Research On The Association Among Intraocular Pressure, Intracranial Pressure And Blood Pressure

Objective: As an important parameter, intraocular pressure (IOP) plays a unique role in the area of Ophthalmology. IOP ranges from 11mmHg to 21 mmHg for normal people. Intracranial pressure (ICP) is usually measured as the pressure of cerebrospinal fluid in a standardized lateral decubitus position with the patient's neck and knees bent in full flexion[1]. The reference spectrum of ICP is from 5mmHg to 15mmHg. As two pressures pressing on each side of lamina cribrosa, whose role in the development of glaucomatous damage is being discussed fiercely by specialists, maybe there is an underlying mechanism for IOP and ICP to influent each other or some common factors affecting IOP and ICP at the same time.Recently some researchers have done several studies on the association between IOP and ICP. Some researchers announce that there is no obvious association between IOP and ICP, and IOP isn't a good predictor of ICP. The others claim that IOP can be a very significant predictor of ICP, the two have a very prominent linear correlation, and the abnormal IOP can diagnose abnormal ICP with high sensitivity and specialty. Then what is the real relationship between IOP and ICP?Our research is aimed at testifying the real relationship between IOP and ICP, and answering questions listed below through collecting and analyzing clinical data.1 Does IOP change in a reliable, accurate and predictable way in accordance with ICP? (The relationship between IOP and ICP)2 What is the association among IOP, ICP and MAP (mean arterial pressure)?3 Can IOP be the non-invasive predictor of ICP? What is the diagnostic sensitivity and specialty of high IOP to ICP? Methods:1 The collection of clinical data: After conforming the information of inpatients meeting our inclusion standard, we will collect the clinical data of inpatients, having got lumbar puncture taken, from Neurological Department and Neural Surgery Department between Aug 1st, 2010 and Feb 1st, 2011.1.1 Inclusion criteria of our research:①Without glaucoma family history, vascular disease history such as migraine, or other diseases that can affect IOP;②Without the usage of medicines, which can interfere with the formation of aqueous humor and cerebrospinal fluid, such as inhibitors of carbonic anhydrase andβadrenoreceptor antagonists;③Without deficiencies of respiratory system and circulatory system;④Meet ophthalmic conditions: without halo vision, exclude shallow anterior chamber by side illumination with a light torch,without glaucomatous fundus changes, comparatively normal visual field;⑤The cerebrospinal fluid circulatory pathway must be kept smooth. If an inpatient is diagnosed with intracranial tumor, it must be verified by CT or MRI that the tumor does not obstruct the pathway of cerebrospinal fluid circulation. If it really happens, then this case should be abolished.1.2 Exclusion standard of our research:If corneal conditions of the inpatient make the measurement of IOP impossible, the case will be put aside.If the circulatory path of cerebrospinal fluid is conformed to be blocked by operations or auxiliary tests, the case will be rejected later.2 The measured index: The inpatients'blood pressure of brachial artery and IOP of both eyes should be measured in a supine position after lying peacefully for half an hour just before the lumber puncture. The pressure of cerebrospinal fluid must be measured in a strictly lateral recumber position. 3 Analysis of the collected data: Use SPSS 17.0(SPSS for Windows, version 17.0, SPSS, Chicago, IL) to analyze the collected data. All data is provided in the form of average±standard deviation((x|-)±s). As the indexes were not measured at the same time, we use t-test to test the hypotheses with α=0.05(two tail),β=0.1. If the calculated result indicates p<0.05, we will esteem that the result has statistical significance.If there are linear trends among IOP, ICP and MAP deduced from scatter diagrams, linear correlation and regression analysis will be done successively.Results: Of the enrolled 32 inpatients in this study (age range, 20-74 years, 48.19±14.45), 15 cases (46.88%) were men and 17 cases (53.12%) were women. The ratio of men to women is nearly 1:1. The range of IOP of the subjects is from 8.97 to 28.10 mmHg (17.46±5.74 mmHg), but after deleting the high ICP ones, it is from 8.97 to 15.97 mmHg (11.95±2.36mmHg). ICP ranges from 5.36 to 25.00 mmHg (14.72±5.54mmHg). As for MAP, it is from 72 to 134 mmHg (97.27±14.81 mmHg).It is proved that there are linear trends among IOP, ICP, and MAP by the usage of scatter diagrams, which are attached later in this paper. So the linear correlation and regression analysis between the three parameters is done latterly. The Pearson correlation coefficient between IOP and ICP is 0.902 (p<0.001), and the equation between IOP and ICP can be described as IOP (mmHg) =0.934×ICP (mmHg) + 3.705.The Pearson correlation coefficient between IOP and MAP is 0.668(p<0.01), and the equation between them is IOP (mmHg) =0.259×MAP (mmHg) -7.747. The Pearson correlation coefficient between ICP and MAP is calculated to be 0.705(p<0.01), and the equation between them could be written as ICP (mmHg) =0.264×MAP (mmHg)-10.938.Grouped by the normal ranges of IOP and ICP, the collected clinical cases can be categorized into four groups: The number of inpatients with both high IOP and ICP is 13.One inpatient, recommended to visit ophthalmologists regularly and have his IOP measured periodically, has high IOP but normal ICP. For 16 inpatients the values of IOP and ICP are in the normal ranges. Only two cases characterized as normal IOP but high ICP. Based on the data summarized above, the diagnostic sensitivity, specialty and Youden index of high IOP to ICP are 86.67%, 94.12% and 0.8079 respectively.The patient with high IOP but normal ICP was diagnosed with ocular hypertension by a glaucoma specialist.Conclusions: By analyzing the collected clinical data of 32 inpatients scientifically, we can make some conclusions, which are illuminated in details below.1 There is significant positive linear correlation between IOP and ICP at statistical level.2 The linear correlation exists between IOP and MAP. At the same time, the linear correlation also exists between ICP and MAP.3 Because of its high sensitivity and specialty, IOP can be a reliable predictor of ICP.