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Steven Katz, Ashraf Mahmoud, Monica Okon, Keerthana Bolisetty, Robert Small, Cynthia Roberts; Changes in Intracranial Pressure (ICP) and Ocular Pulse Amplitude (OPA) in Patients with Idiopathic Intracranial Hypertension (IIH). Invest. Ophthalmol. Vis. Sci. 2013;54(15):4367.
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Ocular Pulse Amplitude (OPA) has been shown to be affected by both ocular biomechanics and ocular blood flow.1 The hypothesis to be tested is that it is also affected by intracranial pressure (ICP). Therefore, the purpose of this preliminary study was to evaluate the response of OPA in subjects diagnosed and subsequently treated for Idiopathic Intracranial Hypertension (IIH) with presenting elevated cerebral spinal fluid (CSF) opening pressure (OP) determined by lumbar puncture, followed by treatment.
A total of 10 right eyes of 10 subjects were prospectively enrolled with increased ICP. In addition to the standard work-up for IIH, PASCAL Dynamic Contour Tonometry (DCT) was performed with custom software to digitally record the ocular pulse signal, provided by the manufacturer (Ziemer Ophthalmic Systems AG, Port, Switzerland). Systemic blood pressure was also acquired, with systolic, diastolic and difference of the two which is pulse pressure (pp). CSF opening pressure was determined via lumbar puncture. Treatment consisted of shunt, Diamox, Lasix, or Topamax, followed by a second DCT measurement after treatment. Intraocular pressure (IOP), OPA, IOP/OPA, and PP were compared before and after treatment with a student t-test.
The mean values of IOP and OPA were 18.6±1.7mmHg, 2.3±0.7mmHg on presentation, and 17.1+2.9mmHg, 1.8±0.5mmHg after treatment, respectively. Both IOP (p=0.05) and OPA (p<0.03) were significantly reduced after treatment, and IOP/OPA showed a significant change (p = 0.05). There was no difference in systemic pulse pressure (p=0.28). In one subject who received a shunt, IOP increased while OPA decreased.
A decrease in OPA is consistent with a decrease in IOP. However, the significant change in the IOP/OPA ratio is consistent with a decrease in intracranial pressure. Changes in ICP may be reflected in the OPA. Future work will involve developing a model for interpretation, since OPA is affected by IOP, PP, and now ICP. 1Perkins, E. S., The Ocular Pulse. Current Eye Research, 1981. 1(1): 19-23.
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