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 with one eye, but may spread easily to the other.

Viral conjunctivitis shows a fine, diffuse pinkness of the conjunctiva, which is easily mistaken for the ciliary infection of iris (iritis), but there are usually corroborative signs on microscopy, particularly numerous lymphoid follicles on the tarsal conjunctiva, and sometimes a punctate keratitis.

Allergic conjunctivitis is inflammation of the conjunctiva (the membrane covering the white part of the eye) due to allergy. Allergens differ among patients.

Symptoms consist of redness (mainly due to vasodilation of the peripheral small blood vessels), swelling of the conjunctiva, itching, and increased lacrimation (production of tears). If this is combined with rhinitis, the condition is termed "allergic rhinoconjunctivitis". The symptoms are due to release of histamine and other active substances by mast cells, which stimulate dilation of blood vessels, irritate nerve endings, and increase secretion of tears.

Neonatal conjunctivitis by definition presents during the first month of life. It may be infectious or non infectious. In infectious conjunctivitis, the organism is transmitted from the genital tract of an infected mother during birth or by infected hands.

- Pain and tenderness in the eyeball.

- Conjunctival discharge: purulent, mucoid or mucopurulent depending on the cause.

- Conjunctiva shows hyperaemia and chemosis. Eyelids are usually swollen.

- Corneal involvement (rare) may occur in herpes simplex ophthalmia neonatorum.

Ligneous conjunctivitis is a rare form of chronic conjunctivitis characterized by recurrent, fibrin-rich pseudomembranous lesions of wood-like consistency that develop mainly on the underside of the eyelid (tarsal conjunctiva). It is generally a systemic disease which may involve the periodontal tissue, the upper and lower respiratory tract, kidneys, middle ear, and female genitalia. It can be sight-threatening, and death can occasionally occur from pulmonary involvement.

It has been speculated that ligneous conjunctivitis may be a manifestation of IgG4-related disease (IgG4-RD) involving the conjunctiva.

The conjunctiva is a thin membrane that covers the eye. When an allergen irritates the conjunctiva, common symptoms that occur in the eye include: ocular itching, eyelid swelling, tearing, photophobia, watery discharge, and foreign body sensation (with pain).

Itching is the most typical symptom of ocular allergy, and more than 75% of patients report this symptom when seeking treatment. Symptoms are usually worse for patients when the weather is warm and dry, whereas cooler weather with lower temperatures and rain tend to assuage symptoms. Signs in phlyctenular keratoconjunctivitis include small yellow nodules that develop over the cornea, which ulcerate after a few days.

A study by Klein et al. showed that in addition to the physical discomfort allergic conjunctivitis causes, it also alters patients' routines, with patients limiting certain activities such as going outdoors, reading, sleeping, and driving. Therefore, treating patients with allergic conjunctivitis may improve their everyday "quality of life."

Untreated cases may develop corneal ulceration, which may perforate resulting in corneal opacification and Staphyloma formation.

Symptoms of scleritis include:

- Redness of the sclera and conjunctiva, sometimes changing to a purple hue

- Severe ocular pain, which may radiate to the temple or jaw. The pain is often described as deep or boring.

- Photophobia and tearing

- Decrease in visual acuity, possibly leading to blindness

The pain of episcleritis is less severe than in scleritis. In hyperemia, there is a visible increase in the blood flow to the sclera (hyperaemia), which accounts for the redness of the eye. Unlike in conjunctivitis, this redness will not move with gentle pressure to the conjunctiva.

Primary infection most commonly manifests as blepharoconjunctivitis i.e. infection of lids and conjunctiva that heals without scarring. Lid vesicles and conjunctivitis are seen in primary infection. Corneal involvement is rarely seen in primary infection.

This classic herpetic lesion consists of a linear branching corneal ulcer (dendritic ulcer). During eye exam the defect is examined after staining with fluorescein dye. The underlying cornea has minimal inflammation.

Patients with epithelial keratitis complain of foreign-body sensation, light sensitivity, redness and blurred vision.

Focal or diffuse reduction in corneal sensation develops following recurrent epithelial keratitis.

In immune deficient patients or with the use of corticosteroids the ulcer may become large and in these cases it is called geographic ulcer.

The conjunctiva provides lining for the inside of the eyelid as well as a coating for the sclera, the white portion of the eyeball. It typically serves to provide lubrication for the eye through the production of mucus and tears. When infected with AHC, patients will experience painful, red eyes, swelling of the conjunctival tissue, and frequent mucus discharge from the eyes accompanied by excessive tearing and subconjunctival hemorrhaging. This hemorrhaging is caused by the rupture of blood vessels beneath the conjunctiva giving the eyes a bright red appearance. Some patients also experience blurry vision and fever in addition to the common symptoms and one in every ten thousand cases exhibits paralysis similar to that of polio.

Conjunctival concretions are generally asymptomatic. Common symptoms include eye discomfort, eye irritation, and foreign body sensation. Sometimes, the larger, harder or multiple concretions make the rubbing off of the superficial layers of the conjunctiva or eyelids to cause conjunctival abrasion, especially prominent when upon blinking. In severe cases, dysfunction or inflammation of the Meibomian (Meibomianitis, an inflammation of the tarsal glands) glands may occur.

Histopathological findings from affected humans indicate that wound healing is impaired due to a deficiency in plasmin-mediated extracellular fibrinolysis. Episodes may be triggered by minor trauma, eye surgery, or by systemic events such as infections or antifibrinolytic therapy. Histology shows amorphous subepithelial deposits of eosinophilic material consisting predominantly of fibrin.

Patients typically present within one week of surgery with eye pain, photophobia, conjunctivitis, or excessive tear production.

Secondary keratitis or uveitis may occur with scleritis. The most severe complications are associated with necrotizing scleritis.

Chronic conjunctivitis (e.g. trachoma) and aging factor are two causes of conjunctival concretion, which will make the conjunctiva cellular degeneration to produce an epithelial inclusion cyst, filled with epithelial cells and keratin debris. After calcification, the conjunctival cyst hardens and forms a conjunctival concretion. Congenital conjunctival concretion condition is also more common.

Allergic conjunctivitis is inflammation of the conjunctiva (the membrane covering the white part of the eye) due to allergy. Although allergens differ among patients, the most common cause is hay fever. Symptoms consist of redness (mainly due to vasodilation of the peripheral small blood vessels), edema (swelling) of the conjunctiva, itching, and increased lacrimation (production of tears). If this is combined with rhinitis, the condition is termed allergic rhinoconjunctivitis.

The symptoms are due to release of histamine and other active substances by mast cells, which stimulate dilation of blood vessels, irritate nerve endings, and increase secretion of tears.

Treatment of allergic conjunctivitis is by avoiding the allergen ("e.g.", avoiding grass in bloom during "hay fever season") and treatment with antihistamines, either topical (in the form of eye drops), or systemic (in the form of tablets). Antihistamines, medications that stabilize mast cells, and nonsteroidal anti-inflammatory drugs (NSAIDs) are generally safe and usually effective.

Initial signs of FVR include coughing, sneezing, nasal discharge, conjunctivitis, and sometimes fever (up to 106) and loss of appetite. These usually resolve within four to seven days, but secondary bacterial infections can cause the persistence of clinical signs for weeks. Frontal sinusitis and empyema can also result.

FHV-1 also has a predilection for corneal epithelium, resulting in corneal ulcers, often pinpoint or dendritic in shape. Other ocular signs of FHV-1 infection include conjunctivitis, keratitis, keratoconjunctivitis sicca (decreased tear production), and corneal sequestra. Infection of the nasolacrimal duct can result in chronic epiphora (excess tearing). Ulcerative skin disease can also result from FHV-1 infection. FHV-1 can also cause abortion in pregnant queens, usually at the sixth week of gestation, although this may be due to systemic effects of the infection rather than the virus directly.

In chronic nasal and sinus disease of cats, FHV-1 may play more of an initiating role than an ongoing cause. Infection at an early age may permanently damage nasal and sinus tissue, causing a disruption of ciliary clearance of mucus and bacteria, and predispose these cats to chronic bacterial infections.

Conjunctivitis eye condition contracted from exposure to actinic rays. Symptoms are redness and swelling.

Actinic conjunctivitis is an inflammation of the eye contracted from prolonged exposure to actinic (ultraviolet) rays. Symptoms are redness and swelling of the eyes. Most often the condition is caused by prolonged exposure to Klieg lights, therapeutic lamps, or acetylene torches. Other names for the condition include Klieg conjunctivitis, eyeburn, arc-flash, welder's conjunctivitis, flash keratoconjunctivitis, actinic ray ophthalmia, x-ray ophthalmia, and ultraviolet ray ophthalmia.

DLK is predominantly associated with Lasik, as the creation of a flap creates a potential space for cells to accumulate. Individuals with atopic conditions with pre-existing allergic conjunctivitis, or ocular rosacea, are more prone to developing the condition after surgery. Some authors have reported that moderate to severe eye allergies and chronic allergic conjunctivitis are an absolute contraindication to the LASIK procedure. This is in distinction to findings of earlier studies. Keratitis can also occur after photorefractive keratectomy (PRK), although because it occurs in the setting of infection, it is distinct from the sterile infiltrates of DLK. DLK can also occur following myopic keratomileusis, in which a disc of corneal tissue is removed, shaped and sutured back into place, although this technique is more historical, having been replaced by Lasik and PRK.

Feline viral rhinotracheitis (FVR) is an upper respiratory or pulmonary infection of cats caused by "feline herpesvirus 1", of the family "Herpesviridae". It is also commonly referred to as feline influenza, feline coryza, and feline pneumonia but, as these terms describe other very distinct collections of respiratory symptoms, they are misnomers for the condition. Viral respiratory diseases in cats can be serious, especially in catteries and kennels. Causing one-half of the respiratory diseases in cats, FVR is the most important of these diseases and is found worldwide. The other important cause of feline respiratory disease is "feline calicivirus".

FVR is very contagious and can cause severe disease, including death from pneumonia in young kittens. It can cause flat-chested kitten syndrome, but most evidence for this is anecdotal. All members of the "Felidae" family are susceptible to FVR; in fact, FHV-1 has caused a fatal encephalitis in lions in Germany.

Acute hemorrhagic conjunctivitis (AHC) (also spelled acute haemorrhagic conjunctivitis) is a derivative of the highly contagious conjunctivitis virus, otherwise known as pink eye. Symptoms include excessively red, swollen eyes as well as subconjuntival hemorrhaging. Currently, there is no known treatment and patients are required to merely endure the symptoms while the virus runs its five- to seven-day course. While it was first identified in Ghana, the virus has now been seen in China, India, Egypt, Cuba, Singapore, Taiwan, Japan, Pakistan, Thailand, and the United States.

Epulis (literally, 'on the gingiva') is a general term for any gingival or alveolar tumor (i.e. lump on the gum). This term describes only the location of a lump and has no implication on the histologic appearance of a lesion. "Epulis" is also sometimes used synonymously with epulis fissuratum, however other conditions are classified as epulides, e.g. giant cell epulis (peripheral giant cell granuloma), ossifying fibroid epulis (peripheral ossifying fibroma), and congenital epulis.

The lesion is usually painless. The usual appearance is of two excess tissue folds in alveolar vestibule/buccal sulcus, with the flange of the denture fitting in between the two folds. It may occur in either the maxillary or mandibular sulci, although the latter is more usual. Anterior locations are more common than posterior. Less commonly there may be a single fold, and the lesion may appear on the lingual surface of the mandibular alveolar ridge.

The swelling is firm and fibrous, with a smooth, pink surface. The surface may also show ulceration or erythema. The size of the lesion varies from less than 1 cm to involving the entire length of the sulcus.

Ophthalmia (also called ophthalmitis) is inflammation of the eye. It is a medical sign which may be indicative of various conditions, including sympathetic ophthalmia (inflammation of both eyes following trauma to one eye), gonococcal ophthalmia, trachoma or "Egyptian" ophthalmia, ophthalmia neonatorum (a conjunctivitis of the newborn due to either of the two previous pathogens), photophthalmia and actinic conjunctivitis (inflammation resulting from prolonged exposure to ultraviolet rays), and others.