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.

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

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.

Symptoms include recurring attacks of severe acute ocular pain, foreign-body sensation, photophobia (i.e. sensitivity to bright lights), and tearing often at the time of awakening or during sleep when the eyelids are rubbed or opened. Signs of the condition include corneal abrasion or localized roughening of the corneal epithelium, sometimes with map-like lines, epithelial dots or microcysts, or fingerprint patterns. An epithelial defect may be present, usually in the inferior interpalpebral zone.

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.

Blepharochalasis results from recurrent bouts of painless eyelid swelling, each lasting for several days. This is thought to be a form of localized angioedema, or rapid accumulation of fluid in the tissues. Recurrent episodes lead to thin and atrophic skin. Damage to the levator palpebrae superioris muscle causes ptosis, or drooping of the eyelid, when the muscle can no longer hold the eyelid up.

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.

Most cases of recurrent corneal erosion are acquired. There is often a history of recent corneal injury (corneal abrasion or ulcer), but also may be due to corneal dystrophy or corneal disease. In other words, one may suffer from corneal erosions as a result of another disorder, such as map-dot fingerprint dystrophy. Familial corneal erosions occur in dominantly inherited recurrent corneal erosion dystrophy (ERED) in which COL17A1 gene is mutated..

Dermatochalasis is sometimes confused with blepharochalasis, but these are two different conditions.

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.

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

Typical symptoms of dry eye syndrome are dryness, burning and a sandy-gritty eye irritation that gets worse as the day goes on. Symptoms may also be described as itchy, scratchy, stinging or tired eyes. Other symptoms are pain, redness, a pulling sensation, and pressure behind the eye. There may be a feeling that something, such as a speck of dirt, is in the eye. The resultant damage to the eye surface increases discomfort and sensitivity to bright light. Both eyes usually are affected.

There may also be a stringy discharge from the eyes. Although it may seem strange, dry eye can cause the eyes to water. This can happen because the eyes are irritated. One may experience excessive tearing in the same way as one would if something got into the eye. These reflex tears will not necessarily make the eyes feel better. This is because they are the watery type that are produced in response to injury, irritation, or emotion. They do not have the lubricating qualities necessary to prevent dry eye.

Because blinking coats the eye with tears, symptoms are worsened by activities in which the rate of blinking is reduced due to prolonged use of the eyes. These activities include prolonged reading, computer usage, driving, or watching television. Symptoms increase in windy, dusty or smoky (including cigarette smoke) areas, in dry environments high altitudes including airplanes, on days with low humidity, and in areas where an air conditioner (especially in a car), fan, heater, or even a hair dryer is being used. Symptoms reduce during cool, rainy, or foggy weather and in humid places, such as in the shower.

Most people who have dry eyes experience mild irritation with no long-term effects. However, if the condition is left untreated or becomes severe, it can produce complications that can cause eye damage, resulting in impaired vision or (rarely) in the loss of vision.

Symptom assessment is a key component of dry eye diagnosis – to the extent that many believe dry eye syndrome to be a symptom-based disease. Several questionnaires have been developed to determine a score that would allow for dry eye diagnosis. The McMonnies & Ho dry eye questionnaire is often used in clinical studies of dry eyes.

Any abnormality of any one of the three layers of tears produces an unstable tear film, resulting in symptoms of dry eyes.

Dermatochalasis is caused by a loss of elasticity in the connective tissue supporting the structure of the front portion of the eyelid. Normally, in Caucasians, the orbicularis muscle and overlying skin form a crease near the tarsal border. In dermatochalasis, the excess tissues hangs down, over the front edge of the eyelid. The excess tissue can sometimes obstruct the visual field, especially the superior visual field. In severe cases, it may obstruct as much as 50 percent of the superior visual field.

Ectropion in dogs usually involves the lower eyelid. Often the condition has no symptoms, but tearing and conjunctivitis may be seen. Breeds associated with ectropion include the Cocker Spaniel, the Saint Bernard, the Bloodhound, the Clumber Spaniel, and the Basset Hound. It can also result from trauma or nerve damage. Treatment (surgery) is recommended only if there is chronic conjunctivitis or if there is corneal damage. A small part of the affected lid is removed and then the lid is sewn back together.

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.

A symblepharon is a partial or complete adhesion of the palpebral conjunctiva of the eyelid to the bulbar conjunctiva of the eyeball. It results either from disease (conjunctival sequelae of trachoma) or trauma. Cicatricial pemphigoid and, in severe cases, rosacea may cause symblepharon. It is rarely congenital. and its treament

1 ocular movements restricted

2 diplopia

3 lagophthalmos

4 cosmetic cause

types.

Anterior, adhesion in Anterior part

Posterior, adhesion in only fornices

total, adhesion involves whole lens

Complications.

prophylaxis, 1 sweeping a glass rod around fornices several times a day

2 therapeutic soft contact lens

curative treatment t, 1 mobilising surrounding cornea, 2 conjunctival or buccal mucosa graft, 3 amniotic membrane transplant

People with dermatochalasis often also have blepharitis, a condition caused by the plugging of glands in the eye that produce lubricating fluid (meibomian glands). Dermatochalasis can be severe enough that it pushes the eyelashes into the eye, causing entropion.

Weakness in the orbital septum may cause the herniation of the orbital fat pads. This is observed as the presence of bulges (fat pads) in the soft tissue of the baggy eyes.

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.

Depending upon the cause it can be classified into:

- "Neurogenic ptosis" which includes oculomotor nerve palsy, Horner's syndrome, Marcus Gunn jaw winking syndrome, third cranial nerve misdirection.

- "Myogenic ptosis" which includes oculopharyngeal muscular dystrophy, myasthenia gravis, myotonic dystrophy, ocular myopathy, simple congenital ptosis, blepharophimosis syndrome

- "Aponeurotic ptosis" which may be involutional or post-operative

- "Mechanical ptosis" which occurs due to edema or tumors of the upper lid

- "Neurotoxic ptosis" which is a classic symptom of envenomation by elapid snakes such as cobras, kraits, mambas and taipans. Bilateral ptosis is usually accompanied by diplopia, dysphagia and/or progressive muscular paralysis. Regardless, neurotoxic ptosis is a precursor to respiratory failure and eventual suffocation caused by complete paralysis of the thoracic diaphragm. It is therefore a medical emergency and immediate treatment is required. Similarly, ptosis may occur in victims of Botulism (caused by Botulinum toxin) and this is also regarded as a life-threatening symptom

- "Pseudo ptosis" due to:

1. Lack of lid support: empty socket or atrophic globe.

2. Higher lid position on the other side: as in lid retraction

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.

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.

Myasthenia gravis is a common neurogenic ptosis which could be also classified as neuromuscular ptosis because the site of pathology is at the neuromuscular junction. Studies have shown that up to 70% of myasthenia gravis patients present with ptosis, and 90% of these patients will eventually develop ptosis. In this case, ptosis can be unilateral or bilateral and its severity tends to be oscillating during the day, because of factors such as fatigue or drug effect. This particular type of ptosis is distinguished from the others with the help of a Tensilon challenge test and blood tests. Also, specific to myasthenia gravis is the fact that coldness inhibits the activity of cholinesterase, which makes possible differentiating this type of ptosis by applying ice onto the eyelids. Patients with myasthenic ptosis are very likely to still experience a variation of the drooping of the eyelid at different hours of the day.

The ptosis caused by the oculomotor palsy can be unilateral or bilateral, as the subnucleus to the levator muscle is a shared, midline structure in the brainstem. In cases in which the palsy is caused by the compression of the nerve by a tumor or aneurysm, it is highly likely to result in an abnormal ipsilateral papillary response and a larger pupil. Surgical third nerve palsy is characterized by a sudden onset of unilateral ptosis and an enlarged or sluggish pupil to the light. In this case, imaging tests such as CTs or MRIs should be considered. Medical third nerve palsy, contrary to surgical third nerve palsy, usually does not affect the pupil and it tends to slowly improve in several weeks. Surgery to correct ptosis due to medical third nerve palsy is normally considered only if the improvement of ptosis and ocular motility are unsatisfactory after half a year. Patients with third nerve palsy tend to have diminished or absent function of the levator.

When caused by Horner's syndrome, ptosis is usually accompanied by miosis and anhidrosis. In this case, the ptosis is due to the result of interruption innervations to the sympathetic, autonomic Muller's muscle rather than the somatic levator palpebrae superioris muscle. The lid position and pupil size are typically affected by this condition and the ptosis is generally mild, no more than 2 mm. The pupil might be smaller on the affected side. While 4% cocaine instilled to the eyes can confirm the diagnosis of Horner's syndrome, Hydroxyamphetamine eye drops can differentiate the location of the lesion.

Chronic progressive external ophthalmoplegia is a systemic condition that occurs and which usually affects only the lid position and the external eye movement, without involving the movement of the pupil. This condition accounts for nearly 45% of myogenic ptosis cases. Most patients develop ptosis due to this disease in their adulthood. Characteristic to ptosis caused by this condition is the fact that the protective up rolling of the eyeball when the eyelids are closed is very poor.

Von Graefe's sign is the lagging of the upper eyelid on downward rotation of the eye, indicating exophthalmic goiter (Graves' Disease). It is a dynamic sign, whereas lid lag is a static sign which may also be present in cicatricial eyelid retraction or congenital ptosis.

A pseudo Graefe's sign (pseudo lid lag) shows a similar lag, but is due to aberrant regeneration of fibres of the oculomotor nerve (III) into the elevator of the upper lid. It occurs in paramyotonia congenita.

A pseudo Graefe's sign is most commonly manifested in just one eye but can occasionally be observed in both. The reason only one eye is affected is not yet clear.

Stye complications occur in very rare cases. However, the most frequent complication of styes is progression to a chalazion that causes cosmetic deformity, corneal irritation, and often requires surgical removal. Complications may also arise from the improper surgical lancing, and mainly consist of disruption of lash growth, lid deformity or lid fistula. Styes that are too large may interfere with one's vision.

Eyelid cellulitis is another potential complication of eye styes, which is a generalized infection of the eyelid. Progression of a stye to a systemic infection (spreading throughout the body) is extremely rare, and only a few instances of such spread have been recorded.