Associations of long-term fluctuation in blood pressure and ocular perfusion pressure with visual field progression in normal-tension glaucoma

BACKGROUD

The aim of this study was to investigate the associations between fluctuation in blood pressure (BP), ocular perfusion pressure (OPP) and visual field (VF) progression in normal-tension glaucoma (NTG).

METHODS

This prospective, longitudinal study included 44 patients with NTG. Only newly diagnosed NTG patients who had not been treated with a glaucoma medication were included. Patients were examined every year for 7 years. Intraocular pressure (IOP), heart rate (HR), systolic BP (SBP), diastolic BP (DBP), ocular perfusion pressure (OPP), and diastolic ocular perfusion pressure (DOPP) were measured at the same time. Ophthalmic examinations, including perimetry, were performed also. Initial VF were compared with follow-up data after 7 years.

RESULTS

After 7 years of follow-up, 9 of the 44 patients showed VF progression. The standard deviation (SD) of SBP and OPP were significantly associated with VF progression (P = 0.007, < 0.001, respectively). Multiple regression analysis showed that VF progression was significantly associated with SD of OPP (odds ratio, OR = 2.012, 95% CI = 1.016-3.985; P = 0.045).

CONCLUSIONS

Fluctuation in OPP was associated with VF progression in patients with NTG.

Non-arteritic anterior ischemic optic neuropathy secondary to Posner-Schlossman syndrome in a twenty-six-year-old female

Purpose

To describe a case of non-arteritic ischemic optic neuropathy (NAION) secondary to Posner-Schlossman syndrome in a twenty-six-year-old female.

Observations

A 26-year-old female presented with painful visual loss of the left eye, elevated intraocular pressure of 38 mmHg, and trace to 1+ anterior chamber cell. Diffuse optic disc edema in the left eye and a small cup-to-disc ratio of the right optic disc were evident. Magnetic resonance imaging was unremarkable.

Conclusions and Importance

The patient was diagnosed with NAION secondary to Posner-Schlossman syndrome, an uncommon ocular entity that can significantly affect vision. Posner-Schlossman syndrome can cause a decrease in ocular perfusion pressure involving the optic nerve and can lead to ischemia, swelling, and infarction. NAION should be considered in the differential diagnosis of young patients with sudden development of optic disc swelling and increased intraocular pressure with normal magnetic resonance imaging findings.

Evaluation of macular microvascular density using optical coherence tomography angiography in patients with Posner-Schlossman syndrome

BACKGROUND

Optical coherence tomography angiography (OCTA) is a novel technology that provides a noninvasive, dye-less method to visualize the blood vessels of the retina. In the present study, we investigate macular microvascular density and the correlation of ocular and demographic factors using OCTA in Posner-Schlossman syndrome (PSS) patients.

METHODS

This is a prospective observational study. All PSS patients and age- and sex-matched healthy subjects underwent complete ophthalmologic examination, and RE, BCVA, IOP, CCT, AL, CMT, GCIPI, RNFL, C/D ratio were recorded. The whole-image vessel density (wiVD) and whole-image perfusion density (wiPD), three-circle (1 mm central ring, 3 mm inner ring, 6 mm outer ring), and four-quadrant segmental VD and PD were calculated.

RESULTS

Seventeen PSS patients and 17 healthy subjects were enrolled in this study. The mean age was 42.65 ± 11.22 years in PSS patients and 42.71 ± 10.50 years in healthy controls. IOP, CCT, and C/D ratio were higher in PSS-attacked eyes, and BCVA, OPP and RNFL thickness was lower than those in the fellow eyes (p < 0.05). BCVA and OPP were improved in the PSS-attacked eyes in intermittent period (p < 0.05). The wiVD and wiPD were lower in the PSS-affected eyes than in the fellow eyes and in the control eyes in the PSS-attacked period (p < 0.05). All segmental VD and PD was lower in the PSS affected eyes than in the healthy control eyes (p < 0.05). In intermittent period, the wiVD and wiPD were lower in the PSS-affected eyes than in the fellow eyes (p < 0.05). Age, CCT, and SSI were associated with macular wiVD and wiPD in PSS attacked period. Age and CCT were associated with macular wiVD and wiPD in PSS intermittent period.

CONCLUSION

Decreased macular superficial VD and PD was found in patients with Posner-Schlossman syndrome in attacked period and in remission. Macular wiVD and wiPD were associated with age, CCT and SSI in PSS patients.

Ocular Perfusion Pressure and Severity of Glaucoma: Is There a Link?

Aim and objective

To establish the association between 12-month inter-visits ocular perfusion pressure (OPP) and severity of glaucoma.

Materials and methods

A total of 164 eyes (60 primary open-angle glaucoma, 52 normal-tension glaucoma, and 52 primary angle-closure glaucoma) of 164 patients were analyzed in this prospective cohort study. Patients who demonstrated good compliance to treatment were recruited. The severity of glaucoma was stratified according to the Advanced Glaucoma Intervention Study (AGIS) score based on reliable and reproducible visual field analysis at baseline. OPP was obtained at baseline and a 3-monthly follow-up visit over a 12-month duration. The pattern and fluctuation of mean OPP were studied. Repetitive measure ANOVA and one-way ANOVA were used for statistical analysis.

Results

The inter-visits mean OPP (p = 0.010), systolic OPP (p = 0.020), diastolic OPP (p = 0.010), systolic blood pressure (p = 0.040), and diastolic blood pressure (p = 0.006) showed significant difference with severity of glaucoma. There was no significant difference between mean inter-visits intraocular pressure (IOP) and severity of glaucoma (p = 0.410). The end-stage glaucoma group had the lowest mean OPP and widest inter-visit mean OPP fluctuation. Early and mild glaucoma patients demonstrated higher mean OPP compared with moderate, severe, and end-stage glaucoma.

Conclusion

There is a significant association between OPP and the severity of glaucoma. Balancing blood pressure and IOP is important in optimizing adequate perfusion and prevent further damage to the optic nerve head.

How to cite this article

Ch'ng TW, Chua CY, Ummi Kalsom MA, et al. Ocular Perfusion Pressure and Severity of Glaucoma: Is There a Link? J Curr Glaucoma Pract 2021;15(2):78–85.

Effect of adding clonidine to lidocaine on ocular hemodynamics during sub-Tenon's anesthesia: randomized double-blind study

INTRODUCTION AND OBJECTIVES

Different regional anesthesia techniques for ophthalmology can have hemodynamic effects on the eye. We assessed the effects of adding clonidine to lidocaine on Intraocular Pressure (IOP), Ocular Pulse Amplitude (OPA), and Ocular Perfusion Pressure (OPP) after the sub-Tenon's technique for cataract surgery.

METHODS

The study included 40 patients randomly allocated into two groups: sub-Tenon's blockade with Lidocaine plus Saline Solution (LS) or Lidocaine plus Clonidine (LC). IOP, OPA and OPP were measured before anesthesia, and 1, 5 and 10 minutes after the injection of anesthetic solution.

RESULTS

There was no difference between the groups in IOP, OPA, and OPP baseline values. After the injection of the anesthetic solution, the IOP increased in both groups at minute one, with a mean difference of +4.67 mmHg (p = 0.001) and +2.15 mmHg (p = 0.013) at 5 minutes. The increase was lower in the LC group when compared to LS (p = 0.027). OPA decreased in both groups, with a baseline difference, after 1 minute, of -0.85 mmHg (p =  -0.85 mmHg (p = 0.001), and at 5 and 10 minutes with differences of -1.17 (p = 0.001) and -0.89 mmHg (p = 0.001), respectively. The highest decrease was observed in group LC in relation to group LS (p = 0.03). There was no difference in OPP in relation to baseline measurements.

CONCLUSIONS

Adding clonidine to lidocaine for sub-Tenon's anesthesia reduced IOP and OPA without significant changes in OPP.

Effects of isometric resistance exercise of the lower limbs on intraocular pressure and ocular perfusion pressure among healthy adults: A meta-analysis

BACKGROUND

The main risks for glaucoma are increased intraocular pressure (IOP) and decreased ocular perfusion pressure (OPP). This review aims to examine the potential impact of lower limb isometric resistance exercise on intraocular pressure and ocular perfusion pressure.

METHOD

A meta-analysis was conducted to determine the potential impact of isometric exercise on IOP and OPP. The literature on the relationship between isometric resistance exercise and IOP was systematically searched according to the "Cochrane Handbook" in the databases of Pubmed, Web of Science, EBSCO, and Scopus through December 31, 2020. The search terms used were "exercise," "train," "isometric," "intraocular pressure," and "ocular perfusion pressure," and the mean differences of the data were analyzed using the Stata 16.0 software, with a 95% confidence interval.

RESULTS

A total of 13 studies, which included 268 adult participants consisting of 162 men and 106 women, were selected. All the exercise programs that were included were isometric resistance exercises of the lower limbs with intervention times of 1min, 2min, or 6min. The increase in IOP after intervention was as follows: I²=87.1%, P=0.001 using random-effects model combined statistics, SMD=1.03 (0.48, 1.59), and the increase in OPP was as follows: I²=94.5%, P=0.001 using random-effects model combined statistics, SMD=2.94 (1.65, 4.22), with both results showing high heterogeneity.

CONCLUSION

As isometric exercise may cause an increase in IOP and OPP, therefore, people with glaucoma and related high risk should perform isometric exercise with caution.

Mechanistic links between systemic hypertension and open angle glaucoma

Systemic hypertension or hypertension is a very common chronic age-related disease worldwide. It is typically characterised by a sustained elevation of blood pressure, particularly when the systolic blood pressure and/or diastolic blood pressure are of more than 140 mmHg and 90 mmHg, respectively. If hypertension is not well controlled, it may lead to an increased risk of stroke and heart attack. It has been shown that hypertension is linked to various ocular diseases, including cataract, diabetic retinopathy, age-related macular degeneration, and glaucoma. Glaucoma is the leading cause of irreversible blindness worldwide. Primary open angle glaucoma is the most common form of the disease and is usually characterised by an increase in intraocular pressure. This condition, together with normal tension glaucoma, constitutes open angle glaucoma. Systemic hypertension has been identified as a risk factor for open angle glaucoma. It is speculated that blood pressure is involved in the pathogenesis of open angle glaucoma by altering intraocular pressure or ocular blood flow, or both. Recent evidence has shown that both extremely high and low blood pressure are associated with increased risk of open angle glaucoma. Additional pathogenic mechanisms, including increased inflammation likely to be involved in the development and progression of these two diseases, are discussed.

The intraocular pressure responses to oral academic examination: The influence of perceived levels of public speaking anxiety

We examined the intraocular pressure responsiveness to oral examination stress, as well as the mediating role of the perceived levels of public speaking anxiety on intraocular pressure changes. Thirty-two university students (intervention group) publicly defended their degree final project, and intraocular pressure and perceived levels of stress were measured before and after the oral presentation, and after 10 min of recovery. The control group (n = 32) was not exposed to any stressful situation, and the dependent measures were taken at the same time points. All participants completed the public speaking anxiety scale. The intervention group exhibited higher intraocular pressure values before the oral presentation (corrected p-values<0.001), with these changes being positively associated with the perceived levels of public speaking anxiety (p < 0.001, r = 0.71). Our results reveal a mediating role of public speaking anxiety on the intraocular pressure responsiveness to oral examination stress, and highlight the utility of intraocular pressure as an indicator of stress in applied situations.

Association between Mean Ocular Perfusion Pressure and Diabetic Retinopathy in a Northeastern Chinese Population

OBJECTIVE

To evaluate the association between diabetic retinopathy (DR) and mean ocular perfusion pressure (MOPP) in patients with type 2 diabetes mellitus (T2DM).

METHODS

Patients from the Fushun Diabetic Retinopathy Cohort Study (FS-DIRECT), a community-based prospective cohort study conducted in northeast China, were included in this study. The presence and severity of DR were determined by grading fundus photographs according to the Early Treatment Diabetic Retinopathy Study (ETDRS) retinopathy scale. Systolic and diastolic blood pressure (SBP and DBP) were recorded using an electronic sphygmomanometer. Intraocular pressure (IOP) was measured using an iCare rebound tonometer. MOPP was calculated using the formula MOPP = 2/3 [DBP + 1/3 (SBP - DBP)] - IOP.

RESULTS

In total, 1,857 patients who had gradable fundus photography and MOPP data were enrolled in this study. Male patients had a higher MOPP than female patients (52.25 ± 8.75 vs. 50.96 ± 8.74 mmHg, P = 0.002). Overall, both male and female patients with any type of DR, non-proliferative DR (NPDR), or non-sight-threatening DR (non-STDR) had significantly higher MOPP relative to patients without DR. Increased MOPP (per 1 mmHg) was in turn associated with the presence of any type of DR [odds ratio ( OR) = 1.03, 95% confidence interval ( CI) : 1.02-1.04], NPDR ( OR= 1.03 95% CI: 1.02-1.04), and non-STDR ( OR= 1.03, 95% CI: 1.01-1.04) after adjusting for confounders. Increased MOPP (per 1 mmHg) was also associated with an increased likelihood of macular edema ( OR= 1.02 , 95% CI: 1.01-1.04).

CONCLUSIONS

The results suggest that increased MOPP was associated with DR and macular edema in northeastern Chinese patients with T2DM.

Non-invasive Assessment of Central Retinal Artery Pressure: Age and Posture-dependent Changes

Purpose: Assessment of Ocular Perfusion Pressure (OPP) requires estimation of the Mean Central Retinal Artery Pressure (MCRAP) [OPP = MCRAP-IOP]. In a seated position, MCRAP is currently estimated as 2/3 of the Mean Arterial Pressure (MAP) to account for the hydrostatic reduction of MAP at eye level. We tested a surrogate method for direct MCRAP assessment by measuring MAP with Arm-Up and cuff at eye level (AUMAP) at different postures and ages. Methods: MAP and AUMAP were assessed in a mixed population of 136 subjects (mean age 44 ± 17.39 years) including healthy participants (N = 30) and patients with optic neuropathies (Glaucoma suspects, N = 14; Open-Angle Glaucoma, N = 26, LHON, N = 19; MS, N = 47) not expected to alter systemic blood pressure. None of the subjects had history of carotid stenosis or pharmacological treatment to regulate blood pressure. AUMAP was also tested in two subgroups in supine (N = 42) and -10° Head Down body Tilt position (HDT, N = 46). Results: In the seated position, both 2/3MAP and AUMAP increased with increasing age, however with steeper (2x) slope for AUMAP (P < .0001). With decreasing angle of body tilt, AUMAP increased while MAP decreased. The mean AUMAP/MAP ratio (posture coefficient) was, seated, 0.73 (SE 0.003); supine, 0.90 (SE 0.005); HDT, 0.97 (SE 0.005). In the seated position only, the AUMAP/MAP ratio significantly increased with age (P < .0001). Mean posture coefficients obtained with AUMAP were in the range of those based on either direct ophthalmodynamometric measurements or hydrostatic estimations. Conclusions: Surrogate measurement of MCRAP in individual subjects is feasible using the simple AUMAP approach that provides a straightforward estimation of OPP (OPP = AUMAP - IOP) at different body postures. The standard method OPP = 2/3*MAP-IOP in the seated posture underestimates OPP at older ages. Clinical estimation of OPP would benefit from the use of AUMAP, in particular for head-down postures.

Systemic and ocular determinants of mean ocular perfusion pressure in a population-based sample

PURPOSE

To investigate the associations between mean ocular perfusion pressure (MOPP) and several variables including body mass index (BMI), comorbid medical conditions and various ocular parameters in a population-based sample.

STUDY DESIGN

Cross-sectional.

METHODS

Data of 2091 healthy participants from a previous population based cross-sectional study were reviewed. Inclusion criteria were adults ≥40 years of age who were screened on-site for glaucoma. Data on medical history, height, weight, systolic and diastolic blood pressures (SBP and DBP, respectively) were obtained. A basic ocular examination was performed which included intraocular pressure (Tono-Pen XL, Reichert Technologies) and central corneal thickness (Pacline pachymetry;) measurement, slit-lamp examination and non-mydriatic optic disc photography (nonmydα fundus camera, Kowa). MOPP was calculated using the formula [2/3 x (DBP + 1/3(SBP-DBP)]-IOP and low MOPP was defined as MOPP ≤45 mmHg.

RESULTS

Mean age of the subjects was 63.04 ± 9.7 years (range: 44 and 99 years) and the majority were women (74.1%, n = 1549). Mean MOPP values in normal weight (BMI < 25), overweight (BMI = 25-29.9) and in obese individuals were 46.9 ± 9.0 mmHg, 48.6 ± 9.2 mmHg and 50.7 ± 10.0 mmHg, respectively (p < 0.001, in all pairwise comparisons). In the multivariable logistic regression analysis, migraine and IOP elevation (per 1 mmHg increment) were significantly associated with a low MOPP (OR: 2.10 and 1.22, p = 0.008 and < 0.001, respectively). On the other hand, risk of low MOPP was reduced in subjects with hypertension, and with increasing age (per 1-year increment) and BMI (per 1-unit increment) (OR: 0.15, 0.97, and 0.95, respectively, and p < 0.001 for all).

CONCLUSION

Migraine and elevated IOP increase the risk of low MOPP and this may have a causal relationship with impaired optic nerve head blood flow.

Exercise-Induced Changes in Ocular Blood Flow Parameters in Primary Open-Angle Glaucoma Patients

PURPOSE

To evaluate exercise-induced changes in ocular blood flow (OBF) parameters in primary open-angle glaucoma (POAG) patients.

METHODS

A prospective observational study was carried out, in which medically treated patients with POAG were enrolled. Following inclusion, all patients performed a 40-min cycloergometry in a standardized fashion. The following parameters were measured and compared immediately before and 1 and 30 min after the exercise: intraocular pressure (IOP; Goldman applanation tonometry), mean arterial pressure (MAP), ocular pulse amplitude (OPA; assessed by dynamic contour tonometry), and ocular perfusion pressure (OPP; 2/3 MAP - IOP). In addition, we investigated possible factors associated with OBF parameter changes immediately after exercise.

RESULTS

A total of 30 eyes (30 patients; mean age was 62.9 ± 1.7 years) were included. Most patients were women (53%), and median visual field mean deviation index was -3.5 dB. Both MAP (mean change, 21%) and IOP (mean change, 17.3%) increased significantly immediately after the workout (p < 0.01), persisting higher than baseline following 30 min (p < 0.01%). Regarding OBF parameters, both OPA (mean change, 58.8%) and OPP (mean change, 21.7%) increased significantly immediately after the workout and persisted higher than baseline 30 min after the workout (p < 0.01). Regression analysis revealed that only age was significantly associated with OPA variation (R2 0.14; p < 0.05). No significant associations were found for OPP (p ≥ 0.19).

CONCLUSION

Aerobic exercise leads to a significant short-time increase in OBF parameters in patients with POAG. Even though IOP seems to present a modest elevation, it is accompanied by a significant increase in MAP, leading to higher OBF measurements. Exercise-induced short-term changes and its possible implications for glaucoma prognosis deserve further investigation.

Effects of caffeine on intraocular pressure are subject to tolerance: a comparative study between low and high caffeine consumers

BACKGROUND

Caffeine has a well-established effect on intraocular pressure (IOP) and ocular perfusion pressure (OPP); however, the possible differences between low- and high-caffeine consumers remain unknown.

METHODS

In this placebo-controlled, double-blind, and balanced crossover study, 40 healthy individuals were divided in low- (n = 21) and high (n = 19)-caffeine consumers, according to their daily caffeine consumption. All participants ingested either caffeine (4 mg/kg) or placebo, and IOP and OPP were measured after 30, 60, and 90 min of ingesting caffeine or placebo. Subjective feelings of arousal were also obtained.

RESULTS

Caffeine induced an acute IOP rise (p < 0.001, ƞ_p² = 0.408), whereas habitual caffeine demonstrated a mediating effect on the IOP changes induced by caffeine intake, with high-caffeine consumers showing a less accentuated IOP rise in comparison to low-caffeine consumers. The greatest IOP change induced by caffeine intake was reached after 90 min from capsule ingestion, being more accentuated for the low-caffeine consumers (+ 3.4 mmHg) than for the high-caffeine consumers (+ 1.2 mmHg). Consequently, the participants reported higher levels of perceived arousal after ingesting caffeine in comparison to placebo (p = 0.002, ƞ_p² = 0.222); however, similar responses were given by high- and low-caffeine consumers (p = 0.256). Our data did not reveal any effect of caffeine consumption on OPP (p = 0.304).

CONCLUSIONS

These results suggest that IOP responsiveness to caffeine ingestion is subject to tolerance, which could have important implication in the management of glaucoma. This finding may be due to alterations in the adenosine receptor system caused by chronic caffeine consumption. Future studies are needed to assess if these findings are also applicable to patients with glaucoma.

Heart rate variability: the comparison between high tension and normal tension glaucoma

RELEVANCE

Vascular factors may be involved in the development of both high tension glaucoma (HTG) and normal tension (NTG) glaucoma; however, they may be not exactly the same. Autonomic dysfunction characterized by heart rate variability (HRV) is one of the possible reasons of decrease in mean ocular perfusion pressure (MOPP).

PURPOSE

To compare the shift of the HRV parameters in NTG and HTG patients after a cold provocation test (CPT).

METHODS

MOPP, 24-hour blood pressure and HRV were studied in 30 NTG, 30 HTG patients, and 28 healthy subjects. The cardiovascular fitness assessment was made before and after the CPT. The direction and magnitude of the average group shifts of the HRV parameters after CPT were assessed using the method of comparing regression lines in order to reveal the difference between the groups.

RESULTS

MOPP and minimum daily diastolic blood pressure were decreased in HTG and NTG patients compared to healthy subjects. There was no difference in MOPP between HTG and NTG before the CPT. However, all HRV parameters reflected the predominance of sympathetic innervation in glaucoma patients compared to healthy subjects (P < 0.05).Before the CPT, the standard deviation of NN intervals (SDNN) of HRV was lower in HTG compared to NTG, 27.2 ± 4.1 ms and 35.33 ± 2.43 ms (P = 0.02), respectively. After the CPT, SDNN decreased in NTG by 1.7 ms and increased in HTG and healthy subjects by 5.0 ms and 7.09 ms, respectively (P < 0.05). The analysis of relative shift of other HRV parameters after the CPT also revealed a significant difference between NTG and HTG in regard to the predominance of sympathetic innervation in NTG compared to HTG.

CONCLUSION

Patients with NTG have more pronounced disturbance of autonomic nervous system than HTG patients, which is manifested with the activation of sympathetic nervous system in response to CPT. This finding refers to the NTG pathogenesis and suggests the use of HRV assessment in glaucoma diagnosis and monitoring.

Effect of interscalene block on intraocular pressure and ocular perfusion pressure

BACKGROUND

Interscalene block (ISB) is commonly associated with Horner's syndrome due to spread of local anesthetic to the cervical sympathetic chain. Postganglionic neurons that originate from superior cervical ganglia form the sympathetic innervation of eye. Decrease in sympathetic tone may change intraocular pressure (IOP) and ocular perfusion pressure (OPP). The aim of the study was to investigate whether ISB affects IOP and/or OPP.

METHODS

Thirty patients scheduled for ambulatory shoulder surgery under regional anesthesia with a single-shot ISB (15 mL 0.5% bupivacaine and 15 mL 2% lidocaine) were recruited. The IOP and OPP in both eyes, mean arterial pressure (MAP), heart rate (HR) and end-tidal CO₂ (ETCO₂) were measured before ISB and 5, 10, 20, 30 and 60 min after ISB in the beach-chair position.

RESULTS

The baseline IOP and OPP were similar in the blocked and unblocked sides (IOP 17.60 ± 1.69 and 17.40 ± 1.96 respectively p = 0.432; OPP 49.80 ± 8.20 and 50 ± 8.07 respectively p = 0.432). The IOP in the blocked side significantly decreased between 10th to 60th min following ISB, compared to the baseline values (p < 0.001). The OPP in the blocked side significantly increased from 10th to 60th min (p < 0.001) whereas, there were no significant changes in IOP and OPP throughout the measurement period in the unblocked side.

CONCLUSIONS

ISB decreased IOP in the blocked side. ISB could be considered as a safe regional technique of choice in elderly patients at high risk for developing glaucoma.

Ocular perfusion pressure control during pars plana vitrectomy: testing a novel device

PURPOSE

To study the efficacy of a novel device intended to control infusion pressure based on mean ocular perfusion pressure (MOPP) during pars plana vitrectomy (PPV).

METHODS

An arm blood pressure cuff connected to a vitrectomy machine calculated mean arterial pressure (MAP), while a pressure sensor close to the infusion trocar measured intraocular pressure (IOP). MOPP was calculated in real time in 36 consecutive patients undergoing PPV, who were divided into two groups. The device lowered IOP every time that calculated MOPP fell below 30 mmHg in the Control ON group (18 patients), while no action was taken in the Control OFF group (18 patients).

RESULTS

Baseline IOP and blood pressure were similar between groups. The Control ON group had significantly lower average intraoperative IOP (30.5 ± 2.1 vs. 35.9 ± 6.9 mmHg; p = 0.002) and higher MOPP (56.4 ± 5.9 vs. 49.7 ± 6.1 mmHg) than the Control OFF group. The Control ON group also spent less time at MOPP < 10 mmHg and < 30 mmHg: 0 vs. 3.40 ± 2.38 min (p < 0.001) and 9.91 ± 7.15 vs. 16.13 ± 8.12 min (p = 0.02), respectively.

CONCLUSIONS

The MOPP control device effectively maintained lower IOP and higher MOPP throughout surgery. It also helped avoid dangerous IOP peaks and MOPP dips, allowing patients to spend less time at MOPP of < 10 and < 30 mmHg.

The effect of age on the response of retinal capillary filling to changes in intraocular pressure measured by optical coherence tomography angiography

PURPOSE

To compare the effect of elevated intraocular pressure (IOP) on retinal capillary filling in elderly vs adult rats using optical coherence tomography angiography (OCTA).

METHODS

The IOP of elderly (24-month-old, N=12) and adult (6-8month-old, N=10) Brown Norway rats was elevated in 10mmHg increments from 10 to 100mmHg. At each IOP level, 3D OCT data were captured using an optical microangiography (OMAG) scanning protocol and then post-processed to obtain both structural and vascular images. Mean arterial blood pressure (MAP), respiratory rate, pulse and blood oxygen saturation were monitored non-invasively throughout each experiment. Ocular perfusion pressure (OPP) was calculated as the difference between MAP for each animal and IOP at each level. The capillary filling index (CFI), defined as the ratio of area occupied by functional capillary vessels to the total scan area but excluding relatively large vessels of >30μm, was calculated at each IOP level and analyzed using the OCTA angiograms. Relative CFI vs IOP was plotted for the group means. CFI vs OPP was plotted for every animal in each group and data from all animals were combined in a CFI vs OPP scatter plot comparing the two groups.

RESULTS

The MAP in adult animals was 108±5mmHg (mean±SD), whereas this value in the elderly was 99±5mmHg. All other physiologic parameters for both age groups were uniform and stable. In elderly animals, significant reduction of the CFI was first noted at IOP 40mmHg, as opposed to 60mmHg in adult animals. Individual assessment of CFI as a function of OPP for adult animals revealed a consistent plateau until OPP reached between 40 and 60mmHg. Elderly individuals demonstrated greater variability, with many showing a beginning of gradual deterioration of CFI at an OPP as high as 80mmHg. Overall comparison of CFI vs OPP between the two groups was not statistically significant.

CONCLUSIONS

Compared to adults, some, but not all, elderly animals demonstrate a more rapid deterioration of CFI vs OPP. This suggests a reduced autoregulatory capacity that may contribute to increased glaucoma susceptibility in some older individuals. This variability must be considered when studying the relationship between IOP, ocular perfusion and glaucoma in elderly animal models.

Postural effects on intraocular pressure and ocular perfusion pressure in patients with non-arteritic anterior ischemic optic neuropathy

BACKGROUND

To investigate postural effects on intraocular pressure (IOP) and ocular perfusion pressure (OPP) in patients with non-arteritic ischemic optic neuropathy (NAION).

METHODS

IOP and blood pressure (BP) were measured in 20 patients with unilateral NAION 10 min after changing to each of the following positions sequentially: sitting, supine, right lateral decubitus position (LDP), supine, left LDP, and supine. IOP was measured using a rebound tonometer and OPP was calculated using formulas based on mean BP. The dependent LDP (DLDP) was defined as the position when the eye of interest (affected or unaffected eye) was placed on the dependent side in the LDP.

RESULTS

IOPs were significantly higher (P = 0.020) and OPPs were significantly lower (P = 0.041) in the affected eye compare with the unaffected eye, with the affected eye in DLDP. Compared with the mean IOP of the unaffected eyes, the mean IOP of the affected eyes increased significantly (+2.9 ± 4.4 versus +0.7 ± 3.1 mmHg, respectively; P = 0.003) and the mean OPP decreased significantly (-6.7 ± 9.4 versus -4.9 ± 8.0 mmHg, respectively; P = 0.022) after changing positions from supine to DLDP. In addition, changing position from supine to DLDP showed significantly larger absolute changes in IOP (4.13 ± 3.19 mmHg versus 2.51 ± 1.92 mmHg, respectively; P = 0.004) and OPP (9.86 ± 5.69 mmHg versus 7.50 ± 5.49 mmHg, respectively; P = 0.009) in the affected eye compared with the unaffected eye. In the affected eye, there was a significant positive correlation between absolute change in IOP and OPP when changing position from supine to DLDP (Rho = 0.512, P = 0.021).

CONCLUSIONS

A postural change from supine to DLDP caused significant fluctuations in IOP and OPP of the affected eye, and may significantly increase IOP and decrease OPP. Posture-induced IOP changes may be a predisposing factor for NAION development.

Current Imaging Modalities for assessing Ocular Blood Flow in Glaucoma

Glaucoma may be caused by an interplay of elevated intraocular pressure (IOP), vascular, genetic, anatomical, brain, and immune factors. The direct assessment of ocular hemodynam-ics offers promise for glaucoma detection, differentiation, and possibly new treatment modalities. All the methods currently in use to measure ocular blood flow have inherent limitations and measure different aspects of ocular blood flow. This review article attempts to provide detailed information on ocular perfu-sion pressure as well as an overview of the newly developed imaging technologies used to investigate ocular blood flow in glaucoma patients.

HOW TO CITE THIS ARTICLE

Mohindroo C, Ichhpujani P, Kumar S. Current Imaging Modalities for assessing Ocular Blood Flow in Glaucoma. J Curr Glaucoma Pract 2016;10(3):104-112.

Twenty-four-hour efficacy of preservative-free tafluprost for open-angle glaucoma patients, assessed by home intraocular pressure (Icare-ONE) and blood-pressure monitoring

PURPOSE

To evaluate the effect of preservative-free (PF) tafluprost on diurnal variation of intraocular pressure (IOP) and ocular perfusion pressure (OPP), measured by use of home IOP and blood-pressure (BP) monitoring devices, for primary open angle glaucoma (POAG) patients.

METHODS

Twenty-two eyes from 22 patients with POAG were studied. Initially, IOP was measured at the hospital by Goldmann applanation tonometry (GAT) and Icare-ONE rebound tonometry. Each patient was then instructed how to use the Icare-ONE and BP home monitoring devices. IOP and BP were measured at home by the patients, every 4 h, before and 2 weeks after once daily treatment with PF tafluprost (0.0015%) ophthalmic solution.

RESULTS

Intraclass correlations between different IOP measurements were greater than 0.8. PF tafluprost reduced mean diurnal IOP significantly for patients with POAG, from 15.7 ± 1.2 mmHg at baseline to 12.5 ± 0.6 mmHg 2 weeks after treatment (p < 0.001). It increased mean diurnal OPP from 48.5 ± 7.3 mmHg at baseline to 51.3 ± 7.0 mmHg post-treatment (p < 0.017).

CONCLUSIONS

Icare-ONE enables glaucoma patients to measure their own diurnal IOP fluctuations. Patient-measured Icare-ONE IOP readings showed that PF tafluprost effectively reduced diurnal IOP in eyes with POAG.

Ocular Perfusion Pressure and Pulsatile Ocular Blood Flow in Normal and Systemic Hypertensive Patients

Purpose: Glaucomatous neuropathy can be a consequence of insufficient blood supply, increase in intraocular pressure (IOP), or other risk factors that diminish the ocular blood flow. To determine the ocular perfusion pressure (OPP) in normal and systemic hypertensive patients.

Materials and methods: One hundred and twenty-one patients were enrolled in this prospective and comparative study and underwent a complete ophthalmologic examination including slit lamp examination, Goldmann applanation tonometry, stereoscopic fundus examination, and pulsatile ocular blood flow (POBF) measurements. The OPP was calculated as being the medium systemic arterial pressure (MAP) less the IOP. Only right eye values were considered for calculations using Student’s t-test.

Results: The mean age of the patients was 57.5 years (36-78), and 68.5% were women. There was a statistically significant difference in the OPP of the normal and systemic hypertensive patients (p < 0.05). The difference in the OPP between these groups varied between 8.84 and 17.9 mm Hg.

Conclusion: The results of this study suggest that although the systemic hypertensive patients have a higher OPP in comparison to normal patients, this increase does not mean that they also have a higher OBF (as measured by POBF tonograph). This may be caused by chronic changes in the vascular network and in the blood hemodynamics in patients with systemic hypertension.

How to cite this article: Kanadani FN, Figueiredo CR, Miranda RM, Cunha PLT, Kanadani TCM, Dorairaj S. Ocular Perfusion Pressure and Pulsatile Ocular Blood Flow in Normal and Systemic Hypertensive Patients. J Curr Glaucoma Pract 2015;9(1):16-19.

Coupling blood flow and neural function in the retina: a model for homeostatic responses to ocular perfusion pressure challenge

Retinal function is known to be more resistant than blood flow to acute reduction of ocular perfusion pressure (OPP). To understand the mechanisms underlying the disconnect between blood flow and neural function, a mathematical model is developed in this study, which proposes that increased oxygen extraction ratio compensates for relative ischemia to sustain retinal function. In addition, the model incorporates a term to account for a pressure-related mechanical stress on neurons when OPP reduction is achieved by intraocular pressure (IOP) elevation. We show that this model, combining ocular blood flow, oxygen extraction ratio, and IOP mechanical stress on neurons, accounts for retinal function over a wide range of OPP manipulations. The robustness of the model is tested against experimental data where ocular blood flow, oxygen tension, and retinal function were simultaneously measured during acute OPP manipulation. The model provides a basis for understanding the retinal hemodynamic responses to short-term OPP challenge.

Low nocturnal ocular perfusion pressure as a risk factor for normal tension glaucoma

OBJECTIVES

In the absence of raised intraocular pressure (IOP), haemodynamic parameters have been implicated in the development of normal tension glaucoma (NTG). The purpose of this study is to compare 24-hour IOP and haemodynamic parameters in NTG patients and non-glaucoma patients.

METHODS

This is a cross sectional study involving 72 NTG patients from University of Malaya Medical Centre eye clinic glaucoma registry. The non-glaucoma patients were volunteers selected from eye clinic patients. All enrolled patients underwent 24-hour IOP and blood pressure monitoring via 2-hourly IOP and blood pressure (BP) measurements. All readings were taken in the sitting position during the diurnal period and in the supine position during the nocturnal period

RESULTS

Comparison of the haemodynamic parameters, the nocturnal mean systolic BP, nocturnal mean diastolic BP and nocturnal mean arterial pressure (MAP) were significantly lower in the NTG group. The systemic ocular perfusion pressures (OPP), diastolic OPP and mean OPP taken at night were also significantly lower in the NTG group. The differences between the groups were still manifest after controlling for age and presence of hypertension.

CONCLUSION

Our findings show that the nocturnal supine blood pressure parameters (systolic, diastolic and mean) and OPP were significantly lower in the NTG group compared to normals. This may reflect defective autoregulatory mechanisms in NTG patients.

Circadian blood pressure and intraocular pressure patterns in normal tension glaucoma patients with undisturbed sleep

Purpose

To investigate and compare the circadian pattern of blood pressure (BP), intraocular pressure (IOP) and mean ocular perfusion pressure (MOPP) while experiencing undisturbed sleep in normal-tension glaucoma (NTG) and non-glaucoma control patient groups.

Methods

Twenty-four eyes from 24 patients diagnosed with NTG and 22 eyes from 22 control group patients were enrolled. Systolic BP, diastolic BP and IOP were measured every two hours except for the period of time from 1 AM to 7 AM in the NTG group and from 11 PM to 7 AM in the control group over a one-day period. IOP and hemodynamic parameters were then compared between the two groups. NTG patients were subdivided according to the degree of morning BP dip and IOP, and hemodynamic parameters and visual field indices (mean deviation and pattern standard deviation) were also compared among these subgroups.

Results

There were no significant differences in mean systolic BP, mean diastolic BP and mean arterial pressure (MAP) between the NTG and the control groups. The NTG group showed a significantly large morning BP dip compared to the control group (7.1±4.2% vs. 3.8±3.4%, p=0.022). However, there were no significant differences in mean or fluctuation of MOPP between the two groups. Morning over-dippers showed significantly large MAP and MOPP fluctuations compared to non-dippers and dippers, while there were no significant differences in visual field indices among the three subgroups.

Conclusions

NTG patients showed significant morning BP dips compared to the control group. The marked morning BP dip was associated with significantly large MAP or MOPP fluctuations but was not associated with visual field indices.