Search PubMed⌕ Search

Biomedical subjects

J A Davison

Publications and source records attributed to J A Davison.

47 records · Page 3Linked to original sources
PubMed1986

Acute intraoperative suprachoroidal hemorrhage in extracapsular cataract surgery.

The incidence of acute intraoperative suprachoroidal hemorrhage (AISH) was studied in 2,839 consecutive extracapsular cataract extraction cases operated by nucleus expression and phacoemulsification. Twenty-five eyes (0.9%) were identified with this complication. Acute intraoperative suprachoroidal hemorrhage was defined as the acute accumulation of fluid in the suprachoroidal space which resulted from a presumed suprachoroidal hemorrhage at the time of surgery. Preoperative risk factors for the development of this complication included advanced age and the presence of glaucoma. Sex, controlled hypertension, long axial length, and method of cataract removal could not be identified as significant risk factors. Recognition of the early signs of AISH and initiation of rapid wound closure followed by the completion of secondary operations performed the next day helped to meet the surgical objective and to provide excellent visual results, with 21 eyes (84%) having a visual acuity of 20/30 or better.

Acute Disease↗
PubMed1986

Sodium hyaluronate exchange in posterior chamber lens implantation.

A method for replacing sodium hyaluronate with balanced salt solution (BSS) at the end of cataract surgery is described. The technique is performed by using an automated irrigation/aspiration machine and three substance exchanges: sodium hyaluronate for BSS, BSS for air, and air for BSS. The objective of the technique is to protect the corneal endothelium from intraocular-lens-induced trauma and to keep the lens in the bag. This is accomplished by preventing even momentary anterior chamber shallowing through the maintenance of a relatively constant anterior chamber volume during the exchanges.

Humans↗
PubMed1984

Endothelial cell loss during the transition from nucleus expression to posterior chamber-iris plane phacoemulsification.

Corneal endothelial cell loss and other complications were analyzed in a series of 344 consecutive extracapsular cataract extraction patients operated on during one year. The cases analyzed represent the first phacoemulsification extractions performed by this surgeon and were compared with those of an already familiar technique, nucleus expression. No significant difference in overall endothelial cell loss (10.7% cell loss for nucleus expression and 10.0% cell loss for phacoemulsification) was found. Analysis of all other complications revealed no significant difference between these two groups.

Cataract Extraction↗
PubMed1983

A comparison of the effects of phacoemulsification and nucleus expression on endothelial cell density.

A series of patients undergoing extracapsular cataract extraction by phacoemulsification (1,126) or nucleus expression (632) were studied to evaluate the relative effects of emulsification time, irrigating volume, and surgical technique on endothelial cell density. The collective data revealed a higher cell loss with phacoemulsification (15%) than with nucleus expression (12%). Patients over 69.5 years appeared to be more vulnerable to the effects of phacoemulsification than those below 69.5 years. Although the data were subjected to combinations and permutations of age, sex, time, and volume, no direct correlation between emulsification time and/or irrigating volume and endothelial cell loss was shown. When data sets for individual surgeons were analyzed, the most striking difference was between the endothelial effect of anterior chamber phacoemulsification (26% average reduction) and that of posterior chamber phacoemulsification (13% average reduction).

Age Factors↗
PubMed1982

The effects of oversize donor buttons on postoperative intraocular pressure and corneal curvature in aphakic penetrating keratoplasty.

Forty-one consecutive aphakic corneal transplants performed by the same surgeon were studied in order to determine the effects on intraocular pressure and corneal curvature of using 8.0-mm donor buttons in 7.5-mm recipient openings. One half of the grafts had oversize donor buttons, and all were followed for 13 months. The intraocular pressure in the oversize donor group was statistically significantly less during the first five days after keratoplasty, but not subsequently. Eliminating eyes with preoperative glaucoma, more transplants in the same size donor group (P = 0.08) needed glaucoma therapy 13 months after operation. The anterior corneal curvature (mean keratometry reading) was statistically significantly greater in the oversize donor group throughout the postoperative period. Concurrently, the oversize donor group was less hyperopic after all sutures were removed. There was no difference in keratometric astigmatism or corneal thickness between the two groups. Thus, the use of 0.5-mm oversize donor tissue in aphakic corneal transplants reduced the intraocular pressure and increased the central corneal curvature after keratoplasty.

Aphakia↗
PubMed1981

Results of penetrating keratoplasty using a double running suture technique.

The results of 84 consecutive penetrating keratoplasties in which a double running suture technique was used are presented herein. The second suture was smaller, looser, and more superficial than the first, causing less corneal distortion, thus allowing better visual acuity. The two sutures were removed at two and 12 months after transplantation. The visual acuities attained were almost as good at three months as at 13 months, and the graft curvature did not change notably from three to 12 months after keratoplasty. There were only two instances of postoperative wound dehiscence (2.4%). Thus, the double running suture technique allowed early visual rehabilitation without increasing the risk of corneal dehiscence from early suture removal.

Cornea↗
PubMed1976

Adenine nucleotide pool and energy charge during growth of a tyrothricin-producing strain of Bacillus brevis.

The adenine nucleotide levels and derived energy charge value of a tyrothricin-producing strain of Bacillus brevis under aerobic conditions were in good agreement with published values for other bacteria. When growing cultures of B. brevis underwent a transition from aerobic to anaerobic conditions, cyclic variations in the level of adenine nucleotides were observed and the energy charge value oxcillated between 0.87 and 0.70. The significance of these changes is considered in relation to antibiotic production as a possible regulatory mechanism in energy metabolism. It is concluded that tyrothricin is not directly involved in the observed changes in energy charge value.

Adenine Nucleotides↗
PubMedDate not supplied

Ontogeny, phylogeny and the origin of biological information.

Accepting the evidence that evolution is largely finished and that sexual reproduction is incapable of supporting macroevolution, indicates that macroevolutionary changes were produced presexually through the cytological events associated with the first meiotic division. This reproductive mode is ideally suited to the production of new structural rearrangements of preexisting genetic information in instantaneous homozygous form. These new arrangements (position effects) produce new and discrete species. Thus, speciation results not from new genetic information, but rather from information already present (preformed). The several parallels that exist between epigenesis and preformation in both ontogeny (development) and phylogeny (evolution) are discussed. I propose that both of these phenomena have proceeded through the selective activation (derepression) of an enormous potential supply of information already present at the onset of each of these biological phenomena. Acceptance of these possibilities can serve to liberate us in our quest for the ultimate truth concerning these two closely related phenomena.

Animals↗