Infections of The Eyes Mr. Mohamed Yusuf Abdi M.Sc. Medical Microbiology and Immunology The anatomy of the eye Eye • It is organ of vision and very sensitive organ so it good protected: • Most of eye structures are not exposed to the outside environment, the external structures of the eye include the eyelids, conjunctiva, sclera, and cornea, and infections of these structures can be quite common. • Ocular infections can occur in the external and internal structures of the eye. Eye Defense 1. Bony orbit 2. Eyelid (prevent entry of organisms & foreign substances). 3. Tears (an aqueous fluid, oil, and mucus) formed in the lacrimal gland, the tears contains sugars, lysozyme, and lactoferrin. These last two substances have antimicrobiaThe mucous layer contains proteins and sugars and plays a protective role properties.. Also the tears contain secretory IgA which can bind to certain pathogens and prevent them from binding to the surface of the eye. And, of course, the flow of the tear film prevents the attachment of microorganisms to the eye surface (washing away organisms). Eye Defense 4. The conjunctiva contains many lymphocytes, plasma cells, neutrophils, and mast cells, which can respond to an infection of the conjunctiva by producing antibodies and phagocytizing the offending microorganisms. 5. Normal biota of the eye: • The few bacteria that are found resemble the normal biota of the skin—namely, diphtheroids, coagulase-negative staphylococci, Micrococcus, nonhemolytic streptococci, and some yeast. Neisseria species can also live on the surface of the eye. Eye Infection • Trauma to the external structures of the eye is a common cause of infection. Other sources of infection include improperly cleaned contact lenses, which can cause a serious infection of the cornea, known as keratitis. • People who do not produce an adequate supply of tears are more likely to develop eye infections. • Infections of the internal structures of the eye are rare and can be caused microorganisms can enter the bloodstream and carry infections to the internal structures. Eye Diseases Caused by Microorganisms Blepharitis • An inflammation of the eyelid margin due to blockage of the meibomian gland. • Infection of eyelid, caused by S.Aureus and candida spp. • Hordeola (complication of blepharitis) are relatively common and appear as acute purulent papules that occur at the lid margin. • Staphylococcus aureus causes hordeola in 90–95% of the cases. • Hordeola can spontaneously resolve, or it can result in a granulomatous inflammation. Therapy and Prevention • Most hordeola drain spontaneously, especially if warm compresses are applied. • If the hordeolum is external, the lesion can be drained by lancing it or by epilating nearby lashes. • For internal hordeola, treatment includes application of warm compresses plus oral nafcillin and oxacillin. • Good hygiene of the eyelid margin should be practiced to prevent hordeola formation. Conjunctivitis • Conjunctivitis is an inflammation of the conjunctiva, often called by the common name red eye, or pinkeye. • Pinkeye, is due to this inflammatory blood vessel dilatation • It is the main & common infection of eye. • Note: a patient with allergic conjunctivitis usually complains of itchy eyes but not burning, gritty, or foreign body sensation. Signs and Symptoms • Inflammation of this tissue almost always causes a discharge. • Most bacterial infections produce a milky discharge, whereas viral infections tend to produce a clear exudate. • Dried exudate can “glue” the eyelid shut when the person wakes after an extended period of sleep, and there may be swelling of the eyelids • Some conjunctivitis cases are caused by an allergic response, and these often produce copious amounts of clear fluid as well. The pain generally is mild. • Redness and eyelid swelling are common, and in some cases patients report photophobia (sensitivity to light). Etiology A. Bacterial conjunctivitis: • Staphylococcal and streptococcal species are the most common causes of purulent conjunctivitis. • Other bacteria includes H. Influenzae, H. aegypticus, Pseudomonas, Chlamydia trachomatis [serotype A,B,C cause conjunctivitis]) • N. gonorrhoeae and C. trachomatis can also cause conjunctivitis in adults. These infections may result from autoinoculation from a genital infection or from sexual activity. Bacterial conjunctivitis • Serratia marcescens, Pseudomonas aeruginosa, and Moraxella species cause a purulent conjunctivitis that is more frequently seen in chronic care facilities (e.g., nursing homes). Bacterial conjunctivitis Neonatal conjunctivas: is any conjunctivitis with discharge occurring during the first 28 days of life and it Caused by N. gonorrhea (Opthalmia neonatrum) Chlamydia trachomatis and S.agalactiae. Usually transmitted vertically from a genital tract infection in the mother. • Infection carries a high risk of blindness. Eye infection Inclusion conjunctivitis or Chlamydial conjunctivitis: • Caused by Chlamydia trachomatis, the organisms appear as very small bodies (inclusion bodies). • In infants who acquire it in the birth canal, the condition tends to resolve spontaneously in a few weeks or months, but in rare cases it can lead to scarring of the cornea. • Chlamydial conjunctivitis also appears to spread in the unchlorinated waters of swimming pools (pool conjunctivitis). Angular conjunctivitis: • Caused by Moraxella. Lacunata (infection in the angle of eye). • The Bacterial conjunctivitis associated with thick purulent discharge (containing pus cells). Eye infection B. Viral conjunctivitis: • Caused by Adenoviruses and Herps simplex viruses (HSV), it is characterized by hyperemia and watery discharge. It is less serious than Bacterial one, most of them are self-Limited but very infectious especially Adenoviruses. Diagnosis • Diagnosis of conjunctivitis is usually determined based on the clinical signs and symptoms. • Examination of the exudates by Gram stain and culture and scrapings of the follicles are performed if patients do not improve within 48–72 hours despite treatment. Prevention and Treatment • Good hygiene is the only way to prevent conjunctivitis in adults and children other than neonates. • Newborn children are administered antimicrobials in their eyes after delivery to prevent neonatal conjunctivitis from either N. gonorrhoeae or C. trachomatis. • Treatment of those infections, if they are suspected, is started before lab results are available and usually is accomplished with erythromycin, both topical and oral. Prevention and Treatment • If N. gonorrhoeae is confirmed, oral therapy is usually switched to ceftriaxone. • If antibacterial therapy is prescribed for other conjunctivitis cases, it should cover all possible bacterial pathogens. Ciprofloxacin eye drops are a common choice. Erythromycin or gentamicin are also often used. • Because conjunctivitis is usually diagnosed based on clinical signs, a physician may prescribe prophylactic antibiotics even if a viral cause is suspected. Trachoma • Ocular trachoma is a chronic Chlamydia trachomatis infection of the epithelial cells of the eye. • Transmission is favoured by contaminated fingers, fomites, fleas, and a hot, dry climate. • Repeated infections cause inflammation leading to trichiasis, an inturning of the eyelashes. • It is also believed that other bacterial pathogens, such as Streptococcus and Staphylococcus, contribute to the scarring process once trachoma has begun. Trachoma • The first signs of infection are a mild conjunctival discharge and slight inflammation of the conjunctiva. These symptoms are followed by marked infiltration of lymphocytes and macrophages into the infected area. As these cells build up, they impart a pebbled (rough) appearance to the inner aspect of the upper eyelid. In time, a pseudomembrane of exudates and inflammatory leukocytes forms over the cornea, a condition called pannus, which lasts a few weeks. Trachoma • Chronic and secondary infections can lead to corneal damage and impaired vision. • Early treatment of this disease with azithromycin is highly effective and prevents all of the complications. Keratitis • Keratitis is a more serious eye infection than conjunctivitis. • Invasion of deeper eye tissues occurs and can lead to complete corneal destruction. • Any microorganism can cause this condition, especially after trauma to the eye. In developed countries, herpes simplex virus is the most common cause. In developing countries, bacterial and fungal causes are more common. Keratitis • Preliminary symptoms are a gritty feeling in the eye, conjunctivitis, sharp pain, and sensitivity to light. Recurrent and chronic keratitis can lead to Blindness. • The viral condition is treated with topical trifluridine, sometimes supplemented with oral acyclovir. • Keratitis resulting from trauma and subsequent bacterial infection is treated with appropriate antibiotics. • Most physicians will prescribe antibiotics for prophylactic reasons when there is damage to the eye, even if the original cause is viral. Keratitis • In the last few years, another form of keratitis has been increasing in incidence. • An amoeba called Acanthamoeba has been causing serious keratitis cases, especially in people who wear contact lenses. • This free-living amoeba is everywhere—it lives in tap water, freshwater lakes, and the like. • The infections are usually associated with less-than-rigorous contact lens hygiene or previous trauma to the eye. Keratitis • In its early stages, the infection consists of only a mild inflammation, but later stages are often accompanied by severe pain. • Diagnosis is confirmed by the presence of trophozoites and cysts in stained scrapings of the cornea. • treatment with propamidine isethionate eye drops and topical neomycin has been successful • Damage is often so severe as to require a corneal transplant or even removal of the eye. Kerato conjunctivitis and Endophthalmitis Kerato conjunctivitis: • Infection of both cornea and conjunctivas it is complication of conjunctivitis and caused by organisms that cause Keratitis and conjunctivitis, but the most serious one are chlamydia, pseudemonas, S. pneumoniae and S. aureus. Endophthalmitis: • Infection interior eye parts. Due to trauma or surgical or accident. The causative a gents streptococci and staphylococci it is rare infection but lead to blindness. River Blindness • River blindness is a chronic parasitic (helminthic) infection. • It is endemic in dozens of countries in Latin America, Africa, Asia, and the Middle East. • At any given time, approximately 37 million people are infected with the worm called Onchocerca volvulus. This organism is a filarial (threadlike) helminthic worm transmitted by small, biting vectors called black flies. • River blindness has been a serious problem in many areas of Africa. In some villages, nearly half of the residents are affected by the disease. River Blindness • The Onchocerca larvae are deposited into a bite wound and develop into adults in the immediate subcutaneous tissues, where disfiguring nodules form within 1 to 2 years after initial contact. • Microfilariae (immature worm forms) given off by the adult female migrate via the bloodstream to many locations but especially to the eyes. • The worms eventually invade the entire eye, producing much inflammation and permanent damage to the retina and optic nerve. Bacterial conjunctivitis Opthalmia neonatrum Uncommon complication of Conjuctivitis Thank you
