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Query: UMLS:C0851184 (thinning)
 11,252 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Keratoconus is a condition in which the cornea assumes a complex irregular curvature caused by central corneal thinning. The abnormal topography of the cornea in combination with central corneal scarring results in an impaired visual acuity. Even in mild cases spectacles do not correct vision adequately. The use of hard contact lenses with a spherical geometry in the past has already given a marked therapeutic improvement. The use of these lenses however, is complicated by hypoxia and mechanical trauma of the cornea. These complications could theoretically be avoided by fitting elliptical lenses with a high oxygen transmission. To investigate this hypothesis we compared low oxygen-permeable spherical lenses with high oxygen-permeable elliptical contact lenses in a group of twenty patients with mild keratoconus. Our results showed both a marked subjective and objective visual improvement after fitting elliptical lenses with a low incidence of complications.
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PMID:Improvement of visual acuity and corneal physiology in keratoconus by fitting aspherical, high oxygen-permeable contact lenses. 191 21

Keratoconus is a corneal thinning disorder usually localized to the paracentral cornea. Though acute hydrops has been well described, perforation in keratoconus is an extremely rare event. We report a case of keratoconus with acute hydrops and perforation.
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PMID:Keratoconus with acute hydrops and perforation. Brief case report. 201 14

In order to identify the direct pathogenic factors involved in the stromal thinning of keratoconus, quantitative analysis of keratocytes, collagen fibers and collagen lamellae in keratoconus cornea was performed histologically by light and electron microscopy. Both normal and keratoconus corneas showed a similar cell density of keratocytes in the central stroma, therefore the total number of keratocytes in keratoconus cornea might be smaller than that of controls, because of the thinning of stroma in the keratoconus. The collagen lamellae in keratoconus corneas showed a significant decrease in number compared with controls. There was a direct relationship between the stromal thickness and number of collagen lamellae. On the other hand, there was no statistical significance between normal and keratoconus corneas in terms of the thickness of collagen lamellae. These results suggest that the thinning of the cornea in keratoconus might occur as the result of a defect of some collagen lamellae due to a disorganization during the process of collagen lamellae formation.
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PMID:[Quantitative analysis of collagen fiber in keratoconus]. 207 70

Signs of keratoconus, including Munson's sign, apical thinning, and Vogt's striae, developed in a 41-year-old woman 6 years after successful penetrating keratoplasty. Screening donor corneas for ectatic diseases may prevent such occurrences.
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PMID:Keratoconus after penetrating keratoplasty. 238 77

Keratoconus involves thinning and central protuberance of the cornea, scarring and significantly decreased vision. It is one of the major causes of corneal transplantation in this country, but the etiology of this disorder is unclear. In the present study stromal keratocytes were isolated and cultured from normal and keratoconus human corneas. Consistent with the phenotype of cornea thinning, we observed an increased gelatinolytic activity in keratoconus cultures. Characterization of enzyme properties in these cells suggested that gelatinase (type IV collagenase) was responsible for the majority of proteolytic activity found in this system. This elevated gelatinolytic activity was present in spite of lower amounts of total protein being produced by the keratoconus cultures.
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PMID:Altered gelatinolytic activity by keratoconus corneal cells. 247 30

Terrien's disease is characterized by slowly progressive thinning of the pre-limbal cornea in middle-aged patients. It usually leads to peripheral ectasia with marked astigmatism. It is rarely accompagnied by inflammation and its cause is unknown. Very few histopathologic examinations have been published, in particular those using electron microscopy We present detailed results concerning 6 patients in whom perforating keratoplasty permitted histopathologic and electron microscopic examination. Clinical and histological features reveal marked degeneration of the peripheral corneal stroma, with lipid accumulation unaccompagnied by significant inflammatory cellular infiltration in each case. Of interest is the association in one patient with keratoconus. The generally accepted pathogenic theories are fully discussed. The wealth of electron microscopic data provides a complete review of stromal degenerative changes.
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PMID:[Terrien's disease, apropos of 6 cases. Ultrastructural study]. 248 56

The type of corneal ectasia, the presence of breaks in Descemet's membrane, and the success with contact lens wear or penetrating keratoplasty were studied in 61 patients with corneal ectasia and vernal keratoconjunctivitis. There were 53 patients with keratoconus, 5 with pellucid marginal corneal degeneration, 2 with keratoglobus, and 1 with superior corneal thinning. The high rate of hydrops and the corneal ectasia itself may be related to excessive eye rubbing. Success with contact lens wear or penetrating keratoplasty in vernal keratoconjunctivitis patients with keratoconus is less than in patients with keratoconus alone.
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PMID:Corneal ectasia in vernal keratoconjunctivitis. 261 47

Three patients had pellucid marginal corneal degeneration complicated by corneal edema. The corneal edema appeared to be a result of a break or detachment of Descemet's membrane as a result of increasing corneal ectasia. The disruption in Descemet's membrane began just above the inferior, crescent-shaped area of stromal thinning. Therapeutic modalities initially included hypertonic solution to determine whether corneal edema would resolve spontaneously, apparently by endothelial migration with healing over the break in Descemet's membrane. One patient required thermokeratoplasty and another penetrating keratoplasty for persistent stromal edema. Acute hydrops can occur with pellucid marginal corneal degeneration by a pathogenesis similar to other noninflammatory corneal thinning disorders such as keratoconus.
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PMID:Acute hydrops in pellucid marginal corneal degeneration. 264 81

1. Keratoconus is a bilateral corneal dystrophy that causes a central corneal thinning. The onset is after puberty. 2. Non-surgical treatment of keratoconus is accomplished best with the use of rigid gas permeable contact lenses. 3. Penetrating keratoplasty is the procedure of choice when contact lenses fail.
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PMID:Keratoconus. 279 66

Keratoconus is a bilateral disorder of corneal shape which may be sporadic or genetically determined. Early corneal thinning suggests that a functional loss of structural elements is a primary event in the disease. Tensile strength of the cornea is reduced and is expressed by signs of rupture and scarring in Bowman's layer, scarring in the substantia propria, and rupture of Descemet's membrane. The overall stretching of the cornea results in an increase in curvature while an increased area of the corneal surfaces probably determines the onset and form of Fleischer's ring and the occurrence of endothelial polymegathism. Biochemical studies have shown an increase in collagenolysis and of reduceable collagen cross-links, but there is inconsistent evidence of altered solubility or of hydroxyproline or proteoglycan content. Of recent interest is the characterization of proteoglycan bridges along and between corneal collagen fibrils in keratoconus and the apparent loss of keratan sulphate demonstrated by electron-histochemical and x-ray diffraction techniques. The manner in which this could interfere with corneal strength is discussed.
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PMID:Keratoconus. 304 80


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