Glaucoma

This is the most common type, where fluid drains too slowly through the trabecular meshwork, causing pressure to build gradually over months or years. The drainage canals become clogged over time, and this increased intraocular pressure damages the optic nerve. Most patients do not notice symptoms until significant vision is affected because peripheral vision loss occurs so slowly that the brain compensates. Risk factors include age over 60, family history, African or Hispanic ancestry, diabetes, high blood pressure, and previous eye trauma. With regular eye exams, open-angle glaucoma may be found early and usually responds well to treatment to preserve remaining vision.

This type happens when the drainage angle between the iris and cornea suddenly closes or narrows significantly, raising pressure quickly and causing an acute attack. The angle closure occurs when the pupil dilates in dim lighting, with strong emotions, or with certain medications, and the iris blocks the trabecular meshwork where fluid must drain. Symptoms include severe eye pain, intense headache, halos around lights, nausea, vomiting, blurred vision, and a sudden, severe decrease in vision that requires immediate emergency treatment. Eye pressure may reach 60 to 70 mm Hg during an acute attack instead of the normal 10 to 20 mm Hg, and permanent vision loss can occur within hours without treatment. Chronic angle-closure glaucoma can develop slowly with less dramatic symptoms when the angle closes gradually over time.

Here, the optic nerve is damaged even when eye pressure measurements remain within the statistically normal range of 10 to 21 mm Hg. Vascular issues like migraine, poor blood flow to the optic nerve, or blood pressure that drops too low at night may reduce oxygen delivery to nerve tissue and play a role, though the exact cause is still unclear. Researchers are studying why some optic nerves are more vulnerable to damage at relatively low fluid pressures, and factors like thin corneas, autoimmune conditions, and Japanese ancestry have been identified as risk factors. Treatment focuses on lowering pressure even further below the patient's baseline to slow progression.

Secondary glaucoma develops after eye injury, inflammation such as uveitis, eye surgery complications, advanced cataracts, diabetes, or use of certain medications including corticosteroids, while congenital glaucoma is present at birth due to abnormal development of the eye's drainage system. Secondary glaucoma may occur in one or both eyes depending on the underlying cause, and treating the primary condition is essential alongside pressure-lowering therapy. Congenital glaucoma causes cloudiness of the cornea, excessive tearing, light sensitivity, and enlargement of the eye in infants, and early surgical intervention is usually required to preserve vision.

• Prostaglandin analogs – increase fluid outflow and are often used as first-line therapy due to once-daily dosing and effectiveness, though they may cause iris darkening and eyelash growth.
• Beta blockers – reduce fluid production by the ciliary body, used with caution in patients with asthma, heart rhythm problems, or low blood pressure.
• Carbonic anhydrase inhibitors – lower fluid production and are available as eye drops or oral tablets, though oral forms may cause fatigue and tingling.
• Alpha agonists – both reduce fluid production and increase drainage, but may cause dry mouth, fatigue, and allergic reactions in some patients.
• Rho kinase inhibitors – help fluid drain by relaxing trabecular meshwork tissue and improving outflow facility.
• Fixed-combination drops – combine two medications in one bottle to improve adherence and reduce preservative exposure.

Selective laser trabeculoplasty (SLT) uses targeted laser energy to help fluid drain better in open-angle glaucoma by stimulating cellular changes in the trabecular meshwork, and the LiGHT trial showed SLT is as effective as topical medications as first-line treatment. Laser peripheral iridotomy (LPI) creates a small opening in the iris to allow fluid to bypass the pupil and prevent angle closure in patients at risk. Laser procedures are performed in the office, typically cause minimal discomfort, and have low risk of serious complications.

Minimally invasive glaucoma surgery (MIGS) uses tiny devices like iStent, Hydrus, or Xen gel stent to improve drainage through micro-incisions with faster recovery and fewer risks than traditional surgery. MIGS procedures are often performed during cataract surgery to treat both conditions simultaneously and reduce medication burden. However, MIGS may not be effective for all patients, especially those with advanced glaucoma, angle-closure glaucoma, very high pressure, or thyroid eye disease, and success rates are generally lower than traditional surgery. Recovery is typically quick with return to normal activities within days, though pressure reduction is often more modest than with trabeculectomy or tube shunts.

Trabeculectomy creates a new drainage channel under the conjunctiva to allow fluid to filter out of the eye into a bleb or reservoir, and this procedure achieves the greatest pressure reduction for advanced disease. Tube shunt surgery diverts fluid from inside the eye through a small tube to a plate positioned on the eye surface where it is absorbed. Regular follow-up ensures proper healing, monitors for complications like infection or scarring, and assesses long-term success in maintaining target pressure.