If visual loss, significant pain, sensitivity to light, signs of herpes, or if symptoms do not improve after a week, further diagnosis and treatment may be required. Conjunctivitis in a newborn, known as neonatal conjunctivitis, may also require specific treatment. Signs and symptoms
Red eye, swelling of the conjunctiva, and watering of the eyes are symptoms common to all forms of conjunctivitis. However, the pupils should be normally reactive, and the visual acuity normal. Conjunctivitis is identified by inflammation of the conjunctiva, manifested by irritation and redness. Examination using a slit lamp (biomicroscope) may improve diagnostic accuracy. Examination of the palpebral conjunctiva, that overlying the inner aspects of the eyelids, is usually more diagnostic than examination of the bulbal conjunctiva, that overlying the sclera. Viral
Between 65% and 90% of cases of viral conjunctivitis are caused by adenoviruses. Viral conjunctivitis is often associated with an infection of the upper respiratory tract, a common cold, or a sore throat. Its symptoms include excessive watering and itching. The infection usually begins in one eye but may spread easily to the other eye. Viral conjunctivitis manifests as a fine, diffuse pinkness of the conjunctiva which may be mistaken for iritis, but corroborative signs on microscopy, particularly numerous lymphoid follicles on the tarsal conjunctiva, and sometimes a punctate keratitis are seen. Allergic
Allergic conjunctivitis is inflammation of the conjunctiva due to allergy. The specific allergens may differ among patients.
Signs of such conditions include decreased vision, significantly increased sensitivity to light, inability to keep the eye open, a pupil that does not respond to light, or a severe headache with nausea. Fluctuating blurring is common, due to tearing and mucoid discharge. Mild photophobia is common. However, if any of these symptoms is prominent, considering other diseases such as glaucoma, uveitis, keratitis, and even meningitis or carotico-cavernous fistula is important.A more comprehensive differential diagnosis for the red or painful eye includes:
Corneal abrasion
Subconjunctival hemorrhage
Pinguecula
Blepharitis
Dacryocystitis
Keratoconjunctivitis sicca (dry eye)
Keratitis
Herpes simplex
Herpes zoster
Episcleritis - an inflammatory condition that produces a similar appearance to conjunctivitis, but without discharge or tearing
Uveitis
Acute angle-closure glaucoma
Endophthalmitis
Orbital cellulitis

Prevention
The most effective prevention is good hygiene, especially avoiding rubbing the eyes with infected hands. Vaccination against adenovirus, Haemophilus influenzae, pneumococcus, and Neisseria meningitidis is also effective.Povidone-iodine eye solution has been found to prevent neonatal conjunctivitis. It is becoming more commonly used globally because of its low cost. Management
Conjunctivitis resolves in 65% of cases without treatment, within 2–5 days. The prescription of antibiotics is not necessary in most cases. Viral
Viral conjunctivitis usually resolves on its own and does not require any specific treatment. Antihistamines (e.g., diphenhydramine) or mast cell stabilizers (e.g., cromolyn) may be used to help with the symptoms. Povidone-iodine has been suggested as a treatment, but as of 2008, evidence to support it was poor. Allergic
For allergic conjunctivitis, cool water poured over the face with the head inclined downward constricts capillaries, and artificial tears sometimes relieve discomfort in mild cases.