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PubMed2005

[Corneal pachymetry and intraocular pressure].

Just recently studies on glaucoma have emphasised the significance of intraocular pressure in the diagnosis of glaucoma and the importance of intraocular pressure reduction in the management of glaucoma. Central corneal thickness appears to play an important role in the exact measurement of intraocular pressure and in the diagnostic assessment of glaucoma. Numerous studies have verified that corneal thickness shows systematic differences in different forms of glaucoma. Since deviations of corneal thickness from normal can possibly result in an artificial change of Goldmann applanation values, it would be a most important source of error in the diagnosis of glaucoma to ignore central corneal thickness. Corrections of intraocular pressure measured with applanation tonometry can be achieved in various ways but there is considerable divergence in the results. The absence of a generally accepted algorithm for the correction of intraocular pressure measured with applanation tonometry should not prevent us from a wide application of pachymetry, since it delivers valuable additional information on the individual risk of glaucoma.

Cornea↗
PubMed2005

Incidence and management of elevated intraocular pressure after silicone oil injection.

PURPOSE: To determine the incidence and clinical features of chronic elevated intraocular pressure after pars plana vitrectomy and silicone oil injection for complicated retinal detachments, and to evaluate the clinical management of eyes with secondary glaucoma. METHODS: This was an observational consecutive case series of 450 eyes in 447 patients who were treated with pars plana vitrectomy and silicone oil injection. Patients who developed secondary glaucoma were treated medically with antiglaucoma medications and surgically with glaucoma drainage implants placed in an inferior quadrant. Main outcome measures were intraocular pressure, number of glaucoma medications, surgical success, and complications. RESULTS: Fifty-one of 450 eyes (11%) developed elevated intraocular pressure after pars plana vitrectomy and silicone oil injection whereas 399 eyes (89%) did not have a rise in intraocular pressure. Of the 51 eyes that developed elevated intraocular pressure, 40 (78%) were treated only with glaucoma medicines. Medical therapy reduced the intraocular pressure from a mean +/- SD of 26 +/- 13.4 mm Hg before treatment to 18 +/- 9.1 mm Hg after medical treatment (P = 0.002). The 11 of 51 eyes (22%) with elevated intraocular pressure that failed medical therapy were treated surgically with Ahmed Glaucoma Valve implantation within 12 months of silicone oil injection. In the surgical group, intraocular pressure was reduced from a mean +/- SD of 44 +/- 11.8 mm Hg before surgery to 14 +/- 4.2 mm Hg at the most recent follow-up after surgery (P < 0.001). The number of antiglaucoma medications was reduced from 3.5 +/- 0.7 before surgery to 1.2 +/- 0.5 at the most recent follow-up after surgery (P < 0.001). CONCLUSION: Chronic intraocular pressure elevation occurs in a minority (11%) of patients who are treated with silicone oil. Most of these eyes are effectively treated with antiglaucoma medications. Eyes that do not respond to medical therapy may be effectively managed with glaucoma drainage implant placement in an inferior quadrant.

Adolescent↗
PubMed1980

The mechanism of optic nerve damage in experimental acute intraocular pressure elevation.

We produced intraocular pressure (IOP) elevations in 32 primate eyes and studied retinal ganglion cell rapid axonal transport with autoradiography and electron microscopy. Animals breathing room air at sea level pressure were compared to animals breathing 100% oxygen at 3 atm pressure in a hyperbaric chamber. Despite major increases in arterial oxygen levels in the hyperbarically oxygenated animals, both groups had axonal transport blockade at the optic nerve head. Anoxia appears not to be the most important cause of acute axonal damage induced by elevated IOP. The pattern of axonal abnormality within individual fiber bundles at the optic nerve head provides support for mechanical compression as a more likely alternative cause for induced neural damage.

Animals↗
PubMed2000

Prevention of intraocular pressure elevations during hemodialysis.

Intraocular pressure (IOP) may rise during hemodialysis sessions in predisposed patients because of a rapid drop in osmolality at the blood compartment. A patient with diabetes had painful ocular episodes during hemodialysis that were associated with an IOP increase. We modified the dialysis parameters to prevent a rapid decrease in osmolality by creating conductivity and ultrafiltration profiles and adding a colloid solution at the beginning of the procedure. After instituting these changes, the patient became asymptomatic and did not have variations in IOP during the dialysis sessions.

Diabetes Mellitus, Type 1↗
PubMedDate not supplied

Intraocular pressure measurement in patients with instrastromal corneal ring segments.

PURPOSE: To study the measurement of intraocular pressure after implantation of Intacs (ICRS) intrastromal corneal ring segment, a device that is positioned circumferentially in the peripheral corneal stroma to correct myopia. The device changes the corneal curvature by shortening arc length. Since the ring segments are made of polymethylmethacrylate, this may cause localized changes in corneal elasticity so intraocular pressure measurement may be affected. METHODS: We measured the intraocular pressure of 12 eyes in which the ICRS had been in place longer than 6 months. We used Goldmann applanation and Tono-Pen tonometers over the central corneal and the paracentral corneal areas. We also measured the intraocular pressure with the Tono-Pen applanated directly over the intrastromal corneal ring segments. RESULTS: The resulting intraocular pressure measurements were similar for the Tono-Pen tonometer readings over the central cornea, paracentral cornea, and the Goldmann applanation tonometer readings over the central cornea (P < .01). Our measurements using the Goldmann applanation tonometer on the paracentral corneal area showed artificially elevated intraocular pressure in the 40 to 60 mmHg range. We were not able to obtain consistent results when we measured the intraocular pressure using the Tono-Pen on the corneal area directly overlying the intrastromal corneal ring segment implants. CONCLUSION: Consistent intraocular pressure measurements on eyes with the ICRS can be obtained with the Goldmann applanation tonometer over the central corneal area or with the Tono-Pen tonometer over the central or paracentral corneal areas.

Corneal Stroma↗
PubMed2006

Choroidal innervation and optic neuropathy in macacque monkeys with laser- or anterior chamber perfusion-induced short-term elevation of intraocular pressure.

Long-term intraocular pressure (IOP) elevation leads to a significant reduction of the intrinsic choroidal innervation and axon loss in the optic nerve. In this study we investigated early changes in these tissues in order to clarify the putative sequence of events between choroidal ganglion cell loss and optic nerve axon loss in 19 monkeys with experimentally induced glaucoma. After 1 month of increased IOP, severe optic neuropathy but no reduction of choroidal ganglion cells (CGC) was detectable. Beginning at 2 months after treatment signs of degeneration in CGC morphology were observed. Laser treatment of the trabecular meshwork without IOP elevation caused no changes in choroidal innervation. Our results show that there is no apparent association between reduction of CGC and optic neuropathy in the early stages of IOP elevation.

Animals↗
PubMed1988

Altering body position affects intraocular pressure and visual function.

Intraocular pressure (IOP) can be altered by changing body position. This report describes two experiments evaluating variations in IOP, as well as neural functioning of the retina and visual cortex (as measured by pattern-reversal electroretinogram and visual evoked potential), associated with whole-body, head-down tilt. The subjects, ten per experiment, were visually normal with IOP less than 19. In the first experiment, IOP elevations were induced by varying the angle of tilt in discrete steps between +90 degrees (upright) and -90 degrees (inverted). In each position IOP was measured and significant elevations (up to 3x baseline) were noted. These elevations were maintained for 1 min during which simultaneous retinal and cortical biopotentials were measured. In the second experiment, 6 degrees head-down tilt was maintained for 2 hr during which time the IOP and both biopotentials were measured repeatedly. Our findings confirm the effect of body position of IOP, while also revealing that head-down tilt produces significant reductions in neurophysiological function at both the retinal and cortical levels. The neural effect is maximized when 6 degrees head-down tilt is maintained for 20 min.

Adult↗
PubMed1990

Early intraocular pressure rise after trabeculectomy.

Intraocular pressure (IOP) was measured 4 to 6 hours after surgery and on the first postoperative day in 35 eyes of 35 consecutive patients undergoing initial trabeculectomy. In 27 eyes, the anterior chamber was re-formed at the completion of surgery with balanced salt solution, and in eight eyes it was reformed with hyaluronate sodium. A total of six eyes (17%) had an IOP of 40 mm Hg or greater 4 to 6 hours after surgery. Patients who received hyaluronate to maintain the depth of the anterior chamber had a significantly greater chance of experiencing a marked postoperative IOP rise, both at 4 to 6 hours (P = .005) and on the first postoperative day (P = .0038). There was no correlation between the postoperative IOP rise and the patient's age, sex, glaucoma diagnosis, preoperative IOP, use of 5-fluorouracil, or the number of sutures used to close the scleral flap. Hyaluronate may contribute to an early increase in IOP that could result in further visual field loss in eyes with severe glaucomatous damage. We recommend early monitoring of IOP after trabeculectomy and avoiding the routine use of hyaluronate.

Acetates↗
PubMedDate not supplied

The effect of betamethasone on intraocular pressure in nephrotic children.

Intraocular pressure (IOP) was measured by Goldmann's or Schiotz's method in 46 nephrotic children, who were treated with betamethasone, and in 40 age-matched normal controls at the Taipei Municipal Chung-Hsin Hospital, from July 1, 1987 to June 30, 1990. We found the difference in mean IOP between patients treated at the end of a full-dose course of betamethasone and normal controls or patients before treatment, was statistically significant. This difference was also found between the measurement of IOP at the end of a full-dose course of betamethasone, and after stopping betamethasone therapy two to four weeks later. Although six of all patients had high IOP and suffered from headache or ocular pain, clinically, at the end of full-dose betamethasone therapy, the symptoms disappeared quickly after tapering or stopping of the drug. Therefore, we believe it is very safe to treat the nephrotic syndrome with betamethasone. On the other hand, these observations indicate that corticosteroid is a causative factor in increasing IOP. Susceptibility to full-dose betamethasone is firmly recognized, and patients need to be monitored on an individual basis. Nephrotic syndrome is a chronic disease which often requires long-term corticosteroid treatment. Children with the syndrome are at risk of developing steroid-induced increasing IOP. Careful ophthalmological examination of nephrotic children, as well as other pediatric patients who received corticosteroid therapy, is highly recommended.

Adolescent↗
PubMed1994

Effect of resisting tonometry on intraocular pressure.

BACKGROUND: Children and patients with developmental delay frequently resist the procedure of tonometry. Intraocular pressure (IOP) readings, if obtained under stressful circumstances, may have questionable reliability because IOP is influenced by numerous factors characteristic of the uncooperative patient. These factors include possible increases in arterial blood pressure, intraocular vascular engorgement, and pressure on the globe. A study of the effect upon IOP of these factors occurring simultaneously has not been reported previously. METHODS: We measured IOP using the Tono-Pen on 40 cooperative adults under normal conditions and again under conditions simulating the resistant patient. RESULTS: Paired t-test revealed a statistically significant difference between IOP readings under the two conditions (p < 0.001), with IOP under "resistant" conditions showing more variability and averaging 6mmHg higher than under normal conditions. CONCLUSIONS: We conclude that IOP readings in resistant patients should be viewed with caution. The possibility of obtaining false high readings in these patients could lead to unnecessary glaucoma evaluations if based only on elevated IOP readings.

Adult↗
PubMed1997

Comparison of intraocular pressure between normotensive and preeclamptic women in the peripartum period.

OBJECTIVE: Our purpose was to determine whether intraocular pressure differs between preeclamptic and normotensive women in the peripartum period. STUDY DESIGN: Eighteen preeclamptic (defined as blood pressure > 140/90 mm Hg and > or = 1+ proteinuria) and 18 normotensive women were studied. Intraocular pressure was determined with a handheld tonometer. Each intraocular pressure determination was obtained by repeatedly touching the cornea until signal averaging produced a single measurement with a variance < 5%. Right and left intraocular pressure, heart rate, and blood pressure were obtained intrapartum and 24 hours post partum with the patient in the seated, supine, and left lateral positions. Data are reported as mean +/- SD or median (range) as appropriate. Significance was set at p < 0.05. RESULTS: No differences existed in race, age, weight, gravidity, parity, cervical dilatation, and heart rate between the preeclamptic and normotensive groups. Gestational age was lower (39 [34 to 42] vs 41 [34 to 42] weeks, p = 0.003), and intrapartum mean arterial pressure (100.2 +/- 9.8 vs 81.0 +/- 8.3 mm Hg, p < 0.001) and degree of proteinuria (3 [1 to 4] vs 0, p < 0.001) were higher in the preeclamptic group. There was no effect of position or delivery on intraocular pressure in either group. Intraocular pressure was higher in the preeclamptic group in the intrapartum (18.8 +/- 3.0 vs 15.3 +/- 2.7 mm Hg, p < 0.001) and postpartum periods (20.2 +/- 4.5 vs 15.7 +/- 3.6 mm Hg, p = 0.002). CONCLUSION: Compared with normotensive women, preeclamptic women have increased intraocular pressure in the peripartum period.

Adult↗
PubMed1985

Diurnal intraocular pressure. Correlation to automated perimetry.

Patients referred to a centralized glaucoma laboratory obtained intraocular pressure measurements every two hours from 5:00 am to 3:00 pm. Analysis revealed 400 eyes with visual field defects and 400 eyes without visual field defects as determined by Octopus perimetry of the central 20 degrees. The diurnal variation in intraocular pressure was 6.2 mmHg +/- 3.6 for those with visual field defects and 5.5 mmHg +/- 2.7 for those without visual field defects. There was no statistical significance in the mean diurnal variation between the two groups (P = 0.91). The highest intraocular pressure tended to occur at either 5:00 am to 7:00 am or 11:00 am to 1:00 pm in both groups. The lowest intraocular pressure tended to occur between 7:00 am to 9:00 am or 1:00 pm to 3:00 pm in both groups. No significant differences were noted in the distribution between the two groups with regard to the time of the highest or lowest intraocular pressure. In the group with visual field defects, 30% had an intraocular pressure of less than 23 mmHg and 23% had an intraocular pressure of greater than or equal to 23 mmHg at all five time periods.

Circadian Rhythm↗
PubMed1988

Increased intraocular pressure in the immediate postoperative period after extracapsular cataract extraction.

We evaluated the immediate intraocular pressure increase after extracapsular cataract surgery in 58 eyes. Two to three hours postoperatively, 34 eyes (59%) developed an intraocular pressure greater than or equal to 25 mm Hg. We found an intraocular pressure of at least 40 mm Hg in seven eyes. Mean intraocular pressure two to three hours postoperatively was 8.9 +/- 9.8 mm Hg greater than the preoperative intraocular pressure. The use of intraocular sodium hyaluronate had no apparent effect on intraocular pressure.

Aged↗
PubMed1993

[Behavior of the intraocular pressure after blunt eye injuries].

Elevation of intraocular pressure is often seen immediately after blunt trauma of the eye, but it can occur even years after the primary impact. A retrospective study was performed in 144 patients with contusion to the eye. After a mean observation period of 6.1 years, a significant rise in intraocular pressure was found in the engaged eye (P < 0.05). In more than 8% of the patients the level of intraocular pressure exceeded 22 mmHg, but only 3 cases developed a glaucomatous visual field and optic nerve head changes. Thus, the risk of secondary glaucoma after contusion of the eye is low.

Adolescent↗
PubMed2005

Intraocular pressure over the clinical range of blood pressure: blue mountains eye study findings.

PURPOSE: To quantify the relation of blood pressure (BP) and intraocular pressure (IOP) across the clinical range of BP in an older phakic population not using glaucoma medications. DESIGN: Cross-sectional population-based study METHODS: Seated BP and applanation IOP were measured, and their relation was assessed in regression models. RESULTS: Mean IOP of the two eyes increased linearly from 14.3 mm Hg for systolic BP <110 mm Hg to 17.7 mm Hg for systolic BP > or =200 mm Hg, a 3.4-mm Hg excursion over this range. Mean IOP also increased from 15.2 mm Hg for diastolic BP <70 to 18.4 mm Hg for diastolic BP > or =120, a similar variance. There were no changes after age and multivariate adjustments for IOP or after excluding undiagnosed glaucoma cases. CONCLUSION: A 3-mm linear IOP increase over the clinical spectrum of BP levels was evident; this variance is greater than with most other systemic and ocular parameters.

Blood Pressure↗
PubMedDate not supplied

Change in intraocular pressure during maturation in Labrador Retriever dogs.

OBJECTIVE: To measure intraocular pressure (IOP) in a group of dogs as puppies and young adults to determine if there is any change during maturation. Animals studied Thirty-two healthy Labrador Retriever dogs. PROCEDURES: Intraocular pressure was measured using a Tonopen XL initially at approximately 6 weeks of age (T1), then again approximately 1 year later (T2). Exact ages were known based on whelp date. RESULTS: The dogs had marginally higher IOP OU at T2 (mean = 14.9 mmHg) compared to T1 (mean = 13.4 mmHg). However, the difference was not statistically significant. No differences were seen based on sex and litter. Intraocular pressure OD was statistically greater than OS at T1 but not at T2. CONCLUSIONS: Normal values for intraocular pressure are the same in puppies and adults. The results of this study do not support the previously suggested theory that younger dogs have sustained increased IOP as a requirement to drive growth of the globe. However, it does not rule out the possibility that a dynamic relationship between intraocular pressure and expansion of the globe may exist.

Animals↗
PubMed1994

The contralateral reduction of intraocular pressure by timolol.

Administration of timolol to one eye is associated with a decrease in intraocular pressure in both eyes. To further investigate this effect the contralateral decrease in intraocular pressure was measured in a three arm crossover study using a 0.1 mg dose of timolol given topically to an eye, a 0.1 mg dose of timolol given lingually, and a placebo given topically. Two hours after topical timolol administration the mean intraocular pressure reduction in the fellow eye was 3.1 mm Hg compared with baseline (p = 0.0007). Two hours after lingual timolol administration the mean intraocular pressure reduction was 3.9 mm Hg compared with baseline (p = 0.0004). Two hours after topical administration of placebo the mean intraocular pressure reduction in the fellow eye was only 0.33 mm Hg (p = 0.6). These findings suggest the contralateral reduction in intraocular pressure from timolol is caused by systemic absorption. The significant intraocular pressure reduction obtained from lingual timolol raises the possibility that this route of drug administration may be useful in selected patients who cannot use eye drops.

Administration, Topical↗
PubMed2001

[Technical construction, calibration and results with a new intraocular pressure sensor with telemetric transmission].

BACKGROUND: Presently intraocular pressure is measured indirectly by applanation or impression of the cornea. Only isolated values are available with this method. We present a new implantable system for direct and continuos measurement of the intraocular pressure. METHODS: An implantable system consisting of a miniaturized sensor and a telemetric unit was integrated in an intraocular lens. The eye pressure is determined by the sensor, modulated and transduced by the telemetric system. By an extracorporal receiver the signal is demodulated. The electric supply of the intraocular system is achieved by external electromagnetic induction. RESULTS: The telemetric transmission of the intraocular pressure can be achieved with an accuracy of +/- 1 mm Hg and a frequency of registration of 3 values per second. CONCLUSION: Clinical application necessitates further animal trials in vivo.

Calibration↗