A study conducted in November of 2017, conveyed a correlation between blepharitis and early onset metabolic syndrome (MetS). To investigate the relationship between blepharitis and MetS, researchers used the Longitudinal Health Insurance Database in Taiwan. Results indicated that hyperlipidaemia and coronary artery disease were significantly correlated with the prior development of blepharitis. Therefore, blepharitis was shown to be significantly related to MetS and can serve as an early indication of the condition.

In another recent study, the presence of Demodex has been unveiled as a common cause of blepharitis. However, the pathogenesis of demodicosis is still unclear. In this study, researchers provide a diagnosis of the disease and propose diagnostic criteria of Demodex blepharitis.

Styes are most commonly caused by the blocking of an oil gland at the base of the eyelash. Styes are experienced by people of all ages. Styes can be triggered by poor nutrition, sleep deprivation, lack of hygiene, lack of water, and rubbing of the eyes. Styes often result from a Staphylococcal infection in the eye, and can be secondary to blepharitis or a deficiency in immunoglobulin. Sharing of washcloths or face towels should be curtailed to avoid spreading the infection between individuals. Styes can last from one to two weeks without treatment, or as little as four days if treated properly.

Keratoconjunctivitis sicca is relatively common within the United States, especially so in older patients. Specifically, the persons most likely to be affected by dry eyes are those aged 40 or older. 10-20% of adults experience Keratoconjunctivitis sicca. Approximately 1 to 4 million adults (age 65-84) in the USA are effected.

While persons with autoimmune diseases have a high likelihood of having dry eyes, most persons with dry eyes do not have an autoimmune disease. Instances of Sjögren syndrome and keratoconjunctivitis sicca associated with it are present much more commonly in women, with a ratio of 9:1. In addition, milder forms of keratoconjunctivitis sicca also are more common in women. This is partly because hormonal changes, such as those that occur in pregnancy, menstruation, and menopause, can decrease tear production.

In areas of the world where malnutrition is common, vitamin A deficiency is a common cause. This is rare in the United States.

Racial predilections do not exist for this disease.

The mechanism by which the bacteria causes symptoms of blepharitis is not fully understood and may include direct irritation of bacterial toxins and/or enhanced cell-mediated immunity to S. aureus.

Staphylococcal blepharitis is caused by an infection of the anterior portion of the eyelid by Staphylococcal bacteria. In a study of ocular flora, 46% to 51% of those diagnosed with staphylococcal blepharitis had cultures positive for Staphylococcus aureus in comparison to 8% of normal patients. Staphylococcal blepharitis may start in childhood and continue into adulthood. It is commonly recurrent and it requires special medical care. The prevalence of Staphylococcus aureus in the conjunctival sac and on the lid margin varies among countries, likely due to differences in climate and environment. Seborrheic blepharitis is characterized by less inflammation than Staphylococcal blepharitis; however, it causes more excess oil or greasy scaling. Meibomian Gland Dysfunction is a result of abnormalities of the meibomian glands and altered secretion meibum, which plays an imperative role in lagging the evaporation of tear films and smoothing of the tear film to produce an even optical surface. Posterior blepharitis is an inflammation of the eyelids, secondary to dysfunction of the meibomian glands. Like anterior blepharitis, it is a bilateral chronic condition and may be associated with skin rosacea. There is growing evidence that, in some cases, it is caused by Demodex mites.

Of the many causes, conjunctivitis is the most common. Others include:

"Usually nonurgent"

- blepharitis - a usually chronic inflammation of the eyelids with scaling, sometimes resolving spontaneously

- subconjunctival hemorrhage - a sometimes dramatic, but usually harmless, bleeding underneath the conjunctiva most often from spontaneous rupture of the small, fragile blood vessels, commonly from a cough or sneeze

- inflamed pterygium - a benign, triangular, horizontal growth of the conjunctiva, arising from the inner side, at the level of contact of the upper and lower eyelids, associated with exposure to sunlight, low humidity and dust. It may be more common in occupations such as farming and welding.

- inflamed pinguecula - a yellow-white deposit close to the junction between the cornea and sclera, on the conjunctiva. It is most prevalent in tropical climates with much UV exposure. Although harmless, it can occasionally become inflamed.

- dry eye syndrome - caused by either decreased tear production or increased tear film evaporation which may lead to irritation and redness

- airborne contaminants or irritants

- tiredness

- drug use including cannabis

"Usually urgent"

- acute angle closure glaucoma - implies injury to the optic nerve with the potential for irreversible vision loss which may be permanent unless treated quickly, as a result of increased pressure within the eyeball. Not all forms of glaucoma are acute, and not all are associated with increased 'intra-ocular' pressure.

- injury

- keratitis - a potentially serious inflammation or injury to the cornea (window), often associated with significant pain, light intolerance, and deterioration in vision. Numerous causes include virus infection. Injury from contact lenses can lead to keratitis.

- iritis - together with the ciliary body and choroid, the iris makes up the uvea, part of the middle, pigmented, structures of the eye. Inflammation of this layer (uveitis) requires urgent control and is estimated to be responsible for 10% of blindness in the United States.

- scleritis - a serious inflammatory condition, often painful, that can result in permanent vision loss, and without an identifiable cause in half of those presenting with it. About 30-40% have an underlying systemic autoimmune condition.

- episcleritis - most often a mild, inflammatory disorder of the 'white' of the eye unassociated with eye complications in contrast to scleritis, and responding to topical medications such as anti-inflammatory drops.

- tick borne illnesses like Rocky Mountain spotted fever - the eye is not primarily involved, but the presence of conjunctivitis, along with fever and rash, may help with the diagnosis in appropriate circumstances.

It is usually caused by allergies or viral infections, often inciting excessive eye rubbing. Chemosis is also included in the Chandler Classification system of orbital infections.

If chemosis has occurred due to excessive rubbing of the eye, the first aid to be given is a cold water wash for eyes.

Other causes of chemosis include:

- Superior vena cava obstruction, accompanied by facial oedema

- Hyperthyroidism, associated with exophthalmos, periorbital puffiness, lid retraction, and lid lag

- Cavernous sinus thrombosis, associated with infection of the paranasal sinuses, proptosis, periorbital oedema, retinal haemorrhages, papilledema, extraocular movement abnormalities, and trigeminal nerve sensory loss

- Carotid-cavernous fistula - classic triad of chemosis, pulsatile proptosis, and ocular bruit

- Cluster headache

- Trichinellosis

- Systemic lupus erythematosus (SLE)

- Angioedema

- Acute glaucoma

- Panophthalmitis

- Orbital cellulitis

- Gonorrheal conjunctivitis

- Dacryocystitis

- Spitting cobra venom to the eye

- High concentrations of phenacyl chloride in chemical mace spray

- Urticaria

- Trauma

- Post surgical

- Rhabdomyosarcoma of the orbit

Keratoconjunctivitis sicca is uncommon in cats. Most cases seem to be caused by chronic conjunctivitis, especially secondary to feline herpesvirus. Diagnosis, symptoms, and treatment are similar to those for dogs.

Stye prevention is closely related to proper hygiene. Proper hand washing can reduce the risks of developing not only styes, but also many other types of infections.

Upon awakening, application of a warm washcloth to the eyelids for one to two minutes may be beneficial in decreasing the occurrence of styes by liquefying the contents of the oil glands of the eyelid and thereby preventing blockage.

To prevent developing styes, it is recommended to never share cosmetics or cosmetic eye tools with other people. People should also keep their eye tools clean and generally practice proper eye hygiene. It is also recommended to remove makeup every night before going to sleep and discard old or contaminated eye makeup.

Most conjunctivochalasis is thought to be caused by both a gradual thinning and stretching of the conjunctiva that accompanies age and a loss of adhesion between the conjunctiva and underlying sclera due to the dissolution of Tenon's capsule. The resulting loose, excess conjunctiva may mechanically irritate the eye and disrupt the tear film and its outflow, leading to dry eye and excess tearing. A correlation may also exist between inflammation in the eye and conjunctivochalasis; though it is unclear if this correlation is causal. Conjunctivochalasis may be associated with previous surgery, Blepharitis, Meibomian Gland Disorder (MGD), Ehlers-Danlos Syndrome, and Aqueous Tear Deficiency,

A red eye is an eye that appears red due to illness or injury. It is usually injection and prominence of the superficial blood vessels of the conjunctiva, or sclera, which may be caused by disorders of these or adjacent structures. Conjunctivitis and subconjunctival hemorrhage are two of the less serious but more common causes.

Management includes assessing whether emergency action (including referral) is needed, or whether treatment can be accomplished without additional resources.

Slit lamp examination is invaluable in diagnosis but initial assessment can be performed using a careful history, testing vision (visual acuity), and carrying out a penlight examination.

Because the disorder often occurs in people with typical dry eye symptoms, it can be difficult to distinguish readily the discomfort caused by the dry eye from that directly related to the redundant conjunctiva.

Trichiasis in dogs is hair from the eyelid growing in the wrong direction and rubbing on the eye, causing irritation. It usually occurs at the lateral upper eyelid, especially in the English Cocker Spaniel. Trichiasis also refers to hair from a nasal fold rubbing on the eye. This type of trichiasis can be flattened by rubbing petroleum jelly onto it, but surgery is sometimes necessary for permanent correction.

Conjunctivitis due to chemicals is treated via irrigation with Ringer's lactate or saline solution. Chemical injuries (particularly alkali burns) are medical emergencies, as they can lead to severe scarring and intraocular damage. People with chemically induced conjunctivitis should not touch their eyes, regardless of whether or not their hands are clean, as they run the risk of spreading the condition to another eye.

Conjunctivitis may also be caused by allergens such as pollen, perfumes, cosmetics, smoke, dust mites, Balsam of Peru, and eye drops.

Trichiasis (, or , ) a medical term for abnormally positioned eyelashes that grow back toward the eye, touching the cornea or conjunctiva. This can be caused by infection, inflammation, autoimmune conditions, congenital defects, eyelid agenesis and trauma such as burns or eyelid injury. It is the leading cause of infectious blindness in the world.

Standard treatment involves removal or destruction of the affected eyelashes with electrology, specialized laser, or surgery. In many cases, removal of the affected eyelashes with forceps resolves the symptoms, although the problem often recurs in a few weeks when the eyelashes regrow. Severe cases may cause scarring of the cornea and lead to vision loss if untreated. Mild cases may not require treatment.

Repeated cases of trachoma infection may cause trichiasis.

Posterior misdirection of normal lashes most frequently affects lower lid.

Chemosis is the swelling (or edema) of the conjunctiva. It is due to the oozing of exudate from abnormally permeable capillaries. In general, chemosis is a nonspecific sign of eye irritation. The outer surface covering appears to have fluid in it. The conjunctiva becomes swollen and gelatinous in appearance. Often, the eye area swells so much that the eyes become difficult or impossible to close fully. Sometimes, it may also appear as if the eyeball has moved slightly backwards from the white part of the eye due to the fluid filled in the conjunctiva all over the eyes except the iris. The iris is not covered by this fluid and so it appears to be moved slightly inwards.

Episcleritis is a common disease, and its exact prevalence and incidence are unknown. It typically affects young adults, and may be more common in women.

Ocular rosacea is a manifestation of rosacea that affects the eyes and eyelids. Signs and symptoms generally consist of redness, irritation or burning of the eyes. Affected individuals may also feel that there is something, such as an eyelash, in the eye and frequently have redness of the nose and cheeks as well.

Those who suffer from ocular rosacea may be treated with warm compresses, artificial tears and washing the area around the eye with warm water, including the eyelids, to help relieve symptoms. Additionally, oral antibiotics, typically doxycycline, may be prescribed. Some people with ocular rosacea feel that dietary restrictions of caffeine, spicy foods, and alcoholic beverages may reduce or eliminate symptoms.

Episcleritis is a benign, self-limiting condition, meaning patients recover without any treatment. Most cases of episcleritis resolve within 7–10 days. The nodular type is more aggressive and takes longer to resolve. Although rare, some cases may progress to scleritis. However, in general, episcleritis does not cause complications in the eye. Smoking tobacco delays the response to treatment in patients with episcleritis.

Perhaps the most universal risk of sneezing is the spread of disease. Bacterial infections can spread to susceptible uninfected people via the spread of microscopic organisms suspended in the droplets expelled by a sneeze. Bacteria which commonly spread by sneezing include bacterial meningitis, strep throat, and tuberculosis. Viral infections can also be spread by sneezing. When a virus is expelled by a sneeze, its mucous membrane evaporates, and the virus becomes a droplet nucleus which can be inhaled by another person, thus spreading the virulent infection. Examples of virulent infections that spread by sneezing include measles, mumps, rubella, and influenza.

Causes of epiphora are any that cause either overproduction of tears or decreased drainage of tears, resulting in tearing onto the cheek. This can be due to ocular irritation and inflammation (including trichiasis and entropion) or an obstructed tear outflow tract which is divided according to its anatomical location (i.e. ectropion, punctal, canalicular or nasolacrimal duct obstruction). The latter is often due to aging (a spontaneous process), conjunctivochalasis, infection (i.e. dacryocystitis), rhinitis, and in neonates or infants, failure of the nasolacrimal duct to open. Another cause could be poor reconstruction of the nasolacrimal duct system after trauma to the area. Cause of trauma could be facial fractures (including nasoethmoid fractures or maxillary Le Fort fractures), and soft tissue trauma involving the nose and/or the eyelid.

This condition is often frustrating or irritating. A systematic review studying the usage of punctal plugs for treatment of dry eye reported a few cases of epiphora among participants.

A fit of sneezing while operating a vehicle can cause the operator to lose control of that vehicle, resulting in injury to the person, and damage to the vehicle and/or surroundings. In particular, photic sneezing poses a considerable risk to pilots, due to the frequent presence of bright sunlight and the precise reactions needed to successfully control the aircraft. For the pilot of a fighter aircraft, if an uncontrollable fit of sneezing were to occur during aerial combat, the pilot could be incapacitated when his or her situational awareness needs to be greatest. A plane landing on an aircraft carrier or shoreline also requires precise movements and quick reflexes. The reflection of the sun from surrounding water has a high probability of producing at least one photic sneeze for pilots who have the reflex. Any amount of sneezing while attempting to land could cause the pilot to lose control, potentially resulting in disaster.

Conjunctival concretions can be seen easily by everting the eyelid. The projecting concretions should be removed. Removal is easily performed by a doctor. For example, using needles or sharp knife removes the concretion, under a local light anesthesia of the conjunctiva.

Epiphora is an overflow of tears onto the face. A clinical sign or condition that constitutes insufficient tear film drainage from the eyes in that tears will drain down the face rather than through the nasolacrimal system.

Conjunctival concretions can be single, also multiple, less confluent. There is no difference between the site of the occurrence on the upper and lower eyelid, nor right or left eye. The vast majority of concretions are in the conjunctival surface rather than deep. There is no difference in age for predilection or incidence of concretions, due to the causes of conjunctivitis, aging, and even congenital factor.