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

Rabbit corneas were perfused in vitro with an irrigation solution for 90 minutes. This was followed by 6 hours of perfusion with tissue culture medium TC199 during which endothelial function was assessed by monitoring rates of swelling during a period of perfusion in the absence of bicarbonate ions, and subsequent rates of thinning when bicarbonate ions were restored to the perfusate. Corneal thickness (measured with an ultrasonic pachymeter) immediately following excision was 401 microns (SD 19, n = 23). During the 90 minute perfusion at 35 degrees C, corneas exposed to balanced salt solution (BSS), Hartmann's solution or 0.9% NaCl (all initially at room temperature) swelled, respectively, at 14 (SD 2.3, n = 4), 11 (SD 2.6, n = 4), and 70 (SD 4.3, n = 4) microns/h. Cold Hartmann's solution (initially at 4 degrees C) caused corneas to swell at 9 (SD 2.3, n = 4) microns/h. On the other hand, corneas perfused with BSS Plus thinned at 9 (SD 3.4, n = 4) microns/h and TC199 with Earle's salts had little effect on thickness. Rates of swelling and thinning during the following assessment perfusion showed no apparent effects of prior exposure to any of the irrigation solutions on the barrier properties or pump function of the endothelium. Despite this, the increased thickness of corneas exposed initially to BSS, cold Hartmann's solution, or 0.9% NaCl was not fully reversed, even by the end of the 6 hour assessment perfusion. In contrast, the swelling observed in corneas exposed to Hartmann's solution at room temperature was reversed and these corneas had returned to their normal thickness by the end of the assessment period. All corneas, even those exposed to 0.9% NaCl, had an intact endothelial mosaic with no evidence of damage or cell loss, although morphological differences in cell shape and the appearance of cell borders were evident compared with freshly isolated cornea.
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PMID:Effects of irrigation solutions on corneal endothelial function. 761 71

High-frequency ultrasound biomicroscopy is a new method of examining subsurface anterior segment structures of the eye at microscopic resolution. The sclera has a high internal reflectivity and can be differentiated from the cornea, and overlying and underlying tissue. Using this modality, we examined 18 patients with various manifestations of scleral disease. Localized anterior staphyloma could be differentiated from other causes of a black spot on the scleral surface. Episcleral thickening could be differentiated from involvement of the sclera itself. Different patterns of scleral involvement could be imaged including diffuse low-reflective mottling, low-reflective nodules extending into the scleral substance, and scleral thinning. Scleral thinning could be assessed and quantified. Underlying changes in the vitreous could be detected. Ultrasound biomicroscopy was a useful adjunct to clinical examination in the assessment of anterior scleral disease.
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PMID:Ultrasound biomicroscopy in the assessment of anterior scleral disease. 823 25

Keratoconus is characterized by stromal thinning and conical deformity of the cornea that affects a small but significant portion of the population. Although keratoconus has been well studied, endothelial changes have not been extensively investigated. We studied the endothelium of 14 keratoconus corneal buttons obtained over the past 6 years by penetrating keratoplasty using light microscopy, scanning electron microscopy and transmission electron microscopy. Observations were correlated with patient history. Corneas demonstrated: endothelial cell pleomorphism and polymegathism (6 corneas); endothelial cell degeneration (13), and evidence of anterior chamber inflammation (4). Patterns of endothelial damage were variable ranging from isolated cell membranolysis to denudement of Descemet's membrane. Less damage was present at the apex of the cones than that observed in a circumferential pattern at the bases. In general the damage observed correlated with the severity and duration of the keratoconus with 9 years being the dividing time between mild and severe endothelial cell damage. These observations support other studies that implicate contact lens wear as a cause of pleomorphism and polymegathism in these patients. Endothelial cell alterations are likely a secondary event occurring due to mechanical stresses.
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PMID:Pathology of corneal endothelium in keratoconus. 827 66

The aims of the Australian Corneal Graft Registry are to collect and collate statistical information on the practice of corneal transplantation around Australia, to identify risk factors for corneal graft failure, and to provide information on graft and visual outcome. The current report encompasses analyses performed on 3608 corneal grafts (96% penetrating and 4% lamellar) entered into the Registry between May 1985 and July 1991. Sixty-four per cent of grafts have undergone one or more rounds of follow-up by the 189 contributing surgeons and 110 additional referring practitioners: five-year Kaplan-Meier graft survival for penetrating and lamellar grafts is 72% and 84%, respectively. The main indications for penetrating keratoplasty were keratoconus (31%), bullous keratopathy (25%), history of failed previous graft (14%), corneal scars and opacities (11%), and corneal dystrophies (7%). The most common reasons listed for failure of penetrating grafts were rejection (33%), glaucoma (11%), non-viral infections (10%), endothelial cell failure (8%) and herpetic infection (7%). In 19% of cases, the reason for graft failure was unclear. The main indications for lamellar keratoplasty were pterygium (32%), thinning, necrosis or ulceration from old beta-radiation therapy for pterygium (17%), and scleral ulcers, necrosis, ectasia, perforations or melts (29%). The most common reasons for the failure of lamellar grafts were corneal melting (43%) and sloughing of the graft (29%). Among the factors that influenced the survival of penetrating corneal grafts to a significant extent (P < 0.05) in univariate analysis were: the centre effect, indication for graft, graft number, a history of pregnancy or blood transfusion, inflammation before or at the time of graft, corneal vascularisation at the time of graft, a history of raised intraocular pressure, the donor cornea procurement source, the death to donor cornea enucleation time, graft size and large degrees of oversizing, lens status and the type of intraocular lens in situ. In the postoperative period, risk factors for failure included early removal of graft sutures, neovascularisation of the graft, herpetic recurrences in the graft and the occurrence of rejection episodes. The variables that best predicted penetrating corneal graft failure in Cox proportional hazards regression analysis were aphakia or the presence of an anterior chamber of iris-clip intraocular lens, very small or very large grafts, a history of previous ipsilateral graft, an indication for graft that was neither keratoconus nor any of the corneal dystrophies, inflammation at the time of graft, and a postoperative rise in intraocular pressure.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The Australian Corneal Graft Registry. 1990 to 1992 report. 833 42

Many investigators have measured corneal thickness after keratoplasty using organ culture and storage mediums. Values for corneal thickness were found to stabilize 6-12 months postoperatively, reaching normal values. We followed 59 corneal transplant recipients whose donor tissue was obtained from organ culture (average preservation time 13 days) for > 1 year retrospectively. The overall graft survival was 95.3%. The graft was thick in the early postoperative period. It subsequently became thinner, reaching the lowest level 5-9 months postoperatively (mean 0.48 mm, SD 0.04). After this period the corneas gradually became thicker and reached the normal corneal thickness. The extreme thinning of transplanted corneas in the first postoperative year has not been described before. We found a negative correlation between conservation time and thickness 5-9 months postoperatively. We postulate that organ culture may have a high impact on keratocyte function.
Cornea 1993 Jul
PMID:Extreme temporary thinning after keratoplasty of organ-cultured corneas. 784 17

Keratoconus, a bilateral corneal disease, is characterized by modifications in corneal shape and thinning of the stroma. It affects young people. From a biochemical point of view, a decrease in collagen content, probably due to the high collagenase activity, has been reported. In these experiments, we have studied the membrane receptors for interleukin 1 alpha, and the corresponding dissociation constant (KD). We also investigated synthesis of prostaglandin E2 (PGE2) and collagen, as well as kinetics of cyclooxygenase. Data from normal human corneas and from keratoconus were compared. Fibroblasts from keratoconus proved to bear four fold more IL1 binding sites than those from normal cornea, with similar KD. Both types of cells synthesize prostaglandin E2, even if IL1 is not added to the medium, but the keratoconus cells produce ten times more than the normal cornea cells. When the cells are stimulated with IL1, synthesis of PGE2 strongly increases and the amounts produced by keratoconus cells are always higher than those of the normal cornea cells. Kinetics of the cyclooxygenase show that Vmax. is 10 times higher in keratoconus than in normal cornea cells; Km's are the same. The amounts of collagen synthesized by keratoconus cells are slightly lower than those of normal cornea cells. Addition of IL1 to the cultures enhances synthesis of collagenase by the cells and decreases collagen found in the culture media. The drop of collagen is more important in keratoconus than in normal cornea cell cultures.
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PMID:Modification of prostaglandin E2 and collagen synthesis in keratoconus fibroblasts, associated with an increase of interleukin 1 alpha receptor number. 840 71

Human type IV collagen discs were found to support proliferation and adhesion of rabbit corneal epithelial cells in tissue culture. To assess the biocompatibility of this synthetic collagen for epikeratoplasty, seven eyes of seven rhesus monkeys underwent epikeratoplasty with lenticules made of human type IV collagen. Eye rubbing by the animals expulsed two of the lenticules and caused failure of two to epithelialize completely. The remaining three lenticules epithelialized, remained clear, and caused no adverse effects on the eye. Two of these lenticules developed focal areas of subepithelial thinning 3 months postoperatively and the third lenticule has remained stable for 30 months. The presence of epithelial attachment components at the epithelial-lenticule interface was demonstrated by immunolocalization. Histopathologic and ultrastructural examination revealed focal areas of epithelial invasion and degradation of the lenticule. Neutral proteases were detected in the thinning region of one specimen. Human type IV collagen supports epithelialization in vivo and may have potential as a biomaterial for epikeratoplasty, but the stability of the material must be improved.
Cornea 1993 Jan
PMID:Synthetic epikeratoplasty in rhesus monkeys with human type IV collagen. 845 30

Eleven patients with blue sclera, limbus-to-limbus corneal thinning, hypermobile joints, and consanguineous parents were examined between January 1983 and September 1991. The clinical diagnosis was consistent with the Ehlers-Danlos syndrome type VI phenotype in all patients. A "halo" sign at the limbus was present in all patients. Corneal rupture occurred in seven patients (nine eyes) either spontaneously or following minimal trauma. Acute hydrops occurred in three patients. Bilateral microcornea was present in one patient and two patients had a unilateral increased corneal diameter as a result of secondary glaucoma after trauma. Peripheral sclerocornea was present bilaterally in five patients. Curvature abnormalities included cornea plana, keratoconus, and keratoglobus.
Cornea 1993 Jan
PMID:Corneal abnormalities in Ehlers-Danlos syndrome type VI. 845 32

The biocompatibility of hydrogel intracorneal lenses (ICLs) implanted in monkey eyes was evaluated for periods ranging up to five years. Seventy-three plus or minus powered ICLs made of Lidofilcon A (68% water) or Lidofilcon B (79% water) were implanted following lamellar dissection with a microkeratome. Ten sham surgical procedures were performed without ICL implantation as controls. Eyes were followed for up to five years by slitlamp biomicroscopy and specular microscopy. Light and transmission electron microscopic evaluations of enucleated eyes were performed at various intervals. Minimal tissue reaction was noted; both hydrogel materials appeared to be equally well tolerated. Failures usually occurred as a result of microkeratome problems encountered during surgery. Histopathological changes to the cornea included epithelial thinning anterior to the thickest portion of the ICL, fibroblastic activity along the ICL-stromal interface, and deposition of an amorphous extracellular material adjacent to the ICL. These observations did not appear to be clinically significant as the eyes were quiet by slitlamp examination. Removal of three ICLs eight to ten months prior to enucleation restored the normal histological characteristics of the cornea. The endothelial cell density of ICL-implanted eyes decreased by 4.3% (n = 17) six months after surgery but remained stable thereafter. The variation in endothelial cell area and percentage of hexagonal cells did not change over 50 months. The results appear to demonstrate that high water content synthetic ICLs can be well tolerated in the monkey cornea for up to five years.
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PMID:Assessment of the long-term corneal response to hydrogel intrastromal lenses implanted in monkey eyes for up to five years. 848 63

We evaluated rigid contact lens associated changes in central corneal thickness using an improved method of pachometry. After altering one lens parameter (e.g., lens diameter or base curve) and keeping all other parameters constant, we evaluated 30 rigid lens patients at 4-hour intervals over 20-hour periods. Using micropachometry we were able to detect changes as small as 10-20 microns in the central cornea region. We found that the degree of corneal swelling from rigid contact lens wear can vary from one area to another. Thinning in one area can result from lens compression, while thickening in an adjacent area can result from lens-induced hypoxia. Using micropachometry for the early detection of corneal changes such as thinning may help to avoid problems associated with long-term lens wear.
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PMID:Micropachometric investigation of rigid contact lens-induced corneal dystrophies. 826 1


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