eMedicine Specialties > Ophthalmology > Intraocular Pressure

Glaucoma, Aphakic And Pseudophakic

Author: Robert H Graham, MD, Senior Associate Consultant, Department of Ophthalmology, Mayo Clinic, Scottsdale, Arizona
Contributor Information and Disclosures

Updated: Feb 11, 2009

Introduction

Background

Glaucoma associated with aphakia, but particularly pseudophakia, are important considerations given the more than 1.25 million cataract surgeries performed each year.

Glaucoma in this article refers to conditions that cause increased intraocular pressure (IOP) soon after surgery as well as to those conditions that occur much later. Examples include viscoelastic-associated pressure rise measured in hours to ghost cell glaucoma occurring weeks after surgery.

Pathophysiology

The pathophysiology is dependent on the mechanism involved and includes the following: distortion of the anterior chamber angle, viscoelastics, inflammation, hemorrhage, pigment dispersion, ghost cell, vitreous in the anterior chamber (AC), pupillary block (pseudophakic/aphakic), malignant glaucoma, and posterior capsulotomy.

Frequency

United States

Duke-Elder estimated a 12% incidence of postoperative glaucoma in 1969.¹ However, the landscape of postcataract complications has been altered by the advent of the intraocular lens (IOL) and fine wound-closure techniques. In the modern era, the incidence of glaucoma is dependent on both the methodology and the type of IOL used.

For instance, Cinotti has noted an increased incidence of glaucoma after extracapsular cataract extraction (ECCE) (7.5%) as compared to intracapsular cataract extraction (ICCE) (5.7%).²

Further, Stark has noted that AC IOL (5.5-6.3%) has been associated with an increased incidence of postoperative IOP elevation over iris-fixation (3.9-4.3%) lens and posterior chamber (PC) IOL (1.6-3.5%).³ These figures are consistent with those reported by Hoskins, in which he observed 5.5% in AC IOL and 1.6% in PC IOL.⁴ However, congenital cataract surgeries are associated with a higher incidence of glaucoma, and data range from 6.1-24%.

Mortality/Morbidity

Without good IOP control, glaucoma may result in blindness.

Age

This condition may occur at any age after cataract surgery; however, cataracts are most commonly found in the elderly population.

Clinical

History

The history is dependent on the specific cause of the pressure rise. In general, inquiry into the patient's phakic status as well as the operative course and the use/removal of viscoelastic substances are important historical considerations. For instance, a patient with pseudophakic pupillary block may present with a recent history of cataract surgery complaining of intense pain, red eyes, hazy cornea, and headache.

Also, remember that the clinical presentation may be identical to that of phakic patients and that the specific diagnosis may depend on the historical features described above.

Physical

The ocular examination reveals increased IOP with the accompanying symptoms.

Causes

• Viscoelastic substances
  • The advent of viscoelastic material has allowed greater flexibility in the surgical routine by promoting tissue protection and space stabilization. However, its use also has been associated with pressure spikes in the early postoperative period. For instance, sodium hyaluronate (Healon) has been shown to be associated with maximal IOP spike 16 hours postoperatively in patients undergoing ICCE and a 65% decrease in outflow facility in enucleated eyes. The postoperative pressure spike has not been shown to be relieved with aspiration of the viscoelastic substance. It also has been postulated that small fragments of this substance may become lodged in the trabecular meshwork.
  • Alternative substances, such as methylcellulose, chondroitin sulfate, combination of sodium hyaluronate with chondroitin sulfate (Viscoat), and modified Healon (Healon GV), have been studied but without significant improvement. For instance, chondroitin sulfate has been shown to be 20 times less viscous than Healon. However, Healon GV, a combination of Healon and chondroitin sulfate, has not shown any advantage. Methylcellulose 1-2% has been found to cause postoperative pressure elevation.
  • Whether to aspirate the viscoelastic substance is dependent on the clinical situation and personal creed. For instance, it may be necessary to aspirate in advanced glaucoma to minimize postoperative spike. However, retention and replacement of viscoelastic substance may be necessary in patients presenting with shallow anterior chamber to protect the corneal endothelium.
• Pigment dispersion, inflammation, and hemorrhage
  • Inflammation and hemorrhage are inevitable consequences of surgery, and they may lead to fibrosis and anatomical distortion when excessive. Fibrosis is more common in certain patient populations (eg, diabetes, uveitis), in the IOL (eg, AC IOL, iris fixation), and as complications (eg, retained lens fragment).
  • The clinical triad of uveitis, glaucoma, and hyphema, especially associated with early AC IOL, has been well described as UGH syndrome. Glaucoma is believed to be caused by movement of the IOL against the iris causing the release of inflammatory and red blood cell debris that obstruct the trabecular meshwork. The haptic also may cause direct damage to the trabecular meshwork, thus contributing to the glaucoma. Uveitis was particularly common if metal clip lenses were used. Components of this condition may be reversed if the offending IOL is removed before permanent damage has occurred.
  • Retained cortical material in the AC is another cause of inflammation, which may lead to glaucoma. These are visible as fluffy, white material and may cause a delayed-onset pressure spike. The level and severity of inflammation correlates with the amount of cortical material. Significant amounts of cortical material can be sequestered out of sight in the bag.
  • Aqueous suppressants are helpful to reduce IOP, as are corticosteroids to treat inflammation and to prevent synechiae formation, but this can slow the resorption of lens material. Miotics should be avoided given their tendency to increase vascular permeability, leading to increased inflammation. Surgical aspiration is necessary if medical therapy is inadequate or if phacoanaphylactic uveitis with glaucoma occurs. In such an event, steroids are used to quiet the eye, glaucoma medications are used for IOP stabilization, and complete surgical removal of the cortex is done.
  • Iris pigment can be released by the IOL haptic contact with the iris (especially PC IOL) and clog the trabecular meshwork. This condition is similar to pigment dispersion occurring in phakic patients and can be associated with radial transillumination defects and deposition of pigments on the endothelium (Krukenberg spindle) and zonules. Hemorrhage also can be associated with incarcerated iris vessels, which may be reduced with careful closure.
• Ghost cell glaucoma
  • Late-onset glaucoma secondary to retained RBCs, as opposed to hyphema due to fresh RBCs, can occur over weeks to months. Sequestered RBCs in the vitreous lose hemoglobin (Hb) and become the less pliable Heinz bodies. These cause obstruction of the trabecular meshwork and a pressure spike. The ghost cells do not migrate to the AC, unless the anterior hyaloid face is broken. In such cases, the anterior chamber contains floating tan cells, which may be confused for inflammatory cells.
  • Diagnostically, steroids are not effective, and one may observe layering of tan erythroclasts and fresh RBCs, known as the candy stripe sign. Medical therapy is sometimes effective, but AC washout may be needed. However, IOP usually increases again in 1-3 days, thereby necessitating a vitrectomy to eliminate the reservoir of RBCs in the vitreous in some cases.
• Pupillary block in aphakia
  • Given the paucity of conditions that warrant aphakia today, this condition rarely is seen, except in aphakic patients undergoing additional procedures. Apposition of the intact anterior hyaloid face to the pupil or iridectomy site presenting as iris bombé is the main mechanism for pressure elevation. Predisposing factors include a prolonged period of flat chamber, severe postoperative inflammation, and failure of peripheral iridectomy. As in AC vitreous, posterior vitreous detachment also is a predisposing factor. Eventually, posterior synechiae may develop between the posterior iris surface and the anterior hyaloid face and lead to complete pupillary block.
  • Clinical signs of pupillary block include the following: (1) increased shallowing of the peripheral iris, (2) segmental block/irregular shallowing (eg, loculation of the vitreous behind the iris), and (3) overall shallowing of the AC. The central AC is deep, and forward bowing of the peripheral iris occurs in this condition, which distinguishes it from malignant glaucoma.
  • While Chandler and Grant included increased IOP in their classic description of the clinical findings, others assert that IOP is not a reliable indicator because 50% of patients with aphakic pupillary block had IOP less than 21 mm Hg.⁵ They postulate that IOP in the reference range can be achieved by concurrent conditions, which decrease the IOP, such as uveitis, wound leak, and choroidal detachment.
  • Aphakic pupillary block can occur anytime after surgery, and an increased incidence after congenital cataract extraction has been noted. This may be associated with the increased strength of the anterior hyaloid in this population. Medical treatment includes aggressive dilation, aqueous suppression, cycloplegics, and hyperosmotic agents. Iridotomy and anterior hyaloidotomy ultimately may be required.
• Pupillary block in pseudophakia
  • Pseudophakic pupillary block can be associated with all types of IOL. Risk factors include excessive inflammation causing posterior synechiae (PC IOL and iris-fixation IOL), to direct insult of the trabecular meshwork (AC IOL). Shields notes that the incidence of pupillary block is sufficiently low as to not warrant routine iridectomy with cataract surgery.⁶ However, the following should be considered: iridectomy when excessive inflammation is expected, using iris-fixation lens or rigid uniplanar anterior chamber IOL, or in combination with filtering procedures. Diabetics are associated with increased inflammation and increased thickness of the iris and ciliary body, which may increase the risk of pupillary block. Even a successful iridectomy can be occluded by vitreous, intraocular lens rotation, inflammatory membrane, or lens remnants, and cause pupillary block.
  • The clinical presentation is similar to pupillary block due to other etiologies. Shields notes that (1) IOP is normal unless the patient has concurrent angle closure, (2) increased diurnal variation in the AC depth and IOP is present, and (3) decreased peripheral angle depth is present.⁶ Further investigative methods may include ultrasound biomicroscopy, Scheimpflug video imaging, and optical coherence tomography.
• Aqueous misdirection syndrome
  • First described by von Graefe in 1869, malignant glaucoma denotes a process involving shallowed AC associated with increased IOP. Although typically occurring early in the postoperative period, it can be delayed by weeks or years.
  • Mechanistically, apposition of the ciliary process against the lens or vitreous, posterior diversion of aqueous, and iris abutting against the AC angle by forward displacement of the lens have been proposed. In patients with AC IOL, the mechanism probably involves posterior displacement of the iris against the anterior hyaloid face by the IOL.
  • Complicating 0.6-4% of eyes following surgical intervention for acute angle-closure glaucoma, it also has been associated with the addition of a miotic or cessation of a mydriatic. Malignant glaucoma has been associated in both aphakia and pseudophakia. Pupillary block, choroidal detachment, and suprachoroidal hemorrhage are considered in the differential diagnosis.
  • Historically, the importance of disrupting the vitreous was noted first by Chandler in 1950 when lens removal as treatment for aqueous misdirection was not curative unless vitreous was lost during the procedure.⁵ Today, medical therapy may be curative and includes aqueous suppression, cycloplegia, and hyperosmotic agents. Hyperosmotics decrease the pressure exerted by the vitreous, whereas cycloplegics likely pull the lens back by tightening the zonules. If the condition persists, YAG capsulotomy to disrupt the anterior hyaloid face or the posterior capsule may be needed. Vitrectomy with chamber deepening may be required.
• Nd:YAG posttreatment elevation of IOP: Production of fibrous matrix and contraction of the capsule caused by migrated lens epithelial cells cause visually significant posterior capsular opacification in 50% of patients 3-5 years after ECCE necessitating Nd:YAG capsulotomy. In one study involving 49 capsulotomies, increased IOP was noted in 37 eyes (75%) with pressure peak at 3 hours and average return to baseline at 1 week. Further, patients with preexisting glaucoma were at a higher risk of developing elevated IOP. This has been postulated to be caused by the obstruction of outflow by capsular debris, inflammatory cells, and heavy molecular weight protein. In another study, pressure elevation at 1 hour was correlated with the ultimate pressure elevation. For instance, if the 1-hour elevation was greater than 5 mm Hg, then this was associated with a final pressure elevation greater than 10 mm Hg.
• Distortion of AC angle: Kirsch showed the presence of a white ridge resembling an inverted snowbank in the early postoperative period, which protruded into the AC from the region of the internal lips of the cataract incision.⁷ Whether this represents corneal stromal edema or tight corneoscleral suture remains debated. However, Kirsch showed that this structure was associated with peripheral anterior synechiae, vitreous adhesion, and hyphema, all of which could cause elevated IOP.⁷
• Vitreous in AC: Vitreous can protrude into the AC and block the trabecular meshwork. This condition usually occurs weeks to months postoperatively. Extensive posterior vitreous detachment that displaces the vitreous forward may predispose to this condition. Spontaneous resolution usually occurs in several months. Diagnosis is based on both clinical suspicion and visualization of the vitreous extending into the AC and the trabecular meshwork. If treatment is warranted, mydriatic therapy is effective in allowing the vitreous to fall back into the vitreous cavity, as are aqueous suppressants for temporary relief while the condition resolves.
• Epithelial or fibrous ingrowth is a rare cause of postcataract surgery glaucoma.

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