Keratoconus

👁️ Keratoconus is a progressive eye disease that can lead to significant visual impairment if not diagnosed and managed early. 🩺 Regular eye examinations are essential for individuals at risk.

📖 About Keratoconus

Keratoconus is an acquired disorder where the cornea becomes thin and bulges into a cone shape, leading to distorted vision. It usually affects both eyes, though often asymmetrically, and tends to progress until the 3rd–4th decade before stabilising. 🎯 Early detection is crucial to prevent severe visual impairment.

• 🔺 Irregular corneal curvature → cone-like protrusion.
• 📊 Incidence ≈ 50 per 100,000 people.

🧬 Aetiology

The cause is multifactorial (genetic + environmental + biochemical). Although classically non-inflammatory, oxidative stress and collagen defects play a key role.

• 🧬 Genetic: Familial predisposition, autosomal dominant pattern in some.
• 👦 Onset: Teens → early 20s.
• 🤧 Environmental: Chronic eye rubbing, atopy, allergic eye disease.
• ⚖️ Biochemical: Defective collagen cross-linking, enzymatic imbalance.
• 🔗 Associations: Down syndrome, Marfan’s, Ehlers-Danlos, Leber’s congenital amaurosis.

🩺 Clinical Presentation

• 👓 Progressive irregular astigmatism → blurred, distorted vision.
• 📐 Straight lines appear bent or wavy.
• 🔆 Glare, halos, photophobia.
• 🔁 Frequent spectacle prescription changes (esp. increasing cyl).
• 🫥 Bilateral but asymmetrical involvement.
• 📍 Signs: Munson’s sign (lower lid bulge on downgaze), Fleischer ring (iron line at base of cone), Vogt’s striae (fine vertical lines).

🧾 Differential Diagnosis

• 🌫 Corneal dystrophies (e.g. Fuchs’).
• ⚡ Post-LASIK ectasia.
• 👁️ Contact lens warpage.
• 🦠 Infective keratitis (scarring).
• 🔍 Pellucid marginal degeneration.

🔎 Investigations

• 👁️ Slit Lamp: Detects corneal thinning, Fleischer ring, Vogt’s striae.
• 📊 Keratometry / Topography: Irregular “scissoring reflex” & classic inferior steepening.
• 📉 Pachymetry: Thin cornea (< 450 μm).
• 🧲 Corneal Tomography (Scheimpflug imaging): 3D shape assessment, sensitive for early disease.
• 🔬 Specular microscopy → endothelial health.

💊 Management

Treatment is stage-dependent → from simple refractive correction to surgical interventions.

• Early / Mild: 👓 Glasses, 🟤 soft toric lenses.
• Moderate: 🔵 Rigid gas permeable (RGP) lenses, hybrid lenses, scleral lenses → create smooth refractive surface.
• Progressive / Advanced:
  • 🟡 Corneal Collagen Cross-Linking (CXL): Halts progression by stiffening stromal collagen (gold standard for progression).
  • ⚪ Intrastromal corneal rings (Intacs): Flatten cone, improve optics.
  • 🟢 Topography-guided PRK: Laser smoothing in selected cases.
  • 🧵 Corneal graft (PK/DALK): For severe thinning or scarring.
• Supportive: 🚫 Avoid eye rubbing, 🌱 treat allergy/atopy, 🔎 regular monitoring.

📈 Prognosis

• 🟢 Early: Good vision with glasses / contacts, stabilisation with CXL.
• 🟡 Progressive: Without intervention → advanced ectasia, scarring, severe vision loss.
• 🔵 Long term: With modern therapies, most patients maintain functional vision & avoid transplant.

📝 Conclusion

Keratoconus is a progressive corneal ectasia often emerging in adolescence. 🔑 Exam hallmark = irregular astigmatism not correctable with glasses. 🌟 Early CXL can preserve vision and prevent progression, while advanced disease may require transplantation. Patient education (avoid rubbing, treat allergy) is critical.

📚 References

• American Academy of Ophthalmology – Keratoconus
• Mayo Clinic – Keratoconus overview
• Rabena R, Kezirian EJ. Advances in Keratoconus Management. Clin Ophthalmol, 2019.
• Shetty R. CXL in Keratoconus. Indian J Ophthalmol, 2020.