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Ocular Surface: Conjunctiva and Cornea


The cornea is the outer layer of the eye, it is transparent, curvilinear and acts as the first lens that encounters light when it enters our eyeball. 

For the correct function of the cornea, it must remain transparent and it must have an adequate curvature so that it has good optical refraction properties. 

The cornea performs defensive functions against trauma and infections, protecting the eye from germs and other external risk factors. Many acquired or congenital diseases affect it.

Therefore, the cornea fundamentally helps protect the eye orbit, the eyelid, tears and the sclera (the white part of the eye).

In addition to the transparency of the cornea, the visual capacity of each person depends on it, which is why we can consider the cornea as the first lens of the optical system of our eyes, since a deformity or lack of transparency will cause a bad image on the retina.

Therefore, one of its main functions is to focus the images, adapting to near and far vision.

Causes of damage to the cornea

The most frequent are:
{Arañazos en la córnea}

Scratches on the cornea

Result of an alteration or loss of cells in the outer layer of the cornea.

{Lesión Química}

Chemical Injury

Result from harmful chemical coming into contact with the eye.

{Abuso lente de contacto}

Contact lens abuse

Caused by misuse of contact lenses, or result of not changing them after 6 months.

{Objetos Extraños}

Strange objects

Eye contact with foreign agents: foreign body sensation, pain, blurred vision.

{Exceso de Luz}

Excess Light

Excess ultraviolet rays in the eye, Direct sunlight, Artificial light, light flashes.



Infections caused by fungi, viruses or bacteria.

Corneal diseases

There are many diseases of the cornea, both hereditary and acquired. Due to their importance we can highlight the following:

Keratoconus is a disease of the cornea where thinning and deformity of the cornea itself occurs, affecting the quality of vision in a way that can be mild to even very severe for the patient.

Keratoconus means cone-shaped cornea, and although the exact cause of the disease is unknown, some genetic and environmental factors have been identified, the most important being eye rubbing with a medical history of allergy.


Conjunctivitis is inflammation of the conjunctiva, which is the almost transparent membrane that covers the white part of the eye (called the exclera or sclera).


It is a disease of the external part of the eye (eyelids, conjunctiva, cornea and tears) that occurs when it loses its function of protecting, lubricating and improving vision, causing discomfort, inflammation and altered vision.

Decreased lubrication of the eyes, called dry eye syndrome, is a very common disease in adults, which can affect up to 30% in those over 40 years of age (especially women).


Blepharitis, or inflammation of the eyelids, is a fairly common disorder that affects the eyelid area where the eyelashes grow. The most frequent symptoms include: watery eyes, red eyes, feeling of sand, burning or stinging in the eyes, peeling and dandruff on the eyelashes, sensitivity to light, loss of eyelashes, among others.

Blepharitis is a long-term disorder that is not easy to treat. Although in general it does not cause a significant threat to vision, the symptoms can significantly affect the quality of life of patients.

For treatment, your ophthalmologist will indicate hygienic measures, local heat and, depending on the case, antibiotics or anti-inflammatory agents may be prescribed. Because a definitive cure for the condition is not possible, the objective of therapy lies in controlling symptoms, improving the quality of life of patients and avoiding the appearance of complications such as corneal alterations or severe eyelid infections. 


Pterygium is a growth of the conjunctiva and fibrovascular tissue that occurs as a result of exposure to UV rays and repetitive microtrauma (dust, wind and chronic irritants). The conjunctiva has its anatomical limit at the corneal limbus (edge of the cornea), being called Pterygium when it exceeds this limit, generating a “fabric” over the cornea.