The first sign of a stye is a small, yellowish spot at the center of the bump that develops as pus and expands in the area.

Other stye symptoms may include:

- A lump on the top or bottom eyelid

- Localized swelling of the eyelid

- Localized pain

- Redness

- Tenderness

- Crusting of the eyelid margins

- Burning in the eye

- Droopiness of the eyelid

- Scratchy sensation on the eyeball (itching)

- Blurred vision

- Mucous discharge in the eye

- Irritation of the eye

- Light sensitivity

- Tearing

- Discomfort during blinking

- Sensation of a foreign body in the eye

A stye, also known as a hordeolum, is a bacterial infection of an oil gland in the eyelid. This results in a red tender bump at the edge of the eyelid. The outside or the inside of the eyelid can be affected.

The cause of a stye is usually a bacterial infection by "Staphylococcus aureus". The internal ones are due to infection of the meibomian gland while the external ones are due to an infection of the gland of Zeis. A chalazion on the other hand is a blocked oil gland without infection. They are typically in the middle of the eyelid and non painful.

Often a stye will go away without any specific treatment in a few days or weeks. Recommendations to speed improvement include warm compresses. Occasionally antibiotic eye ointment may be recommended. While these measures are often recommended, evidence to support them is poor. The frequency at which they occur is unclear. They may happen at any age.

Blepharitis is characterized by chronic inflammation of the eyelid, usually at the base of the eyelashes. Symptoms include inflammation, irritation, itchiness, a burning sensation, excessive tearing, and crusting and sticking of eyelids. Additional symptoms may include visual impairment such as photophobia and blurred vision. Symptoms are generally worse in the mornings and patients may experience exacerbation and several remissions if left untreated. It is typically caused by bacterial infection or blockage of the meibomian oil glands. Diseases and conditions that may lead to blepharitis include: rosacea, herpes simplex dermatitis, varicella-zoster dermatitis, molluscum contagiosum, allergic dermatitis, contact dermatitis, seborrheic dermatitis, staphylococcal dermatitis, demodicosis (Demodex), and parasitic infections ("e.g.", Demodex and Phthiriasis palpebrarum).

The parasite, "Demodex folliculorum" ("D. folliculorum"), causes blepharitis when the parasite is present in excessive numbers within the dermis of the eyelids. These parasites can live for approximately 15 days. The parasites (both adult and eggs) live on the hair follicle, inhabiting the sebaceous and apocrine gland of the human lid. Direct contact allows this pathogen to spread. Factors that allow this pathogen to multiply include hypervascular tissue, poor hygienic conditions, and immune deficiency. In treating Blepharitis caused by "D. folliculorum", mechanical cleaning and proper hygiene are important towards decreasing the parasites numbers.

Associated Symptoms:

- Watery eyes - due to excessive tearing.

- Red eyes - due to dilated blood vessels on the sclera.

- Swollen eyelids - due to inflammation.

- Crusting at the eyelid margins/base of the eyelashes/medial canthus, generally worse on waking - due to excessive bacterial buildup along the lid margins.

- Eyelid sticking - due to crusting along the eyelid margin.

- Eyelid itching - due to the irritation from inflammation and epidermis scaling of the eyelid.

- Flaking of skin on eyelids - due to tear film suppressed by clog meibomian glands.

- Gritty/burning sensation in the eye, or foreign-body sensation - due to crusting from bacteria and clogged oil glands

- Frequent blinking - due to impaired tear film from clogged oil glands unable to keep tears from evaporating.

- Light sensitivity/photophobia

- Misdirected eyelashes that grow abnormally - due to permanent damage to the eyelid margin

- Eyelash loss - due to excessive buildup of bacteria along the base of the eyelashes.

- Infection of the eyelash follicle/sebaceous gland (hordeolum)

- Debris in the tear film, seen under magnification (improved contrast with use of fluorescein drops)

Chronic blepharitis may result in damage of varying severity and, in the worst cases, may have a negative effect on vision. This can be resolved with a proper eyeglass prescription. Long-term untreated blepharitis can lead to eyelid scarring, excess tearing, difficulty wearing contact lenses, development of a stye (an infection near the base of the eyelashes, resulting in a painful lump on the edge of the eyelid) or a chalazion (a blockage/bacteria infection in a small oil glands at the margin of the eyelid, just behind the eyelashes, leading to a red, swollen eyelid), chronic pink eye (conjunctivitis), keratitis, and corneal ulcer or irritation. The lids may become red and may have ulcerate, non-healing areas that may lead to bleeding. Blepharitis can also cause blurred vision due to a poor tear film. Tears may be frothy or bubbly, which can contribute to mild scarring along the eyelids. Symptoms and signs of blepharitis are often erroneously ascribed by the patient as "recurrent conjunctivitis".

Staphylococcal blepharitis and Posterior blepharitis or "rosacea-associated" blepharitis Symptoms

Symptoms include a foreign body sensation, matting of the lashes, and burning. Collarette around eyelashes, a ring-like formation around the lash shaft, can be observed. Other symptoms include loss of eyelashes or broken eyelashes. The condition can sometimes lead to a chalazion or a stye. Chronic bacterial blepharitis may also lead to ectropion. Posterior blepharitis or "rosacea-associated" blepharitis is manifested by a broad spectrum of symptoms involving the lids including inflammation and plugging of the meibomian orifices and production of abnormal secretion upon pressure over the glands.

Blepharitis ( ) is one of the most common ocular conditions characterized by inflammation, scaling, reddening, and crusting of the eyelid. This condition may also cause burning, itching, or a grainy sensation when introducing foreign objects or substances to the eye. Although blepharitis is not sight-threatening, it can lead to permanent alterations of the eyelid margin. The overall etiology is a result of bacteria and inflammation from congested meibomian oil glands at the base of each eyelash. Other conditions may give rise to blepharitis, whether they be infectious or noninfectious, including, but not limited to, bacterial infections or allergies.

Different variations of blepharitis can be classified as seborrheic, staphylococcal, mixed, posterior or meibomitis, or parasitic. In a survey of US ophthalmologists and optometrists, 37% to 47% of patients seen by those surveyed had signs of blepharitis, which can affect all ages and ethnic groups. One single-center study of 90 patients with chronic blepharitis found that the average age of patients was 50 years old.

A chalazion or meibomian cyst can sometimes be mistaken for a stye.

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.

Chalazion is a cyst in the eyelid due to a blocked oil gland. They are typically in the middle of the eyelid, red, and non painful. They tend to come on gradually over a few weeks.

A chalazion may occur following a stye or from hardened oils blocking the gland. The blocked gland is usually the meibomian gland but can also be the gland of Zeis. A stye and cellulitis may appear similar. A stye, however, is usually more sudden in onset, painful, and occurs at the edge of the eyelid. Cellulitis is also typically painful.

Treatment is typically initially with warm compresses. If this is not effective injecting steroids into the lesion may be tried. If large, incision and drainage may be recommended. While relatively common the frequency of the condition is unknown. The term is from the Greek "khalazion" meaning "small hailstone".

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.

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.

Periorbital cellulitis must be differentiated from orbital cellulitis, which is an emergency and requires intravenous (IV) antibiotics. In contrast to orbital cellulitis, patients with periorbital cellulitis do not have bulging of the eye (proptosis), limited eye movement (ophthalmoplegia), pain on eye movement, or loss of vision. If any of these features is present, one must assume that the patient has orbital cellulitis and begin treatment with IV antibiotics. CT scan may be done to delineate the extension of the infection.

Affected individuals may experience the following;

swelling,

redness,

discharge,

pain,

shut eye,

conjunctival injection,

fever (mild), slightly blurred vision, teary eyes, and some reduction in vision.

Typical signs include periorbital erythema, induration, tenderness and warmth.

Periorbital cellulitis, also known as preseptal cellulitis (and not to be confused with orbital cellulitis, which is behind the septum), is an inflammation and infection of the eyelid and portions of skin around the eye, anterior to the orbital septum. It may be caused by breaks in the skin around the eye, and subsequent spread to the eyelid; infection of the sinuses around the nose (sinusitis); or from spread of an infection elsewhere through the blood.

Symptoms of entropion include:

- Redness and pain around the eye

- Sensitivity to light and wind

- Sagging skin around the eye

- Epiphora

- Decreased vision, especially if the cornea is damaged

Eye care during general anaesthesia is an important part of anaesthesia care. Eye injuries are reasonably common if care is not taken to prevent them.

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.

A distichia is an eyelash that arises from an abnormal spot on the eyelid. This abnormality, attributed to a genetic mutation, is known to affect dogs and humans. Distichiae (the abnormal eyelash) usually exit from the duct of the meibomian gland at the eyelid margin. They are usually multiple and sometimes more than one arises from a duct. They can affect either the upper or lower eyelid and are usually bilateral. The lower eyelids of dogs usually have no eyelashes.

Distichiae usually cause no symptoms because the lashes are soft, but they can irritate the eye and cause tearing, squinting, inflammation, and corneal ulcers and scarring. Treatment options include manual removal, electrolysis, electrocautery, cryotherapy, and surgery.

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.

Entropion is a medical condition in which the eyelid (usually the lower lid) folds inward. It is very uncomfortable, as the eyelashes continuously rub against the cornea causing irritation. Entropion is usually caused by genetic factors. This is different from when an extra fold of skin on the lower eyelid causes lashes to turn in towards the eye (epiblepharon). In epiblepharons, the eyelid margin itself is in the correct position, but the extra fold of skin causes the lashes to be misdirected. Entropion can also create secondary pain of the eye (leading to self trauma, scarring of the eyelid, or nerve damage). The upper or lower eyelid can be involved, and one or both eyes may be affected. When entropion occurs in both eyes, this is known as "bilateral entropion." Repeated cases of trachoma infection may cause scarring of the inner eyelid, which may cause entropion. In human cases, this condition is most common to people over 60 years of age.

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.

It is a characterized by a breakdown or damage of the epithelium of the cornea in a pinpoint pattern, which can be seen with examination with a slit-lamp. Patients may present with non-specific symptoms such as red eye, tearing, foreign body sensation, photophobia and burning.

Lagophthalmos can arise from a malfunction of the facial nerve. Lagopthalmos can also occur in comatose patients having a decrease in orbicularis tone, in patients having palsy of the facial nerve (7th cranial nerve), in people with severe exophthalmos, and in people with severe skin disorders such as ichthyosis.

Today, lagophthalmos may arise after an overenthusiastic upper blepharoplasty. Blepharoplasty is an operation performed to remove excessive skin overlying the upper eyelid (suprapalpebral hooding) that often occurs with aging. This can appreciably improve the patient's appearance, and make the patient look younger. If, however, excessive skin is removed, the appearance is unnatural and "lagophthalmos" is one of the signs of such excessive skin removal.

An ectopic cilia is a special type of distichia. It is usually found in younger dogs. Commonly affected breeds include Poodles, Golden Retrievers, and Shih Tzus. The eyelash exits through the conjunctiva of the eyelid facing toward the eye, usually at the middle of the upper eyelid. It can cause intense pain and corneal ulcers. Treatment is surgery or cryotherapy.

Cherry eye is most common in young dogs, especially breeds such as Cavalier King Charles Spaniel, English Bulldog, Lhasa Apso, Shih Tzu, West Highland White Terrier, Pug, Bloodhound, American Cocker Spaniel, and Boston Terrier Cherry eye is rare in felines, but can occur. This defect is most common in the Burmese breed of felines. A similar condition exists in dwarf lop-eared rabbits, which occurs in the harderian gland. Similar surgical treatment is necessary.

Cherry eye is not considered a genetic problem, as no proof of inheritance has been determined. The NM contains many glands which merge and appear as a single gland. Typically, glands secrete tears for lubrication of the cornea. Lack of anchoring allows the gland to flip up, causing the gland to prolapse.

Symptoms include a visible fleshy mass, abnormal tear production, and a discharge or drainage from the eye. Cherry eye is typically diagnosed by examination of the conjunctiva and nictitating membrane. The most obvious symptom of cherry eye is a round fleshy mass through medial canthus of the eye, similar in appearance to the fruit it is named for. This mass may be unilateral or ‘’bilateral’’. Both eyes may develop cherry eye at different times in the animal’s life. Other symptoms of cherry eye include drainage from the eye and abnormal tear production. Initially, cherry eye results in overproduction of tears, but eventually changes to unsubstantial tear production.

Cherry eye is a disorder of the nictitating membrane (NM), also called the third eyelid, present in the eyes of dogs and cats. Cherry eye is most often seen in young dogs under the age of two. Common misnomers include adenitis, hyperplasia, adenoma of the gland of the third eyelid; however, cherry eye is not caused by hyperplasia, neoplasia, or primary inflammation. In many species, the third eyelid plays an essential role in vision by supplying oxygen and nutrients to the eye via tear production. Normally, the gland can evert without detachment. Cherry eye results from a defect in the retinaculum which is responsible for anchoring the gland to the periorbita. This defect causes the gland to prolapse and protrude from the eye as a red fleshy mass. Problems arise as sensitive tissue dries out and is subjected to external trauma Exposure of the tissue often results in secondary inflammation, swelling, or infection. If left untreated, this condition can lead to Keratoconjunctivitis sicca (KCS) and other complications.

Punctate epithelial erosions is a pathology affecting the cornea. It is also known as punctate erosive keratopathy or superficial punctate keratitis.

Common signs and symptoms of orbital cellulitis include pain with eye movement, sudden vision loss, chemosis, bulging of the infected eye, and limited eye movement. Along with these symptoms, patients typically have redness and swelling of the eyelid, pain, discharge, inability to open the eye, occasional fever and lethargy. It is usually caused by a previous sinusitis. Other causes include infection of nearby structures, trauma and previous surgery.