Eye infection - Introduction, Etiological agents, Clinical syndromes

Introduction to an eye infection

In the conjunctival sacs, sparse indigenous (resident microbes) flora are present. Some of these microorganisms responsible for eye infections are listed:

• Staphylococcus epidermidis (most frequently found)

• Lactobacillus spp. (most frequently found)

• Propinoibacterium acnes

• Staphylococcus aureus – is found in less than 30% of individuals

• Haemophilus influenzae – colonies 0.4 – 25%

• Moraxella catarrhalis (found in a very small percentage)

• Streptococcus pyogenes (found in a very small percentage)

• S. pneumoniae (found in a very small percentage)

• Enterobacteriaceae (found in a very small percentage)

Etiological agents of eye infection

The potential pathogens for eye infections are

• Staphylococcus aureus

• Pseudomonas aeruginosa

• Haemophilus influenzae

• Streptococcus pneumoniae

• Cornebacterium diptheriae

• Neisseria gonorrhoeae

• Escherichia coli

• Chlamydia trachomatis

• Moraxella lacunata

Predisposing factors of eye infection

Eye infections depend on the following factors:

• Age

• Trauma

• Use of contact lens

• Immunocompromised state

Clinical syndromes/manifestation

The clinical syndromes/manifestations of eye infection include:

1. Blepharitis

2. Conjunctivitis

3. Keratitis

4. Trachoma

5. Keratoconjunctivitis

6. Chorioretinitis and uveitis

7. Endophthalmitis

8. Canalculitis, Lacrimal infection

9. Dacryocystitis

10. Dacryoadenitis

Blepharitis

Blepharitis is the inflammation of the margins of the eyelids, eyelashes, or associated pilosebaceous glands. The symptoms of this eye infection include irritation, redness, burning sensation, and itching. The first (common) causative agent is S. aureus.

Conjunctivitis

The inflammation of the conjunctiva, a thin mucous membrane that lines the inside of the eyelids and covers the sclera of the eye, is called conjunctivitis. Symptoms, which can be acute or chronic, include swelling of the conjunctiva, inflammatory exudates, burning, and itching.

Acute conjunctivitis is the sudden onset of infection while chronic conjunctivitis is the condition of conjunctivitis lasting more than 4 weeks. Hyperacute conjunctivitis is defined as an infection that occurs during birth. Eg: Neisseria gonorrhoeae can occur through CIA vertical transmission (mother to fetus).

Conjunctivitis, a type of eye infection, may be purulent [pus+tensed eyelid+ difficulty in cleaning eye] or mucopurulent [mucous + pus +exudates +matting]. It is of two types:

• membranous conjunctivitis

• Angular conjunctivitis

Membranous conjunctivitis (aka diphtheritic conjunctivitis)

In membranous conjunctivitis (aka diphtheritic conjunctivitis), the pseudomembrane is formed on the conjunctival layer caused by Corynebacterium diphtheriae and is characterized by necrosis of epithelial cells.

Angular conjunctivitis

Angular conjunctivitis occurs at the margin of the conjunctival layer and is caused by Moraxella lacunata. It is characterized by discharge at nighttime and may be purulent or mucopurulent.

Keratitis

Keratitis is the inflammation of the cornea of the eye and is caused by Staphylococcus aureus, Pseudomonas aeruginosa, Moraxella lacunata. Symptoms of this eye infection include intense pain, a decrease in some vision, with or without discharge from the eye, blurred vision, gritty sensation, and red eye. It occurs especially in people using contact lenses.

Trachoma

Trachoma, an eye infection, is inflammation of the cornea caused by Chlamydia trachomatis:

• 1^st stage: small white bumps/follicles occur inside the eyelid. It damages the eyelids as the bacteria is intracellular

• 2^nd stage: eyelashes slowly enters the eyes and rub the cornea

• 3^rd stage: damage to the cornea occurs followed by clouds as a result of rubbing (finally, blindness occurs)

Keratoconjunctivitis

Eye infections such as Keratoconjunctivitis is the infection of both the cornea and conjunctiva.

Chorioretinitis and uveitis

Chorioretinitis and uveitis, a type of eye infection, are the inflammation of the retina and underlying choroid or the uvea. The condition may result in loss of vision. It is caused by Mycobacterium tuberculosis, Treponema pallidum, and Borrelia burgdorferi.

Endophthalmitis

Endophthalmitis is the infection of the aqueous or vitreous humor of the eye. The disease develops suddenly and progresses rapidly often leading to blindness. Pain is experienced especially while moving the eye, and decreased vision. It is caused by Staphylococcus aureus, Pseudomonas aeroginosa, Streptococcus penumoniae, and Streptococcus epidermidis.

Lacrimal infection, canaliculitis

Lacrimal infection, canaliculitis is a rare condition of eye infection and the chronic inflammation of lacrimal canals in which the eyelids swell with thick mucopurulent discharge. It is caused by: Propionibacterium propionicum, Actinomyces.

Dacryocystitis

Dacryocystitis is the inflammation of the lacrimal sac of the eye. The condition shows symptoms such as pain, swelling, and tenderness of soft tissue in the media canthal region.

Dacryoadenitis

Dacryoadenitis is an acute eye infection of the lacrimal gland. Symptoms include pain, redness, swelling of the upper eyelid, conjunctiva discharge, etc.