Functionally, melanin serves as a protection against UV radiation. The uvea (Fig. 373) is composed of the iris, ciliary body, and choroid. All three are contiguous and pigmented with melanocytes. Fig 373 Uvea. Source: Courtesy of Stephen McCormick. The iris is a diaphragm that changes the size of the pupil by the action of the sympathetic dilator muscle and the cholinergic constrictor muscle (Fig . 125). Brushfield spots are normally occurring small, white‐to‐brown elevations on the peripheral iris, more common in hazel or blue iris and in Down’s syndrome (Fig. 375). The ciliary body (Figs 374, 376, and 378) is made up of four clinically significant parts, as follows: Fig 374 The uvea is made up of the iris, ciliary body, and choroid. Source: Courtesy of Pfizer Pharmaceuticals. The choroid has the highest tissue blood flow and least oxygen extraction of any tissue in the body supplying 70% of the blood flow to the eye. Its purpose is to nourish the retina, which has one of the highest metabolic rates of any tissue in the body. Unlike the tree‐like branching of the retinal vessels, the choroidal circulation appears to crisscross in a tigroid‐like appearance (Fig. 378). It is most easily visualized in advanced dry age‐related macular degeneration (also called geographic AMD) after the retinal pigment layer disappears (Fig. 518) or in albinism where the retinal pigment is never fully developed (Fig. 540). The choriocapillaris may develop abnormal neovascularization in wet age‐related macular degeneration, pathologic myopia, and presumed histoplasmosis (Figs 519–521 and 524). Fig 375 Brushfield spots are lightly colored spots on the iris common to Down’s syndrome and light irides. Source: Courtesy of University of Iowa, Eyerounds.org. Fig 376 Ciliary body. Source: Courtesy of Pfizer Pharmaceuticals. Fig 377 Ciliary muscle contraction lessens tension on zonules causing the lens to become more convex which changes its focus from distance to near. Source: Courtesy of Pfizer Pharmaceuticals. Fig 378 Tigroid fundus with clearly visible, lightly pigmented choroidal vasculature. Source: Courtesy of Elliot Davidoff, MD. Fig 379 A flat benign choroidal nevus is present in 8% of Americans. Malignant transformation occurs in 1 in 9000/year. Six percent of metastatic tumors from elsewhere in the body go to the eye and the choroid is the most common ocular site. The primary site is most commonly the breast or lung. A melanocyte tumor is the most common primary intraocular malignancy. It is unilateral and develops from the choroid (Figs 379–384) in 85% of cases, the ciliary body in 9%, and the iris in 6% (Figs 313, 385, and 387). Ocular melanoma of the conjunctiva is the least common type (Figs 311 and 312). The risk may increase in fair‐skinned people, ages 50–70, and with excess exposure to sunlight and with melanosis of conjunctiva and skin (Fig. 313). Unlike a benign nevus (Fig. 379), which is usually a more uniform gray color and flat (Fig. 379), choroidal tumors are elevated and usually slate gray, but may be white to black with yellow‐gold and uneven pigmentation (Figs 380–384). This must be distinguished from metastatic carcinoma to the eye, which is also most common in the choroid, but is usually lighter in color. Primary and metastatic tumors of the eye are usually treated locally with external proton beam radiation or with a radioactive plaque brachytherapy (Fig. 381), both of which may preserve some vision. For larger tumors, the eye is sometimes removed by enucleation (Fig. 423). If the tumor extends beyond the globe and is life threatening, an exenteration of the orbit is required. This rarely performed surgery is disfiguring and destructive. It could necessitate removal of the orbital contents, the eyelids, orbital walls, and periorbital structures (Fig. 384). About 40% of uveal melanomas may metastasize. Metastatic tumors to the choroid, from elsewhere in the body, may be treated using laser photodynamic therapy with Verteporfin. It provides tumor control in 78% of eyes giving 20/40 or better vision in 66% of eyes. Fig 380 Elevated malignant choroidal melanoma. Note change in direction as artery rises over tumor (↑). Fig 381 Ruthenium radioactive plaque sewn or glued to the episclera of the eye is usually left in place for about 4 days and is used to treat smaller intraocular tumors. It is referred to as brachytherapy. Source: Courtesy of Dr Santosh G. Honor and Dr Surbhi Joshi, Prasad Eye Institute, Hyderabad, India. Fig 382 Gross section of malignant ↑ melanoma treated with removal of the eye (enucleation). Note retinal detachment ↑↑ and normally scalloped (serrated) junction of retina and pars plana ↑↑↑. The junction is, therefore, called the ora serrata. Source: Courtesy of University of Iowa, Eyerounds.com. Fig 383 B‐scan ultrasound of a malignant choroidal melanoma showing typical dome‐shaped growth which helps to confirm the diagnosis. The scan also shows its size and whether it extends beyond the sclera which will determine the type of treatment. This eye, with its massive tumor, was enucleated. Fig 384 Exenteration of the orbit for malignant melanoma extending beyond the sclera. Source: J.J. Ross et al., Br. J. Ophthalmol., 2010, Vol. 94, No. 5. Reproduced with permission of BMJ Publishing Group, Ltd. Fig 385 Benign iris freckle. Fig 386 Malignant iris melanoma with elevated lesions and distorted pupil. Patients with melanoma of the skin and elsewhere are often referred to eye physicians to rule out the eye as the primary site of origin of the tumor. Benign iris freckles (Fig. 385) and nevi are common, whereas malignant iris melanoma (Figs 386 and 387) is rare. Lesions become more suspicious if they are growing, elevated, vascularized, distort the pupil, or cause inflammation, glaucoma, or cataracts. Fig 387 Gonioscopic view of elevated iris melanoma. Source: Courtesy of Michael P. Kelly. Rubeosis iridis is a serious condition in which abnormal vessels grow on the surface of the iris (Figs 388 and 389) in response to ischemia associated with central retinal artery or vein occlusion, proliferative diabetic retinopathy, or carotid artery occlusive disease. Untreated, the neovascularization could cause end‐stage glaucoma, painful enough to require multiple glaucoma surgeries or rarely require removal of the eye (enucleation). Laser photocoagulation, or intravitreal anti‐VEGF (vascular endothelial growth factor) injections often cause regression of iris vessels. Fig 388 Rubeosis iridis with neovascularization. Fig 389 Rubeosis iridis. These abnormal iris blood vessels scar the angle of the eye. They most often result from ischemic retinal diseases such as proliferative diabetic retinopathy and central retinal artery or vein occlusion. An iris coloboma (Fig. 390) is due to failure of embryonic tissue to fuse inferiorly. It may also involve the choroid, lens, and optic nerve. Fig 390 Iris coloboma. Inflammations of the uvea are categorized by location: A, anterior (iritis); B, intermediate involving the ciliary body (cyclitis); C. posterior (choroiditis); and D, panuveitis, involving all uveal structures. There are many possible causes (Table 16, p. 148) and sometimes no etiology is found. Treatments vary depending on the cause, the severity and the chronicity. Most often the go‐to therapy includes corticosteroids but non‐steroidals (NSAIDS), antimetabolites and antibiotics (Table 14, p. 145) are sometimes needed. Macular edema is the most common cause for loss of vision, but cataracts, vitreous haze, and glaucoma are also common. Fig 391 Iritis. Fig 392 Slit‐beam view of flare and cells in anterior chamber. Category A, iritis, inflammation of the iris, accounts for 92% of cases of uveitis. It causes pain, tearing, and photophobia. Signs include miosis (small pupil), perilimbal conjunctival injection (Figs 391–396 and Table 13, p. 144), and anterior chamber flare and cells (Fig. 392). Flare refers to the beam’s milky appearance due to elevated protein. With the slit lamp on high magnification and a short, bright beam shone across the dark pupil, inflammatory cells are graded from trace to very many (4+). Fig 393 Keratic precipitates (Fig. 395) and posterior synechiae. Fig 394 Larger greasy yellowish keratic precipitates called mutton‐fat occur in sarcoidosis. Courtesy of University of Iowa, Eyerounds.org. Fig 395 Sites of conjunctival injection and pupil size in three cases of an inflamed eye due to three different causes (Figs 305, 363, and 393). Deposits of inflammatory cells and protein on the corneal endothelium (Figs 393, 394, and 395) are called keratic precipitates (or KPs) and are often a sign that is present for more than a few days. Iritis usually reduces eye pressure due to depressed secretion of aqueous and increased uveoscleral outflow. On the other hand the pressure could become elevated if the drainage from the eye is compromised by uveitic inflammatory cells obstructing the trabecular meshwork or from the side‐effect of the corticosteroid used to treat the iritis. Another complication of iritis is posterior synechiae. These are adhesions between the iris and the lens capsule (Fig. 393). To prevent this, steroids, such as generic topical prednisolone 1% (Pred Forte) or branded difluprednate (Durezol) are given to prevent a fibrinous sticky aqueous. Medrysone (HMS 1%), fluorometholone 0.25% (FML Forte), and loteprednol 0.5% (Lotimax) are three examples of steroids with less pressure‐elevating effects, but are less potent. Frequency and strength of medication depends on the severity of the condition (Table 14, p. 145). Table 13 Common causes of an injected conjunctiva (Fig. 395).
Chapter 8
Uvea
Malignant uveal tumors
Inflammation of the uvea (uveitis)
Iritis
Conjunctivitis
Acute glaucoma (Fig. 364)
Symptom
Pain, photophobia
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