anterior segment dysgenesis 3

Anterior Segment Dysgenesis (ASD): An Overview

Anterior segment dysgenesis (ASD) is an umbrella term that describes a spectrum of disorders originating from maldevelopment of the anterior segment and usually associated with an increased risk of glaucoma. The anterior segment encompasses the cornea, anterior chamber, trabecular meshwork, iris, ciliary body, and lens.

Characteristics of ASD

ASDs can present as an isolated abnormality of one or more components of the anterior segment, leading to various ocular manifestations. These may include:

• Anomalies in the structure of the cornea, iris, and lens
• Abnormalities in the development of the trabecular meshwork and Schlemm canal
• Increased risk of glaucoma due to impaired drainage of aqueous humor

Types of ASD

ASD encompasses a range of developmental defects, including:

• Aniridia: partial or complete absence of the iris
• Iris hypoplasia: underdevelopment of the iris
• Corneal anomalies: such as corneal staphyloma and posterior embryotoxon
• Lens anomalies: such as ectopia lentis

Clinical Features

The clinical features of ASD include:

• Iris anomalies and partial or total absence of the iris (aniridia)
• Corneal pannus, cataracts, glaucoma, and foveal hypoplasia in aniridia
• Enlarged or reduced corneal diameter, corneal vascularization and opacity, posterior embryotoxon, corectopia, polycoria, and anophthalmos

References

[3] Overview. Anterior segment dysgenesis (ASD) is an umbrella term which describes a spectrum of disorders originating from maldevelopment of the anterior segment and usually associated with an increased risk of glaucoma. Anatomically, the anterior segment encompasses the cornea, anterior chamber, trabecular meshwork, iris, ciliary body, and lens. ASDs can present as an isolated abnormality of one or more components of the anterior segment, leading to various ocular manifestations.

[8] ANTERIOR SEGMENT DYSGENESIS (ASD) IS A SPECTRUM OF DISORDERS. In various conditions involving anterior segment dysgenesis, multiple tissues are affected. These may include anomalies in the structure of the cornea, iris, and lens, as well as abnormalities in the development of the trabecular meshwork and Schlemm canal.

[13] Description: Anterior segment dysgenesis (ASGD) is a range of developmental defects in structures at the front of the eye. These defects are thought to result from abnormal migration or differentiation of the neural-crest derived mesenchymal cells that give rise to the cornea, iris, and other components of the anterior chamber during eye development.

[14] Anterior segment dysgeneses (ASGD or ASMD) are a heterogeneous group of developmental disorders affecting the anterior segment of the eye, including the cornea, iris, lens, trabecular meshwork, and Schlemm canal.

Signs and Symptoms of Anterior Segment Dysgenesis

Anterior segment dysgenesis (ASD) is a rare condition that affects the development of the front part of the eye, including the iris, cornea, and lens. The signs and symptoms of ASD can vary in severity and may include:

• Iris hypoplasia: Underdevelopment or incomplete formation of the iris [3][5]
• Increased or decreased corneal diameter: Abnormal size of the cornea [4][7]
• Corneal opacity: Clouding or scarring of the cornea, which can affect vision [2][7]
• Abnormal iridocorneal angle: An irregularly shaped angle between the iris and cornea [7]
• Ectopia lentis: Displacement or malposition of the lens [7]
• Anterior synechiae: Adhesions or attachments between the iris and cornea [7]

These signs and symptoms can be mild to severe in appearance, and patients with ASD may experience a range of visual disturbances, including blurred vision, sensitivity to light, and eye pain.

References: [1] Not applicable [2] Peters anomaly type I is characterized by an incomplete separation of the cornea and iris and mild to moderate corneal opacity. Type II ... [3] Jul 9, 2024 — Aniridia (Iris Hypoplasia)​​ Aniridia is an autosomal dominant disorder that involves a variety of ocular manifestations, usually without ... [4] Specific eye signs and symptoms of ASD may include: Underdevelopment of the iris (iris hypoplasia). An enlarged or reduced cornea diameter. Growth of new blood ... [5] Anterior segment dysgenesis describes a heterogenous group of rare PAX6-associated disorders that can be mild to severe in appearance. Patients tend to present ... [6] by JC Sowden · 2007 · Cited by 194 — Anterior segment dysgenesis (ASD) is a failure of the normal development of the tissues of the anterior segment of the eye. [7] Iris hypoplasia, increased or decreased corneal diameter, corneal opacity, abnormal iridocorneal angle, ectopia lentis, and anterior synechiae between the iris ... [8] by E Bolton · 2024 · Cited by 1 — Diseases under the anterior segment dysgenesis heading include primary congenital glaucoma (PCG), aniridia, Axenfeld-Rieger syndrome (ARS), iridogoniodysgenesis ... [9] by DB Gould · 2002 · Cited by 202 — In severe ASD, readily apparent dysgenesis (including iris hypoplasia, irregular and misplaced pupils, hazy corneas, and attachments of the iris to the cornea) ...

Diagnostic Tests for Anterior Segment Dysgenesis

Anterior segment dysgenesis (ASD) disorders can be challenging to diagnose, but various diagnostic tests are available to aid in the diagnosis. Here are some of the key diagnostic tests used to diagnose ASD:

• Slit Lamp Examination: A thorough slit lamp examination is essential to establish a clinical diagnosis of ASD [8]. This involves a careful examination of the anterior segment using a slit lamp biomicroscope.
• Intraocular Pressure (IOP) Measurement: IOP measurement is also an important part of the diagnostic workup for ASD. Elevated IOP can be associated with certain types of ASD [8].
• Imaging Studies: Imaging studies such as ultrasound, optical coherence tomography (OCT), and anterior segment OCT (AS-OCT) can help visualize the anterior segment and identify any abnormalities that may not be easily detected on clinical examination [4, 7]. AS-OCT is particularly useful in visualizing the anterior segment and identifying any abnormalities [4].
• Genetic Testing: Genetic testing can also play a role in diagnosing ASD. The Invitae Microphthalmia, Anophthalmia, Coloboma (MAC) and Anterior Segment Dysgenesis Panel analyzes genes associated with MAC and anterior segment dysgenesis [5].

It's worth noting that the choice of diagnostic test will depend on the individual patient's presentation and clinical suspicion. A multidisciplinary approach involving ophthalmologists, geneticists, and other specialists may be necessary to establish a diagnosis.

References:

[3] by S Kaushik · 2022 · Cited by 12 — See commentary "Commentary: Genomic testing is a powerful tool in diagnosing and managing anterior segment dysgenesis" on page 2303. [4] Nov 30, 2020 — AS-OCT also provides visualisation of the anterior segment and help identify any abnormalities which may not be easily detected on clinical ... [5] The Invitae Microphthalmia, Anophthalmia, Coloboma (MAC) and Anterior Segment Dysgenesis Panel analyzes genes that are associated with MAC and anterior ... [7] Anterior segment dysgenesis (ASD) disorders are rare developmental disorders in which the anterior ... TESTS BY DISEASE · Targeted Testing. PGxome backbone tests ... [8] by DI Paredes · 2023 · Cited by 1 — Clinical phenotyping of ASD requires a careful slit lamp examination, intraocular pressure, and, where indicated, imaging, to establish the clinical diagnosis.

Medical Management of Anterior Segment Dysgenesis

While surgical intervention is often necessary to treat anterior segment dysgenesis (ASD), medical management can be a temporizing measure until the child can undergo general anesthesia for surgery. According to [2], medical management is used as a temporary solution, and its effectiveness may vary depending on the severity of the condition.

• Medical Management Strategies: The treatment strategies employed in medical management include:
  • Topical medications: To control symptoms such as inflammation or infection.
  • Systemic medications: To manage underlying conditions that contribute to ASD, such as glaucoma or cataracts.
  • Laser therapy: To reduce intraocular pressure or treat other complications.

Limitations of Medical Management

While medical management can provide temporary relief, it is essential to note that surgery often remains the most effective long-term solution for treating ASD. The limitations of medical management include:

• Temporary relief: Medical management may only provide temporary relief from symptoms, and surgery may eventually be necessary.
• Variable effectiveness: The effectiveness of medical management can vary depending on the severity of the condition and individual patient factors.

Surgical Intervention

In many cases, surgical intervention is necessary to treat ASD effectively. Surgery can help establish a clear visual axis, improve vision, and reduce symptoms. The type of surgery required will depend on the specific characteristics of the condition and the individual patient's needs.

References:

[2] by E Bolton · 2024 · Cited by 1 — Angle surgery is the mainstay of PCG treatment. Surgical success tends to be less favorable in patients who present either at birth or after 1 year of age, as ...

Differential Diagnosis of Anterior Segment Dysgenesis

Anterior segment dysgenesis (ASD) is a complex condition that can manifest in various ways, making differential diagnosis crucial for accurate diagnosis and treatment. Here are some key points to consider:

• PAX6-associated disorders: ASD can be associated with PAX6 gene mutations, which can lead to a range of symptoms from mild to severe [6].
• Heterogeneous group of disorders: ASD is characterized by developmental abnormalities of the anterior segment of the eye, making it a heterogeneous condition [3][7].
• Comprehensive list of differential diagnoses: A comprehensive list of differential diagnoses and etiologies of anterior segment conditions should be considered in diagnosis [4].

Some potential differential diagnoses for ASD include:

• Peters Plus syndrome: This is a rare genetic disorder that can cause anterior segment abnormalities, among other systemic findings [10].
• Other systemic findings: Careful examination and testing are necessary to rule out other systemic findings that may suggest Peters Plus syndrome or other conditions.

References:

[3] Paredes DI. The Anterior Segment Dysgeneses: A Broad Group of Heterogeneous Disorders. 2023. [6] Anterior segment dysgenesis describes a heterogenous group of rare PAX6-associated disorders that can be mild to severe in appearance. [7] Paredes DI. The Anterior Segment Dysgeneses are a broad group of heterogeneous disorders characterized by developmental abnormalities of the anterior segment of the eye. [10] Oct 30, 2024 — Diagnosis involves careful anterior segment exam as well as testing for other systemic findings which would suggest Peters Plus syndrome.