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Results for “INTRAOCULAR PRESSURE”

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At least 145 records · Page 8Linked to original sources
PubMed1997

Risk factors for elevated intraocular pressure after the use of intraocular gases in vitreoretinal surgery.

BACKGROUND AND OBJECTIVE: The authors studied the contribution of multiple factors, including gas type and concentration, to postoperative intraocular pressure (IOP) elevation following vitreoretinal surgery with intraocular gas. PATIENTS AND METHODS: One hundred seventy-one eyes of 134 patients were retrospectively investigated after vitreoretinal surgery using air, sulfur hexafluoride (SF6) (10%-30%), or perfluoropropane (C3F8) (5%-35%). RESULTS: IOPs greater than 25 mm Hg occurred in 74 of 171 eyes (43%). Elevated IOP was associated with increasing patient age (P < .001), expansile gas concentrations (P < .001), use of C3F8 (P = .01), and circumferential scleral buckles (P = .04). Most IOP elevations (65 eyes, 88%) occurred within 24 hours and responded to aqueous suppression within 24 to 72 hours. CONCLUSIONS: Transient IOP elevation is common following vitreoretinal surgery. Although it is responsive to treatment, it may pose a risk to some eyes. Prophylactic treatment should be considered in high-risk eyes.

Adolescent↗
PubMed2002

Refractory intraocular pressure increase after phakic posterior chamber intraocular lens implantation.

PURPOSE: To describe a complication resulting from the implantation of a posterior chamber intraocular lens in a phakic eye. DESIGN: Interventional case report. METHODS: We examined a 37-year-old woman with severe myopia who had implantation of a phakic posterior chamber intraocular lens. RESULTS: The patient developed pigmentary glaucoma with refractory increase in intraocular pressure, despitemedical therapy and intraocular lens removal. Trabeculectomy was required to reduce the pressure. CONCLUSION: This case demonstrates that pigmentary glaucoma secondary to implantation of a phakic posterior chamber intraocular lens can lead to filtering surgery to decrease intraocular pressure.

Adult↗
PubMed1991

Effects of IAL and Healon on postoperative intraocular pressure after cataract surgery with intraocular lens implantation.

A randomized controlled study was done on 60 patients, divided into three groups, who underwent extracapsular cataract extraction and intraocular lens implantation. The aim of the study was to investigate the effect on postoperative intraocular pressure (IOP) of IAL left in situ compared with IAL or Healon removed after surgery. The IOP was monitored three, six, 12, and 24 hours and seven days after surgery. In general, there was a similar trend in IOP in the three groups with increasing values starting three hours after surgery and normal values reached around 24 hours. No significant statistical difference was found when IAL was removed compared with Healon removed or IAL left in situ compared with Healon removed. No differences were found in the presence of an inflammatory reaction or its severity among the three groups 24 hours after surgery. We believe that IAL can be used in cataract surgery without removing it at the end of the operation, thus simplifying surgical maneuvers and reducing surgical risks.

Adult↗
PubMed1983

Function of retinal nerve fibers depends on perfusion pressure: neurophysiologic investigations during acute intraocular pressure elevation.

Field potentials of the ganglion cell axons were recorded in the cat from the retinal surface during electrical stimulation of the optic tract. Using this technique during intraocular pressure (IOP) elevation, the impulse conduction was investigated independent of the neuronal input to the retinal ganglion cells. By infusing Na-Nitroprusside intravenously, the mean arterial blood pressure (BPm) of the animal was adjusted to levels between 50 and 130 mmHg. Thus, by setting the perfusion pressure (PP) to values between +30 and -20 mmHg, a large range of IOPs was tested. A PP of +20 mmHg or more left the axonal impulse conduction unimpaired, independent of whether the absolute IOP was 40 or 135 mmHg. Interruption of impulse conduction occurred first at a PP of +10 mmHg. At a PP of 0 mmHg or less, the impulse conduction ceased after a constant time interval (80-120 sec, when 20 Hz electrical stimulation was used). Recovery of the field potentials after restoring normal IOP was independent of the preceding IOP or PP. This data demonstrates that in short-term IOP elevation the electrical function of the ganglion cell axon depends on the PP and not on the absolute height of the IOP.

Animals↗
PubMed1994

24-hour (nyctohemeral) and sleep-related variations of intraocular pressure in healthy white individuals.

Intraocular pressure was measured hourly during 24 hours in 12 young (20.6 +/- 0.3 years, mean +/- SEM) and 12 older (59.5 +/- 1.6 years) healthy white adults to determine whether intraocular pressure followed a circadian rhythm and whether its nocturnal variations were related to the stages of sleep in the subjects. An electronic tonometer (Tono-Pen), working on the applanation principle, which was shown to give accurate intraocular pressure measurements in any posture, was used to measure intraocular pressure. Nocturnal polysomnography was measured. Wakefulness, light sleep (stages 1 and 2), slow-wave sleep (stages 3 and 4), and rapid eye movement sleep were scored. Intraocular pressure followed a circadian rhythm with a nocturnal peak value (acrophase). The variations in intraocular pressure were related to the stage of sleep, being lowest during rapid eye movement sleep, and highest during slow-wave sleep.

Adult↗
PubMed1980

Oxygen lowers intraocular pressure.

A significant decrease in intraocular pressure was demonstrated in 14 patients as atmospheric pressure was increased at intervals of 0.5 atmospheric pressure up to 3 atmospheres within a hyperbaric chamber. Nine of these patients had the identical protocol repeated in room air at atmospheric pressure without a significant change in intraocular pressure. Administration of 100% O2 at 15 L/min by partial rebreathing face mask to these patients using the same protocol at atmospheric pressure resulted in a significant decrease in intraocular pressure. The results in the oxygen and hyperbaric groups were not statistically different. While in the hyperbaric chamber, scleral rigidity increased uniformly, outflow facility decreased significantly, and keratometry readings remained unchanged. A significant decrease in intraocular prssure occurred in 20 rabbits that received 100% oxygen by partial rebreathing face mask for 180 minutes. Arterial blood gases were obtained at 0.90, and 180 min in seven rabbits. The pH and pCO2 did not change significantly; however, pO2 was markedly elevated. Increased oxygen concentration was felt to be responsible fot the decrease in intraocular pressure and the changes in other parameters observed in patients and rabbits.

Animals↗
PubMed1978

The vascular basis of the positional influence of the intraocular pressure.

By measuring intraocular pressure in different body positions from 60 degrees semiupright to 30 degrees head down, a nonlinear relationship between IOP increase and body position was confirmed. IOP postural response in individual subjects was roughly correlated to ophthalmic arterial pressure and to the episcleral venous pressure postural response. In one series of subjects, the episcleral venous pressure increments due to posture wa; parallel to the applanation-indentation disparity in the same individual eyes. Differential tonometry with applanation or indentation procedures under blind conditions gave significantly low indentation readings. It is concluded that IOP postural response depends on arterial and venous vascular changes when subjects move from an erect to a horizontal body position. Blood expulsion from the choroid by indentation tonometry might be the reason that this tonometric procedure does not measure IOP changes based on vascular changes.

Adult↗
PubMed1984

Intraocular pressure in diabetic persons.

Intraocular pressure measurements were taken in 2366 diabetic persons and 381 nondiabetic persons who lived in southern Wisconsin. Diabetic persons tended to have higher mean intraocular pressure than the nondiabetic persons. Higher blood pressure, earlier time of day of IOP measurement, absence of cataract and, in some comparisons, female gender, were significantly associated with higher intraocular pressure. In this study rates of a positive history of glaucoma were higher in diabetic persons than in nondiabetic persons and the population participating in the Health Interview Survey. These findings suggest that ophthalmologists must be aware of the increased risk of glaucoma when evaluating diabetic patients.

Adolescent↗
PubMed1984

The relation between visual sensitivity and intraocular pressure in normal eyes.

Intraocular pressure and flicker modulation sensitivity at 25 and 40 Hz were measured in 22 normal observers, with an age range from 20-71 years. Significant correlations up to 0.67 were found between intraocular pressure and flicker sensitivity at several points in the visual field. There was no correlation between flicker sensitivity and age of the observers. Thus intraocular pressure may affect neuronal function in the normal eye.

Adult↗
PubMed1994

The influence of elevated intraocular pressure on vascular pressures in the cat retina.

PURPOSE: Elevated intraocular pressure is known to reduce retinal blood flow, although the effect of intraocular pressure on retinal vascular pressures is unknown. Direct measurements of intravascular pressures were taken in the cat retina at various intraocular pressures. METHODS: Micropipettes of 2- to 3-microns tip diameter were used in conjunction with a servonull pressure-measuring system to determine retinal intravascular pressures in supine anesthetized cats. Pressures in large (80 to 120 microns diameter) vessels near the optic disc were measured over a wide range of intraocular pressures. RESULTS: Measurements show that retinal artery pressure depends on both intraocular pressure and mean systemic blood pressure, and that retinal vein pressure is determined by, but generally is different from, intraocular pressure, with no significant correlation to mean systemic blood pressure. Empirical equations are presented that predict statistically significant retinal artery, vein, and microvascular perfusion pressures. CONCLUSIONS: Intraocular pressure is an important determinant of the microvascular perfusion pressure in the retina of the cat, particularly at low mean systemic blood pressure. It is also apparent that retinal vein pressure is always greater than intraocular pressure, which implies the existence of a high-resistance extraretinal segment of the retinal vein. The results suggest mechanisms for the loss of visual function in glaucoma and other retinal circulatory disorders.

Animals↗
PubMed1993

Intraocular pressure and mechanical ventilation.

Mechanical ventilation increases superior vena cava pressure and should theoretically increase episcleral venous pressure and intraocular pressure (IOP). A Keeler Pulsair Non Contact Tonometer was used to measure the IOP's of six subjects with no history of glaucoma or ocular hypertension. At 30 min of supine mechanical ventilation of tidal volume with low (7 to 15 cm H2O) peak inspiratory pressures, the IOP's were no different than at the end of a 30-min control period of supine spontaneous ventilation. However, using high (60 cm H2O) peak inspiratory pressures for 1 min after tidal volume ventilation, IOP's were 32.7% higher than at the end of the supine spontaneous ventilation control period (p < 0.05). Patients requiring long-term mechanical ventilation at high peak inspiratory pressures may be at increased risk of vision impairment secondary to machine-induced increase of IOP.

Adult↗
PubMed2001

The effect of prone positioning on intraocular pressure in anesthetized patients.

BACKGROUND: Ocular perfusion pressure is commonly defined as mean arterial pressure minus intraocular pressure (IOP). Changes in mean arterial pressure or IOP can affect ocular perfusion pressure. IOP has not been studied in this context in the prone anesthetized patient. METHODS: After institutional human studies committee approval and informed consent, 20 patients (American Society of Anesthesiologists physical status I-III) without eye disease who were scheduled for spine surgery in the prone position were enrolled. IOP was measured with a Tono-pen XL handheld tonometer at five time points: awake supine (baseline), anesthetized (supine 1), anesthetized prone (prone 1), anesthetized prone at conclusion of case (prone 2), and anesthetized supine before wake-up (supine 2). Anesthetic protocol was standardized. The head was positioned with a pinned head-holder. Data were analyzed with repeated-measures analysis of variance and paired t test. RESULTS: Supine 1 IOP (13 +/- 1 mmHg) decreased from baseline (19 +/- 1 mmHg) (P < 0.05). Prone 1 IOP (27 +/- 2 mmHg) increased in comparison with baseline (P < 0.05) and supine 1 (P < 0.05). Prone 2 IOP (40 +/- 2 mmHg) was measured after 320 +/- 107 min in the prone position and was significantly increased in comparison with all previous measurements (P < 0.05). Supine 2 IOP (31 +/- 2 mmHg) decreased in comparison with prone 2 IOP (P < 0.05) but was relatively elevated in comparison with supine 1 and baseline (P < 0.05). Hemodynamic and ventilatory parameters remained unchanged during the prone period. CONCLUSIONS: Prone positioning increases IOP during anesthesia. Ocular perfusion pressure could therefore decrease, despite maintenance of normotension.

Adolescent↗
PubMed1986

The influence of oxybuprocaine (Novesine) on the intraocular pressure.

Patients with raised intraocular pressure often have lower tension during hospital admissions than on out-patient measurement, even though the therapy is the same. A prospective study on 18 volunteers and 10 glaucoma patients was set up to find out whether oxybuprocaine eyedrops or repeated applanation tonometry could have anything to do with this. The tension was measured at least 3 times a day with the non-contact tonometer (NCT). In the case of the volunteers oxybuprocaine was instilled into the eye 3 times a day for one week. In the case of the patients the tension in one eye was measured with the Goldmann tonometer on several days after the application of oxybuprocaine drops. No reduction in intraocular pressure was found during the observation period, nor was there an obvious difference between the test eyes and the control eyes. In hospital, patients had at 11 o'clock in the morning intraocular pressure which was on the average 2.2 +/- 1.5 mmHg lower than that measured at out-patient checks, in spite of receiving the same therapy.

Adult↗
PubMed1990

Effects of halothane on intraocular pressure in anesthetized children.

Intraocular pressure (IOP) measurements in children are usually performed under nitrous oxide and halothane anesthesia. We studied the effects of both time and end-tidal halothane concentration on IOP in 80 children (mean age +/- SD = 4.5 +/- 2.9 yr), to determine the most optimal time to make such measurements in anesthetized children. In 30 children the end-tidal halothane and nitrous oxide concentrations were kept constant while IOP was measured at 1-min intervals after the induction of anesthesia. Intraocular pressure did not change with time. In another 50 children IOP was measured immediately after induction, after 10 min of steady-state end-tidal halothane concentrations of both 0.5% and 1.0% in 66% nitrous oxide, and immediately after tracheal intubation. Intraocular pressure did not differ significantly at either halothane concentration but increased after tracheal intubation. We conclude that in patients anesthetized with halothane and nitrous oxide, IOP after induction remains constant over time and is not affected by end-tidal halothane concentrations up to 1.0% but is affected by tracheal intubation. Thus, the optimal time to measure IOP in children receiving up to 1% halothane in 66% nitrous oxide is during the first 10 min after induction, but before tracheal intubation.

Anesthesia, Inhalation↗
PubMed1987

Prevalence and mechanisms of secondary intraocular pressure elevation in eyes with intraocular tumors.

A survey of 2704 eyes with intraocular tumors in patients who were evaluated on the Oncology Service at Wills Eye Hospital showed that 126 of the tumor-containing eyes (5%) had tumor-induced elevated intraocular pressure (IOP) at the time of diagnosis of the tumor. Of the 2111 eyes with uveal melanomas, secondary IOP elevation was present in 55 (3%). Secondary IOP elevation was present in 7% of eyes with iris melanoma, 17% with ciliary body melanoma, and 2% with choroidal melanoma. The most common mechanism of elevated IOP was tumor invasion of the angle in the case of iris melanomas, pigment dispersion and tumor invasion of the angle in the case of ciliary body melanomas, and iris neovascularization in the case of choroidal melanomas. Of the 256 eyes with uveal metastases, secondary IOP elevation was found in 12 eyes (5%). Secondary IOP elevation was present in 64% of eyes with iris metastases, 67% with ciliary body metastases, and 1% with choroidal metastases. The most common mechanism of elevated IOP was tumor invasion of the angle in the case of iris and ciliary body metastases, and angle closure in the case of choroidal metastases. There were 303 eyes with retinoblastoma, 17% of which had elevated IOP which was secondary to iris neovascularization in 70% of cases and to an angle closure without neovascularization in 27%. Several other intraocular tumors including lymphoma, leukemia, medulloepithelioma, melanocytoma, and adenoma of the iris pigment epithelium were occasionally associated with secondary elevated IOP.

Biomechanical Phenomena↗