Definition

Glaucoma refers to a group of eye disorders characterized by an impairment in the visual field due to the loss of nerve cells in the eye. This condition is progressive, meaning it worsens over time, and is the leading cause of irreversible blindness globally. Approximately 3 million people worldwide suffer from blindness due to glaucoma, particularly primary open-angle glaucoma, with 2 million new cases diagnosed each year.

Causes

The eye anterior contains a fluid-filled space known as the aqueous humor, which is produced by the ciliary body, a structure that supports the eye lens. This transparent fluid is nutrient-rich, benefiting various parts of the eye that lack a direct blood supply. It also plays a crucial role in maintaining stable intraocular pressure and the round shape of the eyeball. The aqueous humor is drained through the trabecular meshwork, located near the iris. When the fluid's drainage is obstructed, intraocular pressure increases, a significant risk factor for glaucoma.

Elevated intraocular pressure can contribute to optic nerve damage, though other factors, such as hypoxia, neurotoxic substances, and impaired cellular repair mechanisms, also play a role. This damage occurs in the retina, the eye's light-sensitive layer, leading to the characteristic visual field constriction associated with chronic glaucoma.

Glaucoma is categorized into several types, including open-angle, closed-angle, normal-tension, and secondary glaucoma. The distinction between open-angle and closed-angle glaucoma is based on the angle between the iris and cornea. A narrow angle can obstruct aqueous humor outflow, leading to closed-angle glaucoma, whereas open-angle glaucoma involves trabecular meshwork damage without angle narrowing.

While increased intraocular pressure is common in glaucoma, normal-tension glaucoma (NTG) occurs when optic nerve damage persists despite normal intraocular pressure. If glaucoma arises from an external cause, such as medication use, it is classified as secondary glaucoma.

Risk Factors

The risk factors for chronic glaucoma vary depending on the type. For open-angle glaucoma, key risk factors include elevated intraocular pressure, advanced age, visual impairment, and a family history of the condition. The likelihood of developing open-angle glaucoma increases with age, and nearsightedness requiring strong corrective lenses is a notable visual risk factor. A genetic predisposition is evident, as a family history involving parents or siblings with open-angle glaucoma significantly elevates an individual's risk.

For closed-angle glaucoma, risk factors include age over 40, female sex, a narrow anterior chamber angle, and visual disturbances such as hyperopia, particularly associated with a shorter eyeball length. Certain medications, such as those used for asthma, depression, flu, epilepsy, and muscle relaxation, can also precipitate closed-angle in susceptible individuals.

Symptoms

Chronic glaucoma typically remains asymptomatic until significant nerve damage has occurred. In advanced stages of the condition, patients may experience frequent tripping due to an inability to detect objects directly in front of them, as well as a narrowing of vision, often described as tunnel vision. In contrast, closed-angle glaucoma may present with more acute symptoms, including sudden onset eye pain, redness, and headaches. Other common complaints in angle-closure glaucoma include blurred vision and the appearance of halos that disrupt normal sight.

Diagnosis

Diagnosing chronic glaucoma involves a thorough patient history, where the doctor may inquire about the use of certain medications, such as those for asthma, depression, or anti-inflammatory drugs like steroids. The doctor may also inquire if there was a prior history of eye surgery or trauma, which are recognized risk factors for glaucoma.

Diagnostic procedures may include gonioscopy to examine the anterior chamber angle, fundoscopy to assess the optic nerve, and slit-lamp examination to inspect the front of the eye. Intraocular pressure can be measured using Goldmann applanation tonometry.

Additionally, a visual field test with perimetry may be conducted to detect any constriction of the visual field.

Management

The primary goal of chronic glaucoma management is to slow the progression of vision loss. Unfortunately, any vision that has already been lost cannot be restored. Treatment generally focuses on lowering intraocular pressure, typically through the use of medications, which can be administered as eye drops or taken orally.

Laser surgery is another therapeutic option for chronic glaucoma, aimed at either widening the anterior chamber angle or repairing the trabecular meshwork. Non-laser surgical interventions may also be considered as part of glaucoma treatment.

Complications

Complications from glaucoma include a progressive narrowing of the visual field, which can eventually lead to blindness due to optic nerve damage. Additionally, glaucoma can result in corneal damage, as this transparent layer covers the iris. In cases of blindness resulting from glaucoma, the eyeball's internal contents may become disorganized, rendering the eye structure nonfunctional. This leads to a significant drop in intraocular pressure, causing the eye to shrink and potentially be recognized by the body as a foreign object, prompting an immune response.

Prevention

It is advisable to undergo regular eye examinations after the age of 40 to monitor for increased intraocular pressure, a key risk factor for glaucoma. Early intervention to lower intraocular pressure has been proven to prevent glaucoma in individuals with elevated eye pressure but without visual impairment.

While the progression of chronic glaucoma cannot be entirely prevented, it can be slowed. Individuals with a family history of glaucoma, such as a parent or sibling, should consider visiting a doctor to determine their risk. If glaucoma is diagnosed, appropriate medication can be prescribed to slow the deterioration of vision.

When to See a Doctor?

Immediate medical attention should be sought if these symptoms occur: 

• Extreme eye pain
• Eye redness
• Watery eyes
• Headaches;
• or vision disturbances

These may indicate acute glaucoma, a potential complication of chronic glaucoma, which can lead to optic nerve damage and blindness if not promptly treated.

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