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Peters anomaly
This condition is present from birth and can affect one or both eyes, often leading to significant vision impairment. It is typically caused by genetic changes that disrupt normal eye development.
Overview
Peters anomaly is a rare congenital disorder that primarily affects the front part of the eye, known as the anterior segment. It is characterised by a cloudy cornea, which is the clear outer layer at the front of the eye [PMID:32252187]. This clouding can range from mild to severe and is often associated with other structural abnormalities within the eye, such as adhesion of the iris (the coloured part of the eye) to the posterior surface of the cornea. Peters anomaly can occur in one eye (unilateral) or both eyes (bilateral), with bilateral involvement generally leading to more significant vision challenges.
The condition is present from birth, meaning it is congenital. The severity can vary greatly among individuals, even within the same family. Early diagnosis and appropriate management are important for optimising visual outcomes.
Symptoms & clinical features
The primary symptom of Peters anomaly is a noticeable clouding of the cornea at birth or shortly after. This clouding can make the pupil appear white or grey instead of black. Other visible signs may include an abnormally small or underdeveloped iris, or the iris being stuck to the cloudy cornea [PMID:24177420].
Beyond these visible signs, individuals with Peters anomaly may experience other ocular complications. These can include glaucoma, a condition characterised by increased pressure within the eye that can damage the optic nerve, and cataracts, which are clouding of the eye's lens. Nystagmus, an involuntary rhythmic movement of the eyes, may also be present, particularly if vision is significantly impaired. In some cases, the eyes may be smaller than average (microphthalmia).
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Affected organs
Peters anomaly predominantly affects the eyes. Specifically, it impacts the cornea, iris, and lens, which are all components of the eye's anterior segment. The primary defect involves the development of the cornea, leading to its characteristic cloudiness. The iris and lens may also show developmental abnormalities.
While Peters anomaly is primarily an eye condition, in some instances, it can be part of a broader syndrome affecting other body systems. This is more common when the condition is associated with specific genetic changes. However, the isolated form of Peters anomaly typically only involves the eyes.
Risks & severity
The severity of Peters anomaly is highly variable. Some individuals may have mild corneal clouding with relatively good vision, while others may experience profound vision impairment or even blindness due to severe corneal opacification, glaucoma, or retinal detachment. The condition can significantly impact an individual's quality of life, particularly if both eyes are severely affected.
Complications such as glaucoma and cataracts can worsen over time, requiring ongoing monitoring and treatment. The risk of developing these secondary conditions is a significant concern for individuals with Peters anomaly. The exact prevalence of Peters anomaly is not well established, but it is considered a rare condition.
Genetic causes
Peters anomaly is often caused by genetic changes (also known as variants or mutations) in certain genes that play a crucial role in eye development. The most commonly associated genes include FOXE3, PAX6, and PITX2 [PMID:29669562]. These genes provide instructions for making proteins that are essential for the proper formation of the eye's anterior structures during foetal development.
For example, the PAX6 gene is known to be a master control gene for eye development, and variants in PAX6 can lead to a range of ocular anomalies, including Peters anomaly. Similarly, FOXE3 and PITX2 are involved in regulatory processes that guide the development of the cornea and other anterior segment structures. When these genes do not function correctly due to a genetic change, the intricate process of eye formation can be disrupted, leading to the features observed in Peters anomaly.
- FOXE3 forkhead box E3
- PAX6 paired box 6
- PITX2 paired like homeodomain 2
Inheritance pattern
Peters anomaly is typically inherited in an autosomal dominant pattern. This means that only one altered copy of a particular gene in each cell is sufficient to cause the condition. In many cases, the genetic change occurs spontaneously in the affected individual and is not inherited from either parent (a 'de novo' variant). However, if an affected parent carries the genetic change, there is a 50% chance for each child to inherit the variant and potentially develop Peters anomaly.
even within families where the genetic change is inherited, the severity of the condition can vary widely among affected individuals. This is known as variable expressivity. Genetic counselling is recommended for families with a diagnosis of Peters anomaly to understand the specific inheritance pattern and recurrence risks.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
Diagnosis & testing
Diagnosis of Peters anomaly is usually made at birth based on a clinical eye examination that reveals corneal clouding and other anterior segment abnormalities. Specialised ophthalmological examinations, such as anterior segment optical coherence tomography (OCT) or ultrasound biomicroscopy (UBM), may be used to further assess the ocular structures and confirm the diagnosis.
Genetic testing is increasingly important for confirming the diagnosis and identifying the specific genetic cause, especially when considering family planning or if the condition is part of a syndromic presentation. In the UK, genetic testing for inherited eye conditions, including those that cause Peters anomaly, may be accessed via the NHS Genomic Medicine Service (GMS). Referral to clinical genetics services is typically made by an ophthalmologist, paediatrician, or general practitioner to consider relevant R-codes for genomic testing.
Management & lifestyle
Management of Peters anomaly focuses on preserving and improving vision as much as possible, as well as managing associated complications. This often involves a multidisciplinary team including ophthalmologists, geneticists, and low vision specialists. Treatment approaches can vary based on the severity of corneal clouding and the presence of other ocular issues like glaucoma or cataracts.
Medical treatments may include eye drops to manage glaucoma. Surgical interventions, such as corneal transplantation (keratoplasty), may be considered for severe corneal clouding to improve vision, though outcomes can be variable. Cataract surgery may also be performed if cataracts are present. Regular follow-up appointments with an ophthalmologist are crucial to monitor eye health and address any emerging complications. Genetic counselling is an integral part of the management pathway, offering information and support to individuals and families regarding the genetic aspects of the condition and potential implications for future pregnancies.
UK care pathway
In the UK, individuals suspected of having Peters anomaly will typically be referred to an ophthalmologist, often within a paediatric ophthalmology service. If a genetic cause is suspected, the patient may be referred to a clinical genetics service for assessment. The NHS Genomic Medicine Service provides access to genomic testing through specific R-codes, such as those related to inherited eye disorders (e.g., R109 for congenital eye anomalies). A genetic counsellor will provide information and support to patients and their families regarding genetic testing, inheritance patterns, and potential implications.
Frequently asked questions
What is the long-term outlook for someone with Peters anomaly?
The long-term outlook varies greatly depending on the severity of the condition and how well any complications, such as glaucoma or cataracts, are managed. Regular follow-up with eye specialists is essential for monitoring and addressing issues that may arise to help maintain vision as much as possible.
Can Peters anomaly be cured?
Currently, there is no cure for the underlying genetic cause of Peters anomaly. However, treatments such as corneal transplantation and management of secondary complications like glaucoma and cataracts can help to improve vision and preserve eye health.
Is Peters anomaly always inherited from parents?
Peters anomaly is often caused by a new genetic change (de novo variant) that occurs spontaneously in the affected individual, meaning it is not inherited from either parent. However, in some cases, it can be inherited in an autosomal dominant pattern from an affected parent. Genetic counselling can help clarify the inheritance pattern for specific families.
How does Peters anomaly affect a child's development?
Significant vision impairment from Peters anomaly can affect a child's development, particularly in areas like motor skills and learning. Early intervention, including low vision support, educational assistance, and therapy, is often recommended to help children reach their full potential.
What support is available for families affected by Peters anomaly?
Families can access support through clinical genetics services, genetic counsellors, and patient support groups for rare eye conditions. Low vision services and educational support are also available to help individuals manage the visual impairment associated with Peters anomaly.
References
- Moshirfar M, Hastings J, Ronquillo Y. Megalocornea. 2023. PMID: 32119261