Corneal dystrophy is a process in which a certain cell in normal corneal tissue is subjected to an abnormal genetic decision that causes progressive damage to its structure and function.
The disease is characterized by bilateral symmetry, mostly autosomal dominant, and occurs in the central cornea, without any inflammatory phenomena or neovascularization. It is characterized by the deposition of abnormal material in the cornea of both eyes. The disease often begins by invading only one layer of the cornea, but in later stages it may spread to adjacent tissues or even invade the whole cornea. It tends to respond poorly to drug therapy.
Classification (by anatomical site).
1, anterior corneal dystrophy.
2, corneal stromal dystrophy.
3, corneal endothelial dystrophy.
Clinical features and treatment of each type
I. Anterior corneal dystrophy
1, anterior corneal basement membrane dystrophy (map-like – dot-like – fingerprint-like dystrophy)
Symmetrical onset in both eyes, mainly seen in adults, often after 30 years of age, early without conscious symptoms.
(1) Clinical features: diffuse gray-white patches (map-like), small white creamy cysts of varying sizes (dot-like), and fine refractive lines arranged in circular concentric circles (fingerprint-like) are seen in the corneal epithelium, which are easily distinguished by slit lamp broadband light lateral illumination or posterior light irradiation method. Spontaneous corneal epithelial exfoliation (erosion), pain, photophobia, especially when the eyes are opened after sleep is easy to occur, can cause vision loss.
(2) Pathology: mainly in the epithelium and basement membrane, the basement membrane can be thickened by 2-6 um, dividing the epithelial cell layer into two parts, the front part is very easy to be exfoliated, the rear part of the cells near the abnormal basement membrane degenerates, liquefies, forms a vacuole or cyst-like, which contains degenerated and deformed cell nuclei and cytoplasmic debris.
(3) Treatment: No treatment is needed for those without conscious symptoms in the early stage. Late stage symptomatic patients can apply hypertonic eye water or eye ointment locally. If the lesion is located in the pupil area and affects vision, epithelial debridement is feasible to scrape the lesion epithelium or wear hydrophilic soft corneal contact lens, which can easily improve the symptoms and vision.
2.Meesmann corneal dystrophy
The disease starts in infancy, often symmetrical onset in both eyes, the disease progresses slowly, the course of the disease can be 30-40 years.
(1) clinical features: slit lamp microscopy, post-illumination method can be seen in the corneal epithelium scattered in numerous small dense dot turbidity, with direct focus illumination method, can be seen there are most of the tiny gray dots or transparent vesicles, sometimes arranged in a swirl, at this time with fluorescein often can not color, the lesion diffuse distribution, but the lid fissure corneal more obvious. In adulthood, some of the vesicles rupture, causing mild irritation such as photophobia and lacrimation.
(2) Pathology: thickening of the epithelial layer, insufficient maturation of the superficial cells, varying degrees of increased glycogen content, vesicle-like degeneration, intracellular cysts in the deeper cells, cysts containing debris, and positive PAS staining.
(3) Treatment: The disease generally does not require treatment, but if photophobia is obvious or seriously affects vision, it can be treated with soft contact lenses, superficial keratectomy or lamellar corneal transplantation.
Second, corneal stromal dystrophy
1, lattice-like corneal dystrophy
Visual impairment is more severe bilateral symmetrical autosomal dominant keratopathy, the onset of early, often before the age of 10 years.
(1) clinical features: early visible in the central cornea is mildly diffuse clouding, in the anterior elastic layer and stroma superficial layer with irregular branching thin stripes and dotted nodules, gradually increasing thickening, intertwined mesh or lattice, the peripheral part of the cornea is still 2-3mm transparent area, refractive character lines is the characteristic lesion of the disease, as the disease progresses, the lesion can be extended to the periphery and stroma deep layer or epithelial layer, so that corneal surface irregularity, together with superficial corneal scarring to gradually increase the degree of corneal clouding.
(2) pathology: corneal epithelial cell layer of varying thickness and irregular arrangement, fracture of the anterior elastic layer, distortion of the corneal stromal plate layer, some eosinophilic poke-shaped turbid deposits between the epithelial cell layer and the anterior elastic layer, histochemical examination showed that the deposits were amyloid material.
(3) Treatment: In early stages, if epithelial erosion occurs repeatedly, apply hypertonic eye ointment dressing or wear soft corneal contact lenses. For advanced vision loss can be performed corneal transplantation, lesions involving the deep layer of the cornea is best to perform penetrating corneal transplantation.
2, granular corneal dystrophy
The onset of the disease begins at an early age, but generally does not appear symptoms, with age, the disease gradually developed, can affect the vision to varying degrees, mostly accompanied by myopic astigmatism.
(1) Clinical features: grayish-white granular deposits in the superficial layer of the corneal stroma, deposits in the shape of round, oval, ring, snowflake, star and chain, etc., with scattered transparent areas at their intervals, mostly located in the central part of the cornea and transparent in the peripheral part of the cornea.
(2) Pathology: There is a darkly colored eosinophilic granular material in the corneal stroma, which is considered by histochemical analysis to be a non-collagenous fibrillar protein containing tryptophan, arginine and sulfur-containing amino acids.
(3) treatment: early vision is not affected without treatment, late when the focal fusion is a large area of clouding so that vision loss, penetrating or lamellar corneal transplantation can be performed, but PTK or corneal transplantation can recur within 3-5 years.
3.Patchy corneal dystrophy
Symmetrical onset in both eyes from the age of 3-9 years, the symptoms will appear around the age of 10 years, with progressive vision loss, and most of them will have lost most of their vision by the age of 30 years.
(1) clinical features: the whole corneal stroma gray-white cloudy, mist-like diffuse hairy glass-like appearance, the boundaries are unclear, the interval has a cloudy cloudy area, can involve the whole stroma, more likely to occur in the central part of the corneal shallow stroma and the peripheral part of the deep stroma, but still the central more serious, advanced lesions, the corneal surface is not flat, can occur recurrent epithelial erosion and different degrees of eye irritation symptoms, the posterior elastic layer The posterior elastic layer can also be invaded, and the anterior chamber of the formation of droplet-shaped superfluous, but the thickness of the parenchymal layer does not increase, but thinner than normal.
(2) Pathology: there are histochemically confirmed acidic mucopolysaccharides deposited in the subepithelium, anterior elastic layer, stromal plate interlayer, endothelial cells, and stromal layer keratocytes, and these deposits are clinically manifested as intra-stromal plaque-like clouding and posterior elastic layer droplets.
(3) Treatment: The most effective method is to perform penetrating corneal transplantation, but there is a possibility of recurrence after 2-10 years.
4, Schnyder central crystalline corneal dystrophy
A clinically rare form of corneal stromal dystrophy that can be associated with hyperlipidemia and hypercholesterolemia. Examination includes fasting blood cholesterol and triglyceride levels. It usually begins in infants around 1 year of age, and most have symmetrical onset in both eyes.
(1) Clinical features: fine yellowish-white needle-like crystals in the central superficial corneal stroma. These crystals shine in various colors and are disorganized or fenestrated, and in advanced stages there is total clouding of the central corneal stroma and dense senile rings.
(2) Pathology: Histochemical staining confirms the presence of cholesterol crystals, amorphous cholesterol, triacylglycerol and neutral fat deposits under the anterior elastic layer and within the stroma.
(3) Treatment: The effect on vision is small, and corneal transplantation is usually not required.
Third, corneal endothelial dystrophy
1.Fuchs’ corneal endothelial dystrophy
Usually begins at the age of 50-60 years, women are more than men about 2.5 times, the onset of both eyes, but usually asymmetric.
(1) clinical features: the first phase, also known as drop-shaped cornea, the central cornea after the manifestation of multiple small, drop-shaped warts protruding from the anterior chamber; second phase: also known as primary corneal endothelial loss of compensatory phase, for the stromal layer and epithelial layer corneal edema, epithelial and subepithelial vesicles develop into large vesicles, the stromal layer is hairy glass-like clouding, can appear obvious posterior elastic layer folds; third phase: scarring phase, deep and superficial layers of neovascularization grow into The large vesicles rupture repeatedly to form a scar.
(2) Pathology: the number of corneal endothelial cells decreases, the density decreases, the average cell area increases, the coefficient of variation increases, and the proportion of hexagonal cells decreases.
(3) Treatment: no special treatment is needed for asymptomatic phase I. Phase II can be localized with hypertonic drugs and anti-inflammatory and anti-infective eye ointment, wearing soft corneal contact lenses can reduce pain and increase visual acuity, and penetrating corneal transplantation is feasible for severe visual impairment in late phase
2.Posterior polymorphic corneal endothelial dystrophy
Can be congenital or can start in early childhood, the onset of both eyes, but usually asymmetric, early generally asymptomatic, visual impairment is relatively light.
(1) Clinical features: lesions are located in the posterior elastic layer, with linear or clustered aggregated blisters, gray clouding, or broad bands with irregular serrated edges. Iris abnormalities include anterior iris adhesions and pupil displacement, sometimes with corneal edema, and visible glaucoma.
(2) Pathology: there are pyknotic or nodular redundancies in the posterior elastic lamina (positive PAS staining).
(3) treatment: early material symptoms and visual acuity is not affected can not need to deal with, if corneal edema, clouding is obvious, affecting the visual acuity is serious, can perform penetrating corneal transplantation, if the secondary glaucoma, it is necessary to first anti-glaucoma surgery, to be reduced to normal intraocular pressure before the penetrating corneal transplantation, but often poor prognosis.
3, congenital hereditary corneal endothelial dystrophy
(1) Clinical features: corneal edema and clouding. The recessive and dominant genetic types have different clinical manifestations. Autosomal recessive inheritance: onset at birth, stable disease, no significant progression, nystagmus is common, less pain and photophobia. Total corneal edema, increased corneal thickness, and thickening of the posterior elastic lamina. Autosomal dominant: onset in childhood, slow progression, no nystagmus, often pain, tearing and photophobia. The cornea is diffusely edematous and cloudy with scattered gray spots.
(2) Pathology: granular deposits between the epithelial cells and stromal fiber plate layers, diffuse thickening of the posterior elastic layer, and vacuolation within the endothelium.
(3) Treatment: Early localized hypertonic drugs are available, and penetrating corneal transplantation is feasible in severe cases, but the surgical results are not very satisfactory.