Glaucoma: Clinical sciences

Glaucoma is a group of ocular conditions characterized by optic neuropathy, which is usually associated with increased intraocular pressure, or IOP for short, due to impaired drainage of fluid, called the aqueous humor.

Normally, most of the aqueous humor flows through a drainage pathway called the anterior chamber angle between the iris and the cornea. When this pathway becomes partially or completely blocked, the fluid can’t easily drain out, which increases IOP. The increased IOP causes damage to the optic nerve, resulting in progressive vision loss and potential blindness.

Now, glaucoma is categorized as either angle-closure glaucoma, also known as closed-angle glaucoma, or open-angle glaucoma.

If glaucoma is caused by an underlying identifiable medical condition, like injury to the eye or inflammation, it’s called secondary glaucoma; but the most common form is primary glaucoma, which can’t be attributed to any known medical condition.

If a patient presents with a chief concern suggesting glaucoma, first obtain a focused history and physical examination. Your patient will typically report loss of peripheral vision and possibly blurred vision; while a physical exam will reveal peripheral visual field impairment, decreased visual acuity, and optic nerve edema on fundoscopy.

If your patient presents with these findings, your next step is to assess for angle-closure glaucoma. Now, angle-closure glaucoma can be chronic, where the obstruction of aqueous humor outflow progresses slowly over time. Once the outflow is completely blocked, it’s called acute angle-closure glaucoma, which is a vision-threatening emergency!

These patients are generally 40 years of age or older and report severe unilateral eye pain and headache with nausea. They may even see halos around lights or have a family history of angle-closure glaucoma. A physical exam will show a dilated unreactive pupil; a hazy cornea; and conjunctival injection, commonly referred to as blood shot eyes, which is redness due to dilation of the conjunctival blood vessels.

With these findings, you should suspect angle-closure glaucoma and make an emergent referral to the ophthalmology team. A gonioscopy exam that measures an anterior chamber angle of 20 degrees or less confirms the diagnosis of angle-closure glaucoma!

Here’s a high-yield fact! Keep in mind that the smaller the angle between the iris and cornea, the greater the threat to the patient’s vision!

Now, here’s a clinical pearl! While not required for the diagnosis of angle-closure glaucoma, fundoscopy, slit lamp examination, and tonometry are also helpful tools. Both fundoscopy and slit lamp examination will show a shallow anterior chamber and an enlarged optic cup, which is the area in the center of the optic disc that increases in size as optic nerve fibers are lost; whereas tonometry will reveal an IOP greater than 21 millimeters of mercury, often ranging between 50 to 80 millimeters of mercury!