Glaucoma

Glaucoma refers to a set of eye conditions that harm the optic nerve, the structure responsible for sending visual signals from the eye to the brain. Without treatment, it can result in vision loss, and it is often nicknamed the "silent thief of sight" because this loss tends to happen gradually over many years. A key risk factor is elevated intraocular pressure (IOP), or increased pressure inside the eye. The term itself comes from the Ancient Greek word *glaukós*, meaning 'gleaming, blue-green, gray.'

The two most common forms are open-angle glaucoma and closed-angle glaucoma. Inside the eye, a fluid called aqueous humor, made by the ciliary body, helps maintain the eye’s shape and supply nutrients. Normally, this fluid drains through the trabecular meshwork. In open-angle glaucoma, drainage is blocked, causing aqueous humor to build up in the anterior chamber and raise eye pressure. This higher pressure can reduce blood flow in the vitreous chamber and damage the optic nerve and surrounding glial tissues. In closed-angle glaucoma, drainage is suddenly blocked, leading to a rapid spike in intraocular pressure. This can cause intense eye pain, blurred vision, and nausea, and it is a medical emergency requiring immediate care.

If caught early, the progression of glaucoma can be slowed or halted. Regular eye exams are crucial for early detection, especially for people over 40 or those with a family history of the condition. Treatment often involves prescription eye drops, medication, laser therapy, or surgery, all aimed at lowering eye pressure.

Glaucoma is a major cause of blindness among African Americans, Hispanic Americans, and Asians. Its prevalence increases with age, affecting more than 8% of Americans over 80, and closed-angle glaucoma is more common in women.

**Epidemiology**

In 2013, for people aged 40 to 80, the global prevalence of glaucoma was estimated at 3.54%, affecting 64.3 million individuals worldwide. That same year, 2.97 million people in North America had open-angle glaucoma. By 2040, the number of people with all types of glaucoma worldwide is projected to reach 111.82 million, with 4.72 million in North America.

Globally, glaucoma is the second most common cause of blindness, after cataracts. In the United States, it is a leading cause of blindness for African Americans, who have higher rates of primary open-angle glaucoma, and for Hispanic Americans. Bilateral vision loss can impair mobility and interfere with driving. A 2009 meta-analysis found that people with primary open-angle glaucoma do not have higher mortality rates or an increased risk of cardiovascular death. A 2024 *JAMA Ophthalmology* article, based on a meta-analysis, reported that in 2022, an estimated 4.22 million people in the U.S. had glaucoma, with 1.49 million experiencing vision impairment from it. Black adults were about twice as likely to have glaucoma as White adults. Glaucoma prevalence was 1.62% among those 18 and older and 2.56% among those 40 and older; vision-affecting glaucoma occurred in 0.57% and 0.91% of these age groups, respectively.

**Signs and Symptoms**

Open-angle glaucoma often has no symptoms early on but can gradually cause vision problems. It typically starts with peripheral vision loss, then central vision loss as it advances, though it can sometimes present as central vision loss or patchy areas of vision loss. An eye exam may reveal optic nerve damage, such as an increased cup-to-disc ratio. Acute angle-closure glaucoma is a medical emergency due to the risk of permanent vision loss. It is marked by sudden eye pain, seeing halos around lights, red eye, very high intraocular pressure, nausea and vomiting, and sudden vision decrease. On examination, it may show corneal edema, engorged conjunctival vessels, and a fixed, dilated pupil. Opaque specks in the lens, called *glaukomflecken* (German for "glaucoma-specks"), can also occur.

**Risk Factors**

Anyone can develop glaucoma, but certain factors raise the risk: increasing age, high intraocular pressure, a family history of glaucoma, and use of steroid medications.

**Ocular Hypertension**

Elevated intraocular pressure is a major risk factor for glaucoma, but only about 10–70% of people with primary open-angle glaucoma (depending on ethnic group) actually have high eye pressure. Ocular hypertension—IOP above the traditional threshold of 21 mmHg (28 hPa) or even above 24 mmHg (32 hPa)—is not necessarily a disease, but it increases the risk of developing glaucoma. A study of 1,636 people aged 40–80 with IOP above 24 mmHg in at least one eye but no signs of eye damage found that after five years, 9.5% of untreated participants and 4.4% of treated participants developed glaucomatous symptoms. This means only about one in ten untreated people with elevated IOP will develop such symptoms in that period. Given these results, whether to treat everyone with elevated IOP as a preventive measure is debated. As of 2018, most ophthalmologists favored treating those with additional risk factors.