Abstract:
Non-tactile and non-evasive tonometer utilizing air flow with a definite amount of pressure to the eye and a mechanism to deflate the thin foil set that is placed near to eye ball such that re-bounded air hits on it. The mechanism involves acquiring or capturing then the images of the known pattern marking on thin foils both before and after deflating process due to rebounded air. On evaluating the deformation of the pattern appearing in the images obtained before and after air flow and calibrating the deformation with respect to size, translation, rotation and scaling parameters due the different pressure level that hits the eye ball and that rebounds on to thin foils, we arrive at a scheme of measuring the intraocular pressure of human eye. This intraocular pressure is used as a parameter for the ophthalmologist to diagnose glaucoma impairment of human beings.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 371 U.S. National Stage of International Application No. PCT/IB2012/054134, filed Aug. 14, 2012, and claims priority to Indian Patent Application No. 2831/CHE/2011, filed Aug. 18, 2011, the disclosures of which are herein incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to a medical device. More particularly, embodiments relates to a method and a system for determining Intraocular Pressure (IOP) of an eye. 
     BACKGROUND 
     There are few non-contact and non-evasive Tonometers that utilize angle modulation of high frequency sound waves or light waves to determine the Intraocular Pressure (IOP) of a human eye using either frequency or phase modulation. 
     One of the limitations of aforementioned approaches is that the Intraocular Pressure parameter is intended to diagnose Glaucoma impairment but this need to be used in conjunction with other observations. Some of the other observations involved are based on image analysis of optic nerve head and retinal nerve fibre loss in the retinal portion of the eye. On this context, it is preferable to integrate these measurements into single device in order to avoid usage of multiple devices. As indicated earlier the Tonometer exploits either sound or light waves which demands different sources and measuring techniques, whereas, an imaging requires other type of sources and components. This leads to not only in increased bill of materials for the device but also to aid making device more portable. 
     Hence, there exists need to provide a system to integrate all measurement in a single device to reduce bill of materials for the device. Also, eliminate different sources and measuring techniques to measure IOP. 
     SUMMARY 
     The shortcomings of the prior art are overcome through the provision of a method and a system as described in the description. 
     Accordingly, the present disclosure relates to a method to identify Intraocular Pressure (IOP) of an eye by blowing air onto an eye ball of the eye. The method comprises of placing a foil-flap support assembly between an imaging unit and the eye, wherein the foil-flap support assembly has a transparent stiff foil fixed to a support and plurality of movable flaps facing the eye is suspended from the support. Once the foil-flap support assembly is placed, air of predetermined amount of pressure is blown onto an eye ball of the eye through an air channel, wherein the air blown to the eye ball rebounds from the eye ball deflating the flaps of the foil-flap support assembly. At this stage an image of the deflated foil-flap support assembly is captured and plurality of parameters value of the captured image is calculated. Now, the calculated plurality of parameters value is compared with plurality of predetermined parameters value to identify IOP of the eye. 
     A system to identify IOP of the eye is disclosed as another aspect of the present disclosure. The system comprises a foil-flap support assembly and a control unit. The foil-flop support assembly comprises a transparent stiff foil fixed to a support and plurality of movable flaps facing the eye is suspended from the support. The control unit comprises an imaging unit, a computing unit, a storage unit and a blowing unit. The blowing unit comprising an air channel is used to blow air of predetermined amount of pressure onto an eye ball of the eye. Thus, the blown air gets rebound deflating the flaps of the foil-flap support assembly. The imaging unit is used to capture image of the foil-flap support assembly before and after deflation of the flaps. The computing device is configured to identify plurality of parameters value of the captured image and to compare the identified parameters value with a predetermined parameters value to identify IOP of the eye. The predetermined parameters value is determined during a calibration. A storage unit is configured in the control unit to store the calibrated predetermined parameters value. 
     The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the present disclosure are set forth with particularity in the appended claims. The disclosure itself, together with further features and attended advantages, will become apparent from consideration of the following detailed description, taken in conjunction with the accompanying drawings. One or more embodiments of the present disclosure are now described, by way of example only, with reference to the accompanied drawings wherein like reference numerals represent like elements and in which: 
         FIG. 1A  shows an exemplary system to identify IOP of the eye according to an embodiment of the present disclosure. 
         FIG. 1B  shows arrangement of various components of an assembly according to an embodiment of the present disclosure. 
         FIG. 2A  illustrates an exemplary logical steps used to identify Intraocular Pressure (IOP) of an eye according to an embodiment of present disclosure. 
         FIG. 2B  is an exemplary image illustrating deflation of flaps according to an embodiment of the present disclosure. 
         FIG. 3A  shows an outwardly bulged lens surface of the eye when IOP is high according to an embodiment of the present disclosure. 
         FIG. 3B  shows a flat or inwardly dented lens surface of the eye when IOP is low according to an embodiment of the present disclosure. 
         FIG. 4A  illustrates an exemplary sequence of steps used for performing a calibration to determine predetermined parameters value from a normal eye according to an embodiment of the present disclosure. 
         FIG. 4B  is an image of the foil-flap support assembly before blowing the air in calibration according to an embodiment of the present disclosure. 
         FIG. 4C  is the image of the deflated flaps corresponding to varied amount of air pressure during calibration according to an embodiment of the present disclosure. 
         FIGS. 5A and 5B  shows a relationship curves between varying amounts of air pressure P o  and change in length Δ l  and change in breadth Δ b  respectively according to an embodiment of the present disclosure. 
     
    
    
     The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein. 
     DETAILED DESCRIPTION 
     The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the claims of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the disclosure as set forth in the appended claims. The novel features which are believed to be characteristic of the disclosure, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure. 
     The present disclosure relates to a method to identify Intraocular Pressure (IOP) of an eye by blowing air onto an eye ball of the eye. The method comprises of placing a foil-flap support assembly between an imaging unit and the eye, wherein the foil-flap support assembly has a transparent stiff foil fixed to a support and plurality of movable flaps facing the eye is suspended from the support. Once the foil-flap support assembly is placed, air of predetermined amount of pressure, which is in the range of 10 millimeter of Mercury (10 mmHg) to 100 millimeter of Mercury (100 mmHg), is blown onto an eye ball of the eye through an air channel. The blown air hits the eye ball. The blown air rebounds from the eye ball deflating the flaps of the foil-flap support assembly. At this stage an image of the deflated foil-flap support assembly is captured and plurality of parameters value of the captured image is calculated. The plurality of parameters value of the is selected from at least one of size, length, breadth, width, shape, lateral shifts, rotation, translation, scaling or any combinations thereof. Now, the calculated parameters value is compared with plurality of predetermined parameters value to identify IOP of the eye. 
     The predetermined parameters value is determined from a normal eye by performing a calibration comprising steps of placing the foil-flap support assembly between the eye and the camera. At this stage, an image of the foil-flap support assembly is captured. The plurality of parameters value of the captured image is calculated. Now, air of the predetermined amount of pressure is blown onto an eye ball of the normal eye through the air channel. The air blown hits the eye ball and gets rebound from the eye ball which deflates the foil-flap support assembly. Now, the image of the deflated flaps of the foil-flap support assembly is captured. From the captured image, the plurality of parameters value of the deflated flaps is calculated. The calculated parameters value is stored. Later, the amounts of air pressure are varied and are blown to the eye ball of the normal eye. The images of the deflated flaps corresponding to varied amounts of air pressure are captured. The parameters value is calculated for each captured images and is stored. 
     A system to identify IOP of the eye is disclosed as another aspect of the present disclosure. The system comprises a foil-flap support assembly and a control unit. The foil-flop support assembly comprises a transparent stiff foil fixed to a support and plurality of movable flaps facing the eye is flexibly suspended from the support. The transparent stiff foil and the plurality of movable flaps have a thickness in the range of 0.1 millimeter to 5.0 millimeter. Also, they have a predefined color or prerequisite pattern different from one another. The control unit comprises a blowing unit, a camera, a computing device and a storage unit. The air channel selected from at least one of a transparent tube and a non-transparent tube. The transparent tube is selected from at least one of a glass tube, plastic tube and rubber tube. The non-transparent tube is selected from at least one of plastic tube, rubber tube and metallic tube. The air channel is used to blow air of predetermined amount of pressure onto an eye ball of the eye. The air channel is placed at a distance of 30 millimeter to 40 millimeter from the eye. The blown air hits the eye ball and gets rebound from the eye ball deflating the flaps of the foil-flap support assembly. The control unit also includes an imaging unit used to capture image of the foil-flap support assembly before and after deflation of the flaps. The computing device is configured to identify plurality of parameters value of the captured image and to compare the identified parameters value with a predetermined parameters value to identify IOP of the eye. The predetermined parameters value is determined during a calibration. The storage unit is configured in the control unit to store the calibrated predetermined parameters value. 
       FIG. 1A  shows a system to identify IOP of the eye according to an embodiment of the present disclosure. The system has a foil-flap support assembly  112  and a control unit  102 . The foil-flap assembly have a transparent stiff foil  118  fixed to a support  114  and plurality of movable flaps  116  facing an eye is flexibly suspended from the support  114 . The transparent stiff foil  118  and the plurality of movable flaps  116  have a thickness in the range of 0.1 millimeter to 5.0 millimeter. Also, the transparent stiff foil  118  and the plurality of movable flaps  116  have a predefined color or prerequisite pattern different from one another. The control unit  102  comprises a blowing unit  110 , a imaging unit  106 , a computing unit  104  and a storage unit  108 . The blowing unit  110  has an air channel  120  to blow air of predetermined amount of pressure onto an eye ball  122  of the eye. The air channel  120  is placed such a way that it impinges air on the eye ball  122  and do not block rebound air that deflates the suspended flaps  116 . In an embodiment, the air channel  120  comprises a nozzle with one or more openings. The opening of the air channel  120  can be of any shape including but not limited to circle, oval etc. In an exemplary embodiment, one or more sensors can be placed between or around the opening to measure the reflected air pressure. The imaging unit  106  is used to capture image of the foil-flap support assembly  112  before (in calibration) and after deflation. The computing device  104  is configured to identify plurality of parameters value of the captured image and to compare the identified parameters value with a predetermined parameters value which is determined during a calibration to identify IOP of the eye. The storage unit  108  is used to store calibrated parameters value. 
       FIG. 1B  shows arrangement of various components of an assembly  112  according to an embodiment of the present disclosure. A black or any specific colored definite fringe pattern on the transparent material labelled  118  is rigidly fixed to the support  114 . Further, two or more flaps  116  with another definite fringe pattern like moiré pattern or any other definite pattern is flexibly suspended from the support  114  that gets deflated as rebound air hits on them. This assembly  112  is placed between the imaging unit  106  and the eye such that the images of the combined fringe pattern can be captured without air puffing and while is puffed. As the rebound air falls on the suspended flaps  116  could either moved laterally apart from each other or could be made moved front to back direction. Both the described movements will change the parameters value such as breadth, length and lateral shifts. This change in parameters value is directly proportional to rebound air pressure. 
       FIG. 2A  illustrates a method to identify Intraocular Pressure (IOP) of an eye according to an embodiment of present disclosure. The method comprises acts of placing a foil-flap support assembly  112  between the eye and a imaging unit  106  at step  202 , wherein the foil-flap support assembly has a transparent stiff foil  118  fixed to a support  114  and plurality of movable flaps  116  facing the eye is suspended from the support  114 . At step  204  the air of predetermined amount of pressure i.e. of 20 millimeter of Mercury (20 mmHg) is blown onto an eye ball  122  of the eye through an air channel  120 . The air blown to the eye ball  122  gets rebound from the eye ball  122  deflating the flaps  116  of the assembly  112 . At step  206  an image of the deflated flaps  116  of the foil-flap support assembly  112  is captured by the imaging unit  106 . The plurality of parameters value of the captured image is identified at step  208  by a computing unit  104 . For example, in  FIG. 2B , the length of the deflated flaps is labelled as l e  and breadth of the flaps labelled as b e  are identified at step  208 . At step  110 , the identified parameters value is compared with plurality of predetermined parameters value to identify IOP of the eye. 
       FIG. 3A  shows an outwardly bulged lens surface of the eye ball  122  when IOP is high according to an embodiment of the present disclosure. If the IOP is high, then the internal surface pressure is high that makes the lens surface bulged and inflexible or stiff as shown in  FIG. 3A . When the air of 20 mmHg is blown on such surface, the air is outwardly rebounded from the eye ball  122  is less that depends on a surface curvature of the lens surface of the eye ball  122  of the eye which is usually bulged as shown. This makes the flexible flaps  116  to get less deflated and consequently there will be less change in parameters values. 
       FIG. 3B  shows a flat or inwardly dented lens surface of the eye ball  122  when IOP is low according to an embodiment of the present disclosure. When the air at pressure of 20 mmHg is blown to the lens of the eye ball  122  having little or low IOP, the lens surface is flexible enough that allows external corneal surface of lens to become flat or dented inside. Further, the rebound air pressure is oriented in the direction of the flaps  116  would be more as shown in  FIG. 3B . 
       FIG. 4A  illustrates a method of performing a calibration to determine predetermined parameters value from a normal eye according to an embodiment of the present disclosure. A foil-flap support assembly  112  is placed between the eye and the imaging unit  106  at step  402 . At step  404 , an image of the foil-flap support assembly  112  before the air is blown is captured using the imaging unit  106 . The parameters values of the flaps  116  i.e. l and b as shown in  FIG. 4B  which are the length and breadth of the flaps before air is blown are identified at step  406 . At step  408 , air of ‘K’ mmHg amount of pressure is blown onto the eye ball  122 . This causes the flaps  116  to get deflated since air blown gets rebound from the eye ball  122 . The imaging unit  106  captures the image of the deflated flaps at step  410 . The computing unit  104  identifies image parameters value of the deflated flaps  116  at step  412  i.e. l 2  and b 2  which are the length and breadth of the deflated flaps as shown in  FIG. 4C . The storage unit  108  stores identified parameters value performed at step  414 . The amounts of air pressure are varied and are blown to the eye ball  122  of the normal eye. The images of the deflated flaps  116  corresponding to varied amounts of air pressure are captured. The parameters value is calculated for each captured images and is stored in a storage unit  108 . 
       FIG. 5A  is a relationship curve obtained during calibration between varying amounts of air pressure P o  and change in length Δ l  according to an embodiment of the present disclosure. Here, the change in length is obtained by computing:
         Δ l =l−l 2  where Δ l  is the change in length corresponding to varied amount of air pressure P o .       

       FIG. 5B  is the relationship curve obtained during calibration between varying amounts of air pressure P o  and change in breadth Δ b  according to an embodiment of the present disclosure. Here, the change in breadth is obtained by computing:
         Δ b =b−b 2  where Δ b  is the change in breadth corresponding to varied amounts of air pressure P o .       

     Additional features and advantages are realized through various techniques provided in the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered as part of the claimed disclosure. 
     The present disclosure addresses a problem of integrating the Tonometer and Retina imaging into single device by making use of common resources and components. 
     The image analysis based intraocular pressure measurements facilitate in utilizing the resources optimally that aid in reducing cost and making device more portable. 
     Further, the proposed disclosure is a non-contact and non-evasive indirect approach, which is based on image analysis and the intraocular pressure determination explored based on prior calibration. 
     The intraocular pressure measured using the method disclosed in the present disclosure is used as a parameter by the ophthalmologist to diagnose glaucoma impairment of human beings. 
     
       
         
               
               
             
           
               
                   
               
               
                 Reference Numeral 
                 Description 
               
               
                   
               
             
             
               
                 102 
                 Control Unit 
               
               
                 104 
                 Computing Unit 
               
               
                 106 
                 Imaging Unit 
               
               
                 108 
                 Storage Unit 
               
               
                 110 
                 Blowing Unit 
               
               
                 112 
                 Foil-flap Support Assembly 
               
               
                 114 
                 Support 
               
               
                 116 
                 Movable Flaps 
               
               
                 118 
                 Transparent Foil 
               
               
                 120 
                 Air Channel 
               
               
                 122 
                 Eye ball