Eye infections

Question 1

Describe the general clinical features of conjunctivitis and causes

Answer 1

Conjunctiva partially susceptible

• Conjunctiva covered by eye lids
• Creates warm, most enclosed environment

Conjunctivitis = often referred as pink eye or red eye due to inflammation causing capillaries of conjunctiva becoming more prominent

• Caused by a number of agents: bacteria, viruses, allergic reactions, foreign bodies, contacts and their cleaning solutions

Common symptoms:

• Redness, itching, gritty and uncomfortable feeling
• Excessive tearing and swelling
• Copious discharge, accumulation overnight, making eyes difficult to open in morning
• Bacteria cause a thick, yellow-green discharge

Question 2

For Inclusion conjunctivitis, describe: causative microbe, transmission, symptoms and treatment for both newborn and adult infections

Answer 2

Causative agent: Chlaymydia trachomatis

In newborns

Transmission – caused by passage through infected birth canal

Symptoms: both eyes inflamed and may have mucous discharge

In adults

Transmission - through sexual contact with infected person

• conjunctiva exposed to infected fingers with genital secretions, also eye-to-eye transmission
• poorly maintained chlorinated swimming pool/spa

Symptoms: may have bumps on inside of eyelid (called follicle), eye(s) –> may have stringy mucous discharge

Treatment for both: tetracyline ointment and oral tetracycline

Question 3

For Trachoma, describe: causative microbe, transmission and epidemiology, pathogenesis, treatment and prevention

Answer 3

Causative agent: Chlamydia trachomatis

• Bacteria can attach directly to the conjunctiva, and resist action of eye lids
• Repeated infection causes damage to the cornea by in-turned eyelids and can lead to blindness – Blinding endemic trachoma

Epidemiology

• Endemic in resource poor countries
• poor hygiene –> especially lack of water to wash hands and face, crowded living

Transmission: – direct contact with contaminated individual or material: hands, towels, clothes and flies​

Pathogenesis

• Repeated infections result in inflammation of the eyelid, called entropion​
• In-turned eyelid causes eyelashes to rub and scar cornea
• Over time this results is opacity and blindness, often not significant until adulthood

Prevention and treatment

Lab diagnosis to confirm chlamydial infection

Treatment

• Treat infection with topical tetracycline, preferably azithromycin because only requires one oral dose
• Serious cases may require surgical correction of eyelid

Prevention

Because repeated infection in endemic regions is facilitated by:

• overcrowding, shortage of water, poor hygiene and abundant fly population
• Prevent by improving standard of hygiene

Question 4

List other bacterial and systemic viral pathogens that cause conjunctivitis

Answer 4

BACTERIAL

• Haemophilus influenzae - caused by non-typeable strains (i.e. non-encapsulated)
• Staphylococcus aureus – causes infections in newborns and adults
• Streptococcus pneumoniae
• Neisseria gonorrhoeae – causes infections in newborn from infected birth canal, requiring urgent treatment

VIRAL

• Herpes simplex virus
• Varicella-zoster virus
• Adenovirus
• Measles virus
• Enterovirus

Question 5

List pathogens that cause deep layer infections, the disease they cause and route of infection

Answer 5

Rubella virus -> Cataracts -> infection in utero

CMV –> inflammation of eye -> infection in utero

P.aeruginosa -> serious inner eye infection –> eye operations, bacteria can contaminate eye drops