Eye discharge testing is used to diagnose, monitor, and evaluate treating patients with ocular infections such as blepharitis, conjunctivitis, orbital cellulitis, and keratitis.
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A variety of microorganisms can cause eye infections. Exogenously derived microorganisms can be introduced into the eye through the hands, contact lenses, injury from a foreign body, after surgery or by contagion from neighboring sites.
Infections
Mild eye infections include conjunctivitis and blepharitis (inflammation of the eyelids). Conjunctivitis can occur in conjunction with an infection of the eyelid (blepharoconjunctivitis) or cornea (keratoconjunctivitis). Less common and more severe infections include keratitis (inflammation of the cornea) and endophthalmitis (infection inside the eye). Blood spread from other parts of the body can also occur. Other eye infections include inflammation of the tear gland, dacryocystitis (inflammation of the lacrimal sac), inflammation of the lacrimal ducts, and orbital cellulitis. Eye infections that occur in the first 4 weeks of life and are caused by Chlamydia trachomatis or Neisseria gonorrhoeae are called neonatal ophthalmia.
Blepharitis
Blepharitis is usually due to:
- Staphylococcus aureus
- Staphylococcus epidermidis
- Corynebacterium species
- Propionibacterium acnes
However, these microorganisms can also be isolated from the eyes of normal individuals.
Conjunctivitis
Conjunctivitis can be acute or chronic. Conjunctivitis is the most frequently infected ocular tissue, and infectious conjunctivitis is one of the most common causes of eye redness. The most common bacterial causes of conjunctivitis are:
- Staphylococcus aureus
- Streptococcus pneumoniae
- Haemophilus influenzae
Less common causes include Group A, C, and G (Lancefield) Streptococcus, Neisseria cinerea, Propionibacterium acnes, species of the genus Moraxella, and other Gram-negative microbes as well as anaerobic microbes such as the genera Eubacterium and Peptostreptococcus. Moraxella catarrhalis causes acute conjunctivitis, and Moraxella lacunata causes chronic infection. However, many of these organisms can also be isolated from the surrounding (skin) areas, so interpreting their presence is problematic. Conjunctivitis caused by Neisseria species is rare in developed countries. The most crucial eye pathogen is Neisseria gonorrhoeae (gonococcus). In adults, it is associated with concurrent genital infection. In neonates, it is a significant cause of neonatal ophthalmia, which can cause blindness if left untreated. Neisseria meningitidis has also been implicated in acute conjunctivitis.
Neonatal conjunctivitis is caused by the pathogens commonly found in adults and in addition by microorganisms:
- Neisseria gonorrhoeae
- Haemophilus parainfluenzae
- Group B Streptococcus and Enterococci
- Enterobacteriaceae, e.g., Klebsiella pneumoniae and Proteus mirabilis
- Pseudomonas aeruginosa
Chlamydial and viral conjunctivitis
Chlamydial and viral conjunctivitis can also occur. Different serotypes of Chlamydia trachomatis cause inclusion conjunctivitis and trachoma. Trachoma is associated with serotypes A-C and is usually found in rural areas. In contrast, inclusion conjunctivitis is associated with serotypes D-K and is a characteristic feature of developed urban areas. The most common causes of viral conjunctivitis are adenoviruses.
Acanthamoeba species
Acanthamoeba can cause severe keratitis, usually in contact lens wearers or after eye injury. This protozoan can be isolated after corneal abrasion, as well as contact lenses and storage pockets.
Orbital Cellulitis
Orbital cellulitis is an infection of the tissues of the eye socket. It can be caused by trauma, surgery, or the extension of a sinus infection. This severe infection can cause blindness, septic thrombosis of the cavernous sinus, or intracranial infection. The most common adult pathogens are S. aureus, Streptococci, and anaerobes. The most common microbe in children is H. influenzae, but B strain is rare. Streptococci, Staphylococci, Peptostreptococci and P. aeruginosa can cause necrosis.
Important Note
Laboratory test results are the most critical parameter for diagnosing and monitoring all pathological conditions. 70% and 80% of diagnostic decisions are based on laboratory tests. Correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased."
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be analyzed based on each case and family history, clinical findings, and other laboratory tests and information. Your physician should explain the importance of your test results.
At Diagnostiki Athinon, we answer any questions you may have about the test you perform in our laboratory and contact your doctor to ensure you receive the best possible medical care.
