Cornea plana 2

Cornea plana 2 (CNA2) is a congenital disorder that causes the cornea to flatten and the angle between the sclera and cornea to shrink.^[1] This could result in the early development of arcus lipoides, hazy corneal limbus, and hyperopia.^[2] There is evidence that cornea plana 2 is caused by mutations in KERA gene encoding keratocan.^[3] Cornea plana 2 is an autosomal recessive disorder.^[4]

Cornea plana 2
Other names	Autosomal recessive Cornea plana, CNA2.
Cornea plana 2 is inherited in an autosomal recessive manner.
Specialty	Medical genetics

Signs and symptoms

Cornea plana commonly presents as a flat cornea, early-onset arcus lipoides, low anterior chamber depth, and an indistinct border between the sclera and cornea due to a decreased angle between the two.^[2] Although a small corneal diameter is anticipated, measuring it can be challenging because the scleral tissue overlaps the cornea by a few millimeters. In the patients who have cornea plana, the anterior chamber depth has been found to vary from 0.8 to 2.1 mm.^[5]

Moreover, high hyperopia, strabismus, microcornea, posterior embryotoxon, iridocorneal adhesions, iris lumps, iris wasting, and pupillary abnormalities can all be present.^[6] Instead of hyperopia, myopia has been identified in a few cases.^[7] As many as 90 percent of cases have a bilateral presentation, which is linked to sclerocornea.^[1] Finally, congenital ptosis has also been reported, and the absence of corneal protrusion is most likely the cause.^[5]

Cause

Diagnosis

Clinical presentation, keratometry,^[7] pachymetry, and endothelial imaging are used to make the diagnosis.^[8]

Since the decreased refraction in the autosomal recessive form is more severe than in the autosomal dominant form, corneal refraction measurements can be used to differentiate between CNA1 and CNA2.^[5]

Histology is distinguished by acanthosis, keratinization of the corneal epithelium, Bowman's membrane defects, and stromal vascularization and scar formation.^[4]

Management

See also

• Cornea plana 1
• Keratoglobus