Glaucoma is a type of eye condition that causes damage to the optic nerve. This leads to gradual, irreversible vision loss if not treated early. The two well-known types of glaucoma are open-angle glaucoma and angle-closure (closed-angle) glaucoma. Despite the fact that both affect the optic nerve and can cause blindness, their causes, progression, symptoms, and treatment strategies vary. Understanding these differences will help you recognise early warning signs and seek prompt medical attention to protect your vision.
Open-Angle Glaucoma
Open-angle glaucoma, also commonly known as primary open-angle glaucoma. It accounts for approximately 90% of all glaucoma cases worldwide. It is often referred to as the “silent thief of sight” because it develops slowly and painlessly, with no noticeable symptoms in its early stages.
In open-angle glaucoma, the drainage angle created by the cornea and iris remains open, but the eye’s drainage canals lose their efficiency over time. This leads to a slow buildup of intraocular pressure (IOP), which damages the optic nerve. Elevated IOP is the most significant risk factor for open-angle glaucoma, although some individuals may develop this condition even with normal eye pressure, known as normal-tension glaucoma.
Risk factors for open-angle glaucoma include a family history of glaucoma, advanced age, ethnicity-related factors, diabetes, and long-term steroid use. The disease is asymptomatic until significant vision loss occurs; daily eye examinations are essential, particularly for those at higher risk.
Typically, vision loss from open-angle glaucoma begins with the peripheral (side) vision, progressing toward the central vision if left untreated. Patients may not notice the changes until the disease has advanced, leading to tunnel vision or blindness in severe cases.
Diagnosis is made through comprehensive eye exams that include measuring IOP, visualising the optic nerve using imaging techniques, testing the field of vision, and evaluating the drainage angle through gonioscopy. Once diagnosed, treatment typically involves lowering eye pressure using prescription eye drops, oral medications, laser therapy or other related procedures to prevent further damage to the optic nerve.
Closed-Angle Glaucoma
Closed-angle glaucoma, also known as angle-closure glaucoma or narrow-angle glaucoma, is rare but can cause a sudden, severe increase in intraocular pressure, resulting in a medical emergency. Unlike open-angle glaucoma, this condition develops when the drainage angle between the cornea and iris becomes blocked, preventing fluid from draining properly from the eye.
This type of glaucoma can occur suddenly (acute angle-closure glaucoma) or develop gradually (chronic angle-closure glaucoma). Acute angle-closure glaucoma requires immediate medical attention to prevent permanent vision loss.
During a particularly serious attack, symptoms can appear suddenly. It may include severe eye pain, sudden blurred vision, headache, nausea, vomiting, seeing halos around lights, and eye redness. The sudden rise in IOP can rapidly damage the optic nerve, making prompt treatment critical to preserve vision.
Risk factors for closed-angle glaucoma include older age, ethnicity-related factors, gender, farsightedness (hyperopia), and a family history of glaucoma. Specific medications, like those used to treat allergies, depression, or gastrointestinal issues, may trigger an attack in individuals predisposed to angle-closure glaucoma.
Diagnosis is established through comprehensive eye examinations, including keeping track of IOP, examining the optic nerve, performing visual field testing, and conducting gonioscopy to assess the angle structure. Initial treatment typically includes medications to lower eye pressure, followed by a laser procedure called laser peripheral iridotomy, which creates a small hole in the iris to improve fluid drainage and prevent future attacks.
The Key Differences
While both open-angle and angle-closure glaucoma involve damage to the optic nerve and increased intraocular pressure, their causes, symptoms, and treatment urgency differ significantly:
- Onset and Progression:
Open-angle glaucoma develops slowly and painlessly. It leads to gradual peripheral vision loss. On the other hand, angle-closure glaucoma can occur suddenly. It causes rapid symptoms that require emergency care. - Drainage Angle Status:
In open-angle glaucoma, the drainage angle stays open. However, fluid drains inefficiently, leading to a slow pressure buildup. In closed-angle glaucoma, the angle is blocked, preventing fluid outflow and causing a sudden spike in pressure. - Symptoms:
Open-angle glaucoma is asymptomatic in early stages, while angle-closure glaucoma often presents with sudden eye pain, headache, blurred vision, nausea, vomiting, and halos around lights during an acute attack. - Risk Factors:
Open-angle glaucoma is more common in individuals with a family history, certain ethnicities, and old age. Angle-closure glaucoma is more common in people of Asian descent, women, those with hyperopia, and the elderly. - Treatment Urgency:
Open-angle glaucoma requires continuous management to lower eye pressure and prevent further optic nerve damage. Angle-closure glaucoma, especially during acute attacks, is an ophthalmic emergency requiring immediate treatment to prevent permanent vision loss. - Vision Loss Pattern:
Loss of vision in open-angle glaucoma typically starts with peripheral vision, while untreated acute angle-closure glaucoma can lead to rapid, severe vision loss. - Management:
The two types of glaucoma are managed by reducing intraocular pressure using medications, laser therapy, or surgery, but angle-closure glaucoma may require urgent laser procedures such as peripheral iridotomy to alleviate the blockage quickly.
Understanding these differences is crucial, as prompt detection and timely intervention can help preserve vision in patients with glaucoma.
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Conclusion
Glaucoma has maintained its position as one of the leading causes of permanent blindness globally. However, with early detection, appropriate treatment, and regular monitoring, vision loss can often be prevented or slowed. Open-angle glaucoma and angle-closure glaucoma, though both damaging to the optic nerve, differ significantly in their mechanisms, symptoms, and urgency of treatment.
If you experience any risk factors for either type of glaucoma or notice any changes in your vision, schedule a comprehensive eye examination with your ophthalmologist. Early diagnosis is the key to managing glaucoma effectively and preserving your sight.
Keep in mind that vision once lost to glaucoma cannot be restored, but with vigilant monitoring, adherence to treatment, and lifestyle adjustments such as maintaining a healthy diet, exercising regularly, and avoiding activities that may increase eye pressure, you can take charge of your eye health.
