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Age-related macular degeneration

Last updated: November 4, 2020

Summary

Age-related macular degeneration (AMD) is a degenerative disease of the retina and represents the most common cause of blindness in individuals > 65 years in developed countries. It is classified into two major forms: dry AMD and wet AMD. Dry AMD is caused by deposition of various metabolites under the retinal pigment epithelium (drusen) and usually develops over decades, while wet AMD is caused by neovascularizations growing into the subretinal space and manifests within weeks to months or even acutely. Both forms ultimately cause impaired central vision and can, in rare cases, lead to complete blindness. Patient history and clinical tools such as the Amsler grid can provide clues regarding visual impairment. Fundoscopy is needed to identify specific pathological changes. Fluorescein angiography may be used to confirm the diagnosis of wet AMD. Treatment focuses on slowing vision loss and/or improving vision.

Epidemiology

AMD is the leading cause of blindness in individuals > 65 years in developed countries.

  • Age of onset: usually > 55 years
  • Prevalence: increasing from 0.2 % (ages 55 to 64) to 13.1 % (≥ 84 years)
  • Sex: >
  • Ethnicity: more prevalent in whites

References:[1][2]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

References:[2]

Pathophysiology

AMD is characterized by progressive degenerative changes in the central part of the retina (macula) → visual impairment.

References:[2][3][4][5]

Clinical features

  • Painless central or pericentral visual impairment → reduced visual acuity, difficulty adapting to changes in lighting
    • Dry AMD: slow progressive visual impairment (usually over decades) and unilateral or bilateral onset
    • Wet AMD: acute or insidious onset (over weeks to months) and usually manifests in one eye first
  • Metamorphopsia; : type of visual distortion in which straight lines appear wavy, which can be tested for using an Amsler grid
  • Scotoma (blind spot)

References:[2][4][5][6]

Diagnostics

Dry AMD Wet AMD

References:[2][4][5][6][7]

Differential diagnoses

Differential diagnosis of vision loss
Condition Clinical features Fundoscopy
AMD
  • May be insidious (dry AMD) or rapid (wet AMD) onset
  • Impairment of central vision only (vision loss is rare)
Open-angle glaucoma
  • Insidious onset
  • Peripheral vision loss (tunnel vision)
Central vessel occlusion (retinal artery)
  • Acute or subacute onset
  • Complete vision loss
Retinal detachment
  • Acute onset
  • Partial or complete vision loss (falling curtain)
Cataract
  • Insidious onset
  • Blurred, dim vision, and a glare
  • Absent or opacified red-reflex
  • Retina may not be visible (in advanced disease)

The differential diagnoses listed here are not exhaustive.

Treatment

  • No causal treatment available
  • Supportive treatment
    • Patient education
    • Visual and reading aids: magnifying glass
    • Avoid risk factors (e.g., smoking)
    • Improve diet (i.e., high in green leafy vegetables and fish)
    • Antioxidants therapy: vitamins A, C, and E, beta-carotene, zinc
  • Treatment of wet AMD
    • First-line: injection of VEGF inhibitors (ranibizumab, bevacizumab, pegaptanib) into the vitreous body
    • Second-line: when VEGF is contraindicated
      • Laser coagulation: direct thermal coagulation of neovascularization
      • Photodynamic therapy: intravenously administered dye is activated in the eye by laser light → local toxic effect → thrombosis of subretinal neovascularizations

References:[8][9]

Prognosis

  • Chronic progressive course for both types
  • Prognosis for dry AMD is significantly better than for wet AMD
  • Complete loss of central vision is possible but rare

References:[1]

References

  1. Agabegi SS, Agabegi ED. Step-Up To Medicine. Wolters Kluwer Health ; 2015
  2. Arroyo JG, Trobe J, Schmader KE, Libman H. Age-Related Macular Degeneration: Clinical Presentation, Etiology, and Diagnosis. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/age-related-macular-degeneration-clinical-presentation-etiology-and-diagnosis.Last updated: August 18, 2016. Accessed: May 17, 2017.
  3. Le T, Bhushan V. First Aid for the USMLE Step 1 2015. McGraw-Hill Education ; 2014
  4. Maturi RK, Dahl AA. Nonexudative (Dry) Age-Related Macular Degeneration (AMD). Nonexudative (Dry) Age-Related Macular Degeneration (AMD). New York, NY: WebMD. http://emedicine.medscape.com/article/1223154. Updated: March 16, 2017. Accessed: May 17, 2017.
  5. Age-Related Macular Degeneration (AMD or ARMD). https://www.merckmanuals.com/professional/eye-disorders/retinal-disorders/age-related-macular-degeneration-amd-or-armd. Updated: January 1, 2017. Accessed: May 17, 2017.
  6. Prall FR, Dahl AA. Exudative (Wet) Age-Related Macular Degeneration (AMD). Exudative (Wet) Age-Related Macular Degeneration (AMD). New York, NY: WebMD. http://emedicine.medscape.com/article/1226030. Updated: February 28, 2017. Accessed: May 17, 2017.
  7. O'Toole L. Fluorescein and ICG angiograms : still a gold standard.. Acta Ophthalmologica Scandinavica. 2007; 85 (240). doi: 10.1111/j.1600-0420.2007.01063_2988.x . | Open in Read by QxMD
  8. Le T, Bhushan V, Chen V, King M. First Aid for the USMLE Step 2 CK. McGraw-Hill Education ; 2015
  9. Arroyo JG, Trobe J, Schmader KE, Libman H. Age-Related Macular Degeneration: Treatment and Prevention. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/age-related-macular-degeneration-treatment-and-prevention.Last updated: March 8, 2017. Accessed: May 17, 2017.