What is Conjunctivitis?

Mechanical causes / irritants (e.g. eyelashes, contact lenses, foreign bodies, self-inflicted irritation and floppy eyelid syndrome)
Neoplasia—continuous, unregulated increase in cells growth in a tissue.
Chemicals / toxins (e.g. medicaments and personal care products.)

Clinical evaluation of conjunctivitis:

The four main clinical features which should be considered in the diagnosis of  conjunctivitis are:
Type of discharge
Type of conjunctival reaction
Presence of pseudomembranes or true membranes
Presence or absence of lymphadenopathy (enlarged
lymphnodes).

Discharge:

The discharge is composed of the exudate that has filtered through the conjunctival epithelium from dilated blood vessels. The following are the main types of discharge:
Watery—composed of a serous exudate and a variable amount of refluxly secreted tears. It is typical of viral and toxic inflammations.
Mucoid—typical of vernal (seasonal) conjunctivitis  and keratoconjunctivitis sicca.
Purulent—occurs in severe acute bacterial infections.
Mucopurulent—occurs in mild bacterial as well as chlamydial infections.

Pseudomembranes and membranes:
Pseudomembranes consist of coagulated exudate adherent to the inflamed conjunctival epithelium. The 4 main reasons are :
Severe adenoviral infection
Ligneous conjunctivitis
Gonococcal conjunctivitis
Autoimmune conjunctivitis.
True membranes form when the inflammatory exudate permeates the superficial layers of the conjunctival epithelium. The main causes are:
Beta hemolytic streptococci
Diptheria

Lymphadenopathy (enlarged lymphnodes):
This is a feature of:
Viral infections
Chlamydial infections
Severe gonococcal conjunctivitis

Bacterial conjunctivitis:

Simple bacterial conjunctivitis is a very common and usually self-limiting condition. Presentation is with an acute onset of redness, grittiness, burning and discharge. On waking the eyelids are frequently stuck together and difficult to open as a result of the accumulation of exudate during the night. Both eyes are usually involved, although one may become affected before the other by a day or so.

Adult gonococcal keratoconjunctivitis:
Presents as a hyperacute, extremely profuse and thick creamy pus leaking from the eye.

Viral conjunctivitis:

Adenoviral keratoconjunctivitis:
There are two types (PCF and EKC) both of which occur as epidemics and are highly contagious for up to two weeks. The virus can spread from finger-to-eye contact so hand washing is extremely important. It presents with acute watering, redness, discomfort and photophobia. Both eyes are affected in about 60% of cases.

Chlamydial conjunctivitis:

This typically affects young adults during sexually active years. The eye lesions present about 1 week after sexual exposure. It usually presents as a unilateral chronic muco-purulent discharge. If untreated the disease has a prolonged remittent course.

Neonatal conjunctivitis:

This is defined as a conjunctival inflammation that occurs during the first month of life. The three main causes are:
Chlamydial—most common cause. Typically between 5 and 14 days with an acute mucopurulent discharge.
Gonococcal—rare cause. Usually between 1 –3 days after birth with a hyperacute purulent conjunctivitis.
3) Miscellaneous—may be caused by silver nitrate or  antibiotics used as prophylaxis  against gonococcal infection. It presents within a few hours of delivery or instilling the agent..

Allergic conjunctivitis:
Seasonal allergic (hay fever) conjunctivitis is a very common allergic reatcion triggered by airborne antigens such as mould spores, pollen, grass, weeds, hair, wool and feathers. It presents with acute, transient attacks of itching, lacrimation and redness during the hay fever season.
The main symptoms are ocular itching which may be associated with lacrimation, photophobia, foreign body sensation and burning. Thick mucous discharge from the eyes and ptosis (droopy lids) also occur. The symptoms are characteristically worse during spring and summer.

Atopic keratoconjunctivitis:
This is relatively rare but potentially serious and typically affects young men with atopic dermatitis. In addition to the skin changes patients may also have asthma, hay fever, urticaria, migraines and rhinitis.

Autoimmune conjunctivitis
Cicatricial pemphigoid—blisters of the skin and mucous membranes. Primarily a disease of the elderly. Presents as irritation, burning and tearing.
Steven-Johnson Syndrome—presents as fever, malaise, sore throat and possible a cough and arthralgia which could last up to 14 days.