Glaucoma

Glaucoma refers to a group of eye diseases that can damage the optic nerve. This nerve is essential for transmitting visual information from the eye to the brain. If left untreated, glaucoma can lead to significant vision loss. It is often called the "silent thief of sight." This nickname exists because vision loss usually occurs slowly over a long period.

To understand the disease, one must understand intraocular pressure, or IOP. Inside the eye, a liquid called aqueous humor is produced by the ciliary body. This fluid helps the eye maintain its shape and provides necessary nutrients. Normally, the aqueous humor drains through a structure called the trabecular meshwork. This drainage allows the fluid to flow into the scleral venous sinus, also known as Schlemm's canal.

There are two primary types of glaucoma: open-angle and closed-angle. In open-angle glaucoma, the drainage through the trabecular meshwork is impeded or slowed. This causes the aqueous humor to accumulate in the anterior chamber. This accumulation leads to a chronic, painless increase in intraocular pressure. This elevated pressure can reduce vascular perfusion in the vitreous chamber. It may also damage the optic nerve and peripheral glial tissues.

Closed-angle glaucoma is a much more sudden condition. In this type, the iridocorneal angle becomes narrowed or completely closed. This often happens because the iris moves forward and blocks the trabecular meshwork. This blockage causes a rapid and acute increase in intraocular pressure. This type is a medical emergency. It can cause intense eye pain, blurred vision, nausea, vomiting, and seeing halos around lights.

Scientists have several theories regarding how high pressure damages the optic nerve. The biomechanical theory suggests that retinal ganglion-cell axons are physically damaged. This damage occurs as they pass through pores at the lamina cribrosa. The vascular theory suggests that a decreased blood supply causes nerve damage. This might result from high pressure or systemic issues like atherosclerosis. A third theory is the primary neurodegeneration theory. This theory suggests a direct process causes the degeneration of the optic nerve head.

Glaucoma affects millions of people across the globe. In 2013, the global prevalence was estimated at 3.54%, affecting 64.3 million people. By 2040, this number is projected to reach 111.82 million people worldwide. In the United States, an estimated 4.22 million people had glaucoma in 2022. This condition is a leading cause of blindness for African Americans, Hispanic Americans, and Asians. For example, Black adults in the U.S. are about twice as likely to be affected as White adults.

Several risk factors can increase a person's susceptibility to glaucoma. Increasing age is a major factor, as incidence rises with age. Having a family history of the disease also increases risk. For instance, the risk is two to four times higher for those with a sibling with glaucoma. Certain genetic mutations, such as in the MYOC or OPA1 genes, are also linked to the disease. Other factors include the use of steroid medications or ocular trauma.

Early detection is the best way to manage the condition. Regular eye examinations are essential, especially for people over age 40. Doctors look for changes in the optic nerve, such as an increased cup-to-disc ratio. If caught early, treatment can slow or stop the progression of vision loss. Common treatments include prescription eye drops, laser treatment, or surgery. The primary goal of all these treatments is to decrease the intraocular pressure.