Congenital hereditary corneal dystrophy (CHED) is a form of
corneal endothelial dystrophy that presents at birth.
CHED was previously subclassified into two subtypes: CHED1 and CHED2. However in 2015, the International Classification of Corneal Dystrophies (IC3D) renamed the condition "CHED1" to become
posterior polymorphous corneal dystrophy
Posterior polymorphous corneal dystrophy (PPCD; sometimes also ''Schlichting dystrophy'') is a type of corneal dystrophy, characterised by changes in Descemet's membrane and endothelial layer. Symptoms mainly consist of decreased vision due to ...
, and renamed the condition "CHED2" to become, simply, CHED.
Consequently, the scope of this article is restricted to the condition currently referred to as ''CHED''
Signs and symptoms
CHED presents congenitally, but has a stationary course. The cornea exhibits a variable degree of clouding: from a diffuse haze, to a "ground glass" appearance, with occasional focal gray spots. The cornea thickens to between two and three times is normal thickness. Rarely, sub-epithelial
band keratopathy
Band keratopathy is a corneal disease derived from the appearance of calcium on the central cornea. This is an example of metastatic calcification, which by definition, occurs in the presence of hypercalcemia.
Signs and symptoms
Signs and sympto ...
and elevated
intraocular pressure
Intraocular pressure (IOP) is the fluid pressure inside the eye. Tonometry is the method eye care professionals use to determine this. IOP is an important aspect in the evaluation of patients at risk of glaucoma. Most tonometers are calibrated t ...
occur. Patients have blurred vision and nystagmus, however it is rare for the condition to be associated with either
epiphora or
photophobia
Photophobia is a medical symptom of abnormal intolerance to visual perception of light. As a medical symptom photophobia is not a morbid fear or phobia, but an experience of discomfort or pain to the eyes due to light exposure or by presence of ...
with this.
Genetics
CHED exhibits autosomal recessive inheritance, with 80% of cases linked to mutations in
SLC4A11
Sodium bicarbonate transporter-like protein 11 is a protein that in humans is encoded by the ''SLC4A11'' gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." m ...
gene. The SLC4A11 gene encodes solute carrier family 4, sodium borate transporter, member 11.
Pathology
Histologically, the
Descemet's membrane
Descemet's membrane ( or the Descemet membrane) is the basement membrane that lies between the corneal proper substance, also called stroma, and the endothelial layer of the cornea. It is composed of different kinds of collagen (Type IV and VIII) ...
in CHED becomes diffusely thickened and laminated. Multiple layers of
basement membrane-like material appear to form on the posterior part of
Descemet's membrane
Descemet's membrane ( or the Descemet membrane) is the basement membrane that lies between the corneal proper substance, also called stroma, and the endothelial layer of the cornea. It is composed of different kinds of collagen (Type IV and VIII) ...
. The endothelial cells are sparse - they become atrophic and degenerated, with many vacuoles. The
corneal stroma
The stroma of the cornea (or substantia propria) is a fibrous, tough, unyielding, perfectly transparent and the thickest layer of the cornea of the eye. It is between Bowman's membrane anteriorly, and Descemet's membrane posteriorly.
At its cent ...
becomes severely disorganised; the lamellar arrangement of the fibrils becomes disrupted.
Diagnosis
Management
Management of CHED primarily involves
corneal transplantation. The age that corneal transplantation is required is variable, however, it is usually necessary fairly early in life.
See also
*
Posterior polymorphous corneal dystrophy
Posterior polymorphous corneal dystrophy (PPCD; sometimes also ''Schlichting dystrophy'') is a type of corneal dystrophy, characterised by changes in Descemet's membrane and endothelial layer. Symptoms mainly consist of decreased vision due to ...
(for the condition previously referred to as ''CHED1'')
*
Corneal dystrophy
Corneal dystrophy is a group of rare hereditary disorders characterised by bilateral abnormal deposition of substances in the transparent front part of the eye called the cornea.
Signs and symptoms
Corneal dystrophy may not significantly affect v ...
References
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Disorders of sclera and cornea