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| Age-related
macular degeneration is a gradual, often bilateral, degeneration caused by
aging and possibly involving vascular disease in the choriocapillaris and
RPE degeneration with secondary retinal changes.
There are two morphologic types: non-disciform and disciform.
Non-disciform (dry type) is usually a slow, bilateral visual loss
in elderly associated with degeneration of the RPE and obliteration of the
underlying choriocapillaris. Clinically, drusen are commonly seen in the macula and appear
as small, whitish-yellow, round lesions composed largely of
mucopolysaccharide representing secretory and degenerative products of the
RPE and its basement membrane (Bruch's membrane)(#22059).
These reveal hyperflorescence with angiography because of the
atrophy of the overlying RPE. A
small percentage may evolve into a disciform degeneration with serous and
hemorrhagic detachment. Histologically,
this entity is characteristized by degeneration and hypopigmentation of
the RPE. Drusen appear as
eosinophilic, PAS positive, hyalin bulbous thickening on Bruch's
membrane(#22060). In early
stages, the overlying RPE appears normal; however, the RPE becomes more
flattened, atrophic, depigmented, or may migrate in later stages.
Drusen may also calcify. Bruch's
membrane may also show signs of diffuse thickening.
In long-standing cases, a secondary cystoid degeneration, schisis,
or overlying retinal holes may develop.
RETINA--AGE-RELATED
(SENILE) MACULAR DEGENERATION (SMD) Disciform (wet type) is a senile
process associated with sub-RPE neovascularization similar to that which
occurs in several other disorders of the RPE, sensory retina, and choroid,
and from trauma. Classically
it begins after age 60 and is often bilateral.
Patients often have antecedent non-disciform degenerative changes.
Clinically the patient may notice acute metamorphosis or loss of
vision and may present suddenly with hemorrhagic detachment from
neovascularization which extends from the choroid through Bruch's membrane
into the sub-RPE space. They
may also get exudative detachments. If hemorrhage develops, it appears as a discretely elevated
subretinal mound(#22052,#22063). This
eventually leads to rod and cone degeneration, intraretinal exudation with
circinate deposition of lipids, CME, and/or macular hole.
The blood may organize leaving a yellow-gray discoloration admixed
with hemosiderin. The RPE may
undergo hyperplasia and fibrous metaplasia leading to a thick, fibrous
subretinal disciform scar.
For an
additional view of disciform type SMD, see (#22772).
Additional
views of drusen: (#22832, #22835, #22838, #22844, #22847)
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| Clinical
#22059 |
Clinical
#22062 |
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| Gross
#22063 |
High
Power #22060 |
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| Med.
Power #22064 |
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