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Glaucoma

Jonathan A. Barnett

Background

  • Glaucoma is a disease of the optic nerve that follows a characteristic pattern of optic nerve fiber degeneration.

  • High intraocular pressure (IOP) is believed to be the main etiology of the disease.

  • While the “normal” IOP range is between 11 and 21 mmHg, there are individuals who have a pressure above 21 that do NOT develop glaucoma. Conversely, there are individuals who have a pressure in the normal range that DO develop glaucoma (= Normal Tension Glaucoma).

  • Aqueous humor fills the anterior chamber and drains through a sieve-like structure called the trabecular meshwork (TM), located in the angle between the iris and the cornea. After passing through TM, aqueous drains into the eye’s venous system. Impediment to aqueous flow will cause elevated IOP.

Presentation

  • All glaucomas generally cause progressive peripheral visual field loss that ultimately encroaches on central fixation and leads to irreversible blindness if left untreated.

  • A glaucomatous optic nerve is often described as “cupped”

  • Presents in an acute or chronic fashion:

  • Acute Angle-Closure Glaucoma

    • The iridocorneal angle rapidly closes, blocking aqueous drainage and causing a sudden rise in IOP (usually >40mmHg).

    • Symptoms and Signs: intense eye or orbital pain, headache, nausea/vomiting, blurred vision, halos around lights, fixed and mid-dilated pupil, rock-hard eye, conjunctival redness, cloudy cornea.

    • Usually unilateral, but occasionally can be bilateral.

    • Classic trigger is a pupil-dilating factor (e.g., dark environment or anticholinergic medications) in a person with anatomically narrow angles.

    • If IOP is not lowered within hours, permanent optic nerve damage and vision loss will likely occur.

  • Primary Open Angle Glaucoma (POAG)

    • The iridocorneal angle is open, but due to inadequately functioning TM (or other mechanism) aqueous does not drain properly and IOP is chronically elevated.

    • POAG is often painless and without noticeable vision changes in the early stage of disease. Individuals can go undiagnosed for years, sitting at an IOP of say 30mmHg, without being aware they are losing vision until the vision loss is severe.

    • POAG is the most common glaucoma in the US. When a patient says they have a history of glaucoma, they probably have POAG.

Evaluation and Management

  • Primary Open Angle:

  • Continue the patient’s home glaucoma drops; caution if they develop a medical condition that results in a contraindication (See table below)

  • No need to officially place an Ophthalmology consult to order a patient’s home glaucoma drops; feel free to page Ophthalmology if you have questions.

  • Pro tip: Often patients will remember the cap color of the drops they take but not the names!

Name (brand) Cap color Class Dosing Possible side effects Relative contraindications
Timolol (Timoptic) Yellow Nonselective beta-blocker BID Bradycardia, bronchospasm, hypotension Heart conditions (CHF, heart block), asthma/COPD

Latanoprost

(Xalatan)

 Teal Prostaglandin analogue QHS Flulike symptoms, joint pains Pregnancy (category C), uveitis

Brimonidine

(Alphagan)

 Purple Alpha-2 agonist BID-TID Allergic conjunctivitis, CNS depression, bradycardia Infants and young children

Dorzolamide

(Trusopt)

 Orange Carbonic anhydrase inhibitor BID Acidosis, hypokalemia, malaise, GI upset, metallic taste Renal insufficiency, Hepatic cirrhosis, Sickle cell disease, caution when using with other K-wasting drugs

Acetazolamide

(Diamox) PO

 PO tablet Carbonic anhydrase inhibitor

250mg

BID-QID

 Same as dorzolamide, but side effects more likely to occur given PO Same as dorzolamide, but side effects more likely to occur given PO

Cosopt (Blue cap) = dorzolamide + timolol

Combigan (Purple cap) = brimonidine + timolol

  • Acute Angle Closure:

  • If suspect acute angle closure given the signs described above, consult Ophthalmology ASAP.

  • The goal is to lower the IOP ASAP. Target is \<30mmHg.

  • Administer frequent rotating rounds of all the IOP-lowering drops: 1 drop of Cosopt (then wait 5 minutes), followed by Brimonidine (then wait 5 minutes), followed by Latanoprost (then wait 5 minutes)--then keep repeating the cycle until the IOP goes down.

  • Concurrently, administer one dose of IV Diamox 500mg if not contraindicated (e.g., renal insufficiency or hepatic cirrhosis). Ophthalmology will recheck the IOP every hour or so to ensure that the IOP is responding (usually it does).

  • If the IOP does not respond, patient will need a bedside AC tap to offload aqueous and lower the pressure.

  • Patient should ultimately get a Laser Peripheral Iridotomy (LPI) to avoid future angle-closure attacks, which is typically performed as an outpatient procedure.