Classification by Age:

• Congenital (0 years old),
• Infantile (0-2 years old),
• Juvenile (2-34 years old),
• Adult (35+ years old).

Classification by Glaucoma Types and Mechanisms:

• Open-angle glaucoma,
• Angle-closure glaucoma,
• Mixed type.

Glaucoma can be primarily classified into two types: open-angle and angle-closure glaucoma.

Open-Angle Glaucoma

This is the most common type of glaucoma, accounting for 85-90% of cases. It is a chronic disease characterized by resistance to outflow of the aqueous humor, the fluid responsible for draining from the trabecular meshwork. As a result, the intraocular pressure gradually increases. This slow rise in pressure does not cause noticeable symptoms and can go undetected until advanced stages of visual loss. In open-angle glaucoma, the disease progresses silently without clear symptoms, and patients may not be aware of their condition. Visual loss can only be detected through advanced tests. Patients usually become aware of their deteriorating vision and seek medical attention when they are close to the advanced stage. However, by that time, the optic nerve has already been significantly damaged, and the visual field has narrowed. Treatment can only help preserve the remaining vision, as the lost vision cannot be restored. Increasing intraocular pressure starts to mechanically damage the nerve fibers of the optic nerve. The damage to the nerve fibers is monitored through visual field examinations. When these damages reach a certain level, the optic nerve head collapses, resulting in irreversible vision loss. This group includes high-pressure, normal-pressure, and secondary types of glaucoma. The most common type is high-pressure glaucoma, which occurs in approximately 1 in 100 individuals, with more than half of the affected individuals unaware of their condition. If left untreated, it can gradually lead to irreversible blindness. a) Normal-Tension Open-Angle Glaucoma Also known as low-pressure glaucoma, it is characterized by visual field loss and optic nerve damage despite normal intraocular pressure (within the universally accepted range, not exceeding 22 mmHg). In these eyes, the optic nerve head becomes susceptible and weak due to impaired circulation. Even with normal intraocular pressure, the optic nerve head develops cupping, and visual field defects occur. Vasoconstrictive conditions such as migraines and Raynaud’s phenomenon (discoloration of fingers in cold) and individuals who experience a significant drop in blood pressure due to antihypertensive medications are at risk for normal-tension glaucoma. It is particularly common in older individuals. In these cases, a circulation disorder in the optic nerve is present, and intraocular pressure needs to be lowered below normal values. b) Ocular Hypertension Ocular hypertension, also known as ocular high pressure, occurs when the intraocular pressure is elevated (22 mmHg or higher), but there is no evidence of optic nerve damage or visual field defects. It is not considered glaucoma. However, it can progress to glaucoma, so regular follow-up is necessary. In individuals with ocular hypertension, visual field examinations are performed at appropriate intervals as intraocular pressure continues to rise. As long as the optic nerve fibers are healthy, no treatment is required. c) Congenital and Infantile Glaucomas These conditions are rare, occurring in approximately 1 in 10,000 individuals, and are present at birth. Congenital and infantile glaucomas are characterized by malformation or abnormal development of the drainage angle in the eye. Symptoms such as excessive eye growth, light sensitivity, tearing, and blurred vision become apparent within a few months after birth. In infants with glaucoma, as the intraocular pressure rises, the cornea loses transparency and becomes cloudy, and the eyes start to tear. These signs are usually noticed by parents. If increased intraocular pressure and the condition go unnoticed by the age of 3, the eyes start to enlarge (resulting in an ox-eye appearance). If it affects only one eye, it can be easily recognized, but if it affects both eyes, the diagnosis may be delayed. Immediate surgical intervention is almost always necessary in these types of glaucoma. Without early surgical treatment, permanent blindness can occur throughout life. Due to structural abnormalities, repeated surgeries and close monitoring may be required.

Angle-Closure Glaucoma

Angle-Closure (Acute) Glaucoma Crisis

Angle-closure glaucoma accounts for 5-10% of glaucoma cases. It is more common in individuals with narrow or predisposed drainage angles in their eyes. It can be hereditary and can be observed in different individuals within the same family simultaneously. It is more prevalent in hyperopic (farsighted) individuals. Angle-closure glaucoma crisis occurs at an average age of 60, is four times more common in women, and is more frequently observed in individuals with a family history of the condition. In addition, diabetes, retinal vascular occlusions, uveitis, complications of cataract surgery, and various other conditions can cause secondary angle-closure glaucoma. Sometimes, both open-angle glaucoma and angle-closure glaucoma can coexist. Individuals with narrow drainage angles have a narrower anterior chamber compared to normal individuals. As they age, the angle further narrows due to lens enlargement, leading to elevated intraocular pressure. When the angle completely closes, acute glaucoma occurs. The pupil dilates and covers the superior portion of the drainage angle, blocking the outflow of aqueous humor and causing increased intraocular pressure. Unlike the silent and asymptomatic nature of open-angle glaucoma, angle-closure glaucoma presents with a very symptomatic and dramatic clinical picture. Most attacks occur in the dark or during stressful situations when the pupil dilates and the angle narrows. Additionally, antidepressants, cold and flu medications, antihistamines, and antiemetics that dilate the pupil can also trigger angle-closure glaucoma crisis. Mild attacks can be self-relieved by transitioning to a well-lit environment or sleeping because the pupil constricts. Angle-closure glaucoma, also known as acute glaucoma crisis, manifests with severe eye pain, redness, blurred and decreased vision, light sensitivity, and nausea and vomiting. In this condition, the eye pressure is usually found to be very high, reaching 40-50 mmHg or even higher. Such high intraocular pressure paralyzes the pupil. The eye pain is severe and can induce vomiting. This is an emergency situation, and if treatment is delayed, it can result in vision loss. Rapid development of cataracts and optic nerve damage can occur. When these symptoms are observed, the patient should seek medical attention as soon as possible without attempting to alleviate the pain with analgesics. Individuals with narrow drainage angles are usually alerted by their doctors about such a crisis. If severe eye pain and eye hardening accompany these symptoms, immediate medical attention should