Calculating conjunctival redness

1. A computer implemented method for evaluating a condition of an ocular surface based on a color of the ocular surface, the method comprising:

obtaining a digital image of at least a portion of the ocular surface;

receiving a selection of a portion of the image as an evaluation area;

for each of a plurality of pixels within the evaluation area:

determining a plurality of color components that are based on a Cartesian color space,

determining, from the color components, a hue value in a polar coordinate based hue-saturation-value (HSV) color space,

selecting an angle range in accordance with a color associated with the ocular condition being evaluated,

determining that the hue value lies within the angle range that represents the color associated with the condition being evaluated in a hue circle representation of the HSV color space,

mapping the hue value to a scalar value within a predetermined range, in response to determining that the hue value lies within the angle range,

selecting a function of one or both of the saturation and value components of the HSV color space, wherein the function is selected based on the condition being evaluated, and

determining a color value as a product of the scalar value and the function of one or both of the saturation and value components of the HSV color space; and

generating a color score for the evaluation area based on an average of the color values of the plurality of pixels, wherein the color score of the ocular surface relates to a quantitative evaluation of the condition of the ocular surface.

2. The method of claim 1 , wherein the digital image further comprises an area of reference white color.

3. The method of claim 2 , further comprising

receiving a selection of at least a portion of the reference white color;

determining an average gain associated with the portion of the reference white color; and

applying the average gain to each of the plurality of pixels within the evaluation area.

4. The method of claim 1 wherein a parabolic curve is used in mapping the hue value to the scalar value within the predetermined range.

5. The method of claim 1 , wherein the selection of the evaluation area is received through a graphical user interface in which the digital image is presented.

6. The method of claim 5 , wherein the selection of the evaluation area is received as a polygonal area of the digital image selected through the graphical user interface.

7. The method of claim 1 , wherein the ocular surface comprises conjunctiva.

8. The method of claim 1 , wherein the Cartesian color space is an RGB color space.

9. The method of claim 1 , further comprising storing the color score and an association of the color score with the digital image.

10. The method of claim 1 , wherein the digital images are related to one or more of corneal neovascularization, fluorescein stained epithelial punctate keratitis and epithelial defects, eyelid and skin telangiectasia, and conjunctival/scleral pigmented lesions.

11. The method of claim 1 , wherein the angle range is determined based on whether the condition is a conjunctival condition or a corneal neovascularization condition.

12. The method of claim 3 , further comprising omitting an area of specular reflection from the portion of the reference white color in determining the average gain.

13. The method of claim 1 , wherein to evaluate conjunctival redness, the color value is determined as a product of the scalar value and a saturation component of the polar coordinate based color space.

14. The method of claim 1 , wherein to evaluate conjunctival/scleral pigmented lesions or fluorescein stained punctuate keratitis, the color value is determined as a product of the scalar value, a saturation component, and a brightness component of the polar coordinate based color space.

15. The method of claim 1 , further comprising scaling the color score within a predetermined range.

16. The method of claim 15 , wherein the predetermined range is 0-100.