Porth's Essentials of Pathophysiology, 4e

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Nervous System

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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

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 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).

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