Figure 4-13 Fuchs heterochromic iridocyclitis. Fine vessels (arrows) are seen crossing the trabecular meshwork. This neovascularization is not accompanied by a fibrovascular membrane and does not result in peripheral anterior synechiae formation and secondary angle closure. (Courtesy of Steven T. Simmons, MD.)
The IOP does not correspond to the degree of inflammation and may be difficult to control. Corticosteroids are generally not effective in treating this condition and could potentially cause a steroid-induced IOP elevation. Medical therapy starts with aqueous suppressants, which are often effective in controlling IOP. Recent evidence suggests that rubella virus infection may be the underlying cause of this condition.
Birnbaum AD, Tessler HH, Schultz KL, et al. Epidemiologic relationship between Fuchs heterochromic iridocyclitis and the United States rubella vaccination program. Am J Ophthalmol. 2007;144(3):424–428.
Elevated Episcleral Venous Pressure
Episcleral venous pressure is an important factor in the regulation of IOP. Normal episcleral venous pressure is 8–10 mm Hg, but it can be raised by a variety of clinical entities that either obstruct venous outflow or involve arteriovenous malformations. A list of entities that increase episcleral venous pressure is presented in Table 4-3.
Table 4-3
Patients may note a chronic red eye without discomfort or allergic symptoms. Occasionally, a distant history of significant head trauma may suggest the cause of a carotid cavernous sinus or dural fistula. However, most cases are idiopathic, often without angiographic abnormalities, and may be
familial. Clinically, patients with elevated episcleral venous pressure present with tortuous, dilated episcleral veins (Fig 4-14). These vascular abnormalities may be unilateral or bilateral. Gonioscopy often discloses blood in the Schlemm canal (see Chapter 3, Fig 3-17C). In rare instances, signs of ocular ischemia or venous stasis may be present. Sudden, severe carotid-cavernous fistulas may be accompanied by proptosis and other orbital or neurological signs. These cases may require neuroradiologic intervention.
Figure 4-14 Prominent episcleral vessels are seen in a patient with idiopathic elevated episcleral venous pressure. (Courtesy of
Keith Barton, MD.)
Prostaglandin analogues and medications that reduce aqueous humor formation may be effective in some patients. Laser trabeculoplasty is not effective. Glaucoma filtering surgery may be complicated by ciliochoroidal effusion or suprachoroidal hemorrhage.
Accidental and Surgical Trauma
Nonpenetrating, or blunt, trauma to the eye causes a variety of anterior segment injuries:
hyphema angle recession iridodialysis
iris sphincter tear cyclodialysis lens subluxation
A combination of posttraumatic inflammation, presence of blood, and direct injury to the trabecular meshwork often results in elevated IOP initially after trauma. This elevation tends to be short in duration but may be protracted, with the risk of corneal blood staining (Fig 4-15) and glaucomatous optic nerve damage.
Figure 4-15 Corneal blood staining following trauma. (Courtesy of Steven T. Simmons, MD.)
OAG is one of the long-term sequelae of siderosis or chalcosis from a retained intraocular metallic foreign body in penetrating or perforating injuries. Chemical injuries, particularly alkali, may cause acute secondary glaucoma as a result of inflammation, shrinkage of scleral collagen, release of chemical mediators such as prostaglandins, direct damage to the chamber angle, or compromise of the anterior uveal circulation. Trabecular damage or inflammation may cause glaucoma to develop months or years after a chemical injury.
Hyphema
Elevated IOP may result from hyphema through several mechanisms (Fig 4-16). Increased IOP is more common following recurrent hemorrhage or rebleeding following a traumatic hyphema. The reported frequency of rebleeding following hyphema varies considerably in the literature, probably because of differences in study populations, with an average incidence of 5%–10%. Rebleeding usually occurs within 3–7 days of the initial hyphema and may be related to normal clot retraction and lysis. In general, the larger the hyphema, the higher the incidence of increased IOP, although small hemorrhages may also be associated with marked elevation of IOP, especially in the already compromised angle. Increased IOP is a result of obstruction of the trabecular meshwork with red blood cells (RBCs), inflammatory cells, debris, and fibrin, and of direct injury to the trabecular meshwork from the blunt trauma.
Figure 4-16 A small hyphema seen gonioscopically in the inferior chamber angle, with layering of blood on the trabecular
meshwork. (Courtesy of Steven T. Simmons, MD.)
Individuals with sickle cell hemoglobinopathies have an increased incidence of elevated IOP following hyphema and are more susceptible to the development of optic neuropathy. Normal RBCs generally pass through the trabecular meshwork without difficulty. However, in the sickle cell hemoglobinopathies (including sickle trait), the RBCs tend to sickle in the anterior chamber, because of the low pH of aqueous humor. These more rigid cells tend to become trapped in the trabecular meshwork. Even small amounts of blood in the anterior chamber may therefore result in marked elevations of IOP. In addition, the optic nerves of patients with sickle cell disease are much more sensitive to elevated IOP and are prone to developing anterior ischemic optic neuropathy and central retinal artery occlusion, as a result of compromised microvascular perfusion.
In general, the patient with an uncomplicated hyphema should be managed conservatively, with an eye shield, limited activity, and head elevation. Topical and systemic corticosteroids may reduce associated inflammation, although their effect on rebleeding is debatable. If significant ciliary spasm or photophobia occurs, cycloplegic agents may be helpful, but they have no proven benefit for prevention of rebleeding. Systemic administration of aminocaproic acid has been shown to reduce rebleeding in some studies. However, this has not been confirmed in all studies, and systemic adverse effects, such as hypotension, syncope, abdominal pain, and nausea, can be significant. Also, discontinuation of aminocaproic acid may be associated with clot lysis and with additional IOP elevation. Patching and bed rest are advocated by some authors, although these precautions are of unproven value.
If the IOP is elevated, aqueous suppressants and hyperosmotic agents are recommended. It has been suggested that patients with sickle cell hemoglobinopathies avoid carbonic anhydrase inhibitors, because these agents may increase the sickling tendency in the anterior chamber by further lowering the pH; however, this relationship has not been firmly established. Physicians should be aware of the potential of systemic carbonic anhydrase inhibitors and hyperosmotic agents to induce sickle crises in susceptible individuals who are significantly dehydrated. Both classes of drugs may enhance sickling, as each may exacerbate dehydration. Adrenergic agonists with significant α1-agonist effects (apraclonidine, dipivefrin, epinephrine) should also be avoided in sickle cell disease because of concerns regarding anterior segment vasoconstriction. Parasympathomimetic agents should be avoided in all patients with hyphemas.
Clinicians should have a lower threshold for surgical intervention in sickle cell patients, given the
increased risk of optic atrophy from elevated IOP. If the hyphema or corneal staining significantly obstructs vision, the possibility of amblyopia may justify early surgical intervention in very young children. If surgery for elevated IOP becomes necessary, an anterior chamber irrigation or washout procedure is commonly performed first. If a total hyphema is present, pupillary block may occur, and an iridectomy is helpful at the time of the washout. If the IOP remains uncontrolled, incisional glaucoma surgery may be required. Some surgeons prefer to perform incisional glaucoma surgery as the initial surgical procedure with the anterior chamber washout in order to obtain immediate control of IOP and relief of any pupillary block.
Campagna JA. Traumatic hyphema: current strategies. Focal Points: Clinical Modules for Ophthalmologists. San Francisco: American Academy of Ophthalmology; 2007, module 10.
Hemolytic and ghost cell glaucoma
Hemolytic and/or ghost cell glaucoma may develop after a vitreous hemorrhage. In hemolytic glaucoma, hemoglobin-laden macrophages block the trabecular outflow channels. Red-tinged cells are seen floating in the anterior chamber, and a reddish brown discoloration of the trabecular meshwork is often present.
Ghost cell glaucoma is a secondary OAG caused by degenerated RBCs (ghost cells) blocking the trabecular meshwork. Ghost cells are RBCs that have lost their intracellular hemoglobin and appear as small, khaki-colored cells. They are less pliable than normal RBCs (Fig 4-17); thus, they obstruct the trabecular meshwork, causing IOP elevation. RBCs degenerate within 1–3 months of a vitreous hemorrhage. They gain access to the anterior chamber through a disrupted hyaloid face, which can occur from previous surgery (pars plana vitrectomy, cataract extraction, or capsulotomy), from trauma, or spontaneously.
Figure 4-17 Ghost cell glaucoma: the classic appearance of ghost cells in the anterior chamber. These khaki-colored cells are small and can become layered, as is seen in a hyphema and hypopyon. (Courtesy of Ron Gross, MD.)
Clinically, patients present with elevated IOP and a history of vitreous hemorrhage resulting from trauma, surgery, or preexisting retinal disease. The IOP may be markedly elevated, causing corneal edema. The anterior chamber is filled with small, circulating, tan-colored cells (see Fig 4-17). The cellular reaction appears out of proportion to the aqueous flare, and the conjunctiva tends not to be inflamed unless the IOP is markedly elevated. On gonioscopy, the angle appears normal except for the layering of ghost cells over the trabecular meshwork inferiorly. A long-standing vitreous hemorrhage is present, with characteristic khaki coloration and clumps of extracellular pigmentation
from degenerated hemoglobin.
Both hemolytic and ghost cell glaucoma generally resolve once the hemorrhage has cleared. Medical therapy with aqueous suppressants is the preferred initial approach. If medical therapy fails to control the IOP, some patients may require irrigation of the anterior chamber, pars plana vitrectomy, and/or incisional glaucoma surgery. When a collection of RBCs or ghost cells is present in the vitreous, a pars plana vitrectomy is usually required for IOP control.
Traumatic, or angle-recession, glaucoma
Angle recession is due to a tear in the ciliary body, usually between the longitudinal and circular muscle fibers. Angle recession is often associated with injury to the trabecular meshwork as well. Angle-recession glaucoma is a chronic, typically unilateral, secondary OAG that may occur soon after ocular trauma or may develop months to years later. It resembles POAG in presentation and clinical course but can usually be distinguished by its classic gonioscopic findings (Figs 4-18, 4-19):
brown-colored, broad angle recess absent or torn iris processes white, glistening scleral spur
depression in the overlying trabecular meshwork PAS at the border of the recession
The degree of angle involvement is an important factor in determining whether a secondary glaucoma will develop. A significant proportion (up to 50%) of fellow eyes may develop elevated IOP, suggesting that many eyes with angle-recession glaucoma may have been predisposed to OAG.
Figure 4-18 Angle recession occurs when the ciliary body is torn, usually between the longitudinal and circular fibers of the ciliary body. There is a deepened angle recess as a result of a tear in the ciliary body (arrows). (Courtesy of Joseph Krug, MD.)
Figure 4-19 Typical angle appearance of an angle recession. Torn iris processes (arrows), a whitened and increasingly visible scleral spur, and a localized depression in the trabecular meshwork are seen.
Angle-recession glaucoma should be considered in a patient presenting with unilateral IOP elevation. The patient’s history may reveal the contributing incident; however, often this has been forgotten. Examination may show findings consistent with previous trauma, such as corneal scars, iris injury, changes in the angle as mentioned previously, focal anterior subcapsular cataracts, and phacodonesis. Comparing gonioscopic findings in the affected eye with those in the fellow eye may help the clinician identify areas of recession.
A greater extent of angle recession is associated with a greater risk of glaucoma. However, even with substantial angle recession, this risk is not high. Regardless, all eyes with angle recession must be observed because it is not possible to predict which eyes will develop glaucoma. Although the risk of developing glaucoma decreases appreciably after several years, it is still present even 25 years or more following injury. These eyes should continue to be examined annually.
The treatment of angle-recession glaucoma is often initiated with aqueous suppressants, prostaglandin analogues, and α2-adrenergic agonists. Miotics may be useful, but paradoxical responses with increased IOP may occur. Laser trabeculoplasty has a limited role and a reduced chance of success. Incisional glaucoma surgery may be required in order to control the IOP in patients not responding to medical therapy.
Surgical trauma
Surgical procedures such as cataract extraction, filtering surgery, and corneal transplantation may be followed by an increase in IOP. Similarly, laser surgery—including trabeculoplasty, iridotomy, and posterior capsulotomy—may be complicated by posttreatment IOP elevation. Although the IOP may rise as high as 50 mm Hg or more, these elevations are usually transient, lasting from a few hours to a few days. The exact mechanism is not always known. However, pigment release; presence of inflammatory cells, RBCs, and debris; mechanical deformation of the trabecular meshwork; and angle closure may all be implicated.
In addition, agents used as adjuncts to intraocular surgery may cause secondary IOP elevations. For example, the injection of viscoelastic substances such as sodium hyaluronate into the anterior chamber may result in a transient and possibly severe postoperative increase in IOP. Dispersive viscoelastics, especially in higher-molecular-weight forms, may be more likely to cause IOP increases than cohesive viscoelastic agents.
Such postoperative pressure elevation can cause considerable damage to the optic nerve of a susceptible individual, even in a short time. Eyes with preexisting glaucoma are at particular risk of further damage. Elevated IOP may increase the risk of retinal and optic nerve ischemia. It is therefore important to measure IOP soon after surgery or laser treatment. If a substantial rise in IOP does occur, therapy may be required. Usually, use of β-adrenergic antagonists, α2-adrenergic agonists, or carbonic anhydrase inhibitors is adequate. However, hyperosmotic agents, and even paracentesis, are sometimes necessary. Persistent elevation of IOP may require filtering surgery.
The implantation of an intraocular lens (IOL) can lead to a variety of secondary glaucomas:
uveitis-glaucoma-hyphema syndrome secondary pigmentary glaucoma pseudophakic pupillary block (see Chapter 5)
Uveitis-glaucoma-hyphema (UGH) syndrome is a form of secondary inflammatory glaucoma caused by chronic irritation that is usually the result of a malpositioned or rotating anterior chamber IOL. Characterized by chronic inflammation, cystoid macular edema, secondary iris neovascularization,