ISSN:1395-3907    

DOI:10.1111/j.1600-0420.1995.tb00001.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:1395-3907    

DOI:10.1111/j.1600-0420.1995.tb00002.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:1395-3907    

DOI:10.1111/j.1600-0420.1995.tb00003.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTA video camera, a microscope, and a PC‐based digital image processing board were assembled for in vitro studies of corneal biomechanics. Central tangential corneal strain was determined by placing pairs of tiny mercury droplets on the epithelial surface and on the endothelial surface of the cornea. A distance of 3.2 mm could be determined with a standard deviation of 1.2 μm. Central corneal radius of curvature was measured from digital traces of the corneal surface contour. The standard deviation on estimating the radius of an 8 mm steel sphere was 15 μm. Corneal thickness was measured by digital optical pachometry. The standard deviation on measuring a thickness of 1 mm was 4.6 μm. The corneal extensibility was investigated in a total of 10 enucleated human eyes with increased corneal hydration. Tension was applied by varying the intraocular pressure from 2 to 100 mmHg with a column of isotonic saline. The epithelial side corneal strain and the increase in corneal curvature were approximately 1% for a change in intraocular pressure from 2 to 100 mmHg. When a high intraocular pressure was kept constant for 2 h the corneal thickness, radius of curvature, and the epithelial side strain gradually decreased, whereas the endothelial side strain increased. The elastic and visco‐elastic behaviour of the human cornea was found to be closely related to changes in corneal hydration. We found digital image processing useful for in vitro biomechanical studies of the

ISSN:1395-3907    

DOI:10.1111/j.1600-0420.1995.tb00004.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTThe extensibility of 10 human corneas was evaluated in vitro by measuring central epithelial side and endothelial side tangential strain induced by intraocular pressure loads ranging from 2 to 100 mmHg. Corneal normo‐hydration was attempted by immersing and perfusing the eyes with 8% Dextran 500 in isotonic saline. The relationship between corneal strain and intraocular pressure was found to be non‐linear, showing a typical stress‐stiffening behaviour. Strain changes were approximately 10% higher on the endothelial side compared with the epithelial side. This difference could be fully explained by pressure induced changes in corneal volume. Compared to previous experiments performed on swollen corneas, the stiffness of the normo‐hydrated human cornea was found to be higher. Young's modulus of elasticity for the corneal stroma was estimated to 3, 9, and 20 MPa for intraocular pressure intervals of 2–10, 10–25, and 25–100 mmHg,

ISSN:1395-3907    

DOI:10.1111/j.1600-0420.1995.tb00005.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTEnucleated human eye globes were set‐up for measurements of pressure (2–100 mmHg) induced tangential epithelial and endothelial side corneal strain, and for measurements of central corneal thickness and central radius of curvature. In one experimental group (N = 6), a shallow ablation (15–20 μm deep) removing Bowman's layer was performed in the central 7 mm diameter zone of the cornea. The fellow eye served as control (N = 6). In another experimental group (N = 6) a 70% deep keratectomy was performed in the central 7 mm diameter zone. The pressure induced central corneal strain was 5–10% higher in corneas without Bowman's layer compared with intact corneas. The epithelial side tangential corneal strain in eyes with a 70% deep keratectomy increased to twice as much as that of intact corneas, but the endothelial side strain was similar. In all groups of eyes Young's modulus of elasticity increased rapidly with the corneal stress level up to testing loads of 25 mmHg. At higher loads the degree of stress‐stiffening was smaller. The differences in average corneal strain between the 3 groups could be explained by the induced changes in central corneal thickness, as there were no statistically significant differences in stress‐normalized Young's modula of elasticity between the 3 groups. The central radius of curvature did not change significantly with increasing pressure in intact eyes or in eyes without Bowman's layer. In deep keratectomized corneas the corneal radius of curvature decreased approximately 1% when the intraocular pressure was increased from 2 to 100 mmHg. The study indicates that Bowman's layer plays no particular role for the immediate elastic response induced by pressure loading of the cornea. Due to stress‐stiffening of the corneal stroma even a 70% deep keratectomy induces only minimal elastic changes in the central corneal radius of curvature. The different strain behaviour of the epithelial and endothelial side in deep keratectomized eyes suggests that corneal shear force resistance influence the regional tangential strain in pressure loading of surgically altered

ISSN:1395-3907    

DOI:10.1111/j.1600-0420.1995.tb00006.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTThe results of transverse or combined transverse and radial keratotomy in eyes with idiopathic corneal astigmatism (N = 11), astigmatism + myopia (N = 9) or early stages of keratoconus (N = 6) are presented. The corneal astigmatism was reduced in all our patients, the absolute reduction being significantly correlated to the degree of preoperative astigmatism (p = 0.007). In the whole study group the mean relative reduction of the corneal astigmatism was 52.7%. In eyes without keratoconus the astigmatism recorded at the last follow‐up visit was very similar to that measured a few days after surgery, while greater changes occurred in the keratoconus grou

ISSN:1395-3907    

DOI:10.1111/j.1600-0420.1995.tb00007.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTSeventy‐two penetrating primary keratoplasties for herpes simplex keratitis performed from 1970 to 1993 were reviewed. Postoperative follow‐up periods ranged from 6 months to 16 years with 2 years median. Epithelial herpetic recurrence occurred in 25% of the transplants the first year and in 44% during the first 2 years. Primary allograft rejection was observed in 29% of the grafts the first year and in 46% during the first 2 years. Preoperative inflammation was a risk factor for preservation of a clear cornea (p<0.10). The degree of corneal vascularization prior to operation did not influence the survival of the grafts. The overall one‐year survival rate of a clear graft was 84% and the 2‐year survival rate was 67%. Prophylactic antiviral treatment is di

ISSN:1395-3907    

DOI:10.1111/j.1600-0420.1995.tb00008.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTThe aim of this study was to investigate the prevalence of snake‐like chromatin in the nuclei of conjunctival cells of normal elderly persons, and to compare with findings in patients with connective tissue diseases other than primary Sjögren's syndrome and in age‐matched patients with primary Sjögren's syndrome. Thirty‐nine per cent of the eyes of normal controls contained snake‐like chromatin. Snake‐like chromatin has almost never been found in young normals, and the results of this study therefore raise the question of whether age may be a contributing factor. Snake‐like chromatin was as frequent in patients with other connective tissue diseases as in patients with primary Sjögren's syndrome, and no correlation to the presence of keratoconjunctivitis sicca was found in this group. The presence of snake‐like chromatin was significantly correlated to increased cell size (N/C ratio) and low goblet cell density. A marked correlation between snake‐like chromatin and low values of break‐up time was found in normals, whereas no correlation was found to the other standa

ISSN:1395-3907    

DOI:10.1111/j.1600-0420.1995.tb00009.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTThe aim of the study was to examine for possible differences between cell cultures derived from eye with and without pseudoexfoliation. In both populations, scanning electron microscopy showed flattened epithelial cells and also spindleshaped fibroblast‐like cells. The presence of these cell types was further confirmed by immunohistochemical demonstration of cytokeratin and vimentin in the cultured cells. The cells maintained in vitro showed a linear increase in uptake of leucine during a 12‐h period. Within this period, the leucine recovered in the TCA precipitable fraction was considerably higher than the non‐bound fraction. In cultures maintained in medium with and without L‐ascorbic acid, the presence of L‐ascorbic acid significantly increase the uptake of leucine into TCA precipitable material, and to a similar extent in cultures from the two populations. In conclusion, cells derived from eyes with and without pseudoexfoliation material and maintained in vitro showed similar morphology, presence of intermediate filaments, as well as uptake of leucine under various culture c

ISSN:1395-3907    

DOI:10.1111/j.1600-0420.1995.tb00010.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY