Ocular Toxicology

Ocular Tox Basics - Toxic Trouble Types

• Scope: Ocular toxicology investigates adverse effects of drugs, chemicals, and physical agents on eye structures and visual function.
• Routes of Exposure:
  • Systemic: Ingestion, inhalation, injection (IV/IM).
  • Topical: Eye drops, ointments, contact lenses.
  • Direct: Chemical burns, foreign bodies, trauma.
  • Intraocular: Surgical, injections.
• Mechanisms of Damage:
  • Direct cytotoxicity.
  • Inflammation & immune reactions.
  • Vascular endothelial damage.
  • Neurotoxicity (e.g., optic nerve).
  • Phototoxicity.

⭐ Chloroquine/Hydroxychloroquine can cause "bull's eye" maculopathy, a classic example of drug-induced retinal toxicity.

Systemic Drugs & Eye - Eye Alarms

Many systemic drugs cause ocular toxicity. Early recognition prevents irreversible damage.

Topical Agents & Tox - Drop Dangers

• Benzalkonium Chloride (BAK): Most common preservative.
  • Detergent; disrupts cell membranes.
  • Toxicity: Corneal epithelial damage, ↓ tear film stability, conjunctival inflammation. Dose & duration-dependent.
  • 📌 BAK: Bothers And Kills cornea.
• Key Agent Toxicities:
  • Topical Anesthetics (e.g., Proparacaine): Abuse → ring keratitis, persistent epithelial defects.
  • Miotics (e.g., Pilocarpine): Brow ache, induced myopia. Chronic use → iris cysts, anterior subcapsular cataracts.
  • Mydriatics (e.g., Phenylephrine): 10% solution ↑ systemic risk (hypertension, arrhythmias) vs 2.5%. ⚠️ Caution: infants, elderly.
  • Thimerosal: Mercury-based; hypersensitivity.

⭐ BAK-induced ocular surface disease significantly impacts long-term glaucoma management and patient adherence.

Chemicals & Plants - Eye Assaults

• Chemical Burns:

  • Acids: Coagulative necrosis (barrier). E.g., $H_2SO_4$. Less severe.
  • Alkalis: Liquefactive necrosis (saponification). Deeper penetration. More severe. E.g., $NaOH$, $Ca(OH)_2$ (cement), $NH_3$.

    ⭐ Alkali burns are more severe than acid burns due to deeper tissue penetration.

  • Management:
    • Immediate copious irrigation (water/saline) for 15-30 mins.
    • Check pH (target 7.0-7.4). Morgan lens.
    • 📌 Mnemonic: "ALKALI = ALL KILLS EYE".

• Plant Toxins:

  • Calotropis (Madar): Milky latex → kerato-uveitis, corneal edema.
  • Ricinus communis (Castor): Ricin → conjunctivitis, keratitis.
  • Datura: Atropine → mydriasis, cycloplegia.
  • Parthenium: Allergic conjunctivitis.

Ocular Tox Management - Eye Emergency Rx

• Priority: Rapid, thorough decontamination.
• Key Actions:
  • Ensure ABCs; remove from source; remove contact lenses.
  • Irrigate: Copious sterile saline/Ringer's lactate/tap water for 15-30 min. Morgan lens aids continuous flow.
  • pH Testing: Check conjunctival fornix pH (normal 7.0-7.4). Continue irrigation until neutralized.
  • Identify toxin.
  • Medications: Topical anaesthetic, cycloplegic, antibiotic.
  • Urgent ophthalmology referral.

⭐ For chemical eye burns, immediate and copious irrigation (minimum 1-2L or for 15-30 minutes) is paramount, even before full assessment.

High‑Yield Points - ⚡ Biggest Takeaways

• Chloroquine/Hydroxychloroquine: Bull's eye maculopathy; regular screening vital.
• Ethambutol: Optic neuritis (retrobulbar, dose-dependent); monitor red-green color vision.
• Corticosteroids: Posterior subcapsular cataract and steroid-induced glaucoma.
• Amiodarone: Vortex keratopathy (corneal verticillata) and optic neuropathy.
• Digitalis: Xanthopsia (yellow vision) and blurred vision.
• Tamoxifen: Crystalline retinopathy and macular edema.
• Methanol poisoning: Severe optic atrophy, "snowstorm" vision, and potential blindness.