AGE-RELATED MACULAR DEGENERATION

Age-related macular degeneration (ARMD) is an acquired degeneration of the retina that causes significant central visual impairment through a combination of non-neovascular (drusen and retinal pigment epithelium abnormalities), and neovascular derangement (choroidal neovascular membrane formation). Advanced disease may involve focal areas of retinal pigment epithelium (RPE) loss, subretinal or sub-RPE hemorrhage or serous fluid, as well as subretinal fibrosis.

CAUSES

Eat a diet high in saturated fat (found in foods like meat, butter, and cheese)

KEY TERMS

  • Age-related Macular degeneration (ARMD)
  • Nonexudative, dry, or nonneovascular ARMD (synonyms)
  • Exudative, wet, or neovascular ARMD (synonyms)
  • Geographic atrophy
  • Choroidal neovascularization and choroidal neovascular membranes

Early ARMD: Defined by the presence of numerous small (<63 microns, “hard”) or intermediate (≥63 microns but <125 microns, “soft”) drusen

Dry AMD is when parts of the macula get thinner with age and tiny clumps of protein called drusen grow. You slowly lose central vision. In dry age-related macular degeneration, small white or yellowish deposits, called drusen, form on the retina, beneath the macula, causing it to deteriorate or degenerate over time.

Wet ARMD age-related macular degeneration, abnormal blood vessels under the retina begin to grow toward the macula. Because these new blood vessels are abnormal, they tend to break, bleed, and leak fluid, damaging the macula and causing it to lift up and pull away from its base.

SIGNS

  • Drusen
  • Geographic atrophy
  • Subretinal fibrosis
  • RPE changes
  • Subretinal fluid or hemorrhage/hard exudate

SYMPTOMS

  • Decreased visual acuity, insidious or sudden-onset
    • Dry ARMD constitutes 85-90% cases of ARMD, and usually does not cause severe vision loss.
    • Wet AMD constiutes 10-15% of ARMD cases and is the major cause of severe vision loss.
  • Blurred vision
  • Distorted near vision
  • Scotoma
  • Visual distortion, metamorphopsia, micropsia
  • Vague visual complaints

DRUSEN

Drusen are a hallmark of ARMD. On histopathology, nodular drusen appear as eosinophilic dome-shaped structures situated between Bruch’s membrane and the displaced, attenuated RPE overlying the drusen.

Serous detachments of the RPE

On histopathology, serous RPE detachments can be associated with thickening of the inner aspect of Bruch’s membrane.[36]

RPE atrophy

Histopathologically, RPE atrophy may be associated with depigmentation, migration and proliferation of RPE cells into the photoreceptor layer. With progression, RPE degeneration is seen, with loss of adjacent photoreceptors, and juxtaposition of Bruch’s membrane to the inner nuclear layer.

Subretinal or sub-RPE neovascularisation

Sub-RPE neovascularization is located within Bruch’s membrane, typically between the thickened inner aspect of Bruch’s membrane and the rest of Bruch’s membrane. A sub-RPE neovascular membrane can extend subretinally in areas where Bruch’s membrane is not intact. With discontinuities in Bruch’s membrane, capillary-like choroidal vessels can form a subretinal RPE vascular web that can affect serous or hemorrhagic detachments of the neurosensory retina.

DISCIFORM SCARS OR LESIONS

Fibrous disciform scars are usually results of sub-RPE neovascularization. Fibrous tissue develops within Bruch’s membrane or between the RPE and retina

COMPLICATIONS

Subretinalhemorrhage

Subretinalhemorrhage can cause photoreceptor damage as the blood is in contact with the photoreceptors and early treatment is needed. Subretinalhemorrhage may be of varying severity. Massive subretinalhemorrhages are typically thought to be associated with anticoagulation therapy, specifically, warfarin therapy. Surgical management options has been reviewed elsewhere (Management of SubmacularHemorrhage).

Vitreous hemorrhage

Break-through vitreous hemorrhage secondary to neovascular ARMD is a rare complication. Sudden peripheral visual field and central vision loss is noted in these instances, to be distinguished from the central field complaints typically noted with ARMD. Other etiologies, such as retinal tears from hemorrhagic posterior vitreous detachments, retinal vascular diseases such as diabetic retinopathy or vein occlusions should be considered as well.

DIPLOPIA

Diplopia can occur as a result of the choroidal neovascular membrane “dragging” the fovea.

Physical examination

  • Periodic dilated fundus exams are warranted to identify patients who progress to neovascular ARMD without having symptoms.
  • Amsler grid
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