Corneal opacity

Types

Nebular corneal opacity

Macular corneal opacity

Leucomatous corneal opacity (leucoma simplex)

• Adherent leucoma: It results when healing occurs after perforation of cornea with incarceration of iris. The iris is adherent to the back of a leucomatous cornea. One of the major complication of adherent leucoma is Secondary glaucoma
• Corneoiridic scar: If iris tissue is incarcerated and incorporated within the scar tissue, as occurs in healing of a large sloughed corneal ulcer, it is called a corneoiridic scar.
• Corneal facet: Sometimes the corneal surface is depressed at the site of healing ; such a scar is called facet.
• Kerectasia: In this condition, corneal curvature is increased at the site of opacity.

  Presentation

• Loss of vision or Blindness
• Blurred vision
• Glare

  Complications

Secondary changes in corneal opacity

Causes

• Congenital opacities may occur as developmental anomalies or following birth trauma. Causes of congenital corneal opacities include sclerocornea, trauma, ulcer, mucopolysaccharidosis, Peter’s anomaly, congenital hereditary endothelial dystrophy.
• Ocular trauma
• Corneal ulceration
• Xerophthalmia, caused by Vitamin A deficiency
• Trachoma
• Onchocerciasis
• Mucous membrane pemphigoid: Ocular form of mucous membrane pemphigoid may cause corneal opacity and loss of vision.

  Genetics

Congenital Corneal Opacities

• Congenital hereditary endothelial dystrophy : There are 2 forms of congenital hereditary endothelial dystrophy. Commonest is an autosomal recessive form, which is present at birth, but nonprogressive. Nystagmus is seen in association with this form. Another is an autosomal dominant form that occurs within the first few years of life. This form is progressive, but nystagmus is not seen. Deafness and CHED are seen in Harboyan syndrome. The histologic findings are very similar to those seen in pseudophakic/ aphakic bullous keratopathy. The appearance of the cornea is similar to that in congenital glaucoma but without increased corneal diameter and elevated intraocular pressure.
• Posterior Polymorphous Corneal Dystrophy : PPCD, also known as Schlichting dystrophy, is an autosomal dominant disorder of the corneal endothelium and Descemet’s membrane. It is usually present in the second or third decade of life. It has the same entity as the first form of CHED. Most cases of PPMD are asymptomatic, and these cases generally do not require treatment. PPMD patients with bilateral, corneal opacities that can affect vision, descemet’s membrane endothelial keratoplasty or penetrating keratoplasty are the treatments of choice to improve vision and to avoid amblyopia.
• Congenital hereditary stromal dystrophy : CHSD is also known as Congenital stromal corneal dystrophy or Congenital stromal dystrophy of the cornea. It is a rare autosomal dominant disease caused by mutations in the DCN gene. In this bilateral Snowflake, whitish opacities appear throughout the cornea. The stromal lamellae are abnormal and may be separated by amorphous deposits. Moderate to severe vision loss may occur due to corneal opacity. In case of severe vision loss,treament of choice is penetrating keratoplasty.
• Peters anomaly: Peters anomaly, also known as iridocorneal adhesions or keratolenticular adhesions, is a posterior corneal defect with an overlying stromal opacity, often accompanied by adherent iris strands. The size and density of the opacity can range from a mild to dense central leukoma.
• Congenital Anterior Staphyloma: Congenital anterior staphyloma is a rare form of anterior segment dysgenesis that shares similarities with Peters anomaly. It is characterized by an ectatic protrusion of a central opacified cornea lined by uveal tissue. The protrusion extends beyond the plane of the eyelid margins and it can be unilateral or bilateral.
• Lattice Corneal Dystrophy: Lattice corneal dystrophy is an autosomal-dominant characterized by amyloid deposition in the corneal stroma. Due to deposits, lattice-like corneal opacities may occur in stroma. Three types of dystrophies are there, type 1, type 2 and type 3. Type 1 is also known as Biber-Haab-Dimmer corneal dystrophy, TGFBI type Lattice Dystrophy, or Classic Lattice Dystrophy. LCD type II is not included in corneal dystrophies.
• Granular Corneal Dystrophy: Two types, Type 1 and Type 2 are there. Both have autosomal dominant inheritance. In Type 1, Discrete crumb-like opacities are seen in the central anterior stroma. Visual symptoms such as glare and photophobia may occur early in life. In Type 2, deposits begin to appear in early childhood or adolescence as tiny whitish dots in the anterior stroma. Larger stellate, ring, or snowflake opacities may occur in later stages. Decrease in vision starts earlier in type2 than type1.
• Sclerocornea: Sclerocornea is a congenital disorder in which the cornea is opaque and resembles the sclera, making the limbus indistinct. The central cornea is clearer than the periphery.
• Cystinosis: Cystinosis is a rare autosomal recessive metabolic disease characterized by elevated levels of cystine within the cell. Early deposition of cystine crystals in the cornea cause tinsel-like corneal opacities.
• Ichthyosis: X-linked ichthyosis is a genetic skin disorder caused by the hereditary deficiency of the steroid sulfatase enzyme. Ocular manifestations of XLI include superficial or deep corneal opacities.
• Trisomy 8 mosaicism : It is a rare chromosome disorder caused by the presence of an extra chromosome 8 in some cells of the body. Dense corneal opacities may occur in trisomy 8 mosaicism.
• Farber's disease: Nodular corneal opacity may be seen in association with this rare autosomal recessive disease.

  Acquired Pediatric Corneal Opacities

• Traumatic: Traumatic breaks in Descemet membrane may cause corneal opacity. Injuries to Descemet membrane occur during delivery. Opacity is commonly unilateral.
• Congenital or infantile glaucoma: In Congenital glaucoma, the cornea becomes edematous, cloudy, and enlarged. Treatment should be done to reduce Intraocular pressure.
• Congenital corneal ulcers: Unilateral corneal opacity may occur in association with conjunctival injection and other signs of inflammation.
• Mucopolysaccharidoses: The mucopolysaccharidoses are a group of inherited metabolic diseases caused by the absence or malfunctioning of certain enzymes the body needs to break down molecules called glycosaminoglycans. It is an autosomal recessive disorder. Sometimes, Corneal haze may be present in early life. Treatment options for significant opacities include penetrating keratoplasty and DALK.

  Treatment

Keratoplasty

• Penetrating keratoplasty: It is the traditional full thickness corneal transplant procedure, in which trephine is used to cut opaque cornea, a similar-sized portion of the donor cornea is removed with a second trephine. The removed part of donor cornea is known as corneal button. The donor tissue is then sutured to the patient eye. Dense corneal opacity which occupies all the corneal layers may be treated with penetrating keratoplasty.
• Superficial lamellar keratoplasty: Superficial lamellar keratoplasty is used to treat superficial corneal opacities, which occupies superficial one third part of stroma. In this technique, the opaque part of the cornea is removed and replaced with donor tissue, leaving healthy part of the cornea including deeper parts of stroma and endothelium.
• Deep anterior lamellar keratoplasty: DALK may be considered in deep opacities with normal endothelium and descemet's membrane. In this procedure, the anterior layers of cornea are removed and replaced with donor tissue, leaving the endothelial layer and the descemet's membrane in place.

  Optical iridectomy

Phototherapeutic keratectomy (PTK)

Tattooing of scar

Techniques

• Staining method: In this technique, tattoo ink is directly applied to anterior surface of cornea. Benefits of this procedure include fast procedure with uniform dye application. Risk of fading is a main drawback.
• Femtosecond laser-assisted corneal tattooing: Femtosecond laser-assisted corneal tattooing is a new corneal tattooing technique, with many benefits.

  Keratoprosthesis

Epidemiology

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