Suppurative keratitis (corneal ulcer)

Suppurative keratitis (corneal ulcer) . Corneal ulcer is the process of corneal infiltration with loss of substance, caused by an invasion of microorganisms into the cornea with biomicroscopic characteristics and a clinical picture depending on the causal germ accompanied by general symptoms.

It is characterized by presenting three periods in its evolution: inflammatory infiltration ( keratitis period ), suppuration (tissue loss due to necrosis ) and scarring . These generally arise from an infectious complication of previous corneal epithelial lesions , for example: traumatic, exposure, neurotrophic, etc. There are also germs that cause corneal ulcers without previous injury.

Ulcers leave scars that affect visual acuity and, if pierced, can cause endophthalmitis due to the entry of germs into the eye , leading to loss of the eyeball .

Summary

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  • 1 Causes and main clinical manifestations
  • 2 Complications
  • 3 Diagnosis
  • 4 Source

Causes and main clinical manifestations

Numerous microorganisms can invade the cornea and damage it, mainly bacterial infections, either by gram-positive ( Gam + ) or gram-negative ( Gram- ), fungal infections such as Candida and viral infections, the most common herpes simplex , among which those caused by germs capable of producing ulcers. in this, although without affecting the corneal epithelium, for example: Neisseria meningitidis , Neisseria gonorrhoeae and Corinebacterium diphteriae , in which cases the diagnosis is difficult.

The main endogenous factors favoring the appearance of corneal ulcers are eyelid disorders (entropion, blepharitis and lagoftalmus), lacrimal (lacrimal hyposecretion and dacryocystitis), conjunctival (trachoma, pemphigoid eye) and corneal (herpetic ulcer, keratopathia). trigeminal), as well as the systemic factors where alcoholism, coma, diabetes, immune disorders and malnutrition, among others, intervene. Also, the predisposing factors in the appearance of this condition must be taken into account, among which stand out: chronic infection of the ocular annexes, underlying diseases of the cornea (herpetic keratitis, bullous keratopathy, trauma), dry eye, neurotrophic keratopathy by exposure,

The structural harmony of the eye and its annexes is essential to guarantee good health, therefore, whenever there is a triggering factor for any eye disorder, there is a risk of corneal ulcer or other corneal condition, which is aggravated , if it is combined with decompensated systemic diseases that in turn will affect the course and unfavorable evolution of eye conditions.

Corneal ulcers of bacterial origin are characterized by being irregularly acute with a thick mucopurulent exudate, diffuse liquefaction necrosis and ground glass appearance. There are germs that generally cause its appearance, such as: Staphilococcus aureus , Streptococcus pneumoniae , Pseudomonas sp. and Enterobacteriaceae , among others. These ulcers are very serious, in this environment they present with torpid evolutions, there is not always a response to the initial therapy and they evolve in more than 21 days. The most frequent complications that appear during its development are ocular hypertension, descemetocele, corneal lysis and perforation. Depending on the biomicroscopy of the anterior segment inslit lamp and fluorescein staining , the clinical diagnosis and the presence of one or the other germ can be inferred.

  • Streptococcus pneumoniae: associated with eye trauma. The clinical manifestations can be early and intense when the edge of the ulcer, undermined and covered with tissue, protrudes above it; the reaction in the anterior chamber is acute, there is frequent perforation, the presence of a hypopyon, oval suppuration of the yellowish-white stroma and increased opacity surrounded by a relatively clear cornea.
  • Staphilococcus aureus: It presents with a round or oval ulcer, sometimes diffuse, micro-accesses in the anterior stroma that are connected by stromal infiltrates. Its development is superior in depth. Sterile hypopyon and endothelial plaques are common.
  • Pseudomonas sp: require previous corneal injury. They cause mucopurulent discharge to adhere to the surface of the ulcer. They spread rapidly, double in size in 24 hours, and perforate in 2-5 days. They can be central or paracentral, round with a gelatinous appearance and move with the movement of the eyelids. They produce necrosis and dense infiltrates of the posterior corneal stroma, endothelial plaques and hypopyon. The non-ulcerated portion of the cornea will have a diffuse grayish epithelial appearance or ground glass.

Although rare, fungal infection can have devastating effects, as they cause stromal necrosis and enter the anterior chamber through Descemet’s membrane , which is very difficult to control, due in part to the low penetration of antifungal agents. . The most frequent fungi are the filamentous Aspergillus and Candida albicans . Filamentous keratitis is common in agricultural areas and is typically preceded by ocular trauma, where organic matter ( wood or plants ) intervenes . These ulcers are described as the most serious, since they usually appear in isolation depending on the causal germ.

  • Candida albicans causes keratitis that develops characteristically, associated with a pre-existing corneal disease or in an immunocompromised patient. Its ocular characteristics are given by the antecedent of trauma with vegetal matter, which gives rise to symptoms such as: photophobiatearing , blepharospasm , decreased visual acuity , conjunctival cilia injection , chemosis and eyelid edema . Most of them are caused by Candida sp. and the Aspergillus; In addition, in advanced stages they can reach perforation. Clinically they are characterized by being high, with an irregular and dry surface with scalloped or feathery edges. In some cases, partial or total grooves, satellite opacities and endothelial plate, Wessely inflammatory ring , retrokeratic precipitates, and thick or dense hypopyon that do not displace eye movements appear.

Moreover, species of Acanthamoeba are protozoa free life that are in the air , the soil and the water sweet or salty. They exist in active form ( trophozoite ) and tente ( cyst ). The cystic form is highly resistant and capable of surviving for prolonged periods in hostile environmental conditions (chlorinated water from swimming pools, hot water from pipes and sub-freezing temperatures in freshwater lakes). Under appropriate environmental conditions, the cysts become trophozoites that produce a series of enzymes, which aid in tissue penetration and destruction.

Ulcers of viral etiology present with linear, branched and dendritic ulcers. The ends of the branches show a characteristic swollen appearance, where herpes simplex is one of the most frequent causes; They are easily diagnosed diseases and their evolution is generally favorable. In this environment, these are the ones with the best results in conventional therapy and in which, during their evolution, complications rarely appear.

Complications

There are multiple complications that accompany the evolution of corneal ulcers, and secondary ocular hypertension , descematocele and endophthalmitis stand out , despite the fact that early and timely therapy has been instituted.

Diagnosis

  • Before the suspected infectious cause, the [microbiological diagnosis]] is made by corneal scrapingand cultivation in ulcers and infiltrates.
  • When contact lensesare used , culture of the lens covers and cleaning solutions should be done; In addition, if eye medications have been received, each should be cultured.

Among the diagnostic stains are: Gram ( yeasts , bacteria ), Giemsa ( fungi , chlamydia , rickettsia and Acanthamoeba ), Calcofluor white (fungi, Acanthamoeba), Acridine orange (fungi), among others. The culture media are: Blood agar (aerobic bacteria, saprophytic fungi), Chocolate agar (Haemophilus, neisserias, Moraxella), Mannitol agar (Escherichia coli), Sabouraud agar (fungi) and Thioglycollate (aerobic and anaerobic bacteria).

 

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