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Keratitis

The keratitis is an inflammatory reaction of the corneal epithelium.

The cornea constitutes the most anterior part of the ocular outer covering, and is shaped like a spherical cap. It is made up of five layers, of which the epithelium is the most superficial, and the stroma the thickest, forming 90% of it. This area of ​​the eye does not have vessels, therefore, it must be nourished from the vessels located in the sclerocorneal limbus, the aqueous humor and the tear film that covers the external surface of the cornea. The nerve fibers that facilitate the sensations of pain and cold also come from the limbus. The main functions of the cornea are to cover the eye and act as a lens. Therefore, any irregularity in its surface will lead to the alteration of visual capacity.

Causes of keratitis

The causes that can produce keratitis are multiple, the most frequent being the following:

  • Infections, whether caused by viruses, bacteria or fungi. Among the viruses, those produced by herpes simplex viruses or herpes zoster are especially important, due to the complications that can appear if they are not treated correctly.
  • Physical agents, such as prolonged exposure to ultraviolet rays, either from the sun or from artificial lamps; or contact lens abuse.
    Drugs, such as adenosine arabinoside.
  • Allergens, such as dust mites or grasses.
  • Alterations in the characteristics of the tear, which would lead to keratoconjunctivitis sicca. Said alterations may be due to a deficit in tear volume or due to alterations in its composition.

As might be expected, the pathogenesis varies depending on the ethology. However, in most cases, the inflammatory alterations that occur damage the corneal epithelium, producing erosion of it, as occurs in superficial punctate keratitis. If this is not treated in time, not only the epithelium, but also the underlying stroma, can be affected, leading to the appearance of ulcers.

In the natural history of corneal ulcers, three stages are distinguished: infiltration phase, healing phase and healing phase.

  1. During the infiltration phase, the leukocytes penetrate the cornea, and edema appears, which favors the necrosis of the corneal tissue. If the entire thickness of it is destroyed, what is called a corneal perforation will appear. Said perforation can lead to clinical improvement, probably due to the arrival of defensive elements from the aqueous humor. However, in most cases, it will lead to multiple complications, such as the appearance of an external fistula that allows the aqueous humor to escape and the appearance of intraocular infection; the development of cataracts or synechiae.
  2. The healing phase can occur, either because it increases the host’s defenses or because the corneal destructive process ceases.
  3. Finally, the healing period occurs, in which not only a new epithelium appears, but also the replacement of necrotic tissue by collagen tissue, which is not transparent, thus altering the quality of vision.

Symptoms

In general, the following symptoms and signs will always appear:

  • Loss of transparency of the cornea, which if located in the visual axis, will cause loss of vision and glare.
  • Irritation of the corneal nerves, which will result in the appearance of pain and a secondary ciliary reaction, which will be expressed by the appearance of ciliary injection, that is, increased vascularity near the limbus, photophobia, involuntary contraction of the palpebral muscles and tearing.
  • If ulcers appear, the same symptoms, but more marked, in addition to the complications mentioned above.

In the case of herpes simplex keratitis, two stages are distinguished: primary infection and recurrences.

  • The primary infection usually presents with a banal keratoconjunctivitis, accompanied by a catarrhal picture and the typical herpetic vesicles around the eye or lip.
  • Recurrences are characterized, above all, by the appearance of dendrite-shaped ulcers, pain less intense than in bacterial keratitis.

How is it diagnosed?

The diagnosis is made from the clinical data, having special importance for the differential diagnosis with conjunctivitis , the existence of ciliary injection. This differs from conjunctival hyperemia typical of conjunctivitis, in that it is more purplish, closer to the limbus, does not disappear after instillation of neosionephrine and does not move when the conjunctiva is moved with a swab. On the contrary, conjunctival hyperemia is characterized by being reddish, more external, disappears with the instillation of neosinephrine and moves with the conjunctiva.

To observe the lesions produced in the cornea, we use magnifying glasses or slit lamps, as well as fluorescein, which is a dye that stains the defects of the epithelium greenish-yellow when illuminated with a blue light.

Keratitis treatment

Treatment of superficial punctate keratitis is carried out depending on the etiology:

  • The disease caused by adenovirus (the most common type of viral conjunctivitis) resolves spontaneously within three weeks.
  • The caused by exposure to ultraviolet light is treated with cycloplegics, such as atropine, antibiotic ointment and occlusion for 24 hours.
  • If the cause is the prolonged use of contact lenses, antibiotics are administered and the eye is avoided, to avoid the risk of serious infections.

If the keratitis is due to the administration of drugs, they should be suppressed.

  • The treatment of corneal ulcers is based on:
  • Eliminate any mechanical or toxic factor that perpetuates the ulcer.
  • Fight against infection, both by applying antibiotics to the eye, orally or venously.
  • Use of cycloplegics such as atropine, which paralyze the ciliary muscle and eliminate the associated ciliary response.
  • If the ulcers are already healed, with residual lesions affecting vision, a keratoplasty can be performed.

Avoiding keratitis

In the case of infections, it is enough to maintain basic hygiene rules, such as avoiding touching your eyes with dirty hands.

To avoid keratitis caused by allergens, it will be necessary to avoid exposure to them, although this is not always possible to achieve completely, as in the case of exposure to dust.

When drugs capable of damaging the cornea are used, follow-up by the ophthalmologist will be necessary for the duration of the treatment. In addition, you should avoid direct exposure to ultraviolet light, through the use of sunglasses, as well as not overuse the use of contact lenses.

Whenever there is the slightest eye condition, a doctor should be consulted, given the fragility of the eye; however, it will be especially important to consult in the event that eye redness appears, especially around the limbus; eye pain, blurred vision or discharge.

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Hello Readers, I am Nikki Bella a Psychology student. I have always been concerned about human behavior and the mental processes that lead us to act and think the way we do. My collaboration as an editor in the psychology area of ​​Well Being Pole has allowed me to investigate further and expand my knowledge in the field of mental health; I have also acquired great knowledge about physical health and well-being, two fundamental bases that are directly related and are part of all mental health.

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