Corneal Degeneration

Corneal degenerations are non-inflammatory, often age related, deposits or thinning of the cornea, usually bilateral and slowly progressive. They differ from dystrophies, which are inherited and appear earlier.

• Arcus senilis (gerontoxon): lipid deposition in the peripheral stroma, with a clear interval (lucid interval) from the limbus. Normal in older adults; in patients under 40 years it suggests hyperlipidaemia (familial hypercholesterolaemia).
• Vogt limbal girdle: crescentic white lines at the nasal and temporal limbus.
• Salzmann nodular degeneration: bluish white elevated nodules, often after chronic keratitis, trachoma or phlyctenulosis.
• Spheroidal degeneration (climatic droplet keratopathy): amber subepithelial droplets from ultraviolet exposure in outdoor workers.
• Lipid keratopathy: stromal lipid with neovascularisation.
• Terrien marginal degeneration: peripheral, painless, slowly progressive thinning with lipid line, more common in males, risk of perforation after minor trauma.
• Pellucid marginal degeneration: inferior band of thinning above which the cornea protrudes, causing irregular against-the-rule astigmatism.
• Others: crocodile shagreen, white limbal girdle, Cornea farinata, amyloid, and corneal keloid.

• Most are asymptomatic.
• Terrien: progressive astigmatism and reduced vision, thinning with vascularised lipid border, pseudopterygium.
• Salzmann: reduced vision, irritation, glare, with nodules in the mid-peripheral cornea.
• Spheroidal: oily droplets, reduced vision in advanced cases.
• Pellucid: gradual vision loss from irregular astigmatism; acute hydrops is possible.
• Complications: perforation, scarring, recurrent erosions.

• Slit lamp for distribution and depth; corneal topography and tomography (crab claw pattern in pellucid; steepening of the inferior cornea).
• Pachymetry, anterior segment OCT.
• For arcus in younger patients: fasting lipid profile.
• Distinguish from keratoconus, Mooren ulcer (painful, undermined edge) and peripheral ulcerative keratitis.

• No treatment for asymptomatic degeneration.
• Lubrication for irritation.
• Terrien and pellucid: spectacles or rigid gas permeable lenses and scleral lenses for astigmatism; corneal cross linking (selected cases); crescentic lamellar keratoplasty or wedge resection for severe thinning; urgent management of perforation (glue and patch graft).
• Salzmann: superficial keratectomy with or without mitomycin C 0.02 percent for 1 to 2 minutes, phototherapeutic keratectomy, and amniotic membrane; recurrence about 20 to 30 percent.
• Spheroidal: superficial keratectomy, phototherapeutic keratectomy, or lamellar keratoplasty for dense opacities; ultraviolet protective eyewear.
• Lipid keratopathy: treat underlying inflammation, argon laser or needle diathermy to feeder vessels, subconjunctival or topical bevacizumab 1.25 mg/0.05 mL or 1 percent drops, and keratoplasty.
• Arcus: lipid lowering with statin (atorvastatin 20 to 80 mg daily) when hyperlipidaemia is identified; screen first degree relatives.