Biomedical subjects

T Oshika

Publications and source records attributed to T Oshika.

At least 109 records · Page 6Linked to original sources

PubMed1991

Effect of bunazosin hydrochloride on intraocular pressure and aqueous humor dynamics in normotensive human eyes.

We investigated the effects of topical administration of bunazosin hydrochloride, a new selective alpha 1-adrenergic antagonist, on intraocular pressure and aqueous humor dynamics in normal human eyes. In the single-dose study, all concentrations of bunazosin (0.025%, 0.05%, 0.1%, and 0.2%) significantly lowered intraocular pressure in a concentration-dependent manner. Administration of multiple doses of 0.1% bunazosin revealed no occurrence of tachyphylaxis after 1 week. Single application of 0.1% bunazosin had no significant influence on aqueous flow rate, tonographic outflow facility, or episcleral venous pressure, suggesting that bunazosin reduces intraocular pressure by increasing uveoscleral outflow. Aqueous protein concentration was found to be unaltered by bunazosin, indicating that blood-aqueous barrier permeability to protein molecules remained unchanged. We conclude that bunazosin may be a possible new antiglaucoma agent with a mechanism of action different from those currently in use for treating ocular hypertension.

Administration, Topical↗

PubMed1991

Effect of systemic acetazolamide on the fluid movement across the aqueous-vitreous interface.

In an attempt to study the effect of systemic acetazolamide on the fluid flow between the aqueous and vitreous in normal eyes, 50 mg kg(-1) acetazolamide was given intravenously every hour for 3 hr and the time change of the aqueous flow rate was calculated in two groups of rabbits, applying one of the following two different methods to each: the fluorescein method II of Jones and Maurice, a classical fluorometric method, or the more recently developed Johnson-Maurice method which entails intravitreal injection of FITC-dextran and measurements of its concentration in the anterior chamber many days after the injection. The flow rate after acetazolamide calculated by the fluorescein method II of Jones and Maurice in one group of rabbits was reduced to 55 +/- 5% (mean +/- S.E. n = 9) of the control on the average. When calculated by the Johnson-Maurice method in another group of rabbits, the reduction was to 80 +/- 4% (n = 11) of the control rate. The difference between the above figures was significant (P less than 0.005). Furthermore, the effect of acetazolamide calculated by the first procedure was significantly greater than that calculated by the second at 1 and 2.33 hr and at later times after the acetazolamide injection (P less than 0.05-0.01). On the other hand, the outflow pressure was reduced by 53-60% in both groups. The difference between the flow rates after acetazolamide determined by the above two methods was best explained by assuming that the FITC-dextran movement from the vitreous into the aqueous was reduced by about 25% after acetazolamide administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetazolamide↗

PubMed1991

Severe corneal edema after prolonged use of psychotropic agents.

A 23-year-old woman with schizophrenia who had been treated with a high dose of psychotropic agents for 6 years had bilateral corneal edema and suffered from severe visual disturbance. No signs of inflammation, infection, congenital abnormality, or corneal endotheliitis were observed. The symptoms did not respond to either topical or systemic treatments. Reduction in the dosage of psychotropic agents resulted in quick and complete disappearance of the corneal edema within 2 weeks. Specular microscopic examination after recovery revealed a marked enlargement of corneal endothelial cells, but there was no evidence of any corneal dystrophy. Blood-aqueous barrier function was not deteriorated, as demonstrated by aqueous protein concentration measured with a laser flare-cell meter. In conclusion, we suggest that corneal edema may be caused by prolonged use of psychotropic agents, particularly a major tranquilizer.

Adult↗

PubMed1991

Effects of topical application of UF-021, a novel prostaglandin derivative, on aqueous humor dynamics in normal human eyes.

The mechanism underlying the intraocular pressure (IOP) lowering effect of a prostaglandin-related compound, isopropyl 20-ethyl-9 alpha,11 alpha-dihydroxy-15-keto-cis-delta 5-prostanoate (UF-021), and its possible adverse effects in long-term use were studied in normal human eyes. A single instillation of 0.12% UF-021 significantly lowered IOP without affecting aqueous flow rate, tonographic C value or episcleral venous pressure. Protein concentration in the anterior chamber and corneal endothelial permeability to fluorescein remained unaffected. It was suggested that UF-021 lowers IOP mainly by increasing uveoscleral outflow. Twice daily application of 0.12% UF-021 for 4 weeks caused no significant changes in aqueous protein concentration, aqueous flow rate or corneal endothelial permeability. Neither single nor long-term use of topical UF-021 induced irritative responses in the outer segment of the eye. The present study suggests that UF-021 has potential as a safe and effective ocular hypotensive drug with a mechanism of action different from other drugs currently available for the treatment of glaucoma.

Administration, Topical↗

PubMed1990

Time course of changes in aqueous protein concentration and flow rate after oral acetazolamide.

The coefficient of plasma protein entry into the aqueous humor, kin, was calculated in the human eyes from the aqueous protein concentration measured with a flare-cell meter and from the aqueous flow rate determined with fluorophotometry. The value of kin averaged 3.47 +/- 0.25 x 10(-5) min-1 (mean +/- SEM) in 12 eyes of six normal young volunteers. The time course of changes in aqueous protein concentration after oral administration of 500 mg acetazolamide was measured with a flare-cell meter in 24 eyes of 12 subjects. Aqueous protein concentration significantly increased from 2-10 hr postadministration with a maximum increase of 41 +/- 7% (mean +/- SEM) at 6 hr postadministration. Assuming that kin is not affected by the drug treatment, we calculated the time change of aqueous flow rate from that of aqueous protein concentration using the value of kin above. The calculated flow rate after the administration of acetazolamide decreased between 1.25 and 8 hr, with a maximum reduction of 40 +/- 11% at 1.75 hr postadministration. These measurements obtained with the flare-cell meter corresponded well to those obtained by fluorophotometry in a separate group of volunteers given the same treatment. It was shown that oral acetazolamide increases aqueous protein concentration, and that the time change of its effect on aqueous flow rate can be monitored by measuring aqueous protein concentration.

Acetazolamide↗

PubMed1990

[Changes in intraocular pressure and aqueous humor dynamics of normal human eyes after topical application of bunazosin hydrochloride].

The effects of topically applied bunazosin hydrochloride, a recently developed highly selective alpha 1-adrenergic antagonist, on intraocular pressure, pupillary diameter, aqueous protein concentration, anterior chamber volume, aqueous flow rate and tonographic outflow facility were investigated in eight normal human volunteers. A single application of 0.1% bunazosin hydrochloride caused a significant unilateral reduction in the intraocular pressure from 30 minutes through 4 hours after the application, with a maximum decrease of 2.0 +/- 0.5mmHg (mean +/- SEM) below the contralateral control eyes at 2 hours post-application. Neither pupillary diameter, anterior chamber volume nor outflow facility was affected by the drug application. Both aqueous protein concentration measured with a flare-cell meter and aqueous flow rate determined by fluorophotometry were unaltered. The mechanism of intraocular pressure reduction appears to be an increase in uveoscleral outflow and/or a decrease in episcleral venous pressure.

Adrenergic alpha-Antagonists↗

PubMed1990

A new approach to the study of aqueous humor dynamics by measuring the intensity of Tyndall's effect.

A technique is described for studying aqueous humor dynamics by measuring aqueous flare intensity with the laser flare-cell meter. Aqueous flare intensity measured with this instrument was converted into the equivalent human albumin concentration (Ca). A differential equation was given to express the relationship among Ca, aqueous flow rate, plasma protein concentration, anterior chamber volume and the coefficient of entry into the anterior chamber (k(in)) for plasma protein. When k(in) is constant, the time course of changes in aqueous flow rate can be determined from a series of measurements of Ca with the laser flare-cell meter. Using this technique, we assessed the effects of oral acetazolamide on aqueous flow rate. Oral administration of 500 mg acetazolamide decreased aqueous flow rate from 1.25 to 8 hours post-administration, with a maximum reduction of 40% at 1.75 hours post-administration. The validity of this technique was confirmed by comparing the results with those of fluorophotometric measurements. In situations where k(in) is affected by ocular procedures, the time course of changes in k(in) can be monitored by measuring Ca, aqueous flow rate and anterior chamber volume in the same eye. We applied this method to investigate the effects of pilocarpine on the rate of protein entry into the aqueous humor. Single instillation of 1% pilocarpine increased k(in) from 4 to more than 10 hours after the application, with a maximum increase of 37% observed at 9 hours post-application.

Acetazolamide↗

PubMed1990

Aqueous protein concentration in rhegmatogenous retinal detachment.

Changes in aqueous protein concentration (APC) in rhegmatogenous retinal detachment (RD) were investigated. A 6-month prospective study was carried out in 40 unilateral RD patients who underwent scleral buckling procedures with cryotherapy, and a retrospective examination was performed in another 40 patients who had undergone successful retinal reattachment at least 2 years previously. Before the surgery, the APC in the RD eyes was more than twice as high as that in the contralateral control eyes. The surgery caused a further increase in APC, and the peak was observed at the 2nd postoperative week. The APC values decreased to a stable level 3 months postoperatively, but remained significantly higher than those of the control eyes. A statistical analysis revealed the following clinical factors to have a significant correlation with the increase in APC: 1) before surgery, age, extent of RD, balloon-shaped RD, presence of retinal tear rather than hole, and decreased preoperative intraocular pressure; 2) in the early postoperative period, age, size of retinal breaks, and number of cryoapplications; and 3) in the late postoperative period, age, extent of RD, and performance of scleral encircling procedure. These findings would suggest that different mechanisms are responsible for the increase in APC in each period, including 1) a reduction in the aqueous bulk flow; 2) disruption of the blood-retinal barrier caused by cryotherapy, or dispersion of subretinal protein into the vitreous cavity during the surgery; and 3) a decrease in aqueous flow rate following buckling procedures, and alteration of the blood-aqueous barrier function induced by changes in anterior uveal blood circulation.

Adult↗

PubMed1990

[Time course of changes in aqueous protein concentration in rhegmatogenous retinal detachment].

Changes in aqueous protein concentration (APC) in unilateral rhegmatogenous retinal detachment (RD) were investigated 1) prospectively in 40 patients who were undergoing scleral buckling surgery with cryotherapy and 2) retrospectively in another 40 patients who had undergone successful retinal reattachment more than 2 years previously. Before the surgery, APC in RD eyes was more than double that in the contralateral normal eyes. The surgical intervention led to a further increase in APC and a peak was observed at 2 weeks postoperatively. Values decreased to a stable level approximately 3 months after surgery, but remained significantly higher than those of the control eyes. Clinical factors which were found to significantly correlate with APC were: 1) before surgery; age, area of RD, balloon-shaped RD, tear rather than hole, and the extent of preoperative hypotony; 2) in the early postoperative period; age, size of retinal breaks, and number of cryoapplication; and 3) in the late postoperative period; age, area of RD, and performance of scleral encircling. It was suggested that different mechanisms are responsible for the increase in APC observed at different periods, including 1) decreased aqueous bulk flow; 2) disruption of the blood-retinal barrier caused by cryotherapy, and/or dispersion of subretinal protein during the surgeries; and 3) decreased aqueous flow rate following buckling procedures, and breakdown of the blood-aqueous barrier induced by changes in anterior uveal blood circulation.

Aqueous Humor↗

PubMed1989

Quantitative assessment of aqueous flare intensity in diabetes.

Aqueous flare intensity was measured with the laser flare-cell meter in 231 eyes of diabetic patients and 31 eyes of normal age-matched controls. Diabetic patients were divided into four groups based on the degree of retinopathy: (1) non-retinopathy, 42 eyes; (2) background retinopathy, 72; (3) preproliferative retinopathy, 23; and (4) proliferative retinopathy, 94. There was no significant difference between the normal controls and the non-retinopathy group, whereas the rest of the diabetic groups showed significantly higher flare values than did normal controls (P less than 0.001). Flare intensity increased with the progression of retinopathy. Our results demonstrate that clinical use of the flare-cell meter enables the quantitative assessment of blood-aqueous barrier function in diabetics and suggest that diabetic iridopathy, as one of the manifestations of diabetes in the anterior part of the eye, exists even in the early stages of this disease and progresses in parallel with retinopathy.

Aqueous Humor↗

PubMed1989

[Quantitative assessment of aqueous flare intensity and cell count in uveitis].

In an attempt to evaluate the validity of the laser flare-cell meter in in iridocyclitis, we conducted a comparative study of slit-lamp examination and flare-cell meter measurements in 251 eyes of uveitis patients. A significant correlation was observed between the two methods both in the measurement of flare intensity (Kendall tau = 0.580, p less than 0.001) and cell count (tau = 0.390, p less than 0.001). However, there were wide variations in grading within groups and large overlaps in scores between groups. These results were thought to be attributable to differences in the two examination methods. Flare-cell meter demonstrated high sensitivity for flare measurements, while there were some cases where low numbers of cells, which could be observed by a slit-lamp, were undetectable by the flare-cell meter. Patients with Behçet's disease were divided into three groups based on the interval from an ocular attack episode. Flare-cell meter examination revealed that flare intensity values remained abnormally high even in patients free from an attack episode for more than six months prior to the examination (p less than 0.001). It was considered that disruption of the blood-aqueous barrier exists permanently in patients with Behçet's disease.

Adult↗

PubMed1989

Aqueous flare intensity and age.

The influence of aging on the blood-aqueous barrier function was assessed by measuring aqueous flare intensity in 203 normal eyes of healthy human subjects aged 20 to 79 years, using the recently developed laser flare-cell meter. The flare intensity correlated well with age (r = 0.502, Spearman r = 0.503, P = 0.00), and the intensity values in the subjects with their ages in the 6th, 7th and 8th decade were significantly higher than the values in the subjects in their 3rd decade (P less than 0.01).

Adult↗

PubMed1989

[Effect of acetazolamide on aqueous flare in normal human eyes].

A newly developed instrument for the quantitative measurement of aqueous flare, the laser flare-cell meter, is now being introduced clinically. The present experiment was designed to assess the effect of a commonly administered drug, acetazolamide, on measurements obtained in normal, healthy subjects. Control measurements were taken over a 24 hr period, from 0900 hrs to 0900 hrs of the next day in 12 drug-free, normal, healthy subjects. A second, similar time-course measurement was conducted in the same subjects on another day after oral administration of 500 mg acetazolamide. Results revealed that acetazolamide increased aqueous flare from 2 hrs to 10 hrs post-administration. The peak effect was observed approximately 6 hrs after acetazolamide administration, reaching a level 41% greater than that on the control day. Anterior chamber volume and serum protein concentration were not affected by the drug treatment. The use of the laser flare-cell meter in the clinic and possible mechanisms contributing to the effect of the drug are discussed.

Acetazolamide↗

PubMed1989

[Increasing of aqueous flare intensity with aging in normal human eyes].

An attempt was made to evaluate the influence of aging on aqueous flare intensity by measuring 203 normal human eyes. Subjects were divided into six age groups from twenty years to seventy nine years old, and the values for aqueous flare intensity were then determined by a flare-cell meter. Flare values were higher in the older age groups and correlated well with age (linear correlation coefficient r = 0.506, Spearman r = 0.510, p = 0.000). Subjects in their fifties, sixties and seventies showed statistically significant differences to those in their twenties (p less than 0.01). A preliminary in vitro experiment was performed to convert the flare-cell meter reading (photon count/msec) into bovine albumin concentration (mg/dl), which is necessary to compare measurements of different flare-cell meters. The three flare-cell meters employed in this study all showed good linear relationships between photon count and albumin concentration (r = 0.99-1.00), giving converting equations of Y = -0.72 + 0.969 X, Y = -0.68 + 0.958 X, Y = -0.84 + 1.017 X less than Y = log (photon count), X = log (albumin concentration) greater than, respectively. In this report, flare values are expressed in albumin concentrations for each age group, which will then serve as control values in future studies.

Adult↗

PubMed1989

Changes in aqueous flare and cells after mydriasis.

The influence of a commonly used short-acting mydriatic agent, tropicamide-phenylephrine, on aqueous flare intensity and cell number was studied both in postsurgical cases and normal subjects. Measurements with a laser flare-cell meter were carried out in 40 patients who had undergone planned extracapsular cataract extraction with posterior chamber intraocular lens implantation. On the second postoperative day, 20 patients received one drop of a combined solution of 0.5% tropicamide and 0.5% phenylephrine, and the remaining patients received no mydriatic agents. Flare-cell meter measurements in the non-mydriasis group were rather difficult, and measurements in 12 out of 20 (60%) cases were discontinued. In the mydriasis group, flare intensity became significantly lower 2 hours after the application (P less than 0.01) and continued to decrease throughout the rest of the measurement period. The cell counts tended to decrease throughout the period after mydriasis and showed significantly lower values compared to the initial value (P less than 0.01). It was considered that measurements with this instrument in postoperative cases are best performed between 30 minutes to 1 hour after the application of the short-acting mydriatic agents. In normal human eyes, the effects of 0.5% phenylephrine-0.5% tropicamide, 0.4% tropicamide, and 5% phenylephrine on aqueous flare and cells were tested separately. Aqueous flare intensity was significantly decreased by tropicamide-phenylephrine at 1, 1.5 and 2 hours (P less than 0.05), by tropicamide at 1 and 1.5 hours (P less than 0.01), and by phenylephrine at 3 hours (P less than 0.01) after the application, respectively. Values returned to normal following these transient decreases.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

Quantitative assessment of aqueous flare and cells in uveitis.

Validity of the laser flare-cell meter in uveitis was evaluated. A comparative study of slit-lamp examination and flare-cell meter measurements was carried out in the evaluation of iridocyclitis in a total of 251 measurements in patients with uveitis of various etiologies, including Behçet's disease, Vogt-Koyanagi-Harada's disease and sarcoidosis. The data obtained by these two methods showed a significant overall correlation both in the measurement of flare intensity (Kendall tau = 0.580, P less than 0.001) and cell count (tau = 0.390, P less than 0.001). Problems inherent to the slit-lamp examination were marked in terms of wide variations in grading within groups and large overlaps in scores between groups. The flare-cell meter was highly reliable in the measurement of flare intensity; whereas it could not detect low numbers of cells in some cases. Ninety-one eyes of patients with Behçet's disease were divided into three groups based on the interval from the last ocular attack episode. The flare-cell meter examination revealed that values for flare intensity remained abnormally high even in patients free from an attack episode for more than six months prior to the examination. It was considered that deterioration or breakdown of the blood-aqueous barrier function persists in patients with Behçet's disease.

Aqueous Humor↗

PubMed1989

[Aqueous flare and cells after mydriasis in normal human eyes].

The influence of mydriasis on aqueous flare intensity and cell number was investigated in normal human eyes. A mixture of 0.5% phenylephrine and 0.5% tropicamide (Mydrin P) was topically instilled in 173 eyes of normal subjects ranging from 20 to 79 years old, and measurements with a laser flare-cell meter were carried out before and 1 hour after the application. For statistical analysis, subjects were divided into groups based on ten-year age intervals ranging from 20-29 years to 70-79 years. Aqueous flare intensity was significantly decreased by mydriasis in all age groups. Prior to drug application, aqueous cells were observed in none of the cases, while after mydriasis, apparent aqueous floaters appeared in 9.2% of the cases, all of whom were over 40 years of age. Appearance of aqueous floaters following mydriasis was not accompanied by an increase in aqueous flare intensity. Time course of changes in aqueous flare intensity after topical instillation of 5% phenylephrine and 0.4% tropicamide were investigated separately. Tropicamide decreased aqueous flare intensity in normal young human subjects, and values at 1 and 1.5 hours post-application differed significantly from those of the contralateral control eyes. The instillation of phenylephrine in normal young subjects resulted in a significant decrease of aqueous flare at 3 hours post-application. Observed decreases in aqueous flare intensity by a commonly used mydriatic agent, a combined solution of phenylephrine and tropicamide, was considered to be the result of the pharmacological effects of tropicamide.

Adult↗

PubMed1988

Diurnal variation of aqueous flare in normal human eyes measured with laser flare-cell meter.

An attempt was made to detect the diurnal variation of aqueous protein concentration (aqueous flare) in normal human eyes. The laser flare-cell meter, which was recently developed to determine aqueous protein concentration quantitatively in vivo, was employed in the study. A preliminary study was performed to evaluate the reproducibility of aqueous flare measurements with the laser flare-cell meter in normal subjects, giving a reproducibility coefficient of 12.5%. The aqueous flare intensity was found to be high in the morning and low in the evening. The quotient between the highest and the lowest value was 1.32. The findings were considered to represent changes in actual aqueous protein concentration and the possible sources of this fluctuation were discussed.

Adult↗