Search PubMed⌕ Search

Biomedical subjects

M B Shields

Publications and source records attributed to M B Shields.

At least 109 records · Page 6Linked to original sources
PubMed1987

Prevalence and mechanisms of secondary intraocular pressure elevation in eyes with intraocular tumors.

A survey of 2704 eyes with intraocular tumors in patients who were evaluated on the Oncology Service at Wills Eye Hospital showed that 126 of the tumor-containing eyes (5%) had tumor-induced elevated intraocular pressure (IOP) at the time of diagnosis of the tumor. Of the 2111 eyes with uveal melanomas, secondary IOP elevation was present in 55 (3%). Secondary IOP elevation was present in 7% of eyes with iris melanoma, 17% with ciliary body melanoma, and 2% with choroidal melanoma. The most common mechanism of elevated IOP was tumor invasion of the angle in the case of iris melanomas, pigment dispersion and tumor invasion of the angle in the case of ciliary body melanomas, and iris neovascularization in the case of choroidal melanomas. Of the 256 eyes with uveal metastases, secondary IOP elevation was found in 12 eyes (5%). Secondary IOP elevation was present in 64% of eyes with iris metastases, 67% with ciliary body metastases, and 1% with choroidal metastases. The most common mechanism of elevated IOP was tumor invasion of the angle in the case of iris and ciliary body metastases, and angle closure in the case of choroidal metastases. There were 303 eyes with retinoblastoma, 17% of which had elevated IOP which was secondary to iris neovascularization in 70% of cases and to an angle closure without neovascularization in 27%. Several other intraocular tumors including lymphoma, leukemia, medulloepithelioma, melanocytoma, and adenoma of the iris pigment epithelium were occasionally associated with secondary elevated IOP.

Biomechanical Phenomena↗
PubMed1987

A common pathway for developmental glaucomas.

In a clinicopathologic study of ten patients, utilizing a modified trabeculectomy technique for acquisition of histologic specimens, a high insertion of the iris was observed in four types of developmental glaucoma. A survey of the literature revealed additional developmental disorders with this abnormality of the anterior chamber angle. The common defect is believed to arise from a developmental arrest during the third trimester of gestation of tissues derived from cranial neural crest cells. The mechanism by which this developmental defect leads to aqueous outflow obstruction may, in some cases, be a paradoxical collapse of the trabecular meshwork and Schlemm's canal in response to contraction of the ciliary musculature, while other patients may have additional developmental abnormalities in the aqueous outflow system as the possible mechanism of glaucoma.

Adolescent↗
PubMed1987

Limbus-based versus fornix-based conjunctival flaps in trabeculectomy.

Forty consecutive trabeculectomies were performed by one surgeon, utilizing a limbus-based conjunctival flap in the first 20 eyes and a fornix-based flap in the remaining 20. A success rate of 90% was achieved in both groups, although eyes with limbus-based flaps had slightly better postoperative intraocular pressure control.

Adult↗
PubMed1986

Comparison of two treatment schedules for combined timolol and dipivefrin therapy.

In a prospective, randomized, single-masked, cross-over study, 18 patients with primary open-angle glaucoma were treated for one month with each of the following regimens: timolol 0.5% twice daily, timolol 0.5% plus dipivefrin 0.1% twice daily given ten minutes apart, and timolol 0.5% plus dipivefrin 0.1% given twice daily four hours apart. An eight-hour intraocular pressure curve was obtained before treatment and at the end of each monthly regimen. When added to timolol therapy, dipivefrin produced a small but statistically significant additional mean decrease in intraocular pressure. The difference in intraocular pressure reduction between the two regimens for combined timolol and dipivefrin therapy was not statistically significant.

Adult↗
PubMed1986

Value and limitations of cyclocryotherapy.

We studied a consecutive series of 114 eyes of 102 patients that were treated with cyclocryotherapy by one surgeon. Intraocular pressure reduction sufficient to avoid further surgical intervention was achieved in two-thirds of the cases. However, the postoperative visual acuity was worse than the preoperative level in 60% of the cases, and 12% of the eyes developed phthisis. Factors which influenced these results included the type of glaucoma and the age of the patient. Eyes with neovascular glaucoma had the worst results, while those having glaucoma in aphakia without neovascular glaucoma had the most favorable response to cyclocryotherapy. Findings further showed that younger patients required more cryotherapy to achieve pressure reduction. Phthisis developed significantly more often following initial treatments than in eyes undergoing one or more repeat cyclocryotherapy procedures.

Adolescent↗
PubMed1986

Combined cataract extraction and guarded sclerectomy. Reevaluation in the extracapsular era.

Thirty-four eyes of 25 patients underwent a guarded sclerectomy in combination with either an intracapsular or extracapsular cataract extraction. The intraocular pressure was well-controlled in the early postoperative period in all but one case, and only one eye developed a flat anterior chamber that required surgical reformation. However, there was a high incidence of intraoperative and postoperative complications in both the intracapsular and extracapsular groups. These observations, as well as experience with extracapsular cataract extraction and posterior chamber lens implantation alone in glaucomatous eyes, have led to a reevaluation of the criteria for combined cataract and glaucoma surgery.

Adult↗
PubMed1986

Intraocular cyclophotocoagulation.

Laser energy, as a cyclodestructive source for the treatment of glaucoma, can be delivered by several routes. The transscleral approach has the advantages of being noninvasive and relatively quick and easy, but the disadvantages of unpredictable results and a high complication rate. Transpupillary cyclophotocoagulation has fewer complications, but is only possible in a small number of eyes. The intraocular intraocular route is a newer technique, which utilises endophotocoagulation through a pars plana incision to treat ciliary processes in aphakic eyes. Visualisation for intraocular cyclophotocoagulation can be either transpupillary with scleral depression to expose the processes or by the use of an endoscope.

Ciliary Body↗
PubMed1985

Two-stage argon laser trabeculoplasty in open-angle glaucoma.

Forty-five adults with primary open-angle glaucoma received argon laser trabeculoplasty in two stages (180 degrees in each session) separated by one month. The indication for argon laser trabeculoplasty in each case was uncontrolled glaucoma consisting of progressive optic disk cupping and visual field loss despite maximally tolerable medication. A P value of .01 by Student's two-tailed paired t-test was used for statistical significance in the analysis of the intraocular pressure data. In most cases, the greatest reduction in intraocular pressure followed stage 1. Some patients received no additional benefit from stage 2; in other cases, the second stage was not only beneficial but provided most of the reduction in pressure. The pretreatment intraocular pressure level influenced the response to laser therapy. Patients with the highest pretreatment intraocular pressures received the most benefit. Both stages were complicated by a transient postoperative increase of 5 mm Hg or more in 12 patients (approximately 19%).

Adult↗
PubMed1985

A dose-response study of piloplex for duration of action.

The duration of reduction in intraocular pressure after single-dose administration of three concentrations of piloplex and the vehicle of the drug was evaluated in 12 patients with open-angle glaucoma in a randomized, double-masked, crossover study. Piloplex lowered intraocular pressure in a dose-related fashion, with a duration of action of at least 14 hours.

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↗
PubMed1985

Cyclodestructive surgery for glaucoma: past, present, and future.

When surgical attempts to control glaucoma by improving aqueous outflow are not successful, the alternative approach is usually to reduce aqueous inflow by a cyclodestructive procedure. Cyclodestructive elements that have been tried in the past include diathermy, electrolysis, and beta irradiation. Cyclocryotherapy is presently the most commonly used cyclodestructive procedure, although this operation has significant limitations, and newer techniques are being evaluated utilizing laser energy or ultrasonic radiation. Each of these procedures uses a transcleral approach, which has the disadvantages of (1) the inability to precisely quantitate the destruction of the ciliary processes, and (2) damage to adjacent tissue. Transpupillary cyclophotocoagulation minimizes these problems, but is limited to the small number of eyes in which adequate gonioscopic visualization of the ciliary processes can be achieved. An alternative approach for aphakic eyes is intraocular cyclophotocoagulation, utilizing an endophotocoagulator through a pars plana incision. Depending on the status of the eye, visualization for this technique can be accomplished either by the transpupillary route or with an endoscope.

Adolescent↗
PubMed1984

Betaxolol and timolol. A comparison of efficacy and side effects.

Betaxolol hydrochloride, 0.5%, and timolol maleate, 0.5%, were compared in a 26-week randomized, double-masked study involving 46 patients with primary open-angle glaucoma. The two drugs were comparable with regard to both intraocular pressure-lowering efficacy and side effects. Since betaxolol is a selective beta 1-adrenergic antagonist, it may be advantageous for patients in whom beta 2-blockade could be harmful.

Aged↗
PubMed1984

Open-angle glaucoma associated with posterior polymorphous dystrophy. A clinicopathologic study.

Clinical and histopathologic features of a 62-year-old black man with posterior polymorphous dystrophy and open-angle glaucoma requiring trabeculectomy are reported. The surgical procedure was modified to allow en bloc resection of the deep limbal tissue and peripheral iris. Light and electron microscopy of the specimen revealed a high insertion of the iris into the posterior portion of the trabecular meshwork with compression of the intertrabecular spaces. These findings are similar to changes that have been reported in primary congenital glaucoma and suggest a developmental anomaly of the anterior chamber angle in this form of glaucoma associated with posterior polymorphous dystrophy.

Cornea↗
PubMed1983

Effect of timolol on aqueous humor protein concentration in humans.

Short-term topical application of timolol, in a prospective, randomized, double-masked study of 32 human eyes, was associated with an average aqueous humor protein concentration of 38 mg/100 ml, compared to 13 mg/100 ml in control subjects (P less than .001). This apparent influence of timolol on aqueous protein levels probably resulted from reduced aqueous production. It did not affect the course of intraocular surgery.

Aged↗
PubMed1983

Timolol in the management of secondary glaucomas.

The mechanisms of the secondary glaucomas and the actions and side effects of antiglaucoma drugs are reviewed. Based on these observations, the advantages of timolol, as compared to other medications, in the management of secondary glaucomas are discussed. To illustrate some of these advantages, a study is reported in which timolol is evaluated for control of the early intraocular pressure elevation after routine cataract surgery.

Carbonic Anhydrase Inhibitors↗