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Biomedical subjects

K R Kenyon

Publications and source records attributed to K R Kenyon.

At least 91 records · Page 5Linked to original sources
PubMed1988

Microbial keratitis associated with contaminated ocular medications.

We studied seven cases of severe gram-negative microbial keratitis associated with the use of contaminated topical ocular medications. Five cases involved Pseudomonas aeruginosa, one involved Serratia marcescens, and one involved Proteus mirabilis. In each case the same organism was cultured from corneal scrapings and from the medication. Either prednisolone acetate (one case) or timolol maleate (seven cases) was implicated in all instances.

Administration, Topical↗
PubMed1988

Effects of gentamicin on healing of transdifferentiating conjunctival epithelium in rabbit eyes.

We examined the effects of commercially prepared gentamicin, a wide-spectrum topical antibiotic, on the healing of epithelial defects of the rabbit cornea. Abrasions were created by: (1) removing the corneal epithelium and 3 mm of the conjunctival epithelium (Group 1); and (2) producing the same initial trauma and subsequently removing the central 8 mm of epithelium 28 days after initial healing (Group 2). The complete healing of the large corneal and conjunctival epithelial defects was not delayed when gentamicin solution was used four times a day (Group 1). When the healed epithelium was reinjured while transdifferentiating from conjunctival to corneal epithelium (day 28, Group 2), treatment with the gentamicin solution and its vehicle, both containing benzalkonium chloride, delayed epithelial healing significantly compared with treatment with saline (P less than .01).

Administration, Topical↗
PubMed1988

Noninvasive metabolic analysis of preserved rabbit cornea.

With the method of corneal redox fluorometry, the autofluorescence of reduced pyridine nucleotides (PN) and oxidized flavoproteins (Fp) in rabbit corneal endothelium was measured as a function of storage time in McCarey-Kaufman (MK) medium and K-Sol medium. Measurements were started immediately after preparation of the corneal button, and the corneas were followed up for up to three weeks of storage. In both media, the PN/Fp ratio of the endothelium initially increased slightly in the first or second day and then began to decrease toward a level lower than baseline. This initial increase is possibly a result of an adaptive mechanism. The PN/Fp ratio maintained itself in the range of baseline values up to one week in MK medium but not in K-Sol medium. With scanning electron microscopy, the surface of the membrane and cell border were maintained for a three-week preservation period, and no apparent differences were found between the corneas stored in the two media. With transmission electron microscopy, the intracellular organelles appeared almost normal through one week of preservation in corneas stored in either media. During weeks 2 and 3, however, intracellular edema with increased endothelial thickness became prominent in the corneas stored in both media. Although no visual difference in the morphological features of the endothelium was apparent between corneas stored in either medium, computer-assisted morphometric analysis showed a statistically significant increase in the coefficient of variation of mean cell area for the corneas preserved in K-Sol medium but not for those preserved in MK medium.

Animals↗
PubMed1988

Microbial keratitis complicating penetrating keratoplasty.

A retrospective review of 68 consecutive episodes of microbial keratitis complicating 66 penetrating keratoplasties (PKs) showed major risk associations: suture-related problems (50%), contact lens wear (26%), previous herpes simplex infection (15%), graft failure (15%), and persistent epithelial defects (15%). Topical steroid (85%) and antibiotic (59%) usage were common iatrogenic factors. Half the infections occurred more than 1 year after grafting. Bacterial infections involving gram-positive organisms (59%) predominated, except for patients with extended-wear hydrophilic contact lenses, which usually involved gram-negative bacilli. The incidence of fungal infections (6%) was relatively low. Recommendations to minimize microbial keratitis include prompt attention to exposed, broken, or loose sutures, and preventive and therapeutic management of epithelial defects. The inadequacy of low-dose antibiotics in precluding microbial infection in many cases and the propensity to develop infections with resistant organisms suggest that guidelines for using postoperative and prophylactic topical antibiotics require reevaluation.

Corneal Transplantation↗
PubMed1988

Results of anterior segment reconstruction for aphakic and pseudophakic corneal edema.

The authors studied prospectively 59 eyes with corneal edema after cataract surgery that required reconstructive surgery; penetrating keratoplasty in 59 (100%), anterior vitrectomy in 42 (71%), intraocular lens removal or exchange in 33 (56%), gonioplasty in 32 (54%), and iridoplasty in 30 (51%). With an average follow-up of 9.9 months, the corneal transplant was clear in 56 eyes (95%). The corrected visual acuity was improved in 49 eyes (83%) and was the same in seven eyes (12%). Intraocular pressure was less than or equal to 21 mmHg in 47 eyes (80%) and 22 to 29 mmHg in nine eyes (15%). The peripheral anterior synechiae score was the same or improved in 56 eyes (95%). Cystoid macular edema was absent to mild in 52 eyes (88%). Anterior segment reconstruction improved both anatomic integrity and visual acuity of most eyes without increasing complications.

Aged↗
PubMed1988

Episodic conjunctival inflammation after Stevens-Johnson syndrome.

The authors studied the histopathologic, ultrastructural, and immunopathologic characteristics of conjunctiva from patients with Stevens-Johnson syndrome (SJS). A small subset of SJS patients with recurrent conjunctival inflammation unassociated with external factors such as lid margin keratinization, sicca syndrome, trichiasis, or entropion was identified. The ultrastructural and immunopathologic characteristics of the conjunctiva from these patients were distinctly different from those of the conjunctiva from SJS patients without recurrent conjunctivitis, and suggested an active, immunologically mediated inflammation. Vasculitis or perivasculitis, immunoreactant deposition in vessel walls, vascular basement membrane disruption, thickening, and reduplication, and a preponderance of helper T-lymphocytes, macrophages, and Langerhans' cells were the notable distinguishing features in those patients with recurrent conjunctival inflammation. This rare clinical syndrome may represent the ocular counterpart to recurrent dermal or oral mucosal erythema multiforme.

Adolescent↗
PubMed1988

Epithelial abnormalities and sterile ulceration of epikeratoplasty grafts.

Six epikeratoplasty (EKP) specimens were obtained 1 to 10 months after refractive keratoplasty for aphakia (2 cases), keratoconus (1 case), and myopia (3 cases). The EKP grafts were removed because of postoperative complications such as delayed reepithelialization, lenticule edema, stromal ulceration, graft opacification, and inability to improve vision in a clear graft. The extent of epithelial abnormalities was associated directly with the severity of structural changes in the underlying basal lamina, Bowman's layer, and stroma as evidenced by electron microscopic examination. Epithelial defects were associated with varying degrees of sterile stromal ulceration of the underlying lenticule. In one case, an extensive full-thickness ulceration of the EKP button occurred in the area of persistent epithelial defects and was associated with a major ulceration of the underlying recipient's corneal stroma. Removing the failing button halted the ulcerative process with prompt reepithelialization. In the absence of inflammation and infection, the persistent epithelial abnormalities and defects leading to proteolytic degradation of the EKP buttons constitute an important mechanism of graft failure with major visual consequences and possibly irreversible ocular damage.

Adult↗
PubMed1988

Evidence for a feline reservoir for dysgonic fermenter 2 keratitis.

A 78-year-old female developed microbial keratitis from which corneal scrapings grew dysgonic fermenter 2. The infection initially responded poorly to a combination of topical antibiotics and corticosteroids but healed with intensive antibiotic therapy. There was no systemic predisposition to infection, and only feline exposure had occurred. Close association with a cat probably contaminated the eye.

Aged↗
PubMed1988

Increased cytochrome oxidase activity in alkali-burned corneas.

Cytochrome oxidase (CO) activity on alkali-burned rabbit corneas was investigated histochemically to determine the metabolic change in inflamed corneas during wound healing. Cryostat sections of chemically burned and mechanically scraped corneas were stained for CO activity, which is regarded as an index of metabolic activity. Following chemical injury, positive CO activity was detected initially in the vascular endothelial cells of limbal blood vessels. Numerous active polymorphonuclear leukocytes (PMNs) and monocytes were found intravascularly and perivascularly. Fibroblasts that appeared at the wound site exhibited marked CO activity around the limbus. Over a period of 13 days, PMNs gradually invaded the central cornea, followed by fibroblasts of high metabolic activity. The areas of PMN infiltration were the same areas in which fibroblasts showed intense staining, suggesting that a PMN-derived mediator or secondary products might affect the activation of fibroblasts. Epithelial resurfacing was delayed in the chemically burned corneas, although reepithelialization was completed within two to three days in the scraped corneas. Limbal epithelial cells, which recently were suggested as the source of epithelial renewal, showed a remarkable increase of metabolic activity in response to chemical inflammatory stimulation, whereas those in the scraped model did not. This suggests that epithelial cell renewal at the limbus was accelerated in the presence of disturbed reepithelialization.

Alkalies↗
PubMed1988

Plasminogen activator activity in vitamin A-deficient rat corneas.

Plasminogen activator (PA) activity during epithelial wound healing in vitamin A-deficient rats was investigated to determine whether a relationship exists between corneal defect formation and PA activity. Uniform, central 3 mm diameter corneal epithelial wounds were made by scalpel debridement in vitamin A-deficient and in pair-fed control rats. Cryostat sections of such corneas, taken at various times post-scrape, were overlaid with fibrin films containing plasminogen to examine the distribution of PA activity; and antibodies to tissue plasminogen activator (tPA) or to urokinase-like activator (uPA) were incorporated into the films so that the immunochemical natures of detected PA activities could be determined. Corneas from pair-fed controls showed tPA-dependent lysis in association with the regenerating epithelium as well as in the defect region during epithelial wound healing. Corneas from vitamin A-deficient rats also demonstrated tPA activity in association with corneal epithelium post-scrape but showed no detectable tPA activity in the defect region. Histological examination of the vitamin A-deficient corneas demonstrated that a pseudomembrane composed of PMNs, cell debris, and fibrinous exudate had formed on the scrape-debrided stromal surface. The migrating edge of regenerating epithelium overlaid this membrane and was, therefore, not in contact with the stromal surface. The formation of the pseudomembrane, which delays reepithelialization, might have resulted from the absence of PA activity in the defect region. Both excessive and inadequate levels of PA activity may result in impaired epithelial wound healing.

Animals↗
PubMed1988

Tear film osmolarity and ocular surface disease in two rabbit models for keratoconjunctivitis sicca.

We report the natural history of keratoconjunctivitis sicca (KCS) in two rabbit models. The first one (full KCS model) was created by closing the lacrimal gland excretory duct, and removing the nictitating membrane and harderian gland. We created the second one (lacrimal gland duct only [LGDO]-KCS model) by closing the lacrimal gland excretory duct. Although tear film osmolarity was abnormally high in both models, it was higher in the full KCS model. Decreases in corneal epithelial glycogen and in conjunctival goblet cell density, and morphological abnormalities of the conjunctiva correlated with increases in tear film osmolarity and duration of disease.

Animals↗
PubMed1988

Morphogenesis of rat conjunctival goblet cells.

Conjunctival flat-mount preparations stained with alcian blue and PAS were used to study the development and mucin differentiation of conjunctival goblet cells in Sprague-Dawley rats from newborn to 17 months of age. In the neonatal conjunctiva, only single goblet cells containing primarily acidic mucin (alcian-blue positive) were noted. With the increase of age, the rat conjunctival goblet cells were in clusters with heterogeneous mucin contents, which differ from the nonclustered, single goblet cells of human and rabbit conjunctiva. Topographical analysis revealed that the density and size of goblet cell clusters were highest in the forniceal zone, with gradual decrease towards the bulbar and orbital zones. and were absent in the limbal and tarsal conjunctiva in all ages. The goblet cells in the forniceal zone contained predominantly acidic mucin in all ages, except that selective loss of acidic mucin with vacuolation of the clusters was noted in the 17-month-old rats. Despite the fact that the size of the goblet cell clusters increased with age, the overall density of the clusters remained rather constant throughout the ages studied. These results indicate that each goblet cell cluster may derive from a single progenitor (stem) cell and represents a glandular primordium, and that goblet cell development and mucin differentiation are modulated by the aging process.

Animals↗
PubMed1988

Effects of air and irrigating solutions on the corneal endothelium.

It is well established that the corneal endothelium reflects the trauma it experiences by changing its morphological appearance. We have studied the effect of mild trauma to the rabbit endothelium by replacing the aqueous humor with air. After either 2 or 4 h, the air was removed and then replaced with either physiological saline or balanced salt solution (BSS). Specular microscopy was then performed for 1 week to observe endothelial changes. Various transient morphological changes observed during this period included many nonhexagonal cells, enlarged cells, and clusters of small cells. The changes produced were more dramatic for the saline replacement group than the BSS replacement group, indicating that the recovery process of the endothelium following this mild trauma depends on the material used to replace the air. The air appears to sensitize the endothelium to subsequent insult. This model can perhaps be used to evaluate the relative safety of the various solutions that are used in the anterior chamber during ocular surgery.

Air↗
PubMed1987

Pseudomonas corneoscleritis.

We evaluated three cases of Pseudomonas aeruginosa corneoscleritis, one associated with the use of contaminated eyedrops; another in an elderly, debilitated patient; and the third in a patient who had previously undergone penetrating keratoplasty. In the first two cases, control of the infection was achieved by intensive antibiotic therapy alone. The third case required evisceration of the eye following spontaneous perforation at the site of scleral involvement. Histopathologic findings showed persistence of the organism in the sclera despite intensive antibiotic therapy for six days.

Aged↗
PubMed1987

Pseudomonas attachment to new hydrogel contact lenses.

The adhesion of two strains of Pseudomonas aeruginosa to unworn hydrogel contact lenses (CLs) was studied by scanning electron microscopy. New daily-wear polymacon lenses (38.6% water content) and extended-wear lidofilcon A lenses (70% water content) were exposed to a suspension of 10(8) colony-forming units per milliliter of P aeruginosa for 2, 5, 15, 30, and 60 minutes. Increasing numbers of bacteria were found to attach to the lenses with time, and no significant differences between CL types were demonstrated. Attachment was considered to be irreversible since washing did not remove the bacteria. We conclude that P aeruginosa can actively attach to new, unworn hydrogel CLs.

Bacterial Adhesion↗
PubMed1987

Ocular involvement associated with chronic Epstein-Barr virus disease.

Ocular involvement with acute Epstein-Barr virus infection is usually limited to a transient follicular conjunctivitis, although other lesions have been reported. Chronic Epstein-Barr virus infection has recently gained attention, but ocular manifestations have not been emphasized. We describe three patients with chronic infection with prominent ocular involvement. Bilateral uveitis was noted in all patients, ranging from an anterior uveitis that was responsive to steroids to a severe panuveitis with vitritis, cataract, optic disc swelling, and macular edema. In one patient, topical acyclovir ointment resulted in a substantial decrease in the inflammatory reaction when added to systemic acyclovir therapy. Another patient displayed a keratitis that resolved with topical steroid therapy. Cataract and vitreous surgery were also beneficial in the management of these patients.

Acyclovir↗