The exact cause of keratoconus is unknown. There are many theories based on research and its association with other conditions. However, no one theory explains it all and it may be caused by a combination of things.
It is believed that genetics, the environment and the endocrine system all play a role in keratoconus.
- One scientific view is that keratoconus is developmental (i.e., genetic) in origin because in some cases there does appear to be a familial association. From the presently available information there is less than a one in ten chance that a blood relative of a keratoconic patient will have keratoconus. The majority of patients with keratoconus do not have other family members with the disease. Some studies show that keratoconus corneas lack important anchoring fibrils that structurally stabilize the anterior cornea. This increased flexibility allows that cornea to “bulge forward” into a cone-shaped appearance.
- Eye Rubbing: Keratoconus corneas are more easily damaged by minor trauma such as eye rubbing. Poorly fit contact lenses (that rub against the irregularity of the KC cornea) have been suggested as a possible cause of keratoconus; this has not been proven and remains questionable.
- Allergies: Many who have keratoconus report vigorous eye rubbing and also have allergies (which cause eye itching and irritation, leading to eye rubbing), however the link to allergic disease also remains unclear. A higher percent of keratoconic patients have atopic disease than the general population. Disorders such as hay fever, eczema, asthma, and food allergies are all considered atopic diseases. Those with KC are advised to avoid eye rubbing as much as possible.
- Oxidative Stress: Some studies indicate an abnormal processing of the superoxide radicals in the keratoconus cornea and an involvement of oxidative stress in the pathogenesis of this disease. Keratoconus corneas lack the ability to self-repair routine damage easily repaired by normal corneas. Like any tissues in the body, the cornea creates harmful byproducts of cell metabolism called free radicals. Normal corneas, like any other body tissue, have a defense system in place to neutralize these free radicals so they don’t damage the collagen, the structural part of the cornea, weakening it and causing the cornea to thin and bulge. The keratoconus corneas do not possess the ability to eliminate the free radicals so they stay in the tissue and can cause structural damage.
- Another hypothesis is that the endocrine system may be involved because keratoconus is generally first detected at puberty and progresses during pregnancy. This theory is still controversial and has not been proven.