Corneal Scarring (Corneal Opacity)

How a cornea scars

The cornea is clear because its collagen fibers are tightly and evenly arranged, and it has no blood vessels. When the deeper layer, the stroma, is damaged, repair cells lay down new collagen in a disorganized pattern. This new tissue scatters light instead of letting it through, creating a scar.

Damage confined to the thin surface layer (the epithelium), such as a simple corneal abrasion, usually heals within days without scarring. Scars form when injury or infection reaches the stroma.

Doctors grade scars by density:

Blood vessels growing into the cornea (neovascularization) and thinning or bulging of the cornea can accompany scars and affect treatment choices.

Causes of corneal scarring

Infections

• Bacterial keratitis and corneal ulcers: the most common cause in developed countries, strongly linked to sleeping or swimming in contact lenses.
• Herpes simplex keratitis: repeated flares of the cold-sore virus in the eye cause progressive scarring and are a leading infectious cause of corneal blindness in the US.
• Shingles affecting the eye.
• Fungal and acanthamoeba keratitis: linked to plant injuries and to tap water or swimming with contact lenses. These often leave dense scars.
• Trachoma: repeated chlamydia eye infections turn eyelashes inward to scratch the cornea. It is a leading infectious cause of blindness worldwide, though rare in the US.

Injury

• Deep scratches, foreign bodies and penetrating injuries
• Chemical burns, especially alkalis such as lye, lime or drain cleaner, which penetrate deeply
• Thermal and ultraviolet burns

Other causes

• Keratoconus: the thinned, cone-shaped cornea can scar at its tip, sometimes after a sudden fluid leak (hydrops).
• Previous eye surgery, including haze after laser refractive surgery
• Severe dry eye, eyelids that do not close fully, and inward-turning eyelids
• Inherited corneal dystrophies, which cause clouding in both eyes
• Vitamin A deficiency, a major cause of childhood blindness in low-income countries
• Congenital opacities present at birth

Symptoms

• Blurred or hazy vision in the affected eye
• Glare, halos and starbursts around lights, especially at night
• Distorted or ghosted images, because scars often warp the corneal surface and cause irregular astigmatism
• Light sensitivity
• A visible white or gray spot on the eye

A healed scar is usually painless. Pain and redness suggest active infection or inflammation, which needs urgent care.

Diagnosis

An ophthalmologist examines the eye with a slit lamp microscope to judge the scar's depth, size, density and position. Other tests include:

• Corneal topography or tomography to map surface irregularity and astigmatism
• Pachymetry or optical coherence tomography (OCT) to measure thickness and scar depth
• A trial with a rigid contact lens, which shows how much blur comes from surface irregularity rather than the opacity itself

Treatment

First, any active infection or inflammation must be fully controlled. Treatment then depends on how much the scar affects vision.

Non-surgical options

• Glasses if the scar is small or peripheral.
• Rigid gas-permeable or scleral contact lenses: these create a smooth new optical surface over an irregular cornea and often restore surprisingly good vision.
• Steroid eye drops under specialist supervision can reduce early, active scar formation and new blood vessels.
• Antiviral tablets long-term for herpes keratitis to prevent recurrences that add new scarring.

Laser and surgical options

• Phototherapeutic keratectomy (PTK): an excimer laser removes scars in the front 10 to 20% of the cornea.
• Partial-thickness transplant (DALK): replaces the front layers of the cornea while keeping the patient's own inner layer, lowering rejection risk.
• Full-thickness transplant (penetrating keratoplasty): for deep, dense scars. Recovery of vision takes months, and long-term drops are needed.
• Artificial cornea (keratoprosthesis): for eyes where transplants have failed or are likely to fail.

Corneal transplants are among the most successful transplants, with a high rate of clear grafts at 5 years in low-risk eyes. Risk of rejection is higher with blood vessels in the cornea, previous failed grafts or active inflammation.

Prevention

• Never sleep, swim or shower in contact lenses, and never rinse lenses or cases with tap water.
• Wear protective eyewear for grinding, hammering, gardening and chemicals.
• Seek same-day care for a painful red eye, especially if you wear lenses.
• Take antiviral medicines as advised if you have had herpes eye disease.

Frequently asked questions

Can a corneal scar heal on its own?

Faint scars often fade partly over 6 to 12 months as the collagen remodels, and vision may improve. Dense scars from deep injury or infection are permanent. If a scar still affects vision after it has stabilized, lenses, laser treatment or a transplant can help.

Can a contact lens cause a corneal scar?

Not directly, but contact lens wear is the biggest risk factor for corneal infections in developed countries. An infection under a lens can form an ulcer that leaves a scar. Sleeping in lenses raises the risk many times. Good hygiene and never exposing lenses to water greatly reduce it.

Does corneal scarring cause blindness?

It can. Corneal opacity is one of the leading causes of blindness worldwide, mainly from trachoma, untreated infections, vitamin A deficiency and injuries. In most cases in the US, scars cause blur or glare rather than blindness, and treatment can restore useful vision.

Can LASIK fix a corneal scar?

Usually not. LASIK reshapes the cornea under a flap and does not remove scars. A different laser treatment, phototherapeutic keratectomy, can remove scars near the surface. Some people later have refractive surgery once the scar is treated, but this needs careful assessment.

How successful is a corneal transplant for scarring?

For a scar in an otherwise healthy eye, success rates are high, and most grafts stay clear for many years. Results are poorer when the cornea has blood vessels, active inflammation or previous graft failures. Vision may take months to settle, and glasses or contact lenses are often still needed.