Corneal Scar

A corneal scar is permanent opacification from fibrous tissue replacing normal stromal lamellae after injury, infection, inflammation or surgery.

• Classification by density: nebula (faint, visible only at the slit lamp), macula (dense, visible with a torch, iris details still seen), leucoma (dense white, obscuring iris details); adherent leucoma when the iris is incarcerated.
• Causes: microbial keratitis (bacterial, fungal, herpetic, acanthamoeba), trauma and perforation, chemical injury, trachoma, vitamin A deficiency, ophthalmia neonatorum, corneal dystrophies, post-surgical scarring, and peripheral ulcerative disease.
• Corneal opacity is a leading cause of blindness in low income regions, mostly from preventable infection and trauma.
• Children: corneal scarring causes deprivation amblyopia and is a visual emergency.

• Reduced vision, glare and haloes (irregular astigmatism and light scatter), monocular diplopia, cosmetic concern.
• White or grey opacity with varying density, location (central scars are most disabling) and vascularisation.
• Associated features: thinning, ectasia, irregular astigmatism, anterior synechiae, secondary glaucoma, cataract.
• In children: squint, nystagmus, poor fixation.

• Visual acuity, pinhole and contact lens over refraction to distinguish scar from irregular astigmatism.
• Slit lamp: depth, density, size, location, vascularisation, and active inflammation.
• Anterior segment OCT for depth of scar; corneal topography and tomography; pachymetry; specular microscopy if the endothelium is considered.
• Assess intraocular pressure, lens, and posterior segment (B-scan ultrasound if no view).
• Establish the cause and exclude active infection or inflammation before surgery.

• Treat any active cause first: antimicrobials for infection, antiviral prophylaxis (aciclovir 400 mg twice daily) in herpetic scarring, control of inflammation (topical prednisolone acetate 1 percent tapered).
• Optical correction: spectacles for mild scars, rigid gas permeable lenses or scleral lenses to mask irregular astigmatism.
• Cosmetic: tinted or painted prosthetic soft contact lens, scleral shell, or corneal tattooing in blind eyes.
• Laser: phototherapeutic keratectomy for superficial scars (to a depth of about 100 to 120 micrometres), with mitomycin C 0.02 percent for 30 to 60 seconds in some cases to reduce haze.
• Surgery for visually significant scars: deep anterior lamellar keratoplasty (healthy endothelium), penetrating keratoplasty (full thickness scarring or endothelial damage), anterior lamellar keratoplasty for superficial scars.
• Failed keratoplasty or severe ocular surface disease: keratoprosthesis (Boston type 1 or 2, osteo-odonto-keratoprosthesis).
• Children: early surgery, optical correction and amblyopia therapy (patching of the better eye for 2 to 6 hours daily).
• Prevention: protective eyewear, prompt treatment of keratitis, vitamin A supplementation (200,000 IU orally for children over 12 months, repeated at 24 hours and 2 weeks if deficient), avoid traditional eye medicines.