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Biomedical subjects

D Hickingbotham

Publications and source records attributed to D Hickingbotham.

18 recordsLinked to original sources
PubMed1991

In vitro videographic comparison of argon and Nd:YAG laser iridotomy.

We used an in vitro technique with high-magnification video recording to evaluate from the posterior side of the iris the immediate sequence of events during argon and Nd:YAG laser peripheral iridotomy. The observed effects differed strikingly. The argon laser caused a gradual mounding up of iris pigment epithelium with each successive energy application before final penetration. This effect was reduced but not eliminated with higher power levels. The Nd:YAG laser caused complete disruption and dispersal of the pigment epithelium with a single pulse of energy. Additionally, a multiple focal point configuration of the Nd:YAG laser was observed to produce a significantly larger iridotomy than a single focal point configuration for comparable energy settings. These observations may in part explain the observed clinical advantage of the Nd:YAG laser over the argon laser for creation of a patent iridotomy.

Humans↗
PubMed1990

Refinements in microinstrumentation for vitreous surgery.

We developed a series of 25-gauge (0.5 mm) microinstruments for vitreous surgery, including a 25-gauge vitreous cutter, 25-gauge microscissors for limited reuse, and a vitreous membrane dissector. Clinical experience with these instruments in more than 20 cases of advanced proliferative vitreoretinopathy, retinopathy of prematurity, and diabetic retinopathy indicates that these instruments facilitate delicate vitreoretinal dissections, particularly in the vitreous base and when fibrovascular tissues are closely adherent to the retina. Because of their smaller size, the microinstruments are more precise in their cutting capabilities than other instruments.

Equipment Design↗
PubMed1990

The effect of oxygen on corneal neovascularization.

Since tissue oxygen levels are believed to play a pivotal role in new vessel growth in several situations, we studied the effect of several oxygen concentrations (0, 10, 21, 50, 75, or 100%) on corneal vascularization induced in the rat by chemical cautery. We achieved this by perfusing known concentrations of oxygen through goggles fitted over both eyes of the rat after corneal cauterization. Neovascularization was measured in flat corneal preparations with India ink-filled vessels 4 days postcautery using computerized image analysis. The angiogenic response of rats whose eyes were continuously exposed to 0-75% oxygen were not significantly different from each other. The mean response in corneas exposed to 100% oxygen was 10-21% lower than all of the other groups, and this difference was statistically significant when compared to oxygen concentrations of 0, 21 and 75%. The reason for the inhibitory effect of 100% oxygen remains to be determined, but it may represent a toxic effect of oxygen free radicals on the vascular endothelium.

Animals↗
PubMed1989

Accuracy of topographic measurements with the Optic Nerve Head Analyzer.

We used a plastic model of the human eye to study the accuracy with which the Optic Nerve Head Analyzer estimates the surface contour and two-dimensional size of the optic nerve head. Computer-generated contour lines were similar to the actual cross-sectional contour of plastic cups as photographed by scanning electron microscopy. The magnification error of computer-measured cup diameters was inversely related to the axial length of the model. The slope of this relationship was reduced with the use of either refraction or axial length as a correction factor for magnification error. Of the two correction factors, the former provided the closest estimation of the known diameters in the phakic model, while the latter performed better in the aphakic model.

Computer Graphics↗
PubMed1989

Temporary iris fixation with a micro-iris retractor.

We developed a new micro-iris retractor to achieve temporary intraoperative pupillary mydriasis in selected eyes undergoing pars plana vitreous surgery. The micro-iris retractor and its use were compared with previous methods for obtaining adequate intraoperative pupillary dilation.

Dilatation↗
PubMed1989

A new retractable micromagnet for intraocular foreign body removal.

We have developed a new, self-contained, small-gauge, permanent, rare-earth magnet for use in conjunction with pars plana vitrectomy in the treatment of selected magnetic intraocular foreign bodies. This magnet allows controlled grasping and releasing of the foreign body by the surgeon, thus increasing surgical control in magnetic intraocular foreign body removal.

Equipment Design↗
PubMed1986

Experimental transvitreal cyanoacrylate retinopexy.

We used an experimental rabbit model of rhegmatogenous retinal detachment to compare the onset, quality, and duration of chorioretinal adhesions obtained by transvitreal application of N-butyl-2-cyanoacrylate mixed with iophendylate with those obtained by transscleral retinal cryopexy. The chorioretinal adhesions produced by the cyanoacrylate tissue adhesive were immediate in onset, stronger, and long lasting.

Animals↗
PubMed1985

The three-port microcannular system for closed vitrectomy.

Microcannulas used during vitreous surgery protect the entry site, avoid vitreous base damage, and allow easy exchange of 20- and 19-gauge (0.9- and 1-mm) instruments. The use of three cannulas of equal size permits interchangeability of all instruments. A locking mechanism allows attachment and exchange of various infusion lines (balanced salt solution, gas, and oil). Temporary plugging of the cannula is possible. Selection of 1 mm as a standard diameter for all cannulas make multiple-function instruments feasible.

Catheterization↗
PubMed1985

Retinal tacks.

An improved retinal tack and applicator can be used to fix the retina to the wall of the eye mechanically. The system consists of a small (1 X 2.7 mm) stainless steel tack with a blade-like tip and a forked applicator that can grasp the tack securely from any position. Two eyes with complex detachments with fixed rolled retinas could not have been repaired without the help of retinal tacks. The advantages of the retinal tack system over other methods include ease of handling, insertion, and removal.

Adult↗
PubMed1985

Intraocular cyclophotocoagulation. Histopathologic evaluation in primates.

Intraocular cyclophotocoagulation with endoscopic visualization, following lensectomy and anterior vitrectomy, was performed on 14 eyes of eight rhesus monkeys. Two eyes received lensectomy and vitrectomy without laser treatment. One eye of each animal was studied one to eight months postoperatively, while the contralateral eyes were enucleated for study immediately after surgery. Histopathologic changes in the treated ciliary processes immediately after therapy included variable degrees of disruption in the epithelial layers and bleeding, while the late changes ranged from partial disruption of the epithelium and intrastromal pigment clumping to replacement of the processes by a fibrotic mass. The degree of these structural changes correlated reasonably well with the level of laser energy used and especially with the immediate, visible tissue alteration. These data may be useful in the development of clinical protocol for intraocular cyclophotocoagulation.

Animals↗
PubMed1977

A portable system for external photography.

A portable system for external photography combines a focusing lamp and movable flash unit with a wide focusing range. The system is arranged to operate from a single two-position trigger and may be hand-held or mounted on a slitlamp stand. It is designed for use in general ophthalmology in a multilaned office practice or bedside use in a hospital situation.

Ophthalmology↗