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At least 127 records · Page 7Linked to original sources
PubMed1995

The role of the ocular lens in the regulation of intraocular pressure.

The relationship between lenticular colloid osmotic (oncotic) pressure and intraocular pressure is discussed, with particular reference to a postulated buffering reservoir action of the lens in protecting against acute changes in intraocular pressure. A hypothesis is developed regarding acute lenticular volume changes in those species manifesting change in lens shape during accommodation. The unusually high colloid osmotic pressure of fish lenses is discussed and related to their unique means of accommodation and their susceptibility to cataract formation.

Accommodation, Ocular↗
PubMedDate not supplied

[Effectiveness of convex ophthalmocompression in the course of combined preoperative treatment aimed at decrease of intraocular pressure before extracapsular cataract extraction with intraocular lens implantation].

Two groups of patients with cataracts of different origin (a total of 110) are compared, in whom intraocular pressure was decreased by different methods before surgery: mechanical (convex compression) and combined (convex compression combined with hypotensive drugs). The decrease of intraocular pressure depended on the coefficient of intraocular fluid discharge easiness. Time course of intraocular pressure during and after convex compression is analyzed.

Acetazolamide↗
PubMed1976

[Role of mechanical properties of the external ocular membrane in the dynamics of intraocular pressure].

Changes of the intraocular pressure in alterations of the central arterial pressure are an accepted fact. Disbalance of the above changes occurring at that is considered to be a display of active regulatory mechanisms. In this study, comparison of the pulse waves and short--term changes of arterial pressure with oscillations of the intraocular pressure occurring at that, has been made. Analysis of all the changes was made with the aid of a mathematical model. Amplitude--phasic characteristics of the eye membrane were studied for ascertaining of effect of different factors on the amplitude and form of the intraocular pressure pulse waves. In experimental conditions, the differences in dynamics of the level and in form of the pulse oscillations between the central arterial and the intraocular pressures were shown to be due not to functioning of active regulatory mechanisms but to the elastic--viscous features of the eye membrane.

Animals↗
PubMed1980

A scleral buckle pressure gauge for continuous monitoring of intraocular pressure.

An implantable variable resistance pressure gauge has been constructed from a conductive elastomere in the form of a scleral buckle which is suitable for recording intraocular pressure in vivo continuously over an indefinite period of time. The similarity of the pressure transducer to the standard scleral buckles used to reduce retinal detachments suggests that it will be tolerated over a period of years without significant effect on intraocular pressure. The electrical output from these pressure gauges appears to be both well defined and of sufficient magnitude to operate a valve to control intraocular pressure.

Animals↗
PubMed1997

Measurement of intraocular pressure after epikeratophakia.

AIMS: To assess the accuracy of three commonly used tonometers in eyes after epikeratophakia. METHODS: Five eye bank eyes with sutured epikeratophakia buttons were connected to a manometer and a pressure transducer. Intraocular pressure was adjusted in 5 mm Hg increments from 0 to 50 mm Hg. The intraocular pressure was measured at each increment using a Goldmann tonometer, a pneumatonometer, and a Tono-pen. RESULTS: The difference between the manometer (actual pressure) and the Goldmann tonometer ranged from -19 to +9 mm Hg (mean (SD) overestimation 2.6 (5.8) mm Hg). The pneumatonometer error ranged from -27.5 to +5.5 mm Hg (mean (SD) overestimation 4.7 (6.1) mm Hg), and for the Tono-pen the range was -18 to +11 mm Hg (mean (SD) overestimation 0.05 (7.9) mm Hg). The correlation coefficients for the three tonometers were 0.94, 0.92, and 0.87 for the Goldmann tonometer, pneumatonometer, and Tono-pen respectively. CONCLUSION: The Goldmann tonometer had the best correlation with the manometer in eye bank eyes with epikeratophakia (correlation coefficient 0.94), but none of the tonometers was accurate over the entire range of pressures tested. Detection of glaucoma in eyes with epikeratophakia cannot rely on tonometry alone, but requires examination of the optic nerve and visual field.

Case-Control Studies↗
PubMedDate not supplied

Effects of the application of neck pressure by a collar or harness on intraocular pressure in dogs.

The effect on intraocular pressure (IOP) from dogs pulling against a collar or a harness was evaluated in 51 eyes of 26 dogs. The force each dog generated while pulling against a collar or a harness was measured. Intraocular pressure measurements were obtained during application of corresponding pressures via collars or harnesses. Intraocular pressure increased significantly from baseline when pressure was applied via a collar but not via a harness. Based on the results of the study, dogs with weak or thin corneas, glaucoma, or conditions for which an increase in IOP could be harmful should wear a harness instead of a collar, especially during exercise or activity.

Animal Husbandry↗
PubMed1975

The influence of tropicamide on intraocular pressure.

Elevation of intraocular pressure by many cycloplegic drugs has been reported to occur in eyes in which the filtration angle remained open during mydriasis. Tropicamide 1% is also capable of this phenomenon in patients with open angle glaucoma who are being medicated with pilocarpine. However, in normal eyes as well as those with untreated open angle glaucoma, this cycloplegic has a relatively small effect on intraocular pressure. It is postulated that this difference between the subject groups may be due to competitive inhibition of the miotic at the receptor site in those treated with pilocarpine. In 3 patients in whom the intraocular tension elevation was found to be quite marked, heavy pigments showers in the anterior chamber occurred which suggested an outflow obstructive phenomenon similar to that seen in "Pigmentary Glaucoma."

Amides↗
PubMed1987

[Comparative study of the effect of muscle relaxants on the intraocular pressure].

Control of intraocular pressure is a major concern in ophthalmic anesthesia, especially in the presence of glaucoma or penetrating eye injury. The use of succinylcholine under these conditions is controversial. This study was undertaken to assess the effects of the neuromuscular blocking agents succinylcholine, pancuronium, metocurine, vecuronium, and atracurium on the intraocular pressure of dogs. The study was performed on five "conditioned" mature male foxhounds. The dogs were intubated immediately after induction with thiopental 10 mg/kg and ventilated with an O2/N2O mixture (FIO2 = 0.33). The ventilation was controlled to maintain an endtidal CO2 concentration of 5 vol.%. and anesthesia maintained with a fentanyl infusion of 10 micrograms/kg per hour. Direct and continuous measurements were taken of blood pressure (MAP), central venous pressure (CVP), and intra-ocular pressure (IOP), the latter via a 22-gauge needle inserted into the anterior chamber of the eye. A force-displacement transducer was attached to the hindpaw to monitor muscle twitch following supramaximal stimulation of the anterior tibial nerve. These four measurements were displayed on a multi-channel polygraph (Figs. 1 and 2). Control values were obtained and then succinylcholine 1 mg/kg, pancuronium 0.1 mg/kg, metocurine 0.3 mg/kg, vecuronium 0.1 mg/kg, or atracurium 0.4 mg/kg were given in a randomized fashion and on different days. Measurements of heart rate (HR), MAP, CVP, and IOP were noted at 2, 5, 10, 20, and 30 min after giving the neuromuscular blocking agent. The results, as displayed on the polygraphy, indicate that the least effect on IOP and cardiovascular state followed neuromuscular blockade with vecuronium and atracurium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

Mean intraocular pressure in Ghanaians.

Intraocular pressure (IOP) was measured in 600 Ghanaians by applanation. They were aged 16 to 77 years with a mean age of 36 years and standard deviation of 12.91. Nineteen subjects (3%) were found to have glaucoma. Five hundred and forty-five qualified for analysis of IOP in non-glaucomatous eyes. The IOP in the latter ranged from 5 to 28 mmHg with a mean of 15.5, median 16, and standard deviation 3.70. The graph of mean IOP is slightly skewed to the right. The 95% confidence interval for mean intraocular pressure for the population is 15.3 to 15.7. The graph of IOP by age showed a slight drop in IOP after the 50-55 year age group. There was no significant difference between mean IOP in males and females (t statistic = 0.17, p > 0.5).

Adolescent↗
PubMed1991

The effect of Perkins, Tono-Pen, and Schiötz tonometry on intraocular pressure.

We studied the intraocular pressure changes produced in five eye bank eyes by Perkins, Tono-Pen, and Schiötz tonometry performed by experienced and inexperienced personnel. When all users were considered together, Perkins tonometry produced a mean intraocular pressure increase of 0.7 mm Hg, significantly less than the mean increase of 12.1 mm Hg produced by Tono-Pen tonometry (P less than .05) or the mean increase of 16.5 mm Hg produced by Schiötz tonometry (P less than .01). There was no statistically significant difference between the intraocular pressure increase produced by Tono-Pen or Schiötz tonometry. Tonometry performed by inexperienced Tono-Pen users and experienced or inexperienced Schiötz users produced a significantly greater increase in intraocular pressure than that performed by experienced Tono-Pen users (P less than .05), and an extremely significant increase compared to tonometry performed by experienced or inexperienced Perkins users (P less than .01). The marked increase in intraocular pressure produced by Tono-Pen tonometry suggests that hand-held electronic applanation tonometers should be used with caution in eyes with a weakened cornea or sclera.

Humans↗
PubMed1977

Adrenergic activity and intraocular pressure.

Systemically-administered noradrenaline lowers intraocular pressure; isoproterenol, similarly administered, has an intraocular pressure-raising effect. Unless extremely low doses are used, these effects will be marked by opposite changes in arterial perfusing pressure. Intraocular pressure-regulating mechanisms carry both alpha- and beta-receptors. Stimulation of alpha-receptors decreases intraocular pressure, while stimulation of beta-receptors increases intraocular pressure. Intraocular pressure is under tonic sympathetic influence.

Abducens Nerve↗
PubMed1984

Aqueous humour turnover and intraocular pressure during menstruation.

Both intraocular pressure and aqueous humour turnover rate were determined at intervals over three months in three females in order to investigate whether a correlation existed between these variables and the menstrual cycle. Not only was there a lack of correlation between intraocular pressure or aqueous humour flow rate and menses but intraocular pressure and aqueous humour flow rate were also not related to each other. If pharmacologically administered doses of progesterone or oestrogen influence intraocular pressure, the present data indicate that the effect is probably mediated through effects on the aqueous outflow pathways.

Adult↗
PubMed1997

Reduced intraocular pressure after phacoemulsification and posterior chamber intraocular lens implantation.

PURPOSE: To ascertain whether phacoemulsification with posterior chamber intraocular lens (IOL) implantation causes long-term reduction in intraocular pressure (IOP). SETTING: Private practice, Kempten, Germany. METHODS: Intraocular pressure was measured in both eyes of 120 consecutive patients who were unilaterally phakic after phacoemulsification a mean of 17 months +/- 17 (SD) previously. Mean age of the 36 men and 84 women was 76 +/- 10 years. Data were analyzed using binomial distribution and the Wilcoxon signed-rank test. RESULTS: The median ratio of IOP in the pseudophakic eye to IOP in the phakic eye was 0.83. The IOP was lower in the pseudophakic eye in 96 patients (80%). The median IOP was 12 mm Hg in the pseudophakic eyes and 14 mm Hg in the phakic eyes (P < .001). As measured by the interquartile range, IOP distribution was more centered in the pseudophakic than in the phakic eyes (3 versus 4). The IOP in the pseudophakic eyes remained lower to the last measurement, 5 years postoperatively, and appeared to be independent of patient age. Lower IOP in the pseudophakic eye was consistently present in patients with higher IOP in the phakic eye (16 to 22 mm Hg). CONCLUSION: Phacoemulsification with posterior chamber IOL implantation reduced IOP in most but not all patients with a preoperative IOP of 22 mm Hg or less. This reduction was maintained over several years, with the cause yet to be established. Lower IOP may decrease the risk of subsequent glaucomatous nerve damage in these patients.

Aged↗
PubMed1986

Possible mechanisms underlying the differential effects of selective inhibitors of type A and type B monoamine oxidase on intraocular pressure in the cat.

Intraocular pressure and facility of aqueous outflow were measured in adult cats after topical application of clorgyline, a selective inhibitor of type A monoamine oxidase (MAO), or deprenyl, a selective inhibitor of type B of the enzyme. Clorgyline produced a dose-related lowering of intraocular pressure which was associated with a dose-related increase in outflow facility. Sympathetic denervation markedly reduced both these effects of clorgyline. Both effects, on the other hand, persisted after death of the animals. Deprenyl did not lower intraocular pressure; in fact, a tendency toward pressure elevation was apparent 2 hours after its administration. Outflow facility was not significantly changed. These results suggest that an endogenous substrate of type A MAO, presumably norepinephrine, is responsible for the ocular tension lowering effect of clorgyline. Because cessation of circulation after death did not abolish the effect, it is assumed that the trabecular meshwork is the site of action and that sympathetic innervation normally supplies an adrenergic neurotransmitter to the meshwork area. The tendency toward rise in intraocular pressure produced by deprenyl is probably due to alteration of aqueous humor formation rather than to a change in outflow resistance.

Animals↗