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Synechia: Adhesions between eye structures

In synechia, deformities or adhesions occur between adjacent eye structures. The formation of synechia often occurs during inflammation and the proliferation of cells (cellular proliferation). This results in the patient developing glaucoma. These adhesions occur due to some (congenital) (eye) conditions, due to surgery or due to the use of medication. The patient complains of headaches and has reduced vision due to deformity of the eye structures. The ophthalmologist and/or doctor treats the underlying cause of synechia, and he also uses medication to remove the adhesions. A complication of synechia is glaucoma, an eye condition in which the intraocular pressure is often increased.

  • Synonyms synechia
  • Eye disease epidemiology
  • Anatomy
  • Types of adhesions between eye structures
  • Causes: Eye disorders, medication and surgery
  • Symptoms
  • Diagnosis and examinations
  • Treatment with medication
  • Complication is glaucoma
  • Eye disease prognosis


Synonyms synechia

Synechie is also known under these synonyms:

  • Synechia (singular)
  • Synechiae (plural)


Eye disease epidemiology

Synechiae can develop at any age, but the risk of this eye condition is higher in old age because the depth of the anterior chamber decreases with aging. Synechiae are also more common in women compared to men.


The iris is the colored part inside the eye. The pupil is the circular black area in the center of the iris through which light enters the eyes. Behind the iris, there is a lens that focuses light for good vision. The space in the front of the lens contains a clear fluid known as aqueous humor. Aqueous humor, which provides nourishment to the internal eye structures, flows into a meshwork of canals, better known as the trabecular meshwork. This is located at the base of the iris (or near the corner of the eye). The aqueous humor leaves the eyes through this trabecular network.

Types of adhesions between eye structures

When adhesions form between the iris and the cornea or the trabecular system at the front, this is called synechia iridis anterior or anterior synechia. The adhesion may also be part of the iris with the lens at the back (lens capsule), which is then known as synechia iridis posterior or posterior synechia.

Causes: Eye disorders, medication and surgery

Patients with synechia usually have an underlying inflammatory process. Posterior synechia is the result of keratitis (inflammation of the cornea of the eye), uveitis (inflammation of the uvea, the middle layer of the eye), glaucoma (increased intraocular pressure) or cataract (cataract: cloudy lens of the eye). Anterior synechia and posterior synechia may also be due to eye trauma or a complication of eye surgery. Presumably, inflammation causes a deposition of fibrin and proteins, which stimulates the formation of adhesions between structures. Synechiae form when the iris remains in close contact with the cornea and lens for an extended period of time.


Several patients are born with abnormally developed eyes. They have a lower depth of the anterior chamber or an abnormally shaped iris due to, for example, neurofibromatosis (neurological disorder with abnormalities of the skin and eyes) or iris atrophy (death of the iris). In some patients, abnormal blood vessels form in the eyes before birth. This eye disorder is known as premature retinopathy.


Iritis is an eye condition in which the iris is inflamed and swollen. The swelling brings the iris closer to the cornea or lens capsule. In addition, the iris moves less with iritis. This causes prolonged adhesion of the iris to the structures surrounding it, leading to the formation of synechiae. Iritis occurs due to a buildup of immune cells in the iris. The eye condition is due to autoimmune diseases such as rheumatoid arthritis (chronic autoimmune condition with inflammation of joints and other organs), ankylosing spondylitis or systemic lupus erythematosus. Bacterial infections, such as syphilis (bacterial infection through sexual contact), toxoplasmosis (parasitic infection with symptoms in the brain, lungs, heart, eyes and/or liver), tuberculosis (bacterial infection with lung problems) or viruses may also cause iritis. Injuries to the eye cause hyphemia, a bleeding in the anterior chamber of the eye. The pooled blood may result in iritis. The chance that synechiae will follow iritis increases as iritis is chronic.

Narrow angle glaucoma

The aqueous humor in the eye flows into the trabecular system located at the base of the iris (corner of the eye). In some patients, this angle is narrow, which prevents the aqueous humor from draining and accumulates in the eye. As a result, the pressure in the eye increases, pushing the iris forward. When this happens, the iris comes into close contact with the cornea or trabecular system, which increases the risk of synechiae.

Medication use

Patients with certain eye conditions such as glaucoma or iritis may take certain medications, such as cycloplegics or antihistamines (drugs for allergic reactions). These drugs either cause forward movement or else thickening of the iris, leading to the formation of synechiae.

Eye surgery

Eye surgery increases the risk of synechiae, because the risk of infection and inflammation of the iris increases.


One or both eyes are affected. The patient has reduced visual acuity (blurred vision). Headaches and seeing halos around illuminating objects such as lamps are also common features of synechia. These symptoms cause mild vision loss. The eye pressure is also increased, which causes greater vision loss in a later phase. Sometimes patients have no symptoms at all.

Diagnosis and examinations

Eye examination

The diagnosis is made on the basis of a slit lamp examination, an ophthalmoscopy (examination of the back of the eye) with gonioscopy of the angle structures in glaucoma.

Differential diagnosis

The ophthalmologist may confuse the following conditions with synechia:

  • a choroidal detachment
  • an iris melanoma
  • an ocular melanoma
  • glaucoma
  • herpes simplex
  • herpes zoster
  • irritable bowel syndrome (symptoms of diarrhea and constipation)
  • HLA-B27 syndromes
  • hyphemia
  • lens dislocation: Displacement of the lens of the eye
  • neurofibromatosis type 1
  • ocular hypotonia
  • ocular toxoplasmosis (parasitic eye infection)
  • phacoanaphylaxis
  • premature retinopathy (retinal disease resulting from premature birth)
  • pseudophakic pupillary block
  • Sarcoidosis: Disease of the skin, lungs, eyes and nervous system
  • Scleritis: Severe eye inflammation of the sclera (outer hard membrane)
  • traumatic cataract
  • uveitis


Treatment with medication

The ophthalmologist treats the underlying cause of synechia. Cycloplegics and mydriatics (eye pupil dilating drugs) also prevent and break down adhesions. Anti-inflammatory drugs often prevent the further formation of synechia. Suppressing the inflammation is done with corticosteroids. Furthermore, the patient uses eye pressure-lowering eye drops according to correct eye drop guidelines. Sometimes surgery is necessary.

Complication is glaucoma

Both anterior and posterior synechia iris cause glaucoma, but each has a different mechanism.

Eye disease prognosis

If the pupil can be completely dilated with the drugs during the treatment of iritis, the prognosis for recovery from synechia is good.

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