Method and system for evaluating progression of age-related macular degeneration

Patent metadata

Field	Value
Publication number	US-9737205-B2
Application number	US-201414908519-A
Country	US
Kind code	B2
Filing date	Jul 30, 2014
Priority date	Jul 31, 2013
Publication date	Aug 22, 2017
Grant date	Aug 22, 2017

Abstract

Disclosed is a method for analyzing retinal image data obtained using spectral-domain optical coherence tomography (SD-OCT). The image data comprise a cross-section of the retina and an en face image of the retina of a subject having AMD (age-related macular degeneration). The image data are processed to obtain an accurate structure showing locations, shape, size, and other data on drusen (deposits under the retina). This structural information is processed to extract quantitative drusen features that are indicative of a risk of progression of AMD from the dry form to the wet form of the disease in a given subject and defined time period, including short time intervals (one year or less). Relevant drusen features used include number, en face area and volume of drusen detected; shape of drusen detected; density of drusen; and reflectivity of drusen. The method uses the extracted drusen features in combination with clinical data and measurement of the changes of the quantitative image features over time to derive a risk score for whether or not the subject will progress from dry AMD to wet AMD in a defined time period.

First claim

What is claimed is:

1. A method for analyzing optical coherence tomography (OCT) images of a retina, comprising the steps of:
(a) obtaining an OCT image of a subject's retina and corresponding demographic data, including age, gender, and presence of age-related macular degeneration (AMD) in the subject;
(b) processing the OCT image of step (a) to define an inner retinal pigment epithelium boundary and an outer retinal pigment epithelium boundary;
(c) identifying drusen using the boundaries defined in step (b);
(d) characterizing identified drusen by quantitative values representing characteristics of identified drusen; and
(e) using the quantitative values obtained in step (d) and demographic data from step (a) to obtain a score indicating a likelihood of progressing from dry AMD to wet AMD.

2. The method of claim 1 wherein the step of characterizing identified drusen comprises determining values for one or more of:
(i) drusen slope expressed as height versus en face area; (ii) drusen reflectivity expressed as pixel intensity; (iii) drusen height; (iv) drusen area, (v) drusen volume, and (vi) drusen number.

3. The method of claim 2 further comprising a step wherein values (i) through (vi) are measured at separate time points, and a difference in measurements between time points is calculated.

4. The method of claim 1 wherein the quantitative values include one, two or three of maximum height of drusen and standard deviation of pixel intensity in a normalized spectral domain optical coherence tomography (SD-OCT) image inside drusen regions; and a slope of linear fit through time of mean en face area per drusen.

5. The method of claim 1 wherein the quantitative values are a measurement of standard deviation of drusen reflectivity and changes with time in mean drusen area.

6. The method of claim 1 comprising using SD-OCT to generate the OCT images.

7. The method of claim 1 wherein said demographic data of step (a) further includes at least one, two or three of: (a) exceeding an age of 60 years; (b) a previous diagnosis of dry AMD; and (c) a genetic predisposition to AMD.

8. The method of claim 1 wherein the step of processing an OCT image in step (b) further includes determination of one or more of the following retina layer boundaries: inner limiting membrane (ILM), inner retinal nerve fiber layer boundary (iRNFL), outer retinal nerve fiber layer boundary (oRNFL), outer boundary of the inner plexiform layer (IPL), outer boundary of the inner nuclear layer (INL), outer boundary of the outer plexiform layer (OPL), inner boundary of the inner segment/outer segment junction (IS), and outer boundary of the inner segment/outer segment junction (OS), in addition to inner retinal pigment epithelium boundary (iRPE), and outer retinal pigment epithelium boundary (oRPE).

9. The method of claim 8 comprising determining at least nine boundary layers.

10. The method of claim 8 wherein boundary determination includes calculation of particular curvature of boundary layers.

11. The method of claim 1 wherein the step of characterizing identified drusen further comprises the step of measuring maximum drusen height, wherein an increase in drusen height indicates an increased likelihood of progression to wet AMD.

12. The method of claim 1 wherein the step of characterizing identified drusen further comprises measuring standard deviation of pixel intensity resulting from drusen reflectivity.

13. The method of claim 1 further comprising the step of comparing previously measured values from other patients to those measured in step (d), wherein increased values in measured values in step (d) compared to previously measured values indicate an increased likelihood of progression from dry AMD to wet AMD.

14. A method for analyzing optical coherence tomography (OCT) images of a retina, comprising the steps of:
(a) obtaining a subject's demographic data, including age, gender, presence of age-related macular degeneration (“AMD”), and further obtaining OCT images of the subject's retina;
(b) processing the OCT images of step (a) to define segmentations of three dimensional retinal layers, including an inner boundary and an outer boundary of retinal pigment epithelium (RPE);
(c) identifying drusen segmentations using boundaries obtained in step (b);
(d) using drusen segmentations calculated in step (c) to determine a plurality of three-dimensional drusen features having individual numerical values; and
(e) using (i) the individual numerical values obtained in step (d); (ii) historical numerical values corresponding to values measured in step (d); and (iii) subject demographic data in step (a) to obtain an AMD score representing a likelihood of progression of AMD.

15. A method for assessing risk for progression from Age-Related Macular Degeneration (AMD), comprising the steps of:
(a) obtaining subject demographic data and OCT images of said retina;
(b) processing said OCT images to define segmentations of three dimensional retinal layers, including an inner boundary and an outer boundary of retinal pigment epithelium (RPE);
(c) identifying drusen segmentations using boundaries obtained in step (b);
(d) using drusen segmentations identified in step (c) to determine a plurality of three dimensional drusen features having individual numerical values comprising
(i) number of drusen identified,
(ii) extent of retinal area affected by drusen,
(iii) mean area per drusen detected,
(iv) mean volume of drusen detected,
(v) shape of drusen detected,
(vi) density of drusen, and
(vii) reflectivity of drusen; and

(e) using (i) the individual numerical values obtained in step (d); (ii) historical numerical values corresponding to values measured in step (d); and (iii) subject demographic data in step (a) to assess a risk of progression of AMD, wherein higher values of values in (i) through (vii) indicate a higher risk of progression.

16. An OCT device comprising
(a) storage means for holding a subject's demographic data, including age, gender, and presence of age-related macular degeneration (AMD);
(b) components for obtaining OCT images of the subject's retina;
(c) instructions for analyzing OCT images of the subject to define an inner retinal pigment epithelium boundary and an outer retinal pigment epithelium boundary;
(d) instructions for identifying drusen using boundaries to identify drusen by quantitative values for at least one of: (i) drusen slope expressed as height versus en face area; (ii) drusen reflectivity expressed as pixel intensity; a value that is at least one of (iii) drusen height; (iv) drusen area, (v) drusen volume, (vi) drusen number and (vii) drusen reflectivity,
wherein measured values (i) through (vii) as determined in step (d) are measured at separate time points, and a difference in measurements between time points is calculated; and
(e) logic means for using quantitative values obtained in step (d) and demographic data from step (a) to obtain a score wherein increases in value in the quantitative values indicates an increased likelihood of progressing from dry AMD to wet AMD.

17. The OCT device of claim 16 wherein the quantitative values used in step (e) are all of (iii) through (vii), inclusive.

18. The OCT device of claim 16 further comprising an SD-OCT device.

19. An OCT device configured to carry out and store retinal images derived according to instructions, comprising:
(a) obtaining an OCT image of a subject's retina and corresponding demographic data, including age, gender, and presence of age-related ma

Assignees

• Univ Leland Stanford Junior

Inventors

• Rubin Daniel L
• Garcia Luis De Sisternes

Classifications

• A61B3/102 Primary

  for optical coherence tomography [OCT] · CPC title

• G06T7/0012

  Biomedical image inspection · CPC title

• A61B3/1225

  using coherent radiation · CPC title

• G06T2207/10101

  Optical tomography; Optical coherence tomography [OCT] · CPC title

• A61B3/0025 Primary

  characterised by electronic signal processing, e.g. eye models · CPC title