Pupil edge region removal in digital imaging
A digital imaging system processes digital images of a subject's fundus and/or pupils to determine pupil edge region pixels. Pupil edge region pixels are removed and a glint area is identified and interpolated over. Resulting images can be processed to determine a pixel intensity distribution slope. Using the pixel intensity distribution slope, refractive error determinations can be made.
1. A method for removing a pupil edge region from a digital image, the method comprising:
identifying a plurality of pupil pixels in the digital image;
identifying a glint area in the plurality of pupil pixels;
generating interpolated pupil data, including interpolating a first portion of the plurality of pupil pixels, the first portion including the glint area;
determining a representative intensity of the interpolated pupil data;
using the representative intensity, generating a threshold;
generating a binary image of the digital image using the threshold;
removing a pupil area of the binary image;
averaging remaining outer pupil pixel intensity values in the binary image, thereby generating a pupil edge region threshold; and
removing the pupil edge region from the digital image using the pupil edge region threshold;
wherein removing the pupil edge region includes removing pixels having an intensity value that is lower than the pupil edge region threshold.
2. The method according to claim 1 , wherein removing the pupil edge region from the digital image includes applying a mask to the digital image.
3. The method according to claim 2 , wherein removing the pupil edge region from the digital image includes removing pixels included in the mask.
4. The method according to claim 1 , wherein interpolating the first portion of the plurality of pupil pixels includes identifying probable glint pixels, the probable glint pixels being likely to be part of the glint area.
5. The method according to claim 4 , wherein interpolating the first portion of the plurality of pupil pixels includes:
generating new pixel values for the probable glint pixels, including evaluating intensity values for pixels proximate to the probable glint pixels; and
replacing the probable glint pixels with the new pixel values.
6. The method according to claim 5 , wherein determining the plurality of pupil pixels includes:
obtaining a center point of a pupil in the digital image; and
obtaining a radius of the pupil in the digital image.
7. The method according to claim 6 , the radius of the pupil being no greater than 2.5 mm.
8. The method according to claim 1 , wherein the representative intensity is a mean of the interpolated pupil data.
9. The method according to claim 1 , wherein generating the threshold includes multiplying the representative intensity by a multiplier; and
wherein removing the pupil area of the binary image includes removing a center area of a pupil.
10. The method according to claim 9 , wherein the multiplier is greater than 1 and no greater than 3.
11. The method according to claim 10 , wherein the multiplier is 2.
12. A method for generating a mask of a pupil edge region in a digital image, the method comprising:
receiving the digital image;
identifying a plurality of pupil pixels in the digital image;
identifying a glint area in the plurality of pupil pixels;
generating interpolated pupil data, including interpolating a first portion of the plurality of pupil pixels, the first portion including the glint area, wherein interpolating the first portion of the plurality of pupil pixels includes:
identifying probable glint pixels, the probable glint pixels being likely to be part of the glint area;
generating new pixel values for the probable glint pixels, including evaluating intensity values for pixels proximate to the probable glint pixels; and
replacing the probable glint pixels with the new pixel values;
determining a representative intensity of the interpolated pupil data;
using the representative intensity, generating a threshold;
generating a binary image of the digital image using the threshold;
removing a center pupil area of the binary image;
averaging remaining outer pupil pixel intensity values in the binary image, thereby generating a pupil edge region threshold;
using the pupil edge region threshold, applying the mask to the digital image; and
removing pixels included in the mask from the digital image.
13. The method according to claim 12 , wherein determining the plurality of pupil pixels includes:
obtaining a center point of a pupil in the digital image; and
obtaining a radius of the pupil in the digital image.
14. The method according to claim 13 , wherein the representative intensity is a mean of the interpolated pupil data; and
wherein generating the threshold includes multiplying the representative intensity by a multiplier, the multiplier being greater than 1 and no greater than 3.
15. A medical imaging system, comprising:
an illumination assembly;
a digital camera assembly;
a processing unit; and
memory storing instructions that, when executed by the processing unit, cause the medical imaging system to:
illuminate an eye fundus of a subject with the illumination assembly;
receive a digital image with the digital camera assembly;
identify a plurality of pupil pixels in the digital image;
identify a glint area in the plurality of pupil pixels;
generate interpolated pupil data, including interpolating a first portion of the plurality of pupil pixels, the first portion including the glint area, wherein interpolating the first portion of the plurality of pupil pixels includes to:
identify probable glint pixels, the probable glint pixels being likely to be part of the glint area;
generate new pixel values for the probable glint pixels, including evaluating intensity values for pixels proximate to the probable glint pixels; and
replace the probable glint pixels with the new pixel values;
determine a representative intensity of the interpolated pupil data;
use the representative intensity to generate a threshold;
generate a binary image of the digital image using the threshold;
remove a center pupil area of the binary image;
average remaining outer pupil pixel intensity values in the binary image, thereby generating a pupil edge region threshold; and
remove a pupil edge region from the digital image using the pupil edge region threshold, including removing pixels having an intensity value that is lower than the pupil edge region threshold.
16. The medical imaging system according to claim 15 , wherein the representative intensity is a mean of the interpolated pupil data;
wherein generating the threshold includes to multiply the representative intensity by a multiplier, the multiplier being greater than 1 and no greater than 3; and
wherein determining the plurality of pupil pixels includes to:
obtain a center point of a pupil in the digital image; and
obtain a radius of the pupil in the digital image.