Relative Stability of Regional Facial and Ocular Temperature Measurements in Healthy Individuals.

Purpose: Non-contact measurement of facial temperature using infrared thermography has been used for mass screening of body temperature during a pandemic. We investigated the relative stability of temperature measurement in different facial regions of healthy individuals. Methods: Twenty healthy subjects underwent two experiments. In the first experiment, subjects washed their faces with a 20°C wet towel for 1 minute. Temperature changes compared to baseline in the forehead, cornea, inner canthus, and outer canthus were determined using an infrared camera for 10 minutes. In the second experiment, lubricating eye drops at 20°C were instilled over one eye. Temperature changes in the same regions of interest were monitored for 5 minutes. Results: Baseline temperatures before face washing in the forehead and cornea, inner canthus, and outer canthus of the right eye were 33.4°C ± 0.8°C (mean ± SD), 33.3°C ± 0.8°C, 34.3°C ± 0.7°C, and 32.8°C ± 0.7°C, respectively. Reductions in temperature due to face washing were most significant for the forehead and least significant for the cornea. One minute after face washing, the corresponding changes were -2.8°C ± 0.6°C, -0.3°C ± 0.6°C, -0.6°C ± 0.7°C, and -0.9°C ± 0.7°C for the forehead, cornea, inner canthus, and outer canthus, respectively. After administering the eye drops, no significant temperature changes were observed. Conclusions: When facial temperature was exogenously cooled, the cornea had the most stable temperature readings. Translational Relevance: When using infrared thermography to screen facial temperature, the measurement of corneal temperature is probably a better representative if the stability of temperature readings is critical.

Intraocular pressure and choroidal thickness respond differently to lower body negative pressure during spaceflight.

Spaceflight-associated neuro-ocular syndrome (SANS) develops during long-duration (>1 mo) spaceflight presumably because of chronic exposure to a headward fluid shift that occurs in weightlessness. We aimed to determine whether reversing this headward fluid shift with acute application of lower body negative pressure (LBNP) can influence outcome measures at the eye. Intraocular pressure (IOP) and subfoveal choroidal thickness were therefore evaluated by tonometry and optical coherence tomography (OCT), respectively, in 14 International Space Station crewmembers before flight in the seated, supine, and 15° head-down tilt (HDT) postures and during spaceflight, without and with application of 25 mmHg LBNP. IOP in the preflight seated posture was 14.4 mmHg (95% CI, 13.5-15.2 mmHg), and spaceflight elevated this value by 1.3 mmHg (95% CI, 0.7-1.8 mmHg, P < 0.001). Acute exposure to LBNP during spaceflight reduced IOP to 14.2 mmHg (95% CI, 13.4-15.0 mmHg), which was equivalent to that of the seated posture (P > 0.99), indicating that venous fluid redistribution by LBNP can influence ocular outcome variables during spaceflight. Choroidal thickness during spaceflight (374 µm, 95% CI, 325-423 µm) increased by 35 µm (95% CI, 25-45 µm, P < 0.001), compared with the preflight seated posture (339 µm, 95% CI, 289-388 µm). Acute use of LBNP during spaceflight did not affect choroidal thickness (381 µm, 95% CI, 331-430 µm, P = 0.99). The finding that transmission of reduced venous pressure by LBNP did not decrease choroidal thickness suggests that engorgement of this tissue during spaceflight may reflect changes that are secondary to the chronic cerebral venous congestion associated with spaceflight.NEW & NOTEWORTHY Spaceflight induces a chronic headward fluid shift that is believed to underlie ocular changes observed in astronauts. The present study demonstrates, for the first time, that reversing this headward fluid shift via application of lower body negative pressure (LBNP) during spaceflight may alter the ocular venous system, as evidenced by a decrease in intraocular pressure. This finding indicates that LBNP has the potential to be an effective countermeasure against the headward fluid shift during spaceflight, which may then be beneficial in preventing or reversing associated ocular changes.

The Relationship Between Plasma Tetrahydrocannabinol Levels and Intraocular Pressure in Healthy Adult Subjects.

BACKGROUND: Δ9-tetrahydrocannabinol (THC) has been shown to decreased intraocular pressure (IOP). This project aims to define the relationship between plasma THC levels and IOP in healthy adult subjects. METHODS: Eleven healthy subjects received a single dose of inhaled cannabis that was self-administered in negative pressure rooms. Measurements of IOP and plasma THC levels were taken at baseline and every 30 min for 1 h and afterwards every hour for 4 h. IOP reduction and percent change in IOP over time were calculated. Linear regression models were used to measure the relationship between IOP and plasma THC levels. Two line linear regression models with F-tests were used to detect change points in the regression. Then, Pearson correlations were computed based on the change point. RESULTS: Twenty-two eyes met inclusion criteria. The average peak percentage decrease in IOP was 16% at 60 min. Percent IOP reduction as well as total IOP reduction demonstrated a negative correlation with THC plasma levels showing r-values of -0.81 and -0.70, respectively. F-tests revealed a change point in the regression for plasma levels >20 ng/ml. For levels >20 ng/ml, the correlation coefficients changed significantly with r-values of 0.21 and 0.29 (p < 0.01). CONCLUSION: Plasma THC levels are significantly correlated with IOP reduction up to plasma levels of 20 ng/ml. Plasma levels >20 ng/ml were not correlated with further decrease in IOP. More research is needed to determine the efficacy of THC in reducing IOP for eyes with ocular hypertension and glaucoma.

Correlation Between Office-Hour and Peak Nocturnal Intraocular Pressure in Patients Treated with Prostaglandin Analogs.

PURPOSE: To test the hypothesis that the correlation between office-hour intraocular pressure (IOP) and peak nocturnal IOP is weakened after using a prostaglandin analog. DESIGN: Before-and-after study. METHODS: Twenty-four-hour IOP data obtained in a sleep laboratory of 51 patients (22 patients with open-angle glaucoma and 29 patients with ocular hypertension) were reviewed. Patients had no IOP-lowering medication upon study entry and were then treated with prostaglandin monotherapy for 4 weeks. Measurements of IOP were taken every 2 hours in the sitting and supine positions during the diurnal/wake period (7:30 AM-9:30 PM) and in the supine position during the nocturnal/sleep period (11:30 PM-5:30 AM). Individual and average IOP readings during office hours (9:30 AM-3:30 PM) and peak IOP during the nocturnal/sleep hours were analyzed using the Pearson correlation coefficient and linear regression. RESULTS: There were statistically significant correlations for all the paired variables for the analyses. Average office-hour IOP had a higher correlation with peak nocturnal IOP than individual office-hour IOP. After the treatment with prostaglandin analog, the correlation between average office-hour IOP and nocturnal peak IOP in the sitting position (r = 0.373) and the supine position (r = 0.386) were reduced from the sitting baseline (r = 0.517) and the supine baseline (r = 0.573) in right eyes. Similar change patterns appeared in left eyes. CONCLUSION: There is a correlation between office-hour IOP reading and peak nocturnal IOP under no IOP-lowering treatment as well as under prostaglandin monotherapy. The strength of correlation was weaker under the treatment compared with baseline.

Efficacy of Latanoprostene Bunod 0.024% Compared With Timolol 0.5% in Lowering Intraocular Pressure Over 24 Hours.

PURPOSE: To compare the diurnal and nocturnal effects of latanoprostene bunod 0.024% solution with timolol maleate 0.5% solution on intraocular pressure (IOP) and ocular perfusion pressure. DESIGN: Prospective, open-label randomized crossover trial. METHODS: Twenty-five patients (aged 43-82 years) with ocular hypertension or early primary open-angle glaucoma were enrolled. Baseline IOP and blood pressure were measured in a sleep laboratory every 2 hours in the sitting and supine positions during the 16-hour diurnal/wake period and in the supine position during the 8-hour nocturnal/sleep period. Subjects were randomly assigned to bilateral treatments of latanoprostene bunod at 8 PM or timolol at 8 AM and 8 PM. The second laboratory recording occurred after the 4-week treatment. Subjects were crossed over to the comparator treatment for 4 weeks before the third laboratory recording. Mean IOP and calculated ocular perfusion pressure were compared for the diurnal and nocturnal periods. RESULTS: Twenty-one subjects completed the study. Both treatments reduced diurnal sitting and supine IOP compared to baseline by 2.3-3.9 mm Hg (all P < .001) with no statistically significant difference between the 2 treatments. Nocturnal IOP under latanoprostene bunod treatment was 2.5 ± 3.1 mm Hg (mean ± SD) less than baseline (P = .002) and 2.3 ± 3.0 mm Hg less than timolol treatment (P = .004). Latanoprostene bunod treatment resulted in greater diurnal sitting and supine ocular perfusion pressures compared with baseline (P ≤ .006) and greater nocturnal ocular perfusion pressure compared with timolol treatment (P = .010). CONCLUSIONS: During the nocturnal period, latanoprostene bunod caused more IOP reduction and more increase of ocular perfusion pressure than timolol.

A Population-based Investigation of Circadian Rhythm of Intraocular Pressure in Habitual Position Among Healthy Subjects: The Handan Eye Study.

PURPOSE: (1) To investigate the reference value of peak-trough difference in circadian rhythm of intraocular pressure (IOP) in habitual position and (2) to compare the IOP parameters among 3 age groups. MATERIALS AND METHODS: Habitual IOP of healthy subjects sampled from the population in the Handan Eye Study was measured every 2 hours in the seated position during light-wake period (7:30 AM, 9:30 AM, 11:30 AM, 1:30 PM, 3:30 PM, 5:30 PM, 7:30 PM, 9:30 PM) and in the supine position during dark-sleep period (11:30 PM, 1:30 AM, 3:30 AM, 5:30 AM). Blood pressure and heart rate were obtained subsequently at each IOP measurement. RESULTS: Two hundred six healthy subjects were included in the final analyses (n=20, 30 to 39 y old; n=95, 40 to 49 y old; n=91, 50 to 59 y old). For peak-trough difference (7.2±2.3 mm Hg; 6.8 to 7.5 mm Hg, 95% confidence interval) in habitual position, the reference value was described as median 7.0 mm Hg, 25th percentile 5.5 mm Hg, and 95th percentile 11.5 mm Hg. No significant differences in peak-trough difference, acrophase (cosine-fit analysis derived peak timing) and amplitude (half distance between the cosine-fit maximum and minimum) were found among the 3 age groups. In the cosine model, the nocturnal acrophase (3:49±0.53 AM; 3:42 to 3:55 AM, 95% confidence interval) was detected for the entire group. Furthermore, 106 subjects (52%) had a nocturnal peak pattern, 36 subjects (17%) had a diurnal peak pattern, and 64 subjects (31%) had no evident pattern. CONCLUSIONS: In habitual position, 75% of healthy subjects from a population-based investigation had IOP variation >5.5 mm Hg and 95% subjects had <11.5 mm Hg variation. Aging may not influence the circadian habitual IOP rhythm.

Estimation of 24-Hour Intraocular Pressure Peak Timing and Variation Using a Contact Lens Sensor.

PURPOSE: To compare estimates of 24-hour intraocular pressure (IOP) peak timing and variation obtained using a contact lens sensor (CLS) and using a pneumatonometer. METHODS: Laboratory data collected from 30 healthy volunteers (ages, 20-66 years) in a randomized, controlled clinical trial were analyzed. Participants were housed for 24 hours in a sleep laboratory. One randomly selected right or left eye was fitted with a CLS that monitored circumferential curvature in the corneoscleral region related to the change of IOP. Electronic output signals of 30 seconds were averaged and recorded every 5 minutes. In the contralateral eye, habitual IOP measurements were taken using a pneumatonometer once every two hours. Simulated 24-hour rhythms in both eyes were determined by cosinor fitting. Simulated peak timings (acrophases) and simulated data variations (amplitudes) were compared between the paired eyes. RESULTS: Bilateral change patterns of average 24-hour data for the group were in parallel. The simulated peak timing in the CLS fitted eye occurred at 4:44 AM ± 210 min (mean ± SD) and the IOP peak timing in the contralateral eye at 4:11 AM ± 120 min (P=0.256, Wilcoxon signed-rank test). There was no significant correlation between the simulated data variations in the paired eyes (P=0.820, linear regression). CONCLUSIONS: The 24-hour CLS data showed a simulated peak timing close to the 24-hour IOP peak timing obtained using the pneumatonometer. However, the simulated variations of 24-hour data in the paired eyes were not correlated. Estimated 24-hour IOP rhythms using the two devices should not be considered interchangeable.

Efficacy of a contact lens sensor for monitoring 24-h intraocular pressure related patterns.

PURPOSE: To study performance of a contact lens sensor (CLS) for 24-hour monitoring of IOP-related short-term patterns and compare with IOP obtained by pneumatonometry. METHODS: Prospective clinical trial. Thirty-one healthy volunteers and 2 glaucoma patients were housed for 24 hours in a sleep laboratory. One randomly selected eye was fitted with a CLS (Triggerfish, Sensimed, Switzerland), which measures changes in ocular circumference. In the contralateral eye, IOP measurements were taken using a pneumatonometer every two hours with subjects in the habitual body positions. Heart rate (HR) was measured 3 times during the night for periods of 6 minutes separated by 2 hours. Performance of CLS was defined in two ways: 1) recording the known pattern of IOP increase going from awake (sitting position) to sleep (recumbent), defined as the wake/sleep (W/S) slope and 2) accuracy of the ocular pulse frequency (OPF) concurrent to that of the HR interval. Strength of association between overall CLS and pneumatonometer curves was assessed using coefficients of determination (R2). RESULTS: The W/S slope was statistically significantly positive in both eyes of each subject (CLS, 57.0 ± 40.5 mVeq/h, p<0.001 and 1.6 ± 0.9 mmHg/h, p<0.05 in the contralateral eye). In all, 87 CLS plots concurrent to the HR interval were evaluated. Graders agreed on evaluability for OPF in 83.9% of CLS plots. Accuracy of the CLS to detect the OPF was 86.5%. Coefficient of correlation between CLS and pneumatonometer for the mean 24-h curve was R2 = 0.914. CONCLUSIONS: CLS measurements compare well to the pneumatonometer and may be of practical use for detection of sleep-induced IOP changes. The CLS also is able to detect ocular pulsations with good accuracy in a majority of eyes. TRIAL REGISTRATION: ClinicalTrials.gov NCT01390779.

Intraocular and intracranial pressures during head-down tilt with lower body negative pressure.

BACKGROUND: Seven astronauts after 6-mo missions to the International Space Station showed unexpected vision problems. Lumbar punctures performed in the four astronauts with optic disc edema showed moderate elevations of cerebral spinal fluid pressure after returning to Earth. We hypothesized that lower body negative pressure (LBNP) imposed during head-down tilt (HDT) would reduce intraocular pressure (IOP) and transcranial ultrasound pulse amplitude, a noninvasive intracranial pressure (ICP) surrogate. METHODS: Participating in this study were 25 normal healthy nonsmoking volunteers (mean age: 36 yr). Subjects were positioned supine (5 min), sitting (5 min), 15° whole body HDT (5 min), and 10 min of HDT with LBNP (25 mmHg). The order of HDT and HDT+LBNP tests was balanced. Right and left IOP, transcranial ultrasound pulse amplitude, arm blood pressure, and heart rate were measured during the last minute (steady state) of each testing condition. RESULTS: IOP significantly decreased from supine to sitting posture by 3.2 ± 1.4 mmHg (mean ± SD: N = 25), and increased by 0.9 ± 1.3 mmHg from supine to the HDT position. LBNP during HDT significantly lowered IOP to supine levels. In addition, LBNP significantly reduced transcranial ultrasound pulse amplitudes by 38% as compared to the HDT condition (N = 9). Sitting mean blood pressure (BP) was significantly higher (+5 mmHg) than BP values after 10 min of LBNP during HDT. However, heart rate was not significantly different across all conditions. DISCUSSION: These data suggest that short duration exposures to LBNP attenuate HDT-induced increases in IOP and ICP. Macias BR, Liu JHK, Grande-Gutierrez N, Hargens AR. Intraocular and intracranial pressures during head-down tilt with lower body negative pressure.

Asymmetry of habitual 24-hour intraocular pressure rhythm in glaucoma patients.

PURPOSE: To examine the strength of association between 24-hour rhythms of habitual IOP in the paired eyes of healthy individuals and glaucoma patients. METHODS: Laboratory records of 24-hour habitual IOP from 38 younger healthy individuals, 53 older healthy individuals, and 41 untreated older primary open-angle glaucoma patients were examined. Intraocular pressure was measured every 2 hours sitting during the day and supine at night using a pneumatonometer. Rhythms of 24-hour IOP in the right eye and in the left eye were estimated separately using cosinor rhythmometry. Estimated 24-hour IOP peak timing (acrophase) and estimated 24-hour IOP variation (amplitude) were compared between the paired eyes for each subject group. Strength of association was determined by the absolute time interval between paired 24-hour IOP peak timings and by the coefficient of determination (r(2)) between paired 24-hour IOP variations. RESULTS: Mean absolute time intervals between the paired IOP peak timings were 1 hour and 33 minutes in the younger healthy group and 1 hour and 37 minutes in the older healthy group. In the older glaucoma group, the mean absolute time interval was 2 hours and 30 minutes. Coefficient of determination for the paired 24-hour IOP variations in the older glaucoma group was 0.343, significantly lower than the coefficients of determination in the younger healthy group (0.571) and the older healthy group (0.646). CONCLUSIONS: The strength of association between the paired 24-hour rhythms of habitual IOP is significantly weaker in glaucoma patients than in healthy individuals.

Anterior-posterior transcranial ultrasound to measure cranial oscillations.

BACKGROUND: We aimed to provide information on whether or not the correlation between body tilt and the pulse amplitude of transcranial ultrasonic time-of-flight waveform can be observed in the anterior-posterior skull direction. Also, we asked the question whether or not the skull pulsation can be detected since the cranial bones involved are thicker. METHODS: The experimental model of body tilt that alters intracranial pressure by shifting body fluid headward was employed. Transcranial ultrasound waveforms were examined in 15 healthy volunteers positioned at five tilt angles of +30 degrees, 0 degrees, -30 degrees, -60 degrees, and -90 degrees from the horizontal body position. A pulse-echo transducer was placed on the middle forehead and ultrasound waveforms were recorded. Synchronized variations in the ultrasonic time-of-flight with heartbeats were monitored using the pulsed phase locked loop technique for the output voltage of the ultrasound transducer. Simultaneous effects of body tilt on cardiovascular parameters were also evaluated. RESULTS: Pulse amplitudes of ultrasonic time-of-flight waveforms were found to vary with body tilt. Repeated-measures ANOVA and regression analysis showed a negative correlation between body tilt angle and pulse amplitude. The regression line has the equation: pulse amplitude = (1.158-0.01023 x tilt angle) x 10(-4) voltage. There was no such relationship between head-down body tilt and altered mean blood pressure or heart rate. CONCLUSION: An increase in the pulse amplitude of the anterior-posterior transcranial ultrasonic time-of-flight waveform can be detected when the head-down body tilt angle increases.

Twenty-four-hour pattern of intraocular pressure in untreated patients with ocular hypertension.

PURPOSE: To characterize the 24-hour pattern of intraocular pressure (IOP) in untreated ocular hypertensive (OHTN) patients. METHODS: IOP measurements were taken every 2 hours during a 24-hour period from 15 untreated OHTN patients (ages 41-77 years). Measurements were both sitting and supine (diurnal) and supine only (nocturnal). Mean diurnal and nocturnal IOPs in the OHTN group were compared to previously reported values in age-matched healthy and glaucomatous eyes. Post hoc analysis compared the 24-hour IOP pattern of the OHTN patients who converted to glaucoma and those who did not with that in the same healthy and glaucomatous eyes. RESULTS: Mean sitting and supine IOPs were significantly higher in the OHTN group than in the healthy control but not the glaucoma group. Similar to the glaucoma group, the OHTN group demonstrated significant differences from healthy controls in diurnal IOP variation and IOP changes upon awakening in habitual and supine positions. The 24-hour IOP curve acrophases and amplitudes for OHTNs were closer to those of the glaucoma than the healthy control group in the habitual position. Thirty-three percent of OHTNs developed glaucoma during a mean follow-up period of 4.3 ± 3.8 years. Similar to findings in the glaucoma group, habitual IOP curve phase delay, habitual IOP variation, diurnal-to-nocturnal IOP changes, and IOP changes upon awakening of the converters were significantly different from those in healthy controls. There were no differences between nonconverters and other groups. CONCLUSIONS: Baseline 24-hour IOP pattern in OHTN patients is similar to that in glaucomatous patients. In contrast to nonconverters, OHTN patients who converted to glaucoma are significantly different from healthy controls.

Analysis of continuous 24-hour intraocular pressure patterns in glaucoma.

PURPOSE: To present a method to analyze circadian intraocular pressure (IOP) patterns in glaucoma patients and suspects undergoing repeated continuous 24-hour IOP monitoring. METHODS: Forty patients with established (n = 19) or suspected glaucoma (n = 21) underwent ambulatory 24-hour IOP monitoring on two sessions 1 week apart using a contact lens sensor (CLS). The CLS provides its output in arbitrary units (a.u.). A modified cosinor rhythmometry method was adapted to the CLS output to analyze 24-hour IOP patterns and their reproducibility. Nonparametric tests were used to study differences between sessions 1 and 2 (S1 and S2). Patients pursued their routine daily activities and their sleep was uncontrolled. CLS data were used to assess sleep times. RESULTS: Complete 24-hour data from both sessions were available for 35 patients. Mean (SD) age of the patients was 55.8 ± 15.5 years. The correlation of the cosinor fitting and measured CLS values was r = 0.38 (Spearman r; P < 0.001) for S1, r = 0.50 (P < 0.001) for S2, whereas the correlation between S1 and S2 cosinor fittings was r = 0.76 (P < 0.001). Repeated nocturnal acrophase was seen in 62.9% of patients; 17.1% of patients had no repeatable acrophase. The average amplitude of the 24-hour curve was 143.6 ± 108.1 a.u. (S1) and 130.8 ± 68.2 a.u. (S2) (P = 0.936). CONCLUSIONS: Adapting the cosinor method to CLS data is a useful way for modeling the rhythmic nature of 24-hour IOP patterns and evaluating their reproducibility. Repeatable nocturnal acrophase was seen in 62.9% of patients. (ClinicalTrials.gov number, NCT01319617.).

Twenty-four-hour effects of bimatoprost 0.01% monotherapy on intraocular pressure and ocular perfusion pressure.

OBJECTIVES: To investigate the 24 h effects of bimatoprost 0.01% monotherapy on intraocular pressure (IOP) and ocular perfusion pressure (OPP). DESIGN: Prospective, open-label experimental study. SETTING: Single tertiary ophthalmic clinic. PARTICIPANTS: Sixteen patients with diagnosed primary open-angle glaucoma (POAG) or ocular hypertension (ages, 49-77 years). INTERVENTIONS: Baseline data of 24 h IOP in untreated patients were collected in a sleep laboratory. Measurements of IOP were taken using a pneumatonometer every 2 h in the sitting and supine body positions during the 16 h diurnal/wake period and in the supine position during the 8 h nocturnal/sleep period. After baseline measurements were taken, patients were treated with bimatoprost 0.01% one time per day at bedtime for 4 weeks, and then 24 h IOP data were collected under the same laboratory conditions. PRIMARY AND SECONDARY OUTCOME MEASURES: Diurnal and nocturnal IOP and OPP means under bimatoprost 0.01% treatment were compared with baseline. RESULTS: The diurnal and nocturnal IOP means were significantly lower under the bimatoprost 0.01% treatment than baseline in both the sitting and supine positions. The diurnal and nocturnal OPP means were significantly higher under treatment than baseline in both the sitting and supine positions. CONCLUSION: Bimatoprost 0.01% monotherapy significantly lowered IOP and increased OPP during the 24 h period.

Positional independence of optic nerve head and retinal nerve fiber layer thickness measurements with spectral-domain optical coherence tomography.

PURPOSE: To evaluate repeatability and positional independence of optic nerve head (ONH) and retinal nerve fiber layer (RNFL) thickness measurements in sitting and supine body positions using portable spectral-domain optical coherence tomography (iVue SD-OCT; Optovue Inc). DESIGN: Evaluation of diagnostic technology. METHODS: Sixty eyes of 30 subjects (10 healthy younger adults aged 20-27 years, 10 healthy older adults aged 50-66 years, and 10 glaucoma patients aged 38-82 years) were included prospectively. For each participant, all measurements were taken in a single session. After 5 minutes in the supine position, 5 scans were obtained from both eyes. Following a 5-minute sitting adaptation, 5 scans were then obtained in the sitting position. The same instrument was used for all measurements. Repeatability and correlation between supine and sitting measurements of 4 ONH and 3 RNFL parameters were assessed using intraclass correlation coefficients (ICC), concordance correlation coefficients (ρ), and Bland-Altman plots. RESULTS: Measurements were highly repeatable within individual eyes, both for ONH (ICC range, 73%-99%) and RNFL (ICC range, 72%-99%) parameters. The correlation between supine and sitting ONH measurements was strong and ranged from ρ = 97%-99% (younger healthy) to ρ = 98%-99% (older healthy) and ρ = 84%-99% (glaucoma). Bland-Altman plots indicated good agreement between sitting and supine readings of ONH and RNFL parameters. CONCLUSIONS: Repeatability of measurements of ONH and RNFL is high and measurements between sitting and supine are highly correlated. The ability of the iVue SD-OCT to evaluate ONH and RNFL parameters is good to excellent in both body positions.

Effects of aging on 24-hour intraocular pressure measurements in sitting and supine body positions.

PURPOSE: To evaluate how aging alters 24-hour measurements of intraocular pressure (IOP) in the sitting and supine body positions. METHODS: Fifteen older volunteers with healthy eyes (ages, 53-71 years) were each housed for 1 day in a sleep laboratory. An 8-hour accustomed sleep period was assigned to each subject. Every 2 hours, measurements of IOP were taken in the sitting and supine positions. Sitting and supine patterns of 24-hour IOP were compared. Simulated 24-hour IOP rhythms in the same body position were determined using cosine fitting of individual 24-hour data. The average postural IOP effects during the diurnal/wake period and the nocturnal/sleep period were compared. Data from this group of older subjects were compared with previously collected data from 16 healthy younger subjects (ages, 18-25 years) under the same experimental conditions. RESULTS: Within each age group, sitting and supine patterns of 24-hour IOP were similar and parallel. Compared to the younger subjects, the phase timing (simulated peak) of 24-hour IOP was significantly delayed for the older subjects in both body positions. The postural IOP effect for the older subjects was 4.7 ± 0.8 and 4.8 ± 0.8 mm Hg during the diurnal and nocturnal periods, respectively. These postural IOP effects were not significantly different from the postural effects in the younger subjects. CONCLUSIONS: Although aging can significantly delay the phase timing of the 24-hour IOP pattern toward the diurnal/awake period, it may not affect the postural IOP effect during the diurnal and the nocturnal periods.

Asymmetry of 24-hour intraocular pressure reduction by topical ocular hypotensive medications in fellow eyes.

PURPOSE: A core assumption for the 1-eye therapeutic trial of ocular hypotensive medications is the symmetrical reduction of intraocular pressure (IOP) in paired eyes. This assumption was evaluated for 24-hour IOP reduction in patients who underwent monotherapy or adjunctive therapy. DESIGN: Database study. PARTICIPANTS: Patients 41 to 79 years of age with primary open-angle glaucoma or ocular hypertension. METHODS: Twenty-four-hour IOP data from the paired eyes of patients undergoing bilateral monotherapy (n = 66) of latanoprost, travoprost, timolol, or brimonidine or bilateral adjunctive therapy (n = 52) with brinzolamide or timolol added to latanoprost monotherapy were analyzed retrospectively. Measurements of IOP were obtained every 2 hours in a sleep laboratory before and after at least 4-week drug treatments. Strengths of association for single-pair IOP reductions and average IOP reductions in the paired eyes during the office-hour, diurnal, nocturnal, and 24-hour periods and in different body positions were analyzed. MAIN OUTCOME MEASURES: Variance for the difference, percentage distribution of large absolute difference, and coefficient of determination (r(2)) in the paired IOP reductions. RESULTS: The standard deviations for the differences in single-pair IOP reductions from the means were larger than 2.5 mmHg for all periods and body positions under monotherapy and adjunctive therapy. Absolute differences in single-pair IOP reductions of the cutoff thresholds of 3 and 2 mmHg or more occurred in more than 20% and 36% cases, respectively. Corresponding coefficients of determination were 0.240 to 0.374 with monotherapy and 0.215 to 0.381 with adjunctive therapy. When the average differences in the paired IOP reductions were analyzed for a specific period and posture, the standard deviations for the differences in the paired IOP reductions and the percentage distributions of large absolute differences were reduced, and most coefficients of determination were improved. CONCLUSIONS: There is only a weak association between the right- and left-eye responses to IOP-lowering monotherapy or adjunctive therapy during a 24-hour period when single-pair IOP data are considered. Considering the averages of multiple paired IOP responses can improve the strength of the association. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.