Lens-Associated Open-Angle Glaucomas
Michele C. Lim
Ashley G. Lesley
INTRODUCTION
Lens-associated open-angle glaucomas are composed of three separate diagnoses with similar clinical presentations. Lens protein glaucoma, lens particle glaucoma, and lens-associated uveitis (LAU) may each present with intraocular inflammation, an abnormal lens, and elevated intraocular pressure (IOP), although hypotony may commonly occur in the latter. Distinguishing among the three entities requires careful examination and an understanding of the mechanisms that define each diagnosis (Table 15-1).
TABLE 15-1. Clinical Presentation of Lens-Associated Open-Angle Glaucomas | ||||||||||||||||||||||||||||
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LENS PROTEIN OR PHACOLYTIC GLAUCOMA
Lens protein glaucoma occurs in the presence of a mature or a hypermature cataract (Fig. 15-1). Soluble lens proteins seep into the anterior chamber and obstruct the trabecular meshwork, causing an elevation in IOP.
Pathophysiology
• In lens protein glaucoma, heavy-molecular-weight (HMW) proteins (greater than 150 × 106 Da) obstruct trabecular meshwork outflow, causing a rise in IOP. Previously, it was thought that the rise in pressure resulted exclusively from macrophage outflow obstruction, based on the fact that they were identified in the aqueous humor and in the trabecular meshwork of patients with lens protein glaucoma1,2 (Fig. 15-2). However, Epstein et al.3,4 suggested that HMW proteins obstruct the trabecular meshwork based on the following experimental evidence:
Epstein sampled aqueous fluid of patients with phacolytic glaucoma and showed an abundance of HMW proteins, which increase in concentration as the cataract matures.
In vitro perfusion of cadaver eyes with HMW soluble proteins caused a 60% decrease in outflow facility after 1 hour.
The HMW proteins were present in high-enough concentrations in the aqueous humor of patients with lens protein glaucoma to cause obstruction of outflow.
Several of the eyes with phacolytic glaucoma had a paucity of macrophages.
• Lens proteins can induce the migration of peripheral blood monocytes5 and macrophages probably function as scavengers to remove soluble lens proteins and fragments from the anterior chamber and trabecular meshwork.
History
• Patients report gradually diminishing vision from the mature or hypermature cataract and pain from inflammation and elevated IOP.
Clinical Examination
• Lens protein glaucoma occurs in the presence of a mature or hypermature cataract. These patients have an acutely elevated IOP, ocular redness, and pain. There is intense flare, which correlates with soluble proteins released from the mature cataract (Fig. 15-3). A cellular response composed mostly of macrophages is present, and the cells appear larger and more translucent than lymphocytes (Fig. 15-4). Hypopyon is uncommon.
• White patches may be observed on the lens and are thought to correspond to aggregates of macrophages phagocytosing lens proteins at leakage sites on the capsule.
• Gonioscopy reveals open angles. A retinal perivasculitis has been observed in some cases.6
Special Tests
• Samples taken from the aqueous humor and concentrated via Millipore filtration may reveal macrophages and an amorphous substance corresponding to lens protein.
• The diagnosis is usually made on clinical observation alone.
Treatment
• Management of lens protein glaucoma should start with medical therapy to temporize the elevated IOP. Beta-blockers, prostaglandin analogs, alpha-adrenergic drugs, and carbonic anhydrase inhibitors are the mainstays of medical therapy. Topical steroids to reduce the inflammation and cycloplegics
to stabilize the blood-aqueous barrier and to reduce pain may also be used.
to stabilize the blood-aqueous barrier and to reduce pain may also be used.
• Medical therapy may help partially lower the pressure, but definitive treatment can only be obtained by removal of the cataract. In developing countries, small-incision extracapsular cataract surgery has been shown in a case series to be a safe and effective method of surgical therapy with minimal morbidity.7
REFERENCES
1. Hogan M, Zimmerman L. Ophthalmic Pathology: An Atlas and Textbook. 2nd ed. Philadelphia, PA: WB Saunders; 1962:797.
2. Irvine S, Irvine A. Lens-induced uveitis and glaucoma. Am J Ophthalmol. 1952;35:489.
3. Epstein D, Jedziniak J, Grant W. Identification of heavy-molecular-weight soluble protein in aqueous humor in human phacolytic glaucoma. Invest Ophthalmol Vis Sci. 1978;17(5):398-402.
4. Epstein D, Jedziniak J, Grant W. Obstruction of aqueous outflow by lens particles and by heavy-molecular-weight soluble lens proteins. Invest Ophthalmol Vis Sci. 1978;17(3):272-277.
5. Rosenbaum J. Chemotactic activity of lens proteins and the pathogenesis of phacolytic glaucoma. Arch Ophthalmol. 1987;105:1582.
6. Uemura A, Sameshima M, Nakao K. Complications of hypermature cataract: Spontaneous absorption of lens material and phacolytic glaucoma-associated retinal perivasculitis. Jpn J Ophthalmol. 1988;32(1):35-40.
7. Venkatesh R, Tan CS, Kumar T, et al. Safety and efficacy of manual small incision cataract surgery for phacolytic glaucoma. Br J Ophthalmol. 2007;91:279-281.
 FIGURE 15-1. Mature cataract. Mature cataract with folds in the anterior capsule. (Courtesy of Donald L. Budenz, MD, MPH University, North Carolina, Chapel Hill.) |
 FIGURE 15-2. Lens protein glaucoma. Macrophages in the trabecular meshwork in lens protein glaucoma. (Courtesy of Donald L. Budenz, MD, MPH University, North Carolina, Chapel Hill.) |
 FIGURE 15-3. Lens protein glaucoma. Intense anterior chamber inflammation with mature cataract in lens protein glaucoma. (Courtesy of Donald L. Budenz, MD, MPH University, North Carolina, Chapel Hill.) |
 FIGURE 15-4. Lens protein glaucoma. Hypermature cataract (A and B) with clumps of inflammatory cells on the lens face (white arrows). (Courtesy James D. Brandt, Department of Ophthalmology and Vision Science, University of California, Davis, Sacramento, CA.) |
LENS PARTICLE GLAUCOMA
Lens particle glaucoma occurs when the lens capsule is disrupted and lens cortex and proteins are released into the anterior chamber. This may occur after extracapsular cataract surgery, lens trauma with capsular disruption, and neodymium (Nd):YAG posterior capsulotomy in which liberated lens particles obstruct the trabecular meshwork, reducing aqueous outflow. Lens particle glaucoma after subluxation of a posterior chamber intraocular lens in a patient with pseudoexfoliation syndrome has also been reported1 (Figs. 15-5 and 15-6). Figure 15-7 shows an extreme case of lens particle glaucoma in which a hypermature cataract with phacodonesis progressed to dislocation into the anterior chamber with disruption of the capsular bag and led to high IOP.
Pathophysiology
• The elevated IOP in lens particle glaucoma can be caused by the following:
Lens particles obstructing the trabecular meshwork
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