Method and Apparatus for Detecting Possible Arterial Constriction by Examining an Eye

Abstract

A tonometer capable of measuring systolic or ocular pulse pressure (OPP) can be used to examine eyes of a patient to measure whether OPP or ocular blood flow (OBF) is sub-normal to one or both eyes. This can serve as an indication of a possible constriction of blood flow in arteries leading not only to the eyes, but to the brain and other regions above the neck. Any such sub-normal measure can then indicate that further investigation of blood flow in carotid and other arteries is appropriate.

1 . A method of detecting possible constriction of blood flow in arteries supplying a head, the method comprising: 
 examining an eye of the head with an applanation tonometer producing intra ocular pressure signals representing a diastolic phase signal and a departure from the diastolic phase signal occurring as a systolic pulse of blood enters the eye;    determining blood flow to the eye from the systolic phase signal; and    determining from the detected blood flow to the eye whether blood flow constriction in arteries supplying the head may be occurring.    
   
   
       2 . The method of  claim 1  including measuring blood flow to each of two eyes of the head to determine whether blood flow is significantly less in one of the eyes as an indication of where a possible blood flow constriction may be occurring.  
   
   
       3 . The method of  claim 1  including subsequently measuring blood flow in a carotid artery leading to an eye with a subnormal blood flow to determine whether blood flow is constricted in the carotid artery.  
   
   
       4 . The method of  claim 1  including programming the tonometer to distinguish between and to indicate normal and abnormal blood flow to the eye.  
   
   
       5 . A tonometer operated by the method of  claim 1 .  
   
   
       6 . A method of predicting possible cardiovascular events, the method comprising: 
 examining an eye of a patient with an applanation tonometer to measure a systolic pulse of blood to the eye;    determining an ocular pulse pressure (OPP) or ocular blood flow (OBF) from the systolic pulse to the eye; and    determining whether either OPP or OBF is subnormal as an indication of possible constriction of a carotid artery leading to the eye.    
   
   
       7 . The method of  claim 6  including programming the tonometer to distinguish between and to indicate normal and subnormal OPP and OBF.  
   
   
       8 . The method of  claim 6  including examining each eye of a patient with the applanation tonometer, comparing OPP and OBF for each of the examined eyes, and determining from the comparison whether one of the eyes has a lower OPP or OBF than the other.  
   
   
       9 . The method of  claim 6  including examining blood flow in a carotid artery leading to an eye having a subnormal OPP or OBF.  
   
   
       10 . A tonometer operated by the method of  claim 6 .  
   
   
       11 . The method of  claim 10  wherein the tonometer includes a microprocessor programmed to distinguish between and to indicate normal and subnormal OPP or OBF.  
   
   
       12 . A test for possible constriction of blood flow in a carotid artery preliminary to a carotid artery ultrasound examination, the test comprising: 
 examining each eye of a patient with an applanation tonometer that produces a systolic pulse signal as a bolus of blood enters an eye being examined;    determining ocular pulse pressure (OPP) or ocular blood flow (OBF) for each eye from the systolic pulse signals; and    determining to proceed with a carotid artery ultrasound examination whenever the OPP or OBF determination for either eye is subnormal.    
   
   
       13 . The test of  claim 12  including determining not to proceed with a carotid artery ultrasound examination whenever the OPP and OBF are normal.  
   
   
       14 . A tonometer arranged to perform the test of  claim 12.