Diurnal Variation Of Intraocular Pressure Research Articles

Characterization of intraocular pressure variability in conscious rats

Elevation of mean intraocular pressure (IOP) has long been recognized as a leading risk factor for glaucoma. Less is known about the possible contribution of moment-to-moment variations in IOP to disease development and progression due to limitations of tonometry, the prevailing method of IOP measurement. Tonometry provides good estimates of mean IOP but not IOP variance. The aim of this study was to quantitatively characterize IOP variability via round-the-clock IOP telemetry in conscious unrestrained rats. The anterior chamber of one eye was implanted with a microcannula connected to a wireless backpack telemetry system, and IOP data were collected every 4 s for one week. The cannula was then repositioned under the conjunctiva, and control data were collected for an additional week. IOP statistics were computed in 30-min intervals over a 24-h period and averaged across days. All animals exhibited a diurnal variation in mean IOP, while deviations about the mean were independent of time of day. Correlation analysis of the deviations revealed transient and sustained components, which were respectively extracted from IOP records using an event detection algorithm. The amplitude and interval distributions of transient and sustained events were characterized, and their energy content was estimated based on outflow tissue resistance of rat eyes. Transient IOP events occurred ∼231 times per day and were typically ≤5 mmHg in amplitude and 2–8 min in duration, while sustained IOP events occurred ∼16 times per day and were typically ≤5 mmHg in amplitude and 20–60 min in duration. Both persisted but were greatly reduced in control recordings, implying minor contamination of IOP data by motion-induced telemetry noise. Sustained events were also often synchronous across implanted animals, indicating that they were driven by autonomic startle and stress responses or other physiological processes activated by sensory signals in the animal housing environment. Not surprisingly, the total daily fluidic energy applied to resistive outflow pathways was determined primarily by basal IOP level. Nevertheless, transient and sustained fluctuations collectively contributed 6% and diurnal fluctuations contributed 9% to daily IOP energy. It is therefore important to consider the cumulative impact of biomechanical stress that IOP fluctuations apply over time to ocular tissues.

Relationship between Diurnal Variation in Intraocular Pressure and Central Corneal Power.

Relationship between intraocular pressure (IOP) change and central corneal curvature is complicated by measurement techniques and corneal biomechanical parameters. Findings from this study indicate that it is worthwhile to observe the association between diurnal change in IOP and corneal power. This study aimed to investigate the relationship between the diurnal change in IOP and central corneal power among eyes with and without myopia. Sixty healthy eyes of 24 emmetropes and 36 myopes were recruited for this cross-sectional study. Both anterior and posterior central corneal powers of the steep (Ks), flat (Kf), mean meridian (Km), best-fit spheres, and central corneal thickness were recorded followed by the IOP (Goldmann-correlated IOP [IOPg] and corneal-compensated IOP) and corneal biomechanics (corneal hysteresis and corneal resistance factor). Measurements were obtained every 3 hours from 9.30 am to 6.30 pm . Linear-mixed model was used to determine the relationship between the change in IOP and the associated change in corneal measurements (adjusted for age, sex, refractive error, central corneal thickness, and biomechanics) among the myopic and nonmyopic eyes. Group mean, amplitude of change, and the diurnal change in IOPg were (mean ± standard deviation) 15.14 ± 2.50, 3.33 ± 1.44, and 1.81 ± 1.25 mmHg, respectively. Overall, an IOP increase was associated with a decrease in the adjusted anterior corneal powers. Myopic eyes were associated with a decrease of 0.04 D (95% confidence interval [CI], 0.07 to 0.01 D; P = .02) in Ks and 0.03 D (95% CI, 0.06 to 0.001 D; P = .047) in Kf per mmHg increase in IOP, whereas for emmetropes, per mmHg increase in IOP only flattened the Kf by 0.03 D (95% CI, 0.06 to 0.004 D; P = .02). Change in anterior corneal power was inversely related to the change in IOPg, with myopic and nonmyopic eyes reporting a significant but differential impact of IOP. Clinicians must keep in mind the impact of large IOP fluctuation on the anterior corneal power.

Diurnal Variation and Effects of Dilation and Sedation on Intraocular Pressure in Infant Rhesus Monkeys

PurposeIntraocular pressure (IOP) is an important factor in numerous ocular conditions and research areas, including eye growth and myopia. In infant monkeys, IOP is typically measured under anesthesia. This study aimed to establish a method for awake IOP measurement in infant rhesus monkeys, determine diurnal variation, and assess the effects of dilation and sedation.MethodsAwake IOP (iCare TonoVet) was measured every 2 h from 7:30 am to 5:30 pm to assess potential diurnal variations in infant rhesus monkeys (age 3 weeks, n = 11). The following day, and every 2 weeks to age 15 weeks, IOP was measured under three conditions: (1) awake, (2) awake and dilated (tropicamide 0.5%), and (3) sedated (ketamine and acepromazine) and dilated. Intraclass correlation coefficient (ICC) was used to determine intersession repeatability, and repeated measures. ANOVA was used to determine effects of age and condition.ResultsAt age 3 weeks, mean (±SEM) awake IOP was 15.4 ± 0.6 and 15.2 ± 0.7 mmHg for right and left eyes, respectively (p=.59). The ICC between sessions was 0.63[−0.5 to 0.9], with a mean difference of 2.2 ± 0.3 mmHg. Diurnal IOP from 7:30 am to 5:30 pm showed no significant variation (p=.65). From 3 to 15 weeks of age, there was a significant effect of age (p=.01) and condition (p<.001). Across ages, IOP was 17.8 ± 0.7 mmHg while awake and undilated, 18.4 ± 0.2 mmHg awake and dilated, and 11.0 ± 0.3 mmHg after sedation and dilation.ConclusionsAwake IOP measurement was feasible in young rhesus monkeys. No significant diurnal variations in IOP were observed between 7:30 am and 5:30 pm at age 3 weeks. In awake monkeys, IOP was slightly higher after mydriasis and considerably lower after sedation. Findings show that IOP under ketamine/acepromazine anesthesia is significantly different than awake IOP in young rhesus monkeys.

The safety and validity of contact lens sensor (Triggerfish) in measuring diurnal variation of intraocular pressure (IOP)

With the current understanding of pathophysiology of glaucoma, the reduction of intraocular pressure (IOP) is the main evidence-based treatment which can prevent the progression of visual field defect (1). Several studies have shown that IOP varies throughout the day and night and patients with different glaucoma subtypes can have different circadian IOP patterns (2-4). In clinical practice, most ophthalmologists rely on the single measurement of IOP in clinic at each patient visit to monitor the control of IOP and thereby monitor the control of glaucoma. The peak IOP during after-hours is frequently underestimated by this form of measurement because it can only provide a single temporal value. Therefore, it is clear that in order to better manage glaucomatous patients, it is necessary to keep track of how their IOP changes over time.

Diurnal Variation of Corneal Hysteresis in Patients With Untreated Primary Open Angle Glaucoma and Normal Individuals.

Corneal hysteresis in both patients with untreated open angle glaucoma and normal individuals demonstrated significant diurnal variation independent of confounding factors and was higher in the nighttime than in the daytime. To investigate diurnal variations in corneal hysteresis (CH) in patients with untreated primary open angle glaucoma (POAG) and normal individuals by using an ocular response analyzer. This prospective study included 72 eyes of 53 patients with untreated POAG and 53 eyes of 47 normal individuals. Intraocular pressure (IOP) and CH were measured using Goldmann applanation tonometry (GAT) and ocular response analyzer, respectively, every 3 hours from 9:00 to 24:00. Mixed-effects models were used to determine factors associated with CH values and CH amplitude (maximum values minus minimum values) and to examine the diurnal variations in GAT IOP and CH in each group. Significant differences between time points were defined as significant variations. The diurnal average GAT IOP and CH in patients with POAG were significantly higher and lower than those in normal individuals ( P =0.001, 0.002). In the multivariate analysis, the larger central corneal thickness was associated with larger CH values in POAG and normal eyes (both P <0.001). A larger amplitude of GAT IOP was significantly associated with a larger CH amplitude in POAG and normal eyes ( P =0.010, 0.013). CH, in both groups, showed similar significant diurnal variation and was higher in the nighttime than in the daytime, even after adjusting for confounding factors, while IOP showed an antiphase pattern. CH in both untreated POAG patients and normal participants demonstrated similar diurnal variations, that is, higher at night, independent of confounding factors. These findings suggest that viscoelastic properties of the cornea may fluctuate diurnally independent of IOP.

Effect of Mindfulness-Based Stress Reduction on Intraocular Pressure in Patients With Ocular Hypertension: A Randomized Control Trial

To evaluate the effect of mindfulness-based stress reduction (MBSR) on intraocular pressure (IOP) in patients with ocular hypertension (OHT). Parallel arm, single masked, randomized controlled trial. Sixty patients with ocular hypertension and IOP > 21 and < 30 mmHg were recruited at a tertiary eye care centre in India. Thirty patients (group 1) underwent six weeks of one hour daily MBSR sessions, while the other 30 patients (group 2) were waitlisted and kept on follow-up. The primary outcome was change in IOP (ΔIOP) after six weeks of MBSR. Secondary outcomes were effect on serum cortisol level, diurnal variation of IOP, vessel perfusion and vessel density on optical coherence tomography angiography (OCTA), and quality of life (QOL). At six weeks, a significant decrease in IOP was noted in group 1 (23.05 ± 1.17 to 19.15 ± 1.45 mmHg; P=.001) compared with group 2 (22.55 ± 0.98 mmHg to 22.37 ± 1.07 mmHg; P=.107). The ΔIOP was significantly greater in group 1 (3.93 ± 1.47) than group 2 (0.17 ± 0.58; P = .001). The diurnal fluctuation of IOP decreased in group 1 (4.87 ± 1.13 mmHg to 2.73 ± 0.98 mmHg; P=.001) as compared with group 2 (4.50 ± 0.86 mmHg to 4.30 ± 0.83 mmHg; P=.227). Significant improvement in vessel perfusion, vessel density, and flux index was noted on OCTA in group 1 compared with group 2. Group 1 showed a significant decrease (P ≤ .001) in serum cortisol level and an improved QOL (P=.001). Mindfulness-based stress reduction was associated with a significant decrease in IOP and serum cortisol, along with an improvement in optic nerve head perfusion and QOL. Mindfulness-based stress reduction can be considered as a potential treatment option in the management of OHT.

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.

A comparison of postural and diurnal variations in intraocular pressure using the iCare rebound tonometer and Perkins applanation tonometer in admitted adults in Kenya

Background: Elevated intraocular pressure (IOP) remained the most important known risk factor for glaucoma.Aim: To compare the postural and diurnal IOP variations using the iCare rebound tonometer (RT) and Perkins applanation tonometer (PAT).Setting: Kakamega County Hospital, Kenya.Methods: Elevated intraocular pressure measurements were taken by two (masked) examiners with two devices in the morning (06:00–09:00), midday (12:00–15:00) and evening (18:00–21:00), in the sitting followed by supine positions in one randomly selected eye of 24 oculo-visual healthy hospital-admitted patients. Effects of the time of the day and position of the body within and between devices were analysed with the Statistical Package for Social Sciences.Results: The mean IOP measured by the RT ranged from 6 mmHg to 24 millimetres of mercury (mmHg) in the sitting position and from 10 mmHg to 26 mmHg in the supine position. The mean IOP measured using PAT ranged from 6 mmHg to 21 mmHg in the sitting position and from 8 mmHg to 24 mmHg in the supine position. The IOP measured by both devices significantly varied with position (p 0.05). Perkins applanation tonometer on average gave a significantly higher IOP (1.7 mmHg [p = 0.003] and 1.3 mmHg [p = 0.034]) at 06:00 compared to that at 12:00 and 18:00, respectively. The IOP readings with the RT were on average 2.2 mmHg and 3.0 mmHg higher at 06:00 compared to that at 12:00 and 18:00, respectively (p 0.0005).Conclusion: Significant reductions were observed in postural and diurnal IOPs in the sitting positions and in the afternoon, respectively. Diurnal IOP variations were slightly higher when measured by RT compared to when measured by PAT.

Effect of Mindfulness Meditation on Intraocular Pressure and Trabecular Meshwork Gene Expression: A Randomized Controlled Trial

To evaluate the effect of mindfulness meditation (MM) on intraocular pressure (IOP) and trabecular meshwork (TM) gene expression in patients with medically uncontrolled primary open angle glaucoma (POAG). Parallel arm, single-masked, randomized controlled trial. Sixty POAG patients with IOP ≥21mm Hg taking maximal topical medication and scheduled for trabeculectomy were included in this study at a tertiary eye care center in India. Thirty patients (Group 1) underwent 3weeks of 45-minute daily MM sessions in addition to medical therapy while Group 2 continued medical therapy only. Primary outcome was change in IOP (ΔIOP) after 3weeks of MM. Secondary outcomes were probability of success, percentage of reduction in IOP, effect on diurnal variations of IOP, changes in quality of life (QoL), and changes in gene expression patterns in TM. At 3weeks, a significant decrease in IOP was seen in Group 1 (20.16 ± 3.3 to 15.05 ± 2.4mm Hg; P= .001), compared to Group 2 (21.2 ± 5.6 to 20.0 ± 5.8mm Hg; P= .38). ΔIOP was significantly higher in Group 1 than in Group 2 (5.0 ± 1.80 vs. 0.20 ± 3.03mm Hg; P= .001). Analysis of gene expression revealed significant upregulation of nitric oxide synthetase (NOS1 and NOS3) and neuroprotective genes with downregulation of proinflammatory genes in Group 1 in comparison to Group 2 (P= .001). MM was associated with significant decrease in IOP and changes in TM gene expression, indicating its direct impact on ocular tissues.

Diurnal variation of intraocular pressure in a tertiary care population

The intraocular pressure has been a subject of considerable speculation since it is the only modifiable risk factor for Primary Open Angle patients.This fluctuation follows a reproducible pattern in most of the eyes. However, there are some eyes which do not follow a consistent pattern of this fluctuation. The need to precisely measure this pattern stems from the fact that a single office based measurement could miss these pressure peaks.Recording the diurnal variation proves to be an effective tool in management of progression of Primary Open Angle Glaucoma as it not only identifies the time of the day when the pressure peaks to enable us to tailor the therapy to appropriately timing the drug administration but it also offers an understanding of range of intraocular pressure fluctuation during the day.

Evaluation of Diurnal Fluctuation in Parafoveal and Peripapillary Vascular Density Using Optical Coherence Tomography Angiography in Patients with Exfoliative Glaucoma and Primary Open-Angle Glaucoma

ABSTRACT Purpose To determine the diurnal variations in parafoveal and peripapillary vessel density using optical coherence tomography angiography in patients with exfoliative glaucoma, patients with primary open-angle glaucoma and healthy individuals. Materials and Methods In this prospective cross-sectional study, 36 exfoliative glaucoma patients, 34 primary open-angle glaucoma patients and 35 healthy individuals were examined. Optical coherence tomography angiography was used for examining the vessel density of peripapillary (radial peripapillary capillary) and parafoveal (superficial layer) regions. Optical coherence tomography angiography readings were obtained at 09:00, 11:00, 14:00 and 16:00 on the same day. Intraocular pressure values were assessed accordingly. The intraclass correlation coefficients were used to evaluate test–retest variability. Results Diurnal variation in intraocular pressure or vessel density values was not found in any parafoveal or peripapillary region in any of the groups at any hour of measurement. The vessel density in the temporal sector of the exfoliative glaucoma group was significantly lower than in the primary open-angle glaucoma group at all time points. (Mann−Whitney U test; 09:00, P= .015; 11:00, P= .002; 14:00, P= .040; and 16:00, P= .048, respectively). The test–retest repeatability was high and almost excellent for the parafoveal and peripapillary regions in each group (XFG range: 0.757 − 0.985, POAG range: 0.834 − 0.985, and control range: 0.708 − 0.983). Conclusions It may be important to estimate the diurnal fluctuation occurring in retinal haemodynamics in patients with exfoliative glaucoma and primary open-angle glaucoma despite the lack of any considerable variation in intraocular pressure and retinal vessel density values in one day. The study found that at any point of time, vessel density of radial peripapillary capillary in temporal region was lower in exfoliative glaucoma patients than in primary open-angle glaucoma patients having the same glaucoma severity.

Diurnal Spikes of Intraocular Pressure in Uveitic Glaucoma: A 24-hour Intraocular Pressure Monitoring Study

ABSTRACT Purpose The aim of this study was to document diurnal changes in intraocular pressure (IOP) in uveitic glaucoma (UG) and compare it with primary open angle glaucoma (POAG) patients. Methods Eight patients with UG and seven patients with POAG were included in this study. The patients were matched for age, gender, and glaucoma medications. None of the patients experienced angle closure, uveitis attack, and ocular surgery, and were not under steroid or immunomodulatory therapy within the last three months. The 24-hour IOP fluctuations were recorded with the help of a contact lens sensor (Sensimed Triggerfish ®, Switzerland). The diurnal IOP fluctuations were modeled with best-fit lines and statistical comparisons between the longitudinal responses of the two groups were determined with nonlinear regression. Results The comparison of mean 24-hour contact lens sensor (CLS) amplitudes revealed a significant difference between the fluctuation levels of UG and POAG groups (213 ± 160 millivolt equivalents (mVeq) vs. 162 ± 168 mVeq, respectively p = .003). The top level of the best-fit curves was significantly higher in the UG group (266 ± 143 mVeq) compared to the POAG group (159 ± 162 mVeq, p < .001). Both curves had their top levels between 5:00 PM and 8:00 AM. The longitudinal regression analysis revealed that the amplitudes of the 24-hour fluctuation waves were significantly different (p = .041). Conclusions This study demonstrated for the first time that the diurnal variation in IOP was significantly higher in UG patients. This difference was also more distinct between 5:00 PM and 8:00 AM clock-hours. The uveitis and glaucoma specialists should consider this potential for higher IOP fluctuations, while tailoring the glaucoma treatment in uveitic patients.

Ophthalmology of clinically normal alpacas (Vicugna pacos) in the United Kingdom: a cross-sectional study.

BackgroundAlpacas are being more frequently presented to veterinarians in the UK. It is important to validate whether published normal ocular parameters are consistent with the alpaca population in the UK.MethodsOphthalmic examinations were performed on healthy alpacas (Vicugna pacos) from three farms in East Anglia, UK.ResultsOn direct ophthalmoscopy of 35 alpacas, there was a 50 per cent prevalence of opacities within the lens in alpacas older than two years old (n=8/16). There was a 36.8 per cent prevalence of persistent hyaloid arteries in alpacas under two years old (n=7/19). The mean Schirmer tear test-1 value was 20.0 ±6 mm/minute (n=40). The mean intraocular pressure measured by rebound tonometry was 17.2 ±5.5 mmHg (n=46), and applanation tonometry resulted in statistically similar values (P=0.30; n=25). There was a significant variation in intraocular pressure throughout a 24-hour period (n=8). Fluorescein dye was not detected at the nostrils of any of the alpacas which underwent a Jones test to assess nasolacrimal duct patency (n=8).ConclusionThe ophthalmic findings appear largely consistent with previously published values from North America and continental Europe. Variations include the large range of measurements obtained and evidence of diurnal variation in intraocular pressure.

Initial experience in self-monitoring of intraocular pressure.

Background/aimsDiurnal variation in intraocular pressure (IOP) is a routine assessment in glaucoma management. Providing patients the opportunity to perform self-tonometry might empower them and free hospital resource. We previously demonstrated that 74% of patients can use the Icare® HOME tonometer. This study further explores Icare® HOME patient self-monitoring.MethodsPatients were trained by standard protocol to use the Icare® HOME rebound tonometer. Patient self-tonometry was compared to Goldmann applanation tonometry (GAT) over one clinical day. Following this, each patient was instructed to undertake further data collection that evening and over the subsequent two days.ResultsEighteen patients (35 eyes) participated. Good agreement was demonstrated between GAT and Icare® HOME for IOPs up to 15 mm Hg. Above this IOP the Icare® tended to over-read, largely explained by 2 patients with corneal thickness >600 um. The mean peak IOP during ‘clinic hours’ phasing was 16.7 mm Hg and 18.5 mm Hg (p = 0.24) over three days. An average range of 5.0, 7.0 and 9.8 mm Hg was shown during single day clinic, single day home and three day home phasing respectively (p =<0.001). The range of IOP was lower in eyes with prior trabeculectomy (6.1 mm Hg vs 12.2 mm Hg). All patients undertook one reading in the early morning at home with an average of 4.8 readings during, and 3.1 readings after office hours.ConclusionsThis small study shows that self-tonometry is feasible. The findings from home phasing demonstrated higher peak and trough IOPs, providing additional clinical information. Home phasing is a viable alternative. The cost-effectiveness of this approach has yet to be addressed.

Diurnal Variation of IOP in Angle Closure Disease: Are We Doing Enough?

Intraocular pressure (IOP) is known to have a definite circadian rhythm and its fluctuation correlates well with glaucoma progression. Twenty-four hour monitoring of IOP is an important indicator intraocular pressure fluctuation, as well as its peaks and spikes. However, Diurnal variation in IOP is well recognized but many decisions in glaucoma management are taken after one or two IOP measurements. Patient directed self-tonometry can be preformed through the twenty-four cycle, and has been the subject of an ongoing debate. In this review, we studied the history of self-tonometry devices and the present technologies for future. The results of various techniques studied revealed that a standardized method of conducting diurnal variation is yet to be ascertained, and for this, a proper research method is required.

Evaluation of influence of non-office hours diurnal variation of intraocular pressure in management of glaucoma

Aim and Objectives: This article attempts to elucidate the role of round the clock IOP control and its relevance to current glaucoma practice. Materials and Methods: A prospective observational study was carried out on 50 patients of POAG or CACG on medical management whose intraocular pressures were found to be controlled by daytime office hours IOP estimation. The diurnal IOP readings obtained with Clarkes Hand held Perkins applanation tonometer and Reicherts Tonopen at 7am, 10am, 1pm, 4pm, 7pm, 10pm, 1am and 4am. Comparison of office hours IOP, extended office hours DVT and 24 hours IOP was done. Results: Fifty patients were enrolled (mean age: 53.88 ± 8.42 years) in the study. The mean office hours IOP for both eyes was significantly less (16.31±2.46) than extended office hours (17.18±2.50) and 24 hours DVT (17.49 ±2.45). There was significant difference in IOP fluctuation in office (3.72±2.14) versus extended office hours (9.26±3.11) and 24 hours DVT (10.28±2.76). The mean office hours peak IOP was significantly lower than that of extended office hours and 24 hours DVT. Conclusion: 24-hour IOP monitoring can reveal higher peaks and wider fluctuation of IOP than those found during typical office hours, it suggests a greater role for IOP-related risk for glaucoma progression. Thus may justify a more aggressive IOP-lowering treatment strategy. Keywords: Chronic angle closure glaucoma (CACG), Clarkes hand held perkins applanation tonometer, Intraocular pressure (IOP), glaucoma, Primary open angle glaucoma (POAG), Reicherts tonopen.

Evaluation of influence of non-office hours diurnal variation of intraocular pressure in management of glaucoma

Evaluation of influence of non-office hours diurnal variation of intraocular pressure in management of glaucoma - IJCEO- Print ISSN No: - 2395-1443 Online ISSN No:- 2395-1451 Article DOI No:- 10.18231/j.ijceo.2019.039, Indian Journal of Clinical and Experimental Ophthalmology-Indian J Clin Exp Ophthalmol

Diurnal change of retinal vessel density and mean ocular perfusion pressure in patients with open-angle glaucoma.

PurposeTo investigate, in primary open-angle glaucoma (POAG) and healthy subjects, the pattern and magnitude of diurnal variation in optical coherence tomography angiography (OCTA) retinal vessel density (RVD).DesignProspective, observational cross-sectional study.ParticipantsA prospective study was conducted on 20POAG patients and 19 healthy subjects.MethodsPeripapillary/macular RVD (using swept-source OCTA), intraocular pressure (IOP), and systemic blood pressure (BP) were measured five times a day (8 a.m., 11 a.m., 2 p.m.,5 p.m. and 8 p.m.). The magnitudes and patterns of diurnal changes in RVD, diastolic BP, and mean ocular-perfusion pressure (MOPP) were analyzed and compared between the POAG patients and the healthy subjects.Main outcome measuresThe patterns and magnitudes of diurnal RVD change in OCTA.ResultsIntra-visit repeatability (0.755–0.943) and inter-visit reproducibility (0.843–0.986) for the RVD measurements showed excellent reliability. In the POAG patients, the magnitude of diurnal change in peripapillary RVD (9.71±7.04%) and macular RVD (7.22±4.73%) were significantly greater than that in the healthy group (5.73±3.85%, P = 0.013 and 5.51±3.45%, P = 0.042, respectively). The magnitudes of diurnal variations of IOP and MOPP in the POAG group likewise were greater than those in the healthy group (P = 0.003 and 0.039). As for the patterns of diurnal RVD change, interestingly, at 8 p.m., the macular RVD of the healthy group increased to the highest level (44.12±2.95%) while that of the POAG group decreased to the lowest level (40.41±2.54%).ConclusionsIn POAG eyes, diurnal change of IOP, MOPP and RVD was significantly greater than in the healthy eyes. These findings suggest that diurnal RVD changes might reflect the hemodynamic variation of POAG.

Impact of diurnal IOP variations on the dynamic corneal hysteresis measured with air-puff swept-source OCT

The deformation amplitudes measured with air-puff OCT are sensitive to both (intraocular pressure) IOP and biomechanical properties of the cornea. Analysis of the amplitudes of corneal deformation is challenging due to interrelation of IOP and corneal biomechanics. In this study, we used natural diurnal IOP fluctuations to investigate corneal deformations in a number of subjects whose eyes were measured multiple times during a day. The results of analysis, based on corneal hysteresis, revealed a corneal hysteresis parameter, which remains constant during a day for each individual eye. We hypothesize that above-mentioned metric might correlate with biomechanical properties of the cornea without influence of IOP. Full Text: PDF ReferencesMeek KM, Tuft SJ, Huang Y, Gill PS, Hayes S, Newton RH, Bron AJ, "Changes in Collagen Orientation and Distribution in Keratoconus Corneas", Invest Ophthalmol Vis Sci, 2005. 46(6): p. 1948-56. CrossRef Zimmermann DR, Fisher RW, Winterhalter KH, Witmer R, Vaughan L, "Comparative studies of collagens in normal and keratoconus corneas", Exp Eye Res, 1988. 46(3): p. 431-42. CrossRef Andreassen TT, Simonsen AH, and Oxlund H, "Biomechanical properties of keratoconus and normal corneas", Experimental Eye Research, 1980. 31(4): p. 435-441. CrossRef Heijl A, Leske MC, Bengtsson B, Hyman L, Bengtsson B, Hussein M, "Reduction of Intraocular Pressure and Glaucoma Progression", Arch Ophthalmol, 2002. 120(10): p. 1268-79. CrossRef Chauhan BC and Drance SM, "The influence of intraocular pressure on visual field damage in patients with normal-tension and high-tension glaucoma", Investigative Ophthalmology &amp; Visual Science, 1990. 31(11): p. 2367-2372. DirectLink Gelaw Y, "The impact of central corneal thickness on intraocular pressure among Ethiopian glaucoma patients: a cross-sectional study", BMC Ophthalmology, 2012. 12(1): p. 58. CrossRef Doughty MJ and Zaman ML, "Human Corneal Thickness and Its Impact on Intraocular Pressure Measures: A Review and Meta-analysis Approach", Surv Ophthalmol, 2000. 44(5): p. 367-408. CrossRef Liu J, and Roberts CJ, "Influence of corneal biomechanical properties on intraocular pressure measurement: Quantitative analysis", J Cataract Refract Surg, 2005. 31(1): p. 146-55. CrossRef Ehlers N, Hansen FK, and Aasved H, "Biometric Correlations of Corneal Thickness", Acta Ophthalmol (Copenh), 1975. 53(4): p. 652-9. CrossRef Harada Y, Hirose N, Tawara A, "The Influence of Central Corneal Thickness and Corneal Curvature Radius on The Intraocular Pressure as Measured By Different Tonometers: Noncontact and Goldmann Applanation Tonometers", J Glaucoma, 2008. 17(8): p. 619-25. CrossRef Alonso-Caneiro D, Karnowski K, Kaluzny BJ, Kowalczyk A, Wojtkowski M, "Assessment of corneal dynamics with high-speed swept source Optical Coherence Tomography combined with an air puff system", Optics Express, 2011. 19(15): p. 14188-14199. CrossRef Dorronsoro C, Pascual D, Perez-Merino P, Kling S and Marcos S, "Dynamic OCT measurement of corneal deformation by an air puff in normal and cross-linked corneas", Biomedical Optics Express, 2012. 3(3): p. 473-487. CrossRef Karnowski K, Kaluzny BJ, Szkulmowski M, Gora M, Wojtkowski M, "Corneal topography with high-speed swept source OCT in clinical examination", Biomedical Optics Express, 2011. 2(9): p. 2709-2720. CrossRef A. N. S. Institute, "American National Standard for Safe use of Lasers," (American National Standards Institute, Orlando, FL, 2000) DirectLink David R, Zangwill L, Briscoe D, Dagan M, Yagev R, Yassur Y, "Diurnal intraocular pressure variations: an analysis of 690 diurnal curves", Br J Ophthamlom, 1992, 76(5): p. 280-282 CrossRef Maczynska E, Karnowski K, Szulzycki K, Malinowska M, Dolezyczek H, Cichanski A, Wojtkowski M, Kaluzny BJ, Grulkowski I, Journal of Biophotonics (to be published).

Diurnal variations in intraocular pressure and central corneal thickness and the correlation between these factors in dogs.

To study the diurnal variation in intraocular pressure (IOP) and central corneal thickness (CCT) in healthy Beagles by rebound tonometry and ultrasonic pachymetry, respectively, in addition to determining whether a correlation exists between these two variables. Twenty eyes from 10 healthy Beagle dogs were included in the study. The IOP and CCT were measured by rebound tonometry and ultrasonic pachymetry, respectively, at 2-h intervals over an 8-hour period between 10:00 and 18:00. The mean values (± SD) of IOP obtained were 11.45±2.96 at 10:00, 10.00±1.89 at 12:00, 8.25±1.62 at 14:00, 7.05±1.05 at 16:00, and 6.55±1.36 at 18:00. The mean values (± SD) of CCT obtained were 554.95±72.41 at 10:00, 549.20±69.10 at 12:00, 566.15±80.56 at 14:00, 545.45±70.19 at 16:00, and 538.30±73.33 at 18:00. The IOP and CCT of dogs were found to decrease progressively from the first to the last measurement. There were statistically significant differences between the IOP (P=0.000) and CCT values (P=0.032) measured at different times of the day. There was no effect or interaction between gender and eye with the dependent variables. The IOP and CCT were found to be positively correlated (r=0.213, P=0.034). The regression equationdemonstrated that for every 100μm increase in CCT, there was an elevation in IOP by 0.8mmHg. The CCT and IOP values were lower in the afternoon/evening than in the morning, and these were positively correlated. Both findings are important for the diagnostic interpretation of IOP values in dogs.