Ординатура / Офтальмология / Английские материалы / Clinical Pathways in Glaucoma_Zimmerman, Kooner_2001

LENS PARTICLE GLAUCOMA

Definition

How Is Lens Particle Glaucoma Defined?

In this entity the release of lens particles is the result of trauma to the lens. This material circulates in the anterior chamber, blocking the trabeculum and causing a significant IOP elevation.31

Epidemiology and Importance

Extracapsular cataract surgery is the method of choice for surgeons in the United States29 and most countries around the world. Surgeons who operate on the anterior segment know that small amounts of cortex left in the eye cause no significant complications. This material is usually handled by the cellular and drainage mechanisms of the eye.30 As a result, postoperative IOP elevations and inflammation are usually moderate, transient, and responsive to medical treatment. As surgical techniques continue to improve, lens-related complications will decrease in frequency.

What Is the Pathogenesis of Lens Particle Glaucoma?

In some instances this material adopts a particulate pattern and causes a significant blockage of aqueous outflow.31 The resulting elevation in IOP is proportional to the amount of material released, stressing the mechanical nature of the obstruction and the resulting glaucoma. Macrophages, inflammatory cells, and debris can add to the blocking effect of the lens matter30 (see Tables 10–4 and 10–5).

Diagnosis and Differential Diagnosis

How Is Lens Particle Glaucoma Diagnosed?

The glaucoma can occur weeks, months, or even years after the trauma (or surgery).30 Patients usually present with ocular pain and decreased vision in one eye. White, fluffy lens material can be seen in the anterior chamber in addition to a moderate amount of cells and flare. In extreme cases, a hypopion may be present. The anterior chamber angle is usually open. Macrophages containing lens proteins (as in phacolytic glaucoma) have also been identified31 and may play a role in further blocking the trabeculum.30

In addition to the mechanical obstruction of the open angle by various components, untreated inflammation and its secondary changes (peripheral anterior or posterior synechiae, angle scarring, pupillary membranes, and pigment deposition) can play additional roles in the pathogenesis of the glaucoma.1,30,31 Cystoid macular edema can result in further visual loss.

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What Is the Differential Diagnosis

of Lens Particle Glaucoma?

The diagnosis of this condition begins with the documentation of either surgical or nonsurgical lens trauma. Typical fluffy material in the anterior chamber, some inflammation, and elevated IOP with an open angle are strong diagnostic components. The differential diagnosis with other conditions that may mimic lens particle glaucoma are discussed below and illustrated in Figure 10–3.

Phacoanaphylaxis is another entity that can follow traumatic capsular disruption and should be considered in the differential diagnosis. As inflammation is the overriding problem, the IOP tends to be low. In the few cases where the IOP is high, phacoanaphylactic glaucoma results. Granulomatous inflammation with large keratic precipitates strongly suggests phacoanaphylaxis rather than lens particle glaucoma.30

In phacolytic glaucoma the lens capsule is grossly intact and a mature or hypermature cataract is present. A history of trauma is not a typical feature of this syndrome. White, fluffy material is not seen because the capsule has not been ruptured. On the other hand, a phacolytic component may be present in lens particle glaucoma if macrophages engulf lens proteins and contribute to outflow blockage.30, 31 In less typical cases (specially postsurgical), an aqueous sample should be examined to rule out infectious endophthalmitis. An intraocular tumor could seed cells into the anterior chamber, but a thorough preoperative examination should have diagnosed the problem.

Treatment and Management

How Is Lens Particle Glaucoma Treated?

The initial therapy is medical and consists of aqueous suppressants, antiinflammatory drugs, and cycloplegics.30,31 If prompt improvement does not take place the definitive therapy consists of surgically removing all remaining lens fragments (Fig. 10–4). Delaying intervention can result in entrapment of lens material between capsular flaps or inflammatory membranes, making a late removal more problematic.30 Acting promptly when patients with a history of trauma or cataract surgery complain of sudden pain or decreased vision will prevent serious complications and permanent visual loss.

Can Nd:YAG Laser Posterior Capsulotomy Cause Lens

Particle Glaucoma?

Some patients develop significant IOP elevation and inflammation following Nd:YAG laser posterior capsulotomy.32,33 Several features place this syndrome apart from classical lens particle glaucoma. First, the small amount of material released by the procedure does not explain an outflow obstruction on a purely mechanical basis. In addition there is no correlation between IOP level and amount of material floating in the anterior segment.30 It has been shown that the IOP elevation does result from decreased outflow, but the precise mechanism is not fully understood.33 Small, nonvisible lens particles or vitreous components blocking the trabeculum have been postulated as possible sources of

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obstruction.34,35 It may be better to reserve the term lens particle glaucoma for eyes with visible lens particles floating in the anterior chamber. This is not the case in the majority of patients with glaucoma after YAG capsulotomy. A small percentage of these patients will develop full-blown open-angle glaucoma and require conventional long-term medical therapy or filtering surgery.

Future Considerations

With current improvements in surgical techniques, lens particle glaucoma may continue to be seen more often in association with lens trauma than with cataract surgery. In both instances the removal of the lens material may require a more complex approach such as pars plana vitrectomy and lensectomy. It is hoped that future techniques will allow a safer IOL implantation in cases where the entire lens is removed.

Is There a Cataract, But a History of Trauma is Not Present?

When faced with a nontraumatic cataract and glaucoma, a crucial diagnostic element is the evaluation of the anterior chamber angle (see Fig. 10–3).

Is the Angle Open?

If the angle is open, one must carefully examine the lens to determine if one is dealing with a mature or hypermature cataract.

PHACOLYTIC GLAUCOMA

Definition

How Is Phacolytic Glaucoma Defined?

In this condition a particular type of lens proteins (see below) leak through the capsule and along with macrophages block the trabeculum, causing an IOP elevation. Usually a long-standing significant cataract is present.

What Is the Pathogenesis of Phacolytic Glaucoma?

If the cataract is mature or hypermature (rarely immature), the stage is set for phacolytic glaucoma. These cataracts have an increased amount of high molecular weight (HMW) soluble lens proteins.31 These proteins can leak through microscopic defects in the capsule and circulate in the anterior chamber. Current evidence indicates that the trabecular meshwork is blocked by both HMW proteins and macrophages containing engulfed proteins.35–37 It has been suggested that these proteins may be more specific and more closely responsible for the outflow blockage seen in phacolytic glaucoma.31 Crystals of calcium oxalate and cholesterol have also been identified in the anterior chamber38 (see Tables 10–4 and 10–5).

Epidemiology and Importance

Phacolytic glaucoma is uncommon in the United States, as cataracts are usually removed before they mature.29 Large series of patients with this entity come from countries where easy access to surgical eye care is not as readily available.38,39 In one such series, 45 consecutive patients were operated on during a 5-year period with excellent visual results and IOP control.38 There was no gender preference, and ages ranged from 45 to 85 years. Another series, reporting 44 phacolytic glaucomas and 49 phacomorphic (see next section) glaucomas diagnosed during 1 year, confirms the frequency of lens-induced glaucoma in other parts of the world.39

Diagnosis and Differential Diagnosis

How Is Phacolytic Glaucoma Diagnosed?

Because a cataract must be present, this disease usually presents in elderly adults. The sudden onset of open-angle glaucoma in an eye with a mature or hypermature cataract should be considered as phacolytic glaucoma until proven otherwise. These patients present with ocular pain and a prior history of decreased vision due to the cataract. A recent worsening in vision may have occurred.30 The eye appears injected and the IOP may be markedly elevated, causing corneal edema. The anterior chamber is formed, showing significant flare (soluble proteins) and variable amount of cells. These cells consist of small white cells and larger floating macrophages containing lens proteins.31 The filtration angle is open and appears grossly normal. The lens is opaque, and in some hypermature cataracts a brunescent nucleus rests inferiorly in a bag of liquefied cortex (morgagnian cataract). The anterior capsule may appear irregular or wrinkled, sometimes with whitish patches on its surface.31 In some cases the lens may luxate posteriorly, eventually falling into the vitreous cavity.

What Is the Differential Diagnosis

of Phacolytic Glaucoma?

Refer to the section on differential diagnosis of lens particle glaucoma, above, for a comparison of phacolytic glaucoma with the most pertinent acute lens-induced glaucoma entities. If the history and examination are consistent and other types of open-angle glaucoma can be ruled out (e.g., neovascular, traumatic, inflammatory), the diagnosis can be reliably made on clinical grounds. If there is doubt, the microscopic examination of an aqueous sample looking for engorged macrophages is indicated. Using the Millipore® filter technique facilitates the identification of the macrophages.31 False negatives can occur, especially in eyes treated with steroids. Uveitis in the presence of a cataract (but not caused by it) is a major diagnostic category to be ruled out because the extraction of the cataract will cure phacolytic glaucoma but dangerously excacerbate the uveitis. Once again, in these cases the examination of the aqueous humor becomes critical.

As we continue to analyze the differential diagnosis in Figure 10–3 we reach another important question:

206 Glaucoma Associated with Lens Disorders

Treatment and Management

How Is Phacolytic Glaucoma Managed?

The initial treatment consists of hyperosmotic agents, aqueous suppressants, antiinflammatory drugs, and cycloplegics to temporarily control the disease (see Fig. 10–4). The definitive treatment currently consists of extracapsular extraction of the lens with or without intraocular lens implantation and should be carried out as soon as it is reasonably safe. Unless PAS or trabecular damage is present, the removal of the lens uniformly eliminates the glaucoma and provides excellent visual rehabilitation.39,40 Although not always feasible, the eye should be open after the IOP has been maximally lowered. If the IOP remains high, a paracentesis should be performed to partially decompress the globe before proceeding.1 If there is significant zonular dehiscence or difficulty opening the anterior capsule, an intracapsular lens removal30 with anterior chamber or sutured posterior chamber intraocular lens implantation can be considered. Some surgeons may choose to delay the implantation of the lens until the inflammation has subsided. In one large series the IOL implantation was not a factor affecting the final visual acuity (p = .18).41 Univariate analysis performed in this study showed that patients over 60 years of age with more than 5 days of disease had a higher risk of poor visual outcome. Visual acuity of light perception without projection has not been a poor prognostic indicator in many cases.39

Future Considerations

The management of phacolytic glaucoma consists of removing the lens, and the tendency is toward extracapsular surgery with primary IOL insertion.39,40 The use of viscoelastic materials has allowed a more controlled treatment of the capsule, and small-incision surgery may further improve the visual prognosis in these eyes. Cataract surgery in phacolytic glaucoma will continue to be a challenge.39

Is the Angle Closed?

If this is the case, the iris is being pushed against the cornea by either trapped aqueous humor or an enlarged lens. One or both of these components mechanically occlude the angle.

Is the Lens Intumescent?

This can be determined by careful anterior segment biomicroscopy complemented by ultrasonic studies. The axial diameter of the lens is significantly increased. Usually the lens appears white and the cataract is mature. The formation of an intumescent lens can occur over a variable period of time, often becoming noticeable by the pain induced by the elevated IOP. An intumescent lens in the presence of a closed angle is currently known as phacomorphic glaucoma (see Fig. 10–3).

PHACOMORPHIC GLAUCOMA

Definition

How Is Phacomorphic Glaucoma Defined?

This definition implies that the lens is mechanically exerting a direct “pushing” effect on the iris, causing the closure of the angle. This can result from an anteriorly dislocated lens or, most commonly, from an enlarged lens.1,2

Epidemiology and Importance

Because phacomorphic glaucoma due to an intumescent lens occurs in cases of advanced, long-standing cataracts, the concepts mentioned in the previous section on phacolytic glaucoma apply to phacomorphic glaucoma as well. Again, this is an uncommon entity in the United States, and large series come from overseas.41

What Is the Pathogenesis of Phacomorphic Glaucoma?

In an eye with a nontraumatic cataract and a closed anterior chamber angle, the possibility of phacomorphic glaucoma should be entertained. The term phacomorphic has been traditionally associated with an intumescent lens.1,2,31,35 Intumescence results from influx of water and swelling of the lens cortex, rarely the nucleus. This usually occurs in mature senile, diabetic, uveitic, and traumatic cataracts. The result is distention of the capsule and an increase of the axial diameter of the lens41 (see Table 10–5).

An enlarged lens can cause angle-closure glaucoma via two mechanisms. First, an increased iris-lens contact results in a relative pupillary block, and second, the enlarged lens can directly push the iris (phacomorphic effect) forward against the cornea, occluding the angle. Usually, whenever phacomorphic glaucoma is present, there is some degree of pupillary block.42,43 Eyes with narrow angles are more likely to suffer from this type of angle closure.4,43

Is the Lens Nonintumescent, But Still Large?

An increase in the axial diameter of the lens can also occur without intumescense, most commonly as a result of a growing cataract. In eyes with narrow angles (hyperopia, small globes with shallow anterior chambers), a phacomorphic component will result from simple lens enlargement, making acute pupillary-block glaucoma more likely.42 This is probably one of the mechanisms behind primary angle-closure glaucoma. In addition, a clear lens could become “too large” for the eye, acting mechanically to activate the mechanisms previously described. We see how the size of the lens and its spatial relationships with surrounding structures can create circumstances in which a pupillary-block component coexists with a phacomorphic component.42

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Diagnosis and Management

How Is Phacomorphic Glaucoma Diagnosed?

The diagnosis is usually based on the clinical examination. We should suspect phacomorphic glaucoma in any eye with angle-closure glaucoma and an advanced cataract. Usually the vision is poor, the patient is in pain, and the eye is injected. The cornea can be edematous due to the increased IOP.4 The angle appears closed and cannot be opened upon reasonable corneal indentation. Low-grade inflammation can sometimes be observed in a uniformly shallow anterior chamber. If the examination of the fellow eye reveals a deeper central anterior chamber, it is likely that lens swelling is present in the involved eye.4

On clinical examination what differentiates phacomorphic glaucoma from pure pupillary-block glaucoma is the equal shallowness of the axial and peripheral anterior chamber. In pupillary block the iris bombé gives the axial chamber a greater depth than in phacomorphic glaucoma. An intumescent lens is commonly seen, but a totally dislocated lens in the posterior chamber can be present. Ultrasound biomicroscopy can neatly delineate the various surfaces involved in the pathogenesis of this and other types of angle-closure glaucoma.44

What Is the Differential Diagnosis

of Phacomorphic Glaucoma?

Figure 10–3 illustrates the thinking pathway as we deal with patients with cataract and angle-closure glaucoma. Other causes of angle closure should be first ruled out. Usually a good history and a detailed anterior segment examination will identify traumatic glaucoma, neovascular glaucoma, exfoliation glaucoma, phacolytic glaucoma, and the various types of angle-closure glaucoma. In addition, the differential diagnosis includes miotic therapy, aqueous misdirection, and uveal effusion, all of which can exert the same effect on the iris and angle.42 As the view of the posterior pole is impeded by the cataract, a B-scan should be done to rule out a retrolenticular tumor causing the anterior displacement of the lens.45 Ultrasonography will also identify choroidal effusions and iris cysts, which can result in angle-closure glaucoma.44

Treatment and Management

How Is Phacomorphic Glaucoma Managed?

As in other entities discussed in this chapter, it is desirable to reduce inflammation and IOP medically before definitive surgical treatment is undertaken. The initial treatment, therefore, consists of hyperosmotics, aqueous supressants, and antiinflammatory agents. Cycloplegics may not be able to deepen the anterior chamber and may further crowd the angle. Miotics can worsen the pupillary block or create one by pulling the iris-lens diaphragm forward. The definitive therapy consists of removal of the lens with or without IOL placement.4,31,42 If the IOP can be medically controlled and a large intumescent lens is present, lens removal can be the first and definitive surgical approach.

It appears that in most cases there is a significant component of pupillary block; therefore, a YAG laser PI is indicated as an effective way of lowering the IOP to safe levels.4,42,46 If the pupillary block is broken and the IOP controlled, lens extraction can be performed under safer circumstances. A reasonable approach, therefore, would consist of medical treatment initially with a PI to follow in preparation for cataract removal. If a PI does not open the angle, then removal of the lens should be performed. Laser peripheral iridoplasty has also been suggested as an option for some phacomorphic glaucomas,4,47 but is not widely used in this setting.

In the presence of a visually significant cataract, the goals are to visually rehabilitate the eye and prevent permanent optic nerve and trabecular damage as well as peripheral anterior synechiae. Lens extraction under the best possible circumstances will achieve all these goals. The removal of an intumescent lens poses particular challenges as the milky cortex will leak out as soon as the anterior lens capsule is perforated. Initial decompression of the lens and generous use of viscoelastic material usually permits a more controlled anterior capsulotomy. Successful continuous-tear capsulorhexis has been performed using this technique, allowing in-the-bag IOL placement.48

Future Considerations

New techniques and viscoelastic use allow safe management of these eyes. When safe extracapsular surgery cannot be performed, pars plana lensectomy with anterior chamber or sutured IOL placement will continue to be an appropriate alternative.

GLAUCOMA ASSOCIATED

WITH EXFOLIATION SYNDROME

Definition

How Is Exfoliation Syndrome Defined?

Exfoliation syndrome (ES) is a systemic basement membrane disorder that results in the production and deposition of abnormal material throughout the eye and other system organs. In conjunction with the lens abnormalities, a particular type of secondary open-angle glaucoma results in some patients.49,50

Epidemiology and Importance

The reported incidence and prevalence of this disease has significantly increased in recent years across the racial spectrum.51–56 An increased awareness of the disease and more thorough examinations under full pupillary dilatation partially explains this trend.57 Despite these data, the prevalence of ES in the general population remains linked to racial and ethnic factors, varying from almost zero among Eskimos to about 25% in Scandinavia and 38% in Navaho Indians.49,58 The prevalence of ES markedly increases with age in all