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Biomedical subjects

R A Thoft

Publications and source records attributed to R A Thoft.

At least 91 records · Page 5Linked to original sources
PubMed1979

Ocular surface epithelium and corneal vascularization in rabbits. I. The role of wounding.

A new model for rabbit corneal vascularization, created by making a penetrating wound in corneas with epithelium of conjunctival origin, is described. Obligate resurfacing of the cornea from conjunctival epithelium usually leads to a small, but consistent peripheral superficial corneal vascularization. Subsequent penetrating wounds elicit, in 75% of cases, a marked vascular ingrowth. Normal eyes and eyes resurfaced by peripheral corneal epithelial cells do not vascularize after such wounds. The vessels are located in the anterior corneal stroma, and the regenerated epithelium has a conjunctival appearance. Although increased hydration plays a role in this vascularization, the extent of vascularization was much greater in the presence of regenerated epithelium of conjunctival origin than in the presence of regenerated epithelium of corneal origin.

Animals↗
PubMed1978

Corneal complications after closed vitrectomy through the pars plana.

A retrospective study of 150 patients who underwent closed vitrectomy through the pars plana evaluated the incidence and character of postoperative corneal complications. Corneal changes developed in 43% of patients. Thirty patients had significant corneal complications, half of which resolved with treatment. Fourteen patients had complications that necessitated corneal surgery or resulted in loss of useful vision. Diabetic patients were at greatest risk for corneal problems, particularly postoperative epithelial defects. Intraoperative lensectomy was the only other factor that increased the corneal complication rate. The importance of early recognition and therapy for corneal changes after vitrectomy becomes apparent.

Corneal Diseases↗
PubMed1978

Role of the ocular surface in destructive corneal disease.

Corneal destructive disease is related to the ocular surface in at least three ways. Firstly, the maintenance of surface integrity seems to protect the corneal stroma from ulceration. Such integrity is jeopardized if the corneal epithelial cells fail to replicate themselves, or if they fail to adhere tightly to the underlying stroma. Secondly, the ocular surface plays a role in ulceration. Elaboration of collagenolytic enzymes may occur in the abnormal ocular surface epithelial cells themselves. In addition, the surface may modulate the leucocytic response in the stroma, the leucocytes themselves being responsible for the ulceration of the stroma. Finally, the ocular surface appears to play a role in superficial vascularization of the cornea. When all of the corneal epithelium is lost, as is the case in widespread chemical injury, sluggish metabolic transformation of conjunctival cells is associated with vascularization.

Adhesiveness↗
PubMed1978

Functional competence of regenerating ocular surface epithelium.

Several aspects of the ocular surface epithelium, including its clinical appearance, its effect on the strength of underlying stromal wounds, and its healing rates, have been compared between regenerating epithelium of conjunctival and that of corneal origin in rabbits. The results showed that conjunctival epithelium could not transform completely into functionally competent corneal epithelium within 6 weeks.

Animals↗
PubMed1978

Effects of ultraviolet radiation on corneal epithelial metabolism.

Acute exposure to ultraviolet light to 257 nm wavelength produced a photokeratitis associated with characteristic metabolic alterations of corneal epithelial metabolism in rabbits. Significant increases in corneal hydration occurred simultaneously with decreased corneal epithelial glycogen content, but adenosine triphosphate content and enzyme activity of epithelial extracts were not affected despite clinical and histological damage to the corneal epithelium. The pattern and time course of ultraviolet damage to the cornea are distinctly different from those of other forms of trauma.

Animals↗
PubMed1977

Conjunctival transplantation.

A method to transplant healthy conjunctiva onto eyes with damaged ocular surface epithelium and superficial vascularization, as are often seen after chemical or thermal burns is described. Conjunctival resection and lamellar keratectomy were followed by grafting of healthy conjunctival patches. In three of five eyes with total corneal involvement, successful reepithelialization of the cornea from the conjunctiva was accompanied by improved vision and decreased vascularization. Results in two other eyes were less successful due to deep stromal vascularization.

Adolescent↗
PubMed1977

Biochemical transformation of regenerating ocular surface epithelium.

Several biochemical parameters, including glycogen levels, and the activities of hexokinase, phosphorylase, and lactate dehydrogenase have been compared in regenerating epithelium of conjunctival and corneal origin in rabbits. The study was designed to determine the extent of biochemical transformation of conjunctival into corneal epithelium completed within 6 weeks. Although histological transformation, especially in the case of the chemically damaged eyes, is not. Glycogen and lactate dehydrogenase levels remained well below normal corneal epithelial levels for the period of observation.

Animals↗
PubMed1976

Corneal epithelial changes during midterm storage.

The increased use of donor epithelium in keratoplasty for severe corneal disease has prompted an investigation of epithelial viability during midterm storage. Glycogen, ATP, and ADP have been used as indicators of the metabolic state of epithelial cells. These substances have been measured after conventional moist-chamber storage at 4 degrees C. for 1, 2, and 12 days and after immersion at 4 degrees C. in McCarey-Kaufman medium for 1, 2, and 12 days. In addition, recovery of glycogen and ATP stores has been evaluated after warming of the tissue in the storage solution to 37 degrees C. The evidence indicates that the corneal epithelium may recover these biologically important substances, despite depletion secondary to delayed cooling of donor eyes.

Adenosine Diphosphate↗
PubMed1975

Corneal epithelial preservation.

While clinical experience has demonstrated that current storage techniques are adequate for the preservation of human endothelial cells, increased use of donor epithelium in cases of severe disturbance to epithelial and stromal integrity requires a reexamination of storage effects on the epithelial layer. Measurement of human and rabbit metabolite levels in stored corneas indicates that the epithelium is maintained in a normal state only if the eye is cooled promptly. If cold storage is delayed for as little as one hour after death, glucose levels in the stroma and aqueous fall below levels known to be required for preservation of epithelial integrity. The fundamental time of interest in preservation of donor corneal tissue is in the interval between death and cooling of the eye. If prompt enucleation is not possible, ice should be applied to maintain viability of the epithelium.

Animals↗
PubMed1975

Biochmical aspects of contact lens wear.

Glycogen, adenosine triphosphate, and hydration were measured in rabbit corneal epithelium to determine whether the corneal epithelium glycogen decrease, increase in epithelial hydration, and decrease in epithelial adenosine triphosphate stores, seen as a result of contact lens wear, were secondary only to anoxia or may also have resulted from mild trauma, with no interference to oxygenation. Conventional contact lens wear, trauma, and oxygen-permeable contact lens wear caused metabolic changes, showing trauma as well as anoxia may play an important role in the corneal epithelial response to contact lens wear.

Adenosine Diphosphate↗