Bacterial keratitis is an acute inflammation of the cornea of the eye of bacterial origin. It is clinically manifested by acute pain in the eye, edema, corneal syndrome, pronounced inflammatory injection of the eyeball, the presence of mucopurulent discharge, corneal opacity, superficial or deep ulceration. Diagnosis includes biometry of the eye, microbiological examination of a smear from the cornea, confocal and endothelial microscopy, pachymetry, keratometry, keratotopography, determination of corneal sensitivity. The first priority in the treatment is local and systemic antibiotic therapy, supplemented with the use of keratoprotectors, epithelizing agents, mydriatics, with complications – surgical intervention.
Bacterial keratitis is the most common disease of the cornea of the eye. There are primary and secondary, endogenous and exogenous, superficial and deep bacterial keratitis. With a microbial lesion of the cornea, in addition to edema and purulent infiltration, there is increased vascularization, the formation of a stromal abscess, erosion and ulceration with possible tissue necrosis.
Bacterial keratitis is one of the serious problems of practical ophthalmology, since in most cases it is the cause of temporary disability, and in the future it can lead to a decrease in visual acuity and blindness.
Conditions for the development of bacterial keratitis are the presence of pathogenic microflora on the surface of the cornea and violation of the integrity of its epithelial layer. More than 80% of cases are caused by Staphylococcus aureus, Streptococcus, Pneumococcus, Pseudomonas aeruginosa. Less often, the causative agents of keratitis are E. coli, proteus, gram-negative diplococci (pathogens of gonorrhea, meningitis).
Among the exogenous risk factors are its traumatic injuries (including burns, ingestion of foreign bodies, surgical interventions), irrational use of medicines in the treatment of herpetic keratitis and corneal dystrophy, wearing contact lenses and improper storage.
Endogenous factors can contribute to the development of bacterial keratitis, which include the presence of ocular pathology in the patient (lagophthalmos, dry eye syndrome, trichiasis, corneal dystrophy, neurotrophic keratopathy, blepharitis, conjunctivitis, barley), foci of chronic infection (sinusitis, carious teeth), immunodeficiency and diabetes mellitus.
Symptoms of bacterial keratitis
The onset of bacterial keratitis is acute: the disease manifests with sharp pain in the eye, pronounced corneal syndrome (lacrimation, photophobia, blepharospasm). There is a pericorneal or mixed inflammatory injection of the eyeball caused by the expansion of superficial and deep vessels; the development of infiltrates of a yellowish or rusty hue that differ in shape, size and depth. Mucopurulent discharge from the eyes is observed, the transparency and gloss of the cornea is disturbed – it acquires a matte shade, its surface ulcerates, vision deteriorates. Bacterial keratitis has a tendency to rapid progression.
Bacterial keratitis caused by Pseudomonas aeruginosa is particularly severe, the inflammation usually spreads to the inner membranes and causes the development of a severe urgent condition.
With gonoblennorrhea, keratitis is manifested by suppuration, clouding of the epithelium, the formation of a purulent ulcer of a whitish color that spreads over the surface and into the depth of the cornea.
In the case of diphtheria keratitis, superficial and deep ulcers of dirty yellow color are found on the cornea, covered with a film, when removed, a bleeding surface is visible.
Diagnosis of bacterial keratitis does not cause difficulties. It begins with an ophthalmologist’s consultation, which includes the study of the patient’s anamnesis and complaints, an examination of the eye structures to identify a typical clinical picture, and the appointment of the necessary diagnostic studies.
Conducting eye biometrics in bacterial keratitis makes it possible to detect pathological inflammatory changes in various layers of the cornea: epithelial ulceration, infiltrates, purulent stromal inflammation, tissue edema, increased reaction of the anterior chamber of the eye (with or without hypopion), mucopurulent exudate, etc.
To study the cornea, confocal and endothelial microscopy of the cornea, pachymetry (measurement of corneal thickness), keratometry (determination of corneal parameters), keratotopography (detection of corneal distortion), determination of corneal sensitivity (corneal algesimetry) are also performed.
Laboratory diagnostics of bacterial keratitis includes microscopic and bacteriological examination of a smear from the conjunctiva and cornea (from the infiltrate, edges and bottom of the ulcer). Sowing a smear on the appropriate media allows you to determine the causative agent of bacterial keratitis and its sensitivity to antibiotics.
Differential diagnosis is carried out between different types of keratitis: bacterial, herpesvirus and fungal.
Treatment of bacterial keratitis
Due to the threat of rapid progression of bacterial keratitis, its treatment is carried out in a hospital under constant medical supervision. A favorable outcome of the disease depends on the timeliness of diagnosis and prescribed treatment.
The treatment of bacterial keratitis is based on antibacterial therapy. Instillation of eye drops containing broad-spectrum antibiotics (aminoglycosides, fluoroquinolones, cephalosporins) is prescribed. In severe cases of bacterial keratitis, injection (under the conjunctiva) and parabulbar (under the eyeball) administration of antibiotics, as well as their ingestion, is recommended. Local application of antiseptics (sulfacetamide solution), nonsteroidal anti-inflammatory drugs, glucocorticoids (dexamethasone, betamethasone) is also possible.
Treatment of bacterial keratitis in gonoblennorrhea is carried out in conjunction with a venereologist. Diphtheria keratitis is treated in an infectious hospital: in addition to antibiotic therapy, anti-diphtheria serum is necessarily injected intramuscularly, and also instilled into the eyes.
To prevent iridocyclitis and adhesions inside the eye, drugs that dilate the pupil (mydriatics) are prescribed. During the resorption of inflammatory infiltrates, keratoprotective and epithelizing agents are prescribed (r-r quinine hydrochloride, hemodialysates of the blood of dairy calves); additionally, topically and orally – antihistamines, immunocorrectors, vitamins.
With the progression of corneal ulcers, electrocoagulation, cryocoagulation or diathermocoagulation of the edges of the ulcer, quenching of the ulcer with iodine solution or diamond green is performed.
Even with timely and effective therapy, the outcome of bacterial keratitis is usually a thorn (clouding of the cornea in the form of a white spot), resulting from the development of scar tissue and vascularization of the damaged area of the cornea. Excimer laser procedure for superficial corneal scars is indicated as a surgical treatment of a cataract and restoration of visual function. The method of phototherapeutic corneal correction allows you to eliminate or significantly reduce surface opacities and corneal scars. If necessary, keratoplasty is performed.
Prognosis and prevention
The prognosis of bacterial keratitis is always serious both for vision and for the preservation of the eye.
During the transition of inflammation to other membranes of the eyeball (sclera, iris, ciliary body), keratoscleritis, keratoiridocyclitis, keratouveitis develops, and pus accumulates in the lower part of the anterior chamber (hypopion).
Due to the uneven healing of the stroma, a possible consequence of bacterial keratitis may be incorrect astigmatism, requiring further wearing of special lenses or phototherapeutic correction.
The greatest danger in the unfavorable course of bacterial keratitis is corneal perforation, which can develop into purulent endophthalmitis and panophthalmitis (inflammation of all eye tissues), lead to sympathetic ophthalmia, subatrophy (wrinkling) of the eyeball up to complete loss of vision or even the eye.
Prevention of bacterial keratitis consists in protecting the eye tissue from injuries, burns, ingress of foreign bodies, toxic substances; the use of special protective glasses during construction and repair work; careful observance of hygiene rules when wearing contact lenses. When bacterial keratitis has begun, it is very important to strictly follow the doctor’s prescriptions and recommendations in order to prevent the development of corneal ulcers and its complications.