anterior segment dysgenesis 7

Anterior Segment Dysgenesis (ASD) Description

Anterior segment dysgenesis, also known as ASD, is a failure of the normal development of the tissues of the anterior segment of the eye [7]. This condition involves the cornea, iris, and other structures in the front portion of the eye.

The anterior segment of the eye includes the sclera, cornea, iris, trabecular meshwork, and ciliary body. In ASD, these structures may not develop properly, leading to various abnormalities and conditions [4].

ASD is a congenital condition, meaning it is present at birth. It can be caused by genetic mutations or other factors that affect the development of the eye during fetal growth [6]. The exact mechanisms underlying this condition remain unclear, but research suggests that multiple tissues are affected in various conditions involving ASD [8].

Some common features of ASD include:

• Corneal lesions and abnormalities
• Iris defects and colobomas (holes in the iris)
• Anterior chamber anomalies
• Ciliary body malformations

ASD can lead to severe visual impairment or blindness if left untreated. Early diagnosis and treatment are essential for managing this condition effectively.

References: [7] by JC Sowden · 2007 · Cited by 194 [4] Nov 30, 2020 [6] by E Bolton · 2024 · Cited by 1 [8] by DB Gould · 2002 · Cited by 202

Signs and Symptoms of Anterior Segment Dysgenesis

Anterior segment dysgenesis (ASD) is a rare developmental disorder that affects the front portion of the eye, including the cornea, iris, lens, trabecular meshwork, and Schlemm canal. The clinical features of ASD include:

• Iris hypoplasia: Underdevelopment or absence of the iris
• Enlarged or reduced corneal diameter: Abnormal size of the cornea
• Corneal vascularization and opacity: Growth of new blood vessels on the cornea, leading to clouding or scarring
• Posterior embryotoxon: A condition where a thin membrane forms in front of the iris
• Corectopia: Displacement or malposition of the pupil
• Polycoria: Presence of multiple pupils
• Aniridia: Complete absence of the iris

These symptoms can vary in severity and may be associated with other eye problems, such as glaucoma, cataracts, and corneal opacity. In some cases, individuals with ASD may also experience vision loss or blindness.

References:

• [7] Sowden JC (2007) Anterior segment dysgenesis: a review of the literature. Cited by 194.
• [13] Anterior segment dysgeneses (ASGD or ASMD) are a heterogeneous group of developmental disorders affecting the anterior segment of the eye... Cited by multiple sources.
• [14] 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... Cited by multiple sources.
• [12] Anterior segment dysgenesis leads to iris anomalies and even partial or total absence of the iris. Aniridia is a type of anterior segment dysgenesis that causes corneal pannus, cataracts, glaucoma, partial or complete absence of the iris, and foveal hypoplasia. It is rare and can be inherited in an autosomal dominant or recessive mode.

Diagnostic Tests for Anterior Segment Dysgenesis (ASD)

Anterior segment dysgenesis disorders, including microphthalmia, anophthalmia, and coloboma, can be challenging to diagnose. However, several diagnostic tests are available to help identify these conditions.

• Clinical examination: A thorough slit lamp examination is essential in diagnosing ASD. This involves a careful examination of the anterior segment, including the iris, cornea, and lens.
• Intraocular pressure measurement: Measuring intraocular pressure can help establish the clinical diagnosis of ASD.
• Imaging studies: Imaging studies such as ultrasound biomicroscopy (UBM), optical coherence tomography (OCT), and computed tomography (CT) scans can provide valuable information about the anterior segment and help identify any abnormalities.

According to [7], diagnostic tests for congenital microcoria include:

• Pupillary size measurement: In congenital microcoria, pupillary size should not change after administration of dilating drops, including 1% atropine.

Medical Management of Anterior Segment Dysgenesis

While surgical intervention is often necessary to establish a clear visual axis, medical management can be employed as a temporizing measure in some cases. However, the effectiveness of drug treatment for anterior segment dysgenesis (ASD) is limited.

• Glaucoma management: In patients with ASD and glaucoma, medications that decrease intraocular pressure (IOP) may be used to control symptoms [9].
• Mitomycin C trabeculectomy: This surgical procedure may be required in some cases of postkeratoplasty glaucoma, which can occur as a complication of corneal transplant surgery [10].

It's essential to note that medical management is often not sufficient to treat the underlying condition and may only provide temporary relief. Surgical intervention is usually necessary to address the root cause of ASD.

References: [9] - In case of glaucoma, the goal of treatment is to reach low IOP. Surgery is performed if eye drops are not sufficient in lowering IOP. [10] - Mitomycin C trabeculectomy and glaucoma drainage implant surgery may be required in treatment of postkeratoplasty glaucoma.

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:

• Primary developmental anomalies: ASD can result from primary defects in the migration and/or differentiation of neural crest cells, leading to abnormalities in the anterior segment of the eye [8].
• Heterogeneous disorders: ASD is a broad group of heterogeneous disorders characterized by developmental abnormalities of the anterior segment of the eye [3], [7].
• PAX6-associated disorders: Anterior segment dysgenesis can be associated with PAX6 mutations, which can lead to a range of ocular and systemic anomalies [6].

Differential Diagnoses

When considering differential diagnoses for ASD, it's essential to consider the following conditions:

• Glaucoma: Glaucoma is a common complication of ASD, particularly in cases where there are developmental abnormalities of the anterior segment [10].
• Cataracts: Cataracts can also be associated with ASD, especially in cases where there are abnormalities in the lens or cornea.
• Corneal abnormalities: Corneal abnormalities, such as opacities or thinning, can be seen in patients with ASD.
• Iris and pupil anomalies: Anomalies of the iris and pupil, such as colobomas or microphthalmia, can also be associated with ASD.

References

[3] by DI Paredes · 2023 · Cited by 1 — The anterior segment dysgeneses are a broad group of heterogeneous disorders characterized by developmental abnormalities of the anterior segment of the eye. [6] Anterior segment dysgenesis describes a heterogenous group of rare PAX6-associated disorders that can be mild to severe in appearance. Patients tend to present ... [7] by DI Paredes · 2023 · Cited by 1 — The anterior segment dysgeneses are a broad group of heterogeneous disorders characterized by developmental abnormalities of the anterior segment of the eye. [8] by DB Gould · 2002 · Cited by 202 — ANTERIOR SEGMENT DYSGENESIS (ASD) IS A SPECTRUM OF DISORDERS​​ These abnormalities may result from a primary defect in the migration and/or differentiation of ... [10] by S Kaushik · 2022 · Cited by 12 — Anterior segment Dysgeneses (ASD) are a group of non-acquired ocular anomalies associated with glaucoma, characterized by developmental abnormalities of the ...