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Results for “INTRAOCULAR PRESSURE”

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PubMed1976

The intraocular pressure response of conscious rabbits to clonidine.

A study has been made of the time courses of the pupillary and intraocular pressure responses of conscious rabbits to clonidine administered either topically or intravenously. Topical unilateral application of clonidine caused transient pupil dilatation and a biphasic intraocular pressure response; an initial hypertensive response preceded a hypotensive phase lasting several hours. Pupillary and hypertensive responses were absent in the untreated eye, but there was a rapid decrease of intraocular pressure. Intravenous administration of clonidine caused an immediate and large decrease of intraocular pressure in both eyes. Phenoxybenzamine given intravenously inhibited the pupillary dilatation and the hypertensive responses to clonidine. The role of efferent adrenergic neuronal activity in mediating the local biphasic pressure response was studied in rabbits with unilateral precervical and postcervical sympathotomy. The results showed the hypotensive response to be dependent on an intact adrenergic innervation of the ocular tissues.

Administration, Topical↗

PubMed1987

Long-term follow-up of pseudoexfoliation and the development of elevated intraocular pressure.

A retrospective study was performed to determine the long-term course of pseudoexfoliation (PEX) as it relates to both the development of elevated intraocular pressure and to the initial appearance of exfoliation material in normal fellow eyes of patients with PEX. Six hundred eighty patients seen from 1940 through 1980 were diagnosed as having PEX. Patients were excluded from long-term study if there was a diagnosis of glaucoma prior to examination at our institution (199 patients), if glaucoma was present at the time of diagnosis of PEX (40 patients), if there was a history of prior intraocular surgery or disease (19 patients), or if there was only one ocular examination performed (75 patients). The remaining 347 patients with initially normal intraocular pressures were followed over time and consisted of 225 patients with unilateral PEX and 122 patients with bilateral PEX (a total of 469 PEX eyes). Life table (actuarial) analysis was used for data evaluation. During the course of the study, 32 (14%) of the unilateral cases of PEX became bilateral. The cumulative probability of a normal fellow eye developing PEX increased over time, with a 6.8% cumulative probability in 5 years and a 16.8% cumulative probability in 10 years. Elevated intraocular pressure developed in 35 patients (44 eyes) during the study. The cumulative probability for eyes with PEX to develop elevated intraocular pressure was 5.3% in 5 years and increased to 15.4% in 10 years. These probabilities predict that patients with PEX have a higher incidence of developing elevated intraocular pressure than would be expected in patients without PEX of similar age.

Actuarial Analysis↗

PubMed1996

The effect of chronically elevated intraocular pressure on the rat optic nerve head extracellular matrix.

The extracellular matrix of the optic nerve head is altered in both human glaucoma and in experimental primate models of this disease. However, the relationship of this change to glaucomatous optic nerve degeneration is unknown. This report describes similar matrix alterations in rats with unilateral elevated intraocular pressure. Brown Norway rats received episcleral vein injections of hypertonic saline to produce prolonged elevations of intraocular pressure. After up to 6 months of pressure elevation, optic nerve head sections from the rats were evaluated by light microscopic immunohistochemistry using antibodies to collagens I, III, IV and VI, laminin, elastin and chondroitin and dermatan sulfate proteoglycans. In experimental eyes with 11 days or more of pressure elevation, depositions of collagen IV, collagen VI and laminin were found within regions of the optic nerve head that, in normal eyes, are occupied solely by nerve bundles. Collagen I and III deposition appeared to be more dependent on the level and duration of the pressure rise. Eyes with lower mean intraocular pressures showed deposits of interstitial collagens primarily at the level of the sclera, while eyes with higher mean pressure elevations had depositions in the neck regions as well. Chondroitin and dermatan sulfate proteoglycans were deposited in a pattern similar to that of collagen I. No extracellular matrix deposition was seen in the orbital optic nerve in any experimental eye. These extracellular matrix changes in rats replicate previous findings in human glaucomatous eyes and monkey eyes with experimentally elevated pressures. They also suggest a sequence of extracellular matrix protein deposition in response to pressure elevation. The optic nerve head deposition of matrix materials in response to elevated intraocular pressures may affect the susceptibility of remaining axons to pressure by changing the physical properties of their support tissues, by affecting the support functions of astrocytes and by changing the microenvironment of injured axons. This model may be useful for studying these and other aspects of the process of axonal injury resulting from elevated intraocular pressure.

Animals↗

PubMed2006

Fluctuation of intraocular pressure and glaucoma progression in the early manifest glaucoma trial.

PURPOSE: To investigate whether increased fluctuation of intraocular pressure (IOP) is an independent factor for glaucoma progression. DESIGN: A cohort of patients was followed up in a randomized clinical trial. PARTICIPANTS: Two hundred fifty-five glaucoma patients from the Early Manifest Glaucoma Trial (EMGT; 129 treated and 126 control patients). METHODS: Study visits, conducted every 3 months, included ophthalmologic examinations, IOP measurements, and standard automated perimetry, with fundus photography every 6 months. Intraocular pressure values were included only until the time of progression in those eyes that showed such progression. Individual mean follow-up IOP and IOP fluctuation, calculated as the standard deviation of IOP at applicable visits, were the variables of main interest. Cox regression with time-dependent variables was used to evaluate the association between IOP fluctuation and time to progression, both with and without IOP mean in the models. These analyses also controlled for other significant variables. MAIN OUTCOME MEASURES: Glaucoma progression, as defined by a predetermined visual field criterion, worsening of the disk, assessed by an independent disc reading center, or both. RESULTS: Median follow-up time was 8 years (range, 0.1-11.1 years). Sixty-eight percent of the patients progressed. When considering mean follow-up IOP and IOP fluctuation in the same time-dependent model, mean IOP was a significant risk factor for progression. The hazard ratio (HR) was 1.11 (95% confidence interval [CI], 1.06-1.17; P<0.0001). Intraocular pressure fluctuation was not related to progression, with an HR of 1.00 (95% CI, 0.81-1.24; P = 0.999). CONCLUSIONS: These results confirm our earlier finding that elevated IOP is a strong factor for glaucoma progression, with the HR increasing by 11% for every 1 mmHg of higher IOP. Intraocular pressure fluctuation was not an independent factor in our analyses, a finding that conflicts with some earlier reports. One explanation for the discrepancy is that our analyses did not include postprogression IOP values, which would be biased toward larger fluctuations because of more intensive treatment. In contrast, in this EMGT report, no changes in patient management occurred during the period analyzed.

Aged↗

PubMed1995

The effects of mild, moderate, and severe exercise on intraocular pressure in glaucoma patients.

BACKGROUND: Previous studies have shown a reduction in intraocular pressure (IOP) from many means of exertion, ranging from walking to exhausting exercise in both normal and glaucoma subjects. The variability in their results may be due to several variables that can affect IOP significantly. PURPOSE: To investigate the effects of common means of exertion on IOP in normal and glaucoma subjects, after elimination of factors that can affect IOP. SUBJECTS AND METHODS: The effects of walking, jogging, and running fast until exhaustion on IOP were noted in seven normal and seven open-angle glaucoma subjects. Intraocular pressures were measured with the Goldmann applanation tonometer during and after exercise. RESULTS: The mean differences between before and after walking, jogging, and running exercises were -2.43 +/- 0.30, -3.85 +/- 0.55, and -4.0 +/- 0.37 mmHg in normal subjects. In glaucoma patients these differences were -7.72 +/- 1.25, -10.86 +/- 2.12, and -12.86 +/- 2.05 mmHg, respectively. After 5 min of walking and jogging, in all subjects, IOP decreased significantly (by 56 to 61% of total decreases). CONCLUSION: Regardless of the means of exertion, in every subject tested there was a drop in intraocular pressure. Glaucoma patients had a greater drop and longer duration of post-exercise recovery as compared to normal subjects. It would seem reasonable, at present, not to discourage patients who have glaucoma from light exercises such as walking; perhaps, on the contrary, it should be encouraged.

Adult↗

PubMed1992

Corneal diameter, axial length, and intraocular pressure in premature infants.

PURPOSE: Seventy premature infants 25 to 37 weeks' postconceptional age were examined during their first week of life to determine the correlation of corneal diameter, axial length, and intraocular pressure with gestational age and birth weight. METHODS: Corneal diameter measurement was determined with corneal templates, total axial length with standardized A-scan ultrasound, and intraocular pressure with a Tonopen II tonometer. RESULTS: Corneal diameter and total axial length showed parallel linear increases from 6.2 mm to 9.0 mm and 12.6 mm to 16.2 mm, respectively; however, no significant correlation was found between intraocular pressure and gestational age or birth weight. The mean intraocular pressure was 10.3 mmHg (standard deviation, 3.5). CONCLUSION: Normative values are established for corneal diameter and total axial length as they relate to birth weight and gestational age, and a mean and standard deviation for intraocular pressure in the premature newborn. These values will aid the ophthalmologist in assessing ocular dimensions in premature infants.

Birth Weight↗

PubMed2001

Clinical comparison of two intraocular pressure measurement methods: SmartLens dynamic observing tonography versus Goldmann.

PURPOSE: To compare intraocular pressure measurements obtained with SmartLens, a gonioscopic contact lens, to those from Goldmann applanation tonometry. METHODS: Eighty volunteers (20 healthy individuals and 60 glaucoma patients from the university eye hospital's outpatient department) were examined using conventional Goldmann tonometry and the new SmartLens tool. For each device three replicate measurements were performed. A paired t-test and the corresponding mean difference confidence interval approach were used to assess deviations in location of the two tonometric methods; the test procedure of Maloney and Rastogi was used for comparison of precision in paired data. Intraindividual differences were evaluated according to the approach of Altman and Bland. RESULTS: There was a mean difference of 5.6 mmHg (95% CI: 4.3 mmHg; 6.8 mmHg; P<0.01) in intraocular pressure between the two methods with a significant overestimation by SmartLens tonometry compared to Goldmann tonometry (P<0.01). The 95%-limits of agreement ranged from -5.4 mmHg to +16.6 mmHg for individual patients. The measurement method variance of SmartLens was higher (Maloney-Rastogi test; P <0.01). The mean coefficients of variation for intraindividual replicates were 10.1% (SmartLens) and 3.8% (Goldmann; P <0.01). CONCLUSIONS: Accepting Goldmann tonometry as gold standard for intraocular pressure measurement, the SmartLens method shows considerable variation and therefore is not proven to be an adequate substitute for Goldmann tonometry.

Adult↗

PubMed1982

Neural control of intraocular pressure.

Efferent and afferent pathways by which the central nervous system (CNS) may control intraocular pressure (IOP) are considered. As experience with pharmaceutical agents has suggested, the targets for autonomic influence on ocular tension are both aqueous formation and resistance to outflow. The afferent input to the brain must be served by sensory fibers which are sensitive to intraocular pressure levels or which respond to changes in intraocular pressure. The location and physiology of such receptors is discussed.

Afferent Pathways↗

PubMed1992

Intraocular pressure decrease in household contacts of patients with Hansen's disease and endemic control subjects.

We compared the intraocular pressure in 150 urban household contacts of patients with Hansen's disease and 132 endemic control subjects from an urban population in Karachi, Pakistan, who were matched in regard to race, age, gender, and socioeconomic status. The mean intraocular pressure in the upright position was 12.6 mm Hg in the right eye and 12.9 mm Hg in the left eye in household contacts of patients with Hansen's disease and 15.3 mm Hg in the right eye and 15.4 mm Hg in the left eye in the endemic control population (P < .0005). The postural change in intraocular pressure from the upright to supine position was 1.7 mm Hg in the right eye and 2.1 mm Hg in the left eye in the household contacts group and 1.3 mm Hg in the right eye and 1.5 mm Hg in the left eye in the endemic control group (P < .0006). Our findings, especially in view of past observations in intraocular pressure changes in patients with Hansen's disease, raise serious questions about possible early ocular susceptibility to Mycobacterium leprae infection and about public health issues, including possible early indication of disease.

Adolescent↗

PubMed2001

Late normalization of melanocytomalytic intraocular pressure elevation following excision of iris melanocytoma.

BACKGROUND: Melanocytoma of the iris is a rare tumor which may sometimes undergo necrosis that could result in elevated intraocular pressure through pigment dispersion. Only nine similar patients have been previously reported. METHODS: A 27-year-old woman presented with a dark brown iris stromal mass located between the 4 and 8 o'clock positions in the inferior quadrant. Her left visual acuity was 20/60. The tumor encroached on the lens and caused focal cataract. There was massive pigmented debris over the iridocorneal angle and the intraocular pressure was 42 mmHg. RESULTS: Fine needle aspiration biopsy did not suggest malignancy. A wide sector iridectomy was performed and histopathological examination of the lesion revealed melanocytoma of the iris. There was no ciliary body involvement. In the postoperative period, intraocular pressure, which persisted in the mid-twenties, was successfully lowered with topical dorzolamide and betaxolol drops. These drugs were continued for 2 years while the angle pigmentation gradually disappeared. There has been no documented glaucomatous damage to the optic nerve and visual fields. A year after the cessation of the drops, the left intraocular pressure stabilized and did not rise above 15 mmHg. Her left visual acuity remained 20/25. CONCLUSION: In contrast to previously reported cases, the normalization of intraocular pressure in this patient took 26 months, a period that could be associated with the self-clearing process of pigment from the iridocorneal angle. Close follow-up with medical treatment averted a pressure lowering surgical procedure in this case.

Adult↗

PubMed2002

The effect of topical natural ergot alkaloids on the intraocular pressure and aqueous humor dynamics in rabbits with alpha-chymotrypsin-induced ocular hypertension.

BACKGROUND: We previously reported that topical natural ergot alkaloids ergocristine, alpha-ergocryptine and ergocornine dose-dependently reduce intraocular pressure in ocular normotensive rabbits, most likely by decreasing aqueous humor inflow. In the present study, the effects of these compounds on intraocular pressure and aqueous humor dynamics in a rabbit model for ocular hypertension were assessed. METHODS: Experiments were conducted in albino rabbits made ocular hypertensive by intracameral injection of alpha-chymotrypsin. Intraocular pressure responses to drug vehicle and seven different doses of topical natural ergot alkaloids were examined in order to obtain dose-response relationships for comparing the intraocular pressure-lowering effect and potency of these drugs. Tonographies were also performed to ascertain the actions of natural ergot alkaloids on aqueous humor dynamics in alpha-chymotrypsin-induced ocular hypertensive rabbits. RESULTS: Topical application of the natural ergot alkaloids ergocristine, alpha-ergocryptine and ergocornine lowered intraocular pressure in alpha-chymotrypsin-induced ocular hypertensive rabbits in a dose-related fashion, with ergocristine displaying the greatest intraocular pressure-lowering effect. Tonographic studies revealed a decrease in the tonographic outflow facility following topical application of natural ergot alkaloids, although only the effects of both ergocristine and alpha-ergocryptine reached statistical significance. All natural ergot alkaloids tested significantly reduced the calculated aqueous humor inflow. CONCLUSION: This study suggests that the natural ergot alkaloids ergocristine, alpha-ergocryptine and ergocornine effectively decrease intraocular pressure in the alpha-chymotrypsin-induced model of ocular hypertension. Since these compounds reduce the tonographic aqueous humor outflow facility, their final ocular antihypertensive effect appears to result from a remarkable reduction of the aqueous humor inflow.

Administration, Topical↗

PubMed1980

[Changes in intraocular pressure in anesthesia induced with althesin and maintained with methoxyflurane].

Intraocular pressure and arterial blood pressure were studied in 27 patients undergoing anaesthesia induced by 0,6-1 mg/kg of Althesin iv and maintained by methoxyflurane-N2O-O2 on spontaneous ventilation. All patients were scheduled to undergo various types of eye surgery, including open-eye surgery. Patients with glaucoma and cataract were administered 20% mannitol two hours prior to surgery. In all cases premedication was based on meperidine, promethazine and atropine sulphate im. During the entire period of anaesthesia the intraocular pressure and, generally, arterial blood pressure appeared to be lowered.

Adolescent↗

PubMed2005

Accuracy of intraocular pressure measurements in new zealand white rabbits.

PURPOSE: Rabbits are commonly used for the evaluation of drugs and surgery to lower intraocular pressure (IOP). The accuracy of intraocular pressure measurement is therefore critical in the analysis of data and subsequent extrapolation to humans. The purpose of this study was to establish the most reliable technique, from several currently available methods, of measuring IOP in New Zealand White rabbits. METHODS: The IOPs of 11 healthy New Zealand White rabbits were measured with a fluid-filled pressure transducer system that was connected to the anterior chamber of each animal so that the IOP could be varied by altering the height of a bottle of balanced salt solution. Intraocular pressures were recorded over a range of 50 to 0 mm Hg by the transducer system, and comparative measurements at the same pressures were performed with the Tonopen XL (Mentor, Norwell, MA), the Perkins handheld applanation tonometer (Clement Clarke, Harlow, UK), and the Ocular Blood Flow (OBF) pneumatonometer (OBF Laboratories, Wiltshire, UK). RESULTS: All three tonometers underestimated the true IOP, especially at higher pressures. Although the mean difference in actual and tonometric IOP was least in the Tonopen XL, there was a high degree of variability through the entire range of IOPs measured. The Perkins tonometer, although slightly less accurate than the Tonopen XL, was more consistent in measurement. The OBF pneumatonometer was the least-reliable estimate of IOP. CONCLUSIONS: All tonometers underestimate IOP, with increasing inaccuracy at higher pressures. The Perkins applanation tonometer was the most reliable for measuring IOP in the range of 0 to 50 mm Hg in New Zealand White rabbits.

Animals↗

PubMed2001

[Reproducibility of measurement of ocular pulse amplitude and intraocular pressure using Smartlens].

BACKGROUND: SmartLens (ODC Ophthalmic Development Company AG, Zürich) is a contact lens tonometer, which allows continuous registration of intraocular pressure (IOP) and ocular pulse amplitude (OPA) and simultaneous ophthalmoscopy. The purpose of this study was to evaluate the intra- and interobserver variability and reliability of intraocular pressure and ocular pulse amplitude measurements using SmartLens. METHODS: To evaluate the intraobserver variability, intraocular pressure (IOP) and ocular pulse amplitude (OPA) were both measured 5 times in 10 healthy eyes by one observer. To evaluate the interobserver variability, intraocular pressure and ocular pulse amplitude were measured by 3 different observers in 10 healthy eyes. Data description is based on coefficients of variation (SD/mean in %), statistical inference on ANOVA-based reliability estimation. RESULTS: The coefficient of the intraobserver variation was 9.57% for the IOP and 14.5% for the OPA (SD IOP: +/- 1.64 mmHg, SD OPA: +/- 0.39 mmHg). The coefficient of the interobserver variation with 5 replicate measurements was 10.16% for the IOP and 14% for the OPA (SD IOP: +/- 1.83 mmHg, SD OPA: +/- 0.4 mmHg). The interobserver reliability was 87% for the IOP and 86% for the OPA. One of the three observers obtained significantly higher IOP and OPA values. CONCLUSIONS: SmartLens is a reasonably precise and reliable device for IOP as well as OPA measurements but the results were not found to be observer independent.

Analysis of Variance↗

PubMed1999

Effect of topical atropine on intraocular pressure and pupil diameter in the normal horse eye.

The objective was to determine whether topically administered 1% atropine would alter intraocular pressure. The animals studied were four healthy adult horses. Intraocular pressure and pupil diameter were measured prior to and during a 2-day period of treatment with 1% atropine sulfate. No significant changes in intraocular pressure occurred as a result of the treatment with atropine. Pupil diameter increased significantly after atropine was applied. Available information on the outflow of aqueous humor from the horse eye suggests that atropine might reduce intraocular pressure in the horse by increasing uveoscleral outflow. This could prove beneficial in the treatment of equine glaucoma. We could not confirm a significant pressure-lowering effect of atropine. It is possible, however, that a longer treatment period may be required or that atropine may have a more profound effect on glaucomatous globes.

Journal Article↗

PubMedDate not supplied

Viscoelastic substance in the anterior chamber elevates intraocular pressure.

An 85-year-old man underwent an extracapsular cataract extraction OD with posterior chamber intraocular lens implantation. Sodium hyaluronate (0.3 mL) was used during the procedure, and approximately 1.0 mL of the solution, including the sodium hyaluronate, was aspirated before wound closure. The next day, the intraocular pressure OD was elevated to 60 mmHg, and it remained high despite medication. Three days later, the intraocular pressure was still high, a paracentesis was done, and viscous solution was obtained. After the paracentesis, the intraocular pressure OD normalized.

Aged↗

PubMed1997

A comparison of intraocular pressure measurements with the XPERT noncontact tonometer and Goldmann applanation tonometry.

PURPOSE: The purpose of this study was to compare intraocular pressure measurements obtained with XPERT, an upgraded model of the noncontact tonometer, with those from Goldmann applanation tonometry. METHODS: An average of three intraocular pressure measurements, generated by the XPERT, was compared with a single reading from a Goldmann applanation tonometer in 421 eyes of 220 patients. RESULTS: The standard deviation of the matched-pair differences (Sdiff) for the entire population was 2.3 mm Hg, whereas in a subset of 95 eyes with intraocular pressures of > or = 20 mm Hg by Goldmann applanation tonometry, the Sdiff was 3.3 mm Hg. CONCLUSIONS: The XPERT was found to provide reliable intraocular pressure measurements, especially within the normal range.

Adult↗

PubMed1977

Increased intraocular pressure following topical azide or nitroprusside.

In rabbits the topical administration of sodium azide (NaNs) or sodium nitroprusside (SNP) increased intraocular pressure in a dose-response manner. These agents, which activate guanylate cyclase, elevated cyclic GMP in the aqueous humor. Systemic blood pressure and pulse were not altered. Tonographic outflow facility was unchanged, suggesting an increase in aqueous humor flow as the mechanism for the elevation of intraocular pressure. Posterior chamber aqueous humor ascorbate concentration was decreased in the eye receiving the NaN3 or SNP. Systemic pretreatment with phenoxybenzamine, an alpha-adrenergic blocking agent, prevented the elevation of intraocular pressure observed following NaN3 and SNP. Pretreatment with systemic indomethacin, propranolol, or acetazolamide or the topical application of atropine or epinephrine failed to alter the elevation of intraocular pressure by either NaN3 or SNP.

Administration, Topical↗