age-related%20macular%20degeneration
AGE-RELATED MACULAR DEGENERATION
Age-related macular degeneration is a common, chronic, progressive, degenerative disease that causes central loss of vision due to abnormalities that occurs in the pigment, neural and vascular layers of the macula.
The macular disorder may have one or more of the following:
- Formation of drusen which are localized deposits of extracellular material usually concentrated in the macula
- Abnormalities in the retinal pigment epithelium (eg hypopigmentation or hyperpigmentation)
- Retinal pigment epithelium and choriocapillaris geographic atrophy
- Neovascular (exudative) maculopathy
Decreased central vision and distortion of seeing straight lines are the most common symptoms.

Classification

Classification of Age-Related Macular Degeneration (AMD) by Age-Related Eye Disease Study (AREDS)1

  • Used in predicting the risk of progression from early to late AMD and visual loss

No Age-Related Macular Degeneration (AREDS category 1)

  • No drusen or presence of few small drusen (<63 microns in diameter)

Early Age-Related Macular Degeneration (AREDS category 2)

  • Presence of any or all of the following:
    • Multiple small drusen
    • Few intermediate drusen (63-124 microns in diameter) or
    • Abnormalities in the retinal pigment epithelium (RPE)

Intermediate Age-Related Macular Degeneration (AREDS category 3)

  • Presence of any or all of the following:
    • Extensive intermediate drusen
    • At least one large drusen (≥125 microns in diameter) or
    • Geographic atrophy not involving the center of the fovea

Advanced Age-Related Macular Degeneration (AREDS category 4)

  • Geographic atrophy that involves the center of the fovea and/or any of the manifestations of neovascular AMD

Neovascular Age-Related Macular Degeneration (AMD) Classification by Location Seen in Fundus Fluorescein Angiography (FFA)2

  • Helps in identifying specific treatment to give the patient

Extrafoveal

  • Lesion located ≥200 micrometers from the geometric center of the fovea

Juxtafoveal

  • Lesion located between 1 and 199 micrometers from the geometric center of the fovea

Subfoveal

  • Lesion located under the center of the foveal avascular zone

Neovascular Age-Related Macular Degeneration Classification by Angiographic Patterns of Fluorescence2

  • Helps in identifying specific treatment to give the patient

Classic Choroidal Neovascularization (CNV)

  • Bright, well-demarcated, uniform hyperfluorescence in the early phase of FFA and then at the late phase of the angiogram it shows leakage that obscures the boundaries

Occult Choroidal Neovascularization (CNV)

  • Characterized by either:
    • An area of irregular elevation the RPE (fibrovascular pigment epithelial detachment) that appears as stippled hyperfluorescence present in the midphase of the angiogram or
    • Leakage from an undetermined source that appears as speckled hyperfluorescence within dye pooled in the subretinal space

1Modified from: American Academy of Ophthalmology Retina Panel. Preferred practice pattern guidelines. Age-related macular degeneration. San Francisco, CA: American Academy of Ophthalmology; 2008.

2Modified from: The Royal College of Ophthalmologists. Age-related macular degeneration guidelines for management. Feb 2009.

Assessment

Non-Neovascular/Non-Exudative/Early/Dry Age-Related Macular Degeneration (AMD)

  • Clinical presentation:
    • Soft drusen ≥63 microns in diameter that causes areas of hyperpigmentation in the outer retina or choroid
    • Areas of hypopigmentation of the retinal pigment epithelium (RPE) as a result of gradual breakdown of the RPE
    • Photoreceptors has loss of function
  • Usually of ischemic cause

Neovascular/Exudative/Late/Wet Age-Related Macular Degeneration (AMD)

  • Clinical presentation:
    • Presence of choroidal neovascularization (CNV) which is the perforation of the choriocapillaris vessels and growth through the Bruch’s membrane and entry to the subretinal pigment epithelial and/or subretinal spaces
    • Serous and/or hemorrhagic detachment of the sensory retina or RPE
    • Presence of hard exudates in the retina
    • Fibrovascular proliferation in the subretina and sub-RPE
    • Presence of disciform scar
  • Usually due to leakage of fluid from blood vessels

History

  • Ocular history especially presence of precursor lesions
  • Family history especially age-related macular degeneration (AMD)
  • Medical history including any hypersensitivity reactions
  • Social history especially smoking
  • Medications and nutritional supplements

Physical Examination

Ocular Evaluation

  • Dilated eye exam using binocular slit-lamp biomicroscopy reveals any of the following:
    • Presence of drusens that appears as bright yellow spots or pale yellow spots
    • Presence of geographic atrophy that appears as sharply demarcated or defined and scalloped edges of partial or complete depigmentation as a result of retinal pigment epithelium (RPE) atrophy
    • Lesions indicating risk for progression to advanced age-related macular degeneration (AMD) (eg large drusen, soft indistinct drusen, extensive drusen area, hyperpigmentation)
    • Signs of exudative AMD like subretinal or sub-RPE neovascularization that appears as gray green lesions, serous detachment of the neurosensory retina, RPE detachment, hemorrhages in the subretinal pigment epithelium, subretina, intraretina or preretina and breakthrough bleeding into the vitreous may occur, hard exudates within the macular area, epiretinal, intraretinal, subretinal or sub-pigment epithelial scar/glial tissue or fibrin like deposits, retinal angiomatous proliferations and retinochoroidal anatomists

Imaging

Fundus Fluorescein Angiography (FFA)

  • Gold standard for diagnosing choroidal neovascularization (CNV) in age-related macular degeneration (AMD) as it confirms the presence of CNV and its extent, type, size and location
  • Detects persistent or recurrent CNV following treatment
  • Recommended to perform when the patient complains of new metamorphopsia with blurring of vision
  • Used to guide treatment using verteporfin photodynamic therapy (PDT) or laser photocoagulation surgery

Fundus Photography

  • Once angiography is done, color fundus photography can be done to:
    • Locate the pathology of the different tissue layers
    • Evaluate sensory retina serous detachments
    • Identify the cause of blocked fluorescence
  • Stereoscopic color photographs records the appearance of the macular retina that can be used as baseline in patients with advanced non-neovascular AMD and in follow-up of patients that has been treated

Indocyanine Green (ICG) Angiography

  • The alternative dye, indocyanine green, is used to delineate choroidal vessel morphology and circulation
    • Penetrates hemorrhage and retinal pigment epithelium (RPE) better than FFA

Optical Coherence Tomography (OCT)

  • Provides cross-sectional view of the retina that can identify soft drusen, RPE detachments, subretinal and intraretinal fluid, CNV, cystoid macular edema, as well as the integrity of the photoreceptor and RPE layers
  • Helps to distinguish causes of visual loss that are not directly associated with AMD (eg subtle epiretinal membrane or vitreomacular traction)
  • Allows evaluation of the RPE and photoreceptor layer to identify the anatomic causes of metamorphopsia and visual acuity loss
  • Helps determines the presence of subretinal fluid and degree of retinal thickening which are the earliest manifestations of neovascularization
  • Accurately follows the structural changes that can be used in evaluating the retina and RPE response to therapy
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