Fluctuations in intra-ocular pressure with sleep:I. Time course of IOP increase after the onset of sleep

Ten normal subjects slept over a series of four nights for time periods of 30 minutes, 1, 2 and 4 hours. Intra-ocular pressure (IOP) measurements were made using a non-contact tonometer before and after sleep. The subjects showed a significant increase in IOP of 3.45 mm Hg after 30 minutes of sleep and a further IOP increase thereafter to 6.41 mm Hg above baseline. Such increases in IOP after sleep in normal subjects suggest that glaucoma patients and those suspected of having glaucoma should be monitored overnight to assess their IOP control mechanisms.     

Diurnal variation of intraocular pressure and the overriding effects of sleep

Intraocular pressure (IOP) was recorded regularly over a 24-h period in 13 normal subjects. All subjects showed a dramatic rise in IOP after sleep, ranging from 37 to 248%. In a second experiment, IOP decreased when 15 subjects remained upright and awake throughout the night. When sleep was not permitted IOP was lowest at 3:00 a.m. (0300); when six of these subjects were permitted to sleep from 0600 to 0800, they showed a rapid and significant increase in IOP of up to 150%, whereas the remaining nine subjects showed (posturally induced) increases of up to 38%.     

Fluctuations in intra-ocular pressure with sleep:

Intra-ocular pressure (IOP) was measured immediately after normal subjects were woken from at least 5 hours sleep. Measurements were made at approximately 15 s intervals, for about 20 minutes. The IOP of all 14 subjects was elevated after sleep and returned to baseline levels with a time course which was approximately exponential; the longest time constant of return of IOP to baseline was 1056.9 s, and the shortest 133.5 s. Mean time constant of recovery was 404.8 s. The decrease in IOP may be related to melatonin levels which increase during sleep and decrease in the light, or be related to accommodation and eye movements which may act to 'pump' aqueous from the eye.     

Repeatability and effects of sequential measurements with POBF tonograph.

AIMS: (1) To investigate the effect of performing sequential measurements using a Pulsatile Ocular Blood Flow (POBF) Tonograph on POBF and intraocular pressure (IOP) measurements; (2) to determine any effect on IOP caused by performing POBF measurements on the fellow eye; and (3) to assess repeatability of measurements obtained using the POBF Tonograph. METHODS: Forty-six normal adult subjects (13 men, 33 women; age range, 18 to 55 years) took part in the present study. Twenty-one subjects underwent sequential measurements with a POBF Tonograph on five different occasions with five different time intervals (1, 2, 5, 10, and 15 minutes) between recordings. Twenty subjects underwent a baseline measurement on one eye with the POBF Tonograph, followed by repeat measurements in both eyes after 15 minutes. An additional 25 subjects underwent sequential measurements on the same eye with an interval of 15 minutes between readings. The intraclass correlation coefficient and Bland-Altman plots were used to assess repeatability of the instrument for all 46 subjects for the 15-minute time interval. RESULTS: In all the groups, repeated measurement resulted in a lower recorded IOP. A multivariate analysis of variance indicated that there was a significant decrease in IOP when measurements were repeated within 15 minutes (p=0.024), but there was no significant change in the POBF values (p=0.76). The recorded IOP was significantly lower when sequential measurements were performed with an interval of 1 minute (p <0.01) compared with longer time intervals. The decrease in IOP between baseline and the repeat measurement was significantly greater in the 1-minute interval group compared with the 15-minute interval group (p <0.005). There was no significant difference in POBF values between the baseline and repeat measurements in any group. There was no significant change in IOP induced by a single measurement on the fellow eye (p >0.05). The intraclass correlation coefficient value indicated good agreement between the values of the baseline and repeat measurements using the POBF Tonograph but had wide upper and lower limits of agreement. CONCLUSION: If IOP measurements have to be repeated using the POBF Tonograph, they are best done after an interval of at least 2 minutes and preferably after 15 minutes. Use of the POBF Tonograph had no significant immediate effect on the IOP or POBF values obtained from a fellow eye.     

Reversal of intraocular pressure increases with 0.5% apraclonidine after dilated fundus examination in patients with chronic open-angle glaucoma.

BACKGROUND: Apraclonidine 1.0% has been shown to reverse the potential intraocular pressure (IOP) increase after pupil dilation IOP increases in patients with chronic open-angle glaucoma. However, it is only approved for preventing IOP spikes after laser surgery. The purpose of this study is to determine the effectiveness of 0.5% apraclonidine in reversing IOP increases after pupillary dilation in patients with chronic open-angle glaucoma. METHODS: Twenty-two patients with chronic open-angle glaucoma were found to have an increase in post-dilation IOP of at least 4 mmHg from pre-dilated levels (baseline) in both eyes. IOP was measured 1 hour after dilation, after which two drops of 0.5% apraclonidine were instilled in one eye and the IOP was remeasured 15 minutes later in both eyes. Instillation of 0.5% apraclonidine in one eye was continued every 15 minutes and IOP was measured 15 minutes after each instillation, until the pressure returned to baseline levels. RESULTS: The IOP of the initially treated eye of all 22 patients returned to within levels clinically insignificant from baseline IOP within 90 minutes. By comparison, the IOP of the control group (untreated eye) remained elevated. Once the initial treatment eye returned to baseline levels, the control group was then treated with 0.5% apraclonidine, resulting in a lowering effect of the IOP in similar fashion to the initial treated group. CONCLUSIONS: Apraclonidine 0.5% appears to be effective in reduction of post-dilated IOP increases in patients with chronic open-angle glaucoma.     

Twenty-four-hour pattern of intraocular pressure in young adults with moderate to severe myopia

PURPOSE: To characterize the 24-hour change of intraocular pressure (IOP) in young adults with moderate to severe myopia. METHODS: Nineteen young adults, ages 18 to 25 years, with moderate to severe myopia (myopia group) and 17 age-matched volunteers with emmetropia or mild myopia (control group) were housed for 1 day in a sleep laboratory. An 8-hour accustomed sleep period was assigned to each volunteer. Twelve measurements of IOP, axial length, blood pressure, and heart rate were taken at 2-hour intervals. In the wake period, blood pressure and heart rate were measured after a 5-minute bed rest. Axial length and IOP were measured in supine volunteers. Volunteers then sat for 5 minutes, after which IOP was measured. In the sleep period, measurements were taken in supine volunteers in bed. RESULTS: In both the myopia and control groups, the average supine IOP in the sleep period was higher than the average sitting IOP in the wake period. However, the magnitude of this IOP elevation at night was significantly less in the myopia group. In the sleep period, IOP was less in the myopia group than in the control group. When only the 24-hour supine IOP data were considered, the trough occurred at 1:30 AM, and the peak occurred around noon in the myopia group. In the control group, the trough was at 9:30 PM, and the peak at 5:30 AM. Least-square cosine fits showed 24-hour rhythms of supine IOP in both groups, but their phase timings were different. Axial length remained unchanged throughout the day and night in both groups. There was no difference in the 24-hour rhythms of mean blood pressure and heart rate between the two groups. CONCLUSIONS: Considering habitual body positions, IOP increases at night in young adults with moderate to severe myopia, but the magnitude of the increase is significantly less than that in the age-matched control subjects. There is a 24-hour rhythm of supine IOP in the myopic group, but the phase timing is different from that in the control subjects. These variations of IOP in young adults with moderate to severe myopia are not related to changes in cardiovascular parameters.     

Diurnal variation of intraocular pressure of normal-tension glaucoma. Influence of sleep and arousal

The measurement of the diurnal variation of intraocular pressure (IOP) is indispensable for the diagnosis of normal-tension glaucoma (NTG). To determine the diurnal variation of IOP, its measurement has to be made repeatedly for 24 hours, which interferes with patients's sleep at night and may influence the physiologic IOP variation. The authors studied the IOP variation in 82 NTG suspects, whose IOP was first measured every 2 hours for 24 hours. The following night they were suddenly aroused without any notice and IOP was measured. The diurnal IOP variation of NTG patients was found to be similar to that of the normal population and there was no significant difference in the IOP values at the same time points on the two successive nights. Sleep may have little, if any, influence on diurnal IOP variation in NTG patients.     

Investigation of parameters influencing intraocular pressure increases during sleep

In previous studies, we have observed that young normal subjects show an increase in intraocular pressure (IOP) after sleep. Here we describe three experiments which investigated: (i) the effects of sleep in five groups of subjects: glaucoma, suspect glaucoma, young high-normal IOP, old high-normal IOP groups and an elderly control group, (ii) the effect of exposure to bright light (2500 lux) during sleep on associated IOP changes, and (iii) the relationship between changes in IOP and plasma melatonin during sleep, For all experiments IOP was measured before and after sleep. We found that IOP increased significantly after sleep. There was also a significant difference between the five groups with the old high-normal group showing the greatest increase, and the young high-normal group showing the lowest increase in IOP. The increase in IOP after sleep was reduced when the same subjects slept in bright light compared to that recorded when subjects slept in the dark. Plasma melatonin levels, as well as IOP, increased after sleep in the dark although there was no correlation between these changes for individual subjects.     

Effect of Topical Phenylephrine 2.5% on Episcleral Venous Pressure in Normal Human Eyes

PurposePhenylephrine has been shown to affect intraocular pressure (IOP) but the mechanism of action is poorly understood. However, its action as a vasoconstrictor suggests possible effects on episcleral venous pressure (EVP). In this study, we evaluated the effect of phenylephrine on EVP and IOP in healthy subjects.MethodsForty eyes of 20 subjects were included. Each subject received 3 drops of phenylephrine 2.5% in one eye at 1-minute intervals. The fellow eye served as control. Blood pressure, heart rate, and IOP and EVP of both eyes were measured at baseline, 15 minutes, and 60 minutes after instillation of phenylephrine. IOP was measured by pneumatonometry. EVP was assessed by using a computer-controlled episcleral venomanometer. Changes in IOP, EVP, blood pressure, and heart rate at 15 and 60 minutes were analyzed by paired t-tests.ResultsIOP increased 15 minutes after instillation of phenylephrine in both treated (P = 0.001) and control eyes (P = 0.01) and returned to baseline at 60 minutes. The change in IOP at 15 minutes was not significantly different between the 2 groups. EVP in treated eyes was unchanged at 15 minutes (P = 0.8) but decreased significantly at 60 minutes (P < 0.001). In control eyes, there was no change in EVP at any time (P > 0.6). There were no significant changes from baseline in systolic and diastolic blood pressure and heart rate after instillation of phenylephrine.ConclusionsIOP elevation associated with topical phenylephrine is not caused by an increase in EVP in healthy subjects. Instead, EVP decreases with phenylephrine, but the mechanism remains to be determined.     

Ibopamine provocative test and glaucoma: consideration of factors that may influence the examination

PURPOSE: To evaluate factors that may influence the ibopamine provocative test for the diagnosis of glaucoma. METHODS: Two Ibopamine (3,4 di-isobutyrylester of N-methyldopamine) 2% eyedrops were instilled 5 minutes apart in one eye selected at random in both glaucoma and normal subjects. The intraocular pressure (IOP) was assessed prior to the drops and 30, 60 and 180 minutes after instillation. The test was considered positive when there was an IOP increase of greater than 4 mmHg at any one of the timepoints. The amount of IOP change was compared to the severity of glaucomatous visual field loss and to the types of medical treatment. RESULTS: The sensitivity (glaucoma patients with a positive result) and specificity (normal individuals with a negative result) of the Ibopamine test was 87 and 95%, respectively. Glaucoma patients using prostaglandin analogues did not have a significant IOP elevation. CONCLUSION: The Ibopamine provocative test may be an auxiliary test in glaucoma diagnosis. Concurrent use of prostaglandin analogues reduces the test's sensitivity.     

Continuous positive airway pressure therapy is associated with an increase in intraocular pressure in obstructive sleep apnea

PURPOSE: Several reports have demonstrated an association between glaucoma and obstructive sleep apnea (OSA), though the origin of this association remains unknown. In the present study, the influence of OSA and continuous positive airway pressure (CPAP) therapy on intraocular pressure (IOP) and ocular perfusion pressure (OPP) was examined. METHODS: IOP, blood pressure, and pulse rate were measured every 2 hours during 24-hour sessions in 21 patients with newly diagnosed OSA. A first series of measurements was performed before CPAP therapy, and a second series was performed 1 month after the initiation of CPAP therapy. OPP was then calculated. RESULTS: Baseline measurements showed a significant nycththemeral fluctuation in the average IOP, with the highest IOPs at night. After 1 month of CPAP therapy, the average IOP was significantly higher than baseline. The increase in overnight IOP was also significantly higher. A 24-hour IOP fluctuation of > or =8 mm Hg was found in 7 patients at baseline and in 12 patients during CPAP therapy. The mean difference between trough and peak IOP was 6.7 +/- 1.5 mm Hg at baseline and 9.0 +/- 2.0 mm Hg during CPAP therapy. Thirty minutes after CPAP cessation a significant decrease in IOP was recorded. There was a statistically significant decrease in mean OPP during CPAP therapy. CONCLUSIONS: Patients with OSA demonstrated significant 24-hour IOP fluctuations, with the highest values at night. CPAP therapy causes an additional IOP increase, especially at night. Regular screening of visual fields and the optic disc is warranted for all patients with OSA, especially those treated with CPAP.     

Twenty-four-hour time course of intraocular pressure in healthy and glaucomatous Africans: relation to sleep patterns

OBJECTIVE: The study was performed in early middle-aged African natives with primary open-angle glaucoma to compare the 24-hour intraocular pressure (IOP) variations in healthy versus young glaucoma patients, because IOP follows a circadian (24-hour) oscillation in healthy Caucasians. DESIGN: Case-control study. PARTICIPANTS: Sixteen healthy African volunteers (age 24.5 +/- 1 years, mean +/- standard error of the mean) and 11 open-angle glaucoma African patients (age 36.2 +/- 3.3 years). METHODS: IOP was measured hourly during 24 hours with a Modular One pneumatonometer (Modular One, Digilab, Cambridge, MA), which allows measures in supine subjects. To allow the IOP measurement at night, subjects were awakened under polysomnography (electroencephalogram, electromyogram, electro-oculogram) recorded at night and during a 90-minute afternoon nap. MAIN OUTCOME MEASURES: Hourly IOP values were analyzed for circadian rhythmicity with the Cosinor technique and in relation to the state of wakefulness, light sleep (stages 1 and 2), slow-wave sleep (stages 3 and 4), and rapid eye movement (REM) sleep upon awakening. RESULTS: Sleep patterns did not differ between patients and healthy volunteers. As expected, in the healthy subjects, IOP followed a 24-hour rhythm with a nocturnal peak value (acrophase), and the variations in IOP during sleep were related to sleep structure, being lowest during REM sleep and highest during slow-wave sleep. In the glaucoma patients, however, the 24-hour rhythm of IOP was reversed, with an afternoon acrophase and an early morning trough. CONCLUSIONS: These data suggest a circadian phase shift in IOP in glaucoma patients, with maintained relation to sleep structure.     

Effects of ibopamine eye drops on intraocular pressure and aqueous humor flow in healthy volunteers and patients with open-angle glaucoma

PURPOSE: On the basis of intraocular pressure measurements and fluorophotometry we assessed the effects of 2% ibopamine eye drops on aqueous humor production in normal and glaucomatous eyes. METHODS: Thirty subjects (15 healthy volunteers and 15 open-angle glaucoma patients with ocular hypertension) were included in a placebo-controlled study with random assignment of treatment from masked containers. All subjects underwent ophthalmologic examinations and intraocular pressure (IOP) measurements. Fluorophotometry was done in both eyes at baseline (without treatment) and during treatment. Each subject was treated with 1 drop of 2% ibopamine in one eye and 1 drop of placebo in the fellow eye 30 minutes before fluorophotometric scans and every hour after the first instillation (for a total of 4 times). Safety was evaluated by recording adverse events and ocular symptoms and signs. Aqueous humor flow data were analyzed using the paired t-test, comparing ibopamine and placebo-treated eyes. RESULTS: No changes in IOP were detected in normal eyes, whereas glaucomatous eyes showed a mean increase of 4 mmHg (95% CI 3.46-4.51) from baseline. The difference in IOP between healthy eyes and those with glaucoma was significant (p < 0.0001). In normal eyes and patients with glaucoma ibopamine led to a significant increase in aqueous humor flow compared with placebo-treated eyes (p < 0.01). The safety profile of ibopamine was very good. CONCLUSIONS: The results seem to confirm that ibopamine increases aqueous humor production in normal and glaucomatous eyes, raising IOP only in eyes with glaucoma.     

Intraocular pressure effects of timolol after unilateral instillation

Beta-adrenergic antagonists are generally considered to lower intraocular pressure (IOP) of both eyes after unilateral instillation. In order to determine whether timolol also lowers IOP in the contralateral eye and to what extent, pressure curves were established in 14 normal, young subjects. Eye pressure curves on both eyes of each subject were measured before and 1 week after timolol 0.5% instillation twice daily in one eye. All subjects had an IOP decrease in the treated eye, but no subjects had a statistically significant IOP decrease in the contralateral eye. The mean IOP reduction was 26% in the treated eye, and only 3% in the contralateral eye. These results suggest that, in most cases, timolol does not lower IOP in the contralateral eye after unilateral instillation in normal subjects in contrast to certain glaucoma patients. These results suggest two different actions for timolol: (1) a local action in the treated eye, and (2) a systemic action where the pressure-lowering effect in the untreated eye is significant only in some pathologic conditions.     

24小时眼压监测中夜间眼压测量方法的探讨

目的比较24h眼压监测中夜间即刻坐位眼压值和坐起休息10min后测得的眼压值,探讨夜间眼压的不同测量方法对青光眼24h眼压昼夜波动的影响。方法对已确诊且未用药、未做过手术的48例正常眼压性青光眼及17例原发性开角型青光眼患者进行24h眼压监测,每2h1次,其中测量夜间0:00、2:00、4:00眼压时,逐个唤起患者后立即测,后嘱患者坐起休息10min再测,采用SPSS软件以配对t检验分析比较测量结果。结果夜间即刻坐位眼压值和坐起休息10min后测得的眼压值差异有统计学意义(P<0.001),正常眼压性青光眼与原发性开角型青光眼间眼压差值差异有统计学意义(P<0.05)。结论即刻坐位眼压值能更准确反映夜间眼压,对24h眼压测量及青光眼诊断及治疗更有价值,值得临床应用。     

Effects of scleral search coil wear on visual function

PURPOSE: The scleral search coil is widely regarded as the gold standard measurement technique for eye movements. The effect of wearing scleral search coils on human vision has not been systematically studied. However, there are anecdotal reports of degraded visual acuity, mild eye irritation, and an increase rise in intraocular pressure (IOP). The current study was conducted to investigate the effect of scleral search coil use on visual acuity and ocular integrity. METHODS: Six subjects were examined; all had previously worn search coils. Two drops of topical anesthetic were administered before insertion of the coils. Coils were inserted by hand and secured by applying mild pressure. The coils were removed after 45 minutes or on request of either the subject or the clinician. Before, during (at 15-minutes intervals), and after the coil was worn, the following measurements were taken for both eyes: tonometry (noncontact), corneal topography, biomicroscopic examination, visual acuity (monocular Snellen), and an eye-discomfort rating. RESULTS: Scleral coils produced a variety of effects, including ocular discomfort, hyperemia of the bulbar conjunctiva, increased IOP, buckling of the iris, grade 2 and 3 corneal staining, and reduction in visual acuity. Effects appeared as early as 15 minutes after insertion of the coils. All observed effects seemed to be transient and dissipated after coils were removed. CONCLUSIONS: Scleral coils may not be appropriate for all subjects. The findings suggest that there is a need for thorough subject prescreening and that clinicians should consider the risk/benefit ratio. Acute reduction in visual acuity may confound search coil findings. More research is needed to determine the maximum wearing time for properly screened subjects.     

The effects of cyclopentolate on intraocular pressure and retrobulbar hemodynamics in patients with pseudoexfoliation syndrome and pseudoexfoliation glaucoma

PURPOSE: To evaluate the changes of intraocular pressure (IOP) and retrobulbar hemodynamics after cyclopentolate administration in patients with pseudoexfoliation syndrome and pseudoexfoliation glaucoma. METHODS: Eighteen patients with pseudoexfoliation syndrome and 18 patients with pseudoexfoliation glaucoma were enrolled in the study. After baseline measurements of IOP, the peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistivity index (RI) of the ophthalmic, central retinal, and posterior ciliary arteries were investigated by color Doppler imaging. Then, 1% cyclopentolate was instilled in one eye of each subject. After 45 minutes of instillation of the cyclopentolate, the measurements of IOP and retrobulbar blood flow velocities were repeated. The results were compared with those of 20 age-matched normal subjects. RESULTS: Neither IOP nor retrobulbar blood flow velocities changed significantly in control subjects after cyclopentolate administration. IOP increased significantly after cyclopentolate instillation in pseudoexfoliation syndrome (p = 0.004). Retrobulbar blood velocities did not change significantly after the cyclopentolate in this group. In pseudoexfoliation glaucoma group, it was observed that basal mean IOP showed a statistically significant increase after cyclopentolate drop (p = 0.002). Although blood flow velocities of ophthalmic artery did not change significantly, PSV and EDV of the central retinal and posterior ciliary arteries decreased significantly (p < 0.05) and RI of the posterior ciliary artery increased significantly (p = 0.01) after cyclopentolate instillation. CONCLUSIONS: On the basis of our findings, pseudoexfoliation appears to be a predictive factor for an IOP rise after cyclopentolate. In pseudoexfoliation glaucoma patients, an increase of IOP after cyclopentolate could lead to a decreased retrobulbar blood flow. IOP must be rechecked after cyclopentolate administration in these patients to avoid further damage to the ganglion cells.     

不同麻醉方式对眼压和眼脉动振幅的影响

目的比较球后麻醉和眼球筋膜囊下麻醉对眼压及眼脉动振幅（OPA）的影响。方法顺贯性选择单眼白内障40例,分别作球后麻醉和眼球筋膜囊下麻醉（各20例）。术眼为试验组,另眼设为对照。分别于麻醉前及麻醉后1min、10min采用轮廓动态眼压计（DCT）测量眼压及OPA。结果注射利多卡因后球后麻醉组注射眼的眼压升高。眼球筋膜囊下麻醉注射眼和对照眼的眼压均无明显变化。两组注射眼OPA值均显著降低,眼球筋膜囊下麻醉后10min对照眼OPA值降低,球后麻醉后1min对照眼OPA值升高,10min后恢复至注射前水平。结论球后麻醉可降低眼脉动振幅,使眼压升高;眼球筋膜囊下麻醉降低眼脉动振幅,对眼压则无明显影响。     

Effect on intraocular pressure of local anaesthesia in eyes undergoing intraocular surgery.

A total of 104 eyes undergoing intraocular surgery were studied to investigate the effect on intraocular pressure (IOP) of peribulbar and retrobulbar anaesthesia in eyes with and without glaucoma. Forty eyes had glaucoma. Intraocular pressure was measured before, immediately after, and 5 minutes after injection of local anaesthetic. Mean IOP rose by 5.8 mm Hg at 1 minute (p < 0.01) and 0.7 mm Hg at 5 minutes (p > 0.05). However, in eyes not receiving external ocular compression after the 1 minute measurement (n = 70, 67%), IOP was still 3.6 mm Hg higher than baseline (p < 0.01), compared with 5.2 mm Hg lower than baseline (p < 0.01) where compression was used. Patients with glaucoma experienced higher and more persistent increases in IOP than those without glaucoma. The increase in IOP varied greatly between patients: the maximum rise was 25 mm Hg, and in one glaucoma patient an IOP of 50 mm Hg occurred, persisting for 5 minutes. At 1 minute, 14 of the glaucoma subjects (35%) had experienced an IOP rise of > or = 10 mm Hg, and four (10%) a rise of > or = 20 mm Hg. These results suggest that the changes in IOP in patients with glaucoma, with an acute increase in IOP being succeeded by an acute decrease on entry into the anterior chamber, may be hazardous. The implications for clinical practice are discussed.     

佛司可林两个类似物对饮水导致的人眼压升高的影响

目的实验观察佛司可林两个类似物,即isoforskolin(isoF),deacetylforskolin(deaF),对饮水导致急性人眼压升高的影响.方法按随机双盲法设计,将佛司可林两个类似物配成的滴眼液分别滴人l眼,相应的溶媒滴入另眼.让受试者饮水(14 ml/kg)造成急性人眼压升高.给药前后用气动式眼压计测定眼压值,观察眼压变化.结果表明isoF(0.5%)及deaF(1.0%)均有抑制作用,最大抑制率分别为¨.4%及12.0%,并且副作用小.结论实验证明isoF(0.5%)及deaF(1.0%)抑制饮水导致急性人眼压升高.