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PubMed1988

Autonomic drug effects after chronic lowering of ocular cholinergic input. II. Intraocular pressure responses.

Cholinergic input to the anterior segment of the eye was chronically reduced by ciliary ganglionectomy in cats and by treatment with hemicholinium-3 in both rabbits and cats. The parasympathetically denervated cat eyes developed super-sensitivity to the intraocular pressure lowering effects of carbachol and echothiophate. On the other hand, responsiveness to the similar effects of norepinephrine, epinephrine, and isoproterenol was not changed. After both acute and chronic treatment of rabbit eyes with hemicholinium-3, intraocular pressure was markedly lowered, but the facility of aqueous outflow after chronic treatment was not changed. During chronic treatment of cat eyes with hemicholinium-3, intraocular pressure was also lowered. Three days after chronic delivery of this acetylcholine synthesis inhibitor to the eyes of cats, the rate of formation of aqueous humor was reduced by 50 percent. These results suggest that chemical compounds lowering ocular cholinergic input may possess a pharmacological profile useful as an alternative means for the treatment of glaucoma.

Acetylcholine↗

PubMed1997

Intraocular pressure in 528 university students: effect of refractive error.

BACKGROUND: Very few studies measuring the intraocular pressure (IOP) in students are available. Recognizing the higher prevalence of myopia among students, IOP was analyzed in 528 university students according to age, gender, and refractive error. METHODS: The IOP was measured in 1,056 eyes with the Keeler Pulsair noncontact tonometer. The refractive error was determined with an autorefractometer (Shin-Nippon brand, model QR-007). RESULTS: The analysis of variance (ANOVA) showed no significant influence of age and gender on students' IOP (mean IOP, 15.77 +/- 2.67 mmHg). Refractive error did not significantly influence the mean of IOP (ANOVA) in the different categories: (a) severe myopia, (b) medium myopia, (c) emmetropia and mild ametropia, and (d) hypermetropia. The chi 2 test revealed significant differences, as a result of age, between the eyes with IOP < 21 mmHg or > or = 21 mmHg (6.3%). Nevertheless, there was no significant IOP difference as a result of gender or refractive error among eyes with normal IOPs and eyes with IOP above 20 mmHg. CONCLUSIONS: Among university students, intraocular pressure is not influenced by age, gender, or refractive status. Likewise, except for age, there is no significant correlation between any of the other variables and the normal range of IOP. After the age of 25 years, there is a slight increase in the number of eyes with an IOP above 20 mmHg.

Adolescent↗

PubMed1988

Intraocular pressure following ECCE, phacoemulsification, and PC-IOL implantation.

Abnormal intraocular pressure (IOP), either transient or permanent, may follow extracapsular cataract extraction (ECCE) with phacoemulsification (PE) and posterior chamber intraocular lens (PC-IOL) implantation. We retrospectively studied IOP measurements at different intervals post ECCE and PE in 242 eyes of 211 patients: 105 males, 106 females, 198 Caucasians and 13 blacks. Elevated IOP (greater than 23 mm Hg) was observed in 20 eyes (8.2%). Only two patients (0.8%) had persistent (greater than 3 months) IOP elevation and needed antiglaucoma therapy. Six more eyes (2.5%), however, developed glaucoma after 1 year. Hence, the incidence of secondary pseudophakic glaucoma at the conclusion of this study was 3.3%. No patient required laser or other mechanical surgery for IOP control. ECCE and PE with PC-IOL does not appear to adversely affect IOP. Patients, however, must be followed closely, as some may develop glaucoma months after surgery.

Adult↗

PubMed2005

Restoration of retinal ganglion cell function in early glaucoma after intraocular pressure reduction: a pilot study.

PURPOSE: To investigate the changes of pattern electroretinogram (PERG) after intraocular pressure lowering in glaucoma patients and normal controls. DESIGN: Interventional retrospective cross-sectional study. PARTICIPANTS: Twenty-five patients (49 eyes) with ocular hypertension or glaucoma undergoing topical treatment to lower IOP served as a study group; 22 patients (44 eyes) with ocular hypertension or glaucoma observed without treatment served as a control group for treated glaucoma patients; 9 normal subjects (18 eyes) receiving a 250-mg acetazolamide tablet served as a second study group; and 17 normal subjects (34 eyes) from a previous study served as a second control group for treated normal subjects. METHOD: Pattern electroretinograms were recorded simultaneously from both eyes using skin electrodes and automated analysis. Visual field (VF) analyses were performed with white-on-white standard automated perimetry (SAP). Intraocular pressure was measured with Goldmann applanation tonometry; central corneal thickness was measured with pachymetry. MAIN OUTCOME MEASURES: Pattern electroretinogram amplitude (microvolts), phase (pi rads), and test-retest variability (test 2-to-test 1 ratio, in decibels), SAP mean deviation (decibels), and IOP (millimeters of mercury). RESULTS: In 56% of right eyes and 21% of left eyes of the treated glaucoma subgroup, the PERG amplitude and/or phase improved beyond the 95% confidence intervals of the test-retest variability of the untreated glaucoma control group. Pattern electroretinogram improvement with IOP lowering occurred in both high- and low-tension glaucoma eyes. Eyes with severely impaired VFs showed little improvement in PERG; however, eyes of normal subjects treated with acetazolamide did not show significant PERG changes relative to the test-retest variability of normal controls. CONCLUSIONS: Retinal ganglion cell function can be at least partially restored after IOP reduction in glaucomatous eyes with early VF impairment.

Adult↗

PubMed1988

Comparison of intraocular pressure measurements with the Oculab Tono-Pen vs manometry in humans shortly after death.

We compared the Oculab Tono-Pen, a miniaturized Mackay-Marg tonometer, with a Statham membrane manometer in six humans (12 eyes), three to six hours after death. The intraocular pressure was changed in 5- to 10-mm Hg steps in a range between 0 and 60 mm Hg by an infusion system. The correlation coefficient of the relation of Tono-Pen readings vs manometrically determined intraocular pressures was .99. Compared to the manometer, the Tono-Pen gave a small underestimation of intraocular pressure above 17 mm Hg or overestimation below 17 mm Hg. The maximal deviation of the Tono-Pen readings from the manometer readings was 2.5 mm Hg. In our experience the correspondence between Tono-Pen and manometer readings was superior to the correspondence between the readings obtained with the original Mackay-Marg tonometer and manometry.

Aged↗

PubMed1995

Intraocular pressure rise after phacoemulsification with posterior chamber lens implantation: effect of prophylactic medication, wound closure, and surgeon's experience.

AIMS: A prospective clinical trial was carried out to evaluate the effect of prophylactic medication, the technique of wound closure, and the surgeon's experience on the intraocular pressure rise after cataract extraction. METHODS: In 100 eyes, the intraocular pressure was measured before as well as 2-4, 5-7, and 22-24 hours after phacoemulsification and posterior chamber lens implantation. Each of 25 patients received either 1% topical apraclonidine, 0.5% topical levobunolol, 500 mg oral acetazolamide, or placebo. Forty four eyes were operated with sclerocorneal sutureless tunnel and 56 eyes with corneoscleral incision and suture. Sixty three operations were performed by experienced surgeons (more than 300 intraocular operations) and 37 by inexperienced surgeons (less than 200 intraocular operations). RESULTS: The pressure increase from baseline to the maximum 5-7 hours after surgery did not differ significantly (p = 0.8499) for apraclonidine (9.5 mm Hg), levobunolol (7.2 mm Hg), acetazolamide (7.8 mm Hg), and placebo (8.6 mm Hg). The increase was significantly (p = 0.0095) lower in eyes with corneoscleral tunnel (5.5 mm Hg) than in eyes with corneoscleral suture (10.5 mm Hg) and significantly (p = 0.0156) lower for experienced (6.6 mm Hg) than for inexperienced surgeons (11.2 mm Hg). CONCLUSIONS: The intraocular pressure rise after phacoemulsification and posterior chamber lens implantation depends strongly on the technique of wound closure and the surgeon's experience. Compared with these two factors, the effect of prophylactic medication can be neglected.

Acetazolamide↗

PubMed1975

[The electrophysiological behavior of normal and glaucomatous human eyes with short term intraocular pressure elevation (author's transl)].

An electrophysiological study has been done on glaucomatous and normal eyes with briefly elevated intraocular pressure. There was no significant difference between the ERGs, but the changes in the VERs of glaucomatous eyes differed widely from those of normal eyes. This seems to be due to the high sensitivity to pressure of the prelaminary part of the optic nerve in glaucomatous eyes. Obviously this could be a method for the objective measurement of the sensitivity of the papillary vessels to raised intraocular pressure.

Blood Pressure↗

PubMed2006

Computerized invasive measurement of time-dependent intraocular pressure.

Several methods have been described to measure intraocular pressure (IOP) in clinical and research situations. However, the measurement of time varying IOP with high accuracy, mainly in situations that alter corneal properties, has not been reported until now. The present report describes a computerized system capable of recording the transitory variability of IOP, which is sufficiently sensitive to reliably measure ocular pulse peak-to-peak values. We also describe its characteristics and discuss its applicability to research and clinical studies. The device consists of a pressure transducer, a signal conditioning unit and an analog-to-digital converter coupled to a video acquisition board. A modified Cairns trabeculectomy was performed in 9 Oryctolagus cuniculus rabbits to obtain changes in IOP decay parameters and to evaluate the utility and sensitivity of the recording system. The device was effective for the study of kinetic parameters of IOP, such as decay pattern and ocular pulse waves due to cardiac and respiratory cycle rhythm. In addition, there was a significant increase of IOP versus time curve derivative when pre- and post-trabeculectomy recordings were compared. The present procedure excludes corneal thickness and error related to individual operator ability. Clinical complications due to saline infusion and pressure overload were not observed during biomicroscopic evaluation. Among the disadvantages of the procedure are the requirement of anesthesia and the use in acute recordings rather than chronic protocols. Finally, the method described may provide a reliable alternative for the study of ocular pressure dynamic alterations in man and may facilitate the investigation of the pathogenesis of glaucoma.

Animals↗

PubMed1985

The ocular pulse and intraocular pressure as a screening test for carotid artery stenosis.

The ocular pulse and applanation tension were measured with a recording applanation tonometer in 38 patients suspected of having internal carotid artery stenosis. Abnormalities of the ocular pulse amplitude, intraocular pressure, or combinations of these two measurements were found in 23 (82%) of 28 patients who were subsequently found to have angiographic evidence of 50% or more stenosis of one or both internal carotid arteries. Of 10 patients without angiographic evidence of carotid stenosis the ocular pulse amplitude, intraocular pressure, or both were abnormal in five, but two patients had an ocular cause for abnormality and two of the remaining three had evidence of carotid disease in the form of atheromatous plaques. These results suggest that measurement of the amplitude of the ocular pulse in addition to the intraocular pressure can predict the presence of carotid artery stenosis and indicate the need for further investigation. If a tonometer capable of measuring the pulse amplitude was used routinely in ophthalmic examinations, it would provide a useful screening test for the early diagnosis and treatment of carotid artery disease and might thereby reduce the frequency of strokes.

Arterial Occlusive Diseases↗

PubMed2001

Intraocular pressure after homologous penetrating keratoplasty.

PURPOSE: To evaluate intraocular pressure (IOP) changes after homologous central penetrating keratoplasty in a noncomparative interventional case series. METHODS: The study included 245 patients undergoing homologous central penetrating keratoplasty for keratoconus (n = 77), herpetic corneal scars (n = 29), nonherpetic corneal scars (n = 46), Fuchs endothelial dystrophy (n = 24), and secondary corneal endothelial decompensation caused by preceding intraocular operations (n = 69). Mean follow-up time was 30.4 +/- 18.7 months (range, 12.1-111.6 months). The same surgeon operated on all patients, and a peripheral iridotomy was routinely performed. RESULTS: On the first postoperative day, IOP was significantly (P = 0.02) higher than that before keratoplasty. Taking the whole study group and taking the study groups separately, IOP measurements determined on the third postoperative day (P = 0.57), 1 week after surgery (P = 0.55), or later (P > 0.50) were not significantly different from the preoperative values. Eyes undergoing keratoplasty with cataract surgery and eyes undergoing keratoplasty without additional intraocular procedures did not vary significantly (P > 0.10) in IOP measurements. IOP did not differ significantly (P > 0.50) between eyes with an immunologic graft reaction (n = 29) and eyes without a reaction (n = 216). Acute angle-closure glaucoma was not detected in any of the patients. IOP measurements were statistically independent of suture type (P > 0.10), age (P > 0.05), preoperative and postoperative refractive error (P > 0.05), preoperative and postoperative corneal astigmatism (P > 0.10), preoperative and postoperative visual acuity (P > 0.10), diameter of graft and trephine (P > 0.15), and oversize of the graft (P > 0.50). Postoperative IOP measurements were significantly (P < 0.01) correlated with preoperative IOP values. CONCLUSIONS: In eyes with a peripheral iridotomy performed during surgery, homologous central penetrating keratoplasty usually does not markedly change IOP. The main risk factor for postoperatively increased IOP is increased IOP before surgery.

Adolescent↗

PubMed2005

Corneal thickness and daily curve of intraocular pressure in suspected and glaucomatous patients.

PURPOSE: To evaluate in suspected and glaucomatous patients the correlation between central corneal thickness (CCT) and intraocular pressure (IOP), measured during the daily curve of intraocular pressure (DCPo), including CCT and IOP measurements in bed at 6 am. The ocular axial length was also compared. METHODS: 114 eyes from 73 patients, 30 eyes suspected of glaucoma (group I) and 84 eyes with chronic open-angle glaucoma (group II) were prospectively studied. Both groups were subjected to DCPo with measurements of IOP at 9 am, 12 pm, 6 pm, 10:30 pm and on the next day at 6 am in bed and in darkness before the patient gets up. Using the ultrasonic DGH 5100 device, CCT measurements were performed at 9 am, 6 pm, 10:30 pm and the next day at 6 am in bed before the patient gets up. The ocular axial length was also measured. RESULTS: In the total sample and, separately in each group, the mean IOP was more elevated in bed at 6 am. There were no significant CCT changes during the day within each group or between both groups. No statistically significant difference was found between the mean ocular axial length of both groups. CONCLUSIONS: In suspected and glaucomatous patients, there were no statistically significant CCT variations during the day; therefore, only one CCT measurement is sufficient. Also, there was no statistically significant difference between ocular axial length of both groups.

Chronic Disease↗

PubMed1994

The effect of posture on intraocular pressure and pulsatile ocular blood flow in normal and glaucomatous eyes.

While an increase in the intraocular pressure on assumption of the supine position from the seated or upright position has been known for decades, the recent introduction of a means to quantify the pulsatile ocular blood flow has led to studies indicating a postural decrease in the pulsatile ocular blood flow. The factors contributing to the postural response of the intraocular pressure are reviewed, and those proposed for the postural response of the pulsatile ocular blood flow are discussed.

Blood Flow Velocity↗

PubMed1985

The effect of ocular pigmentation on intraocular pressure response to timolol.

The one-hour intraocular pressure (IOP) response to topical ocularly applied timolol was studied in darkly and lightly pigmented eyes. One drop of 0.25% 1-timolol was applied to one eye of ten subjects with brown and ten subjects with blue iris color. In the treated and untreated eyes with blue iris color the IOP fell significantly from the baseline value, whereas no pressure reduction was obtained either in the treated or untreated eyes with brown iris color. Beta-blocking agents are known to accumulate in pigment-containing ocular structures. The lack of a one-hour pressure response to timolol in darkly pigmented eyes observed in our study may refer to the reduction of 1-timolol in the biophase due to excessive pigment binding.

Adult↗

PubMed1993

Elevated intraocular pressure and pseudoexfoliation of the lens capsule as risk factors for chronic open-angle glaucoma. A population-based five-year follow-up study.

In 1984-86, a glaucoma survey was carried out in a municipality in central Sweden, comprising 760 subjects 65-74 years of age. Since 1988, a follow-up study of those 527 subjects who had normal and reliable visual fields has been in progress. A visual field defect was required for a diagnosis of chronic open-angle glaucoma. By December 1991, 10 cases of capsular glaucoma and 3 cases of chronic simple glaucoma had been found. The standardized relative risk for chronic open-angle glaucoma was 3.4 times (95% confidence interval: 1.1-11) greater in subjects with a baseline intraocular pressure > or = 21 mmHg, using the highest pressure in either eye, than in those with an intraocular pressure < 21 mmHg. Pseudoexfoliation increased the standardized relative risk 9.8-fold (95% confidence interval: 2.5-38). There was indication of effect modification between intraocular pressure and pseudoexfoliation. Optic disc haemorrhages were associated with a 4.8-fold (95% confidence interval: 0.63-37) increased unadjusted risk. The study supports the pressure theory of optic nerve damage in glaucoma. Pseudoexfoliation was recognized as an independent risk factor for the development of chronic open-angle glaucoma.

Aged↗

PubMed1994

Evidence for a new role of natriuretic peptides: control of intraocular pressure.

To study the possible physiological role of atrial natriuretic peptide (ANP) in the regulation of intraocular pressure (IOP) the effects of an increase of endogenous ANP within the physiological range induced by the neutral endopeptidase 24.11 (NEP) inhibitor candoxatril were examined. In a single masked placebo controlled trial, seven patients were studied with normal IOP (six male, one female; average age 50 (range 37-62 years). Intraocular pressure in each eye was measured after 2 weeks of placebo, after 4 weeks of candoxatril 200 mg twice daily, and during the first 3 days of placebo washout. With 4 weeks of candoxatril, endogenous plasma ANP levels increased from 4.2 (SEM 1.5) to 6.0 (1.5) pmol/l (p < 0.04) and there was a significant decrease in mean arterial pressure from 119 (4) to 110 (3) mm Hg (p < 0.02; 12 hours after treatment). There was a significant reduction in IOP after 4 weeks' treatment with candoxatril (right eye 2.1 (0.8) mm Hg, p < 0.05 paired t test, left eye 2.8 (0.8) mm Hg, p < 0.02). The mean fall in IOP was 11% (4%) in the right eye and 16% (3%) in the left eye and the fall in IOP was greater the higher the initial IOP. The reduction in IOP with chronic NEP inhibition was positively correlated with the increase in ANP levels but not with changes in blood pressure. These findings suggest that ANP may play a physiological role in the regulation of IOP. As the fall in IOP was greater in subjects with higher initial IOP, NEP inhibitors may be of therapeutic value in the management of glaucoma.

Adult↗

PubMed2006

Long-term effects of mild exercise on intraocular pressure in athletes and sedentary subjects.

The long-term effects of acute submaximal exercise on intraocular pressures (IOPs) of right-and left-eyes and recovery times to basement levels of IOP in postexercise periods in sedentary and physically fit subjects were investigated. Twenty-five sedentary and 24 physically fit subjects, ranging in age 17 to 22 years, participated. Intraocular pressures were measured by a pneumotonometer. Measurements were taken in the morning at about nine (at rest) and immediately, 30 min and 2 h after acute submaximal exercise. In sedentary subjects, IOPs of both right- and left-eyes decreased immediate after exercise, but, these decreases in both eyes continued 30 min and 2 h after exercise. In physically fit subjects, IOPs of both right- and left-eyes increased immediate after exercise, but decreased after 30 min exercise compared to basement levels, and this decrease continued 2 h after exercise. Acute submaximal exercise decreased IOPs of right and left eyes over a period 2 h in sedentary and physically fit subjects. IOP reducing after exercise was different between right- and left-eyes in sedentary subjects. These results suggest that exercise can be used in ocular hypertension treatment.

Adolescent↗

PubMed1997

Associations with intraocular pressure in the Barbados Eye Study.

OBJECTIVE: To evaluate the demographic, medical, ocular, familial, and other factors possibly associated with intraocular pressure (IOP) in a black population, after excluding persons with any type of glaucoma. DESIGN: The Barbados Eye Study was a population-based study of a random sample of residents of Barbados, West Indies, aged 40 to 84 years. PARTICIPANTS: A subset of the Barbados Eye Study population consisting of 3752 black Barbados Eye Study participants without glaucoma. DATA COLLECTION: A standardized protocol included applanation tonometry and other ocular data, blood pressure measurements, anthropometry, complexion pigmentation gradings, and a comprehensive interview. MAIN OUTCOME MEASURE: Intraocular pressure was based on the average of 3 measurements at the Barbados Eye Study visit. Multiple linear regression was used to evaluate factors associated with IOP. RESULTS: Systolic blood pressure (or hypertension), diabetes history, and age were the major factors positively associated with IOP (P<.01). Other positively related factors were female gender, darker complexion, pulse rate, higher body mass, seasonality, family history of glaucoma, current alcohol use, and current smoking. These factors explained 10% of the variation in IOP. CONCLUSIONS: By identifying risk factors, these results define specific subgroups most likely to have an elevated IOP. The high IOP in this population may be linked to the high prevalence of hypertension and diabetes. Aside from age and a family history of glaucoma, none of the risk factors for high IOP evaluated in this study was similar to those associated with open-angle glaucoma.

Adult↗

PubMed1992

Hydrodynamic analysis of intraocular pressure changes during anterior chamber procedures.

Variations in intraocular pressure (IOP), observed by us and other authors in closed-system anterior chamber procedures, are explained using a simple hydrodynamic analysis based on the Bernoulli equation. Calculations show that the sudden increases in IOP (pressure spikes) measured during anterior segment surgery are due primarily to the small size of the infusion cannulas and are exacerbated by high infusion rates. Accurate measurement of these IOP variations requires placement of the pressure sensors in situ and is not possible by remote pressure sensing at the infusion line or the console. This work indicates that closed-system procedures could benefit from accurate monitoring of intraoperative IOP and could use these measurements for automatic IOP control during surgery.

Animals↗