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PubMed2005

Intraocular pressure during lumbar disc surgery in the knee-elbow position.

Increased intraocular pressure is often implicated in the aetiology of postoperative visual impairment. Such an increase in intraocular pressure has been demonstrated in the prone position. We investigated intraocular pressure in seven patients undergoing lumbar disc surgery in the knee-elbow position with the head resting on a cushion and turned to the side. Measurements were performed in the supine position before induction of anaesthesia and in the knee-elbow position after surgery with the patient still anaesthetised. After a mean (SD) duration of prone positioning of 121 (18) min, mean (SD) intraocular pressure in the nondependent eye was unchanged when compared to the awake state (17.7 (2.4) mmHg vs 18.9 (5.5) mmHg), whereas the intraocular pressure in the dependent eye had significantly decreased (17.0 (3.6) mmHg vs 8.1 (1.8) mmHg; p < 0.01). These results may be important for choosing the optimal position for spinal surgery when an increase in intraocular pressure should be avoided.

Adult↗
PubMed1990

Effect of high PaCO2 and time on cerebrospinal fluid and intraocular pressure in halothane-anesthetized horses.

The effects of different arterial carbon dioxide tensions (PaCO2) on cerebrospinal fluid pressure (CSFP) and intraocular pressure (IOP) were studied in 6 male halothane-anesthetized horses positioned in left lateral recumbency. Steady-state anesthetic conditions (1.06% end-tidal halothane concentration) commenced 60 minutes following anesthetic induction with only halothane in oxygen. During atracurium neuromuscular blockade, horses were ventilated, and respiratory rate and peak inspiratory airway pressure were maintained within narrow limits. The CSFP and IOP were measured at 3 different levels of PaCO2 (approx 40, 60, and 80 mm of Hg). The PaCO2 sequence in each horse was determined from a type of switchback design with the initial PaCO2 (period 1), established 30 minutes after the commencement of steady-state anesthesia, being repeated in the middle (period 3) and again at the end (period 5) of the experiment. Measurements taken from the middle 3 periods (2, 3, and 4) would form a Latin square design replicated twice. The interval between each period was approximately 45 minutes. Data from periods 2, 3, and 4 indicated that CSFP (P less than 0.05) and mean systemic arterial pressure increased significantly (P less than 0.05) with high PaCO2. Mean central venous pressure, heart rate, and IOP did not change significantly during these same conditions. Measurements taken during periods 1, 3, and 5 were compared to assess the time-related responses to anesthesia and showed a significant increase in CSFP, a significant decrease in mean central venous pressure, and a small (but not statistically significant) increase in mean systemic arterial pressure.

Animals↗
PubMed1978

Ketamine anesthesia and intraocular pressure.

We studied the influence of intramuscular ketamine-narcosis on the intraocular pressure of rabbits. Tonography and indirect arterial pressure measurements were performed 5 to 10 minutes after the administration of the agent. The systolic arterial pressure did not change significantly, whereas the intraocular pressure significantly increased. The intraocular pressure increase was 7% on the average with a maximal increase of 20%. In more than half of the cases the arterial and intraocular pressures changed in the opposite directions which speaks for the role of other factors in enhancing these pressure alterations.

Anesthesia, General↗
PubMed1985

Intraocular pressure, ocular pulse pressure, and body position.

Intraocular pressures (IOP's) were measured using the Digilab Pneuma-tonometer with the subject in both the sitting and supine positions. The IOP with the Pneuma-tonometer was greater (17.03 mm Hg) in the supine position than in the sitting position (12.90 mm Hg). The IOP measured with the Pneuma-tonometer, with the subject sitting, was similar to the IOP measured with the Goldmann applanation tonometer (13.42 mm Hg). Inasmuch as IOP tends to be lower with the patient in a sitting position, the clinician should be alert to the possibility that some patients with borderline Goldmann IOP's may have pressures well above the normal range when they are lying down. Due to the continuous recording provided by the Pneuma-tonometer, the ocular pulse pressure can be measured. We found a mean ocular pulse pressure amplitude of 1.77 mm Hg. All values are shown plus or minus 1 SD. Comparison of the ocular pulse pressure amplitude for the two eyes could aid in detecting patients with suspected carotid artery stenosis.

Adult↗
PubMed1996

Correlation between intraocular pressure and CD4+ T-lymphocyte counts in patients with human immunodeficiency virus with and without cytomegalovirus retinitis.

PURPOSE: To determine the intraocular pressure in patients with human immunodeficiency virus (HIV) with and without cytomegalovirus retinitis, and to correlate intraocular pressure with CD4+ T-lymphocyte count and the presence, extent, and activity of cytomegalovirus retinitis. METHODS: Intraocular pressure was measured with calibrated Goldmann applanation tonometers in two groups of patients. Group A included 84 patients with HIV (120 eyes) with cytomegalovirus retinitis, and Group B included 110 patients with HIV (183 eyes) without cytomegalovirus retinitis. Thirty-three patients without HIV (66 eyes) were included as a control group. Step-wise regression analysis of intraocular pressure included correlation with cytomegalovirus retinitis (presence, extent, and activity), CD4+ T-lymphocyte count, age, and gender. RESULTS: The mean intraocular pressure was 9.8 mm Hg in Group A, 12.6 mm Hg in Group B, and 16.1 mm Hg in the control group. All three groups were statistically different from each other when intraocular pressure was compared (P < .0001). Step-wise regression showed that low CD4+ T-lymphocyte count (r2 = .20; P < .0001) and extent of cytomegalovirus retinitis (r2 = .08; P = .007) both correlated to low intraocular pressure. CONCLUSION: Intraocular pressure is lower than normal in patients with HIV. Decreased CD4+ T-lymphocyte count is the major association with low intraocular pressure (20% of the effect); extent of cytomegalovirus retinitis accounts for 8% of the effect. Knowledge of the normal range of intraocular pressure in patients with HIV will be important to the understanding and treatment of glaucoma and other disorders or treatments affecting intraocular pressure.

Adult↗
PubMed1994

The influence of the incision length on the early postoperative intraocular pressure following cataract surgery.

In a prospective study we recorded the early postoperative intraocular pressure of 60 eyes following phacoemulsification and posterior chamber lens implantation. In 30 patients each the implantation either of a folded polyHema intraocular lens through a 3.5 mm incision or of a polymethylmetacrylate intraocular lens through a 7 mm incision was performed. Healon was used in all eyes and thoroughly evacuated from the capsular bag behind the implanted lens and the anterior chamber. For intraoperative miosis 0.5 ml acetylcholine chloride was injected into the anterior chamber after wound closure. Intraocular pressure was measured preoperatively as well as six hours, 18 hours, one week and two months postoperatively without the influence of antiglaucomatous medication. We found no statistically significant change of intraocular pressure at any measurement time in the 3.5 mm group (Student's t-test, p > 0.1). In the 7 mm group only the rise of intraocular pressure at 18 hours was statistically significant (p < 0.05, student's t-test). The comparison of the changes of intraocular pressure from preoperative values between both groups revealed a statistically significant difference at 18 hours (p < 0.05, student's t-test) but not at any other time recorded. Intraocular pressure exceeding 22 mmHg was found at 6 hours in 4 (13.3%) patients of both groups and at 18 hours in 3 (10%) eyes of the 3.5 mm group and 5 (16%) eyes of the 7 mm group (p > 0.1, Fisher's Exact Test). From these results we conclude that 1) regardless of the wound size the pressure rising effect of Healon is successfully counteracted by the aspiration technique described, and 2) with small-incision cataract surgery statistically significant less changes of intraocular pressure are observed in the early postoperative period.

Acetylcholine↗
PubMed1976

Glucocorticoids and intraocular pressure: an experimental study.

The state of intraocular pressure and aqueous humor dynamics as well as histomorphologic and histochemical change of the eye tissues as a result of administration of glucocorticoids were studied in 62 rabbits. After administration of glucocorticoids by instillations and subconjunctival injections there was a trend toward increased intraocular pressure but no statistically significant change in the intraocular pressure was demonstrated. When glucocorticoids were administered for 1 month, a significant increase in production and outflow of aqueous humor was established. Continuation of the experiments for 2 months or longer was accompanied by a significant decrease of the outflow facility coefficient and inhibition of aqueous humor formation. Histologic and histochemical examinations of the eyes of the rabbits studied for 2 months revealed marked dystrophic changes in the trabecular meshwork tissues.

Animals↗
PubMed1999

The effect of intraocular pressure on human and rabbit scleral permeability.

PURPOSE: The purpose of this study was to evaluate the effects of intraocular pressure on the permeability of human and rabbit sclera to water, dexamethasone, and carboxyfluorescein. METHODS: Scleral sections excised from moist-chamber-stored human globes or eyes obtained from euthanatized New Zealand White rabbits were mounted in a perfusion chamber that can create a transscleral pressure that simulates an intraocular pressure. A small depot of drug (100 microl) was added to the episcleral surface while perfusing an irrigating solution slowly across the choroidal side. The perfusate was collected and scleral permeability calculated. Experiments were performed at 0, 15, 30, and 60 mm Hg for each compound in human and rabbit tissue. RESULTS: Analysis of variance showed a significant effect of intraocular pressure on both human and rabbit scleral permeability. Human scleral permeability was decreased by as much as a factor of two for water (P = 0.0004), dexamethasone (P<0.0001), and carboxyfluorescein (P = 0.0064) at elevated intraocular pressures. Rabbit scleral permeability was similarly affected by elevated intraocular pressure for water (P = 0.0039), dexamethasone (P = 0.0001), and carboxyfluorescein (P = 0.0016). CONCLUSIONS: This study shows that simulated intraocular pressure ranging from 15 to 60 mm Hg can decrease scleral permeability to small molecules by one half when compared with the sclera with no pressure applied.

Animals↗
PubMed1997

A long-lasting hypotensive effect of topical diltiazem on the intraocular pressure in conscious rabbits.

The effect of calcium channel blockers on intraocular pressure and aqueous humor dynamics remains still controversial, although preliminary evidence suggests that these drugs may be beneficial in the management of ocular hypertension and low-tension glaucoma. Having previously reported the ocular hypotensive effect of topical nifedipine and verapamil in albino rabbits, the original aim of the present work was to evaluate the effect of topical diltiazem on aqueous humor dynamics in this species. Intraocular pressure was measured with a manual applanation tonometer. The experiments examining the ocular actions of diltiazem were carried out in two stages. In the first one, short term effects of topical diltiazem on intraocular pressure were studied in groups of 13 albino rabbits receiving 8 different doses of the drug in order to obtain a dose-response curve. Tonographies were performed in 13 anaesthetized animals before and 90 min after drug instillation. In a second phase, the persistence of the effect of diltiazem on intraocular pressure was examined in 6 groups of 10 rabbits each receiving three different doses of the drug. Topical diltiazem was found to lower intraocular pressure in a dose-related fashion. The maximum response to diltiazem was greater and the ED50 lower than those previously reported for nifedipine and verapamil. In the tonographic study, diltiazem was shown to reduce the facility of aqueous humor outflow and inflow. Diltiazem exhibited a long lasting effect on intraocular pressure that was again dose-related. Depending on the dose administered, the calculated time necessary for the peak effect to be halved ranged from 0.6 to 7.0 days. Due to the intensity and the persistence of its intraocular pressure-lowering effect, diltiazem shows great potential for the treatment of glaucoma, since a daily or less frequent administration may be enough to control ocular hypertension.

Administration, Topical↗
PubMed1985

Momentary fluctuations of intraocular pressure in normal and glaucomatous eyes.

To examine the range of momentary fluctuations of intraocular pressure caused by vascular pulsations in 42 glaucomatous and 18 normal eyes, we obtained consecutive intraocular pressure measurements at hourly intervals with a noncontact air tonometer. Glaucomatous eyes had a significantly (P less than .001) greater range of intraocular pressure measurements on consecutive readings than normal eyes (4.4 +/- 1.4 mm Hg vs 2.7 +/- 0.7 mm Hg). The frequency of consecutive intraocular pressure readings exceeding a spread of 4 mm Hg was significantly increased in glaucomatous eyes. The range of intraocular pressure measurements was greater even in those glaucomatous eyes with mean intraocular pressures within the normal range. There was a positive correlation between mean intraocular pressure and mean range in glaucomatous eyes, but not in normal eyes. In both glaucomatous and normal eyes, there was no significant correlation between age and mean range.

Adolescent↗
PubMed1987

Management of intraocular pressure during cardiopulmonary bypass.

Intraocular pressure was measured in two groups of patients undergoing cardiopulmonary bypass surgery. A control group received mannitol at the start of bypass in accordance with standard practice; pressure was found to rise by 6.4 mmHg. In a second group of patients mannitol was administered 30 min prior to bypass; pressure elevation of 2.4 mmHg was found. These findings are discussed in relation to other clinical observations during bypass and to ocular morbidity complicating bypass surgery.

Cardiopulmonary Bypass↗
PubMed1986

Retrograde axoplasmic transport in rat optic nerve in vivo. What causes blockage at increased intraocular pressure?

The effect of intraocular pressure (IOP) on retrograde axonal transport of horseradish peroxidase (HRP), from the geniculate body to the retina, was studied in the rat in vivo. In 2-hr experiments (17 eyes at 50 mmHg; 13 eyes at 15 mmHg), the pressures were set just prior to the expected HRP arrival into the eyes. In 4.5-hr experiments (24 eyes at 50 mmHg; 21 eyes at 15 mmHg), the pressures were set 2.5 hr before expected HRP arrival. HRP was measured in the retinas 5 hr after the intrageniculate injection. Transport blockage occurred at an IOP of 50 mmHg in both series of experiments. In an earlier study of axonal transport in vitro, an IOP of 50 mmHg also blocked retrograde HRP transport. In a third series of experiments, 15 eyes were set at an IOP of 180 mmHg for 10 min, 10-20 min before expected arrival of HRP into the eye, while 17 control eyes were set at 15 mmHg. After the 10 min, both groups of eyes were set at 15 mmHg for another 2 hr and the HRP content in the retinas measured, 5 hr after HRP injection. There was no significant difference between these two groups of eyes, suggesting either no rapidly occurring block or a rapid recovery of transport after the high-pressure period. It is proposed that optic nerve fibers are stretched and narrowed near or at their exit, by the high IOP, but recover their shape soon after IOP is normalized.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1976

Measurement of intraocular pressure: a study of its reproducibility.

Intraocular pressure was measured with Goldmann applanation tonometers by two independent examiners in 420 eyes. A difference between measurements of at least 3 mm Hg occurred in 30% of the eyes. Some evidence suggests that the differences between pressure measuremens were caused by actual changes of intraocular pressure rather than by instrument inaccuracy of technician error.

Humans↗
PubMed2000

Effect of calcium channel blockers alone and in combination with antiglaucoma medications on intraocular pressure in the primate eye.

PURPOSE: To determine the effect of representative members from six classes of calcium channel blockers on intraocular pressure in the primate eye. Other antiglaucoma medications were administered with verapamil to determine their combined effect on intraocular pressure. METHODS: Six healthy cynomolgus monkeys were anesthetized, and baseline intraocular pressure was measured. Drug-containing solution (50 microL) was instilled in one eye and intraocular pressure was measured in both eyes 90 minutes later. RESULTS: All classes of calcium channel blockers significantly lowered intraocular pressure in the treated eye. The percent reduction in intraocular pressure compared with the baseline pressure was 10% for verapamil (P < 0.002), 18% for nifedipine (P < 0.001), 15% for diltiazem (P < 0.001), 17% for flunarizine (P < 0.001), 19% for prenylamine (P < 0.001), and 6% for perhexiline (P < 0.01). In the fellow eye, a significant reduction in intraocular pressure was also seen with all calcium channel blockers except perhexiline, which suggested a crossover effect. In contrast, neither vehicle treated nor contralateral eyes showed a lowering of intraocular pressure when tested under the same conditions. In the treated eye, 0.5% timolol (P < 0.01) and 0.05% clonidine (P < 0.02) combined with 0.25% verapamil each appeared to produce an additive effect, with a significantly greater pressure-lowering effect than either agent alone. In addition, 0.005% pilocarpine (P < 0.001) and 0.00125% demecarium (P < 0.01) combined with 0.25% verapamil each appeared to produce a synergistic effect, with a significantly greater reduction in intraocular pressure than both agents combined. CONCLUSIONS: Topical calcium channel blockers and combinations of verapamil with antiglaucoma medications may provide a useful alternative for reducing intraocular pressure in patients with ocular hypertension or primary open-angle glaucoma.

Animals↗
PubMed1976

Effect of the intraocular lens on intraocular pressure.

In the Miami Intraocular Lens Collaborative Study, 17 patients with glaucoma had a Copeland lens implanted at the time of cataract extraction. Seven additional glaucoma patients received a Binkhorst lens. Lens implantation did not adversely affect intraocular pressure or control of glaucoma, except in one patient who developed central retinal artery occlusion with rubeosis 1 1/2 years postoperatively and in one patient who had the lens removed because of iritis with uncontrolled glaucoma. Of 606 eyes that did not have glaucoma before cataract extraction and Copeland lens implant, many had transient postoperative pressure rise. Twenty-six (4.3%) developed prolonged pressure elevation. Nineteen patients were maintained on long-term medical therapy. The other seven were patients with iritis and glaucoma who had the implanted lens removed, including one who later had glaucoma surgery and one whose eye was later enucleated.

Arterial Occlusive Diseases↗
PubMed1979

Comparison of the effects of nine beta-adrenergic blocking agents on intraocular pressure in rabbits.

The intraocular pressure lowering effects of nine beta-adrenergic receptor blocking agents were compared using two different models of experimental ocular hypertension in rabbits. All the nine drugs possess, to different extents, a clear pressure-lowering action after topical administration into the conjunctival sac. For potency and duration of action, the best results were obtained with timolol and sotalol. Pindolol, oxprenolol, practolol, and propranolol are also fairly potent while less impressive effects were produced by atenolol, butidrine, and metoprolol. With the exception of propranolol, all the drugs were well tolerated by the ocular tissues.

Adrenergic beta-Antagonists↗