Relationship between postural change of the intraocular pressure and visual field loss in primary open-angle glaucoma

PURPOSE: To determine the relationship between the postural changes of the intraocular pressure and the visual field loss in patients with primary open-angle glaucoma. METHODS: Eleven normal subjects and 11 patients with primary open-angle glaucoma were studied. Intraocular pressure was measured in both the sitting and the supine positions. Visual fields were measured with automated perimetry. RESULTS: When patients moved from a sitting to supine position, the intraocular pressure increased by an average of 3.1 +/- 0.4 mm Hg (mean +/- SEM) in normal subjects and 4.0 +/- 0.2 mm Hg in patients with primary open-angle glaucoma. There was a significant difference between the normal subjects and patients with primary open-angle glaucoma (P = 0.049). Intraocular pressure increased by 4.4 +/- 0.3 mm Hg (P = 0.02) in the worse eye for mean deviation and 3.6 +/- 0.3 mm Hg (P = 0.38) in the better eye for mean deviation. There was no significant difference in intraocular pressure in the sitting position between both groups. CONCLUSIONS: The greatest difference in intraocular pressure between the sitting and supine positions was observed in the worse eye of patients with primary open-angle glaucoma. This result suggests that damage to the optic nerve in primary open-angle glaucoma might occur when patients are asleep in the supine position.     

Effects of latanoprost and timolol-XE on hydrodynamics in the normal eye

PURPOSE: To compare the effects of latanoprost and timolol-XE on ocular pressure and perfusion in healthy adults, with respect to episcleral venous pressure. METHODS: A double-masked, placebo-controlled crossover study of weeklong bedtime treatment with one drop of drug, with placebo contralaterally, followed by a 3-week washout and alternate-drug/contralateral-placebo repeat. Intraocular pressure was measured by applanation and by pneumotonometry, providing pulsatile ocular circulatory estimates. Measurements of episcleral venous pressure were obtained (Friberg method). RESULTS: Twenty subjects participated (five men, 15 women; mean age, 39 years (range, 21 to 55 years); mean baseline intraocular pressure, 13.4 mm Hg). A greater decrease in intraocular pressure was seen among these subjects the morning after initiating treatment with latanoprost (-2.0 mm Hg; P <.0001) than with timolol-XE (-0.9 mm Hg; P =.051) (latanoprost versus timolol DeltaP =.008). This ocular hypotensive effect remained significant that evening with latanoprost (-3.2 mm Hg; P <.0001) but not with timolol XE (-1.0 mm Hg; P =.2). By the morning of day 8, mean intraocular pressure remained 3.2 mm Hg below baseline with latanoprost and 2.3 mm Hg below baseline with timolol-XE (P <.0001 for both drugs). Neither drug altered episcleral venous pressure. Among a subgroup of nine subjects with comparable intraocular pressure reductions with the two drugs, latanoprost treatment was associated with a 16.7% increase in mean pulsatile ocular blood flow (P =.04) through the weeklong treatment interval, consistently higher than during timolol-XE treatment of the same subjects. CONCLUSION: Latanoprost caused an overnight decrease in intraocular pressure in normotensive normal eyes, and both drugs significantly reduced intraocular pressure within 1 week. Intraocular pressure remained higher than episcleral venous pressure throughout treatment with both drugs. Latanoprost was associated with enhanced pulsatile ocular perfusion not seen with timolol-XE treatment.     

Intraocular and episcleral venous pressure increase during inverted posture

We measured intraocular and episcleral venous pressure in 11 subjects in both the supine and the head-down vertical position. Gonioscopy was performed in eight subjects. The intraocular pressure changes were correlated with the alterations in episcleral venous pressure using linear regression analysis. We found that for each 0.83 +/- 0.21 mm Hg increase in episcleral venous pressure there was a rise of 1 mm Hg in intraocular pressure (r = .80, P = .003). Upon inversion, blood appeared in Schlemm's canal in half of the eyes studied with gonioscopy, suggesting that it refluxed into the canal from increased episcleral venous pressure. The mechanism of a sustained intraocular pressure rise during gravity inversion appears to be closely related to increased venous pressure in the orbit.     

Pulsatile ocular blood flow in primary open-angle glaucoma and ocular hypertension

PURPOSE: To compare pulsatile ocular blood flow measurements in untreated ocular hypertensive (OHT) subjects and primary open-angle glaucoma (POAG) patients. DESIGN: A prospective observational study in an institutional setting. METHODS: A total of 97 subjects were recruited to the study (50 ocular hypertensives, 24 glaucoma patients, and 23 normal subjects). "High-risk" OHT had intraocular pressure (IOP) > 25 mm Hg; "low-risk" OHT had IOP 相似文献   

Changes in intraocular pressure during prolonged (7-day) head-down tilt bedrest

PURPOSE: To determine the change in intraocular pressure (IOP) due to postural changes in young healthy volunteers. MATERIALS AND METHODS: Intraocular pressure was measured using a calibrated Pulsair noncontact tonometer in both eyes of 25 female volunteers in a sitting position and after 1, 3, and 10 minutes in a supine position. In the second part of the experiment (a 7-day -6 degrees head-down tilt [HDT]), IOP (at 8 am, 12 am and 6 pm) and corneal thickness (12 am) were monitored in 8 female volunteers before, during, and after the HDT period. Blood pressure, hematocrit, plasma volume and osmolality, and plasma catecholamines concentrations were also measured. RESULTS: Intraocular pressure was significantly higher in the supine position (16.1 +/- 3.6 mm Hg) than in the sitting position, with a mean pressure difference of 2.23 +/- 2.9 mm Hg after 1 minute, 0.9 +/- 3 mm Hg after 3 minutes, and 1.9 +/- 3.8 mm Hg after 10 minutes in a supine position (P < 0.001). During the period of HDT, IOP values decreased significantly on the fifth day (13.3 +/- 1.6 mm Hg, P = 0.03) and the seventh day (12.7 +/- 1.7 mm Hg, P = 0.02) when compared with IOP in the supine position (14.26 +/- 2 mm Hg). The corneal thickness increased significantly (P < 0.0001) at day 5 (549.25 +/- 48.7 microm) and day 7 (540.31 +/- 46.9 microm) compared with baseline (532.45 +/- 38.6 microm). Two days after the end of the HDT bedrest, the mean supine IOP significantly increased (14.1 +/- 1.8 mm Hg, P = 0.003) and corneal thickness was similar to that found at baseline. The mean decrease of IOP was positively correlated with that of the plasma volume (-10%, r = 0.61, P = 0.02) and negatively correlated with the mean rise of hematocrit (r = -0.5, P = 0.07), variables that are considered to be indirect measures of plasma dehydration. CONCLUSIONS: During a 7-day HDT bedrest experiment in healthy women, eyes seemed to compensate the moderate rise of IOP described between a sitting and a supine position, and exhibited a slight and progressive average decrease of 1.3 mm Hg. These physiological modifications could be related to an ocular dehydration or to systemic cardiovascular and hormonal variations during bedrest.     

Postural change of intraocular and blood pressures in ocular hypertension and low tension glaucoma.

The effect of body position on the intraocular and blood pressures of normal volunteers and of patients with ocular hypertension and low tension glaucoma was studied. Changing from the sitting to the supine position increased the intraocular pressure by an average of 4.4 (SD 2.0) mm Hg in the control group, 4.0 (SD 2.0) mm Hg in the ocular hypertension group, and 4.1 (SD 1.8 mm Hg) in the low-tension glaucoma group. After 30 minutes in the supine position the intraocular pressure in normal volunteers and patients with low tension glaucoma remained stable. In contrast patients with ocular hypertension showed a further significant increase in intraocular pressure of 1.6 (SD 2.8) mm Hg (p = 0.004). This was accompanied by an equally significant decrease in blood pressure (p less than 0.001). We believe that these are manifestations of different mechanism of intraocular pressure regulation between these groups.     

Correlation between office and peak nocturnal intraocular pressures in healthy subjects and glaucoma patients

PURPOSE: To evaluate the correlations between office-hour intraocular pressures (IOP) and peak nocturnal IOP in healthy and glaucomatous eyes. DESIGN: Retrospective review of laboratory records. METHODS: We reviewed 24-hour data of IOP collected from 33 younger healthy subjects (aged 18 to 25 years), 35 older healthy subjects (aged 40 to 74 years), and 35 untreated older glaucoma patients (aged 40 to 79 years) housed in a sleep laboratory. Measurements of IOP were taken every 2 hours using a pneumatonometer in the sitting and supine positions during the diurnal/wake period (7 AM to 11 PM) and in the supine position during the nocturnal/sleep period. Correlations between average sitting or supine IOP in the right eye between 9:30 AM and 3:30 PM (office hours) and peak right eye IOP during the nocturnal hours were analyzed. RESULTS: The average values of supine IOP during office hours were found to have the strongest correlation with peak nocturnal IOP in older glaucoma subjects (r = .713, P < .001), whereas the correlation was less in older healthy subjects (r = .523, P < .01) and was absent in younger healthy subjects (r = .224, P = .21). The correlation between average sitting IOP values during office hours and peak nocturnal IOP was also strong in older glaucoma subjects (r = .601, P < .001) and moderate in older healthy subjects (r = .412, P < .05), but absent in younger healthy subjects (r = -.077, P = .672). CONCLUSION: Using a modification of the diurnal IOP curve, the magnitude of peak nocturnal IOP in untreated glaucoma patients can be estimated during routine office visits. Supine IOP measurements estimate peak nocturnal IOP better than sitting measurements. This estimation may provide the clinician with valuable information regarding the nocturnal IOP peak in glaucoma patients.     

Intraocular pressure, ocular pulse pressure, and body position

Intraocular pressures (IOP's) were measured using the Digilab Pneuma-tonometer with the subject in both the sitting and supine positions. The IOP with the Pneuma-tonometer was greater (17.03 mm Hg) in the supine position than in the sitting position (12.90 mm Hg). The IOP measured with the Pneuma-tonometer, with the subject sitting, was similar to the IOP measured with the Goldmann applanation tonometer (13.42 mm Hg). Inasmuch as IOP tends to be lower with the patient in a sitting position, the clinician should be alert to the possibility that some patients with borderline Goldmann IOP's may have pressures well above the normal range when they are lying down. Due to the continuous recording provided by the Pneuma-tonometer, the ocular pulse pressure can be measured. We found a mean ocular pulse pressure amplitude of 1.77 mm Hg. All values are shown plus or minus 1 SD. Comparison of the ocular pulse pressure amplitude for the two eyes could aid in detecting patients with suspected carotid artery stenosis.     

Der intraoculare Druck nach Änderung der Körperlage

Zusammenfassung Es wurde die Abhängigkeit des Augendruckes von der Körperlage (im Sitzen und Liegen) mit Applanations-Tonometern vom Goldmann-Typ untersucht. Die statistische Analyse hat ergeben, daß der Augendruck nach der ersten Messung sinkt, und daß man aus diesem Grund höhere Werte in der ersten Position mißt, gleichgültig, ob zuerst im Liegen oder Sitzen gemessen wird. Werden die Werte des Ruhedruckes, d.h. des Augendruckes bei stabilem Niveau 12 min nach Einnahme bzw. Wechsel der Körperlage analysiert, so findet man einen wenig erhöhten mittleren Augendruck in sitzender Haltung der Patienten. Dieser Unterschied ist nicht gesichert. Es gibt nun Patienten, die in einer Körperhaltung, z.B. im Liegen, immer höhere Werte als im Sitzen haben, andere haben im Liegen immer niedrigere Augendruckwerte als im Sitzen. Diese Tatsache, auf die bereits Strobl und Follmann hingewiesen haben, konnten wir durch Kontrollmessungen bei 19 Patienten mit Unterschieden in beiden Richtungen zwischen 2 und 4 mm Hg bestätigen. Die Verwendung eines statistischen Mittelwertes einer Population zur Berücksichtigung des Lagewechsels im Einzelfall scheint uns deshalb nicht erlaubt.

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Intraocular pressure after changing the patient's position

Summary The influence of the patient's position (sitting or supine) on the intraocular pressure has been examined by means of Goldmann applanation-tonometry. The statistical analysis shows that the intraocular pressure decreases after the first measurement. This is the reason for measuring higher values in the first position, irrespective wether the first measurement is done in sitting or supine position. Analysing the values of steady state pressure i.e. 12 min after taking or changing position indicates a little higher mean value of intraocular pressure in the sitting position of the patient. The difference of mean valuse of sitting and supine position of the patient is not significant. There are patients who have always higher others have always lower values of intraocular pressure in the supine position. These observations described earlier by Strobl and Follmann, have been confirmed by repeated measurements on 19 patients with differences in both directions of 2 to 4 mm Hg. For this reason it seems not feasible to use a statistical mean value of a population to correct the intraocular pressure of a particular case after changing position.

     

Intraocular pressure asymmetry and undiagnosed open-angle glaucoma in an older population

PURPOSE: To quantify prevalence of asymmetric intraocular pressure (IOP) and assess associations with undiagnosed open-angle glaucoma. DESIGN: Population-based cross-sectional study. METHODS: Participants underwent applanation tonometry. Intraocular pressure asymmetry was defined for differences > or = 3 mm Hg; open-angle glaucoma was diagnosed if glaucomatous optic disk and field changes were congruous. Analyses excluded subjects using glaucoma medication, known glaucoma, pseudoexfoliation, and cataract surgery. RESULTS: Intraocular pressure asymmetry was present in 5.1% of subjects and was greater for patients older than 70 years (6.2%). Of subjects with maximum IOP > 21 mm Hg, IOP asymmetry was present in 41.1%. Undiagnosed open-angle glaucoma was more frequent among subjects with (4.8%) than without (1.2%) IOP asymmetry. This relationship remained significant for maximum IOP < or = 21 mm Hg. CONCLUSIONS: Intraocular pressure asymmetry may be a useful sign of undiagnosed glaucoma in subjects without elevated IOP.     

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.     

Nonpenetrating filtering surgery and goniopuncture (staged trabeculectomy) for episcleral venous pressure glaucoma

PURPOSE: To report long-term (>5 years) success of non-penetrating filtering surgery in glaucoma due to elevated episcleral venous pressure. DESIGN: Observational case report. METHODS: A 25-year-old woman developed severe glaucoma due to elevated episcleral venous pressure. Nonpenetrating filtering surgery (opening of the Schlemm canal and resection of corneal stroma overlying the trabecular meshwork and Descemet membrane) was performed with mitomycin. Three months later, the meshwork was perforated ab interno by neodymium:yttrium-aluminum-garnet laser via goniolens (goniopuncture). RESULTS: There were no complications, and no glaucoma medications were used postoperatively. Intraocular pressure ranged from 10 mm Hg to 18 mm Hg during the first 4 months and thereafter between 6 mm Hg and 12 mm Hg. CONCLUSIONS: Glaucoma due to elevated episcleral venous pressure, an entity associated with significant trabeculectomy risks, can be safely and successfully treated with non-penetrating filtering surgery followed by goniopuncture (staged trabeculectomy).     

Nocturnal elevation of intraocular pressure is detectable in the sitting position

PURPOSE. When intraocular pressure (IOP) was monitored in supine healthy young adults throughout a 24-hour period, a diurnal-to-nocturnal elevation of IOP was observed. This study was undertaken to investigate whether a similar elevation of IOP can be detected when experimental subjects are in the sitting position. METHODS. Experimental subjects were 16 nonsmoking, healthy young volunteers (ages, 18-25 years). Subjects with myopia of more than 3 D were excluded. They were housed in a sleep laboratory for 24 hours in a strictly controlled environment. An 8-hour nocturnal/sleep period was assigned to each volunteer according to the individual's accustomed sleep cycle. IOP was measured every 2 hours with a pneumatonometer with the volunteers in both sitting and supine positions. Mean diurnal-to-nocturnal IOP change and the cosine-fit 24-hour IOP rhythm were compared between the sitting and the supine IOP data. RESULTS. Mean IOP was significantly higher in the nocturnal period than in the diurnal/wake period for both the sitting and the supine IOPs. The 24-hour IOP troughs appeared at the end of the diurnal period, and the peaks appeared at the end of the nocturnal period. The difference between the trough and the peak was 3.8 +/- 0.6 mm Hg (mean +/- SEM) in the sitting position and 3.4 +/- 0.6 mm Hg in the supine position. Cosine-fitting of 24-hour IOP data showed a synchronized 24-hour rhythm of the sitting and the supine IOPs for the group. There was no difference in the phase timing or the magnitude of variation between these two 24-hour rhythms of sitting and supine IOPs. CONCLUSIONS. A nocturnal elevation of IOP can be detected in healthy young adults in both the sitting and the supine positions. There is a 24-hour rhythm of sitting IOP that is not different from the 24-hour rhythm of supine IOP.     

Circadian variation of aqueous dynamics in young healthy adults

PURPOSE: Recent research indicates that intraocular pressure (IOP) does not decrease significantly during the nocturnal period, although aqueous humor flow decreases by 50% or more at night. This study was undertaken to investigate whether changes in outflow facility, episcleral venous pressure, or uveoscleral flow at night could account for the nocturnal IOP. METHODS: Sixty-eight eyes of 34 healthy subjects (age, 18-44 years; mean, 29) were studied. Aqueous humor flow rate, IOP, and outflow facility were measured with pneumatonometry, anterior chamber fluorophotometry, and Schiotz tonography respectively, in each eye during the mid-diurnal (2-4 PM) and mid-nocturnal (2-4 AM) periods. Nocturnal IOP, flow rate, and outflow facility were compared to the same variables during the diurnal period. Mathematical models based on the modified Goldmann equation were used to assess the conditions under which these results could be reconciled. RESULTS: Supine IOP decreased slightly from 18.9 +/- 2.7 mm Hg in the mid-diurnal period to 17.8 +/- 2.5 mm Hg in the mid-nocturnal period (mean +/- SD, P = 0.001). Aqueous flow rate decreased from 2.26 +/- 0.73 to 1.12 +/- 0.75 microL/min (mean +/- SD, P < 0.001). There was a nonsignificant trend toward a nocturnal decrease of outflow facility (diurnal, 0.27 +/- 0.11 microL/min/mm Hg; nocturnal, 0.25 +/- 0.08 microL/min/mm Hg; mean +/- SD, P = 0.13). CONCLUSIONS: Outflow facility measured by tonography does not decrease enough during the nocturnal period to compensate for the decreased aqueous humor flow rate. Modeling results indicate that the experimental results could be reconciled only if nocturnal changes in episcleral venous pressure and/or uveoscleral flow occurred.     

Aqueous humor dynamics in the aging human eye

PURPOSE: Healthy subjects were recruited to identify normal, age-associated changes in intraocular pressure and aqueous humor dynamics. METHODS: Normal healthy subjects from two age groups were enrolled in the study: (1) those from 20 to 30 years of age (n = 51) and (2) those 60 years of age and older (n = 53). Intraocular pressure was measured by pneumatonometry, tonographic outflow facility by pneumatonography, and episcleral venous pressure by venomanometry. Aqueous flow and outflow facility were determined by a fluorophotometric technique. Uveoscleral outflow and anterior chamber volume were calculated. Results from the older group were compared with those from the younger group by means of unpaired, two-tailed t tests. RESULTS: Compared with the younger group, the older group showed significant differences as follows: smaller anterior chamber volume (160+/-39 vs. 247+/-39 microl; mean +/- SD; P< .00001), reduced aqueous flow (2.4+/-0.6 vs. 2.8+/-0.8 microl/minute; P = .002), and reduced uveoscleral outflow (1.10+/-0.81 vs. 1.52+/-0.81 microl/minute; P = .009). CONCLUSIONS: In the healthy aging eye, there is a reduction in the production of aqueous humor and a reduction in its drainage through the uveoscleral outflow pathway.     

Laboratory assessment of diurnal and nocturnal ocular perfusion pressures in humans.

We estimated diurnal and nocturnal levels of ocular perfusion pressure at rest in both young and older adults in a clinical sleep laboratory. Measurements of blood pressure and intraocular pressure (IOP) were obtained every 2 hours for 24 consecutive hours in 16 healthy young adults (ages 18-25 years) and 16 older adults (ages 47-74 years). In the 16-hour diurnal wake period, blood pressure and IOP were measured after a 5-minute sitting rest. In the 8-hour nocturnal period, measurements were taken with subjects in the supine position. Sitting and supine ocular perfusion pressures in the diurnal and nocturnal periods were calculated respectively based upon the blood pressure and IOP. Ocular perfusion pressure was found to be higher in the older group than in the younger group throughout the 24 hours. The peak of ocular perfusion pressure was in the nocturnal period for both groups. Within each subject group, the average nocturnal ocular perfusion pressure in the supine position was higher than the average diurnal ocular perfusion pressure in the sitting position. The diurnal-to-nocturnal increase of ocular perfusion pressure was larger in the older group than in the younger group.     

Twenty-four-hour pattern of intraocular pressure in the aging population.

PURPOSE: To characterize the 24-hour pattern of intraocular pressure (IOP) in a sample of the aging human population. METHODS: Twenty-one healthy volunteers 50 to 69 years of age were housed in a sleep laboratory for 24 hours. Experimental conditions were strictly controlled with a 16-hour light period and an 8-hour dark period. Sleep was encouraged in the dark period. Intraocular pressure was measured using a pneumatonometer every 2 hours (total of 12 times). Measurements were taken in both the sitting position and the supine position during the light/wake period but only in the supine position during the dark period. RESULTS: When the sitting IOP data from the light/wake period and the supine IOP data from the dark period were considered, elevation and reduction of IOP occurred around the scheduled lights-off and lights-on transitions, respectively. Mean IOP in the dark period was significantly higher than mean IOP in the light/wake period. The trough appeared at the end of the light/wake period, and the peak appeared at the beginning of the dark period. The magnitude of trough-peak difference was 8.6+/-0.8 mm Hg (mean +/- SEM). Cosine fits of 24-hour IOP data showed a significant 24-hour rhythm. When IOP data from just the supine position were analyzed, the trough-peak IOP difference was 3.4+/-0.7 mm Hg, with similar clock times for the trough and the peak. Cosine fits of supine IOP data showed no statistically significant 24 hour rhythm. CONCLUSIONS: Nocturnal elevation of IOP occurred in this sample of the aging population. The trough of IOP appeared at the end of the light/wake period, and the peak appeared at the beginning of the dark period. The main factor in the nocturnal IOP elevation appeared to be the shift from daytime upright posture to supine posture at night.     

Decrease of intraocular pressure after fat-removal orbital decompression in Graves disease

PURPOSE: To address the efficacy of fat-removal orbital decompression to reduce intraocular pressure in patients with Graves disease. METHODS: This cohort study included 64 eyes of 39 patients with Graves disease. Thirteen men and 36 women, with a mean age of 52.5 years (range, 27 to 80 years), underwent fat-removal orbital decompression. Intraocular pressure (applanation) and proptosis (Hertel exophthalmometry) were prospectively investigated before surgery and 1 week and 6 months after surgery. RESULTS: The volume of resected fat was 6.4+/- 4.5 (3 to 12) ml. The intraocular pressure in primary position decreased from 19.3+/- 4.4 mm Hg to 17.0+/- 2.9 mm Hg at 1 week (p<0.001) and 15.9+/- 3.7 mm Hg at 6 months (p<0.001). Mean proptosis dropped from 24.3+/- 2.5 mm before surgery to 19.9+/-3.0 mm at 1 week (p<0.01), and 19.9+/-3.1 mm at 6 months (p<0.01). Intraocular pressure decrease neither correlated to the volume of resected fat nor to proptosis reduction. CONCLUSIONS: Fat removal reduces intraocular pressure in patients with Graves disease, with no correlation to the volume of resected fat.     

Effect of oxygen on aqueous humor dynamics in rabbits

A study was made in albino rabbits of the effect on aqueous humor dynamics of 100% oxygen, administered by face mask. A mean decrease in intraocular pressure of 4.9 mm Hg was found. This was accompanied by a decrease in episcleral venous pressure of 4.5 mm Hg. Anterior chamber aqueous humor flow decreased transiently after oxygen administration but returned to pre-oxygen levels after about 60 min. It was concluded that the sustained decrease in intraocular pressure which was caused by oxygen was secondary to the decrease in episcleral venous pressure and not to a decrease in the production of aqueous humor.     

Open-angle glaucoma: variations in the intraocular pressure after visual field examination

PURPOSE: To evaluate intraocular pressure (IOP) variations after automated visual field examination in patients with primary open-angle glaucoma and in healthy subjects. PATIENTS AND METHODS: Intraocular pressure was measured in 49 patients (94 eyes) with primary open-angle glaucoma and in 13 healthy subjects (26 eyes) before and immediately after automated visual field examination. All patients had stable IOP and were using local medication to treat glaucoma. The visual field test was performed with a Humphrey 630 VF analyzer and the Central 30-2 full-threshold program. RESULTS: Mean IOP increased significantly in glaucomatous patients immediately after automated visual field examination (P < 0.01), and returned to pretest values after 1 hour (P = 0.2). Mean IOP variation was 2.38 (range, -6-11) mm Hg. In 42 (44.68%) glaucomatous eyes, IOP increased more than 2 mm Hg, with a mean increase of 5.5 mm Hg. Elderly glaucoma patients showed a significantly higher IOP rise than younger patients. No significant IOP variation was detected in healthy subjects. CONCLUSION: Intraocular pressure varied significantly and tended to increase immediately after automated visual field examination in patients with primary open-angle glaucoma. Age seemed to contribute to these IOP changes, but other factors could be involved.