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Results for “INTRAOCULAR PRESSURE”

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PubMed1993

Refraction changes during elevation of intraocular pressure by suction cup, their reflection in the pattern visual evoked cortical potential and their compensation.

Visual evoked cortical potential studies using pattern stimuli with the intraocular pressure raised artificially by the suction cup method have been reported. Possible changes in the refraction of the eye due to the method employed and their influence on the pattern visual evoked cortical potential have not been considered. Changes in the refraction of the eye during artificial intraocular pressure elevation and the influence of such changes on pattern visual evoked cortical potentials were studied. The refraction changes were found to depend on the shape of the suction cup. They could be compensated for by employing properly shaped suction cups and contact lenses. The behavior of amplitude and latency of the pattern visual evoked cortical potential at artificially elevated intraocular pressure with compensation for refraction changes has been studied and found to depend in a characteristic manner on ocular perfusion pressure.

Adult↗

PubMedDate not supplied

Effect of trabecular aspiration on early intraocular pressure rise after cataract surgery.

PURPOSE: To evaluate the efficacy of a new trabecular aspiration technique on intraocular pressure (IOP) immediately after cataract surgery. SETTING: University Eye Hospital of Cologne, Germany. METHODS: This prospective, double-masked study comprised 48 of 100 patients having extracapsular cataract extraction (ECCE) who were randomly assigned to a study group. In these patients, 180 degrees of the inferior circumference of the chamber angle was treated with negative suction pressure ranging between 100 and 200 mm Hg. The other 52 patients served as a control group. Intraocular pressure was measured preoperatively and early (5 to 7 hours) and late (12 to 48 hours) postoperatively. RESULTS: There was a significant mean increase in IOP from the preoperative to early postoperative period in both the control group (20.8 mm Hg) and the treatment group (7.4 mm Hg). There was no significant difference between preoperative and late postoperative pressures in either group. A one-way analysis of covariance of the changes in pressure from the preoperative to early postoperative period showed significantly less increase (P = .0041) in the aspiration than in the control group. CONCLUSION: Trabecular aspiration was effective in reducing the amount of IOP increase in the immediate period after ECCE.

Aged↗

PubMedDate not supplied

Interocular visual-field and intraocular-pressure asymmetries in normal-tension-glaucoma.

To evaluate the role of intraocular-pressure (IOP) in the pathogenesis of glaucomatous damage in normal-tension-glaucoma, we investigated whether the eye with the higher IOP had more severe visual-field damage in 23 normal-tension-glaucoma patients. Twelve patients did have more severe visual-field defects in the eye with the higher IOP, but 11 had more severe defects in the eye with the lower IOP. There was no correlation either between IOP and visual-field damage (r = 0.16; p = NS) or between the interocular differences in IOP and in visual-field damage (r = 0.21; p = NS). Thus, although intraocular pressure may contribute to glaucomatous damage even in normal-tension-glaucoma patients, other factors must be involved as well.

Adult↗

PubMed1999

Twenty-four-hour pattern of intraocular pressure in the aging population.

PURPOSE: To characterize the 24-hour pattern of intraocular pressure (IOP) in a sample of the aging human population. METHODS: Twenty-one healthy volunteers 50 to 69 years of age were housed in a sleep laboratory for 24 hours. Experimental conditions were strictly controlled with a 16-hour light period and an 8-hour dark period. Sleep was encouraged in the dark period. Intraocular pressure was measured using a pneumatonometer every 2 hours (total of 12 times). Measurements were taken in both the sitting position and the supine position during the light/wake period but only in the supine position during the dark period. RESULTS: When the sitting IOP data from the light/wake period and the supine IOP data from the dark period were considered, elevation and reduction of IOP occurred around the scheduled lights-off and lights-on transitions, respectively. Mean IOP in the dark period was significantly higher than mean IOP in the light/wake period. The trough appeared at the end of the light/wake period, and the peak appeared at the beginning of the dark period. The magnitude of trough-peak difference was 8.6+/-0.8 mm Hg (mean +/- SEM). Cosine fits of 24-hour IOP data showed a significant 24-hour rhythm. When IOP data from just the supine position were analyzed, the trough-peak IOP difference was 3.4+/-0.7 mm Hg, with similar clock times for the trough and the peak. Cosine fits of supine IOP data showed no statistically significant 24 hour rhythm. CONCLUSIONS: Nocturnal elevation of IOP occurred in this sample of the aging population. The trough of IOP appeared at the end of the light/wake period, and the peak appeared at the beginning of the dark period. The main factor in the nocturnal IOP elevation appeared to be the shift from daytime upright posture to supine posture at night.

Aged↗

PubMed2001

Intraocular pressure and gonioscopic findings in rural communities mesoendemic and nonendemic for onchoceriasis, Kaduna State, Nigeria.

PURPOSE: To report on glaucoma-related ocular parameters, namely intraocular pressure and peripheral anterior synechiae, in the presence of onchocercal infection. METHODS: Two computer-generated random samples of individuals were drawn from communities mesoendemic and nonendemic for onchocerciasis respectively. Applanation tonometry and gonioscopy were carried out on these individuals. RESULTS: Four hundred and thirty-six and 319 individuals from the mesoendemic and nonendemic communities were examined respectively. The mean intraocular pressure was 1.58 mmHg lower in the individuals from the mesoendemic communities compared with those from the nonendemic communities (p < 0.001) despite the prevalence of peripheral anterior synechiae being higher in the mesoendemic communities. In these communities, there was strong evidence that the prevalence of peripheral anterior synechiae increased with increasing microfilarial load. CONCLUSIONS: Onchocercal infection produces a low-grade inflammatory process, which may result in a lowering of intraocular pressure despite the formation of peripheral anterior synechiae. Glaucomatous optic nerve damage may therefore not be the primary cause of visual loss in ocular onchocerciasis as this occurs late and is probably preceded by other blinding onchocercal pathology.

Adolescent↗

PubMed1981

[Experimental and clinical examinations of the effect of cryosurgery of intraocular pressure].

Diathermy and cryosurgery have different effects on living tissue. Cell membranes are ruptured by cryosurgery, but the proteins are less affected than by diathermy. A short review of experimental cyclocryosurgery and the clinical results are presented. Data from the literature as well as evaluation of patients confirm that, as yet, the results are not satisfactory. The sequelae of freezing are very different in slow-and fast-freezing procedures. Therefore, the results in rabbits treated with a cryosurgical unit used for retinal detachment surgery (Amoils, -80 degrees C) were compared with the results using a cryoprobe cooled with liquid nitrogen (-180 degrees C). A permanent reduction in intraocular pressure was not achieved using cyclocryotherapy applied with the equipment used for detachment surgery (-80 degrees C). Repeated cryosurgery of this type did not result in a permanent pressure reduction. Histopathology demonstrated that the ciliary epithelium had regenerated and prolongation of the cyclocryotherapy applications did not result in a permanent intraocular pressure reduction. Lens opacities occurred in all rabbits of this series. Application of cryotherapy with a nitrogen-cooled cryoprobe (2.5 mm2 contact area) caused severe damage, resulting in phthisis bulbi. Another nitrogen-cooled probe (contact area of about 1 mm2 diameter) resulted in a permanent reduction in intraocular pressure, but the anterior parts of the lens became opaque. Histopathology revealed total necrosis of the ciliary epithelium and the basal membrane. Three months after cyclocryotherapy of this type the ciliary processes were atrophic and covered with connective tissue and regeneration of epithelial cells was not found in areas of such cryotherapy scars. Further experiments have been commenced including a reduction of application time, in order to find the optimum application technique resulting in permanent intraocular pressure reduction and the fewest possible side effects.

Animals↗

PubMed2000

Effect of oral losartan potassium administration on intraocular pressure in normotensive and glaucomatous human subjects.

The effects of the type 1 angiotensin II receptor antagonist Losartan potassium on intraocular pressure (IOP) were studied. Four groups of subjects were analysed: group A, ten controls; group B, ten patients with essential arterial hypertension and with IOP within the normal range; group C, ten patients with primary open angle glaucoma (POAG), but without essential arterial hypertension; group D, ten patients with arterial hypertension and POAG. The study design was held in a randomized crossover double-blind fashion. Systolic and diastolic arterial pressure, heart rate, pupil diameter, IOP and total outflow facility were recorded at baseline and at 1 hr intervals up to 6 hr, following the oral administration of 50 mg of Losartan potassium and/or placebo. The alternative treatment was given a week later. Drug administration significantly reduced IOP in all subjects. No variation in heart rate and pupil diameter was observed during the follow-up period. Blood pressure dropped only in arterial hypertensive patients (groups B and D). Total outflow facility increased significantly in all groups. Placebo did not induce any variation in all groups. These findings demonstrate that the mechanism by which Losartan potassium reduces intraocular pressure is not mediated by a decrease in blood pressure, but rather it is more specific, confirming the role of the renin-angiotensin system also in the regulation of intraocular pressure in man.

Adult↗

PubMed1997

Effects of changes in intraocular pressure on human ocular haemodynamics.

PURPOSE: Myogenic autoregulation is the ability of a vascular bed to maintain blood flow despite changes in perfusion pressure. Ocular perfusion pressure is defined as the difference between ocular arterial pressure and ocular venous pressure, the latter dependent on intraocular pressure (IOP). The aim of the present study was to investigate the effect of moderate increases in IOP on ocular haemodynamics. METHODS: Changes in IOP (+ 10 mmHg, +20 mmHg) were induced by a suction cup in 10 healthy subjects. Ocular fundus pulsations in the macula and the optic disc were measured by laser interferometry; blood flow velocities in the central retinal artery (CRA) and in the ophthalmic artery (OA) were measured by Doppler sonography. RESULTS: Changes in IOP caused a significant reduction in fundus pulsations, which was more pronounced in the macula (at +10 mmHg: -9 +/- 2%, p < 0.01; at +20 mmHg: -19 +/- 3%, p < 0.001) than in the optic disc (at +10 mmHg: -5 +/- 2% (ns); at +20 mmHg: -9 +/- 3%, p < 0.01). Mean flow velocity in the CRA was reduced by -5 +/- 3% at +10 mmHg (ns) and by -14 +/- 5% at +20 mmHg (p < 0.005), resistive index was increased by +4 +/- 1% at +10 mmHg (p < 0.05) and by +6 +/- 2% at +20 mmHg (p < 0.01). In contrast, a rise in IOP did not affect blood flow parameters in the OA. CONCLUSIONS: Our results from fundus pulsation measurements indicate that choroidal blood flow decreases when IOP is increased. The Doppler sonographic findings in the CRA indicate reduced blood flow velocity in this artery during raised IOP.

Adult↗

PubMed2005

Dynamic contour tonometry for intraocular pressure measurement.

PURPOSE: To compare dynamic contour tonometry as a new method for intraocular pressure measurement with Goldmann applanation tonometry. DESIGN: Clinical observational study. METHODS: The study included 176 eyes of 126 subjects (39 eyes with open-angle glaucoma, 137 normal eyes) and consisted of 528 dynamic contour measurements and 352 Goldmann tonometry measurements. Corneal pachymetry measurements were additionally performed. RESULTS: Mean dynamic contour tonometric measurements (18.71 +/- 5.90 mm Hg) were significantly (P < .001) higher than mean applanation tonometric values (16.98 +/- 5.86 mm Hg), correlating significantly with each other (r(2) = .905, P < .001). The slope of the regression line was 0.95. Correlation with central corneal thickness was significant for applanation tonometry (P = .036), while dynamic contour tonometry was statistically independent of corneal thickness (P = .32). CONCLUSIONS: For measurement of intraocular pressure, dynamic contour tonometry may offer a new technology, which, compared with applanation tonometry, may show a lower dependence on central corneal thickness.

Adolescent↗

PubMed2000

Accuracy of clinical estimates of intraocular pressure in Chinese eyes.

PURPOSE: To investigate the validity of clinical estimates of intraocular pressure (IOP) in Chinese people. DESIGN: Prospective, cross-sectional, hospital-based in vivo study. PARTICIPANTS: Twenty-three ethnic Chinese adults (aged 35-82 years) undergoing routine phacoemulsification surgery were examined. TESTING: "True" IOP was measured with a solid-state hemodynamic monitor through a cannula in the anterior chamber. IOP was set successively to 10, 20, and 30 mmHg in each subject, using a reservoir of balanced salt solution. Intraocular pressure was simultaneously estimated by use of a hand-held applanation tonometer (Perkin's) and a Tono-Pen. The association between ocular biometric variables and measurement error was examined. MAIN OUTCOME MEASURES: The median of three readings at each IOP level was taken as the IOP estimate of each instrument. Measurement error was calculated as the mean difference (tonometer minus direct measurement). RESULTS: The error for the hand-held applanation tonometer was -1.6, -4.3 and -5.7 at 10, 20, and 30 mmHg, respectively. For the Tono-Pen the measurement error was +0.4, -2.0, and -4.1 at 10, 20, and 30 mmHg, respectively. We could identify no association between measurement error and corneal thickness or curvature, anterior chamber depth, or axial length. CONCLUSIONS: The applanation tonometer and Tono-Pen underestimate the true IOP in Chinese eyes. Error increases as true IOP increases. These tonometers do not give an accurate estimate of IOP in East Asians.

Adult↗

PubMed2006

[Intraocular pressure and corneal thickness. A comparison between non-contact tonometry and applanation tonometry].

OBJECTIVE: Corneal thickness and deformation seem to have a considerable influence on intraocular pressure measurement. Due to differences in the corneal deformation in either non-contact tonometry or applanation tonometry, both methods should be compared in the same patient group depending on central corneal thickness. METHODS: In 106 eyes of 55 patients (18 males, 37 females, age 17-89 years, mean 63.3 years) with glaucoma and central corneal thickness between 409 and 644 microm (Orbscan II pachymetry) intraocular pressure was measured in each eye with non-contact tonometry (Reichert AT550) and 30 min later with Goldman applanation tonometry. RESULT: Non-contact tonometry as well as applanation tonometry showed a positive correlation between measured intraocular pressure and corneal thickness. The steepness of the line of regression was 0.33 mmHg per 10 microm of corneal thickness in non-contact tonometry and 0.17 mmHg per 10 microm of corneal thickness in applanation tonometry. CONCLUSION: Independently of the large differences in individual pressure measurements between non-contact tonometry and applanation tonometry, we found higher IOP values with non-contact tonometry in thicker corneas as compared with applanation tonometry. In thinner corneas there was a better correspondence between both methods. Thus, it seems very likely that corneal rigidity increases with corneal thickness.

Adolescent↗

PubMed1988

Effect of the calcium antagonist nifedipine on intraocular pressure in normal subjects.

We studied the effects of nifedipine, a calcium antagonist, given intravenously and orally, on intraocular pressure in six normal volunteers. Nifedipine had no effect on intraocular pressure. Nifedipine is not contraindicated for the treatment of cardiovascular disease in glaucomatous patients and may have theoretical advantages in this situation, which are discussed.

Administration, Oral↗

PubMed1987

Effects of increasing enflurane concentrations on intraocular pressure.

The effects of enflurane at various concentrations on intraocular pressure (IOP) were studied. In 15 healthy patients, intubated and mechanically ventilated, IOP was measured the day before surgery, after premedication and during anaesthesia, after administration of 0.5%, 1.0% or 1.5% enflurane. Enflurane in combination with general anaesthesia and controlled ventilation (PCO2 4.7-5.3 kPa) caused a significant decrease in IOP. The decrease was more marked (44%) with 1% enflurane than with 0.5% enflurane (21%). The change in IOP was comparable with 1.0% and 1.5% enflurane; however, systolic arterial pressure decreased more with enflurane 1.5%. Increasing the inspired concentration of enflurane from 1% to 1.5% did not appear to be associated with any further decrease in IOP.

Adult↗

PubMed1988

Intraocular pressure increase associated with epsilon-aminocaproic acid therapy for traumatic hyphema.

We treated five patients receiving epsilon-aminocaproic acid who demonstrated sudden and accelerated clot dissolution with accompanying increases in intraocular pressure 24 to 96 hours after discontinuing treatment. All of these patients required additional ocular hypotensive medications and one patient required anterior chamber washout for persistently increased intraocular pressure. These findings suggest that certain patients with hyphema may be at risk for significant intraocular pressure increases following cessation of epsilon-aminocaproic acid therapy.

Adolescent↗

PubMed2003

The effect of latanoprost, brimonidine, and a fixed combination of timolol and dorzolamide on circadian intraocular pressure in patients with glaucoma or ocular hypertension.

OBJECTIVE: To compare the circadian intraocular pressure (IOP) reductions induced by latanoprost, brimonidine tartrate, and a fixed combination of timolol maleate and dorzolamide hydrochloride in patients with primary open-angle glaucoma (POAG) or ocular hypertension (OHT). METHODS: In this crossover study, 10 patients with POAG and 10 with OHT were treated with latanoprost once a day, brimonidine twice a day, and a fixed combination of timolol and dorzolamide twice a day for 1 month. Four 24-hour tonometric curves were obtained for each patient. Intraocular pressure (IOP) was measured at 3, 6, and 9 AM, and at noon and at 3, 6, and 9 PM, and at midnight, using a handheld electronic tonometer with the patient in supine and sitting positions and a Goldmann applanation tonometer with the patient sitting at the slitlamp. MAIN OUTCOME MEASURE: Reduction of circadian IOP. RESULTS: All the drugs significantly reduced IOP compared with the baseline at all times, except for brimonidine at midnight, 3 AM, and 6 AM. Latanoprost was more effective than brimonidine in lowering IOP at 3 and 6 AM and at 3 PM (P=.03), and the combination of timolol and dorzolamide was more effective than brimonidine at 3 and 9 AM (P=.04) and at 3 and 6 PM (P =.05) and more effective than latanoprost at 9 AM (P=.05). CONCLUSION: Latanoprost and the fixed combination of timolol and dorzolamide led to similar circadian reductions in IOP, whereas brimonidine was less effective, particularly during the night.

Antihypertensive Agents↗

PubMed2006

Increase of peak intraocular pressure during sleep in reproduced diurnal changes by posture.

OBJECTIVE: To characterize diurnal intraocular pressure (IOP) changes in primary open-angle glaucoma by reproducing IOPs based on patient posture. METHODS: In 148 patients with untreated primary open-angle glaucoma who had IOPs recorded during clinic hours that were less than 21 mm Hg (average, 14.8 +/- 3.2 mm Hg), we measured IOP by noncontact tonometry every 2 hours from 6 am to midnight and every 3 hours from midnight to 6 am with patients sitting and supine. The IOP was reproduced by designating the sitting IOP as measurements taken when the patient was awake and the supine IOP as measurements taken when the patient was asleep for each individual. The reproduced diurnal IOP was composed of 12 measurements that included 2 to 4 IOP levels measured with the patients supine and the rest while they were sitting. RESULTS: The peak of sitting diurnal IOP (mean +/- SD) for 148 patients was 16.0 +/- 2.7 mm Hg, which was significantly lower than the peak of supine IOP (18.9 +/- 3.9 mm Hg) or the reproduced IOP (17.5 +/- 3.6 mm Hg) (P<.001 for both comparisons). The average reproduced IOP at each measurement time peaked at 3 am during sleep; with sitting diurnal IOP or supine diurnal IOP, the peak IOPs were at noon. Twenty-nine patients (20%) with an IOP less than 21 mm Hg during clinic hours had a reproduced IOP of 21 mm Hg or greater while asleep, compared with only 5 patients (3%) when the patients were sitting only. CONCLUSIONS: In patients with primary open-angle glaucoma and IOPs less than 21 mm Hg during clinic hours, 20% of patients had a reproduced IOP of 21 mm Hg or greater, compared with only 3% who had an IOP of 21 mm Hg or greater while sitting. Intraocular pressures peaked in most patients during sleep.

Adolescent↗

PubMed1983

Nitrous oxide increases intraocular pressure after intravitreal sulfur hexafluoride injection.

In anesthetized cats ventilated with oxygen, 0.5 ml of the inert gas sulfur hexafluoride (SF6) was substituted for vitreous. When the ventilating gas was changed to nitrous oxide (N2O) 66%, balance oxygen, intraocular pressure increased from 14.4 to 30.3 mmHg in 19.5 min. When the ventilating gas was changed back to oxygen, intraocular pressure decreased from 29.1 to 12.0 mmHg in 18.1 min. This intraocular pressure change secondary to gas volume alteration may adversely affect therapeutic outcome of ophthalmic surgery. Accordingly, N2O should be avoided in patients during and following intravitreal injection of SF6 for up to 10 days.

Anesthesia↗

PubMedDate not supplied

[Variations in intraocular pressure in normal-pressure glaucoma and in hypertensive open-angle glaucoma].

The comparative study of the intraocular pressure variations at patients with low-tension glaucoma and hypertensive open-angle glaucoma reveals some common modifications regarding the aspect of the nictemeral levels of intraocular tension (the maximal variation of the nictemeral curve, the time of maximal intraocular pressure, variability) and the aspect of the provocative testes. The nictemeral curves and the provocative testes are used at the patients suspects of low-tension glaucoma both for diagnose and to eliminate the incipient open-angle glaucoma with one tensional pick.

Disease Progression↗