Conditions Associated With a Pushing Mechanism
Tumors in the posterior segment of the eye or anterior uveal cysts may cause unilateral secondary angle closure. Primary choroidal melanomas, ocular metastases, and retinoblastoma are the tumors most commonly responsible. The mechanism of the angle closure is determined by the size, location, and pathology of the tumor. For example, choroidal and retinal tumors tend to shift the lens–iris interface forward as the tumors enlarge, whereas breakdown of the blood–aqueous barrier and inflammation from tissue necrosis can result in posterior synechiae and PAS formation, further exacerbating other underlying mechanisms of angle closure.
Ocular tumors can also cause anterior segment neovascularization leading to angle closure (see the section “Neovascular glaucoma”).
Malignant glaucoma (also called aqueous misdirection or ciliary block glaucoma) is a rare but potentially devastating form of glaucoma that usually presents following ocular surgery in patients with a history of angle closure. In rare instances, it can occur spontaneously in eyes with an open angle or following cataract surgery or various laser procedures. The disease presents with uniform flattening of both the central and peripheral anterior chamber (Fig 17-10). This is in contrast to acute PAC, which presents with iris bombé and a shallow peripheral anterior chamber (Fig 18-10). In malignant glaucoma, there is typically marked asymmetry between the affected anterior chamber and that of the fellow eye. Classically, the condition has been thought to result from anterior rotation of the ciliary body and posterior misdirection of the aqueous, in association with a relative block to forward aqueous movement at the level of the lens equator, vitreous face, and ciliary processes. However, this historical explanation is a matter of controversy, and some have proposed that it is not physically plausible but, rather, that malignant glaucoma may result from the simultaneous presence of several factors, including a small, anatomically predisposed eye, a propensity for choroidal expansion, and reduced vitreous fluid conductivity.
Clinically, the anterior chamber is shallow or flat, with anterior displacement of the lens, IOL, or vitreous face. Optically clear zones may be seen in the vitreous. Some experts argue this represents aqueous humor trapped in the vitreous cavity; however, this is controversial. In the early postoperative setting, malignant glaucoma is often difficult to distinguish from choroidal effusion, pupillary block, or suprachoroidal hemorrhage. Often, the level of IOP, time frame following surgery, patency of an iridotomy, or presence of a choroidal effusion or suprachoroidal hemorrhage helps the clinician make the appropriate diagnosis. In some cases, the clinical picture is difficult to interpret, and surgical intervention may be required in order to establish the diagnosis.
Figure 10-17 Ultrasound biomicroscopy (UBM) of an eye with malignant glaucoma. The lens–iris diaphragm is pushed forward, causing a uniform shallowing of the anterior chamber (AC). The central portion of the anterior lens capsule (LC) is nearly in contact with the cornea (C). Note ciliary body (CB) detachment, which is commonly seen in malignant glaucoma. I = iris; PC = posterior chamber; S = sclera.
(Courtesy of Robert Ritch, MD.)
Figure 10-18 UBM of an eye with acute primary angle closure. Pupillary block leads to forward bowing of the peripheral iris. The peripheral chamber is shallow, whereas the central chamber is relatively deep by comparison. AC = anterior chamber; C = cornea; CB = ciliary body; I = iris; LC = lens capsule; PC = posterior chamber; S = sclera.
(From Lundy DC. Ciliary block glaucoma. Focal Points: Clinical Modules for Ophthalmologists. American Academy of Ophthalmology; 1999, module 3. Courtesy of Jeffrey M. Liebmann, MD.)
Medical management includes the triad of intensive cycloplegic therapy; aggressive aqueous suppression with β-adrenergic antagonists, α2-adrenergic agonists, and carbonic anhydrase inhibitors; and dehydration of the vitreous with hyperosmotic agents. Miotics can make malignant glaucoma worse and should not be used. In aphakic and pseudophakic eyes, the anterior vitreous can be disrupted with the Nd:YAG laser. Laser photocoagulation of the ciliary processes reportedly has been helpful in treating this condition; this procedure may alter the adjacent vitreous face. In approximately half of patients, malignant glaucoma can be controlled with laser iridotomy and medical management; the other half require surgical intervention alone. The definitive surgical treatment is pars plana vitrectomy with anterior hyaloido-zonulectomy combined with iridectomy and an anterior chamber–deepening procedure. BCSC Section 12, Retina and Vitreous, discusses vitrectomy in detail.
Foreman-Larkin J, Netland PA, Salim S. Clinical management of malignant glaucoma [epub ahead of print December 24, 2015]. J Ophthalmol. 2015;2015:283707. doi:10.1155/2015/283707
Uveal and ciliary body effusions
Uveal effusion or uveal hemorrhage refers to fluid or blood in the potential space between the uvea (choroid and ciliary body) and the sclera. Causes include certain sulfonamide medications (see the section “Drug-induced secondary angle-closure glaucoma”), panretinal photocoagulation, inflammation, infection, penetrating surgery, scleral buckle surgery (see the section “Vitreoretinal surgery”), trauma, retinal vein occlusion, tumor, and uveal effusion syndrome. The suprachoroidal or supraciliary mass effect may result in secondary angle closure related to forward displacement of the lens–iris interface. In addition, exudative retinal detachments can act as space-occupying lesions in the vitreous, which may progressively push the retina forward toward the lens and cause angle closure. Potential causes of exudative retinal detachment include retinoblastoma, Coats disease, metastatic carcinoma, choroidal melanoma, suprachoroidal hemorrhage, choroidal effusion or detachment, infections (eg, HIV), and subretinal neovascularization in age-related macular degeneration with extensive effusion or hemorrhage.
Scleral buckles (especially the encircling bands) used to repair retinal detachments can produce shallowing of the anterior chamber angle and frank angle closure, often accompanied by choroidal effusion and anterior rotation of the ciliary body, causing a flattening of the peripheral iris with a relatively deep central anterior chamber. Vortex vein compression may be responsible for the choroidal effusion. Usually, the anterior chamber deepens with opening of the anterior chamber angle over days to weeks with medical therapy consisting of cycloplegics, anti-inflammatory agents, β-adrenergic antagonists, carbonic anhydrase inhibitors, and hyperosmotic agents. If medical management is unsuccessful, laser iridoplasty, drainage of suprachoroidal fluid, or adjustment of the scleral buckle may be required. The scleral buckle can impede venous drainage by compressing a vortex vein and thus elevating episcleral venous pressure and IOP. Such cases may respond only to moving the scleral buckle or releasing tension on the encircling band. Iridectomy is usually of no benefit in this condition.
Pars plana vitrectomy may lead to angle closure as a result of injection of air, long-acting gases such as sulfur hexafluoride and perfluorocarbon gases (perfluoropropane and perfluoroethane), or silicone oil into the eye. These substances are less dense than water and rise to the top of the eye. An iridotomy may be beneficial and should be located inferiorly to prevent obstruction of the iridotomy site by the gas or oil.
Eyes that have undergone complicated vitreoretinal surgery and have elevated IOP require individualized treatment plans. Therapeutic options include the following: removal of the silicone oil; release of the encircling element; removal of expansile gases; and primary glaucoma surgery, such as trabeculectomy, tube shunt surgery, or a cyclodestructive procedure.
Following panretinal photocoagulation, IOP may become elevated by an angle-closure mechanism. The ciliary body is thickened and rotated anteriorly, and, often, an anterior annular choroidal detachment occurs. Generally, this secondary angle closure is self-limited, and therapy consists of temporary medical management with cycloplegic agents, topical corticosteroids, and aqueous suppressants.
A nanophthalmic eye is normal in shape but unusually small, with a shortened axial length (< 20 mm), a small corneal diameter, and a relatively large lens for the volume of the eye. Thickened sclera may impede drainage from the vortex veins. These eyes are markedly hyperopic and highly susceptible to angle closure, which occurs at an earlier age than in PAC. Intraocular surgery is frequently complicated by choroidal effusion and nonrhegmatogenous retinal detachment. Choroidal effusion may occur spontaneously and may induce angle closure.
Laser iridotomy, laser peripheral iridoplasty, and medical therapy are the safest ways to manage IOP elevation in these patients. Surgery should be avoided if possible because of the high rate of complications. When intraocular surgery is performed, prophylactic posterior sclerotomies may reduce the severity of intraoperative choroidal effusion. If the angles remain compromised despite a patent iridotomy, lensectomy is an additional treatment option. In such cases, a limited core vitrectomy is sometimes necessary to provide adequate anterior chamber depth for safe lens removal. Many clinicians consider early lens extraction in patients with nanophthalmos to avoid the development of angle closure. In such cases, the surgeon should consider prophylactic measures to reduce the risk for clinically significant choroidal effusion, including sclerotomies, decompression of the eye with a Honan balloon, and systemic hyperosmotic agents such as mannitol.
Persistent fetal vasculature and retinopathy of prematurity
The contraction of retrolental fibrovascular tissue seen in persistent fetal vasculature (PFV; formerly known as persistent hyperplastic primary vitreous) and in retinopathy of prematurity can cause progressive shallowing of the anterior chamber angle with subsequent angle closure. In PFV, the onset of this complication usually occurs at 3–6 months of age during the cicatricial phase of the disease, although angle closure may occur later in childhood. Cataractous swelling of the lens can also cause angle closure. PFV is usually unilateral and often associated with microphthalmos and elongated ciliary processes. These conditions are discussed in more detail in BCSC Section 6, Pediatric Ophthalmology and Strabismus, and Section 12, Retina and Vitreous.
In retinopathy of prematurity, angle closure can also be related to a steeper cornea and a higher lens thickness to axial length ratio compared to normal eyes. Neovascularization of the iris is also occasionally associated with retinopathy of prematurity and may contribute to the development of angle closure. LPI can be performed as the first-line treatment of the angle closure. However, lens extraction, trabeculectomy, or tube shunt surgery may be necessary if the IOP cannot be controlled medically.
Drug-induced secondary angle-closure glaucoma
Topiramate, a sulfamate-substituted monosaccharide, is an oral medication prescribed in the treatment of epilepsy, depression, headaches, and idiopathic intracranial hypertension. In some patients, this medication may cause a syndrome characterized by acute myopic shift and acute bilateral angle closure. Patients with this syndrome experience sudden bilateral vision loss with acute myopia, bilateral ocular pain, and headache, usually within 1 month of starting topiramate. In addition to myopia, ocular findings in this syndrome include a uniformly shallow anterior chamber with anterior displacement of the iris and lens, microcystic corneal edema, elevated IOP (40–70 mm Hg), a closed anterior chamber angle, and ciliochoroidal effusion (Fig 19-10). Other medications associated with uveal effusion and secondary angle closure include acetazolamide, methazolamide, buproprion, and trimethoprim-sulfamethoxazole. Some recreational drugs, including MDMA (“ecstasy”), can also cause bilateral secondary angle closure.
Figure 10-19 Topiramate-induced angle closure. A, B-scan ultrasonogram of an eye with a very shallow anterior chamber (asterisk) and topiramate-induced angle closure. The choroidal effusion is clearly evident (arrows).B, Ultrasonographic view of an extremely shallow anterior chamber and closed angle (asterisk). The posterior choroidal effusion is clearly visible (arrow).
(Courtesy of Jonathan Eisengart, MD.)
The bilateral presentation of this type of angle closure should alert the clinician to the possibility of an idiosyncratic response to topiramate or other drugs. Treatment of this syndrome involves immediate discontinuation of the inciting medication and initiation of medical therapy, generally in the form of aqueous suppressants, to decrease the IOP. In addition, systemic corticosteroids may hasten recovery. Aggressive cycloplegia may help deepen the anterior chamber and relieve the attack. The secondary angle closure usually resolves within 24–48 hours with medical treatment, and the myopia resolves within 1–2 weeks of discontinuing topiramate. Because pupillary block is not an underlying mechanism of this syndrome, a peripheral iridotomy is not indicated.
Murphy RM, Bakir B, O’Brien C, Wiggs JL, Pasquale LR. Drug-induced bilateral secondary angle-closure glaucoma: a literature synthesis. J Glaucoma. 2016;25(2):e99–105.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.