Eve J. Higginbotham

Effects of Topical Glaucoma Drugs on Fistuliezed 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.

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.

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.

The Effect of Caffeine on Intraocuular Pressure in Glaucoma Patents

Abstract 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.

Can the concentration of timolol or the frequency of its administration be reduced

BACKGROUND There is evidence that the ocular hypotensive effect of topical beta-blockers persists for at least 24 hours once beta-blockade has been achieved. In previous studies, the highest concentration of drug generally has been used for this purpose. METHOD Home tonometry was performed with a self-tonometer by 14 patients to study the intraocular pressure (IOP) reduction of 0.5% timolol administered once daily in the morning or in the evening and of 0.25% timolol administered in the morning. The study was masked and included washout periods before and between the different regimens. At the end of each treatment period, the IOP was monitored five times daily for 3 days. RESULTS No significant difference in mean reduction of IOP was found between the morning instillation of once daily 0.5% timolol compared with evening instillation of 0.5% timolol. In addition, there was no statistically significant difference in the mean IOP reduction between once daily administration of 0.25% versus 0.5% timolol. CONCLUSION This study indicates that a lower concentration of timolol maleate used once daily may achieve maximum IOP reduction. The time of the single administration appears not to make any difference.

Effects of ascorbic acid on trabecular meshwork cells in culture.

We examined the effects of ascorbic acid on trabecular meshwork cells in culture. Bovine trabecular meshwork cells were plated for 6 days and were exposed to media containing either no ascorbic acid or ascorbic acid in the following concentrations for 24 hr: 50-, 100-, 500-, and 750 micrograms ml-1. Fresh media were then added and incubation was continued for an additional 24 hr. The cell number was subsequently determined for the effects of the various concentrations of ascorbic acid on cell growth. In a parallel experiment, cells were labeled with [35S] sulfate (50 microCi ml-1) and [3H]glucosamine (15 microCi ml-1) for 24 hr with or without ascorbic acid for glycosaminoglycan studies. Results indicated that ascorbic acid stimulated the trabecular cell growth in culture at concentrations of 50-, 100-, and 250 micrograms ml-1. However, at 750 micrograms ml-1, cell growth was inhibited. In addition, cells exposed to 100 micrograms ml-1 of ascorbic acid demonstrated increased incorporation of [3H]glucosamine and [35S]sulfate; enhancement of incorporation of [35S]sulfate was also noted at 250 micrograms ml-1. Incorporation of labels was otherwise either unchanged or retarded at other concentrations. These data suggest that the ascorbic acid level in the aqueous humour may influence trabecular meshwork cell metabolism.

Effects of papaverine pilocarpine and epinephrine on fistulized rabbit conjunctiva

SummaryPretreatment with pilocarpine hydrochloride has been demonstrated to increase the number of myofibroblasts in fistulized conjunctiva in rabbits. To determine if this observation is related to changes in the conjunctival vasculature that may be linked to pilocarpine, we evaluated the effects of a vasodilator and a vasoconstrictor in comparison with pilocarpine hydrochloride. Twenty Dutch-belted rabbits, with five rabbits per group, were treated in a masked fashion in both eyes with topical solutions of 4% pilocarpine hydrochloride, 0.3% papaverine, a combination of 4% pilocarpine and 2% epinephrine, or artificial tears for 3 months. Four of five rabbits in each group underwent thermal sclerostomies in both eyes; the fifth rabbit in each group served as a nonsurgical control. The mean number of myofibroblasts per high-power field was greater in the surgical eyes treated with pilocarpine (6.35

Lensectomy and vitrectomy in the presence of filtering blebs

pM 0.48) or papaverine (9.22

Effects of ascorbic acid on levels of fibronectin, laminin and collagen type 1 in bovine trabecular meshwork in organ culture

pM 0.44) than in the eyes treated with both epinephrine and pilocarpine (4.80

Effects of Antiglaucoma Medications on Bovine Trabecular Meshwork Cells In Vitro

pM 0.70) or artificial tears (5.20