Conjunctivitis Flashcards
What is the conjunctiva?
The conjunctiva is a transparent mucous membrane that lines both the inner surface of the eyelids and the anterior surface of the eyeball (except the cornea).
Parts of the conjunctiva?
- The part lining the eyelid is called the palpebral conjunctiva, while the membrane lining the anterior eye is called the bulbar conjunctiva.
- The point at which the palpebral conjunctiva changes to bulbar, a deep fold or recess is formed called the conjunctival fornix and this space between the two conjunctiva is called the conjunctival sac.
Structure of the conjunctiva?
- epithelium
- stroma
- adenoid layer
- fibrous layer
What is conjunctivitis?
- Conjunctivitis, or pink eye, is an inflammation of the transparent membrane that lines the eyelid and the eyeball (the conjunctiva).
- It is characterized by dilation of the conjunctival vessels resulting in hyperemia and edema of the conjunctiva
Classificaion of conjunctivitis based on etiology?
- infectious (bacterial, viral)
- non-infectious (allergic, irritant, secondary to systemic cause )
Classification of conjunctivitis based on type of exudate?
- Purulent
- Mucopurulent
- Membranous
- Pseudomembranous
- Catarrhal
Classification of conjunctivitis based on clinical course?
- Acute (resolves <4weeks)
- Chronic (persists >4 weeks)
Epidemiology of conjunctivitis?
- Viral conjunctivitis is the most common form accounting for 15 -70% of cases and is more common in adults.
- Bacterial conjunctivitis is more prevalent in children and is responsible for 50 -75% of cases.
- Allergic conjunctivitis affects between 6% and 30% of the general population with a higher prevalence in children.
- There is no significant gender difference.
- Most prevalent eye condition in Malawi at 51%
Pathophysiology of conjunctivitis?
- microbes enter the eye on contact with infected objects
- inflammation of the eye
- congestion and increased permeability of blood vessels of the eye
- swelling, redness, exudates and discharge
Pathophysiology of allergic conjuntivitis?
- Allergen comes in contact with the conjunctiva, and this causes a type 1 hypersensitivity reaction.
- There is activation of mast cells due to allergen crosslinking of surface IgE receptors.
- Degranulation occurs and there is release of histamines, cytokines and prostaglandins.
- These substances then induce vascular leakage causing cellular infiltration of eosinophils and neutrophils.
Risk factors of bacterial conjunctivitis?
- Contact with contaminated fingers or oculogenital contact
- Compromised tear production/drainage
- Trauma
- Immunosuppressed status
Risk factors for viral conjunctivitis?
Contact with:
1. Contaminated finger
2. Medical instruments
3. Swimming pool water
4. Personal items from an infected person
Risk factors for allergic conjunctivitis?
History of non-ocular allergic conditions eg eczema
Clinical features of conjunctivitis?
- Acute onset of redness
- Grittiness
- Photophobia
- Burning
- Eyelid edema and erythema
- Discharge
> watery - viral
> mucoid - bacterial
> mucopurulent or purulent - bacterial - Itching - allergic
Causes of bacterial conjunctivitis?
Most commonly caused by
1. Staphylococcus epidermidis
2. Staphylococcus aureus
3. Streptococcus pneumoniae
4. Hemophilus influenzae
5. Moraxella lacunata.
Describe gonoccocal conjunctivitis?
- Caused by Neisseria gonorrhea, a gram-negative diplococcus.
- It is sexually transmitted
- Incubation period of 3–5 days in adults and 1–3 days in neonates.
- In neonates it causes ophthalmia neonatorum (happens in first month of life) which is potentially life-threatening and can cause systematic complications
Describe chlamydial conjunctivitis?
- Caused by Chlamydia trachomatis serotypes D-K
- Usually occurs in sexually active adults and adolescents
- Almost always sexually transmitted although occasional eye-to-eye infection is reported
- It also occurs in neonates
Describe trachoma?
- Accounts for 10-15% of global blindness and is the leading preventable cause
- Caused by Chlamydia trachomatis serotypes A, B, Ba and C
- It is a chronic/recurrent conjunctivitis
- Occurs in crowded areas and areas of poor hygiene
- Common fly is the vector
Elimination strategy for trachoma?
SAFE
S - surgery for advanced disease
A - antibiotics to clear infection
F - facial cleanliness
E - environmental improvement to reduce transmission
Causes of viral conjunctivitis?
- adenovirus
- Molluscum contagiosum
- Herpes simplex
Describe adenoviral conjunctivitis?
Adenoviral conjunctivitis is highly contagious, and the spectrum of presentation may be generalized into 2 distinct syndromes:
1. Pharyngoconjunctival fever- aerosol transmission, usually post upper respiratory tract infection
2. Epidemic keratoconjunctivitis- transmission by contact (fingers, instruments), there is an 80% chance of developing keratitis
Describe molluscum contagiosum conjunctivitis?
- Molluscum contagiosum conjunctivitis is common in children/ young adults and profuse lesions are seen with HIV infection.
- These patients present with chronic history of umbilicated nodule at the lid margin.
Describe allergic conjunctivitis?
- This occurs due to exposure of the lid surface to a transient allergen.
- It is a type 1 hypersensitivity reaction
The types of allergic conjunctivitis?
- Seasonal
- Vernal
- Atopic
- Acute
