Corneal ulcer

Corneal ulcer heals in two ways: by migration of the surrounding epithelial cells, followed by mitosis (division) and the introduction of blood vessels from the conjunctiva . Small superficial ulcers heal quickly in the first way. However, large or deep ulcers often require the presence of blood vessels to supply inflamed cells. White blood cells and fibroblasts produce granular tissue and then scar tissue, effectively healing the cornea.

Corneal ulcers are a common disease of the human eye and are caused by injuries, in particular, herbal substances, as well as chemical injuries, contact lenses and infections. Other causes of corneal ulcers may include entropion , dysthiasis , corneal dystrophy , and keratoconjunctivitis (dry eye).

Many microorganisms cause an infectious corneal ulcer. Among them are bacteria, fungi, viruses, protozoa, and chlamydia:

• Bacterial keratitis causes Staphylococcus aureus , Streptococcus viridans , Escherichia coli , Enterococci , Pseudomonas, Nocardia, Neisseria gonorrhoeae and many other bacteria.
• Fungal keratitis causes deep and serious corneal ulcers. Its causes may include aspergil, fusarium , candida , as well as Rhizopus, mucor and other mushrooms. A characteristic feature of fungal keratitis is a slow onset and gradual progression, where there are much more signs than symptoms. Small satellite lesions around the ulcer and usually marked suppuration are a common feature of fungal keratitis.
• Viral keratitis causes ulceration of the cornea. This is most often caused by the herpes simplex virus , herpes zoster and adenoviruses . It can also be caused by coronaviruses and many other viruses. The herpes virus causes dendritic ulcers , which can be repeated throughout life.
• Infections with protozoa, such as acanthamoeba keratitis, are characterized by severe pain and are associated with the use of contact lenses when swimming in pools.
• Chlamydia trachomatis can also contribute to the development of corneal ulcers.

Superficial ulcers include loss of part of the epithelium. Deep ulcers pass through or through the stroma and can lead to severe scarring and perforation of the cornea. Descemetoceles (hernia of the descemetic membrane of the eye) occurs when an ulcer passes through the stroma. This type of ulcer is especially dangerous and can quickly lead to perforation of the cornea if started.

The location of the ulcer to some extent depends on its cause. Central ulcers, usually caused by trauma, dry eyes, exposure to facial paralysis or exophthalmos , entropion , severe dry eyes and trichiasis (eyelash inversion), can cause ulceration of the corneal periphery. Immuno-mediated eye disease can cause ulcers at the border of the cornea and sclera . These include rheumatoid arthritis, rosacea , systemic sclerosis, which lead to a special type of corneal ulcer called Murena ulcer (corroding corneal ulcer) ^[3] . It has a circular crater like a depression of the cornea, only inside the limb, usually with an overhanging edge.

Symptoms

Corneal ulcers are extremely painful due to exposure to the nerve, and can cause lacrimation, strabismus, and loss of vision. Signs are also anterior uveitis , miosis (small pupil), Tyndall effect (protein in the intraocular fluid) and redness of the eyes. The axon reflex may be responsible for the formation of uveitis - stimulation of pain receptors in the cornea as a result of the release of inflammatory mediators such as prostaglandins , histamine and acetylcholine . Sensitivity to light is also a symptom of corneal ulcer.

Diagnostics

Diagnosis is by direct observation under an enlarged slit lamp to identify corneal ulcers. The use of a fluorescein spot that covers the open stroma of the cornea and appears green, helping to determine the boundaries of the corneal ulcer, may reveal additional details of the surrounding epithelium. Herpes simplex ulcer shows a colored typical dendritic structure. Rose-Bengal dye is also used for supra-vital (beyond the life cycle ^[4] ) staining purposes, but this can be very irritating to the eye. With a hernia of the Descemetic membrane of the eye, the Descemetic membrane will protrude forward and after staining will look like a dark circle with green borders, since it does not absorb the stain. By filming the cornea and examining the spots under the microscope, like Gram's and pre-treated KOH, bacteria and fungi can be detected, respectively. In some cases, it may be necessary to isolate pathogens during microbiological culture tests. Other tests that may be needed are Schirmer ’s dry keratoconjunctivitis test and facial nerve function analysis for facial paralysis.

Treatment

A correct diagnosis is essential for optimal treatment. Bacterial corneal ulcers require intensive firming antibacterial therapy to treat infection. Fungal ulcers of the cornea require intensive use of topical antifungal agents. Herpes virus ulceration of the cornea can be treated with antiviral drugs, like topical acyclovir ointment, drop by drop at least five times a day. At the same time, maintenance therapy as pain medication, including topical cycloplegs like atropine or homatropin, to expand the pupil and thereby stop the ciliary muscle spasms. Superficial ulcers heal in less than a week. Deep ulcers and herniation of the Descemet sheath may require conjunctival transplantation or a conjunctival pocket, soft contact lenses, or corneal transplantation . Proper nutrition is recommended, including protein and vitamin C. In cases of keratomalacia, where corneal ulceration is due to a lack of vitamin A, vitamin A is administered orally or intramuscularly. Means that are generally contraindicated in corneal ulcers - topical corticosteroids and anesthetics - they should not be used for any type of corneal ulcer, since they interfere with healing, I can lead to superinfection with fungi and other bacteria and often complicate the condition.

Persistent corneal ulcers are superficial ulcers that heal poorly and tend to recur. They are also known as painless ulcers or Boxer ulcers . They are presumably caused by a defect in the basement membrane and the absence of hemidesmosome attachments. They are recognized by the destruction of the epithelium that surrounds the ulcer and the light posterior crust. Persistent corneal ulcers are most often seen in diabetics and they often later affect the other eye. They are similar to Kogan’s cystic dystrophy .

Treatment

Topical strengthening antibiotics are used at hourly intervals to treat infectious corneal ulcers. Cycloplegic eye drops are used to relax the eyes. Painkillers are given as needed. The free epithelium and the base of the ulcer should be scraped off and sent for a sensitive culture study to determine the pathogenic organism. This helps in choosing the appropriate antibiotic. Complete healing takes from several weeks to several months.

Treating persistent corneal ulcers can take a long time, sometimes months. In the case of progressive or non-healing ulcers, surgical intervention by an ophthalmologist with corneal transplantation may be necessary to preserve the eye. For all corneal ulcers, it is important to exclude predisposing factors such as diabetes mellitus and immunodeficiency.

A diminishing ulcer is a type of corneal ulcer involving progressive loss of stroma in a decreasing tissue. This is most often seen in Pseudomonas infections, but it can be caused by other types of bacteria or fungi. These infectious agents produce protease and collagenase, which destroy corneal stroma. Complete stromal loss can occur within 24 hours. Treatment includes antibiotics and collagenase inhibitors such as acetylcysteine . Surgery in the form of corneal transplantation (penetrating keratoplasty) is usually necessary to save the eye.