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Biomedical subjects

M E Yablonski

Publications and source records attributed to M E Yablonski.

At least 37 records · Page 2Linked to original sources
PubMed1989

Trabecular outflow facility determined by fluorophotometry in human subjects.

We studied a new fluorophotometric method to determine trabecular outflow facility in man. Pilocarpine was selected to evaluate this non-invasive method, since its primary ocular hypotensive effect is to increase trabecular outflow facility. Levobunolol was used to decrease intraocular pressure and aqueous humor flow required for the calculation of trabecular outflow facility. In ten ocular hypertensive patients trabecular outflow facility in the pilocarpine-treated eyes was 0.42 +/- 0.16 (S.D.) microliters min-1 mmHg-1 compared with 0.17 +/- 0.14 microliters min-1 mmHg-1 in the vehicle-treated eyes (P less than 0.004). An ocular hypotensive additivity was also found in the eyes treated with both drugs. It was concluded that this non-invasive fluorophotometric method may be useful in evaluating the effect of a drug on trabecular outflow facility.

Aqueous Humor↗
PubMed1989

Decreased formation of aqueous humour in insulin-dependent diabetic patients.

The rate of aqueous humour formation was measured by fluorophotometry in 34 insulin-dependent diabetic patients and 12 non-diabetic controls to determine whether or not aqueous flow in diabetics differed from that of normal controls, and whether or not aqueous flow among diabetics was correlated with the stage of retinopathy. Diabetic patients were divided into three groups based on the degree of retinopathy; group I without retinopathy, group II with minimal to moderate non-proliferative retinopathy, and group III with proliferative retinopathy. Aqueous flow (mean, SD) in diabetic patients was: 1.55 (0.32) microliter/min in group I, 1.51 (0.47) microliter/min in group II, and 1.26 (0.39) microliter/min in group III. No statistically significant difference was found among these three diabetic groups. Aqueous flow in the non-diabetic controls was 2.18 (0.40) microliter/min, and this was statistically significantly greater than in each of the diabetic groups. Intraocular pressure, age, duration of diabetes, haemoglobin A1C, and blood glucose levels had no significant effect on aqueous flow in diabetic patients.

Adult↗
PubMed1988

Enhancement of the ocular hypotensive effect of acetazolamide by diflunisal.

We studied the effect of diflunisal on intraocular pressure in patients with glaucoma who were receiving maximally tolerated therapy. Diflunisal therapy, 500 mg twice daily, was started in 48 patients for one week. No changes were made in their regular antiglaucoma medications. Intraocular pressure was reduced an additional 3.8 +/- 3.1 mm Hg (+/- S.D.) in the acetazolamide-treated patients (P less than .0001) and 1.6 +/- 1.5 mm Hg in methazolamide-treated patients (P less than .02), while no significant reduction in intraocular pressure was found in patients receiving topical medications alone. In 15 acetazolamide-treated patients, total plasma concentrations of acetazolamide after diflunisal therapy were significantly higher than the prediflunisal levels, suggesting a modest decrease in renal excretion. In seven acetazolamide-treated patients, free plasma concentrations of acetazolamide were found to increase 5.6-fold after diflunisal therapy. We concluded that diflunisal potentiated the ocular hypotensive effect of acetazolamide by increasing its free plasma level.

Acetazolamide↗
PubMed1988

Effect of cold air on aqueous humor dynamics in humans.

Several parameters of aqueous humor dynamics were measured in 11 human subjects before and after exposure of one eye to a continuous stream of cold air. In the treated eye, I.O.P. was found to decrease significantly from a mean +/- SD pre-treatment value of 14.1 +/- 2.3 mmHg to a post-treatment value of 12.6 +/- 2.6 mmHg. Episcleral venous pressure was found to decrease significantly from a pre-treatment value of 6.2 +/- 1.3 mm Hg. No significant changes were found in aqueous flow or total outflow facility, indicating that cold air exposure decreased I.O.P. by causing a decrease in episcleral venous pressure.

Air↗
PubMed1987

The effect of levobunolol on aqueous humor dynamics.

We evaluated the acute effects of installation of 0.5% levobunolol on aqueous humor dynamics in a double-masked study in 18 patients with ocular hypertension. Aqueous flow was measured by fluorophotometry and total outflow facility by tonography. Aqueous flow decreased approximately 29% in the eyes treated with levobunolol. Total outflow facility and episcleral venous pressure measurements were similar in levobunolol-treated eyes and contralateral eyes treated with vehicle. A 36% decrease in intraocular pressure was observed in the levobunolol-treated eyes and a slight intraocular pressure reduction was seen in the vehicle-treated eyes. The results of this study indicate that, similar to timolol, levobunolol lowers intraocular pressure primarily by decreasing aqueous humour production.

Adrenergic beta-Antagonists↗
PubMed1987

Eicosanoids as a new class of ocular hypotensive agents. 2. Comparison of the apparent mechanism of the ocular hypotensive effects of A and F type prostaglandins.

It has recently been shown that derived prostaglandins (PGs) of the A and B types are much more potent ocular hypotensive agents than primary PGs of the E, F, or D type. The purpose of this study was to determine whether two representatives of these structurally different PGs, namely PGA2 and PGF2 alpha-1-isopropyl ester (PGF2 alpha IE), reduce intraocular pressure (IOP) of the feline eye by similar or dissimilar mechanisms. Aqueous humor flow rate was determined by a fluorophotometric technique, Schiotz electronic tonography was used to measure outflow facility and venomanometry was done to measure episcleral venous pressure. Although at the doses used, both PGF2 alpha IE (2.5 micrograms/eye) and PGA2 (5.0 micrograms/eye) caused significant IOP reduction within 2.5 hr after their topical application, neither caused a significant decrease in aqueous humor flow rate, a significant increase in outflow facility or a change in episcleral venous pressure. It was concluded, therefore, that both of these PGs reduce IOP by an apparently similar mechanism, presumably by increasing uveoscleral outflow.

Animals↗
PubMed1987

Fluorophotometric study of intravenous carbonic anhydrase inhibitors in rabbits.

The ability of fluorophotometry to measure the time course of changes in aqueous humor flow in rabbits was evaluated by measuring the effect of intravenous carbonic anhydrase inhibitors on aqueous humor flow determinations. The abrupt changes in aqueous humor flow which were found by fluorophotometry agreed well with the expected changes in aqueous humor flow calculated from the time course of the intraocular pressure. Therefore, it was concluded that fluorophotometry could measure the time course of changes in aqueous humor flow in rabbits. Furthermore, it was suggested that the initial abrupt changes in aqueous humor flow after the administration of a carbonic anhydrase inhibitor were induced by the base content of the drug, followed by a more gradual decrease in aqueous humor flow caused by the direct effect of the drug on aqueous humor formation.

Animals↗
PubMed1986

Treatment of glaucoma with high-intensity focused ultrasound.

This report is a summary of results for 170 eyes of patients with refractory glaucoma treated with high-intensity focused ultrasound. The results are analyzed in terms of the effectiveness of various treatment regimens, complications, and classifications of the patient population according to such factors as age and etiology. The mean pretreatment intraocular pressure (IOP) for the ensemble of patients treated with optimal intensity levels was 38.6 mmHg. Whereas only 10% of these patients had an IOP of 25 mmHg or less prior to treatment, 90% had an IOP of 25 mmHg or less within 3 months of treatment. At 1 year after a single treatment, 65% of patients still maintained intraocular pressures of 25 mmHg or less, and 56% had pressures of 22 mmHg or less. The effectiveness of retreatment of failed or unresponsive cases was also investigated and found to have a degree of success comparable to that of initial treatments.

Choroid↗
PubMed1986

Dexamethasone, D-penicillamine, and glaucoma filter surgery in rabbits.

A study was made in rabbits of the effect of topical dexamethasone ointment, .05%, and either subconjunctival or intraperitoneal D-penicillamine on the duration of function of glaucoma filtering surgery. The drugs were tested alone and in combination. Intraperitoneal D-penicillamine was not effective, either alone or combined with topical dexamethasone. Topical dexamethasone ointment alone and subconjunctival D-penicillamine alone significantly prolonged the duration of function of the filter surgery; however, when combined, no additional effect was observed. It was concluded that the institution of therapy with both drugs immediately after glaucoma filtering surgery was not the optimal temporal sequence for combining the two modes of therapy.

Administration, Topical↗
PubMed1985

A fluorophotometric study of the effect of argon laser trabeculoplasty on aqueous humor dynamics.

Fluorophotometry and tonography were used before and after argon laser trabeculoplasty to measure aqueous humor dynamics in 15 eyes of 14 patients. A new fluorophotometric method used to measure true outflow facility showed that it increased from a mean pretreatment value of 0.016 microliter/min/mm Hg to a mean posttreatment value of 0.075 microliter/min/mm Hg. Similarly, total outflow facility, measured tonographically, increased from 0.112 microliter/min/mm Hg to 0.151 microliter/min/mm Hg. Uveoscleral flow decreased after laser therapy; however, this was secondary to the decrease in intraocular pressure. No effect was found on the rate of aqueous humor production. We concluded that the primary effect of argon laser trabeculoplasty was to increase true outflow facility, thereby decreasing intraocular pressure.

Aqueous Humor↗
PubMed1985

Therapeutic ultrasound in the treatment of glaucoma. II. Clinical applications.

Focused, high-intensity therapeutic ultrasound was used to treat 69 selected patients with uncontrollably elevated intraocular pressure (IOP). This new technique selectively thins scleral collagen, and produces focal damage to the ciliary epithelium. These tissue modifications provide a reduction in IOP pressure to 25 mmHg or less in 83% of patients with a minimum three-month follow-up period.

Ciliary Body↗
PubMed1985

Effect of oxygen on aqueous humor dynamics in rabbits.

A study was made in albino rabbits of the effect on aqueous humor dynamics of 100% oxygen, administered by face mask. A mean decrease in intraocular pressure of 4.9 mm Hg was found. This was accompanied by a decrease in episcleral venous pressure of 4.5 mm Hg. Anterior chamber aqueous humor flow decreased transiently after oxygen administration but returned to pre-oxygen levels after about 60 min. It was concluded that the sustained decrease in intraocular pressure which was caused by oxygen was secondary to the decrease in episcleral venous pressure and not to a decrease in the production of aqueous humor.

Animals↗
PubMed1984

Spontaneous remission of glaucoma in scleromalacia perforans: a case report.

Spontaneous resolution of glaucoma in a patient with scleromalacia perforans is described. Fluorophotometric measurements established the presence of normal aqueous production. The reduced intraocular pressure is ascribed to either autolysis of the trabecular meshwork and/or maximization of the uveoscleral pathway.

Aged↗
PubMed1983

Topical nylidrin and aqueous humor dynamics in rabbits and monkeys.

Topical administration of nylidrin hydrochloride lowered intraocular pressure in both albino rabbits and cynomologus monkeys. The maximum decrease occurred two hours following drug application and was unilateral. The response lasted four hours in monkeys and at least six hours in rabbits. Outflow facility, episcleral venous pressure, and aqueous humor flow measured by fluorophotometry were unaltered in both species. In rabbits in the treated eyes, ocular blood flow was increased, and anterior and posterior chamber ascorbate concentrations were unchanged. The mechanism of IOP reduction appears to be increased aqueous humor outflow via uveoscleral outflow routes that are not pressure dependent.

Administration, Topical↗
PubMed1983

An unusual presentation of isolated optic nerve sarcoidosis.

A 32-year old diabetic female had unilateral reduced vision (20/30) in an eye having the ophthalmoscopic appearance of papillophlebitis of the optic nerve head. After an apparently benign course, with recovery, the optic disc became edematous again and a central retinal vein occlusion blinded the eye. Thereafter, an avascular bilobed mass progressively protruded from the optic nerve head. Computerized tomography demonstrated uniform thickening of the optic nerve from the globe through the optic canal. The radiographic appearance was consistent with an optic nerve glioma or meningioma. Spinal fluid, chest x-ray, and serum angiotensin converting enzyme activity were normal. Tuberculin skin test was positive. Optic nerve biopsy demonstrated a noncaseating granuloma and a subsequent Kveim test was positive. Isolated optic nerve sarcoidosis may exist without other systemic manifestations. The appearance on computerized tomography may be similar to that of an optic nerve glioma or meningioma.

Adult↗
PubMed1981

Fluorophotometric study of epinephrine and timolol in human subjects.

The action and interaction of topical 2% epinephrine hydrochloride and 0.5% timolol maleate therapy were studied in 12 normal and 16 ocular hypertensive subjects. Measurements of intraocular pressure, outflow facility, and aqueous secretion by fluorophotometry were made. Uveoscleral outflow values were calculated. Epinephrine, applied topically twice daily for one week, resulted in a decrease in IOP of 3.3 +/- 0.9 mm Hg and an increase in outflow facility of 0.05 +/- 0.01 microL/min/mm Hg, as well as an increase in the rate of aqueous production of 0.32 +/- 0.09 microL/min. Uveoscleral outflow showed an increase of 0.83 +/- 0.23 microL/min. Timolol, applied topically twice daily for one week, reduced the IOP 3.9 +/- 1.0 mm Hg and decreased aqueous flow 0.84 +/- 0.23 microL/min, but produced no change in outflow facility or uveoscleral flow. When epinephrine and timolol are given in combination, the effects in lowering IOP may not be completely additive.

Aqueous Humor↗
PubMed1981

Dipivefrin and echothiophate. Efficacy of combined use in human beings.

In a previous study, pretreatment of rabbit eyes with echothiophate iodide prevented the ocular hypotensive effect of dipivefrin. The present masked study, using inpatient volunteers and nurse-administered drops, investigated whether a similar antagonism of action occurred in human beings. Eight volunteers received 0.25% echothiophate iodide twice a day in both eyes for three weeks. During the second week of therapy, one eye also received 0.25% dipivefrin twice a day and the contralateral eye received 2% epinephrine hydrochloride twice a day. During the third week of therapy, the eyes receiving dipivefrin and epinephrine were reversed. In four volunteers, dipivefrin plus echothiophate produced a significantly greater reduction in intraocular pressure than epinephrine plus echothiophate. As a group the eight eyes treated with dipivefrin plus echothiophate had significantly lower IOPs than the eyes treated with epinephrine plus echothiophate during the second week of therapy. Epinephrine plus echothiophate was never superior to dipivefrin plus echothiophate. Dipivefrin seemed to be effective during combination therapy with echothiophate.

Drug Therapy, Combination↗