Porth's Essentials of Pathophysiology, 4e - page 984

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Nervous System
perceives a shadow or dark curtain progressing across
the visual field. Large peripheral detachments may occur
without involvement of the macula, so that visual acuity
remains unaffected.
Diagnosis and Treatment.
Diagnosis of retinal
detachment is based on a history of visual distur-
bances (e.g., presence of floaters, luminous rays, or
light flashes) and the ophthalmoscopic appearance of
the retina. The direct (handheld) ophthalmoscope is
useful in detecting an altered red reflex sometimes
associated with retinal detachment. However, because
the view is narrow, a negative examination with direct
ophthalmoscopy cannot exclude the diagnosis of retinal
detachment. Ophthalmologists and optometrists use
indirect examination techniques that greatly enhance
visualization of the peripheral retina.
30
Because there is a variable interval between a retinal
break and retinal detachment, treatment methods focus
on early detection and prevention of further vitreous
detachment and retinal tear formation. Symptomatic
retinal breaks are usually treated with laser or
cryotherapy to seal the retinal tears so that the vitreous
humor can no longer leak into the subretinal space.
30
The primary treatment of traction retinal detachment is
vitreoretinal surgery.
23,30
Macular Degeneration
Macular degeneration is characterized by degenera-
tive changes in the central portion of the retina (the
macula) that result primarily in loss of central vision
(see Figure 38-1B). Age-related macular degeneration
(AMD) is the most common cause of reduced vision in
the elderly.
23,25,31–33
The causes are poorly understood.
In addition to older age, identifiable risk factors include
cigarette smoking, obesity, and low dietary intake of
lutein, omega 3 fatty acids, zinc, and vitamins A, C, and
E.
32
Increasing evidence suggests that genetic factors may
also play a role.
Age-related macular degeneration is commonly
classified simply as “early” or “late.” Late AMD is
further subdivided into geographic atrophy (“dry”)
and neovascular (“wet”). Although both late forms
are progressive and usually bilateral, they differ in
manifestations, prognosis, and management.
Geographic Atrophic Degeneration.
Geographic
atrophic degeneration is characterized by gradually
progressive visual loss of moderate severity due to
atrophy and degeneration of the outer retina and retinal
pigment epithelium. Because it does not involve leakage
of blood or serum, it is commonly referred to as dry
macular degeneration. The level of associated visual
impairment is variable and may be minimal, and the
atrophic changes may stabilize or progress slowly (Fig.
38-10A). However, people with this form of AMD need
to be followed closely because the neovascular form may
FIGURE 38-10.
Funduscopic view of age-related macular degeneration (AMD).
(A)
Intermediate AMD
with pale yellow spots or drusen scattered throughout the retina.
(B)
Advanced AMD with formation
of scar tissue representing death of the underlying retinal tissue and loss of all visual function in the
corresponding macular area. (Courtesy of the National Eye Institute, National Institutes of Health.)
A
B
FIGURE 38-9.
Ophthalmoscopic view of retinal detachment
(arrows, wrinkles in detached retina). (From Moore KL,
Daley AF, Agur AMR. Clinically Oriented Anatomy. 6th ed.
Philadelphia, PA: Wolters Kluwer Health | Lippincott Williams &
Wilkins; 2010:910).
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