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Biomedical subjects

E J Higginbotham

Publications and source records attributed to E J Higginbotham.

At least 19 recordsLinked to original sources
PubMed1992

Intraoperative mitomycin versus postoperative 5-fluorouracil in high-risk glaucoma filtering surgery.

In a randomized clinical trial, the authors compared the use of postoperative subconjunctival injections of 5-fluorouracil (5-FU) in 19 eyes with a single intraoperative application of subconjunctival mitomycin (MMC) at the filtering site in 20 eyes at high risk for failure of glaucoma filtering surgery. Six months after surgery, intraocular pressures averaged 10.9 +/- 5.3 mmHg (mean +/- standard deviation) in the MMC-treated eyes versus 14.2 +/- 5.5 mmHg in the 5-FU-treated eyes (P = 0.08) and were less than or equal to 12 mmHg in 60.0% of MMC-treated eyes and 21.1% of 5-FU-treated eyes (P = 0.03). Mitomycin-treated eyes were receiving an average of 0.3 +/- 0.5 medications for intraocular pressure control, and 5-FU-treated eyes were receiving an average of 1.1 +/- 1.1 medications (P = 0.01). Drug-induced corneal epithelial defects were seen in nine 5-FU-treated eyes and in no MMC-treated eyes (P = 0.0004). These results suggest that intraoperative MMC may be a viable alternative to postoperative 5-FU, with lower overall intraocular pressures, decreased dependence on postoperative ocular antihypertensive medications, and decreased corneal toxicity.

Adult↗
PubMed1992

Ascorbic acid modulates collagen type I gene expression by cells from an eye tissue--trabecular meshwork.

The trabecular meshwork, a specialized tissue in the anterior chamber of the eye, plays a major role in the regulation of aqueous humor outflow. We studied the effects of ascorbic acid, a significant component in the aqueous humor, on gene expression of type I collagen in cultures of bovine trabecular meshwork cells. These cells were plated for 6 days, exposed to ascorbic acid in concentrations of 100, 250 and 500 micrograms/ml for 3 days and labeled with (3H)proline for the last 24 hrs. Cultures that did not receive ascorbic acid served as controls. Bacterial collagenase assays showed enhanced incorporation of (3H)proline into collagenous proteins in cultures treated with 100 and 250 micrograms/ml of ascorbic acid. Gel electrophoresis and fluorography revealed that ascorbic acid caused a 2.6- to 4.9-fold increase in production of alpha 1 (I) and alpha 2(I) collagen chains by trabecular meshwork cells. Such an increase was found, using a cDNA probe specific for pro alpha 1(I) chains, to be accompanied by an increase in steady-state mRNA levels. Similar findings were also yielded from in situ hybridization experiments. These results, coupled with previously demonstrated ascorbate-induced effects on glycosaminoglycan, fibronectin and laminin synthesis, suggest that ascorbic acid is a key mediator of the extracellular matrix production by trabecular meshwork cells. Fluctuations in its concentration may lead to alterations in the makeup and assembly of matrices underlying the cells.

Animals↗
PubMed1991

MK-507 versus sezolamide. Comparative efficacy of two topically active carbonic anhydrase inhibitors.

Topical carbonic anhydrase inhibitors MK-507 and sezolamide hydrochloride (previously known as MK-417) were compared in a double-masked, randomized, placebo-controlled study in 82 patients with bilateral primary open-angle glaucoma or ocular hypertension. MK-507 was given every 8 or 12 hours, sezolamide every 8 hours, or placebo every 8 or 12 hours for 4 days. Both drugs lowered intraocular pressure (IOP) substantially. MK-507 was somewhat more active than sezolamide, with a peak mean IOP reduction of 26.2% for MK-507 versus 22.5% for sezolamide, although the difference between the treatments was not statistically significant. These drugs may have potential in the treatment of glaucoma.

Administration, Topical↗
PubMed1991

Cyclophotocoagulation with the transscleral contact neodymium: YAG laser versus cyclocryotherapy in rabbits.

Either transscleral cyclophotocoagulation with the contact neodymium:YAG (Nd:YAG) laser or cyclocryotherapy (CCT) was performed in rabbits to compare the efficacy of these procedures in reducing intraocular pressure (IOP) as well as the histologic changes they induced. The difference in mean maximum reduction of IOP in the two groups was statistically insignificant, but the Nd:YAG laser irradiation, using 2.5 J, destroyed less tissue than the CCT.

Animals↗
PubMed1990

MK-927: a topical carbonic anhydrase inhibitor. Dose response and duration of action.

The dose response to a single topical administration of the carbonic anhydrase inhibitor MK-927 was investigated in 24 patients with primary open angle glaucoma or ocular hypertension. Three concentrations of MK-927 (2%, 1%, and 0.5%) and placebo were administered in a two-center, double-masked, randomized, placebo-controlled, four-period crossover study. MK-927 at the 0.5% concentration appeared to be minimally effective in reducing intraocular pressure. A single topical dose of 1% MK-927 resulted in a significantly greater percent reduction in intraocular pressure for up to 6 hours when compared with treatment with placebo. Similarly, a single dose of 2% MK-927 significantly lowered intraocular pressure for 8 hours compared with treatment with placebo. The pressure reduction from baseline measured 23.7% and 11.3% at 8 hours after instillation of a single drop of 2% MK-927. The medication was well tolerated and appeared to lower intraocular pressure in a dose-dependent fashion.

Adult↗
PubMed1990

Assessment of intraocular pressure in vitrectomized gas-containing eyes. A clinical and manometric comparison of the Tono-Pen to the pneumotonometer.

Elevation of intraocular pressure (IOP) in gas-containing eyes occurs not infrequently, and applanation tonometry in eyes with epithelial irregularities is not accurate. The pneumotonometer and TonoPen (Oculab, La Jolla, Calif) are alternative tonometers for use in these eyes, yet the accuracy of determining IOP with the Tono-Pen has not been determined manometrically. We performed a clinical and manometric study comparing the Tono-Pen with the pneumotonometer in gasfilled vitrectomized eyes. In our clinical study, we measured IOP in 50 eyes of 50 patients with corneal irregularities following vitrectomy and air/gas-fluid exchange. Tono-Pen measurements were highly correlated with those of the pneumotonometer. However, there was a mean difference of 1.4 mm Hg between Tono-Pen and pneumotonometer IOP readings. A larger percentage of Tono-Pen readings were lower than those of the pneumotonometer as IOP levels increased. To assess the accuracy of these tonometers, we compared manometric readings via an indwelling catheter with Tono-Pen and pneumotonometer IOP readings in 11 eye bank eyes following a lensectomy, vitrectomy, and air-fluid exchange. Overall, Tono-Pen and pneumotonometer readings were highly correlated with those of the manometer. However, both machines showed a significant underestimation of IOP at pressures greater than or equal to 30 mm Hg; pneumotonometer and Tono-Pen readings averaged 10.2 and 12.1 mm Hg lower, respectively, than those of the manometer. We conclude that both the pneumotonometer and the Tono-Pen underestimate IOP at pressures greater than or equal to 30 mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS)

Air↗
PubMed1990

Ascorbic acid modulates the production of fibronectin and laminin by cells from an eye tissue-trabecular meshwork.

Ascorbic acid is a significant component in the aqueous humor of the eye, in which trabecular meshwork cells are immersed. Using immunostaining and Western blot analysis, the effects of ascorbic acid on the extracellular matrix production by cultured bovine trabecular meshwork cells were examined. It was found that, when the cultures were treated with 100, 250, and 500 micrograms/ml of ascorbic acid, the amount of fibronectin and laminin produced was enhanced. An enzyme-linked immunosorbent assay for quantitation further showed that the fibronectin and laminin levels in ascorbate-treated cultures were higher than those found in control cultures. These results indicate that ascorbic acid promotes fibronectin and laminin production and suggest that this substance may be one of the factors modulating basal lamina assembly in the trabecular meshwork.

Animals↗
PubMed1990

Effects of topical glaucoma drugs on fistulized rabbit conjunctiva.

Conjunctival fibroblastic proliferation with contracting scar formation has been implicated as a possible cause of glaucoma filtering surgery failure. The effects of glaucoma medications on bulbar conjunctiva were evaluated in both eyes of 20 pigmented rabbits, with 5 rabbits per group each receiving singular topically applied daily doses of either 0.5% timolol, 1% epinephrine, 4% pilocarpine, or artificial tears in a masked fashion for 4 months. Posterior lip sclerectomies were performed in 16 rabbits--4 from each treatment group. The remaining four rabbits served as nonsurgical controls. Four additional rabbits, which had not received eye drops, were included as a nonmedicated control group, with one rabbit serving as a nonsurgical control. Immunostaining was performed to identify the presence of myofibroblasts in fistulized conjunctiva. Treated surgical eyes, regardless of medication, had higher myofibroblastic cell proliferation than treated nonsurgical eyes. Among fistulized eyes, all medications increased cell proliferation, with pilocarpine eliciting the most dramatic increase compared with all other groups.

Animals↗
PubMed1989

The effect of caffeine on intraocular pressure in glaucoma patients.

The authors investigated the effect of drinking regular coffee on intraocular pressure (IOP) using a single-masked randomized crossover study comparing coffee and herbal tea in 13 glaucoma patients. Intraocular pressure and blood pressure were monitored before ingestion of coffee or tea and at 30, 60, and 90 minutes after ingestion. The mean (+/- standard error of measurement) change in IOP 30, 60, and 90 minutes after ingestion for the coffee drinkers was 0.96 +/- 0.4, 1.38 +/- 0.53, and 1.04 +/- 0.37 mmHg, respectively. The mean change in IOP for the tea drinkers 30, 60, and 90 minutes after ingestion was 0.85 +/- 0.41, 0.23 +/- 0.36, and -0.42 +/- 0.44 mmHg, respectively. There was a statistically significant difference in the change in IOP at 90 minutes when comparing coffee to tea (P = 0.003) and no significant difference for 30 and 60 minutes. Although there was a statistically significant difference in IOP at 90 minutes between coffee and tea drinkers, the change was not clinically significant.

Beverages↗
PubMed1988

Effects of cyclocryotherapy on aqueous humor dynamics in cats.

The effects of graded cyclocryotherapy were studied using pneumatonometry, fluorophotometry, and light and electron microscopy. Cats were treated with either 90 degrees, 180 degrees, or 270 degrees of cyclocryotherapy and were followed up for six weeks. The response of the eyes to treatment was evaluated in terms of intraocular pressure (IOP) response, aqueous humor flow rate, and permeability of the blood-aqueous barrier compared with the untreated fellow eye. The average IOP response was determined to be -20%, -44%, and -47% for the 90 degrees, 180 degrees, and 270 degrees treated eyes, respectively. The aqueous humor flow rate was estimated to be -14%, -44%, and -52% for each of the groups, respectively. Finally, the permeability of the blood-aqueous barrier, measured 60 minutes after injection of fluorescein, was estimated to be a percent increase of 22%, 332%, and 285% for each of the groups, respectively. Histologically, the maximally treated eyes (270 degrees) demonstrated greater disruption of the ciliary body compared with the control eyes. Thus, graded cyclocryotherapy causes graded destruction of the ciliary epithelium and proportionally related changes in IOP and aqueous humor dynamics.

Animals↗
PubMed1988

Internal sclerostomy with the Nd: YAG contact laser versus thermal sclerostomy in rabbits.

The authors undertook an investigation to evaluate the efficacy and complications of performing internal sclerostomy with the synthetic sapphire contact neodymium:YAG (Nd:YAG) laser compared with standard external thermal sclerostomy. Fifteen rabbits underwent internal laser sclerostomy in one eye; 12 additional rabbits underwent a standard external thermal sclerostomy in one eye. The fellow eyes served as controls. The differences between the groups in duration of functional blebs and pressure reduction were statistically significant (P = 0.034 and 0.0013, respectively). The evaluation of success (as determined by a pressure reduction greater than 3 mmHg between both eyes after digital pressure) using life-survival analysis indicated that the success rate of the laser-treated group was significantly different from the standard surgical group (P = 0.002). Histologically, there was less inflammation in the laser-treated group 2 days postoperatively. The complications of the laser treatment include focal injury to the overlying cornea, adjacent iris stroma, and lens.

Aluminum Silicates↗