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Biomedical subjects

J A Davison

Publications and source records attributed to J A Davison.

At least 37 records · Page 2Linked to original sources
PubMed1993

Acute intraoperative suprachoroidal hemorrhage in capsular bag phacoemulsification.

Two cases of limited (nonexpulsive) acute intraoperative suprachoroidal hemorrhage (AISH) were identified in a consecutive series of 3,096 cataract surgeries accomplished by capsular bag phacoemulsification--an incidence of 0.06%. This is lower than that reported by me in 1986 when I was using iris plane phacoemulsification (0.81%). I believe the reduction is the result of decreased anatomical distortion from reducing the number and amplitude of intraocular pressure swings experienced by the globe during surgery. The pressure swings result from technique-mandated oscillations in infusion and aspiration dynamics, which are greater in number and amplitude in the iris plane technique.

Acute Disease↗
PubMed1993

Features of a modern retrobulbar anesthetic injection for cataract surgery.

No significant complications including retrobulbar orbital hemorrhage after retrobulbar anesthetic block were identified in a retrospective review of 3,415 consecutive cataract surgical cases blocked and performed by one surgeon. The technique for retrobulbar injections using a disposable retrobulbar needle is described in detail. All injections were deliberately retrobulbar, directed toward the inferior temporal muscle cone, and were given immediately prior to cataract surgery by the surgeon.

Anesthesia, Local↗
PubMed1993

The "blind alley". Its significance for evolutionary theory.

Several scientists have apparently independently used the term "Blind Alley" to indicate that major evolutionary change has ceased. The failure to observe speciation through selection would indicate that obligatory sexual reproduction is incapable of producing progressive evolution. Favoring this conclusion is the evidence that sex determination has independently evolved and may be further correlated with the equally nonhomologous evolution of contemporary gametic sources in the same animal groups. To incorporate these facts into a meaningful theory demands the postulate of a presexual mode of reproduction which has been suggested as identical with the first meiotic division. A hypothetical scenario for macroevolution is presented.

Animals↗
PubMed1991

Modified insertion technique for the SI-18NB intraocular lens.

The 14 mm polypropylene haptic structure of the AMO SI-18NB is extremely soft for safe small incision insertion. The material has a tendency to lose its memory and experience a permanent alteration in shape if it is bent too much during implantation. An alternative surgical technique that spares extreme haptic distortion and improves centration of the intraocular lens optic is presented.

Cataract Extraction↗
PubMed1990

Hybrid nuclear dissection technique for capsular bag phacoemulsification.

A bimanual phacoemulsification technique for dissecting and removing the firm lens nucleus is described. The technique is a surgical hybrid that combines concepts developed by several surgeons. Bimanual posterior and peripheral nuclear bowl fiber separation (nuclear fracture) has been incorporated into the anatomic dissection of the lens within the capsular bag. This dissection is accomplished with the 45-degree tip on separated nuclear components in situ after capsulorhexis. Combining the best features of various techniques permits this hybrid method to be applied to firm cataracts by most surgeons currently performing phacoemulsification.

Cataract Extraction↗
PubMed1990

Capsular bag distension after endophacoemulsification and posterior chamber intraocular lens implantation.

Six cases of capsular bag distension after capsulorhexis, endophacoemulsification, and posterior chamber intraocular lens (IOL) implantation are presented. Five cases had prominent posterior subcapsular cataracts preoperatively. In three cases, the anterior chamber depths were shallower and the apparent refractive errors were more myopic than normal after surgery. All six cases exhibited an apparent early complete sealing of the anterior capsular remnant against the anterior IOL optic. In each case, the capsular bag contained moderate particulate debris and flare while the adjacent vitreous and anterior chambers were clear. I suspect the particles are epithelial cell and cortical debris suspended in a fluid comprising lens epithelial protein, cellular breakdown products, balanced salt solution, and water. Five cases have received no specific treatment. In one case, a neodymium:YAG laser anterior capsulotomy allowed a forward egress of fluid from the distended capsular bag and a return to normal pseudophakic anatomy.

Aged↗
PubMed1989

Bimodal capsular bag phacoemulsification: a serial cutting and suction ultrasonic nuclear dissection technique.

A technique for emulsifying the lens nucleus within the capsular bag is presented. The circular continuous tear anterior capsulotomy (capsulorhexis) and nucleus hydrodissection, which are components of the technique, are identified. The concept of isolated cutting and suction as independent actions of the 45-degree ultrasonic phaco-emulsification tip is discussed. The two actions are achieved by alternating the orientation and action of the 45-degree ultrasonic tip in a multiple rotation nuclear dissection technique. The nucleus is collapsed and drawn centrally without aspirating nuclear material while the tip's aperture is near the lens capsule. This technique prevents the ultrasonic tip aperture from bursting through the peripheral nuclear shell and thus reduces the risk of capsular aspiration and vitreous loss.

Cataract Extraction↗
PubMed1989

Transverse astigmatic keratotomy combined with phacoemulsification and intraocular lens implantation.

Transverse astigmatic keratotomy is a surgical technique to correct preoperative corneal astigmatism during cataract surgery. The operative technique is described and the results of my first 40 cases are reviewed. The average keratometric astigmatism for this group before surgery was 2.6 dipoters (D). The average reduction in astigmatism was 1.5 D, which yielded a final residual average astigmatism of 1.1 D after surgery. Cases of substantial astigmatism showed the most improvement. Less improvement was seen in cases of minimal preoperative astigmatism. No increase in net keratometric astigmatism was seen in any of the eyes studied. Minor complications were limited to several small corneal abrasions created by the front-cutting diamond blade and one late temporary wound dehiscence. The only serious complication was one case of corneal macroperforation. Recommendations for handling this complication and future high astigmatism cases are given.

Adult↗
PubMed1989

Primary malignant melanoma of the lung.

Primary malignant melanoma of the lung is a rare neoplasm; to date, there have been approximately 20 cases reported in the literature. Extensive clinical and postmortem examinations are necessary to exclude the possibility that the lung tumor does not represent a metastasis from an occult cutaneous or extracutaneous melanoma. We present a case of a 62-yr-old man who appears to have had a primary melanoma of the left upper lobe of the lung. The literature on primary pulmonary melanoma is also reviewed.

Humans↗
PubMed1988

Retinal tears and detachments after extracapsular cataract surgery.

A review of 3,120 consecutive cases of extracapsular cataract extraction revealed a retinal detachment incidence of 0.8% and a retinal tear incidence of 0.9%. Approximately 85% of all tears and detachments occurred within the first three years of cataract surgery. Analysis of the retinal detachment group identified several risk factors. These included young age, male sex, axial length greater than 25 mm, primary posterior capsulotomy, and previous retinal surgery in the fellow eye. In the retinal tear group, the risk factors were young age and previous retinal surgery in the fellow eye. Visual results were excellent with an average of one line of acuity lost after successful macula-on and macula-off detachment surgery and no significant change after retinal tear repair. Despite multiple surgeries, the retinas in two detachments were lost to proliferative vitreoretinopathy.

Aged↗
PubMed1988

A short haptic diameter modified J-loop intraocular lens for improved capsular bag performance.

The laboratory and clinical characteristics of a modified J-loop intraocular lens (IOL) are presented. The lens features a 6 mm polymethylmethacrylate optic with uniplanar polypropylene loops of a 12 mm overall haptic diameter. The haptic design has a low resistance to compression at all diameters down to 9 mm. The relationship of the haptic configuration to the architecture of the capsular bag facilitates easy capsular bag implantation and consistent IOL centration in eyes with small and moderate capsular bag diameters. Three hundred fourteen lenses have been implanted over a one year period with no instance of asymmetric capsular bag-ciliary sulcus IOL placement, optic decentration, or pupillary capture.

Humans↗
PubMed1987

Vitrectomy and fluid infusion in the treatment of delayed suprachoroidal hemorrhage after combined cataract and glaucoma filtration surgery.

I report the successful treatment of one case of massive, delayed suprachoroidal hemorrhage that occurred after combined intracapsular cataract extraction and trabeculectomy. Significant vitreous incarceration in the filtration site and consequent vitreoretinal traction were present so that a limbal approach anterior vitrectomy was necessary before choroidal drainage could be accomplished safely. An infusion of balanced salt solution through a limbal infusion cannula was employed during vitrectomy and also during drainage of suprachoroidal blood. The simultaneous intravitreal infusion helped to create an efficient, controlled choroidal drainage procedure. In addition to relieving vitreoretinal traction, this technique helps prevent the periods of extreme hypotony experienced when choroidal drainage and anterior chamber reformation are accomplished serially in step-wise fashion. This use of this method also obviates the compromised view of the peripheral retina which occurs when air is introduced into the vitreous cavity.

Aged↗
PubMed1986

Analysis of capsular bag defects and intraocular lens positions for consistent centration.

Radial anterior capsular tears frequently occur in posterior-chamber iris-plane phacoemulsification cases. These tears extend to the capsular bag equator and can allow the knee of an in-the-bag posterior chamber intraocular lens (IOL) to unfold a smaller anterior capsular remnant. This unfolding can allow the knee of the IOL loop to extend beyond the capsular equator, leading to IOL decentration. Typical anterior capsular radial tear configurations along with guidelines for IOL design selection and orientation after recognition of these tears are presented. Proper IOL centration was achieved in 255 of 262 patients (97%) in a study observing these guidelines.

Cataract Extraction↗