Glaucoma: Clinical sciences

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Introduction0:00–1:11

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.

Angle-Closure Glaucoma1:11–3:28

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!
Okay, management of angle-closure glaucoma involves reducing IOP. The first line medical therapy includes medications to either suppress production or increase outflow of the aqueous humor.

Treatment3:28–4:57

These include topical prostaglandin analogs like latanoprost; beta-blockers like timolol; alpha 2-agonists like apraclonidine; and miotic agents, like pilocarpine; as well as IV agents such as acetazolamide, a carbonic anhydrase inhibitor; and IV mannitol, an osmotic diuretic.
As far as procedures go, a laser peripheral iridotomy can be performed, where a tiny hole is made in the iris to create an alternative pathway for aqueous humor flow.
This will immediately lower the IOP and prevent future angle-closure episodes. If the iridotomy doesn’t control the IOP, an alternative option is an iridectomy, where a small section of the peripheral iris is excised.
Here’s another clinical pearl! In angle-closure glaucoma, the untreated opposite eye shares the same predisposing factors as the affected eye.
In fact, the untreated eye has a forty to eighty percent chance of developing angle-closure glaucoma within five to ten years!
So if you diagnose angle-closure glaucoma in one eye, make sure your patient also undergoes laser peripheral iridotomy on the unaffected eye!
Alright, now if angle-closure glaucoma is not present, your next step is to assess for open-angle glaucoma. Your patient may report glare, difficulty with low contrast environments like a dim movie theater, or difficulty adjusting to extreme lighting changes.

Open-Angle Glaucoma4:57–6:28

They may also have risk factors for glaucoma, such as family history of it, biological female sex, and older age, as well as a history of hypertension, type 2 diabetes mellitus, migraines, or ocular trauma or surgery.
The fundoscopic exam will show cupping of the optic disc as damage to the nerve progresses. This creates an enlarged cup to disc ratio greater than 0.5.
You might even see optic disc hemorrhages! Also, tonometry will show an IOP greater than 21 millimeters of mercury.
With these findings, suspect open-angle glaucoma and make a referral to the ophthalmology team. A diagnosis of open-angle glaucoma is confirmed if gonioscopy measures an anterior chamber angle of 21 to 45 degrees.
And here’s a clinical pearl! Open-angle glaucoma is the most common type of glaucoma worldwide and is the most frequently occurring cause of irreversible blindness.
Because it can present as painless, progressive vision loss it may often go undetected until there’s marked optic nerve atrophy!
Now, moving on to treatment! Just like with angle-closure glaucoma, management for open-angle glaucoma focuses on reducing IOP.

Treatment6:28–7:46

Medications for reducing IOP include topical prostaglandin analogs, beta blockers, alpha-2 agonists, and miotic agents. Rho-kinase inhibitors and nitric oxide donating prostaglandin analogs may also be used.
The target IOP is the level at which further optic neuropathy is unlikely to occur, which is generally greater than or equal to 25 to 30 percent below the patient’s initial IOP.
Patients should be reassessed at regular intervals for progression of visual field deficits or worsening optic disc changes.
If medical therapy is unsuccessful, or if your patient doesn’t tolerate topical agents, a laser trabeculoplasty can be performed, which uses a laser to open the trabecular network to promote fluid drainage.
This reduces IOP and may even eliminate the need for topical agents! Finally, if these therapies fail to maintain target pressures, minimally invasive glaucoma surgery techniques such as a transluminal trabeculotomy or placement of an aqueous shunt can be considered.

Review7:46–8:21

Alright, as a quick recap... Angle-closure glaucoma and open-angle glaucoma are two types of glaucoma characterized by damage to the optic nerve and progressive vision loss.
Patients with angle-closure glaucoma should be treated emergently with medications, laser peripheral iridotomy, or iridectomy to prevent vision loss.
Meanwhile, open-angle glaucoma is treated with similar medications, as well as laser trabeculoplasty or minimally invasive glaucoma surgery techniques, to achieve target IOP and prevent progression of the
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