Block Glaucoma

L. Jay Katz


BASICS


DESCRIPTION


• Pupillary block is the most common mechanism responsible for angle closure.


• It is caused by increased resistance to flow of aqueous from the posterior chamber to the anterior chamber.


EPIDEMIOLOGY


Incidence


• The incidence of pupillary block increases with age and is greater in females.


• Angle closure peaks in incidence between 55 and 70 years of age (1)[A].


Prevalence


• About 22 million people worldwide are affected with primary angle-closure glaucoma (PACG).


• About 90% of patients with angle closure have relative pupillary block as the underlying mechanism (2)[A].


• The prevalence of PACG in the European population is approximately 0.1%.


• The prevalence of PACG is higher in Asians, Eskimos (∼0.5% of population, ∼2–3% of those older than 40 years), and Inuits (1)[A].


RISK FACTORS


• Increasing age


• Asian, Eskimo, or Inuit ethnicities


• Female gender


• Hyperopia


• Spherophakia


• Lens dislocation


• Chronic anterior uveitis


• May be precipitated by topical mydriatics, miotics (rarely), systemic anticholinergics, accommodation, and dim illumination (3)[A]


Genetics


There is heritability in angle-closure glaucoma; however, specific genes have not been identified.


GENERAL PREVENTION


Laser peripheral iridotomy (LPI) is the standard treatment for prevention of angle closure in eyes with occludable angles due to pupillary block (3)[A].


PATHOPHYSIOLOGY


• Increase in resistance to aqueous flow from the posterior chamber to the anterior chamber


• The resulting increase in intraocular pressure (IOP) leads to retinal ganglion cell damage.


ETIOLOGY


• Aqueous is produced into the posterior chamber and normally flows between the posterior surface of the iris and the anterior lens capsule (in phakic eyes) or intraocular lens (in pseudophakic eyes) or hyaloid face (in aphakic eyes).


• Relative resistance to flow of aqueous from the posterior to anterior chamber is usually present; however, the resistance may increase when channel becomes more narrow or longer (e.g., posterior movement of iris insertion, anterior movement of lens, extreme miosis, increase of lens size).


• Increased pressure differential between the posterior and anterior chamber leads to convexity of iris and apposition of iris to trabecular meshwork, leading to decreased aqueous outflow and increased IOP (1)[A].


• Posterior synechiae resulting from inflammation can also lead to pupillary block.


COMMONLY ASSOCIATED CONDITIONS


• Hyperopia


• Pseudoexfoliation


• Spherophakia


• Intumescent cataract


• Nanophthalmos


• Retinopathy of prematurity


• Ciliochoroidal expansion syndromes


• Lens subluxation (e.g., Marfan’s syndrome, homocystinuria) (2)[A]


DIAGNOSIS


HISTORY


• Symptoms of eye pain, blurry vision, or haloes in vision


• Family history


• History of retinal problems


• Recent laser treatment or surgery


• Medications


PHYSICAL EXAM


• Check for an afferent pupillary defect or nonreactive pupil.


• Slit lamp exam of anterior segment: presence of anterior chamber cell or keratic precipitates, anterior chamber depth, presence of a cataract, lens position, presence of glaukomflecken, posterior synechiae, and corneal edema


• Gonioscopy. indentation with 4-mirror lens


• Early peripheral anterior synechiae (PAS) superiorly


• IOP


• Examination of the fundus looking for signs of central retinal vein occlusion, hemorrhage, optic nerve cupping, or uveal effusion


DIAGNOSTIC TESTS & INTERPRETATION


Lab


Lab tests as indicated for clinical suspicion of associated conditions


Imaging


Ultrasound biomicroscopy or optical coherence tomography in dark and light conditions may be indicated if diagnosis or etiology of apparent pupillary block is uncertain.


Diagnostic Procedures/Other


• Provocative tests for pupillary block have high false-positive and false-negative rates. These tests include the following:


– Prone darkroom test


– Pharmacologic dilation of pupil (3)[A]


Pathological Findings


• Apposition of the peripheral iris and trabecular meshwork


• Glaukomflecken—patchy anterior subcapsular opacities, foci of anterior subcapsular epithelial cell necrosis, associated with severe elevation of IOP


DIFFERENTIAL DIAGNOSIS


• Causes of open-angle glaucoma


• Neovascular or inflammatory glaucoma


• Choroidal swelling or detachment


• Medication-induced narrow angles


• Posterior segment tumor


• Aqueous misdirection syndrome


• PAS


TREATMENT


MEDICATION


First Line


• Prostaglandin agonists (e.g., latanoprost, bimatoprost, travoprost)


• Beta-blockers (e.g., timolol, levobunolol)


• Selective alpha-2 receptor agonists (e.g., brimonidine)


• Topical carbonic anhydrase inhibitors (e.g., dorzolamide, brinzolamide)


• Systemic carbonic anhydrase inhibitors (e.g., methazolamide, acetazolamide)


• Intravenous mannitol


Second Line


Miotics (e.g., pilocarpine)—may be ineffective during acute attack due to pressure-induced ischemia of their iris—may be used after IOP has been reduced to break pupillary block.


ADDITIONAL TREATMENT


General Measures


• Lower the IOP with medical treatment first, if possible.


• A paracentesis may be performed to lower the IOP.


• If the cornea remains cloudy, topical glycerin can be used to temporarily clear the cornea for laser therapy.


• Definitive management requires peripheral laser iridotomy or surgical iridectomy, or lens extraction and/or filtering procedure.


Issues for Referral


Inability to lower the IOP to a safe level using medical or laser therapy may require referral to a glaucoma specialist for surgical intervention.


Additional Therapies


Corneal indentation with a soft instrument may lower the IOP during an acute pupillary block attack by forcing aqueous into the peripheral anterior chamber, temporarily opening the chamber angle and allowing aqueous outflow (3)[A].


COMPLEMENTARY & ALTERNATIVE THERAPIES


Argon laser peripheral iridoplasty may be helpful in cases of acute pupillary block glaucoma where corneal edema, shallow anterior chamber, or marked inflammation renders an LPI unfeasible or unsafe, or in cases that are unresponsive to LPI by drawing the peripheral iris away from the anterior chamber angle and allowing aqueous flow and decrease of IOP (4)[A].


SURGERY/OTHER PROCEDURES


• In acute pupillary block angle-closure glaucoma—perform LPI if possible, and safe to do so.


• Surgical peripheral iridectomy may be performed if a laser iridotomy is not possible.


• If pressure remains elevated despite laser iridotomy or peripheral iridectomy and medications, filtering surgery (trabeculectomy) and/or cataract extraction may be necessary.


• Cataract extraction alone may be performed to lessen pupillary block in nonacute cases with little PAS or in cases of pupillary block due to lens subluxation or spherophakia.


IN-PATIENT CONSIDERATIONS


Initial Stabilization

See medical management above.


Admission Criteria


Inability to lower the IOP to a safe level acutely using either medical or laser therapy


IV Fluids


• Diamox and/or mannitol if necessary to lower IOP


• IV fluids may be necessary, if patient is vomiting actively.


Nursing


No special recommendations


Discharge Criteria


Successful lowering of IOP to a safe level


ONGOING CARE


FOLLOW-UP RECOMMENDATIONS


• Follow-up is variable and depends on the therapeutic modality used and the level of IOP at discharge.


• LPI should be performed if the anterior chamber angle is occludable in the contralateral eye at a follow-up visit.


Patient Monitoring


Sequential gonioscopy on follow-up visits should be performed to assess for progressive narrowing of the angle or PAS.


PATIENT EDUCATION


• Patients at risk of pupillary block or angle closure should be educated on the signs and symptoms of an acute angle closure attack (e.g., acute eye pain and blurry vision, seeing haloes), and counseled to seek ophthalmological attention immediately if these symptoms occur.


• Family members should be examined.


PROGNOSIS


• LPI is not reliably protective against chronic angle closure—in a study of LPI in Asian eyes, 100% had resolution of acute attack after LPI; however, 58.1% subsequently developed elevated IOP requiring treatment and 32.7% required trabeculectomy for pressure control (5)[B].


• The failure of LPI to prevent recurrent IOP elevation has been correlated with the amount of PAS present in these eyes.


• Progression of angle closure and PAS may continue after successful LPI.


COMPLICATIONS


• Glaucoma


• Loss of vision


• Acute angle closure



REFERENCES


1. Tarongoy P, Ho CL, Walton DS. Angle-closure glaucoma: The role of the lens in the pathogenesis, prevention, and treatment. Surv Ophthalmol 2009;54(2):211–225.


2. Ritch R, Chang BM, Liebmann JM. Angle closure in younger patients. Ophthalmology 2003;110(10):1880–1889.


3. Shields MB. Pupillary-block glaucoma, Chap. 12. In: Shields’ textbook of glaucoma. Allingham RR, Damji KF, Freedman S, et al. eds, 5th ed, 2005.


4. Lam DS, Lai JS, Tham CC, et al. Argon laser peripheral iridoplasty versus conventional systemic medical therapy in treatment of acute primary angle-closure glaucoma: A prospective, randomized, controlled trial. Ophthalmology 2002;109(9):1591–1596.


5. Aung T, Ang LP, Chan S, et al. Acute primary angle-closure: Long-term intraocular pressure outcome in Asian eyes. Am J Ophthalmol 2001;131(1):7–12.

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Nov 9, 2016 | Posted by in OPHTHALMOLOGY | Comments Off on Block Glaucoma
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