various aspects of the present invention will evolve from the following detailed description of the preferred embodiments of the present invention which should be referenced to the prior described drawings . the invention as a whole is shown in the drawings reference character 10 . the device 10 for detecting the condition known as keratoconjunctivitis sicca ( kcs ) may be described as a tear conductance osmometer , details of which will be described hereinafter . device 10 includes as one of its elements a probe 12 , fig1 having a body 14 with an end portion section 16 . body 14 may be constructed of any rigid or semi - rigid material such as plastic , metal , ceramic compositions and the like . as depicted in fig1 body 14 is formed of a non - conducting material such as plastic . a handle 18 is further depicted in fig1 and 5 as being angularly disposed relative to end portion 16 . handle 18 may also be formed in axial alignment with end portion 16 as depicted by handle 18a , shown in phantom on fig1 . either handle 18 or 18a may include a knurled , contoured gripping surface . in addition , probe body 14 may take the form of a contact lens without handle 18 . the device 10 also includes a plurality of electrical contacts 20 , fig1 - 4 , mounted in spaced configuration . as shown in fig1 electrical contacts 22 , 24 and 26 are fixed in end portion 16 , but have a convex surface that extends beyond non - conducting end surface 28 of end portion 16 . it is intended that plurality of electrical contacts simultaneously communicate with or touch tear fluid or film 30 which coats conjunctiva 32 . a plurality of conductors or wires 34 lead from plurality of contacts 20 to conductance meter 36 , depicted in block form on fig5 and 6 . it should be noted that plurality of contacts 20 shown in fig1 are wedged into recess 38 molded into end portion 16 of probe body 14 . sheath 40 mechanically encompasses plurality of conductors 34 . contacts 20 may be constructed of any high conductance , low corroding material such as gold , platinum , stainless steel and the like . turning to fig2 - 4 , several patterns of plurality of electrical contacts 20 are illustrated . in fig2 contacts 22 , 26 , 42 , 44 , 46 , and 48 are arranged in a regular hexagonal pattern ; contact 24 serving as the center of such pattern . thus , contact 24 is equidistant from any of the other contacts serving to define the periphery of a hexagon . it should also be observed , that any peripheral contact would be equidistant from three other contacts . with reference to fig3 plurality of contacts 20a may take the form of conductive strips 50 and 52 surrounded by multiplicity of peripheral contacts 54 . non - conducting end surface 56 would take the shape of a rectangle having rounded corners . fig4 utilizes a ring contact 58 surrounded by multiplicity of peripheral contacts 60 . concentric rings or bands such as ring 58 may also be employed . non - conducting end surface 62 thereof is circular as is end surface 28 shown in the embodiments depicted in fig1 and 2 . for example , the overall diameter of end surface 28 would range between ( 7 ) and ( 12 ) millimeters with a typical spacing between contacts being ( 2 ) millimeters . it should be mentioned that end surfaces such as end surfaces 28 , 56 and 60 may take a variety of shapes to accommodate the eyelid fissure and the layout of electrodes 20 . in this regard , end surface 28 , is concave to a degree necessary to conform to the outer surface 64 of ocular conjunctiva 32 . it is anticipated that surfaces 56 and 62 , fig3 and 4 would also be concave to generally conform to the outer surface 64 of conjunctiva 32 . turning to fig7 a probe end 66 of a different embodiment is depicted . probe end 66 includes a porous membrane 68 which is ion selective i . e . permitting only a certain ion or ions to pass therethrough i . e . sodium , potassium , chloride , calcium , and the like . membrane end surface 69 , generally conforms to the surface 64 of conjunctiva 32 , although only good contact with fluid 30 is required . the equilibruim ionic activity of a particular ion in chamber 74 may be measured quickly and accurately by more than one method . for example , the chloride ion is measured against an internal reference electrode by a portable meter external to the electrode . also , sodium ion activity is determined at a contacted liquid surface by the potential it generates in reacting with a &# 34 ; solid &# 34 ; calibrated ion selective membrane . it should also be noted that membrane 68 may take the form of a simple ion selective electrode prior described , without chamber 74 . with reference to fig6 it may be seen that means 76 , in the form of a 0 . 1 - 10 volt dc power supply is employed for providing an electrical potential to one of the plurality of the contacts 20 . such potential may be electronically pulsed , eg : 50 - 1000 hz . in the embodiment shown , double throw switch 78 may be used to place a potential on contact 24 , as depicted . in such a case contacts 22 , 42 , 44 , 26 , 46 , and 48 would receive any electrical current traveling through tear fluid 30 when probe 12 is placed in such fluid 30 enveloping the conjunctiva 32 of eye or eyeball 80 , fig5 . however , activating electrical leg 82 by throwing switch 78 to contact 84 activates contact 22 , a peripheral contact in the embodiment depicted in fig2 . in such a case , switches associated with contacts 24 , 42 and 48 of plurality of switches 86 , would also be closed . it is to be noted that switch 88 associated with contact 24 would be simultaneously closed with the closing of switch 78 onto contact 84 . in other words , a relay would suffice as a substitute for switches 78 and 88 in this regard . leg 90 represents a multiplicity of conductors , originating with each of the plurality of switches 86 associated with contacts 22 , 42 , 44 , 26 , 46 , and 48 , it being understood that contact 24 may be substituted for contact 22 in this grouping . conductance meter 36 receiving the current from plurality of contacts 86 would , thus , determine the conductivity or of tear fluid 30 eg : 20 - 2000 microamps . in certain cases such measurement could be in units of voltage . this measurement is easily translated by mathematical tables into a measurement of the tear fluid osmolality ( mosm ). it has been determined that the average normal human tear meniscus osmolality ( tonicity ) is 302 mosm . &# 34 ; dry eye &# 34 ; normally begins with a reading greater than 311 mosm . moderately severe dry eye exhibits an average tear tonicity of 343 mosm , while severe dry eye exhibits a value as high as 360 mosm . such results have been established by j . p . gilbard , previously discussed . any readout 94 , analog or digital , on conductance meter 36 may be programmed to read the mosm value rather than the electrical activity value , eg : amperage . in operation , the patient being examined would be asked to gently yet completely blink the lids of eye 80 a number of times to adequately mix the meniscus tear fluid with ocular surface tear fluid 28 before the contact of probe 12 on conjunctiva 32 is effected . the operator would then gently and securely touch the plurality of contacts 20 , 20a , 20b , or membrane 68 to an area of conjunctiva 32 on either side of , or above or below the cornea 92 of eye 80 , fig5 . plurality of contacts 20 , 20a , 20b , or membrane 68 substantially make contact with fluid 30 , since end surface 28 of end portion 16 substantially conforms to the bulbar conjunctival curvature . after this procedure , conductance meter 36 would read the conductance translated to osmolality of tear fluid 30 between pairs of equidistant contacts . probe 12 may selectively employ sodium , potassium , chloride , calcuim and like ions present in tear film 30 , in this regard . as heretofore described , contacts , such as contacts 24 and 22 of fig6 may be repeatedly interchanged to produce the potential necessary to obtain tonicity values readable on conductance meter 36 readout 94 . this interchange of contacts may be necessary to obviate electrode polarization error and to obtain measurements of osmolality in several areas of the conjunctiva . further , such multiple readings may be automatically averaged and recorded . in addition , multiple readings may be obtained and compared for reproducibility before display . it should be noted , that probe 12 may be precisely positioned by affixing it to an existing biomicroscope normally found in ophthalmologic and optometric examining rooms . while in the foregoing embodiments of the invention have been set forth in considerable detail for the purpose of making a complete disclosure of the invention it may be apparent to those of ordinary skill in the art that numerous changes may be made in such detail without departing from the spirit and principle of the invention .
a device for detecting keratoconjunctivitis sicca utilizing a probe including a body having an end portion . a plurality of electrical contacts are mounted in spaced configuration at the end portion of the probe body for simultaneous contact with the tear fluid of the ocular conjunctiva , or components thereof . an electrical potential is applied to at least one of the plurality of the electrical contacts and electrical activity , such as conductance , between the one electrical contact to another electrical contact is measured relative and the interposed tear fluid .