What are chemists of the eye?

Chemists of the Eye: Understanding Ocular Surface Anatomy and Disorders

The term "chemists of the eye" likely refers to the chemical composition and structures of the ocular surface, which includes the conjunctiva, cornea, and tear film that work together to maintain eye health and function. 1

Anatomy of the Ocular Surface

• The ocular surface consists of the conjunctiva (a translucent mucous membrane) and the cornea (transparent front part of the eye), which are covered by a complex tear film 1
• The conjunctiva extends from the eyelid margin to the corneal limbus and contains epithelial cells and underlying vascular stroma 1
• The cornea is composed of:
  • A highly regular, stratified squamous nonkeratinized epithelium 1
  • A transparent stromal framework of organized collagen fibrils surrounded by extracellular matrix 1
  • An inner endothelial layer that regulates corneal water content 1

Tear Film Structure and Function

• The tear film has multiple layers that protect and nourish the ocular surface:
  • An aqueous component secreted by lacrimal glands containing growth factors, vitamins, immunoglobulins, and antimicrobial peptides 1
  • Mucins produced by conjunctival goblet cells that increase wettability of the ocular surface 1
  • An overlying lipid layer produced by meibomian glands that maintains tear film stability and minimizes evaporation 1

Ocular Surface Disorders

• Dysfunction or destruction of any part of the ocular surface can lead to various disorders 1
• Common ocular surface disorders include:
  • Blepharitis (inflammation of the lid margin) 1
  • Meibomian gland dysfunction (MGD) 1
  • Conjunctivitis (inflammation of the conjunctiva) 1
  • Keratitis (inflammation of the cornea) 1
  • Keratoconjunctivitis (inflammation affecting both cornea and conjunctiva) 1
  • Dry eye (can be aqueous-deficient, evaporative, or mixed) 1

Chemical Eye Injuries and Management

• Chemical injuries to the eye can disrupt the delicate chemistry of the ocular surface 1
• For chemical eye injuries, immediate irrigation with continuous, large volumes of clean water is recommended 1, 2
• Tap water is more effective than saline for irrigation of alkali injuries, as demonstrated in animal studies 1
• Irrigation should continue for at least 15 minutes or until advanced medical care arrives 1, 2
• The definitive endpoint for irrigation is when a healthcare professional determines that the pH of the eye has returned to normal 2

Pharmacology and Drug Delivery to the Eye

• The eye has protective barriers that limit drug absorption, including:
  • Tear flow that washes away topical medications 3
  • Corneal permeability barriers 3
  • Blood-retinal barrier 3
• Many ophthalmic drugs were not specifically designed for eye treatment, leading to potential systemic side effects 3
• Specialized drug design approaches include:
  • Chemical delivery systems (CDSs) 3
  • "Soft drugs" designed to incorporate eye-targeting into their chemical structure 3
  • Formulations that improve corneal penetration and delay elimination 4

Common Pitfalls in Managing Eye Chemical Exposure

• Delaying irrigation after chemical exposure can lead to permanent damage 2, 5
• Using insufficient volumes of irrigation fluid 1, 2
• Cross-contaminating the unaffected eye during treatment 2, 5
• Failing to contact poison control centers for expert advice on severe chemical exposures 1, 5
• Not continuing irrigation long enough to restore normal pH 2

Understanding the complex chemistry of the eye is essential for proper diagnosis and treatment of ocular conditions, particularly in emergency situations like chemical exposures where prompt and appropriate intervention can prevent permanent vision loss.