What are the other Names for this Condition? (Also known as/Synonyms)

• PE (Posterior Embryotoxon)

What is Posterior Embryotoxon? (Definition/Background Information)

• Posterior Embryotoxon (PE) is a type of corneal abnormality that manifests as an opaque/solid ring in the cornea (Schwalbe's ring). It may occur in isolation or form part of a group of disorders named anterior segment developmental anomalies. PE is usually identified via a slit-lamp examination
• Anterior segment developmental anomalies (ASDA) refer to a group of developmental disorders that involve the anterior segment region of the eye. These disorders are also termed anterior segment dysgenesis (ASD). The anterior segment anatomical region includes the cornea, lens, iris, and aqueous humor that nourishes the eye
• Posterior Embryotoxon is usually observed along-with another ASDA conditions, such as Axenfeld-Rieger syndrome, and in individuals with Alagille syndrome (a genetic disorder affecting the heart and liver)
• Typically, Posterior Embryotoxon in isolation (sporadic Posterior Embryotoxon) does not adversely affect vision. However, a diagnosis of syndromic Posterior Embryotoxon may indicate the presence of other associated conditions, such as anterior segment abnormalities, which may require suitable treatment due to an elevated risk for glaucoma

Who gets Posterior Embryotoxon? (Age and Sex Distribution)

• According to research studies, the prevalence of Posterior Embryotoxon among the general population is around 7%
• Individuals of any age category may be affected including children, teens, and young and old adults. A large number of cases are diagnosed by or before the age of 20 years
• Both males and females may be affected
• Worldwide, individuals of all races and ethnicity are prone to developing the condition

What are the Risk Factors for Posterior Embryotoxon? (Predisposing Factors)

No specific risk factors for sporadic Posterior Embryotoxon are identified. The condition occurs at a higher incidence rate with other genetic disorders (syndromic Posterior Embryotoxon). These include:

• Alagille syndrome (arterio-hepatic dysplasia) - around 95% of the individuals with this syndrome present Posterior Embryotoxon
• Axenfeld-Rieger syndrome, an autosomal dominant condition, which forms part of anterior segment dysgenesis (ASD) group of disorders, is often observed with Posterior Embryotoxon
• X-linked ichthyosis - an inherited skin condition
• Familial aniridia - part of anterior segment dysgenesis (ASD) group of disorders

A family history of the above conditions can increase one’s risk for Posterior Embryotoxon.

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Posterior Embryotoxon? (Etiology)

• The cause of Posterior Embryotoxon is not clearly understood. It manifests as a solid corneal ring and is normally asymptomatic
• The condition may be seen in isolation (sporadic Posterior Embryotoxon) or, in association with other genetic disorders notably Axenfeld-Rieger syndrome and Alagille syndrome
• When noted in the presence of associated (familial) conditions, it may be caused by an inherited gene mutation, and usually involves both eyes (bilateral)

In individuals with anterior segment developmental anomalies (ASDA), frequent disruptions in the aqueous humor production and drainage pathways result in complications, such as increased intraocular pressure, and consequently glaucoma.

Syndromic Posterior Embryotoxon is caused by maldevelopment of the neural crest cells occurring during fetal growth and development.

What are the Signs and Symptoms of Posterior Embryotoxon?

In general, Posterior Embryotoxon does not present any significant signs and symptoms in isolation. However, signs and symptoms of any associated conditions may be noted. The condition may involve one or both eyes.

How is Posterior Embryotoxon Diagnosed?

Posterior Embryotoxon may be diagnosed by the following observations and tests:

• Physical examination and medical history evaluation
• Assessment of signs and symptoms
• General eye exam including:
  • Fundoscopic (ophthalmoscopic) examination by an eye specialist, who examines the back part of the eye (or the fundus)
  • Visual acuity test using a special and standardized test chart (Snellen chart)
  • Slit-lamp examination
  • Gonioscopy, a painless eye exam using special devices
  • Visual evoked potential (VEP) test
  • Fundus fluorescein angiography is important in diagnosing Posterior Embryotoxon
  • Indocyanine green (ICG) angiography

Tests and procedures to diagnose the associated condition, if any present, are important.

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Posterior Embryotoxon?

No significant complications of Posterior Embryotoxon are typically noted.

• There is an increased risk for glaucoma when other anterior segment anomalies are observed
• Complications may arise from the associated conditions, if any present

How is Posterior Embryotoxon Treated?

Generally, no treatment measures are required for Posterior Embryotoxon.

• A wait and watch approach may be considered by the healthcare provider
• Treating the associated condition is important to prevent secondary glaucoma

How can Posterior Embryotoxon be Prevented?

Presently, it is difficult to prevent sporadic forms of Posterior Embryotoxon. Syndromic forms of Posterior Embryotoxon may have a family history of the condition.

• If there is a family history of a medical condition, then genetic counseling will help assess risks, before planning for a child
• Undertaking early and adequate treatment of any health concerns is important

What is the Prognosis of Posterior Embryotoxon? (Outcomes/Resolutions)

The prognosis of Posterior Embryotoxon depends on the severity of the associated condition, if any present.

• Sporadic forms of Posterior Embryotoxon require no treatment as the condition does not affect vision
• In syndromic Posterior Embryotoxon, the overall prognosis depends on the severity of the associated genetic disorder

Additional and Relevant Useful Information for Posterior Embryotoxon:

Please visit our Eye & Vision Health Center for more physician-approved health information:

https://www.dovemed.com/health-topics/vision-center/