How the cornea scars
The cornea is transparent because its collagen fibers are arranged in a precisely ordered lattice. When deeper layers are injured, the healing tissue lays down collagen in a disordered pattern that scatters light, producing a scar. The surface epithelium heals without scarring; damage that reaches Bowman's layer or the stroma can scar. Bacterial and herpetic infections, penetrating and chemical injuries, severe abrasions, long standing inflammation and some surgical complications are the usual causes.
How a scar affects vision
Two mechanisms. The scar itself blocks and scatters light, causing haze and glare. And the healing changes the cornea's shape, creating irregular astigmatism that glasses cannot correct, because glasses can only correct a regular difference between two meridians. A patient with a central scar often sees better through a pinhole or a rigid contact lens than through any pair of glasses, which is the clue that the surface irregularity, not the opacity, is the main problem.
Assessment
The slit lamp shows the scar's size, position and depth. Corneal topography maps the irregularity it causes. Anterior segment OCT measures how deep it extends, which determines whether a surface treatment could remove it. A rigid contact lens trial shows how much vision could be recovered by neutralizing the surface. These findings together decide the treatment.
Treatment options
- Observation, for scars that are peripheral or not affecting vision
- Specialty contact lenses, particularly scleral lenses, which vault over the irregular surface and give the best vision for most scarred corneas without surgery
- Phototherapeutic keratectomy (PTK), an excimer laser treatment that removes shallow scars in the anterior stroma and smooths the surface
- Partial thickness transplantation (lamellar keratoplasty) for deep central scars, replacing only the affected layers
- Full thickness transplantation in the rare case where all layers are involved
Preventing further scarring
Prompt treatment of infections and injuries limits the depth of scarring. Herpetic disease is suppressed with long term antivirals in patients with recurrent episodes. Contact lens hygiene prevents the infections that are the most common cause of new scars in younger patients.
Is this right for your eyes?
Nothing on this page is a diagnosis. Whether this is what is affecting your vision is decided by a full examination at one of our 4 offices: Pasadena, Huntington Beach, Woodland Hills and Beverly Hills.
About this content: This page was written with the assistance of AI tools and reviewed for medical accuracy by Dr. Bavand Youssefzadeh, DO. It is general information, not medical advice, and does not replace an eye examination. Individual results vary. Read our medical disclaimer.
