Guttate cornea

Introduction Fuchs endothelial dystrophy, also known as cornea guttata, is a common phenomenon that increases significantly with age. In many patients with keratoconus, other aspects of the cornea are normal and do not affect vision. A small number of patients with corneal stroma and epithelial edema can cause significant loss of vision.

Cause

(1) Causes of the disease

The disease has a certain hereditary nature, the genetic pattern is not very clear, and some cases have been confirmed as autosomal dominant inheritance. The cause is unknown, and it may be multifaceted. Some unrecognized factors interfere with the structure and function of corneal endothelial cells, which ultimately leads to decompensation of endothelial pump function.

In addition to the disease, the disease is an autosomal dominant genetic disease. In 2001, Biswas et al. performed a genomic analysis on a family and found that the Q455K missense mutation occurred in the type VIII collagen Alpha2 (COL8A2) gene located in the short arm 1p34.3-p32 of chromosome 1. This may interfere with the terminal differentiation of corneal endothelial cells by type VIII collagen, disturbing the structure and function of corneal endothelial cells, resulting in abnormal basement membrane and fibrillar collagen product, drip. DDT is further damaged by corneal endothelial cells, which finally causes degeneration of corneal pump function and anti-apoptotic function, resulting in loss of useful vision.

Primary dystrophic corneal endothelial cells may cause collagen deposition behind the posterior elastic membrane. The simple drop corneal histology is the appearance of a sputum or sputum biological appearance, and in other cases it may be localized collagen deposition, an extra-covered basement membrane or a uniformly thickened posterior collagen layer. However, viral particles were found on a case of Fuchs endothelial dystrophy corneal specimens, suggesting the possibility of acquiring a causal cause.

(two) pathogenesis

Although the underlying abnormalities of the endothelium in Fuchs endothelial dystrophy are still unclear, the pathogenesis seen in clinical practice has the following aspects.

1. Increased collagen production: more behind the posterior elastic layer and under the epithelium. As with many other corneal diseases, Fuchs malnourished abnormal endothelial cells produce excess collagen, including abnormalities with sparse collagen, basement membranes, and layers of looser fibrillar collagen. Subepithelial connective tissue comes from fibroblasts that migrate from the limbus or stroma, but some of them may also come from the epithelium.

2. Endothelium barrier function and pump function reduction: can occur at the same time as endothelial degeneration changes and is destroyed. The connection of the apical space of the cell is disrupted, allowing aqueous humor to pass through the endothelial barrier into the stroma and epithelium. Since the diseased endothelium is unable to pump these fluids, the epithelial barrier prevents it from escaping from the front of the cornea, causing edema of the cornea. In the late stage of the disease, the formation of scar under the epithelium prevents the liquid from entering the epithelium. The scar formation of the matrix causes the cornea to no longer thicken. The posterior collagen tissue increases the toughness of the posterior cornea and is difficult to swell. Therefore, the corneal structure is tighter than before, and the patient feels more comfortable. . The density of Na+-K+ pump (Na+-K+ATPase) in corneal endothelial cells increased significantly in the early stage of the disease. As the disease progressed, the density of Na+-K+ pump gradually decreased, and the final pump function was completely lost.

3. Glaucoma pathogenesis

(1) Effects of intraocular pressure on corneal endothelium: There are controversies about the association between glaucoma and dysmenorrhea and Fuchs endothelial dystrophy. One of the reasons is that elevated intraocular pressure often leads to secondary changes in corneal endothelium. Endothelial cell density reduction can be seen in: open angle glaucoma, angle-closure glaucoma and some secondary glaucoma, but the degree of corneal endothelium changes is not always consistent with the degree of intraocular pressure elevation, suggesting other factors (such as age or before) Uveitis) affects the relationship between glaucoma and changes in corneal endothelium. Therefore, in the evaluation of the relationship between glaucoma and the drip cornea and Fuchs endothelium nutrition, the above factors must be considered.

(2) Droplet cornea and aqueous humor outflow: patients with drip cornea have a higher incidence of abnormal aqueous humor fluence, but subsequent studies have confirmed that the mean value of aqueous humor flow coefficient in the drip corneal group is not statistically different from the normal group. There was also no association between the extent of keratopathy and the fluency coefficient of aqueous humor. A comparison of the drip corneal group with the drop-free corneal matching group revealed that the former had a lower mean intraocular pressure.

(3) Fuchs endothelial dystrophy and glaucoma: The relationship between open-angle glaucoma and Fuchs endothelial dystrophy remains unclear. It has been estimated that 10% to 15% of patients with Fuchs endothelial dystrophy have open-angle glaucoma. However, in the Fuchs Endothelial Dystrophy study, there was no genetic overlap between Fuchs endothelial dystrophy and primary open angle glaucoma.

Patients with shallow anterior chamber and Fuchs endothelial dystrophy are prone to angle-closure glaucoma. Obviously, this is the result of the gradual thickening of the cornea and eventually the closure of the corner. In the past, some authors proposed closed-angle glaucoma, especially acute angle-closure glaucoma with iris atrophy, and the incidence of drip cornea was higher. It has also been suggested that the anterior chamber of the patients with smear cornea or Fuchs endothelial dystrophy has a shallower anterior axis, but another study suggests that these two unrelated abnormalities exist simultaneously and may affect each other.

an examination

Related inspection

Eye and sacral area CT examination ophthalmologic examination

First, the corneal photo method

Corneal phototherapy is one of the methods for the treatment of exposed keratitis. Exposure keratitis is common in various lesions of cleft palate, causing corneal exposure and blink dyskinesia. The tears cannot properly wet the cornea. Corneal epithelial damage occurs.

Second, corneal examination

The corneal examination method includes photogrammetry, staining, and perceptual examination. It can also be used with Cochet and Bonnet's corneal sensory meter. It can accurately detect eye diseases by using various examination methods, and also has a healthy eye.

Third, genetic testing

Genetic testing can determine the genetic pattern.

1. Iris keratoscopy: You can understand the involvement of trabecular meshwork.

2, corneal endoscopic surface microscopy: can understand the posterior elastic layer and corneal endothelium lesions.

3, pathological examination: the number of corneal endothelial cells is reduced, thinning, Descemet membrane thickening and drip-like sputum located behind it, this sputum can protrude into the front room, can also be buried in the back of the Descemet membrane. The parenchymal layer is edema, the interlamellar gap is widened, the collagen arrangement is disordered, and the corneal cells are increased. The Bowman layer is essentially intact, with focal fractures in some areas, connective tissue invasion at the break, and extension to the epithelial cell layer. The epithelial basal cells are edema, the intercellular space is enlarged, and there is a connective tissue layer between the epithelial basement membrane and the Bowman layer. The focal thickening of the nascent collagen tissue forms scattered sputum or sputum, that is, the corneal degeneration point. There are four manifestations: 1 simple condyle into the anterior chamber. 2 multi-layer layers. 3 piled up in the multi-layer structure. 4 innocent multi-layer organization. Some neoplasms form lumps, and some are mushroom-shaped.

4. Scanning electron microscopy: It can be seen that the neoplasms squeeze the endothelial cell into a dumbbell shape or a prism shape, which makes the covered endothelial cells thin, and makes the cell boundary irregular, and destroys the integrity of the endothelial mosaic pattern. Endothelial cells are enlarged, and dark spots of varying sizes can appear, exceeding the edges of their cells. Even if you lose its typical hexagonal structure, it usually covers the posterior surface of the cornea.

5. Transmission electron microscopy: It shows that some cytoplasm of endothelial cells have vacuoles, nuclear shrinkage and other degeneration phenomena, some contain melanin particles, and some endothelial cells have morphological characteristics of fibroblasts (endoplasmic reticulum increases, cytoplasm is full) Microfilaments and ribosomes; others have characteristics similar to epithelial cells (surface microvilli, intercellular desmosomes). The most prominent change is the diffuse thickening of the Descemet membrane. It is characterized in that there is no obvious change in the front strip layer, and the rear non-belt layer is thinned or missing, and a strip layer composed of a collagen base film material is added behind it. In some areas, the limitations are dense and thick, and the back is prominently dripping. Filaments and amorphous substances sometimes appear between the drip and the endothelial cells.

Differential diagnosis

Differential diagnosis of the drip cornea:

First, keratitis

(a) superficial keratitis

1 The primary lesion can be caused by a virus. Epidemic keratoconjunctivitis caused by adenovirus type VII, epidemic hemorrhagic conjunctivitis caused by enterovirus. It can cause inflammatory infiltration under the corneal epithelium and epithelium. Fluorescein staining is punctately colored with varying thicknesses. In the case of herpes simplex epithelial infection, it is punctate, star-shaped or linear, and gradually develops into dendritic or map-like opacity.

2 secondary to the inflammation of adjacent tissues, such as heavier acute conjunctivitis, invading the peripheral part of the cornea, superficial corneal infiltration, edema, epithelial exfoliation, and more point-like opacity. Fluorescein staining was positive. If the lower third of the cornea has dense punctate dermatitis and erosion, often associated with staphylococcal eyelid inflammation.

(B) corneal stroma

Most of them are immune reactions, and can also be caused by direct invasion of pathogenic microorganisms. Congenital syphilis is the most common cause, tuberculosis, herpes simplex, banded sores, etc. can also cause the disease. A deep keratitis, the lesion is located in the deep layer of the corneal stroma, infiltrating turbidity and edema. The lesions are thickened with a posterior elastic layer wrinkle and have a frosted glass appearance. Vision loss, ciliary congestion, may be associated with iridocyclitis. In the late stage, the neovascularization is surrounded by the corneal stroma, which is brush-like and rarely branched. The cornea can still return to transparency after the inflammation of the light is subsided. If the substrate layer is necrotic, deep scars of varying thickness will be left behind.

(three) corneal ulcer

The cornea has a gray-white infiltration, the boundary is not clear, the surface is tarnished, followed by tissue defects forming ulcers, and fluorescein staining is positive. The severe irritant symptoms are obvious, the ciliary congestion is significant, the ulcer is large and deep, with anterior chamber empyema, and can be perforated.

Claudication corneal ulcer

It is an acute suppurative corneal ulcer. More common in the elderly or have chronic dacryocystitis. Acute onset, often 1-2 days after corneal trauma, eye pain, photophobia, tearing, decreased vision. Ciliary congestion or mixed hyperemia. The cornea has a gray-yellow dense infiltrating foci with blurred boundaries and a rapid formation of ulcers. The base of the ulcer is filthy, covered with necrotic tissue, and the edge of the ulcer is sneak-extended to the surrounding and deep. Fluorescein staining was positive. Often accompanied by iridocyclitis, a large amount of cellulose-like exudate and empyema in the anterior chamber. The pupil is small and sticks behind. The severe cornea is easy to perforate, or even develop into endophthalmitis. Pathogens can be found by scraping or culturing. Such as pneumococcus, hemolytic streptococcus, Staphylococcus aureus and so on.

2. Pseudomonas aeruginosa corneal ulcer

It is a severe suppurative keratitis caused by Pseudomonas aeruginosa infection. Often caused by trauma, corneal foreign body removal, or using equipment contaminated with Pseudomonas aeruginosa, syrup (such as fluorescein), contact lens. Rapid onset, more than a few hours or 1-2d, severe pain, decreased vision, swelling of the eyelids, conjunctival congestion and edema, yellowish white necrosis on the cornea, slightly bulging on the surface, rapidly expanding, surrounded by a dense annular infiltration. The anterior chamber has a large amount Corneal necrotic tissue shedding forms a large area of ulcers and produces a large amount of yellow-green viscous secretions. If not controlled quickly, all perforations are dissolved within 1-2d. A bacteriological examination of the scraper can be found in Gram-negative bacilli. The culture of Pseudomonas aeruginosa can be clearly diagnosed.

3. Fungal corneal ulcer

There are often agricultural corneal trauma, and the incidence of high-temperature seasons is high. It is characterized by slow onset, long course of disease, and irritating symptoms are heavier than the former two. The color of the ulcer is white, the surface is dry and rough, and it is like "tongue" or "toothpaste". It seems to have a dry and hard feeling and is easy to scrape. "Pseudo-foot" or "satellite stove" is sometimes seen around the central lesion. There is a flaky gel-like deposit on the posterior wall of the cornea. The anterior chamber has thick empyema. The scraper can find the hyphae and the diagnosis can be established. Culture of visible pathogenic fungi. Such as Fusarium, Aspergillus, Penicillium, Candida albicans, yeast and so on.

Second, corneal trauma and foreign body retention

Mechanical or chemical damage, may have epithelial edema, exfoliation. Corneal opacity in the area of injury. Severe cases have major tissue damage, even corneal perforation, with adjacent tissue damage. Corneal foreign body survivors. In addition to the turbidity of the foreign body tissue, there is turbidity or pigmentation around the foreign body. Metal foreign matter can be seen in metal rust. It can be identified by a magnifying glass or a slit lamp microscope.

Third, corneal degeneration or malnutrition

(1) Old age ring

It mainly occurs in the elderly and is a lipid infiltration in the stromal layer of the cornea. Symmetrical on both sides, there is a ring of white rings at the limbus, and the ring width is about 1mm. The naked eye was observed by the naked eye to be separated from the limbus by a transparent band, and the boundary of the inner edge was unclear. Slit lamp microscopy, the optical section can be seen turbid, the deep part comes from the rear elastic layer, and the turbidity is also downward from the front elastic layer. No inflammatory irritation, does not affect vision.

(B) banded keratopathy

It is a calcium deposit located in the pre-corneal elastic layer. The cause is still unclear, which may be related to hyperthyroidism, sarcoidosis, renal calcinosis, vitamin D poisoning, and high concentrations of calcium and phosphate in blood and interstitial fluid. Or corneal water evaporation in the palpebral zone promotes an increase in local calcium salt concentration. The volatilization of carbon dioxide increases the local pH value, which is beneficial to the precipitation of calcium and phosphate. The cornea lacks blood vessels, resulting in minimal buffering of blood to pH. The clinical manifestation is that the exposed part of the corneal cleft palate shows a banded calcareous deposit. Deposited on the epithelial basement membrane, the pre-elastic membrane and the shallow matrix. There are many holes in the elastic layer in front of the belt turbid zone. The lesion spreads from the periphery to the central part and has no neovascularization. The disease should be differentiated from corneal calcium degeneration. The latter deposition of calcium involves the deep tissue of the cornea. Often for severe eye trauma, eye praise, long-term chronic iridocyclitis and secondary glaucoma.

(three) corneal dystrophy

It is a genetically related primary progressive keratopathy. Symmetrical bilateral vision, slow progression of the disease, early cases are often found in physical examination. Most types of corneal dystrophy lesions begin with a layer of tissue or cells. After years of development, it affects or affects adjacent tissues or cells, and even affects the full-thickness cornea, causing severe visual dysfunction. According to the initial anatomy of the primary lesion, it is divided into three categories, namely, the anterior cornea, stromal and posterior corneal dystrophy.

1. Map-like-point-one fingerprint-like malnutrition: a representative of malnutrition in the front. More than 30 years old. There are many gray patches, tiny cysts or tiny lines in the central epithelium of the cornea. There may be recurrent corneal epithelial exfoliation and temporary blurred vision.

2. Granular corneal dystrophy: This is representative of corneal stroma malnutrition. It is an autosomal dominant genetic disease. There is a localized dispersion of particulate transparent material in the pre-corneal stroma. The lesions are mostly in the central part. In the advanced stage, there may be visual impairment.

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