[Variations of intraocular pressure during valsalva's maneuver in relation to body position and length of the bulbus in myopia (author's transl)]

Abnormal Systemic and Ocular Responses to the Valsalva Manoeuvre in Primary Open-Angle Glaucoma: A Case for Autonomic Failure?

OBJECTIVE

This study aimed to examine the association of primary open-angle glaucoma (POAG) with autonomic dysfunction by assessing the differences in systemic and ocular responses to an autonomic provocation test, the Valsalva manoeuvre (VM), between POAG patients and normal subjects.

METHODS

Forty POAG and forty control subjects were subjected to the VM. Systemic and ocular parameters were measured at baseline, phase 2, and phase 4 of the VM (VM2 and VM4), where VM2 and VM4 are sympathetic and parasympathetic nervous activation states, respectively. Heart rate variability was used to assess the autonomic nervous activity, among which the high-frequency component (HF) and the low-frequency (LF)/HF ratio were used as indices of parasympathetic and sympathetic activation, respectively.

RESULTS

POAG patients demonstrated higher sympathetic activation (LF/HF ratio median: 2.17 vs. 1.53, P=0.000) than controls at baseline and exhibited attenuated sympathetic and parasympathetic responses (a smaller change in LF/HF and HF values) during the VM than controls. During VM, the intraocular pressure (IOP), mean blood pressure (MAP), mean ocular perfusion pressure (MOPP), and the Schlemm's canal area (SCAR) increased from baseline to VM2 and then decreased from VM2 to VM4 in both the POAG and control groups (all P<0.05). However, when we compared the changes above, the fluctuations in IOP, MAP, and MOPP were more pronounced in POAG than in controls (all P<0.05), while the changes in amplitudes of SCAR were smaller in POAG (P<0.05). Furthermore, from VM2 to VM4, the choroid thickness (ChT) in the POAG group was significantly decreased, while it was unchanged in normal subjects (P=0.258). A regression analysis showed a significant correlation of the baseline LF/HF with IOP change values (ΔIOP) from baseline to VM2 in POAG (R²=0.147, P=0.014).

CONCLUSION

Patients with POAG showed more pronounced fluctuations in IOP, MAP, MOPP and ChT during the VM than controls. These reactions could be associated with autonomic dysfunction in POAG.

Retinal venous pressure is higher than the airway pressure and the intraocular pressure during the Valsalva manoeuvre

PURPOSE

The aims of this prospective experimental study were to explore the influence of the Valsalva manoeuvre (VM) on retinal venous pressure (RVP) in human volunteers in a university setting and to establish correlations for RVP with the increase in airway pressure (∆AirP) and in intraocular pressure (∆IOP).

METHODS

In total, 31 healthy young volunteers (age: 24 ± 1.7 years) were investigated. The instruments used included a dynamic contour tonometer, a contact lens dynamometer (Imedos) and an electronic pressure transducer for measuring airway pressure. The following measurements were successively performed in left eyes: tonometry, dynamometry, repeated simultaneous dynamometry and airway pressure measurement during the VM and tonometry during the VM. The pressures obtained during the VM were determined at 10, 20 and 30 seconds after onset of the VM by linear interpolation.

RESULTS

The pressures (in mmHg) at baseline and during the VM (median and range with outliers) were as follows: ∆AirP: 10 seconds: 10.0 (7.5); 20 seconds: 12.5 (11.0); and 30 seconds: 11.0 (10.0); and RVP: Start: 17.1 (2.4); 10 seconds: 26.0 (7.5); 20 seconds: 25.0 (6.5); and 30 seconds: 24.0 (6.0). During the VM, the RVP was significantly increased compared with the ∆AirP (p = 0.0017). The IOP during the VM was 13.5 (2.7), and the increase in IOP (∆IOP) was 0.8 (5.6).

CONCLUSION

During the VM, the RVP was increased compared with the ∆AirP. The increase in RVP (∆RVP) was significantly greater than the ∆IOP. During the VM, the calculated retinal perfusion pressure may be more strongly reduced by the ∆RVP than by the ∆IOP. These properties may influence retinal and optic nerve head pathophysiology.

Intraocular pressure and glaucoma: Is physical exercise beneficial or a risk?

Intraocular pressure may become elevated with muscle exertion, changes in body position and increased respiratory volumes, especially when Valsalva manoeuver mechanisms are involved. All of these factors may be present during physical exercise, especially if hydration levels are increased. This review examines the evidence for intraocular pressure changes during and after physical exercise. Intraocular pressure elevation may result in a reduction in ocular perfusion pressure with the associated possibility of mechanical and/or ischaemic damage to the optic nerve head. A key consideration is the possibility that, rather than being beneficial for patients who are susceptible to glaucomatous pathology, any intraocular pressure elevation could be detrimental. Lower intraocular pressure after exercise may result from its elevation causing accelerated aqueous outflow during exercise. Also examined is the possibility that people who have lower frailty are more likely to exercise as well as less likely to have or develop glaucoma. Consequently, lower prevalence of glaucoma would be expected among people who exercise. The evidence base for this topic is deficient and would be greatly improved by the availability of tonometry assessment during dynamic exercise, more studies which control for hydration levels, and methods for assessing the potential general health benefits of exercise against any possibility of exacerbated glaucomatous pathology for individual patients who are susceptible to such changes.

Valsalva manoeuver, intra-ocular pressure, cerebrospinal fluid pressure, optic disc topography: Beijing intracranial and intra-ocular pressure study

PURPOSE

To assess whether a Valsalva manoeuver influences intra-ocular pressure (IOP), cerebrospinal fluid pressure (CSF-P) and, by a change in the trans-laminar cribrosa pressure difference, optic nerve head morphology.

METHODS

In the first part of the study, 20 neurological patients (study group 'A') underwent measurement of IOP and lumbar CSF-P measurement in a lying position before and during a Valsalva manoeuver. In the second study part, 20 healthy subjects (study group 'B') underwent ocular tonometry and confocal scanning laser tomography of the optic nerve head before and during a Valsalva manoeuver.

RESULTS

During the Valsalva manoeuver in study group 'A', the increase in CSF-P by 10.5 ± 2.7 mmHg was significantly (p < 0.001) higher than the increase in IOP by 1.9 ± 2.4 mmHg. The change in CSF-P was not significantly (p = 0.61) correlated with the change in IOP. During the Valsalva manoeuver in study group 'B', IOP increased by 4.5 ± 4.2 mmHg and optic cup volume (p < 0.001), cup/disc area ratio (p = 0.02), cup/disc diameter ratio (p = 0.03) and maximum optic cup depth (p = 0.01) significantly decreased, while neuroretinal rim volume (p = 0.005) and mean retinal nerve fibre layer thickness (p = 0.02) significantly increased.

CONCLUSIONS

The Valsalva manoeuver-associated short-term increase in CSF-P was significantly larger than a simultaneous short-term increase in IOP. It led to a Valsalva manoeuver-associated decrease or reversal of the trans-laminar cribrosa pressure difference, which was associated with a change in the three-dimensional optic nerve head morphology: optic cup-related parameters decreased and neuroretinal rim-related parameters enlarged. These findings may be of interest for the pathogenesis of glaucomatous optic neuropathy.

Mechanobiology of trabecular meshwork cells

Trabecular meshwork (TM) cells likely play a key role in regulating outflow facility and hence intraocular pressure. They function in a dynamic environment subjected to variations in mechanical and fluid shear forces. Because the extent of mechanical stress on the trabecular meshwork is dependent on the intraocular pressure, the behavior of TM cells under mechanical strain may suggest mechanisms for how outflow facility is regulated. Studies have demonstrated that TM cells respond in a variety of ways to mechanical loads, including increased extracellular matrix turnover, altered gene expression, cytokine release, and altered signal transduction. This review highlights some of the considerations and limitations of studying the mechanobiology of TM cells.

The effect of simulated obstructive apnoea on intraocular pressure and pulsatile ocular blood flow in healthy young adults

AIM

To investigate the effect of negative inspiratory effort, as generated by the Mueller manoeuvre, on intraocular pressure (IOP) and pulsatile ocular blood flow (POBF) in healthy young adults.

METHODS

Seven volunteers with no history of systemic or ocular disease were recruited (mean age 30.7 years, range 25-40 years, M/F: 4/3). After initial instruction and practice of the Mueller manoeuvre, baseline measurements of IOP and POBF were obtained for both eyes after 10 and 15 minutes of rest, respectively, in the supine position. Thereafter, the Mueller manoeuvre was performed creating a mouthpiece pressure of -20 cm H(2)O, for at least 15 seconds followed by a 5 minute rest. The manoeuvre was repeated with a mouthpiece pressure of -40 cm H(2)O. IOP and POBF were measured 5-15 seconds into the manoeuvre for both -20 cm H(2)O (M2A) and -40 cm H(2)O (M4A) and directly upon recovery (after two respiratory cycles) from each manoeuvre (M2B, M4B). Baseline measurements were compared using paired t test, whereas manoeuvre induced changes in IOP and POBF were analysed individually using repeated measures ANOVA with Student-Newman Keuls post hoc analyses. Linear regression analysis was used to investigate a dose-response effect.

RESULTS

No significant differences were found between baseline measurements so they were subsequently pooled. There was a significant decrease in IOP for M2B (-9.2%, p<0.05), M4A (-13.8%, p<0.05), and M4B (-15.6%, p<0.05), relative to baseline. A dose-response relation was found for the effect of mouthpiece pressure on measurements 5-10 seconds into the manoeuvre (M2A and M4A, r = 0.54, p = 0.045). There was a trend of increased POBF relative to baseline for all measurements; however, significance was reached for M4B only (p = 0.039).

CONCLUSION

It was shown that forced inspiratory efforts as generated by the Mueller manoeuvre are associated with a dose dependent decrease in IOP and a concomitant increase in pulsatile ocular blood flow.

Sources of error with use of Goldmann-type tonometers

There are many sources of error in the use of Goldmann-type applanation tonometers. In clinically normal corneas hypofluorescence of the precorneal tear film, accommodation, the Valsalva maneuver and vertical gaze are preventable causes of large tonometric errors. Repeated tonometry may induce a decline in the intraocular pressure (IOP). Variations in the corneal resistance to indentation between eyes cause significant errors. The most significant cause of error in clinically abnormal eyes is corneal epithelial edema, which causes a marked underestimation of IOP. Measurements obtained with Goldmann-type tonometers can be used with confidence to monitor changes in the IOP of an individual, but should not be relied on to determine the absolute manometric pressure within an eye or to compare the IOPs in eyes of different individuals.

Respiratory and circulatory influence on photopapillometry

Respiratory and circulatory conditions that could have an influence on measurements of pallor of the papilla were evaluated with our photopapillometer in a controlled study on canines. The brightness of the papilla rim and the width of the arterioles emerging from the optic nerve head were measured in six anesthetized dogs under normal, hypertensive, and hypotensive circulatory conditions, as well as under various respiratory manipulations, and the parameters were compared for statistical correlation. Both brightness and vessel width remained constant for a wide range of arterial pressures when the rest of the experimental conditions were kept stable at naturally occurring levels. If respiration and circulation were brought to extreme levels, however, there was a statistical tendency for the brightness of the papilla to be dependent on arterial and pulmonary arterial blood pressure. The importance of these findings is discussed with regard to their influence on objective measurements of fundus brightness.