Glaucoma (Black Water Disease)

The front part of the eye consists of the cornea, a transparent structure, followed by the iris, which gives the eye its color, and the lens, located behind the iris. The central opening in the iris is called the pupil, which allows light to pass through. The space between the cornea and the lens is divided into two chambers by the iris:

• The anterior chamber (between the cornea and the iris)
• The posterior chamber (between the iris and the lens)

Behind the lens is the vitreous body, a gelatinous, transparent structure that fills the eye. Surrounding the vitreous are:

• Retina (the nerve layer responsible for vision)
• Choroid (the vascular layer that supplies oxygen and nutrients)
• Sclera (the outer, protective layer of the eye)

The sclera is covered by a vascular membrane called Tenon’s capsule and the conjunctiva, a thin protective layer.

The ciliary body, located at the equator of the lens, produces aqueous humor, the fluid inside the eye. The aqueous humor flows through the trabecular meshwork, located at the junction of the iris root and cornea, and exits through drainage channels.

What is Glaucoma?

Glaucoma occurs when the aqueous humor is either produced in excess or cannot drain properly, leading to an increase in intraocular pressure (IOP). The normal IOP range is 10-20 mmHg. Values above this range are considered abnormal.

However, not all increases in intraocular pressure indicate glaucoma. If IOP is high but the optic nerve and visual field remain unaffected, the condition is called ocular hypertension, which does not necessarily require treatment.

Glaucoma, on the other hand, is characterized by elevated intraocular pressure that damages the optic nerve and visual field. If left untreated, this damage is irreversible and leads to permanent vision loss.

Additionally, normal-tension glaucoma occurs when optic nerve damage and visual field loss develop despite normal intraocular pressure.

Glaucoma is classified into two main types:

1. Open-Angle Glaucoma
2. Angle-Closure Glaucoma

Risk Factors for Glaucoma

• Age: The risk of glaucoma increases 2-4 times with age.
• Ethnicity:
  • Africans are 4 times more likely to develop open-angle glaucoma than Caucasians.
  • Chinese individuals have a higher risk of angle-closure glaucoma.
• Intraocular Pressure:
  • IOP of 23 mmHg carries a 10% risk of glaucoma.
  • IOP of 27 mmHg raises the risk to 50%.
• Refractive Errors:
  • Myopia (nearsightedness) increases the risk of open-angle glaucoma.
  • High hyperopia (farsightedness) is a risk factor for angle-closure glaucoma.
• Diabetes: Considered a relative risk factor.
• Systemic Hypertension:
  • In individuals under 60, systemic hypertension reduces glaucoma risk due to high blood pressure maintaining blood flow.
  • In individuals over 70, vascular stiffening impairs blood flow, increasing optic nerve damage risk at night.
• Hypercholesterolemia and Lipid Disorders: Increase glaucoma risk.
• Genetics: Family history of glaucoma is present in 13-45% of cases.
• Smoking: While no direct link exists, toxic chemicals in cigarette smoke can damage optic nerve blood flow.
• Alcohol: No proven association with glaucoma.

Types of Glaucoma

1. Open-Angle Glaucoma

• Most common type of glaucoma, typically occurring in older adults.
• Caused by increased resistance in the trabecular meshwork, leading to slow drainage of aqueous humor.
• Symptoms develop gradually, often without noticeable signs until significant vision loss has occurred.
• Risk Factors: High IOP, old age, large fluctuations in IOP, genetics, myopia, optic nerve sensitivity.
• Treatment:
  • First-line treatment: Eye drops to lower IOP.
  • If medications fail: Laser therapy or glaucoma surgery.

2. Normal-Tension Glaucoma

• Damage to the optic nerve and visual field occurs despite normal IOP.
• Caused by vascular insufficiency, leading to poor blood flow to the optic nerve.
• Occurs more frequently in patients with systemic hypertension due to nighttime blood pressure drops.
• Treatment goal: Reduce IOP by 30% and improve optic nerve blood flow.

3. Angle-Closure Glaucoma

• Familial condition, most common in Asians and hyperopic individuals.
• Occurs due to pupil dilation, which blocks the drainage angle, leading to IOP spikes.
• Triggers include:
  • Prolonged darkness (e.g., watching TV in the dark)
  • Sleeping face-down
  • Certain medications and stress
• Symptoms:
  • Severe headache
  • Nausea and vomiting
  • Red eyes
  • Blurry vision due to corneal swelling
• Treatment:
  • Emergency medication to reduce IOP
  • Laser iridotomy to create an opening in the iris for drainage
  • Surgery if laser treatment is insufficient

4. Pigmentary Glaucoma

• More common in men, myopic individuals, and people in their 20s.
• Occurs when iris pigment flakes off, blocking the trabecular meshwork.
• Regular monitoring is essential, as IOP can increase over time.

5. Exfoliative Glaucoma

• Aging-related condition where flaky deposits accumulate on the lens, iris, and trabecular meshwork.
• When deposits block drainage, IOP rises rapidly, leading to severe optic nerve damage.

6. Neovascular Glaucoma

• Occurs due to abnormal blood vessel growth in the angle, usually triggered by retinal vascular diseases.
• Difficult to treat, as traditional glaucoma surgeries often fail due to scarring.
• Treatment involves implanting drainage devices to create an alternative fluid outflow path.

7. Congenital Glaucoma

• Present at birth, caused by a developmental defect in the drainage angle.
• More common in boys and often bilateral.
• Symptoms include light sensitivity, excessive tearing, and eye enlargement.
• Requires surgical correction, as medications are ineffective.

Glaucoma Treatment Options

1. Medication

• First-line treatment involves using eye drops to lower IOP.
• If eye drops fail, oral medications may be prescribed, but they have systemic side effects.

2. Laser Therapy

• Laser Iridotomy:

  • Used for angle-closure glaucoma to create an opening in the iris.
  • Potential side effects: Bleeding, increased IOP, cataract formation, corneal damage.

• Laser Iridoplasty:

  • Used to widen the drainage angle by reshaping the iris root.

• Laser Trabeculoplasty:

  • Creates small holes in the trabecular meshwork to improve fluid drainage.
  • May require repeat sessions.

3. Surgical Treatment

• Trabeculectomy:

  • A small portion of the sclera and trabecular meshwork is removed to enhance fluid drainage.
  • Does not improve vision but may stabilize vision loss.
  • Complications: Bleeding, cataract formation, low IOP, wound leakage.

• Drainage Implants:

  • Used for neovascular glaucoma when traditional surgery fails.

Glaucoma is a progressive and irreversible disease, making early detection and treatment critical in preventing blindness.