**5. Clinical features**

The development of a bacterial corneal inflammation may occur as a number of clinical features. We should keep in mind that in BK signs are more common than symptoms. The common symptoms of bacterial ulcers include worsening of vision, pain, foreign body sensation, redness, watering, mucopurulent or purulent discharge, and photophobia. The various signs include lid edema, blepharospasm, mucopurulent or purulent discharge, conjunctival hyperemia and chemosis, circumcorneal congestion, epithelial defect, stromal edema and infiltrate, full-thickness infiltrate, Descemet membrane folds, hypopyon, exudates in the anterior chamber, anterior uveitis, posterior synechiae, muddy iris, and small ischemic pupil [28].

In most cases of BK, there is an epithelial defect with hyperemia and exudate mucopurulent discharge accompanied by sudden severe eye pain and photophobia. Corneal infiltrate, which causes loss of tissue transparency, as a result leads to decreased visual acuity. Inflammatory exudate may also occur in the anterior chamber of the eye and penetrate deep into the eye tissues, including the posterior segment of the eye. Such an acute course of infection with the involvement of the posterior segment of the eye occurs mainly in people with impaired immune response, using long-term steroid therapy, after eye surgery or trauma, especially after trauma with organic material. The course of the disease, as well as ocular signs and symptoms depends on the virulence of the pathogen. The increased severity of the corneal ulcer the poorer treatment results. Depending on the severity of signs and symptoms, as well as the rate of progression, BK inflammation can be divided into mild, moderate, and severe. Mild corneal ulcers <2 mm in size with the depth of the ulcer <20% or 100 μm corneal thickness that may be accompanied by superficial infiltrates near the ulcer. Moderate corneal ulcers range between 2 and 5 mm in size, depth of 20–50% (100–275 μm) of the cornea, accompanied by dense infiltrates, including the mid stroma. Severe ulcers ≥5 mm, with a depth of more than 50% (>275 μm), accompanied by dense infiltrates, include the deep layers of the corneal stroma [11, 22, 29].

The clinical features of corneal infiltration also depend on the type of pathogen that caused BK. Bacterial corneal ulceration can occure very often in the form of a single corneal infiltrate with a sharp epithelial demarcation, with a dense, purulent infiltration of the corneal stroma with indistinct borders accompanied by corneal edema. The main factors, which favor the development of bacterial ulcers with hypopyon, include the host tissue's resistance, as well as the bacteria's virulence. They occur generally in old, debilitated, malnourished, and with immunodeficiency patients.

BK caused by gram-positive bacteria, especially cocci, is characterized by a benign course with limited tissue infiltration located superficially with slight corneal swelling. They occur in patients with dry eye syndrome, blepharitis, and rosacea. They are

## *Bacterial Keratitis DOI: http://dx.doi.org/10.5772/intechopen.113365*

characterized by slow progression, but if left untreated, they can even lead to corneal perforation. Sufficient prophylaxis is the treatment of ocular surface disorders [28]. Gram-negative bacteria produce enzymes that quickly damage tissue. They are characterized by rapid progression and the lack or delayed implementation of treatment leads to complete destruction of the cornea, sclera, iris, and even loss of the eyeball. *Pseudomonas aeruginosa* usually progresses rapidly with stromal melt and necrosis, ring infiltrate, hypopyon, anterior chamber cells and flare, endothelial plaque, and later descemetocele formation or perforation [28, 30]. *Pseudomonas aeruginosa* is more common in CL-wear patients as this bacterium becomes more pathogenic in biofilm associated with the contact lens [13, 25, 26, 30]. Some bacteria cause characteristic changes in the corneal stroma, which is helpful in making the diagnosis. Streptococci cause limited infiltrates, the descent of which is crystalline keratopathy. Gram-negative bacteria, such as *Klebsiella*, *Proteus*, *Listeria*, *Streptococcus*, and *Pseudomonas*, favor the appearance of the characteristic annular shape infiltrates of the cornea [28].
