Keratoconus – its relationship with ocular surface diseases and meibomian gland dysfunction

Keratoconus is a corneal disease characterized by the curvature of the cornea into a cone-like shape and hence the name of the disease, this may lead to vision distortion, light sensitivity and astigmatism. Keratoconus has been associated with several ocular surface disorders, including ocular surface disease (OSD) and meibomian gland dysfunction (MGD). This article is intended to give background to the department and show the relationship between keratoconus, OSD and MGD.

Understanding keratoconus

Keratoconus is usually a bilateral (affecting both eyes) and asymmetric condition that manifests itself during puberty and progresses until the third or fourth decade of life. The cornea, in its normal state, is the clear front surface of the eye, which acts like a window that controls and focuses light into the eye. When keratoconus occurs, the cornea weakens, losing its dome shape. The irregular shape and variable refractive index affect the eye's ability to focus light, which leads to significant vision impairment.

Ocular surface disease and keratoconus

Ocular Surface Disease (OSD) is a general term for conditions affecting the surface of the eye, including dry eye, allergies and eyelid inflammation. It is a multifactorial disorder of the tear film and the surface of the eye surface, Zatz causes discomfort in the eyes, visual disturbances and possible damage to the eye surface.

Evidence suggests that OSD often coexists with keratoconus. Corneal irregularities and subsequent changes in tear film distribution associated with keratoconus can cause people to develop OSD. The main symptom of the condition, dry eyes, is due to reduced stability of the tear film and faster evaporation of the tears. This irregularity causes frictional damage during blinking, which leads to nerve damage and cause discomfort, redness and inflammation.

It is also worth noting that contact lens use, a common treatment for patients suffering from keratoconus astigmatism, may worsen OSD due to irritation and increased tear evaporation. This mutual relationship requires comprehensive management that addresses both conditions.

Meibomian gland dysfunction and keratoconus

Meibomian gland dysfunction (MGD) is a chronic condition characterized by obstruction and altered secretion of the meibomian from the meibomian glands in the eyelids. Meibomian glands produce an oily substance that slows the evaporation of the tear film, maintaining the integrity of the eye surface.

The relationship between keratoconus and MGD is not as well known as that between keratoconus and OSD, but studies indicate a higher incidence of MGD in keratoconus patients. This relationship could be due to the common inflammatory aspect between these conditions, although further studies are required to establish in depth the underlying mechanisms.

In keratoconus, the altered corneal structure may lead to instability of the tear film and subsequently to a higher rate of tear evaporation. The loss of the protective tear film exposes the surface of the cornea to the environment, causing irritation and inflammation. This persistent inflammation can affect the eyelids, contributing to MGD. In turn, MGD exacerbates tear film instability, perpetuating a cycle of inflammation and further compromising corneal health.

Comprehensive management of keratoconus, OSD and MGD

The complex relationship between keratoconus, OSD and MGD indicates the need for a comprehensive approach in their treatment. The treating team should consider the interrelationships between these conditions when developing the treatment strategy.

In cases of keratoconus with OSD or MGD at the same time,

Treatment options include plugs to block the tear drainage opening in the eyelid, anti-inflammatory agents or tear-stimulating drugs for OSD. Warm compresses, eyelid hygiene, and oral or topical medications are helpful in managing MGD. For keratoconus and depending on the progression of the disease, corneal crosslinking, special contact lenses, and in some cases, a corneal transplant are treatment options for keratoconus.

In conclusion, keratoconus, ocular surface disease, and meibomian gland dysfunction share common characteristics that reinforce each other, escalating the progression and severity of each condition. More tests are needed to understand the mechanisms and thus we can improve the treatment methods.

Credit: Dr. Assaf Freeman