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Biomedical subjects

W S Dixon

Publications and source records attributed to W S Dixon.

At least 19 recordsLinked to original sources
PubMed1993

Changing risk for early transplant failure: data from the Ontario Corneal Recipient Registry.

To examine the joint effects of donor, recipient and surgical characteristics on the risk of early corneal transplant failure, 73 cases of early failure (no period of clarity or clarity lasting no more than 28 days) reported to the Ontario Corneal Recipient Registry were compared with 1591 control transplants remaining clear for 6 months or more. In logistic regression models donor age was significantly associated with graft failure, with the odds of failure increasing by 24% per decade. In recipients with a history of cataract or glaucoma or with an intraocular lens in place the relative odds of failure ranged from 2.16 to 3.08. Among surgical factors, larger grafts increased risk by 45% per 0.25 mm. Grafts received before 1987 had a consistently higher risk of early failure than those received in 1987 or later. Concurrent changes in storage media, handling of donor tissue and management of recipients may have been responsible. We conclude that donor, recipient and surgical factors all contribute to the risk of early transplant failure.

Case-Control Studies↗
PubMed1988

AIDS and donor eyes.

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1982

Interlamellar refractive keratoplasty in rabbits.

The suitability and effectiveness of hydrophilic soft contact lenses and donor corneal buttons for interlamellar refractive keratoplasty were evaluated in a study with rabbits. In each experimental eye a trephined button of Bausch & Lomb Soflens (polymacon), Cooper Permalens (perfilcon A) or rabbit cornea 6.5 mm in diameter was inserted in a corneal pocket created with a lamellar dissector. Among the inserts available for long-term follow-up all five of the Soflens inserts showed "melting" (perforation and sloughing) by 3 weeks, whereas six of the seven Permalens inserts and all four of the donor corneal inserts were clear at 3 to 6 months. Myopia was induced and the corneal curvature steepened with all but the high-minus Soflens inserts. Thus, interlamellar refractive keratoplasty with soft contact lenses of high water content or lathe-cut donor corneal buttons has potential for the correction of aphakia in rabbits and may well have similar potential in humans.

Animals↗
PubMed1979

An analysis of corneal transplantation: I--graft clarity.

A retrospective review has been undertaken of the clarity results of 378 keratoplasties performed by 6 Toronto corneal surgeons between January 1970 and December 1974. Lamellar keratoplasties were included in the data related to herpes simplex only. In herpes simplex penetrating grafts gave better vision than lamellar grafts. The following factors were statistically important with respect to graft clarity: age of recipient, type of corneal disease, peroperative corneal vessels, first or subsequent graft, pre- and/or postoperative glaucoma, postoperative anterior synechiae, combined procedure, vitreous loss, previous cataract surgery, and follow-up time. The following factors were statistically unimportant with respect to graft clarity: donor age, time from death to enucleation (median 2.8 hours), time from enucleation to use (median 24 hours), sex of donor and recipient, interrupted or running suture, use of microscope, penetrating or lamellar graft in herpes simplex, postoperative astigmatism, and division of postoperative anterior synechiae. Silk (compared with nylon), larger grafts and combined procedures all increased the incidence of graft rejection. Repeat grafts were associated with more preoperative corneal vascularization.

Adolescent↗
PubMed1979

An analysis of corneal transplantation: II--postoperative astigmatism.

An analysis of 153 penetrating keratoplasties was undertaken. The same surgical technique was used in all cases. Three factors had a statistically significant effect on postoperative astigmatism, as measured by keratometry. (1) Astigmatism decreased with increasing follow-up time (P less than 0.05). (2) Vitreous loss at the time of the keratoplasty increased the amount of postoperative astigmatism (P less than 0.05). (3) Females had more postoperative astigmatism than males (P less than 0.05), but this was probably related to a tendency for females to have a greater incidence of postoperative anterior synechiae (P just greater than 0.05), and the fact that all 6 cases of vitreous loss were in females. There was an almost significant trend toward postoperative anterior synechiae being associated with increased astigmatism (P just greater than 0.05), and there was also a trend toward the division of these synechiae reducing the amount of astigmatism. Fifteen of the 153 penetrating grafts were done in cases of herpes simplex. These were compared with 11 lamellar grafts done for herpes simplex, and there was a statistically insignificant trend toward more postoperative astigmatism in penetrating grafts.

Astigmatism↗
PubMed1977

Factors in the survival of stored corneas.

In studying the survival of stored corneas we wished to know if excising the cornea was the most critical step or if one storage medium was superior to another. Rabbit corneas were excised and stored in various media at 4 degrees C or 23 degrees C for four days. The storage media included M-K medium, balanced salt solution (BSS) and 10(-8)M concentration of hydrocortisone in M-K medium and BSS. Comparisons were made by measuring acid phosphatase as an index of autolysis. Results showed a reduced amount of autolysis at 4 degrees C as compared to 23 degrees C. No statistical difference between M-K medium and BSS was seen but steroid decreased autolysis. M-K medium plus hydrocortisone seemed to be the best of the solutions studied, but removal of the cornea seemed to be the most important factor in its survival.

Acid Phosphatase↗
PubMed1976

Inhibition of pseudomonas strains in two soft contact lens soaking solutions.

Ten Pseudomonas aeruginosa and six Pseudomonas cepacia strains recently isolated from infected patients were tested for susceptibility to the antimicrobial activity of two commercially-available soft contact lens soaking solutions. No strain showed evidence of viability after two hours but survivors were found in both solutions after one-half hour and in one solution after one hour. The solution most effective in inhibiting the Pseudomonas strains contained chlorhexidine and disodium edetate but each solution was effective in reducing heavy inocula of both species within the times recommended by the manufacturers.

Chlorhexidine↗
PubMed1975

Fibrillary lines of the cornea. A clinical sign in keratoconus.

Fibrillary lines, whether in the normal cornea or in keratoconus, are faint structures which must be searched for diligently with the appropriate biomicroscopical settings, using a high magnification and oblique focal illumination of high intensity. They are unlikely to be confused with other superficial linear changes in the cornea, such as mare's tail epithelial lines, fingerprint lines and their variants, ring lines, and so on. A detailed description of these and other entities is given elsewhere (Brown and Bron, in preparation).

Cornea↗