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

Posterior keratoconus is an unusual abnormality of the cornea generally classified as one of the anterior chamber cleavage anomalies. It is characterized clinically by the presence of a circumscribed or generalized corneal thinning with posterior depression of the cornea and is considered distinct from keratoconus. Although patients with posterior keratoconus may have visual complaints clearly related to their abnormal corneas, the surface topography of these corneas has not been studied in detail. Keratometry and photokeratoscopy provide an incomplete picture of the surface geometry of posterior keratoconus. We utilized computer assisted topographic analysis to study the cornea of a patient with posterior keratoconus. The Topographic Modeling System demonstrated that the patient's cornea showed a central steepened "cone" coincident with the area of circumscribed posterior keratoconus as well as paracentral flattening. This report documents the topographic abnormality in this rare disorder.
Cornea 1992 Jul
PMID:Corneal topography of posterior keratoconus. 142 57

During examination of 131 penetrating keratoplasty specimens from patients with keratoconus obtained in an 11-year period, we observed two histopathologic variants based on the appearance of Bowman's layer and the corneal epithelium. "Typical" keratoconus specimens had multiple breaks in Bowman's layer and central epithelial thinning, whereas "atypical" corneas lacked breaks in Bowman's layer and had less thinning of the central epithelium. Ninety-five corneas were from patients who underwent grafting in only one eye. Seventy-six (80%) of these corneas were "typical" and 19 corneas (20%) were "atypical" in appearance. Both variants had similar degrees of central stromal thinning. Patients with "typical" and "atypical" corneas differed demographically by race only; 49% of "typical" and 95% of "atypical" corneas were from white individuals. Thirty-six corneas were from 18 patients who underwent bilateral penetrating keratoplasty. The histologic appearance of these corneal pairs was concordant in 13 patients and discordant (one "typical" and one "atypical" cornea) in five patients. Statistical analysis indicated that this distribution is not significantly different from that predicted by chance and suggests that "typical" and "atypical" corneas are manifestations of the same disease process.
Cornea 1992 Nov
PMID:Histopathological variation in keratoconus. 146 18

Posterior amorphous corneal dystrophy (PACD) is a rare autosomal-dominant disease, generally classified with the pre-Descemet's dystrophies. It is characterized by deep stromal corneal opacification, flat corneas with low keratometry values, and central thinning. To our knowledge, only one previous ultrastructural study has been published on this disease. This 5-year-old white boy presented with best corrected vision (20/50 right and 20/60 -2 left). The corneas had dense opacities, bilaterally, deep in the corneal stroma. Keratometry was 39.50/40.50, bilaterally. The patient's father had 20/20 vision, bilaterally, with minimal opacifications in the deep corneal stroma. A penetrating keratoplasty was performed. In contrast to the previously reported case of PACD, in which the abnormalities were largely limited to the stroma, our patient had subepithelial deposits, only mild stromal abnormalities, and a thick collagenous layer posterior to Descemet's membrane, thus suggesting that this variant of PACD is a generalized corneal disease including endothelial and epithelial abnormalities, rather than a pure stromal dystrophy.
Cornea 1992 Mar
PMID:Posterior amorphous corneal dystrophy. An ultrastructural study of a variant with histopathological features of an endothelial dystrophy. 158 20

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.
Cornea 1991 Jan
PMID:Keratoconus with acute hydrops and perforation. Brief case report. 201 14

Autogenous periosteum was used to reinforce scleral thinning, perforation, or corneoscleral wound dehiscence in four eyes of three patients with necrotizing scleritis or peripheral ulcerative keratitis associated with advanced rheumatoid arthritis. All grafts have remained intact during an average follow-up interval of 36 months (range, 19-52 months). The postoperative visual acuity ranged between 20/30-20/60. Two eyes exhibited age-related macular degeneration, and one eye had an epiretinal membrane postoperatively. No systemic complications occurred following surgery.
Cornea 1990 Apr
PMID:Long-term follow-up study of scleroplasty using autogenous periosteum. 232 82

For the first time, we report the pathologic changes in the corneal endothelium of the Royal College of Surgeons (RCS) rat with inherited retinal dystrophy. In the 26-day-old RCS rat, scanning electron microscopy (SEM) revealed several mushroom-like microvilli on the endothelial surface. Transmission electron microscopy (TEM) showed vesicle-like structures that corresponded to the mushroom-like microvilli. However, in the 90-day-old RCS rat, the corneal endothelium had numerous filamentous microvilli, and half of the endothelial cells had cytoplasmic edema, which was also observed by TEM. In the 180-day-old RCS rat, SEM showed numerous slender microvilli on the corneal endothelium. TEM showed thinning of the cells, with loss of cytoplasm and organelles, and thickening of Descemet's membrane. These endothelial changes could be caused by the toxic substances derived from the degenerating photoreceptor cells in the dystrophic retina.
Cornea 1990 Jul
PMID:Corneal endothelial abnormalities in the Royal College of Surgeons rat. 237 16

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.
Cornea 1988
PMID:Keratoconus. 304 80

Pellucid marginal corneal degeneration is a bilateral disease characterized by a narrow band of corneal thinning localized 1-2 mm from the inferior limbus. The disease is diagnosed usually between 20 and 50 years of life, and its etiology remains obscure. During the clinical course and evolution of pellucid marginal corneal degeneration, acute hydrops with corneal edema in the lower half may develop (acute pellucid marginal corneal degeneration). However, since cases of acute pellucid marginal corneal degeneration are not frequently encountered in clinical practice, each new patient is evaluated and managed with the utmost care to contribute to our better understanding of this disease. This is a report of two cases of acute pellucid marginal corneal degeneration that had a relatively favorable functional outcome when treated medically, so that corneal grafting was not necessary.
Cornea 1988
PMID:Acute pellucid marginal corneal degeneration. 321 64

A case of vernal keratoconjunctivitis is presented with a similar clinical presentation and disease type identified in each of two fraternal twins. The unique findings of superior stromal infiltrates and corneal marginal thinning are discussed.
Cornea
PMID:Vernal keratoconjunctivitis: new corneal findings in fraternal twins. 657 93

A 24-year-old man presented with narrow, linear areas of thinning situated horizontally in the upper part of both corneas. These areas were associated with progressive corneal ectasia, causing high degrees of "against the rule" astigmatism. By excising the affected areas, the refractive error was significantly improved in both eyes. Features of the disease suggested that the condition was related to the other ectatic corneal dystrophies.
Cornea 1995 Jan
PMID:Bilateral linear corneal ectasia. An unusual case and its surgical management. 771 29


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