Introduction

For healthcare professionals managing Epidermal Nevus Syndrome (ENS), understanding its complex and frequent ocular manifestations is paramount to preserving patient vision. This definitive clinical review synthesises the latest evidence to provide a clear, actionable guide for recognising, evaluating, and managing the sight-threatening complications associated with this mosaic genetic disorder.

Epidermal Nevus Syndrome (ENS) affects the eyes in a significant majority of patients, with the most common and critical manifestations being epibulbar complex choristomas (present in 100% of cases in recent series), eyelid colobomas (89% prevalence), strabismus (affecting nearly half of all patients), and optic nerve abnormalities like hypoplasia.^1,3 These are not merely cosmetic issues; they are vision-threatening conditions that can lead to irreversible amblyopia, exposure keratopathy, and permanent visual field loss if not identified and managed through early, specialised ophthalmologic intervention.

While the skin lesions are often the initial diagnostic clue, the ocular involvement in ENS demands an equally rigorous and proactive clinical approach. Read on to explore the full spectrum of eye abnormalities, their embryological origins, and the evidence-based strategies for diagnosis, management, and long-term monitoring that can secure the best possible visual outcomes for your patients.

What is ENS & why eyes are affected

Definition & pathophysiology

Epidermal Nevus Syndrome (ENS) is a rare neurocutaneous disorder characterised by the presence of congenital epidermal nevi – benign overgrowths of skin cells, alongside abnormalities in other organ systems, most commonly the brain, bones, and eyes.³ The condition results from postzygotic somatic mutations occurring after fertilisation, creating a mosaic pattern of affected and unaffected cells throughout the body.⁴ 

Research has identified key genes involved, including FGFR3, PIK3CA, HRAS, and PTCH1.^3,5 These genes are part of critical signalling pathways (like RAS/MAPK and Hedgehog) that regulate cell growth and development. When mutated in a mosaic fashion, they disrupt normal tissue formation, explaining the spectrum of symptoms across different systems.

Embryological basis of ocular involvement

The high frequency of eye problems in ENS is no coincidence. The skin, nervous system, and eyes share a common embryological origin. During the first trimester of pregnancy, neural crest cells migrate and contribute to the formation of numerous ocular structures, including the iris, cornea, sclera, and orbital bones.⁶ The neural crest cells, which contribute to ocular structures including the iris, ciliary body, and parts of the cornea and sclera, are particularly susceptible to the same developmental disruptions that cause the characteristic skin lesions.⁷

The same somatic mutations that cause the skin nevi disrupt the signalling pathways guiding this delicate developmental process. Depending on the timing and location of these disrupted signals, different structural eye defects can occur:

Colobomas: caused by the failure of the embryonic optic fissure to close completely.

Choristomas: benign tumours consisting of normal tissue (like cartilage or bone) growing in the wrong place (e.g. on the eye's surface).

Optic nerve hypoplasia: results from the underdevelopment of retinal nerve fibres.

Anterior segment dysgenesis: malformation of the front part of the eye, leading to a high risk of glaucoma.

Current research on ocular manifestations

Recent clinical studies have provided robust data on how commonly the eyes are affected. A landmark study by Yan et al. of 27 patients with Linear Nevus Sebaceous Syndrome (a primary subtype of ENS) found a consistent and high prevalence of specific lesions.¹

Evidence-based prevalence data

Pathological characteristics

Histologically, the epibulbar choristomas in ENS are typically "complex," meaning they contain multiple tissue types such as cartilage, bone, smooth muscle, and fat.² This distinguishes them from simpler dermoid cysts and often indicates deeper orbital involvement.¹¹

Clinical presentation and diagnosis

Initial assessment

Every patient diagnosed with ENS should undergo a comprehensive ophthalmologic evaluation at the time of diagnosis, regardless of the presence of obvious ocular symptoms.¹² The clinical presentation of ocular involvement in ENS can be subtle, and many sight-threatening conditions may be asymptomatic in their early stages.

Key examination components include:

• Visual acuity testing using age-appropriate methods
• Pupillary examination to check for a relative afferent pupillary defect (a sign of optic nerve disease)
• Ocular motility and alignment evaluation to identify strabismus
• Slit-lamp biomicroscopy of the anterior segment
• Intraocular pressure measurement to screen for glaucoma
• Dilated fundus examination to scrutinise the optic nerve and retina
• Photodocumentation of external findings for monitoring over time

Advanced imaging

Modern imaging modalities have revolutionised the detection and characterisation of ocular abnormalities in ENS:¹³ 

• Optical coherence tomography (OCT): provides high-resolution cross-sections of the retina and optic nerve, crucial for detecting subtle hypoplasia or colobomas
• Ultrasound biomicroscopy: visualises anterior segment structures in detail to assess glaucoma risk
• Magnetic resonance imaging (MRI): essential for evaluating the extent of orbital choristomas and any associated intracranial abnormalities

Management strategies

Surgical interventions

Choristoma management:

• Observation: for small, asymptomatic lesions
• Surgical Excision: indicated for lesions obstructing the visual axis, causing significant astigmatism, leading to mechanical ptosis, or for major cosmetic concerns

Coloboma repair:

• Eyelid colobomas require surgical reconstruction to protect the ocular surface from exposure and dehydration
• The timing and technique depend on the defect's size and the risk of corneal exposure

Strabismus surgery:

• Necessary for significant misalignment affecting binocular vision
• Multiple procedures are often needed due to complex muscle anatomy

Medical management amblyopia therapy: 

This is a critical priority. Treatment includes:

• Correcting any significant refractive error with glasses
• Patching or atropine penalisation of the stronger eye to force the brain to use the weaker eye

Glaucoma management: 

Requires a multi-pronged approach:

• Topical pressure-lowering medications are first-line
• Surgical intervention (trabeculectomy, tube shunts) is often necessary and requires close monitoring

Long-term monitoring:

ENS requires lifelong ophthalmologic follow-up due to risks of progression and new complications.¹⁵ Recommended monitoring intervals:

• First year of life: exams every 3-4 months
• Childhood (1-12 years): exams every 6 months
• Adolescence and Adulthood: annual exams, or more frequently if complications exist

Safety considerations and risk management

Surgical risks

Surgery in ENS patients carries specific considerations:

• Anaesthetic risks may be higher due to potential associated systemic or neurological issues
• Bleeding complications can occur due to unusual vascular anatomy in choristomas
• Recurrence is possible if excision is incomplete

Prognostic factors

Visual outcomes depend on several key factors:

• Age at diagnosis and intervention: earlier is better
• Severity of optic nerve involvement: hypoplasia has a poor visual prognosis
• Unilateral vs. Bilateral disease: bilateral involvement is more likely to cause severe impairment
• Associated CNS abnormalities: can compound visual disability

Future directions and emerging therapies

• Molecular targeted therapy: investigating drugs that inhibit the overactive pathways (RAS/MAPK, Hedgehog)
• Advanced surgical techniques: including endoscopic and image-guided surgery for safer lesion removal
• Improved genetic counseling: as testing improves, it will provide better guidance for families¹⁷

FAQs

Is every child with ENS guaranteed to develop eye problems? 

Not every child will develop eye problems, but the risk is substantial, with recent studies showing ocular involvement in up to 89% of patients. All children with ENS should undergo a comprehensive eye examination regardless of symptoms.¹

When should the first eye exam occur? 

The first comprehensive ophthalmologic examination should occur at the time of ENS diagnosis, ideally during infancy. Early detection is crucial for preventing irreversible visual complications.¹²

Can eye problems in ENS be completely cured? 

Some complications, like cataracts and certain types of strabismus, can be successfully treated with excellent visual outcomes. However, conditions like optic nerve hypoplasia result in permanent visual impairment. Early intervention maximises the potential for visual rehabilitation.¹⁴

How often do children with ENS need eye exams?

Monitoring frequency depends on age and severity of involvement. Generally, infants require examination every 3-4 months, children every 6 months, and adults annually, with more frequent visits if complications develop.¹⁵

Does genetic testing change treatment approaches? 

Currently, genetic testing primarily aids in diagnosis confirmation and genetic counselling rather than changing immediate treatment. However, as molecular targeted therapies are developed, genetic information may guide future treatment decisions.^16,18

What should parents watch for between eye appointments? 

Parents should monitor for signs, including eye misalignment, excessive tearing, light sensitivity, white pupil reflex, or any changes in the appearance of existing eye lesions. Any concerning changes warrant immediate ophthalmologic evaluation.

Summary

Epidermal Nevus Syndrome (ENS) is a complex disorder with ocular involvement in up to 89% of patients. The hallmark lesions, epibulbar choristomas, eyelid colobomas, strabismus, and optic nerve anomalies, are more than skin deep; they are significant threats to vision that demand a proactive, multidisciplinary approach. The cornerstone of management is early and comprehensive ophthalmologic evaluation followed by aggressive treatment of amblyopia, timely surgical intervention when indicated, and lifelong monitoring. While challenges remain, current evidence-based strategies can significantly improve functional visual outcomes, and ongoing research into the genetic basis of ENS promises more targeted therapies in the future.