Rhythm Of Intraocular Pressure Research Articles

Repeated Measurements Are Necessary for Evaluating Accurate Diurnal Rhythm Using a Self-Intraocular Pressure Measurement Device

To investigate how many tests need to be performed to adequately assess intraocular pressure (IOP) diurnal change using a self-measuring rebound tonometer among glaucoma patients. Adult patients with primary open-angle glaucoma were included. IOP was measured in the morning (6 AM to 9 AM), afternoon (12 PM to 3 PM), and at night (6 PM to 9 PM) for seven consecutive days. Twenty-four (7 males and 17 females, mean age 59.5 ± 11.0 years) patients who successfully measured IOP at least three times per day during the correct time periods for four days were subjected to analysis. The IOP rhythm was significantly greater on the first day of measurement (6.6 ± 3.6 mmHg) than that averaged during subsequent days (4.4 ± 2.2 mmHg). The time of the highest and lowest IOP measurements on the first day of IOP measurement and during the entire measurement period coincided in 72.9% and 64.6% of cases, respectively. The concordance rate of the highest IOP time between the whole measurement period and each measurement day was less than 60%. The diurnal IOP rhythm measured by the patients themselves was not consistent, and multiple days of measurements may be necessary to correctly assess diurnal IOP rhythm.

Suppression of trabecular meshwork phagocytosis by norepinephrine is associated with nocturnal increase in intraocular pressure in mice

Intraocular pressure (IOP) is an important factor in glaucoma development, which involves aqueous humor (AH) dynamics, with inflow from the ciliary body and outflow through the trabecular meshwork (TM). IOP has a circadian rhythm entrained by sympathetic noradrenaline (NE) or adrenal glucocorticoids (GCs). Herein, we investigated the involvement of GC/NE in AH outflow. Pharmacological prevention of inflow/outflow in mice indicated a diurnal outflow increase, which was related to TM phagocytosis. NE showed a non-self-sustained inhibition in phagocytosis of immortalized human TM cells, but not GC. The pharmacological and reverse genetic approaches identified β1-adrenergic receptor (AR)-mediated exchange proteins directly activated by cyclic adenosine monophosphate (EPAC)-SHIP1 signal activation by ablation of phosphatidylinositol triphosphate, regulating phagocytic cup formation. Furthermore, we revealed the phagocytosis involvement in the β1-AR-EPAC-SHIP1-mediated nocturnal IOP rise in mice. These suggest that TM phagocytosis suppression by NE can regulate IOP rhythm through AH outflow. This discovery may aid glaucoma management.

Melatonin, circadian rhythms and glaucoma: current perspective.

Melatonin, circadian rhythms and glaucoma: current perspective.

A comparison of the circadian rhythm of intraocular pressure in patients with primary glaucoma and normal individuals

Purpose The aim of this study was to evaluate the 24-h intraocular pressure (IOP) fluctuations in patients with glaucoma and to compare them with normal persons.Patients and methods This is a cross-sectional comparative study of the circadian rhythm of IOP that was conducted on 30 patients diagnosed with primary glaucoma on medical or surgical treatment and 30 normal individuals with no signs of glaucoma. There were three cases of primary angle closure glaucoma, and so they were excluded from the analysis.Results The mean age of all participants was 60.25±12.15 years. The mean age of the normal individuals was 58.60±12.33 years compared with 62.22±11.66 years in patients with primary open angle glaucoma (POAG), with no statistically significant difference (P=0.486). A higher proportion of females (63%) were found in the glaucoma group, though not statistically significant (P=0.138). The mean IOP was higher among the glaucoma group (19.92±6.18 mmHg) than in the normal individuals (14.83±1.75 mmHg), with a statistically significant difference (P=0.001). The mean diurnal variation of IOP in the right eye among the normal individuals (3.6±1.1 mmHg) was significantly lower than in the POAG group (7.11±4.8 mmHg) (P=0.001). Similarly, in the left eye, the mean diurnal variation was significantly higher in the POAG group (6.07±2.25 mmHg) compared with the normal individuals (3.52±1.25 mmHg) (P=0.00). The average peak of IOP among normal individuals and patients with POAG was 19.75±2.0 and 37.56.9 mmHg, respectively, in the right eye (P=0.01) and 20.00 ± 1.6 mmHg and 26.25 ± 2.2 in normal individuals and patients with POAG, respectively, in the left eye (P=0.001). The peak IOP among the POAG group was seen at 6 p.m. and 6 a.m., mostly outside office hours.Conclusion The diurnal variation of IOP was more among patients with glaucoma than normal individuals. The average peak of the IOP was seen only after office hours (9 a.m.–5 p.m.), thus emphasizing the need for 24-h monitoring of IOP. The 24-h measurement would help recognize the IOP spikes and help decide the time of instillation of antiglaucoma medication to avoid further glaucoma progression.

Relationship between Myopia and Light Exposure

Epidemiological studies found that the incidence of myopia was increasing year by year and the age of onset of myopia was showing a trend of affecting increasingly younger children. Reducing the occurrence of myopia and controlling the increase of myopia diopter have always been the focus of research on the prevention and control of myopia. Large randomized controlled clinical trials have found that outdoor activities can effectively reduce the incidence of myopia and delay the progression of myopia. Basic experiments also revealed that there were certain connections between light exposure and myopia. We herein review the research progress, limitations and future directions of research on light exposure and myopia. From the perspective of light properties, increasing the intensity of light can slow the progression of myopia and reduce the occurrence of experimentally induced myopia. However, the actual mechanism of action is still unclear. The rhythmic changes of light exposure caused by the light/dark cycle may cause abnormalities in the secretion of melatonin and dopamine, and changes in the circadian rhythm of intraocular pressure and choroidal thickness, thus affecting myopia. The red light, with relatively longer wavelength and forming images behind the retina, tends to induce myopia more easily, while the blue light, with medium and short wavelength and forming images before the retina, tends to delay myopia progression. However, different species respond differently to lights of different wavelengths, and the relationship between light wavelength and myopia needs further investigation. Future research can be done to further explore the mechanism of action of how light exposure changes the progression of myopia, including the following aspects: how light changes dopamine levels, causing changes in downstream signal pathways, and thus controlling the growth of the axial length of the eye; how retinal photoreceptor cells receive light signals of different wavelengths in order to adjust the refractive power of the eyes; and how to design artificial lighting of reasonable intensity, composition and properties, and apply the design in myopia prevention and control.

Triggerfish Recording of IOP Patterns in Combined HFDS Minimally Invasive Glaucoma and Cataract Surgery: A Prospective Study.

Background: The aim of the study is to investigate whether the circadian IOP rhythm can be influenced by combined cataract surgery with high frequency deep sclerotomy (HFDS) and whether intraocular pressure (IOP) can be significantly reduced by HFDS. Methods: In our study 10 patients were included, in whom 24 h IOP monitoring was installed before and after HFDS/cataract surgery using a Triggerfish. HFDS is a minimally invasive glaucoma surgery (MIGS). Results: After performed HFDS combined with cataract surgery, the IOP was reduced from 27.7 ± 2.11 mmHg to 14.4 ± 2.59 mmHg, which is highly significant (p < 0.001). The contact lens sensor (CLS) cosinor analysis pre- and postoperatively showed that the circadian rhythm is not influenced by the surgery, i.e., the circadian IOP rhythm did not show significant differences before and after surgery. Conclusions: HFDS combined with cataract surgery is a potent surgical method that can significantly reduce the IOP. However, the circadian rhythm cannot be changed by the surgery. The acrophase remained during the night in all patients.

Disruption of 24-Hour Rhythm in Intraocular Pressure Correlates with Retinal Ganglion Cell Loss in Glaucoma.

Parameters of 24-h rhythm in intraocular pressure (IOP) were assessed in patients with stable or advanced primary open-angle glaucoma (S-POAG/A-POAG) and referenced to the phase of “marker” circadian temperature rhythm of each patient. Body temperature and IOP were measured over a 72-h span in 115 participants (65 S-POAG and 50 A-POAG). Retinal Ganglion Cell (RGC) damage was assessed by high-definition optical coherence tomography. The 24-h IOP rhythm in A-POAG patients peaked during the night, opposite to the daytime phase position in S-POAG patients (p < 0.0001). The 24-h IOP phase correlated with RGC loss (p < 0.0001). The internal phase shift between IOP and body temperature gradually increased with POAG progression (p < 0.001). Angiotensin converting enzyme Alu-repeat deletion/insertion (ACE I/D) emerged as a candidate gene polymorphism, which may play a role in the alteration of the circadian IOP variability in advanced glaucoma. To conclude, a reliable estimation of the 24-h rhythm in IOP requires the degree of RGC damage to be assessed. In advanced POAG, the 24-h phase of IOP tended to occur during the night and correlated with RGC loss, being progressively delayed relative to the phase of temperature.

Effect of inhalation anesthesia with isoflurane on circadian rhythm of murine intraocular pressure

PurposeFor research on circadian intraocular pressure (IOP), rebound tonometers are widely used with or without general anesthesia as a non-invasive approach to obtain IOP values. However, whether general anesthesia such as inhalation anesthesia with isoflurane affects the circadian rhythm of IOP and in turn IOP measurements is currently unclear. As such, data reporting IOP values obtained under general anesthesia should be interpreted with caution. The purpose of this study was to evaluate how general anesthesia with isoflurane inhalation affects the circadian rhythm of IOP. MethodsC57Bl/6J strain mice maintained using a 12h:12h light/dark cycle (lights on and off at ZT0 and ZT12, respectively) were used. IOPs were measured using a rebound tonometer (Icare TonoLab) before and 3, 5, 10, 15, and 30 min after initiating anesthesia in both light and dark phases (ZT 2–6 and ZT 14–18, respectively). Awake IOPs and IOPs at 3 and 5 min after anesthesia initiation were also obtained at ZT5, 8, 11, 14, 17, and 20 to assess IOP diurnal curves under gas anesthesia. ResultsIOP values gradually decreased after anesthesia initiation in both light and dark phases (P < 0.001) and there was no interaction between light/dark phase and anesthesia time (P = 0.88). There was a slight, but not significant, reduction in IOP 3 min after initiating anesthesia (P = 0.23), and significant decreases in IOP occurred at subsequent timepoints (P ≤ 0.001). Both awake and anesthetized mice showed a robust IOP rhythm that reached a peak and trough in the dark and light phase, respectively. Awake IOP levels did not significantly differ from those for anesthetized mice at 3 min after anesthesia initiation at all time points (P ≥ 0.07). ConclusionsBoth awake and anesthetized mice demonstrated a robust circadian rhythm for IOP. Murine IOP showed similar gradual decreases under inhalation anesthesia with isoflurane in both the light and dark phases. IOPs measured using a rebound tonometer within 3 min of initiating isoflurane anesthesia were comparable to awake IOPs, and thus may be useful to monitor the circadian rhythm of IOP in mice.

Circadian rhythm of intraocular pressure in clinically normal donkeys (Equus asinus)

ABSTRACT The present study aimed to report the circadian rhythm of intraocular pressure (IOP) in clinically normal donkeys. A prospective study was conducted on 30 adult donkeys. Measurement of the IOP was made at 2-hr interval starting at 6:00 hr till the next day at 4:00 using applanation tonometry. Measurements were recorded for both eyes and compared for male and female differences. The overall mean (± SEM) IOP measurement was 24.99 ± 0.14 mmHg. The mean (± SEM) IOP of the right and left eyes was 25.59 ± 0.19 and 24.27 ± 0.19 mmHg, respectively. The IOP values of the right and left eyes as well as of male and female values did not change significantly (P > 0.05) at all times. IOP measurements demonstrated diurnal fluctuation during the light phase of the day. The IOP significantly (P < 0.001) increased (27.07 ± 0.42) in the early morning (peak daytime at 8:00 hr) and was significantly (P < 0.001) lower (20.68 ± 0.34) at the mid-light phase (12:00 hr) compared to all evaluation times. The study documented the daily rhythm of IOP in donkeys. The 24-hr variation of IOP measurement should be considered when evaluating IOP in donkeys.

Analysis of the circadian rhythm of intraocular pressure in stable and progressive forms of primary open-angle glaucoma

Purpose. To analyze the daily dynamics and the parameters of intraocular pressure circadian rhythm (IOP CR) in patients with primary open-angle glaucoma (POAG) (stable and progressive forms) and determine chronobiological regularities of glaucoma progression depending on the patterns of restructuring the daily dynamics of IOP CR and body temperature.Material and methods. The study included 75 POAG patients, of which 35 had a stable form (S-POAG) and 40 had a rapidly progressing form (P-POAG). The control group was composed of 80 subjects without POAG. The index of retinal ganglion cell loss measured by optical coherence tomography (OCT) was used as a criterion of POAG progression. IOP was measured by the patients themselves for 72 hours at 7 time points (3 am, 8 am, 11 am, 2 pm, 5 pm, 8 pm, and 11 pm, who used an Icare ONE portable intraocular pressure tonometer for individual use.Results. IOP daily dynamics was distributed differently in the different groups. In S-POAG, the peak values were mainly reached in the morning hours, while the minimum values were observed at night. In P-POAG, the peak values of IOP were contrariwise recorded at night. In both POAG groups, an increase of irregular fluctuation share was noted, which indicated a decrease of the CR contribution to the IOP CR. Moreover, in POAG, a change in the phase ratio between the IOP CR and CR of body temperature was observed. For IOP CR phase violation manifestations, the threshold value of GCS global loss index was determined at 10–15 % according to OCT data.Conclusion. IOP daily dynamics were shown to differ in S-POAG and P-POAG patients. In both groups. Signs of desynchronization were detected. The ganglion retinal cell global loss index can be used to determine phase disturbances of IOP CR.

Modeling a new dynamic approach to measure intraocular pressure with solitary waves

Glaucoma is an age-related disease and the second cause of blindness in the world. The measurement of intraocular pressure (IOP) is the cornerstone of glaucoma treatment because elevated IOP is the only risk factor that can be modified. Clinical evidences proved that single measurements obtained during office visits are neither sufficient to capture the circadian rhythm of IOP nor valid to demonstrate the effect of medication or patients’ compliance to a given therapy. As such, patients would benefit from a device that they can self-administer to gage the IOP multiple times a day. In this paper, we present a numerical study on a new approach to measure IOP noninvasively using engineering principles never explored in ophthalmology. The method relies on the dynamical interaction between the solitary waves propagating within a chain of particles and the eye to be evaluated that is in contact with the end of the chain. In the study presented in this paper, a numerical model of such interaction was implemented to demonstrate the sensitivity of the proposed approach to the variation of IOP. The findings show that some features of the waves are monotonically dependent on the IOP. These findings may pave the way to the development of a new kind of tonometer that will enable millions of glaucoma patients to perform routine self-measurements of the eye pressure without clinical visits.

Twenty-Four-Hour Contact Lens Sensor Monitoring of Aqueous Humor Dynamics in Surgically or Medically Treated Glaucoma Patients

Aim This study assessed the 24 h circadian rhythm of intraocular pressure (IOP) using a contact lens sensor in three groups of patients with open-angle glaucoma. Methods This study was a monocentric, cross-sectional, nonrandomized, prospective, pilot study. Eighty-nine patients were enrolled: 29 patients previously underwent an Ex-PRESS mini glaucoma device procedure (Group 1), 28 patients previously underwent Hydrus microstent implantation (Group 2), and 32 patients were currently being treated medically for primary open-angle glaucoma (Group 3). Circadian rhythm patterns were considered with five circadian indicators: fluctuation ranges, maximum, minimum, acrophase (time of peak value), and bathyphase (time of trough value). A two-tailed Mann–Whitney U-test was used to evaluate differences between groups. Results All subjects exhibited a circadian rhythm and a nocturnal pattern. The signal fluctuation range was significantly smaller in the surgical groups than in the medically treated group (Group 1 vs. Group 3, p=0.003; Group 2 vs. Group 3, p=0.010). Subjects who underwent the Ex-PRESS procedure (Group 1) exhibited significant differences compared with the drug therapy group (Group 3) with regard to the minimum value (p=0.015), acrophase (p=0.009), and bathyphase (p=0.002). The other circadian indicators were not significantly different among groups. Conclusions Patients who underwent IOP-lowering surgery had an intrinsic nyctohemeral rhythm. Both surgical procedures, Ex-PRESS and Hydrus, were associated with smaller signal fluctuations compared with medical treatment.

Role of light and the circadian clock in the rhythmic oscillation of intraocular pressure: Studies in VPAC2 receptor and PACAP deficient mice

The intraocular pressure of mice displays a daily rhythmicity being highest during the dark period. The present study was performed to elucidate the role of the circadian clock and light in the diurnal and the circadian variations in intraocular pressure in mice, by using animals with disrupted clock function (VPAC2 receptor knockout mice) or impaired light information to the clock (PACAP knockout mice). In wildtype mice, intraocular pressure measured under light/dark conditions showed a statistically significant 24 h sinusoidal rhythm with nadir during the light phase and peak during the dark phase. After transfer of the wildtype mice into constant darkness, the intraocular pressure increased, but the rhythmic changes in intraocular pressure continued with a pattern identical to that obtained during the light/dark cycle. The intraocular pressure in VPAC2 receptor deficient mice during light/dark conditions also showed a sinusoidal pattern with significant changes as a function of a 24 h cycle. However, transfer of the VPAC2 receptor knockout mice into constant darkness completely abolished the rhythmic changes in intraocular pressure. The intraocular pressure in PACAP deficient mice oscillated significantly during both 24 h light and darkness and during constant darkness. During LD conditions, the amplitude of PACAP deficient was significantly lower compared to wildtype mice, resulting in higher daytime and lower nighttime values.In conclusion, by studying the VPAC2 receptor knockout mouse which lacks circadian control and the PACAP knockout mouse which displays impaired light signaling, we provided evidence that the daily intraocular pressure rhythms are primarily generated by the circadian master clock and to a lesser extent by environmental light and darkness.

Light entrainment of the murine intraocular pressure circadian rhythm utilizes non-local mechanisms.

PurposeIntraocular pressure (IOP) is known to have a strong circadian rhythm, yet how light/dark cycles entrain this rhythm is unknown. The purpose of this study was to assess whether, like the retina, the mammalian ciliary body and IOP clocks have an intrinsic ability to entrain to light/dark cycles.MethodsIris-ciliary body complexes were obtained from period2:luciferase (PER2::LUC) mice and cultured to measure bioluminescence rhythmicity. Pairs of the iris-ciliary body complex were exposed to antiphasic 9:15 h light/dark cycle in vitro. After 4 days of exposure to light/dark cycles, bioluminescence was recorded to establish their circadian phases. In addition, pairs of the iris-ciliary body complex co-cultured with the retinas or corneas of wild-type mice were also investigated. The IOP circadian changes of free-running Opn4-/-;rd1/rd1 mice whose behavior was antiphasic to wild-type were measured by a rebound tonometry, and compared with wild-type mice. Opn3, Opn4, and Opn5 mRNA expression in the iris-ciliary body were analyzed using RT-PCR.ResultsThe iris/ciliary body complex expressed Opn3, Opn4, and Opn5 mRNA; however, unlike in retina and cornea, neither the iris-CB complex nor the co-cultured complex was directly entrained by light-dark cycle in vitro. The diurnal IOP change of Opn4-/-;rd1/rd1 mice showed an antiphasic pattern to wild-type mice and their rhythms followed the whole-animal behavioral rhythm.ConclusionsDespite expressing mRNA for several non-visual opsins, circadian rhythms of the iris-ciliary body complex of mice do not entrain directly to light-dark cycles ex vivo. Unlike retina, the iris/ciliary body clocks of blind mice remain synchronized to the organismal behavioral rhythm rather than local light-dark cycles. These results suggest that IOP rhythm entrainment is mediated by a systemic rather than local signal in mice.

24-Hour Intraocular Pressure Rhythm in Patients With Untreated Primary Open Angle Glaucoma and Effects of Selective Laser Trabeculoplasty.

The purpose of the study was to evaluate the 24-hour nyctohemeral rhythm of intraocular pressure (IOP) in patients with untreated primary open angle glaucoma using a contact lens sensor. To evaluate the effect of selective laser trabeculoplasty (SLT) on the 24-hour rhythm of IOP. Prospective study conducted in a chronobiology center. Fourteen patients with primary open angle glaucoma underwent three 24-hour IOP measurement sessions after a complete wash-out of the medical treatment: before SLT and 1 and 6 months after, using the contact lens sensor Triggerfish (SENSIMED, Lausanne, Switzerland). IOP and the main parameters of nyctohemeral rhythm (existence of a rhythm, acrophase, bathyphase, midline estimating statistic of rhythm, amplitude, and range) before SLT were compared with the same parameters measured 1 and 6 months later. IOP increased from 16.3±3.7 to 22.1±8.4 mm Hg (5.8 mm Hg; 95% confidence interval (CI), 2.41-12.71; P=0.009) after the wash-out procedure. After SLT, IOP significantly decreased by 3.4 mm Hg (95% CI, 0.09-7.89; P=0.041) (14.9%) at 1 month and 1.9 mm Hg (95% CI 0.10-3.84; P=0.044) (8.1%) at 6 months. After medication wash-out, 100% of the subjects had a nyctohemeral IOP rhythm with nocturnal acrophase (01:57±3:32 AM, 01:22±3:01 AM, and 03:17±2:12 AM at inclusion, 1 and 6 mo, respectively). SLT did not significantly change the characteristics of the 24-hour IOP pattern, notably the amplitude and the type of rhythm (persistence of nocturnal acrophase). After medical treatment wash-out, patients with open angle glaucoma consistently had a significant 24-hour IOP rhythm with nocturnal acrophase. SLT reduces the absolute IOP value but does not modify the nyctohemeral IOP rhythm.

The Role of Beta-Adrenergic Receptors in the Regulation of Circadian Intraocular Pressure Rhythm in Mice

ABSTRACTPurpose: To investigate whether the elimination of β1- and β2-adrenergic receptors alters the diurnal intraocular pressure (IOP) rhythm in mice.Materials and Methods: β1-/β2-adrenergic receptor double-knockout and C57BL/6J mice were anesthetized intraperitoneally, with their IOPs measured via microneedle method. After entrainment to a 12-h light–dark (LD) cycle (light phase 6:00–18:00), IOPs were measured every 3 h from 9:00 to 24:00 (group 1, β1-/β2-adrenergic receptor double-knockout mice, n = 11; C57BL/6J, n = 15). The IOP measurements at 15:00 and 24:00 under a 12-h LD cycle and in the constant darkness (1 day and 8 days after exposure to darkness, respectively) were performed in another group of β1-/β2-adrenergic receptor double-knockout mice (group 2, n = 12). IOP variance throughout the day and mean IOP differences among time points were evaluated using a linear mixed model.Results: β1-/β2-adrenergic receptor double-knockout and C57BL/6J mice showed biphasic IOP curves, low during the light phase and high during the dark phase; the fluctuation was significant (P < 0.001). The peak IOP (18.7 ± 1.4 mmHg) occurred at 24:00 and the trough IOP (13.5 ± 1.5 mmHg) occurred at 15:00 in β1-/β2-adrenergic receptor double-knockout mice group. IOP curves of β1-/β2-adrenergic receptor double-knockout and C57BL/6J were nearly parallel, and the IOPs of β1-/β2-adrenergic receptor double-knockout mice were significantly higher than those of C57BL/6J mice (P < 0.001). Under constant dark (DD) conditions, IOP at 24:00 (18.1 ± 1.5 mmHg) was significantly higher than that at 15:00 (13.3 ± 1.2 mmHg) (P < 0.001). The transition from the LD cycle to DD environment produced no significant change in IOP (P = 0.728).Conclusions: Elimination of both β1- and β2-adrenergic receptors did not disturb the biphasic diurnal IOP rhythm in mice.

Circadian Patterns of Intraocular Pressure Fluctuation among Normal-Tension Glaucoma Optic Disc Phenotypes.

ObjectiveTo characterize the 24-h habitual-position intraocular pressure (IOP) patterns of optic disc phenotypes (ODPs) in untreated normal-tension glaucoma (NTG) and the relationships between nocturnal IOP elevation and various clinical factors.DesignProspective, cross-sectional, observational study.MethodsEighty-two NTG patients with focal ischemic (FI) ODP and 82 age- and disease severity-matched NTG patients with myopic glaucomatous (MG) ODP were recruited prospectively over 3 years. The IOP was recorded 11 times over a 24-hour (h) period by a single ophthalmologist using a hand-held tonometer (TonoPen®XL). A cosinor model was used to describe the 24-h IOP rhythm. Associations between nocturnal IOP elevation and both ocular and demographic variables were evaluated using the generalized estimating equation (GEE).ResultsMean habitual-position IOP was significantly higher during nighttime than daytime in the FI group (16.44 vs. 14.23 mmHg, P < 0.001), but not in the MG group (15.91 vs. 15.70 mmHg, P = 0.82). The FI group also exhibited a significantly higher peak IOP during sleeping hours (P = 0.01) and lower trough IOP during the 24-h period than the MG group (P < 0.01). The MG group showed a significantly higher peak IOP during waking hours than the FI group (P < 0.01). Therefore, 24-h IOP fluctuation range was significantly higher in the FI group than the MG group (P = 0.013). In the FI group, peak habitual-position IOP and the highest frequency of IOP peaks occurred during sleeping hours (12 AM–6 AM). By contrast, IOP peaks in the MG group occurred during morning hours (8 AM–12 PM). The FI group showed an overall nocturnal acrophase in habitual-position IOP, with 45 patients (54.9%) having a nocturnal acrophase; 10 (12.2%), a diurnal acrophase; and 27 (32.9%), no evident acrophase. By contrast, the MG group showed no evident peak in habitual-position IOP, with 9 patients (10.9%) having a nocturnal acrophase; 43 (52.4%), a diurnal acrophase; and 30 (36.6%), no evident acrophase. In multivariate modeling using the GEE, ODP (P < 0.001) and spherical equivalent (SE, P = 0.001) were independently associated with nocturnal IOP elevation.ConclusionsBased on 24-h habitual-position IOP data, FI is associated with significant nocturnal IOP elevation, while no such nocturnal IOP elevation is observed in MG ODP. In untreated NTG, there are also significant differences in the 24-h IOP pattern between FI and MG ODPs.

Seasonal changes of 24-hour intraocular pressure rhythm in healthy Shanghai population.

The aim of the present study was to investigate and compare the 24-hour intraocular pressure (IOP) rhythms in winter and summer in the healthy population of Shanghai, China.This is a cross-sectional study in which 24-hour IOP measurements were taken for all eligible healthy volunteers in winter and summer, respectively, and the temperature, hours of sunlight (sunlight time), and circulatory parameters, including heart rate, systolic blood pressure, and diastolic blood pressure, were also recorded. The 24-hour IOP curves and IOP parameters (mean, peak, trough, and fluctuation of IOP together with the diurnal-to-nocturnal IOP change) in winter and summer were obtained and compared. The magnitude of IOP changes from summer to winter was also calculated.A total of 29 participants (58 eyes), 14 (48.28%) male and 15 (51.72%) female, aged 43.66 ± 12.20 (19–61) years, were considered eligible for this study. Generally, IOP decreased progressively before noon, increased notably in the nocturnal period, and peaked at 12:00 am in winter and at 2:00 am in summer. The pattern of 24-hour IOP in winter and summer was significantly different (P = 0.002). The average IOPs from 4:00 pm to 8:00 am, except for 6:00 am, were significantly higher in winter (P < 0.05). However, no significant differences were shown after adjusting for temperature and/or sunlight time. From summer to winter, the extent of IOP increase was mostly around 0 to 3 mm Hg, and the IOPs increased more significantly in the nocturnal period than in the diurnal period (P = 0.05).The 24-hour IOP rhythms were different in winter and summer, with higher IOP level in winter. Temperature and sunlight time, which are independent of heart rate and blood pressure, affected the 24-hour IOP rhythms in healthy people in Shanghai, China. Further investigations are expected for the rhythm of some endogenous substance secretion and the inner mechanism of regulation of IOP.

24-h monitoring devices and nyctohemeral rhythms of intraocular pressure.

Intraocular pressure (IOP) is not a fixed value and varies over both the short term and periods lasting several months or years. In particular, IOP is known to vary throughout the 24-h period of a day, defined as a nyctohemeral rhythm in humans. In clinical practice, it is crucial to evaluate the changes in IOP over 24h in several situations, including the diagnosis of ocular hypertension and glaucoma (IOP is often higher at night) and to optimize the therapeutic management of glaucoma. Until recently, all evaluations of 24-h IOP rhythm were performed using repeated IOP measurements, requiring individuals to be awakened for nocturnal measurements. This method may be imperfect, because it is not physiologic and disturbs the sleep architecture, and also because it provides a limited number of time point measurements not sufficient to finely asses IOP changes. These limitations may have biased previous descriptions of physiological IOP rhythm. Recently, extraocular and intraocular devices integrating a pressure sensor for continuous IOP monitoring have been developed and are available for use in humans. The objective of this article is to present the contributions of these new 24-h monitoring devices for the study of the nyctohemeral rhythms. In healthy subjects and untreated glaucoma subjects, a nyctohemeral rhythm is consistently found and frequently characterized by a mean diurnal IOP lower than the mean nocturnal IOP, with a diurnal bathyphase - usually in the middle or at the end of the afternoon - and a nocturnal acrophase, usually in the middle or at the end of the night.

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

PurposeTo compare estimates of 24-hour intraocular pressure (IOP) peak timing and variation obtained using a contact lens sensor (CLS) and using a pneumatonometer.MethodsLaboratory 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.ResultsBilateral 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).ConclusionsThe 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.