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Glaucoma

Summary

Glaucoma is a group of eye diseases associated with acute or chronic destruction of the optic nerve with or without concomitant increased intraocular pressure (IOP). In the US, glaucoma is the second leading cause of blindness in adults following age-related macular degeneration (AMD). The two main types are open-angle glaucoma and angle-closure glaucoma. Open-angle glaucoma accounts for 90% of all cases of glaucoma, is slowly progressive, and is initially often asymptomatic, but leads to bilateral peripheral vision loss over time. With appropriate treatment that lowers IOP (e.g., topical prostaglandins), progression can be stopped before severe damage occurs. Acute angle-closure glaucoma, on the other hand, is characterized by the sudden onset of a painful, red, and hard eye in combination with frontal headache, blurry vision, and halos appearing around lights. Immediate initiation of medical therapy (e.g., timolol eye drops and IV acetazolamide) is crucial to rapidly decrease IOP and prevent vision loss. Chronic angle-closure glaucoma manifests and is managed similarly to open-angle glaucoma.

Epidemiology

References:[1][2]

Epidemiological data refers to the US, unless otherwise specified.

Overview

Important types of glaucoma
Open-angle glaucoma Angle-closure glaucoma
Risk factors
Clinical features
  • Initially often asymptomatic
  • Bilateral, progressive visual field loss (from peripheral to central)
  • Sudden onset
    • Unilateral red, hard, and severely painful eye
    • Frontal headaches
    • Vomiting, nausea
    • Steamy cornea and blurred vision
    • Dilated, nonreactive pupil
Treatment
Overview of drugs used to treat glaucoma
Mechanism of IOP decrease Drugs Mechanism of action Adverse effects

↓ Synthesis of aqueous humor

  • No changes in vision or pupil
  • Hypotension
  • Via decrease in cAMP
Aqueous humor outflow
  • PGF2α
    • Latanoprost
    • Travaprost
    • Bimatoprost
  • Decreases resistance through uveoscleral flow

DIrty PARASites PROSper on ALPine BETonies: DIuretics, PARASympathomimetics, PROStaglandins, ALPha agonists, and BETa blockers.

References:[2]

Pathophysiology

References:[3][4]

Open-angle glaucoma

Definition

  • Open-angle glaucoma (also chronic glaucoma): generally bilateral, progressive loss of optic nerve fibers with open chamber angles (often with increased IOP), not caused by another systemic or local condition

Etiology [5]

Pathophysiology

Clinical features [5]

  • Initially often asymptomatic
  • Over time, nonspecific symptoms such as mild headaches, impaired adaptation to darkness
  • Generally bilateral, progressive visual field loss (from peripheral to central)
  • Halos around lights may occur.

Diagnostics [5]

Treatment of open-angle glaucoma [5]

  • Indicated in all patients diagnosed with open-angle glaucoma (even if asymptomatic)
  • Options include medical therapy, laser surgery, and open surgery
  • Topical prostaglandins are most effective and usually used initially; other drugs (with a different mechanism) may be added if topical prostaglandins are unsuccessful.
    • No decrease in IOP with one drug: Discontinue and replace with another drug or treatment option.
    • Partial response to one drug: Consider combination therapy with other glaucoma medications or switch to an alternative single-agent therapy.
  • Goal of therapy (target IOP): ≥ 25% decrease in pretreatment IOP

Pharmacotherapy [5][6]

The following regimen is the most commonly followed and is also effective in patients with chronic angle-closure glaucoma refractory to laser peripheral iridotomy (see ''Treatment'' in angle-closure glaucoma for further details).

Interventional therapy [5]

Procedures that lower IOP by facilitating drainage of aqueous humor

  • Laser trabeculoplasty
    • Indications
      • An alternative first-line treatment for patients with advanced disease at presentation
      • Glaucoma refractory to pharmacotherapy
      • Patients nonadherent or intolerant to pharmacotherapy
    • Procedure: use of a laser to thermally ablate the trabecular meshwork cells and improve aqueous outflow
    • Alternative: selective laser trabeculoplasty [7]
      • Pigmented cells of the trabecular meshwork are selectively targeted for thermal ablation.
      • Has a better safety profile than laser trabeculoplasty and may soon become the preferred first-line therapy for treatment-naive open-angle glaucoma [8][9]
  • Surgical trabeculectomy
    • Indications: the same as those for laser trabeculoplasty
    • Procedure: involves the creation of a tunnel (through excision of trabecular meshwork) from the anterior chamber to the subconjunctival space under a thin scleral flap
  • Tube shunt surgery
    • Indication: glaucoma refractory to trabeculectomy
    • Procedure: A small silicone tube is inserted into the anterior chamber of the eye through which aqueous humor is drained into a valved chamber that is placed on the sclera underneath the upper eyelid. [10]

Procedures that lower IOP by decreasing aqueous humor production

  • Cyclodestructive surgery
    • Indication: glaucoma refractory to other treatment options
    • Procedure: laser or cryosurgical destruction of the ciliary body

Prevention [5]

  • General screening for glaucoma is not considered cost-effective but is currently recommended in the following patient groups:

Angle-closure glaucoma

Definition [11][12][13][6]

  • Angle-closure glaucoma (also closed-angle glaucoma): sudden and sharp increase in intraocular pressure caused by an obstruction of aqueous outflow (most commonly as a result of an occlusion of the iridocorneal angle ) and associated with optic neuropathy and visual field defects [11][14]
  • Acute angle-closure glaucoma (AACG): sudden obstruction of the iridocorneal angle causing a rapid, acutely symptomatic, and vision-threatening elevation of IOP, often > 30 mm Hg [11][15]
  • Chronic angle-closure glaucoma: chronic obstruction of the iridocorneal angle with peripheral anterior synechiae resulting in an insidious and progressive rise in IOP that typically remains asymptomatic until glaucomatous optic neuropathy and irreversible visual field defects have developed [6]
  • Angle-closure suspect: normal IOP with iridotrabecular contact is seen on gonioscopy [11]

Etiology/risk factors

Pathophysiology [11][12][13][17][18]

Clinical features

Acute angle-closure glaucoma is a medical emergency, as it can cause permanent vision loss if left untreated!

Diagnostics

Approach [12][11][13][6]

Acute angle-closure glaucoma is vision-threatening and requires emergency ophthalmology evaluation as soon as the clinical diagnosis is suspected.

  • Both eyes should be evaluated even if symptoms are unilateral. [11]
  • A clinical diagnosis of angle-closure glaucoma is confirmed with the following findings:
    • Elevated IOP (> 21 mm Hg): on tonometry [13][6][14]
    • Narrowing/closure of the iridocorneal angle (i.e., iridotrabecular contact): on gonioscopy or slit-lamp examination
  • Tests to assess for glaucomatous damage should be performed in all patients.
  • Provocative testing (e.g., placing the patient in a dark room, administering mydriatics) is not recommended in acute angle-closure glaucoma because it is time-consuming, exacerbates symptoms, and is of questionable clinical significance. [11][13][6]
  • Other causes of painful red eye (especially uveitis) and/or headache with ocular pain (e.g., migraine) should be considered if diagnostic findings are inconclusive.

Do not use mydriatic drugs (e.g., atropine and epinephrine) during ophthalmologic examination in patients with acute angle-closure glaucoma! Moreover, do not cover the eye, since darkness induces mydriasis and worsens the condition! [11]

Tonometry [20][21]

  • Indication: all patients with suspected glaucoma
  • Procedure: measurement of IOP by placing a probe over the cornea .
  • Characteristic findings [11][13]

Gonioscopy [12]

  • Indications [11][13][6]
    • Gold-standard test to assess the iridocorneal angle in suspected angle-closure glaucoma
    • To distinguish between primary and secondary causes of angle closure (see ''Pathophysiology'')
  • Procedure: A special lens is placed directly on the eye and the iridocorneal angle is visualized directly using a slit lamp.
    • Typically conducted by a trained specialist
    • Should be performed on both eyes
  • Characteristic findings [11][6][13]
    • Narrowing or closure of the iridocorneal angle (i.e., ≥ 180º iridotrabecular contact)
    • Etiology of narrowed/closed iridocorneal angle may be apparent, such as: [13]

Slit-lamp examination [11][6][18]

Direct fundoscopy (with undilated pupils) [11][6][18]

Do not dilate the pupils to evaluate the fundus in suspected glaucoma!

Visual acuity [11][23]

  • Indication: all patients with glaucoma
  • Supportive findings
    • Acute angle-closure glaucoma: Corneal edema may decrease visual acuity even in the absence of glaucomatous optic neuropathy. [11]
    • Chronic angle-closure glaucoma: There may be decreased central vision or complete blindness in advanced disease. [23]

Visual field testing [6][24][13]

  • Indication: all patients with glaucoma
  • Techniques
    • Confrontation visual field exam: preferred in the ER when an ophthalmologist is not immediately available
    • Automatic static perimetry: preferred if an ophthalmologist is available
  • Characteristic findings
    • Glaucomatous visual field defects: a characteristic pattern of visual field defects as a result of glaucomatous optic neuropathy [18][24]
      • Early-stage: arcuate or double arcuate (ring) scotoma
        • Loss of peripheral vision especially of the superior and/or inferior hemifields
        • Sparing of central vision
      • Advanced stage
        • Tunnel vision: further constriction of peripheral vision
        • Total or near-total blindness: loss of peripheral and central vision with or without sparing of the temporal field

Treatment of acute angle-closure glaucoma [11][13][6][25][15]

Acute angle-closure glaucoma is an emergency and should be initially managed with IOP-decreasing medications that have a rapid onset of action. Once IOP has decreased, patients should undergo a definitive procedure as soon as possible to prevent recurrence.

General considerations

Initial pharmacotherapy

  • Indication: initiate in all patients as soon as a diagnosis of acute angle-closure glaucoma is made. [11][13][6][15]
  • Initial pharmacological regimen: There is currently no standardized recommendation for empiric management of acute angle-closure glaucoma. The following regimen may be followed with due consideration of any comorbidities. [11][13][6][15]
  • If IOP is still elevated after 30–60 minutes: The following should be given only under the guidance of an ophthalmologist. [15][25]
    • Repeat eye drops from above up to three times. [15]
    • Consider a systemic hyperosmotic agent if IOP remains high after 60 minutes of initiating therapy. [13][25]
      • In patients with nausea: IV mannitol
      • In patients without significant nausea [25]
        • Nondiabetic patients: oral glycerine [25]
        • Diabetic patients: oral isosorbide [11]
  • If IOP is decreasing: Examine for other signs of resolution of the acute attack. [13][6]
    • Symptomatic improvement (decreased pain and nausea; improvement of vision)
    • Clear cornea (resolution of corneal edema)
    • Decreased conjunctival hyperemia
    • Normal pupillary size and reaction

Urgent interventional therapy

Topical pilocarpine becomes effective only once IOP decreases to < 40 mm Hg.

Acute management checklist for acute angle-closure glaucoma [11][6][30]

  • Emergency ophthalmology consult
  • Place patient in a supine position.
  • Initiate pharmacotherapy as soon as the diagnosis is made.
  • Consider hyperosmotic pharmacotherapy if initial treatment is unsuccessful.
  • Supportive care, as needed
  • Admit patient or transfer to a hospital with ophthalmology department capable of performing LPI.

Treatment of chronic primary angle-closure glaucoma [11][12][6]

Chronic angle-closure glaucoma with pupillary block should be initially managed with laser surgery (e.g., peripheral iridotomy) or open surgery (iridectomy) to prevent the progression of glaucomatous optic neuropathy and consequent visual field loss. Long-term pharmacotherapy is required if IOP elevation is refractory to the intervention or in patients without pupillary block.

Interventional therapy [11][12][13][6]

Acute angle-closure glaucoma and chronic primary angle-closure with pupillary block

  • Laser peripheral iridotomy (LPI)
    • Indications [6]
    • Procedure: the creation of a hole in the peripheral iris to allow aqueous humor to bypass the pupillary block using a laser (preferably neodymium:YAG) [6]
    • Disadvantages [32][33]
      • Risk of closure of the iridotomy
      • Post-operative IOP
      • Laser burn
      • Transient blurred vision
      • Progression to cataract formation
  • Laser peripheral iridoplasty (gonioplasty)
    • Indication: persistently elevated IOP despite a patent LPI [6]
    • Procedure: creation of burn contractures in the peripheral iris with an argon laser to pull the peripheral iris away from the iridocorneal angle
  • Surgical peripheral iridectomy [11][14][31]
    • Indication: an alternative to LPI in patients with acute/chronic angle-closure glaucoma with pupillary block [11][31]
    • Procedure: the surgical excision of a small amount of iris tissue to allow for aqueous flow
    • Disadvantages
      • Costly
      • Postoperative recovery period
      • Surgical complications

Chronic primary angle-closure glaucoma without pupillary block [6]

Secondary angle-closure glaucoma [6][31]