Ocular secretion testing is used to diagnose, monitor and evaluate the treatment of patients with various ocular infections such as blepharitis, conjunctivitis, tonsillitis and keratitis.
Eye infections can be caused by a variety of microorganisms. Exogenously derived microorganisms can be introduced into the eye through the hands, contact lenses, traumatic injury to a foreign body, after surgery or by contagion from neighboring sites.
Mild eye infections include conjunctivitis and blepharitis (inflammation of the eyelids). Conjunctivitis can occur in conjunction with an infection of the eyelid (eyelid conjunctivitis) or corneal (corneal conjunctivitis). Less common and more serious infections include keratitis (inflammation of the cornea) and intraocular (infection inside the eye). Bloodborne dispersal from other parts of the body can also occur. Other ocular infections include lacrimal adenitis (lacrimal gland inflammation), lacrimal sac (lacrimal sac inflammation), lacrimal duct inflammation and colonic cellulitis. Ocular infections that occur in the first 4 weeks of life caused by Chlamydia trachomatis or Neisseria gonorrhoeae are called neonatal eye.
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 can be acute or chronic. Conjunctivitis is the most frequently infected ocular tissue and infectious conjunctivitis is one of the most common causes of redness of the eyes. 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 quite difficult. Conjunctivitis caused by Neisseria species is rare in developed countries. The most important eye pathogen in this genus is Neisseria gonorrhoeae (gonococcus). In adults it is associated with concomitant genital infection. In neonates, it is a very important cause of neonatal eye, 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. Congenital conjunctivitis and trauma are caused by various serotypes of Chlamydia trachomatis. The trachoma is associated with serotypes A-C. It is commonly found in rural areas, while conjunctivitis with enclosures is associated with D-K serotypes and is a characteristic of developed urban areas. The most common causes of viral conjunctivitis are adenoviruses.
Acanthamoeba can cause severe keratitis, usually in contact lens wearers or after injury to the eye. This protozoan can be isolated after corneal abrasion as well as contact lenses and storage pockets.
Colonic cellulitis is an infection of the optic nerve tissues. It can be caused by trauma, surgery or an extension of the sinus infection. It is a serious infection and can cause blindness, septic cord thrombosis or intracranial infection. The most common pathogens in adults are S. aureus, Streptococcus and anaerobes. In children the most common germ is H. influenzae, but the strain b is rare. Streptococci, Staphylococci, Peptostreptococci and P. aeruginosa can cause necrosis.
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-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 interpreted in relation to each individual case and family history, clinical findings and the results of other laboratory tests and information. Your personal 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 we contact your doctor to get the best possible medical care.