Conjunctivitis, Pterygium & Trachoma: Eye Guide

Conjunctivitis is inflammation of the conjunctiva, the thin clear membrane covering the white of the eye and the inside of the eyelids — pink eye. A pterygium is a fleshy, wing-shaped growth of conjunctival tissue that creeps onto the cornea. Trachoma is a chronic eye infection caused by the bacterium Chlamydia trachomatis, the world's leading infectious cause of blindness.

These matter because they affect millions yearly. Conjunctivitis sweeps through schools and offices because it spreads so easily. Trachoma blinds through repeated infections in communities with poor water and sanitation, yet it is entirely preventable. Pterygium threatens the vision of outdoor workers who spend years in sun, wind and dust.

Key Concepts

• Viral conjunctivitis: usually adenovirus — watery discharge, gritty feeling, often one eye then the other. Highly contagious; no antibiotic helps; resolves in 1–3 weeks.
• Bacterial conjunctivitis: sticky yellow-green pus with eyelids glued shut in the morning, caused by Staphylococcus or Streptococcus. Treated with topical antibiotic drops or ointment.
• Allergic conjunctivitis: intensely itchy, red, watery eyes, almost always both together. Treated with antihistamine drops and cold compresses.
• Pterygium: a triangular fibrovascular growth, usually on the nasal side, driven by ultraviolet exposure. Small ones need lubricants and sunglasses; large ones are removed surgically with a conjunctival autograft to prevent regrowth.
• Trachoma grades (WHO): TF — five or more ≥0.5 mm follicles on the upper tarsal conjunctiva (active disease); TI — intense inflammation; TS — scarring; TT — trichiasis (in-turned lashes scratching the cornea); CO — corneal opacity.
• SAFE strategy: the WHO program to eliminate trachoma — Surgery for trichiasis, Antibiotics (single-dose azithromycin), Facial cleanliness, and Environmental improvement (clean water, sanitation).

How It Works

1. Tell the red eyes apart: watery discharge spreading between eyes suggests viral; thick pus gluing lids suggests bacterial; intense itching in both eyes suggests allergy.
2. Check for growths and follicles: a fleshy wing creeping onto the cornea is pterygium; bumpy follicles on the inner upper lid in a child suggest trachoma.
3. Grade trachoma: evert the upper lid and count follicles at least 0.5 mm wide — five or more means active TF disease needing antibiotics.
4. Treat accordingly: viral gets hygiene and time, bacterial antibiotic drops, allergy antihistamines, pterygium sunglasses or surgery, trachoma the full SAFE strategy.

Worked Example

1. During a school screening, a 9-year-old girl's upper eyelid is everted. Seven distinct follicles, each at least 0.5 mm across, are visible on the tarsal conjunctiva.
2. The WHO threshold for active trachoma (TF) is five or more follicles of at least 0.5 mm. Seven is greater than five, so she has TF — active trachomatous inflammation.
3. Per SAFE she receives single-dose azithromycin (20 mg/kg), her family is counseled on face washing, and her siblings are screened the same day.

Common Misconceptions

• Myth: All pink eye needs antibiotic drops. Fact: viral and allergic conjunctivitis do not respond to antibiotics; wrong drops waste money and breed resistance.
• Myth: Eye drops can dissolve a pterygium. Fact: no drop removes the growth; only surgery does, and UV protection prevents recurrence.
• Myth: Trachoma has been wiped out. Fact: it still blinds in the poorest regions; SAFE is active elimination work.

Real-World Applications

• School health programs: rapid triage of pink-eye outbreaks by discharge type keeps classrooms safe.
• WHO elimination campaigns: mass azithromycin distribution plus sanitation work under the SAFE strategy.
• Occupational health: UV-blocking sunglasses for farmers, fishermen and construction workers prevent pterygium.

Conjunctivitis comes in viral, bacterial and allergic forms with different discharges and treatments; pterygium is a sun-driven growth removed by surgery; and trachoma is graded by follicle count and fought with the SAFE strategy. Telling red eyes apart is the whole battle.