Glaucoma harms the optic nerve and can lead to blindness if untreated. There are two main types of glaucoma, open-angle and closed-angle, each with distinct characteristics and treatment approaches.
This blog will explore the differences between open-angle and closed-angle glaucoma to help you better understand these conditions and their management.
What is Glaucoma?
Glaucoma encompasses various eye conditions that harm the optic nerve, essential for vision. The optic nerve carries visual data to the brain through retinal ganglion cells (RGCs) with axons.
In glaucoma, RGCs and axons are gradually lost in the optic nerve, leading to a decline in peripheral vision. Eventually, central vision may also be affected. While the exact cause remains elusive, it’s linked to elevated intraocular pressure (IOP).
Understanding the Difference Between Open-angle glaucoma and Closed-angle glaucoma
Glaucoma presents in two primary forms: Open-angle and Closed-angle glaucoma.
Open-Angle Glaucoma (OAG)
The most common type, open-angle glaucoma, features an open drainage angle, causing gradual optic nerve damage.
Its exact cause is unknown, but it’s linked to poor aqueous humor drainage or insufficient blood supply to the optic nerve.
It is painless, affects both eyes and may lead to significant vision loss before detection.
Symptoms of Open-Angle Glaucoma
- Gradual loss of peripheral vision
- Tunnel vision in advanced stages
- No noticeable symptoms in the early stages
Diagnosis of Open-Angle Glaucoma
Eye doctors may employ various diagnostic tests to aid in diagnosing and monitoring open-angle glaucoma (OAG). These tests include:
1. Visual field test: This assessment helps identify any loss of peripheral vision, a common symptom of OAG.
2. Eye pressure test: Using specialized equipment, eye doctors can measure intraocular pressure (IOP), a key indicator of glaucoma risk. This may involve a device that emits a gentle puff of air onto the eye or makes direct contact with the eye to obtain IOP readings.
3. Exclusionary diagnostics: Before confirming an OAG diagnosis, eye doctors must eliminate other potential causes of symptoms.
This process involves ruling out alternative forms of glaucoma and other eye conditions that can manifest similar symptoms, such as optic nerve diseases, retinal disorders, and central nervous system disorders.
| Routine eye checkup Regular eye exams are vital for detecting Open-Angle Glaucoma (OAG) early, as this condition frequently advances without apparent symptoms.These exams allow eye care professionals to measure intraocular pressure, inspect the optic nerve, and check visual fields, which are crucial for diagnosing OAG early. Timely detection through regular eye exams enables effective management and helps prevent vision loss. Thus, regular eye check-ups are vital to maintaining eye health and catching OAG before it progresses. |
Closed -Angle Glaucoma (CAG)
Closed-angle glaucoma, less common but a medical emergency, arises when the drainage angle closes. It usually affects one eye and can lead to acute episodes. Structural eye anatomy often contributes to angle blockages, especially with a shallower angle between the iris and cornea.
Symptoms of Closed-Angle Glaucoma
- Sudden, severe eye pain
- Blurred or decreased vision
- Halos around lights
- Nausea and vomiting
- Redness in the eye
- Headache
Acute closed-angle glaucoma
Eye pressure measurement is also crucial in acute closed-angle glaucoma (CAG) cases. Although this condition typically impacts only one eye, assessing the unaffected eye can unveil characteristics that may elevate the risk of developing CAG in that eye. Factors such as dim lighting conditions, like those in a movie theater, can trigger an acute attack of closed-angle glaucoma.
Open-angle glaucoma vs closed-angle glaucoma
| Feature | Open-Angle Glaucoma (OAG) | Closed-Angle Glaucoma (CAG) |
| Prevalence | Most common type of glaucoma | Less common than OAG |
| Angle Between Iris and Cornea | The drainage angle remains open | The drainage angle is closed or obstructed |
| Onset | Gradual onset | Sudden, acute onset |
| Symptoms | Often asymptomatic until significant vision loss occurs | Severe eye pain, nausea, blurred vision, halos around lights |
| Affected Eyes | Typically affects both eyes | Usually affects one eye, but the other eye is at high risk |
| Vision Loss | Progressive peripheral vision loss | Rapid vision loss if not treated promptly |
| Emergency | Not typically an emergency | Medical emergency |
| Causes | Inefficient aqueous humor drainage, poor blood supply to optic nerve | Blockage due to structural anatomy of the eye, shallow angle |
| Treatment | Eye drops, laser treatment, surgery | Immediate medical treatment, laser iridectomy, cataract surgery |
| Prognosis | Vision loss can be slowed with treatment | Urgent treatment is necessary to prevent permanent vision loss. |
This table summarizes the critical differences between open and closed-angle glaucoma, highlighting their characteristics, symptoms, and treatment approaches.
Which type is worse?
Closed-angle glaucoma (CAG) can rapidly lead to vision loss within one day of symptom onset, making it particularly severe.
However, it is less common than open-angle glaucoma (OAG), affecting a larger population. By 2040, experts estimate that approximately 111.8 million individuals worldwide will have OAG.
Treatment
Here are possible treatment options for OAG and CAG.
Open-Angle Glaucoma
While there’s no cure for OAG, treatments aim to slow optic nerve damage and preserve vision. Before treatment, eye doctors consider factors like the type of glaucoma, medical history, and severity of the condition to set a target intraocular pressure (IOP).
Treatment options for OAG include:
1- Eye drops
- Prostaglandin analogs (e.g., latanoprost)
- Adrenergic agents (e.g., brimonidine)
- Beta-blockers (e.g., timolol)
- Carbonic anhydrase inhibitor (e.g., dorzolamide)
- Cholinergic agents (e.g., pilocarpine)
- Rho kinase inhibitors (e.g., ripasudil, netarsudil)
2- Laser treatment
- Laser trabeculoplasty
- Diode laser cyclophotocoagulation
3- Surgery
- Trabeculoplasty
- Glaucoma drainage device
- Non-penetrating glaucoma surgery
- Minimally invasive glaucoma surgery
Closed-Angle glaucoma
Emergency treatment for CAG aims to reduce eye pressure. Options may include:
- (IV) Intravenous acetazolamide to block aqueous humor production.
- Pilocarpine eye drops to enhance aqueous humor drainage.
- IV mannitol to decrease aqueous humor volume.
- Peripheral iridectomy using a laser to create an iris hole for fluid drainage.
- Cataract surgery as a preventive and treatment measure for CAG.
Recognizing the differences between open-angle and closed-angle glaucoma is key for early diagnosis and treatment.
Both conditions can lead to vision loss, but timely diagnosis and treatment can help preserve your sight. If you have symptoms or risk factors, visit Krishna Eye Centre for a comprehensive eye exam.
Our Sion, Dadar, and Parel, Mumbai clinics offer expert care from highly qualified ophthalmologists. Krishna Eye Centre aims to reduce its impact and improve patient outcomes by raising awareness about glaucoma.
