.”

Dietary and lifestyle factors also play a role in the development of macular degeneration. Findings from some studies indicate that regular physical activity is protective against macular degeneration.9 Associations between high glycaemic index diets and macular degeneration have also been reported.2 Therefore a healthy, well-balanced diet high in fish, green leafy vegetables, fruits and nuts is recommended.

Age, genetic conditions and family history are strong non-modifiable risk factors influencing the development of macular degeneration. The risk of symptomatic, sight-threatening macular degeneration rises considerably with age, with the condition most often seen in those over 50 years, and rates increasing with age.3 Mutations in several genes are also thought to be involved,10 however more research is warranted to gain a deeper understanding of the genetic origins. Family history is strongly linked to macular degeneration, and individuals whose family members are affected are at a much higher risk of developing the condition.11,12

Medical literature is constantly evolving and changing; therefore, there are also a number of possible risk factors for developing macular degeneration in cases where the evidence is inconclusive. Interestingly, possible associations have been established between the risk of developing macular degeneration and cataract surgery,13,14 hypertension,15 blue iris colour, and sunlight exposure.16


Detecting the signs and symptoms

Screening is an essential component of early detection and treatment. The screening process in anyone with risk factors or suspected macular degeneration involves a thorough clinical history and examination.17

Dry macular degeneration typically presents with a history of difficulty reading small newsprint, the need for brighter lighting, blurry vision, or difficulty judging distances. Colours may be dimmer and harder to differentiate. Patients with suspected dry macular degeneration should be referred for assessment by an ophthalmologist.17

Wet macular degeneration is characterised by a more dramatic history. Often the individual may report rapid loss of visual acuity causing distortion of vision, with straight lines and objects becoming wavy.17

It is extremely important that patients reporting these symptoms are referred urgently for a comprehensive assessment by an ophthalmologist. Prompt referral is a key element in preventing more extensive vision loss in the future.

Ms Heraghty said:

“It is essential that doctors are aware of the key risk factors for macular degeneration. Referral of these patients to an eye health professional is of vital importance in order to detect the condition early and to direct the course of patient management.”


Options for management 

After a diagnosis has been established, the specific type of treatment varies according to the type of macular degeneration present.

There are currently no treatments available to prevent the progression of dry macular degeneration, so management should focus on controlling all modifiable risk factors as tightly as possible. This includes strategies such as:10

  • Advise the patient to quit smoking;
  • Control blood pressure if elevated;
  • Adopt a healthy lifestyle, including a nutritious diet, optimal weight control and regular exercise;
  • Use a hat and sunglasses as an added precaution;
  • Consider the use of high dose anti-oxidants. These have been shown to reduce further vision loss in some cases of intermediate macular degeneration; and
  • Implement household modifications, including establishing visual aids in the home, improving lighting, and using magnifying glasses, reading telescopes and other visual enhancers.

The same basic measures and lifestyle changes should be prescribed in cases of wet macular degeneration. In addition, there are several medical agents that can be used to combat wet macular degeneration. Anti-vascular endothelial growth factor (VEGF) agents have been a particular success story in this field. These agents are proven to be effective in preventing vision loss and improving sight in some patients with macular degeneration.3,18 The monoclonal antibody ranibizumab (Lucentis) targets VEGF, thereby reducing the stimulus for choroidal neovascularisation.19 Lucentis has demonstrated effectiveness in preventing visual loss and in many cases resulted in improved vision.18,19 Other therapies such as laser therapy, macular translocation surgery and radiotherapy have all been used in the treatment of wet macular degeneration.17

For those with macular degeneration of diabetic origin, a thorough diabetic assessment is vital with optimal control of blood sugar levels and engagement with a multidisciplinary or diabetic specialist team. Additionally, focal macular laser photocoagulation, grid photocoagulation and intra-vitreal triamcinolone acetonide have all been used in the treatment of diabetic maculopathy.4

As the evidence base continues to develop and we learn more about macular degeneration, including its genetic origins, it is hoped that our management of this condition will continue to evolve and improve so that patient outcomes are optimised.

 

References:

  1. Age-related macular degeneration [online]. Moorfields Eye Hospital, National Health Service Foundation Trust; 24 November 2008 [cited 11 January 2010]. Available from URL: http://www.moorfields.nhs.uk/Eyehealth/Commoneyeconditions/Age-relatedmaculardegeneration
  2. Chiu CJ, Milton RC, Gensler G, Taylor A. Association between dietary glycemic index and age-related macular degeneration in nondiabetic participants in the Age-Related Eye Disease Study. Am J Clin Nutr. 2007; 86(1): 180-8.
  3. Guymer RH. Managing neovascular age-related macular degeneration:A step into the light. Med J Aust. 2007; 186(6): 276-7.
  4. Mendrinos E, Stangos AN, Pournaras CJ. Diabetic Retinopathy. BMJ Clin Evid [online]. 23 November 2007 [cited 11 January 2010]. Available from URL: http://www.bmj.com/cgi/content/full/326/7397/1023
  5. Taylor HR, Keeffe JE, Vu HT, Wang JJ, Rochtchina E, Pezzullo ML, et al. Vision loss in Australia. Med J Aust. 2005; 182(11): 565-8.
  6. VanNewkirk MR, Nanjan MB, Wang JJ, Mitchell P, Taylor HR, McCarty CA. The prevalence of age-related maculopathy: The visual impairment project. Ophthalmology. 2000; 107(8): 1593-600.
  7. Smith W, Assink J, Klein R, Mitchell P, Klaver CC, Klein BE, et al. Risk factors for age-related macular degeneration: Pooled findings from three continents. Ophthalmology. 2001; 108(4): 697-704.
  8. Thornton J, Edwards R, Mitchell P, Harrison RA, Buchan I, Kelly SP. Smoking and age-related macular degeneration: A review of association. Eye (Lond). 2005; 19(9): 935-44.
  9. Knudtson MD, Klein R, Klein BE. Physical activity and the 15-year cumulative incidence of age-related macular degeneration: the Beaver Dam Eye Study. Br J Ophthalmol. 2006; 90(12): 1461-3.
  10. Morris B, Imrie F, Armbrecht AM, Dhillon B. Age-related macular degeneration and recent developments: New hope for old eyes? Postgrad Med J. 2007; 83(979): 301-7.
  11. Klein BE, Klein R, Lee KE, Moore EL, Danforth L. Risk of incident age-related eye diseases in people with an affected sibling : The Beaver Dam Eye Study. Am J Epidemiol. 2001; 154(3): 207-11.
  12. Smith W, Mitchell P. Family history and age-related maculopathy: The Blue Mountains Eye Study. Aust NZ J Ophthalmol. 1998; 26(3): 203-6.
  13. Klein R, Klein BE, Wong TY, Tomany SC, Cruickshanks KJ. The association of cataract and cataract surgery with the long-term incidence of age-related maculopathy: The Beaver Dam eye study. Arch Ophthalmol. 2002; 120(11): 1551-8.
  14. Dong LM, Stark WJ, Jefferys JL, Al-Hazzaa S, Bressler SB, Solomon SD, et al. Progression of age-related macular degeneration after cataract surgery. Arch Ophthalmol. 2009; 127(11): 1412-9.
  15. Hogg RE, Woodside JV, Gilchrist SE, et al. Cardiovascular disease and hypertension are strong risk factors for choroidal neovascularization. Ophthalmology 2008; 115: 1046-52.
  16. Coleman HR, Chan C-C, Ferris FL et al. Age-related macular degeneration. Lancet 2008;377:1835-45
  17. Khaw PT, Shah P, Elkington R. ABC of Eyes. 4th ed. London: BMJ Publishing Group Ltd; 2004
  18. Mitchell P, Korobelnik JF, Lanzetta P, Holz FG, Pruente C, Schmidt-Erfurth UM, et al. Ranibizumab (Lucentis) in neovascular age-related macular degeneration: Evidence from clinical trials. Br J Ophthalmol. 2010; 94: 2-13.
  19. Rosenfeld PJ, Brown DM, Heier JS, Boyer DS, Kaiser PK, Chung CY, et al. Ranibizumab for neovascular age-related macular degeneration. N Engl J Med. 2006; 355(14): 1419-31.
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Dates

Posted On: 10 May, 2010
Modified On: 30 May, 2017


Created by: myVMC