Glaucoma: Types, Symptoms, and Prevention

• Glaucoma is a group of eye conditions damaging the optic nerve, often caused by abnormally high pressure in the eye.
• Glaucoma is a leading cause of irreversible blindness.
• Many forms of glaucoma have no warning signs.
• Damage from glaucoma is gradual, so vision changes might not be noticed until the condition is advanced.
• Vision loss from glaucoma cannot be recovered.
• Early diagnosis and treatment can slow or prevent vision loss.
• Most people with glaucoma have no initial symptoms.
• Regular eye exams can help detect glaucoma before significant damage occurs.

Types of Glaucoma

• Open-angle glaucoma is the most common form; the drainage angle formed by the cornea and iris remains open, but the trabecular meshwork is partially blocked.
• Angle-closure glaucoma occurs when the iris bulges forward to narrow or block the drainage angle, and it may occur suddenly (acute) or gradually (chronic); it is also known as narrow-angle glaucoma.
• Normal-tension glaucoma involves optic nerve damage despite normal eye pressure; the cause is unknown.
• Secondary glaucoma can result from other medical conditions or medications like corticosteroids.
• Congenital glaucoma is a rare, inherited condition where children are born with a defect in the drainage angle.

Causes

• Glaucoma is usually caused by increased pressure in the eye, known as intraocular pressure (IOP).
• The eye continuously produces aqueous humor, which drains out through the drainage angle (trabecular meshwork).
• When drainage is blocked, pressure builds up, damaging the optic nerve.
• Factors unrelated to high eye pressure, such as poor blood supply to the optic nerve, can also cause glaucoma.
• In normal-tension glaucoma, the optic nerve is damaged despite normal IOP, and the exact cause is unknown but may involve a sensitive optic nerve or decreased blood supply.

Risk Factors

• High intraocular pressure (IOP) is a risk factor for glaucoma.
• Age over 60 increases the risk of glaucoma.
• A family history of glaucoma increases risk.
• Race: African Americans, Hispanics, and Asians are at higher risk of glaucoma.
• Medical conditions, including diabetes, heart disease, high blood pressure, and sickle cell anemia, increase glaucoma risk.
• Thin cornea.
• Farsightedness or nearsightedness.
• Eye injury or certain types of eye surgery.
• Corticosteroid medications, especially eye drops, for extended periods.

Symptoms

• Open-Angle Glaucoma:
  • Patchy blind spots in the peripheral or central vision, frequently in both eyes.
  • Tunnel vision in the advanced stages.
• Acute Angle-Closure Glaucoma:
  • Severe headache
  • Eye pain
  • Nausea and vomiting
  • Blurred vision
  • Halos around lights
  • Reddening of the eye
• Normal-Tension Glaucoma:
  • Similar to open-angle glaucoma (patchy blind spots, tunnel vision)
• Congenital Glaucoma:
  • Excessive tearing
  • Light sensitivity
  • Cloudiness of the cornea
  • Enlargement of one or both eyes

Diagnosis

• Tonometry measures intraocular pressure (IOP).
• Ophthalmoscopy examines the optic nerve for damage.
• Perimetry tests the field of vision to identify blind spots.
• Gonioscopy inspects the drainage angle.
• Pachymetry measures corneal thickness, as thin corneas may lead to inaccurate IOP readings.
• Optical coherence tomography (OCT) is an imaging technique to assess optic nerve and retinal nerve fiber layer damage.

Treatments

• Eye Drops: Medications to reduce IOP, either by increasing fluid drainage or decreasing fluid production in the eye.
  • Prostaglandins: Increase the outflow of fluid from the eye (e.g., Latanoprost, Bimatoprost, Travoprost).
  • Beta-blockers: Reduce the production of fluid in the eye (e.g., Timolol, Betaxolol).
  • Alpha-adrenergic agonists: Reduce fluid production and increase outflow (e.g., Brimonidine, Apraclonidine).
  • Carbonic anhydrase inhibitors: Reduce fluid production (e.g., Dorzolamide, Brinzolamide).
  • Rho kinase inhibitors: Increase outflow of fluid (e.g., Netarsudil).
• Oral Medications: Carbonic anhydrase inhibitors (e.g., Acetazolamide, Methazolamide) may be prescribed to reduce fluid production.
• Laser Therapy:
  • Selective Laser Trabeculoplasty (SLT) opens blocked drainage canals in open-angle glaucoma.
  • Laser Peripheral Iridotomy (LPI) creates a small hole in the iris to improve fluid flow in angle-closure glaucoma.
  • Cyclophotocoagulation reduces fluid production by targeting the ciliary body.
• Surgery:
  • Trabeculectomy creates a new drainage channel to lower IOP.
  • Glaucoma Drainage Devices (Tube Shunts) implant a tube to drain fluid.
  • Minimally Invasive Glaucoma Surgery (MIGS) includes techniques like iStent, Kahook Dual Blade goniotomy, and others to enhance drainage with minimal tissue disruption.

Prevention

• Regular eye exams are important (including IOP measurement, optic nerve assessment, and visual field testing).
• Know your family history.
• Exercise regularly.
• Maintain a healthy weight.
• Control blood pressure.
• Avoid or limit corticosteroid use, especially eye drops, unless absolutely necessary.
• Wear eye protection to prevent eye injuries.

Glaucoma comprises eye conditions damaging the optic nerve, often due to high eye pressure. Early diagnosis and treatment are crucial for slowing or preventing vision loss, as damage is gradual and often without initial symptoms. Regular eye exams are essential for timely detection and management.