PubMed · 6026596
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U Majzoub. 1967. Volume changes in indentation tonometry.. https://doi.org/10.1136/bjo.51.6.365
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Hemodialysis, a useful treatment for patients with severely compromised renal function, has also unfavorable side effects. In the ophthalmologic area, a rise in intraocular pressure (IOP) during dialysis accompanied by ocular pain has been reported. In our study when measuring IOP, as well as serum osmolality and plasma CO2 pressure every 30 minutes during routine hemodialysis in renal failure patients with a normal aqueous outflow facility, the mean percent changes of IOP to the initial value showed no significant difference at any time, although the changes in serum osmolality decreased significantly. The mean percent changes of plasma CO2 pressure also did not show any significant difference during dialysis. In patients with a poor aqueous outflow facility, the mean percent changes of IOP increased significantly after 90 minutes, with the exception of the change at 180 minutes. The mean percent changes of serum osmolality decreased significantly after starting dialysis. A negative correlation in the mean percent change of IOP with that of serum osmolality was detected. The administration of an intravenous hyperosmotic agent prevented significant changes not only in serum osmolality but also in IOP. Therefore, it is considered that hemodialysis causes a decrease in serum osmolality, resulting in an osmotic gradient between the plasma and the intraocular fluids due to the presence of the blood-ocular barrier. Although the osmotic gradient draws water from the plasma into the eye, if there is no abnormal obstruction in the aqueous outflow pathway, an amount of aqueous humor matching the increase in intraocular fluid goes through the pathway out of the eye to maintain the normal level of IOP. In eyes with an obstructed aqueous outflow pathway, however, this compensatory mechanism of aqueous humor drainage does not work well, and results in an IOP elevation.
PURPOSE: To determine the relationship between saccadic eye movements and the development of early postoperative capsular block syndrome. SETTING: Fundacion Oftalmologica, Los Andes, Santiago, Chile. METHODS: An artificial experimental setup was designed to reproduce the anatomical, hydrodynamic, and kinetic conditions of an early postoperative pseudophakic eye with a capsulorhexis and intracapsular intraocular lens (IOL) implantation. An electromechanical transducer driven by a digital-to-analog converter was used to mimic saccadic eye movements at physiological speeds and accelerations. Position information and differential pressure measurements between the intracapsular space and the extracapsular space were digitized. Various anterior capsule-IOL configurations were tested including partial adhesion of the anterior capsule to the lens. RESULTS: Saccadic movements increased intracapsular pressure by displacing fluid into the capsular bag. This finding was inconstant and only observed when the capsular rim adhered to the IOL optic by more than 70%. Development of positive intracapsular pressure was noted above 4 mm Hg. CONCLUSION: A valve-like mechanism formed by the capsulorhexis rim partially adhered to the IOL optic can occur postoperatively. Under these conditions, saccadic eye movements can increase intracapsular pressure by a unidirectional inertial displacement of fluid into the capsular bag.
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