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Biomedical subjects

R L Lindstrom

Publications and source records attributed to R L Lindstrom.

At least 163 records · Page 9Linked to original sources
PubMed1976

Chiba percutaneous transhepatic cholangiography. A valuable method for visualizing the nondilated biliary tract.

Percutaneous transhepatic cholangiography with the Chiba needle has had remarkable results in cannulating small bile ducts. We have roentgenographically visualized a nondilated biliary system in the first five out of seven cases attempted. Including our series, there have been 71 successful Chiba studies in 107 nondilated or presumed normal biliary tracts with only one questionable major complication. The technique is simple to learn, particularly in comparison with endoscopic retrograde cholangiography. Since the incidence of complications is low, surgical standby should seldom be necessary. The value of the Chiba percutaneous transhepatic cholangiogram is described via four unusual case reports.

Adult↗
PubMedDate not supplied

Unsuspected infectious keratitis in host corneal buttons.

Infectious keratitis may be unsuspected preoperatively in patients undergoing penetrating keratoplasty. We have diagnosed five cases of previously unknown corneal infection discovered only after post-keratoplasty histopathologic examination using specific stains. These cases of preoperatively unsuspected infectious keratitis illustrate examples where histopathologic examination using specialized stains may alert the physician to the need for appropriate postoperative antimicrobial therapy. Furthermore, these cases illustrate the ability of soft contact lenses to mask symptoms of infectious keratitis. Additionally, the clinical appearance of advanced bullous keratopathy may mask signs of infectious keratitis.

Acanthamoeba↗
PubMedDate not supplied

Phacoemulsification and modern cataract surgery.

The techniques and results of cataract surgery have changed dramatically during the past three decades. In the USA, we have moved from intracapsular cataract extraction as the preferred technique to almost exclusively extracapsular techniques. Smaller incisions have become the standard, with phacoemulsification now being the method of choice for most surgeons. Along with these advances have come improved intraocular lens materials and designs, especially well suited for use with smaller incisions. Phacoemulsification as a method to remove the cataractous lens was first proposed more than 20 years ago. Advances in techniques and equipment have led to a dramatic increase in the popularity of phacoemulsification with increased safety and efficiency. Viscoelastic agents have been developed synchronously with modern phacoemulsification techniques, playing an integral role in the success of this new technology. Improved surgical techniques for removing the anterior lens capsule have decreased the incidence of both intraoperative and postoperative capsular complications. Nucleus removal, formerly performed primarily in the anterior chamber, is now performed in the posterior chamber, decreasing damage to the corneal endothelium. Improved wound construction allows many wounds to be left unsutured, and smaller wounds allow shorter recovery time and greater intraoperative control and safety. Intraocular lenses can have smaller optic sizes and still maintain accurate centration. Foldable intraocular lenses can take advantage of the smaller incision, even further shortening the time to visual recovery. Continual evolution of this technology promises to further improve patient outcomes after cataract surgery.

Anesthesia, Local↗
PubMedDate not supplied

Effect of refractive surgery experience on outcomes after photorefractive keratectomy.

BACKGROUND: Excimer laser photorefractive keratectomy is effective in the treatment of myopia. It is unclear whether the refractive and ocular surgical experience of the surgeon influences outcome. METHODS: Photorefractive keratectomy was performed on 131 consecutive myopic eyes by one experienced refractive surgeon and on 428 consecutive myopic eyes by six other less experienced surgeons. Outcome data were compared between groups. RESULTS: The mean preoperative spherical equivalent was -5.76 +/- 2.43 diopters (D) in the single surgeon group and -5.36 +/- 2.34 D in the multiple surgeon group. Follow-up of 6 months was available on 109 eyes (83%) in the single surgeon group and 289 eyes (68%) in the multiple surgeon group. At 6 months, the average residual refractive error was +/- 0.15 +/- 1.13 D in the single-surgeon group and +0.21 +/- 1.15 D in the multiple surgeon group. This difference was not statistically significant (p = 0.68). Correction within 1 D of attempted correction was obtained in 76 eyes (70%) in the single surgeon group and in 223 eyes (77%) in the multiple surgeon group. Uncorrected visual acuity of 20/40 or better was achieved in 89 eyes (82%) in the single surgeon group and 253 eyes (88%) in the multiple surgeon group. CONCLUSION: Refractive and visual acuity outcomes after photorefractive keratectomy are influenced minimally by the refractive surgical experience of the surgeon.

Adolescent↗
PubMedDate not supplied

Adjustability of refractive effect for corneal ring segments.

PURPOSE: To evaluate the safety and efficacy of adjustability of the refractive effect of intrastromal corneal ring segments (ICRS, Intacs). METHODS: Data from four patients who had their initial Intacs removed and exchanged for new Intacs of different thickness sizes during a United States Food and Drug Adminstration Phase II clinical trial were evaluated with regard to segment size, reasons for exchange, duration within the cornea before exchange procedure, loss or change of spectacle-corrected visual acuity, change of uncorrected visual acuity, manifest refraction, cycloplegic refraction, topography after exchange, and stability of refraction. RESULTS: The exchange procedure was performed in two patients due to undercorrection and in two for overcorrection. The length of time the segments remained in the cornea after initial surgery varied from 6 to 15 months (mean, 10.25 +/- 4.03 mo). The most recent examination occurred between 4 to 18 months (mean, 10.0 +/- 6.32 mo) following the exchange procedure and showed improved uncorrected visual acuity with a range from 20/16 to 20/20 and a gain of 2 to 7 lines of uncorrected visual acuity compared to baseline. No eyes lost any lines of spectacle-corrected visual acuity following the exchange procedure and all preserved their preoperative spectacle-corrected visual acuity of 20/16. The intended refractive correction was achieved in the first few days of the exchange procedure and remained stable. CONCLUSION: In these four eyes that were over- or undercorrected after initial Intacs placement, segment thickness sizes were exchanged after 6, 8, 12, and 15 months without complication and with final uncorrected visual acuities of 20/16 to 20/20.

Adult↗
PubMedDate not supplied

Intrastomal corneal ring segments: reversibility of refractive effect.

PURPOSE: To evaluate the reversibility of refractive effect following removal of the ICRS (intrastromal corneal ring segments; Intacs). METHODS: Data from 34 eyes from which ICRS were removed during United States FDA Phase II and III clinical trials were evaluated with regard to segment size, loss or change of best spectacle-corrected visual acuity (BSCVA), any change of uncorrected visual acuity (UCVA), manifest spherical equivalent refraction, manifest cylinder refraction, stability of manifest cylinder refraction, and subjective visual symptoms. RESULTS: Out of 725 initial or contralateral eyes placed with the ICRS during Phase II and III clinical trials, segments were removed from 34 eyes (4.7%). Other than one (1/725, 0.1%) safety related ICRS removal, 30/725 (4.1%) were due to visual symptoms. ICRS removal was accomplished under topical anesthesia without complications in all eyes. The mean length of time the segments remained in the cornea after initial surgery was 10.3 +/- 5.4 months. At 3 months after ICRS removal, 21 eyes had monitored data available and were within +/-1 line or 10 letters of their preoperative BSCVA. Twenty eyes (20/21, 95%) returned to within +/-1.00 D of their preoperative manifest spherical equivalent refraction. All eyes had a stable refraction at the 3-month examination after removal, and a manifest spherical equivalent refraction within +/-1.00 D of their 1-month examination after removal. Nineteen eyes (19/21, 90%) returned to within +/-2 lines and 16 eyes (16/21, 76%) returned to within +/-1 line of preoperative UCVA. CONCLUSION: The ICRS (Intacs) was easily and safely removed, and eyes returned to preoperative refractive status within 3 months.

Corneal Stroma↗
PubMedDate not supplied

Topography and raytracing analysis of patients with excellent visual acuity 3 months after excimer laser photorefractive keratectomy for myopia.

We performed topography and raytracing analysis 3 months after surgery on five consecutive eyes of five patients, which had excimer laser photorefractive keratectomy for myopia. Three of the five eyes had uncorrected postoperative visual acuity of 20/20 or better. Two eyes had an uncorrected vision of 20/40. In three of five eyes, the area of excimer ablation was centered within 1.0 mm of the optical axis. Three other eyes showed decentration that ranged from 1.1 to 1.5 mm. The range of surface power seen within 2 mm of the central keratoscope ring was as follows: patient CK = 37.50 to 39.50 diopters; patient CA = 40.50 D to 44.80 D; patient CW = 37.90 D to 42.20 D; patient AC = 35.50 D to 39.00 D; patient DT = 34.50 D to 41.40 D. Topography patterns differed from eye to eye. A raytracing program modeled refraction of 20/80 and 20/20 "E" of 100%, 50%, 25%, 12.5% and 6.25% contrast through all measured points on the central 10 keratoscope rings of the five postoperative corneas. The five computer-derived images were ranked subjectively according to the observed degree of image degradation by three observers. Two eyes showed discernible 20/20 E's even at the 12.5% contrast level. Little to no ghost image was seen. Two eyes showed degraded but discernible 20/20 letters at higher levels of contrast only. These eyes showed moderate ghost images that were most apparent in the high-contrast 20/80 letters. One eye showed poor resolution of the 100% contrast 20/20 letter and moderately severe ghost images.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Myopic excimer laser keratectomy: a preliminary report.

Six patients underwent excimer laser refractive keratectomy for the correction of myopia. All eyes, with the exception of patient 6, who underwent a previous failed epikeratophakia procedure and subsequent removal of the lenticule, had normal baseline ophthalmologic evaluations and best corrected visual acuities of 20/25 or better. Spherical equivalents ranged between -5.50 and -12.00 diopters. Under topical and peribulbar anesthesia, the central corneal epithelium was removed. The delivery system of the laser was programmed to ablate corrections onto the central 5.0 mm of the cornea that would result in approximate emetropia. Moderate fluctuation of refractive and topographic parameters was noted during the period of epithelial healing and remodeling. At the 12th postoperative week, five of the corneas were clear on biomicroscopic evaluation with best corrected acuities of 20/20. The final patient, who was noncompliant in the use of topical corticosteroid therapy, developed a central, 2-mm opacity and resulting best corrected acuity of 20/40. Overall, the group demonstrated that myopic excimer laser photorefractive keratectomy is consistent with good wound healing, insignificant corneal scarring, a stable refractive correction, and excellent visual acuity.

Adrenal Cortex Hormones↗
PubMedDate not supplied

Surgical correction of postoperative astigmatism.

The photokeratoscope has increased the understanding of the aspheric nature of the cornea as well as a better understanding of normal corneal topography. This has significantly affected the development of newer and more predictable models of surgical astigmatic correction. Relaxing incisions effectively flatten the steeper meridian an equivalent amount as they steepen the flatter meridian. The net change in spherical equivalent is, therefore, negligible. Poor predictability is the major limitation of relaxing incisions. Wedge resection can correct large degrees of postkeratoplasty astigmatism, Resection of 0.10 mm of tissue results in approximately 2 diopters of astigmatic correction. Prolonged postoperative rehabilitation and induced irregular astigmatism are limitations of the procedure. Transverse incisions flatten the steeper meridian an equivalent amount as they steepen the flatter meridian. Semiradial incisions result in two times the amount of flattening in the meridian of the incision compared to the meridian 90 degrees away. Combination of transverse incisions with semiradial incisions describes the trapezoidal astigmatic keratotomy. This procedure may correct from 5.5 to 11.0 diopters dependent upon the age of the patient. The use of the surgical keratometer is helpful in assessing a proper endpoint during surgical correction of astigmatism.

Astigmatism↗
PubMedDate not supplied

Human cadaver corneal thinning for experimental refractive surgery.

Human cadaver eyes can be dehydrated by prolonged elevation of intraocular pressure (three to five hours) or by hyperosmotic Dextran over a 20- to 30-minute period. We divided four pairs of donor eyes into two groups (A and B) and dehydrated four corneas by each method. After corneal thinning to 500 to 600 microns, central corneal pachymetry was measured every ten minutes during the rehydration period for one hour, with each cornea pair being moistened at a different rate (every 30 seconds, 1 minute, 2.5 minutes or 5 minutes). The resultant increase in central corneal thickness noted by change in pachymetry (delta P) ranged from 12.4% to 14.7% over one hour between the two groups. delta P did not differ significantly between groups A and B, regardless of the varying rate of balanced salt solution irrigation of the corneas. Thus, it appears that either method of corneal dehydration provides comparable stability of corneal thinning for at least one hour to allow consistent corneal dynamics for experimental refractive surgery.

Acetates↗
PubMedDate not supplied

Further studies of four incision radial keratotomy.

This investigation evaluated the results of radial keratotomy on 52 eyes in 30 patients; 32 eyes had follow-up of greater than one year. The spherical equivalent refraction for 91% of these patients was within 1 diopter of emmetropia. We have followed five eyes between one and two to three years after surgery, observing a continued effect of the surgery with a mean gain in the hyperopic direction of +0.72 diopters. Initial overcorrections must be avoided in radial keratotomy.

Adult↗
PubMedDate not supplied

Viscoelastic agents.

Viscoelastic materials possess a unique set of properties that result from their chemical structure. These properties enable them to protect the corneal endothelium and epithelium from mechanical trauma and to maintain an intraocular space, such as the anterior or vitreous chambers, even in the face of an open incision. Hence viscoelastic materials have been successfully applied to many areas of ophthalmic surgery, most notably anterior segment surgery, with few complications. There are currently three commercially available viscoelastic preparations, and several new preparations are in various stages of development.

Acrylic Resins↗
PubMedDate not supplied

Vital staining of corneal endothelium.

The efficacy and applicability of dual vital staining of human and porcine corneal endothelium with trypan blue and alizarin red S stains was investigated. Exposure of endothelial cells to different concentrations of these two dyes for varying periods of time revealed that 0.3% solution of trypan blue for 1 minute followed by 0.2% solution of alizarin red S (pH 4.2) for 1/2 to 1 minute was the most useful technique to assess the cell viability, micro to macro damage, cell division and cell counts, etc. Alizarin red S dye should not be used in in vivo evaluation, while trypan blue was very effective to evaluate the endothelial viability of donor cornea just prior to keratoplasty.

Animals↗
PubMedDate not supplied

Bacterial endophthalmitis following penetrating keratoplasty suture removal.

A case of bacterial endophthalmitis following suture removal after penetrating keratoplasty is presented. The sutures were removed 10 months postoperatively, and the endophthalmitis became apparent 2 days following suture removal. The patient was chronically immunosuppressed and was found to have a chronic dacryocystitis, which was felt to be the source of the bacterial infection.

Adult↗
PubMedDate not supplied

Cyclosporin A on human corneal endothelium.

Human corneal endothelial cells grown in culture medium were exposed to different concentrations of cyclosporin A in vitro. After 7 days, concentrations of the drug less than 1,000 ng/ml of medium were found nontoxic to the endothelial layer, while greater concentrations killed the cells in 1 hour to 48 hours, depending upon the concentration of the drug. Degenerative cytoplasmic vacuoles were the first sign of toxicity from the drug, leading in higher concentrations to eventual disintegration.

Cornea↗