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.

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

The characteristic features of the syndrome are:

- Limitation of abduction (outward movement) of the affected eye.

- Less marked limitation of adduction (inward movement) of the same eye.

- Retraction of the eyeball into the socket on adduction, with associated narrowing of the palpebral fissure (eye closing).

- Widening of the palpebral fissure on attempted abduction. (N. B. Mein and Trimble point out that this is "probably of no significance" as the phenomenon also occurs in other conditions in which abduction is limited.)

- Poor convergence.

- A head turn to the side of the affected eye to compensate for the movement limitations of the eye(s) and to maintain binocular vision.

While usually isolated to the eye abnormalities, Duane syndrome can be associated with other problems including cervical spine abnormalities Klippel-Feil syndrome, Goldenhar syndrome, heterochromia, and congenital deafness.

Measurement of the degree of exophthalmos is performed using an exophthalmometer.

Most sources define exophthalmos/proptosis as a protrusion of the globe greater than 18 mm.

The term exophthalmos is often used when describing proptosis associated with Graves' disease.

In addition to small palpebral fissures, features include epicanthus inversus (fold curving in the mediolateral direction, inferior to the inner canthus), low nasal bridge, ptosis of the eyelids and telecanthus.

In the clinical setting, the principal difficulties in differential diagnosis arise as a consequence of the very early age at which patients with this condition first present. The clinician must be persistent in examining abduction and adduction, and in looking for any associated palpebral fissure changes or head postures, when attempting to determine whether what often presents as a common childhood squint (note-"squint" is a British term for two eyes not looking in the same direction) is in fact Duane syndrome. Fissure changes, and the other associated characteristics of Duane's such as up or down shoots and globe retraction, are also vital when deciding whether any abduction limitation is the result of Duane's and not a consequence of VI or abducens cranial nerve palsy.

Acquired Duane's syndrome is a rare event occurring after peripheral nerve palsy.

Blepharophimosis syndrome is an autosomal dominant characterized by blepharophimosis (horizontal shortening of the palpebral fissures), ptosis (upper eyelid drooping, usually with the characteristics of congenital ptosis), epicanthus inversus (skin folds by the nasal bridge, more prominent lower than upper lid), and telecanthus (widening of the distance between the medial orbital walls). This syndrome is caused by mutations in the FOXL2 gene, either with premature ovarian failure (BPES type I) or without (BPES type II). It may also be associated with lop ears, ectropion, hypoplasia of superior orbital rims, and hypertelorism.

Proptosis is the anterior displacement of the eye from the orbit. Since the orbit is closed off posteriorly, medially and laterally, any enlargement of structures located within will cause the anterior displacement of the eye. Swelling or enlargement of the lacrimal gland causes inferior medial and anterior dislocation of the eye. This is because the lacrimal glands are located superiorly and laterally in the orbit.

The presence of a small eye within the orbit can be a normal incidental finding but in most cases it is abnormal and results in blindness. The incidence is 14 per 100,000 and the condition affects 3-11% of blind children.

The most prominent symptoms of BPES are horizontally narrow eyes (blepharophimosis), drooping eyelids (ptosis), and a fold of skin running from the side of the nose to the lower eyelid (epicanthus inversus). Other common symptoms include lack of an eyelid fold, widely spaced eyes (telecanthus), low nose bridge, and ear malformations (including cupping and incomplete development). Rare symptoms include microphthalmos (abnormally small eyes), tear ducts in the wrong location, and high arched palate. Female infertility can occur with type I BPES.

Anophthalmia, (Greek: ανόφθαλμος, "without eye"), is the medical term for the absence of one or both eyes. Both the globe (human eye) and the ocular tissue are missing from the orbit. The absence of the eye will cause a small bony orbit, a constricted mucosal socket, short eyelids, reduced palpebral fissure and malar prominence. Genetic mutations, chromosomal abnormalities, and prenatal environment can all cause anophthalmia. Anophthalmia is an extremely rare disease and is mostly rooted in genetic abnormalities. It can also be associated with other syndromes.

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.

Microphthalmia (Greek: μικρός "micros" = small; ὀφθαλμός "ophthalmos" = eye), also referred as microphthalmos, is a developmental disorder of the eye in which one (unilateral microphthalmia) or both (bilateral microphthalmia) eyes are abnormally small and have anatomic malformations. It is different from nanophthalmos in which the eye is small in size but has no anatomical alterations.

Hypertropia is a condition of misalignment of the eyes (strabismus), whereby the visual axis of one eye is higher than the fellow fixating eye.

Hypotropia is the similar condition, focus being on the eye with the visual axis lower than the fellow fixating eye.

Dissociated Vertical Deviation is a special type of hypertropia leading to slow upward drift of one or rarely both eyes, usually when the patient is inattentive.

Refractive errors such as hyperopia and Anisometropia may be associated abnormalities found in patients with vertical strabismus.

The vertical miscoordination between the two eyes may lead to

- Strabismic amblyopia, (due to deprivation / suppression of the deviating eye)

- cosmetic defect (most noticed by parents of a young child and in photographs)

- Face turn, depending on presence of binocular vision in a particular gaze

- diplopia or double vision - more seen in adults (maturity / plasticity of neural pathways) and suppression mechanisms of the brain in sorting out the images from the two eyes.

- cyclotropia, a cyclotorsional deviation of the eyes (rotation around the visual axis), particularly when the root cause is an oblique muscle paresis causing the hypertropia.

Causes of the one and a half syndrome include pontine hemorrhage, ischemia, tumors, infective mass lesions such as tuberculomas, and demyelinating conditions like multiple sclerosis.

CPEO is a slowly progressing disease. It may begin at any age and progresses over a period of 5–15 years. The first presenting symptom of ptosis is often unnoticed by the patient until the lids droop to the point of producing a visual field defect. Often, patients will tilt the head backwards to adjust for the slowly progressing ptosis of the lids. In addition, as the ptosis becomes complete, the patients will use the frontalis (forehead) muscle to help elevate the lids. The ptosis is typically bilateral, but may be unilateral for a period of months to years before the fellow lid becomes involved.

Ophthalmoplegia or the inability or difficulty to move the eye is usually symmetrical. As such, double vision is sometimes a complaint of these patients. The progressive ophthalmoplegia is often unnoticed till decreased ocular motility limits peripheral vision. Often someone else will point out the ocular disturbance to the patient. Patients will move their heads to adjust for the loss of peripheral vision caused by inability to abduct or adduct the eye. All directions of gaze are affected; however, downward gaze appears to be best spared. This is in contrast to progressive supranuclear palsy (PSP), which typically affects vertical gaze and spares horizontal gaze.

An imperforate lacrimal punctum is a congenital disorder of dogs involving the lack of an opening to the nasolacrimal duct (tear duct) in the conjunctiva. Dogs normally have two lacrimal puncta, the superior and inferior. This condition can affect either or both. Symptoms include excessive tearing and tear staining of the hair around the eye. Affected breeds include the American Cocker Spaniel, Bedlington Terrier, Golden Retriever, Poodle, and Samoyed. Imperforate lacrimal puncta can be corrected by surgical opening of the punctum.

Lid lag is the static situation in which the upper eyelid is higher than normal with the globe in downgaze. It is most often a sign of thyroid eye disease, but may also occur with cicatricial changes to the eyelid or congenital ptosis. Lid lag differs from Von Graefe's sign in that the latter is a dynamic process.It can also be the manifestaition of chemosis (swelling (or edema) of the conjunctiva)

There are three classifications for this condition:

- Primary anophthalmia is a complete absence of eye tissue due to a failure of the part of the brain that forms the eye.

- Secondary anophthalmia the eye starts to develop and for some reason stops, leaving the infant with only residual eye tissue or extremely small eyes which can only be seen under close examination.

- Degenerative anophthalmia the eye started to form and, for some reason, degenerated. One reason for this occurring could be a lack of blood supply to the eye.

Signs that are found in patients on the affected side of the face include

- partial ptosis

- upside-down ptosis (slight elevation of the lower lid)

- anhidrosis

- miosis

- pseudoenophthalmos (the impression that the eye is sunken, caused by a narrow palpebral aperture)

- pupillary dilation lag

- loss of ciliospinal reflex

- bloodshot conjunctiva, depending on the site of lesion.

- unilateral straight hair (in congenital Horner's syndrome); the hair on the affected side may be straight in some cases.

- heterochromia iridum (in congenital Horner's syndrome)

Interruption of sympathetic pathways leads to several implications. It inactivates the dilator muscle and thereby produces miosis. It inactivates the superior tarsal muscle which produces ptosis. It inactivates the orbitalis muscle which produces the effect of enophthalmos. It also reduces sweat secretion in the face.

Sometimes there is flushing on the affected side of the face due to dilation of blood vessels under the skin. The pupil's light reflex is maintained as this is controlled via the parasympathetic nervous system.

In children, Horner's syndrome sometimes leads to heterochromia, a difference in eye color between the two eyes. This happens because a lack of sympathetic stimulation in childhood interferes with melanin pigmentation of the melanocytes in the superficial stroma of the iris.

In veterinary medicine, signs can include partial closure of the third eyelid, or nictitating membrane.

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.

Weakness of extraocular muscle groups including, the orbicularis oculi muscle as well as facial and limb muscles may be present in up to 25% of patients with CPEO. As a result of the orbicularis oculi weakness, patients may suffer from exposure keratopathy (damage to cornea) from the inability to close the eyes tightly. Frontalis muscle weakness may exacerbate the ptotic lids with the inability to compensate for the ptosis. Facial muscles may be involved which lead to atrophy of facial muscle groups producing a thin, expressionless face with some having difficulty with chewing. Neck, shoulder and extremity weakness with atrophy may affect some patients and can be mild or severe.

Mild visual impairment was seen in 95% of patients that were evaluated using the Visual Function Index (VF-14).

The ciliary muscles that control the lens shape and the iris muscles are often unaffected by CPEO.

Additional symptoms are variable, and may include exercise intolerance, cataracts, hearing loss, sensory axonal neuropathy, ataxia, clinical depression, hypogonadism, and parkinsonism.

Kearns–Sayre syndrome is characterized by onset before 15 years of age of CPEO, heart block and pigmentary retinopathy.

Blepharophimosis, ptosis, epicanthus inversus syndrome or BPES is a rare disease characterized by the conditions it is named after: blepharophimosis, ptosis, and epicanthus inversus.

There have been cases of improvement in extra-ocular movement with botulinum toxin injection.