Diagnosis method and diagnostic device for distinguishing types of dry eye syndrome

1 . A diagnostic method for distinguishing a type of dry eye syndrome, comprising:

(a) checking a tear film break-up time point and a break-up location by photographing a cornea of an eye of a subject and checking in time series at least one or more times of the tear film break-up time point, at which a reflected image from the photographed cornea is confirmed to be broken over time;

(b) checking a corneal surface temperature by measuring a surface temperature of the cornea of the subject to be evaluated using a thermal imaging camera performed simultaneously with the photographing of a tear film of the eye to check in time series a change in the surface temperature of the cornea with respect to time;

(c) mapping the tear film break-up time point and the change in the surface temperature of the cornea based on time to compare the tear film break-up time point and a time point of the temperature change of the cornea surface;

(d) diagnosing the type of dry eye syndrome based on any one of the tear film break-up time point and a location of a surface temperature change time point of the cornea corresponding thereto, in a mapping result in step (c), wherein:

the dry eye syndrome is determined to be an evaporative dry eye syndrome, if an initial tear film break-up time point corresponds to a time point having a greatest decrease slope in the temperature change of the cornea; and

the dry eye syndrome is determined to be a mucus layer-deficient dry eye syndrome, if the temperature change of the cornea linearly decreases beyond the time point at which the tear film break-up is observed, and then decreases sharply after a certain period of time so that a sharp temperature decrease is observed later than the initial tear film break-up time point; and

(e) calculating an evaporative heat transfer coefficient at the break-up location by dividing a thermal conductivity of a tear fluid by a thickness of a tear film at the break-up location, according to a formula h=k fluid /δ, where h is the evaporative heat transfer coefficient, k fluid is the thermal conductivity of the tear fluid, and δ is the thickness of the tear film at the break-up location,

wherein the diagnosing in step (d) is further based on a corneal surface temperature decrease at the break-up location determined from the calculated evaporative heat transfer coefficient,

wherein, under conditions of an ambient temperature of the corneal surface of 10° C., an inner temperature of an eyeball of 34° C., a tear film thickness before the break-up of 10 μm, and a surface temperature of a tear layer of the corneal surface of 28° C., the corneal surface temperature decreases to 22° C. when tear evaporation occurs in the tear film having a thickness of 5 μm at the break-up location, and the corneal surface temperature decreases to 25.5° C. when tear evaporation occurs in the tear film having a thickness of 7 μm at the break-up location.

2 . The diagnostic method for distinguishing type of dry eye syndrome of claim 1 , wherein in step (a), the cornea of the eye is photographed using an optical camera, and tear film break-up area and location are calculated based on area and time at which an image is seen to be broken by reflection from the cornea and the time is confirmed.

3 . A diagnostic apparatus for distinguishing a type of dry eye syndrome, comprising:

an optical camera for taking an image of a cornea of an eye;

a thermal imaging camera for obtaining a thermal image of the cornea of the eye and measuring a temperature change of the cornea; and

a controller configured to determine the type of dry eye syndrome by mapping and analyzing the image photographed by the optical camera and the thermal image obtained by the thermal imaging camera, wherein:

the controller is configured to:

determine the dry eye syndrome to be an evaporative dry eye syndrome, if an initial tear film break-up time point corresponds to a time point having a greatest decrease slope in the temperature change of the cornea; and

determine the dry eye syndrome to be a mucus layer-deficient dry eye syndrome, if the temperature change of the cornea linearly decreases beyond the time point at which the tear film break-up is observed, and then decreases sharply after a certain period of time so that a sharp temperature decrease is observed later than the initial tear film break-up time point,

wherein the controller is further configured to calculate an evaporative heat transfer coefficient at a break-up location by dividing a thermal conductivity of a tear fluid by a thickness of a tear film at the break-up location, according to a formula h=k fluid /δ, where h is the evaporative heat transfer coefficient, k fluid is the thermal conductivity of the tear fluid, and δ is the thickness of the tear film at the break-up location,

wherein the controller determines a corneal surface temperature decrease at the break-up location based on the calculated evaporative heat transfer coefficient,

wherein, under conditions of an ambient temperature of the corneal surface of 10° C., an inner temperature of an eyeball of 34° C., a tear film thickness before the break-up of 10 μm, and a surface temperature of a tear layer of the corneal surface of 28° C., the corneal surface temperature decreases to 22° C. when tear evaporation occurs in the tear film having a thickness of 5 μm at the break-up location, and the corneal surface temperature decreases to 25.5° C. when tear evaporation occurs in the tear film having a thickness of 7 μm at the break-up location.

4 . The diagnostic apparatus for distinguishing type of dry eye syndrome of claim 3 , wherein the controller comprises:

a mapping unit for mapping time-series change state of the tear film break-up time point obtained by the optical camera and time-series change state of the surface temperature of the cornea obtained by the thermal imaging camera on a time basis; and

dry eye type determination unit for determining the type of dry eye syndrome by comparing initial time point among the tear film break-up time point and the temperature change time point photographed with the thermal imaging camera from two mapped images.