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Biomedical subjects

R L Lindstrom

Publications and source records attributed to R L Lindstrom.

At least 19 recordsLinked to original sources
PubMed1992

Optisol corneal storage medium.

We compared the safety and efficacy of Optisol (Chiron Ophthalmics, Irvine, California), a new corneal storage medium, with McCarey-Kaufman and Dexsol corneal storage media (Chiron Ophthalmics, Irvine, California) and K-Sol corneal storage medium (Cilco, Huntington, West Virginia). Optisol contains dextran, 2.5% chondroitin sulfate, vitamins, and precursors of adenosine triphosphate (adenosine, inosine, and adenine). In in vitro studies, rabbit and human corneas stored in Optisol were thinner after 12 to 14 days at 4 C than tissue stored in other media. Thymidine uptake showed increased mitotic activity in human corneal endothelial cells cultured in Optisol, compared to Dexsol. Specular microscopic fields showed larger are-as of visibly intact endothelial cells and ultrastructural examination disclosed fewer structural changes in endothelial cells stored in Optisol, compared to tissue stored in Dexsol. In vivo, no clinical signs of epithelial toxicity or histologic evidence of intraocular inflammation were observed in rabbit eyes in which Optisol drops were instilled four times a day for 14 days. Finally, 51 patients undergoing penetrating keratoplasty with tissue stored in Optisol for one to six days (mean, 3.6 days) were enrolled in an uncontrolled, open-label clinical study. The percentage of clear grafts (93%, 41 of 44 patients examined at three months; and 98%, 42 of 43 patients examined at six months) and endothelial cell loss (5.0% and 11.5% at three and six months, respectively) were comparable to data from previous studies that used tissue stored in other short-term and intermediate-term media. The results suggest that Optisol storage preserves corneal endothelial cells for up to two weeks at 4 C, thereby permitting flexibility in the use of donor tissue for corneal transplantation, and that Optisol storage yields thinner tissue, which may allow for more accurate evaluation and more effective surgical manipulation.

Adult↗
PubMed1992

Contrast sensitivity and reading through multifocal intraocular lenses.

Multifocal intraocular lenses are intended to increase depth of focus for patients with cataracts, but optical considerations predict reduced retinal-image contrast. We evaluated visual performance through multifocal intraocular lenses by measuring contrast sensitivity functions and reading speed for age-matched groups with multifocal and monofocal intraocular lenses and two normal control groups. Contrast sensitivity functions of the patients with multifocal lenses did not differ significantly for optical distances differing by 2.5 diopters, indicating substantial depth of focus. Normal and monofocal contrast sensitivity functions were nearly identical, and both were about a factor of two higher than multifocal contrast sensitivity functions. Patients with multifocal lenses showed deficits in reading speed only for low-contrast text (less than 30%) and small letters (0.2 degree and 1.0 degree).

Aging↗
PubMed1991

Clinical use of the 193-nm excimer laser in the treatment of corneal scars.

Phototherapeutic keratectomy using a 193-nm excimer laser was performed at four centers on 33 sighted patients with corneal opacity and/or irregular astigmatism. Pathologic conditions included anterior stromal and superficial scarring from postinfectious and posttraumatic causes, including inactive herpes simplex virus, anterior corneal dystrophies, recurrent erosions, granular dystrophy, and band keratopathy. Most patients received peribulbar anesthesia and underwent removal of the epithelium prior to laser ablation. A majority of patients had a reduction in the amount of corneal scarring and approximately half had improved visual acuity. No intraocular reaction or changes in endothelial counts were seen, and some patients avoided the need for penetrating keratoplasty. Reepithelialization usually occurred within 4 or 5 days and we noted no significant scarring secondary to use of the laser. It was difficult to eliminate preexisting irregular astigmatism despite the use of surface modulators, such as methylcellulose. A hyperopic shift secondary to corneal flattening was encountered in approximately 50% of the patients. A combination of myopic ablation, followed immediately by a secondary hyperopic steepening, may minimize this refractive change. The 193-nm excimer laser is an effective new tool in the treatment of selected patients with superficial corneal opacity from a variety of conditions.

Adult↗
PubMed1991

2% hydroxypropyl methylcellulose as a viscous surgical adjunct. A multicenter prospective randomized trial.

A multicenter prospective trial was conducted comparing preoperative and postoperative endothelial cell counts in patients who had extracapsular cataract extraction with posterior chamber lens implantation or phacoemulsification and posterior chamber lens implantation. One hundred sixty six eyes received 2% hydroxypropyl methylcellulose (Occucoat) and 56 eyes received sodium hyaluronate (Healon). The average cell loss in the Occucoat group was 12.1%; in the Healon group it was 10% (P = NS). There was no significant difference between the two groups in intraocular pressure at 24 hours. In this study Occucoat was as effective in protecting the corneal endothelium as Healon.

Aged↗
PubMed1991

Prospective comparison of the effects of Occucoat, Viscoat, and Healon on intraocular pressure and endothelial cell loss.

We compared the effect of Occucoat (2% hydroxypropylmethyl-cellulose), Viscoat (sodium hyaluronate-chondroitin sulfate), and Healon (sodium hyaluronate) on postoperative intraocular pressure (IOP) and endothelial cell damage. One hundred fourteen patients having planned extracapsular cataract extraction with posterior chamber lens implantation using a viscomaterial were prospectively randomized into one of five groups. Group I received Occucoat which was removed from the anterior chamber at the conclusion of surgery. Group II received Occucoat which was not removed (retained). Group III received Viscoat which was removed, Group IV received Viscoat which was retained, and Group V received Healon which was removed. No prophylactic ocular hypotensive medications were given. Intraocular pressure was measured at four hours, 24 hours, one week, one month, three months, and one year postoperatively. Compared to preoperative IOP, all groups had a significant IOP increase at four hours. All but the Viscoat removed group (Group III) showed a statistically significant increase at 24 hours postoperatively (P less than .05). No group had a significant increase at one week or later. Specular microscopy showed no significant difference in cell loss between any of the groups at three months or within each group when compared to preoperative cell counts (P greater than .1).

Cataract Extraction↗
PubMed1991

A test for crystalline lens biocompatibility.

The current use of monkeys for testing intraocular fluids and viscoelastic materials is being questioned because of the decreasing availability and increasing cost of these scarce animals. The rabbit is an inexpensive, readily available, and convenient animal which might provide an alternative model for this purpose. In this study we have outlined the lens changes (clefts or vacuoles) that are observed in the New Zealand white rabbit as a result of toxicity to intraocular test materials. We used two viscoelastic agents, 1% sodium hyaluronate-Healon and 2% carboxymethylcellulose, and balanced salt solution to evaluate the efficacy and reproducibility of lens changes in this test study. The lens changes in each case were reproducible and could easily be graded. When used in concert with other tests, this new test can help in the preliminary evaluation of an ophthalmic material before its final clinical use in humans.

Animals↗
PubMed1991

Total pupillary capture with a foldable silicone intraocular lens.

We report a case of total pupillary capture on the 1st postoperative day in a patient who had undergone phacoemulsification and placement of a silicone foldable posterior chamber intraocular lens. Anterior displacement of the lens optic resulted in 2.25 diopters of induced myopia. Dilation of the pupil corrected the lens capture and reversed the induced myopia, yielding a refraction of plano. Higher rates of pupillary capture have been associated with sulcus fixation and nonangulated flexible (polypropylene) haptics. Contraction of the capsular bag on the flexible polypropylene haptics of this silicone lens is thought to force the optic anteriorly, increasing the probability of lens capture by the iris.

Adult↗
PubMed1991

Surgical treatment of overcorrection following radial keratotomy: evaluation of clinical effectiveness.

Secondary hyperopia following radial keratotomy (RK) may result from an initial overcorrection or from a continued effect of the procedure with time. We retrospectively evaluated the effect of surgical intervention for the management of overcorrection following RK in six patients who had undergone reopening of all RK incisions, followed by irrigation and closure of the incisions with 10-0 mersilene sutures. Three patients with prior 4-incision RK, with follow-up of 4 to 26 months, were steepened a mean of 1.63 diopters keratometrically; three patients with prior 8-incision RK, with follow-up of 3 to 12 months, were steepened a mean of 1.46 D keratometrically. Comparison of intraoperative with postoperative keratometry demonstrated a substantial loss of effect with time, which stabilized by 2 months in 4-incision RK patients and by 3 months in 8-incision RK patients. Nevertheless, placement of interrupted sutures across reopened radial incisions consistently induced central corneal steepening in these six patients.

Adult↗
PubMed1990

An in vitro and clinical comparison of corneal storage with chondroitin sulfate corneal storage medium with and without dextran.

The safety and efficacy of 1% dextran in Chondroitin Sulfate Corneal Storage Medium (CSM) in reducing corneal swelling after 4 degrees C storage was assessed in a corneal endothelial cell culture system. No difference was found in 3H-thymidine incorporation by cells incubated in either CSM-dextran medium or CSM medium alone. Subsequently, 21 pairs of corneas, stored in either CSM or CSM-dextran from 30 to 112 hours, were transplanted into 42 eyes of 42 patients, paired by diagnostic group and procedure. All CSM grafts and 19 of 21 CSM-dextran grafts were clear at 4 months with no primary donor failures in either group. Intraoperative corneal thickness was significantly greater in the CSM group (0.82 +/- 0.07 mm) than the CSM-dextran group (0.76 +/- 0.06 mm); however, the two groups did not differ thereafter. No differences in all endothelial morphometric parameters were noted between the two groups pre- and postoperatively. Average endothelial cell loss by 4 months was 13.0 +/- 16.4% for the CSM group and 16.4 +/- 15.5% for the CSM-dextran group. The addition of dextran to CSM medium results in significant intraoperative corneal thinning without adversely affecting endothelial DNA synthesis in vitro and endothelial survival in vivo.

Adult↗
PubMed1990

Multifocal intraocular lenses.

Current multifocal intraocular lens designs incorporate refractive or diffractive optical principles to achieve increased depth of focus. Information about four basic design concepts is presented. Early clinical results with two of these, the IOLAB Nuvue two-zone refractive multifocal and the 3M diffractive multifocal, are summarized.

Clinical Trials as Topic↗
PubMed1990

Lysis of vitreous strands with neodymium: YAG laser.

Eighteen eyes with vitreous strands adherent to the corneoscleral wounds of previous cataract surgery were treated with neodymium: YAG laser to lyse those strands. Twelve eyes were treated for management of cystoid macular edema (CME group); six eyes were treated for prophylaxis of possible CME (prophylactic group). In the CME group, visual acuity improved two or more lines in nine eyes (75.0%), and seven eyes had a post laser visual acuity of 0.5 or better (One eye had a pre-treatment visual acuity of 0.5 or better). In the prophylactic group, visual acuity was either maintained at the pre-treatment visual acuity of 0.5 or better. In the prophylactic group, visual acuity was either maintained at the pre-treatment level or improved in five eyes (83.3%) 18 months later following laser treatment. This procedure was complicated by retinal detachment in one case and the elevation of intraocular pressure over 10 mmHg in another case.

Adult↗