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Sclerocornea
This condition can be inherited in an autosomal dominant manner
Specialty	Ophthalmology

Sclerocornea is a congenital anomaly of the eye in which the cornea blends with sclera, having no clear-cut boundary. The extent of the resulting opacity varies from peripheral to total (sclerocornea totalis). The severe form is thought to be inherited in an autosomal recessive manner, but there may be another, milder form that is expressed in a dominant fashion. In some cases the patients also have abnormalities beyond the eye (systemic), such as limb deformities and craniofacial and genitourinary defects.

According to one tissue analysis performed after corneal transplantation, the sulfation pattern of keratan sulfate proteoglycans in the affected area is typical for corneal rather than scleral tissue.

Sclerocornea may be concurrent with cornea plana.

Anatomy of the human eye

Signs and Symptoms

Sclerocornea causes parts or all of the cornea to become cloudy. This cloudiness can be partial or complete. The more of the cornea that is affected, the worse a persons vision will be.

The main area affected is the cornea, but the issue can also spread to nearby parts of the eye, like the limbus and front eye structure.

Since Sclerocornea is present from birth and does not develop later in life there are no short-term symptoms or signs. The condition usually affects both eyes and it does not worsen overtime, the symptoms and severity are present from birth and generally remain stable.

As a result and depending on the variety, the patient may have poor vision and in some cases problems with eye movement, such as nystagmus or strabismus. Over time, people may develop severe farsightedness, glaucoma, and other eye issues.

Cause

The exact cause of Sclerocornea is not fully understood, but it is believed to involve genetic and developmental factors. Even though there are some understanding of the genetic and devlopmental factors, the exact cause is unclear. Ongoing reseach is needed to identify the specific genes and factors that contribute to the disorder.

Genetic Factors:

Sclerocornea can be inherited as a genetic, as autosomal dominant or recessive trait, with the latter form often being more severe. Certain genes have been linked to this condition, and some cases are associated with the genetic disorders like Digeorge syndrome, making genetic counseling important.

Associated Conditions:

Sclerocornea is sometimes found alongside other health issues, such as PHACES syndrome, Dandy-walker malformation, and Hurler syndrome.

Developmental Causes:

The condition is thought to occur because neural crest cells dont move or develop correctly between the 7th and 10th week of pregnancy. These cells are important for forming many parts of the eye structures, and abnormalities in their formation can lead to issues.

Pathophysiology or Mechanism

The main problem affected in sclerocornea occurs in the cornea, which doesn’t develop correctly and starts to look more like the white part of the eye (the sclera). The condition is thought to occur because certain cells, called neural crest cells, don’t move or develop as they should during the 7th and 10th weeks of gestation. When these cells do not migrate correctly, the corena does not develop into a clear structure. Instead, it becomes opaque and the boundary of the cornea is found to be poorly defined.

Under a Microscope, the cornea’s layers are disorganized, have extra blood vessels, and the cornea’s structure is altered. Even though the cornea becomes more like the sclera, it still has some unique markers that show it retains some of its original characteristics.

Scientists don’t fully understand how all the changes happen, but they think it could be due to problems with certain proteins and the development of neural crest cells.

Diagnosis

Diagnosis typically involves an ophthalmologist and might require a geneticist for counseling. Diagnostic tools that are used are clinical examination under anesthesia, handheld slit-lan evaluation, anterior segment optical coherence tomography (ASOCT), and genetic testing.

Misdiagnosis can occur due to overlapping features with other congenital corneal opacities. Diagnostic delays. may happen if systemic associations are not immediately recognized.

Treatment or Management

Primary treatment for Sclerocornea is Penetrating keratoplasty (PK), although success rates are variable due to risks like graft rejection and glaucoma. Non surgical options include refractive correction or optical iridetomy, this can be considered for milder cases.

Currently there are advances in surgical techniques and the isue of immunosuppressants post surgery are being explored. Genetic counseling and comprehensive monitoring of systemic health are recommended.

Prognosis

Visual outcomes depend on the timing and extend of intervention. Early childhood cases often have poorer prognosis. Some patient require multiple surgeries and the risk of vision loss remains high if glaucoma or significant vascularization is present. This vision impairment can impact developmental milestones in children. However, longer-term data on treat efficacy, especially regarding quality of life, is limited.

Epidemiology

Sclerocornea is a rare disorder, with no clear gender bias. It occurs across different ethnicities, although comprehensive epidemiological data is lacking. This conditin also often accompanies other congential disorders, affectings its distribution and manifestation.

Research Directions

Research over the past decade has focused on genetic underpinnings and improving surgical techniques. Case studies highlight the variability in outcomes based on associated ocular and systemic conditions. There are currently investigations into the use of topical and systemic immunosuppressants. The challenges is that the rarity of the disease complicates large-scale studies, though collaborative research is expanding knowledge.

External links

• Congenital Clouding of the Cornea - eMedicine; by Noah S Scheinfeld, MD, JD, FAAD and Benjamin D Freilich, MD, FACS

Category:Eye diseases