Intra-ocular pressure changes during maximal isometric contraction: Does this reflect intra-cranial pressure or retinal venous pressure?

Abstract

Recent publications have suggested that intra-ocular pressure (IOP) may be an indirect assessment of intra-cranial pressure (ICP). Both IOP and ICP have similar physiologic pressure ranges and similar responses to changes in intra-abdominal, intra-thoracic and aortic pressure. Previous studies have demonstrated the relationships between retinal arterial pressure and aortic pressure, intra-ocular pressure and retinal venous pressure, intra-cranial pressure and retinal venous pressure. Power athletes routinely utilize the Valsalva maneuver during weightlifting. In fact there are reports of stroke, cerebral hemorrhage, subarachnoid hemorrhage, conjunctival, foveal and retinal hemorrhage, retinal detachment, hiatal hernia and pneumothorax associated with weightlifting. These events are thought to occur secondary to the extreme pressure elevations that occur in the intra-abdominal, intra-thoracic, intra-cranial, intra-ocular and vascular compartments. To date no human studies have examined the IOP changes that may occur with heavy resistance exercise. Therefore, we recruited power athletes (n = 11), who had participated in prior studies, from the local metropolitan area. The athletes had blood pressure status, drug screening and medical histories performed during previous investigations. Intra-ocular pressure was measured by noncontact tonometry at rest and during maximal isometric contraction. All subjects resting IOP were within normal ranges (mean 13 +/- 2.8 mmHg). Intra-ocular pressures were significantly (p < 0.0001) elevated in each subject during maximal contraction (mean 28 +/- 9.3 mmHg). One subject's IOP reached 46 mmHg during maximal contraction. Linear regression analysis demonstrated a significant linear relationship (r = 0.62, p < 0.0001) in the net change of IOP from rest to maximal contraction for each subject. This study demonstrates that IOP elevates to pathophysiologic levels during resistance exercise. The findings of conjunctival hemorrhages in two subjects further supports IOP being reflective of retinal venous pressure. The enormous pressures generated by power athletes during weightlifting leads to elevations in ICP which obstruct venous outflow leading to hemorrhage and elevations in IOP. The question remains as to whether these intermittent bursts of elevated IOP can lead to long-term pathological sequelae.

Noninvasive Measurement of Intracranial Pressure: Is It Possible?

“…The method of measuring the central retinal vein pressure is called the ophthalmodynamometry. 14 There are also publications claiming no correlation between IOP and ICP. Hayreh 15 indicates that only an acute ICP increase of more than 50 mm Hg may cause significant increase of IOP.…”

Does an iridotomy provide protection against narrowing of the anterior chamber angle during Valsalva maneuvre in eyes with primary angle closure

“…There have been a few studies on the IOP changes induced by a Valsalva maneuvre. [3][4][5][6] The UBM changes in the anterior chamber and anterior chamber angle recess during the Valsalva maneuvre were studied earlier, and showed a significant degree of narrowing of the angle with elevation of IOP during this maneuvre. 7 In the present study, we studied PAC eyes, and found a rise of IOP, and a narrowing of the anterior chamber angle occurring despite the presence of a patent Nd:YAG iridotomy.…”

“…[1][2][3][4][5][6] Although the effect of the Valsalva maneuver on intraocular pressure (IOP) in the normal population and a few glaucomatous eyes has been documented, [3][4][5][6] its effect on the anterior chamber angle using ultrasound biomicroscopy was recently evaluated, and a significant narrowing of the angle recess was documented. 7 This cross-sectional study was designed to evaluate the protective efficacy of a laser iridotomy on the effect produced by the Valsalva manoeuver in eyes with primary angle closure (PAC), using ultrasound biomicroscopy (UBM).…”

Anatomic Evidence for Information Exchange between Primary Afferent Sensory Neurons Innervating the Anterior Eye Chamber and the Dura Mater in Rat

“…3 The response to changes in posture and intra-abdominal or intrathoracic pressure are similar. 36 Both aqueous fluid and CSF are produced by carbonic anhydrase-catalyzed reactions, and the chemical composition of these fluids is almost the same, with more proteins and less ascorbates in CSF. 3 Chemical stimulation of neurons in the DMH/PeF region evoked increases in both of these fluids.…”