Overview
This lecture covers Vernal Keratoconjunctivitis (VKC), focusing on its definition, epidemiology, pathophysiology, clinical features, forms, grading, and classifications.
Definition and Epidemiology
- VKC is a chronic, bilateral, interstitial allergic inflammation of the cornea and conjunctiva.
- Common in children, especially boys, with onset in the first decade and resolution by late puberty.
- Higher prevalence in those with atopic backgrounds (asthma, eczema, allergies) but is distinct from atopic keratoconjunctivitis (AKC).
- More common in hot, dry, tropical climates; incidence decreases with distance from the equator.
Pathophysiology
- Triggered by chronic exposure to allergens, leading to mast cell degranulation and T-helper 2 (Th2) cell activity.
- Involves both Type 1 (immediate) and Type 4 (delayed) hypersensitivity reactions.
- Chronic inflammation recruits various immune cells to conjunctiva and cornea, stimulating fibroblast proliferation and extracellular matrix deposition (hyalinization).
- Results in remodeling of conjunctival tissues and formation of characteristic papillae.
Pathological Changes
- Epithelial layer shows hyperplasia and hypertrophy.
- Adenoid layer infiltrated by eosinophils, lymphocytes, plasma cells, and macrophages.
- Fibrous layer undergoes hyalinization with collagen deposition.
- Conjunctival vessels show increased permeability and vasodilation.
Clinical Features: Symptoms
- Marked itching and burning, worsening in warm, dry conditions.
- Ropey, stringy mucous discharge and lacrimation.
- Foreign body sensation, eyelid heaviness, ptosis, photophobia, and sometimes pain or decreased vision if cornea involved.
Clinical Features: Signs and Forms
- Palpebral (Tarsal) Form: Hard, flat-topped giant papillae on upper tarsal conjunctiva ("cobblestone" appearance), often with ropey discharge; grading based on papillae size.
- Bulbar (Limbal) Form: Dusky red, triangular congestion near limbus and gelatinous limbal papillae; Horner-Trantas dots (white chalky nodules) indicate severe disease.
- Mixed Form: Features of both, common in the Indian subcontinent.
- Skin of eyelids is typically not involved (unlike AKC).
Corneal Involvement and Complications
- Chronic inflammation causes punctate epithelial erosions which may coalesce into shield ulcers, often requiring debridement if plaque forms.
- Shield ulcers graded by size, transparency, and presence of plaque.
- Chronic disease may cause pseudogerontoxon (peripheral corneal opacity), superior periocular pigmentation, and blinding complications (limbal stem cell deficiency, pannus, thinning, cataract, glaucoma).
Classification and Grading
- Severity: Mild (symptoms, papillae), moderate (with Horner-Trantas dots or superficial keratopathy), severe (cobblestone papillae, extensive limbal inflammation), blinding (corneal ulcer, scarring, limbal stem cell deficiency, glaucoma).
- Periodicity: Intermittent (<4 episodes/year with remission), chronic (symptoms persist all year).
- Bonini Grading: Grade 0 (quiescent) to Grade 4 (very severe, with corneal complications).
Key Terms & Definitions
- Vernal Keratoconjunctivitis (VKC) — Chronic allergic inflammation of cornea and conjunctiva, often in children.
- Papillae — Elevated nodules with central blood vessel on conjunctiva, hallmark of VKC.
- Horner-Trantas Dots — White chalky deposits on limbus, indicating severe VKC.
- Shield Ulcer — Large, oval corneal ulcer due to VKC, may have a plaque impeding healing.
- Hyalinization — Deposition of homogeneous, glassy protein material in tissue due to chronic inflammation.
- Panus — Fibrovascular tissue growth onto cornea from limbus.
- Limbal Stem Cell Deficiency — Loss of regenerative cells at the limbus, causing conjunctivalization of cornea.
Action Items / Next Steps
- Review key signs and symptoms for identification of VKC and its forms.
- Understand differences between VKC and AKC for differential diagnosis.
- Study grading/classification systems (clinical severity, Bonini grading).
- Practice identifying clinical features in images, especially papillae and Horner-Trantas dots.