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Onset occurs in the first decade, usually between ages 5 and 9. The disorder is progressive. Minute, gray, punctate opacities develop. Corneal sensitivity is usually reduced. Painful attacks with photophobia, foreign body sensations, and recurrent erosions occur in most patients. Macular corneal dystrophy is very common in Iceland and accounts for almost one-third of all corneal grafts performed there.
Patients may complain of severe problems with dry eyes, or with visual obscurations. It can also be asymptomatic, and only discovered because of subtle lines and marks seen during an eye exam.
EBMD is a bilateral anterior corneal dystrophy characterized by grayish epithelial fingerprint lines, geographic map-like lines, and dots (or microcysts) on slit-lamp examination. Findings are variable and can change with time. While the disorder is usually asymptomatic, up to 10% of patients may have recurrent corneal erosions, usually beginning after age 30; conversely, 50% of patients presenting with idiopathic recurrent erosions have evidence of this dystrophy.
Thiel–Behnke dystrophy, or Corneal dystrophy of Bowman layer, type II, is a rare form of corneal dystrophy affecting the layer that supports corneal epithelium.
The dystrophy was first described in 1967 and initially suspected to denote the same entity as the earlier-described Reis-Bucklers dystrophy, but following a study in 1995 by Kuchle et al. the two look-alike dystrophies were deemed separate disorders.
In the recessive form corneal clouding is observed at birth or within the neonatal period, nystagmus is often present, but no photophobia or epiphora is seen. In the autosomal dominant type corneal opacification is usually seen in the first or second year of life and progresses slowly, and nystagmus is infrequently seen.
Congenital hereditary corneal dystrophy (CHED) is a form of corneal dystrophy which presents at birth.
Patients with Reis-Bücklers dystrophy develop a reticular pattern of cloudiness in the cornea. This cloudiness, or opacity, usually appears in both eyes (bilaterally) in the upper cornea by 4 or 5 years of age. The opacity elevates the corneal epithelium, eventually leading to corneal erosions that prompt attacks of ocular hyperemia, pain, and photophobia. These recurrent painful corneal epithelial erosions often begin as early as 1 year of age.
With time, the corneal changes progress into opacities in Bowman's membrane, which gradually becomes more irregular and more dense. Significant vision loss may occur. However, vascularization of the cornea is not present.
Lisch epithelial corneal dystrophy (LECD), also known as band-shaped and whorled microcystic dystrophy of the corneal epithelium, is a rare form of corneal dystrophy first described in 1992 by Lisch et al. In one study it was linked to chromosomal region Xp22.3, with as yet unknown candidate genes.
The main features of this disease are bilateral or unilateral gray band-shaped and feathery opacities. They sometimes take on a form of a whirlpool, repeating the known pattern of corneal epithelium renewal. Abrasion of the epithelium in 3 patients brought only temporary relief, with abnormal epithelium regrowth in several months.
Epithelial cells in the zones of opacity were shown to have diffuse cytoplasmic vacuoles with as yet unestablished content.
To clarify whether Thiel–Behnke corneal dystrophy is a separate entity from Reis-Bucklers corneal dystrophy, Kuchle et al. (1995) examined 28 corneal specimens with a clinically suspected diagnosis of corneal dystrophy of the Bowman layer by light and electron microscopy and reviewed the literature and concluded that 2 distinct autosomal dominant corneal dystrophy of Bowman layer (CBD) exist and proposed the designation CDB type I (geographic or 'true' Reis-Bucklers dystrophy) and CDB type II (honeycomb-shaped or Thiel–Behnke dystrophy). Visual loss is significantly greater in CDB I, and recurrences after corneal transplantation seem to be earlier and more extensive in CDB I.
Schnyder crystalline corneal dystrophy (SCD) is a rare form of corneal dystrophy. It is caused by heterozygous mutations in UBIAD1 gene. Cells in the cornea accumulate cholesterol and phosopholipid deposits leading to the opacity, in severe cases requiring corneal transplants. Abnormal cholesterol metabolism has been noted in other cell types of affected patients (skin fibroblasts) suggesting that this may be a systemic disorder with clinical manifestations limited to the cornea.
Hair growth on the head is noticeably less full than normal, and the hairs are very weak; the rest of the body shows normal hair.
The macular degeneration comes on slowly with deterioration of central vision, leading to a loss of reading ability. Those affected may otherwise develop in a completely healthy manner; life expectancy is normal.
Congenital stromal corneal dystrophy (CSCD), also called Witschel dystrophy, is an extremely rare, autosomal dominant form of corneal dystrophy. Only 4 families have been reported to have the disease by 2009. The main features of the disease are numerous opaque flaky or feathery areas of clouding in the stroma that multiply with age and eventually preclude visibility of the endothelium. Strabismus or primary open angle glaucoma was noted in some of the patients. Thickness of the cornea stays the same, Descemet's membrane and endothelium are relatively unaffected, but the fibrills of collagen that constitute stromal lamellae are reduced in diameter and lamellae themselves are packed significantly more tightly.
Posterior amorphous corneal dystrophy (PACD) is a rare form of corneal dystrophy. It is not yet linked to any chromosomal locus. The first report describing this dystrophy dates back to 1977.
Subepithelial mucinous corneal dystrophy (SMCD) is a rare form of corneal dystrophy. It was first described in 1993 by Feder et al. Anterior to Bowman layer, deposits of glycosaminoglycan were detected and identified as chondroitin-4-sulfate and dermatan sulfate.
The main pathological features in this dystrophy are mulberry-shaped gelatinous masses beneath the corneal epithelium. Patients suffer from photophobia, foreign body sensation in the cornea. The loss of vision is severe. The amyloid nodules have been found to contain lactoferrin, but the gene encoding lactoferrin is unaffected.
This form of corneal amyloidosis appears to be more frequent in Japan.
Macular corneal dystrophy, also known as Fehr corneal dystrophy named for German ophthalmologist Oskar Fehr (1871-1959), is a rare pathological condition affecting the stroma of cornea. The first signs are usually noticed in the first decade of life, and progress afterwards, with opacities developing in the cornea and attacks of pain. The condition was first described by Arthur Groenouw in 1890.
Reis-Bücklers corneal dystrophy, also known as corneal dystrophy of Bowman layer, type I, is a rare, corneal dystrophy of unknown cause, in which the Bowman's layer of the cornea undergoes disintegration. The disorder is inherited in an autosomal dominant fashion, and is associated with mutations in the gene TGFB1.
Reis-Bücklers dystrophy causes a cloudiness in the corneas of both eyes, which may occur as early as 1 year of age, but usually develops by 4 to 5 years of age. It is usually evident within the first decade of life. This cloudiness, or opacity, causes the corneal epithelium to become elevated, which leads to corneal opacities. The corneal erosions may prompt attacks of redness and swelling in the eye (ocular hyperemia), eye pain, and photophobia. Significant vision loss may occur.
Reis-Bücklers dystrophy is diagnosed by clinical history physical examination of the eye. Labs and imaging studies are not necessary. Treatment may include a complete or partial corneal transplant, or photorefractive keratectomy.
Fleck corneal dystrophy, also known as "Francois-Neetens speckled corneal dystrophy", is a rare form of corneal dystrophy. It is caused by mutations in PIKFYVE gene. Small opacities, some of which resemble "flecks", are scattered in the stroma of the patients. Other opacities look more like snowflakes or clouds. The disease is non-progressive and in most cases asymptomatic, with mild photophobia reported by some patients. In a single case report, a corneal transplantation was performed for concurrent keratoconus, and at 10 years follow-up there was still no evidence of the inclusions in the stroma.
Epithelial basement membrane dystrophy (EBMD), also known as map-dot-fingerprint dystrophy and Cogans's microcystic dystrophy, is a disorder of the eye that can cause pain and dryness.
It is sometimes included in the group of corneal dystrophies. It diverges from the formal definition of corneal dystrophy in being in most cases non-familial. It also has a fluctuating course, while for a typical corneal dystrophy the course is progressive. When it is considered part of this group, it is the most common type of corneal dystrophy.
X-linked endothelial corneal dystrophy (XECD) is a rare form of corneal dystrophy described first in 2006, based on a 4-generation family of 60 members with 9 affected males and 35 trait carriers, which led to mapping the XECD locus to Xq25. It manifests as severe corneal opacification or clouding, sometimes congenital, in the form of a ground glass, milky corneal tissue, and moon crater-like changes of corneal endothelium. Trait carriers manifest only endothelial alterations resembling moon craters.
As of December 2014, the molecular basis for this disease remained unknown, although 181 genes were known to be within the XECD locus, of which 68 were known to be protein-coding.
Meesmann corneal dystrophy, also "Stocker-Holt dystrophy", is a type of corneal dystrophy and a keratin disease.
It is named for German ophthalmologist Alois Meesmann (1888-1969).
It is sometimes called "Meesmann-Wilke syndrome", after the joint contribution of Meesmann and Wilke.
The age of onset is in a child's infancy. Bilateral corneal opacification started in the second year of life and led to severe visual impairment. However, cornea surgery and replacement resulted in better vision.
Symptoms include a combination of spinocerebellar degeneration and corneal dystrophy. Mental retardation and slowly progressive cerebellar abnormalities were also diagnosed in patients. Other symptoms include corneal edema, thickening of Descemet membrane, and degenerative pannus. Abnormalities were found in muscle and sural nerves.
This slowly progressive disorder is characterized by small cysts in the epithelium of the cornea. Patients with Meesmann corneal dystrophy are intolerant of contact lenses, as these devices directly traumatize the corneal epithelium.
Corneal dystrophies were commonly subdivided depending on its specific location within the cornea into "anterior", "stromal", or "posterior" according to the layer of the cornea affected by the dystrophy.
In 2015 the ICD3 classification was published. and has classified disease into four groups as follows:
Epithelial and subepithelial dystrophies
- Epithelial basement membrane dystrophy
- Epithelial recurrent erosion dystrophies (EREDs)—Franceschetti corneal dystrophy, Dystrophia Smolandiensis, and Dystrophia Helsinglandica
- Subepithelial mucinous corneal dystrophy
- Meesmann corneal dystrophy
- Lisch epithelial corneal dystrophy
- Gelatinous drop-like corneal dystrophy
Bowman Layer dystrophies
- Reis–Bücklers corneal dystrophy
- Thiel–Behnke corneal dystrophy
- Stromal dystrophies-
- TGFB1 corneal dystrophies
- Lattice corneal dystrophy, type 1 variants (III, IIIA, I/IIIA, IV) of lattice corneal dystrophy
- Granular corneal dystrophy, type 1
- Granular corneal dystrophy, type 2
Stromal dystrophies
- Macular corneal dystrophy
- Schnyder crystalline corneal dystrophy
- Congenital stromal corneal dystrophy
- Fleck corneal dystrophy
- Posterior amorphous corneal dystrophy
- Central cloudy dystrophy of François
- Pre-Descemet corneal dystrophy
Endothelial dystrophies
- Fuchs' dystrophy
- Posterior polymorphous corneal dystrophy
- Congenital hereditary endothelial dystrophy
- X-linked endothelial corneal dystrophy
The following (now historic) classification was by Klintworth:
Superficial dystrophies:
- Epithelial basement membrane dystrophy
- Meesmann juvenile epithelial corneal dystrophy
- Gelatinous drop-like corneal dystrophy
- Lisch epithelial corneal dystrophy
- Subepithelial mucinous corneal dystrophy
- Reis-Bucklers corneal dystrophy
- Thiel–Behnke dystrophy
Stromal dystrophies:
- Lattice corneal dystrophy
- Granular corneal dystrophy
- Macular corneal dystrophy
- Schnyder crystalline corneal dystrophy
- Congenital stromal corneal dystrophy
- Fleck corneal dystrophy
Posterior dystrophies:
- Fuchs' dystrophy
- Posterior polymorphous corneal dystrophy
- Congenital hereditary endothelial dystrophy
Main differential diagnosis include various causes of monoclonal gammopathy, lecithin-cholesterol-acyltransferase deficiency, Fabry disease, cystinosis, tyrosine transaminase deficiency, systemic lysosomal storage diseases, and several skin diseases (X-linked ichthyosis, keratosis follicularis spinolosa decalvans).
Historically, an accumulation of small gray variable shaped punctate opacities of variable shape in the central deep corneal stroma immediately anterior to Descemet membrane were designated deep filiform dystrophy and cornea farinata because of their resemblance to commas, circles, lines, threads (filiform), flour (farina) or dots. These abnormalities are now known to accompany X-linked ichthyosis, steroid sulfatase deficiency, caused by steroid sulfatase gene mutations and are currently usually not included under the rubric of the corneal dystrophies.
In the past, the designation vortex corneal dystrophy (corneal verticillata) was applied to a corneal disorder characterized by the presence of innumerable tiny brown spots arranged in curved whirlpool-like lines in the superficial cornea. An autosomal dominant mode of transmission was initially suspected, but later it was realized that these individuals were affected hemizygous males and asymptomatic female carriers of an X-linked systemic metabolic disease caused by a deficiency of α-galactosidase, known as Fabry disease.
Filamentous opacities appear in the cornea with intertwining delicate branching processes. During an eye examination, the doctor sees these deposits in the stroma as clear, comma-shaped overlapping dots and branching filaments, creating a lattice effect. Over time, the lattice lines will grow opaque and involve more of the stroma. They will also gradually converge, giving the cornea a cloudiness that may also reduce vision. The disease is bilateral, usually noted before the end of the first decade of life. Although lattice dystrophy can occur at any time in life, the condition usually arises in children between the ages of two and seven.
In some people, these abnormal protein fibers can accumulate under the cornea's outer layer—the epithelium. This can cause erosion of the epithelium. This condition is known as recurrent epithelial erosion. These erosions alter the cornea's normal curvature, resulting in temporary vision problems, and expose the nerves that line the cornea, causing severe pain. Even the involuntary act of blinking can be painful.
In systemic cases, kidney failure, heart failure and neuropathy such as facial nerve palsy, laxity of the skin may be noted.