WO2022175945A1

WO2022175945A1 - System and method for monitoring optic disc conditions

Info

Publication number: WO2022175945A1
Application number: PCT/IL2022/050184
Authority: WO
Inventors: Avihu Meir Gamliel; Michael Aronov; Noam Allon; Moshe Markowitz; Eyal Margalit
Original assignee: Spring Vision Ltd
Current assignee: Spring Vision Ltd
Priority date: 2021-02-16
Filing date: 2022-02-16
Publication date: 2022-08-25
Anticipated expiration: 2023-08-16

Abstract

A method and system are presented for monitoring conditions of an optic disc of an eye to detect pathology of the eye. According to this technique, data indicative of a 3D structure of the optic disc is provided and analyzed to determine at least such parameter as a ratio between a surface area of a cup portion of the optic disc and an optic disc area. This at least one parameter is used to identify the condition of the optic disc and classify this condition in association with at least one corresponding pathology.

Description

SYSTEM AND METHOD FOR MONITORING OPTIC DISC CONDITIONS

TECHNOLOGICAL FIELD AND BACKGROUND

The present invention is in the field of retinal imaging and relates to a system and method for monitoring optic disc conditions for the purposes of diagnostics of various pathological processes. The eye is unique because of the transparency of its optical media. Almost all eye structures can be examined with appropriate optical equipment and lenses. Optic disc or optic nerve head (ONH) is placed 3 to 4 mm to the nasal side of the fovea, and is shaped as a vertical oval, with a central depression or “cup”. This depression can have a variety of shapes which can be significant for diagnosis of several retinal diseases, which, in turn caused by various pathophysiological processes. The optic disc is the point of exit for ganglion cell axons leaving the eye to form the optic nerve.

Optic disc changes are related to various pathologies of the eye, including glaucomatous changes, elevated intra cranial pressure, degenerative diseases and more.

For example, glaucoma is one of the most common causes of visual impairment and blindness worldwide, characterized by elevated intra ocular pressure (IOP). In turn, the elevated pressure within the ocular media, damages cellular structures, including the highly sensitive nervous tissue of the retina and optic disc, eventually leading to loss of visual capabilities, and when severe, even blindness.

Nowadays, for example, glaucomatous changes in the eye are diagnosed using multiple imaging modalities and clinical tests: visual acuity, visual fields, IOP, retinal nerve fiber layer (RNFL) thickness measurement and different parameters of the optic disc, are all measured and analyzed through various devices and techniques to provide a diagnosis of glaucoma or ocular hypertension. The optic disc is imaged using either optical coherence tomography (OCT) or stereoscopy (mainly investigational), providing 3D images of the optic disc. Following image acquisition, various parameters of the optic disc are derived from the image data, in order to determine glaucomatous optic disc changes.

GENERAL DESCRIPTION

There is a need in the art for a novel technique enabling simple and accurate diagnostic evaluation of pathological processes affecting the optic disc changes.

According to the conventional approach, the derived parameters, from which glaucomatous optic disc changes are determined, include cup-to-disc ratio (of respective diameters), vertical (diameters) cup-to-disc ratio, cup-area to disc-area ratio, cup depth and others. Findings from the mentioned parameters are equivocal, and different studies have shown different associations to glaucoma, glaucomatous optic disc changes and elevated IOP. Indeed, while the optic disc has fixed dimensions in every individual, the optic cup (a substructure of the optic disc), depending on local environmental conditions, can undergo structural changes, including diameter, depth and volume changes. When exposed to elevated pressure, ganglion cells in the retina start eroding, and their axons degenerate and disappear from the optic nerve head. They begin to degenerate at the edges of the cup and then the damage progresses to more peripheral areas of the optic disc. Thus, the described changes will first be manifested as increased depth of the optic cup, combined with peripheral loss of cells and increased volume of the optic cup. When the depth of the optic cup reaches its limits, loss of cells will progress in a concentric manner, from center to periphery, manifesting in increasing optic cup diameter, volume and surface area of the inner walls of the optic cup.

The conventional approach for evaluating the above parameters is typically based on 2D image data. Such parameter as cup-area to disc-area ratio used in the conventional techniques utilizes 2D images, and thus the surface area of the cup is actually that of the 2D projection of the cup portion. The inventors have found at least one new parameter of optic disc which is/are more informative of various pathophysiological processes affecting the optic disc condition. Further, the inventors have developed imaging method and system for determining said parameters of the optic disc in a relatively simple manner.

More specifically, the inventors have found that at least one such parameter as a ratio between a surface area of the cup portion of the optic disc and the optic disc area can be used to provide accurate diagnosis of the optic disc condition (e.g., glaucomatous optic disc changes), affected by pathophysiological processes (e.g., causing elevated IOP). However, according to the invention the surface area of the cup portion is a true surface area of a 3D surface, rather than the conventionally used 2D projection thereof. As for the optic disc area, this can be a surface area of a 2D projection of the optic disc (together with the cup portion).

The inventors have shown that a change of the surface area of the cup portion may not result in a change of the surface area of the 2D projection of the cup portion. A change in the ratio between the surface area of the cup portion and the optic disc area is indicative of a pathological condition (e.g. earlier stages of glaucoma development among other retinal pathologies), while the cup to disc ratio determined from the 2D image data remains substantially unchanged. Indeed, the ratio between 2D cup area and ONH area is an unstable measure since different physicians marks the cup differently in 2D images (i.e., it is very hard to determine the cup boundaries from 2D images). Hence, examining the ONH in 3D space, and in particular the cup portion, provides much stable measurement. Accurate cup condition measurement is indicative of a pathological condition (e.g., earlier stages of glaucoma development among other pathologies).

Thus, one or more of the following parameters can also be used to further improve the diagnostics of pathological conditions: cup-volume to disc-area ratio (mm), squared cup-depth to disc-area ratio, and cup-surface-area to disc-area ratio.

The above new parameter(s) have not been previously explored in clinical studies. Furthermore, this/ these new parameter(s) can be measured with extremely high precision using a novel technique of the present invention.

According to the technique of the invention, data indicative of a 3D structure of the optic disc is used to determine therefrom said at least ratio between the surface area of the cup portion of the optic disc and the optic disc area. To this end, 2D retinal images can be acquired with any suitable imaging systems, e.g., traditional fundus photography imaging device, followed by image processing and reconstruction method of the present invention, which provides for highly accurate 3D reconstruction of the optic disc and its substructures. This provides simple and low-cost technique for diagnostic evaluation of pathological processes affecting the optic disc. It should, however, be understood that, generally, the 3D image\point cloud data can be obtained using any 3D photography method, such as structured light, stereovision, OCT radial scans, etc.

Thus, according to one broad aspect of the invention, there is provided a method for monitoring conditions of optic disc of an eye, the method comprising: providing data indicative of a 3D structure of the optic disc; and analyzing said data indicative of the 3D structure of the optic disc and determining at least a ratio between a surface area of a cup portion of the optic disc and an optic disc area, thereby enabling to utilize at least said ratio between the surface area of the cup and the optic disc area to determine and classify the condition of the optic disc in association with at least one predetermined pathology of patient’s eye.

Preferably, said analyzing the data indicative of the 3D structure of the optic disc also comprises determining one or more of the following parameters: a ratio between cup- volume and optic disc area and a ratio between squared cup-depth and the surface are of the optic disc.

In some embodiments, the data indicative of the 3D structure of the optic disc includes 3D point cloud data.

In some embodiments, the data indicative of the 3D structure of the optic disc is derived from processing image data indicative of two or more 2D retinal images acquired at different angles. Preferably, the two or more 2D retinal images are acquired by fundus camera system.

In some embodiments, processing of OCT data may be used to provide the data indicative of the 3D structure of the optic disc. Such OCT data comprises 2D OCT images of several sections of the retina including one or more of the following sections: horizontal sections, vertical sections, and centralized sections.

The 3D point cloud data may be derived from stitching of said two or more 2D retinal images. This 3D data may be obtained by applying to the 2D image data a 3D reconstruction method from video based for example on bundle adjustment algorithm. Alternatively, as mentioned above, the data indicative of the 3D structure of the optic disc (e.g., 3D point cloud data) is acquired using any 3D photography method.

The analyzing of the data indicative of the 3D structure of the optic disc may include deriving from 3D point cloud data a mesh in the form of triangular structures with different areas; performing summation of areas of different triangular structures; and determining surface areas of the optic disc and cup region thereof.

According to another broad aspect of the invention, there is provided a method for monitoring conditions of optic disc of an eye, the method comprising: providing data indicative of a 3D structure of the optic disc; and analyzing said data indicative of the 3D structure of the optic disc and deriving data indicative of a degree of applanation of a cup portion of the optic disc, to classify the optic disc condition in association with at least one predetermined pathology of patient’s eye, said data indicative of the degree of applanation of the cup portion of the optic disc comprising one or more of the following parameters derived from the 3D structure of the optic disc: a ratio between cup- volume and optic disc area; a ratio between squared cup- depth and optic disc area; and a ratio between a surface area of the cup portion of the optic disc and the optic disc area.

According to yet further broad aspect of the invention, there is provided a monitoring system for monitoring conditions of optic disc of an eye. The monitoring system is configured as a computer system in data communication with a retinal image data provider and comprises data input utility, memory and data processor. The data processor comprises: an analyzer configured and operable to analyze data indicative of a 3D structure of the optic disc and determine at least a ratio between a surface area of a cup portion of the optic disc and an optic disc area, ; and an optic disc condition classifier configured and operable to utilize at least said ratio between the surface area of the cup portion and the optic disc area to identify the optic disc condition and classify the optic disc condition in association with at least one predetermined pathology.

Preferably, the analyzer is also capable of determining, from the data indicative of the 3D structure of the optic disc, one or more of the following parameters: a ratio between cup-volume and optic disc area; and a ratio between squared cup-depth and optic disc area. Either one or both of these additional parameters is/are used by the optic disc condition classifier to classify the optic disc condition in association with the pathology of patient’s eye.

In some embodiments, the data processor also comprises a 3D image generator configured and operable to process retinal image data comprising two or more 2D retinal images acquired with different angles and generate the data indicative of the 3D structure of the optic disc.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Fig. 1 a block diagram of a monitoring system of the invention;

Fig. 2 a flow diagram of the method of the invention for monitoring optic disc conditions;

Fig. 3 exemplifies a 2D image of an optic disc and its optic cup region;

Figs. 4A and 4B exemplify the technique and the result of stitching a few retinal images;

Fig. 4C exemplify the 3D sparse point cloud derived from the stitched images of Fig. 4B;

Fig. 5 exemplifies 3D structure of ONH derived as dense point cloud;

Figs. 6A-6C and 6A'-C exemplify several horizontal OCT scans of the optic disc taken from the same depth and used for later 3D reconstruction of the ONH, wherein Figs. 6A-6C show the ONH image with the OCT scan position indicated by a bold arrow and Figs. 6A'-6C show the respective OCT scans. Fig. 6D schematically exemplifies the necessary 2D sections of OCT scans if several angles are scanned at the same depth;

Figs. 7A-7D and 7A’-7D’ schematically illustrate different optic cup conditions as seen in 2D and 3D images, respectively, wherein Figs. 7A and 7A’ show normal optic cup, Figs. 7B and 7B’ show early cup pathological changes, Figs. 7C and 7C’ show advanced cup pathology, and Figs. 7D and 7D’ show papilledema;

Figs. 8A-8E exemplify the technique of 3D reconstruction of the optic disc; wherein: Figs. 8A-8C correspond to a patient with a pathology condition, Fig. 8A showing 2D image of a retina with suspected pathology taken by fundus camera, Fig. 8B showing the 2D image of the optic disc (ONH) extracted from the image of Fig. 8A, Fig. 8C showing 3D reconstruction of the optic disc by using multiple 2D images of the optic disc, similar to Fig. 8B, taken from different angles; and Figs. 8D-8E correspond to healthy condition, Fig. 8D showing 2D image of the optic disc (ONH) of a healthy retina, and Fig. 8E showing 3D reconstruction of the optic disc, with the same technique as Fig. 8C.

DETAILED DESCRIPTION OF EMBODIMENTS

Reference is made to Fig. 1 exemplifying, by way of a block diagram, the configuration of a control system 10 of the present invention for monitoring the conditions of an optic disc.

An image of the optic disc is exemplified in Fig. 3. Optic nerve cupping progresses as the cup portion of the optic disc becomes larger (in diameter, depth, volume and surface area) in comparison to the entire optic disc. Accordingly, cup to disc ratio is a commonly used parameter indicative of the optic disc abnormality.

As described above, such cup to disc ratio refers to dimensions of 2D projections of the cup portion and the entire optic disc (with its cup portion). The same cup to disc ratio may correspond to different values of the ratio between the surface area of the cup and the optic disc area. Hence, the sensitivity of the technique based on the cup to disc ratio is not sufficient to determine various pathological conditions of patient’s eye. Moreover, 2D image data does not allow accurate determination of the 2D surface area of the cup as well as that of the optic disc because extraction of such parameters from 2D images requires accurate segmentation, while detection of the boundary of the cup portion is impeded by relatively low contrast. As shown in Fig. 1, the monitoring system 10 of the present invention is generally a computer system including inter alia such functional utilities (software/hardware utilities) as data input 14, memory 16, data processor 18, user interface 22 and possibly also display 20. For the purposes of the present invention, the data processor 18 includes an image processor 24 configured an operable according to the invention.

The monitoring system 10 is associated with image data provider 12, which may be a retina imaging system or any other imaging system or a storage device where the retinal image data is stored. In some embodiments, the invention utilizes retina images acquired by fundus camera of any known suitable configuration.

The monitoring system 10 may be part of (integral with) the retina imaging system or may be a separate system configured for data communication with the imaging system (e.g., fundus camera) or a separate storage device where the retina images (e.g., acquired by the fundus camera) are stored. The configuration may be such that software modules / utilities of the data processor 18 are distributed between the local control system of the fundus camera and the external monitoring system.

The image processor 24 includes an analyzer 26, which receives and analyzes 3D image data being data indicative of a 3D structure of the optic disc (e.g., 3D point cloud) and determines one or more of characteristic parameters of the optic disc.

As shown in Fig. 1 in dashed lines, in some embodiments, input image data may include 2D retinal images, and the image processor 24 may thus also include a 3D image generator 25 which is configured and operable to produce / reconstruct 3D image data of at least the cup portion of the optic disc from several 2D retinal images (generally, two or more such images) taken from different angles (using the same camera).

The 3D image generator 25 may include an image stitching utility 30 and a 3D point cloud generator 32.

The at least one characteristic parameters of the optic disc structure is a ratio Ri between surface area of the cup S_CUp and the optic disc area Adisc:

Rl= Scup/ Adisc

Additional characteristic parameters of the optic disc that may improve classification of the optic disc condition include the following: • ratio R2 (mm) between cup-volume, V_cup, and optic disc area A_diSC:

R2⁼ Vcup/ Adisc

• ratio R3 between squared cup-depth D_CUp and the optic disc area A_diSC,

R2⁼(Dcup)^/ Adisci

The above parameter Ri, and in some embodiments' combination of parameter Ri with any one or both of the above additional parameters R2 and R3, provides accurate indication of a degree of applanation of the cup.

The parameter(s) and/or the degree of the cup applanation derived from such parameter(s) may be further analyzed by optic disc condition classifier 28, which generates data indicative of the corresponding condition of the optic disc in association with related pathophysiological processes. The classifier 28 may utilize (may access) pre stored data (database) associating the value(s) of the above parameter(s) with pathophysiological processes in various groups of patients.

The operation of the above-described system 10 will now be described in more details with reference to Fig. 2 exemplifying a flow diagram 100 of the method of the invention for monitoring optic disc conditions.

In some embodiments, as shown in dashed lines, the system operation includes an initial stage 102 aimed at providing data about 3D structure of the optic disc from input data indicative of 2D retinal images. To this end, image data indicative of a number N (two or more) of 2D retinal images acquired from M (two or more) different angles by an imaging system 12 is provided (step 104), either during the imaging/inspection sessions (online mode) or from the storage utility (off line mode).

Generally, the imaging system 12 may include a fundus camera 12 and/or stereovision system, and/or structured light or OCT based system utilizing multiple illumination angles.

In some embodiments, the 2D images are used to create retinal montage (stitching several 2D retina images) in order to obtain wider Field of View (step 106), and perform 3D modeling based on any known in the art suitable technique (for example, 3D reconstruction from video/motion technique), to derive 3D sparse point cloud data (step 108). This is illustrated in Figs. 4A - 4C, where Figs. 4A and 4B exemplify the process and the result of stitching of four retinal images, and Fig. 4C shows 3D sparse point cloud derived from the stitching of these four images.

The above technique is generally known and therefore need not be described in details, except to note the following in relation to the present invention: Such stitching and 3D point cloud creation typically require registration of key points that appear on all images. The technique of the invention utilizes selection of key points in the region of the optic disc as being the most dense-in-features region of the retinal image.

Further, the invention may utilize creation of 3D image data from motion ideo algorithms, such as Bundle Adjustment (BA) which uses a number of iterations in order to estimate camera and optics parameters needed for 3D model estimation. This eliminates the need to know / measure camera/optics parameters used in the retinal image acquisition, as well as eliminates the need for prior 3D system calibration.

Fig. 5 exemplifies 3D structure as dense point cloud of the optic disc derived from three fundus camera images obtained by the technique of the invention.

Optical Coherence Tomography (OCT) is another known in the art technique that can be used to provide the 3D structure of a section of the eye and extract therefrom the characteristic parameter(s) used in the present invention. Imaging of the 3D structure of the ONH using spectral-domain OCT (SD-OCT) is known in the art. However, the present invention provides a different approach for reconstructing 3D cup surface from such data.

It should be noted that OCT scans provide 2D sections of the volumetric structure of the retina. According to the present invention, several such 2D sections obtained by OCD can be used in order to reconstruct the 3D structure of the ONH. More specifically, OCT scans may include several horizontalYvertical scans from the same depth or from several angles at a single depth.

In this connection, reference is made to Figs. 6A-6C and Figs. 6A’-6C’ exemplifying several horizontal OCT scans of the optic disc taken from the same depth and used for 3D reconstruction of the ONH. Figs. 6A-6C show the ONH images with the OCT scan position indicated by a bold arrow and Figs. 6A'-6C show the respective OCT scans. More specifically, Figs. 6A'-6C show an example of three OCT horizontal scans performed at different heights indicated by the respective bold arrows in Figs. 6A- 6C, drawn on top of the ONH image. These 2D scans demonstrate that the optic cup shows significant variation in cup depth and cup width. Fig 6D shows schematically a second method of obtaining OCT scans from several angles at the same depth. In both methods, , 3D reconstruction from the 2D scans of the ONH is performed to obtain 3D point cloud.

Another possibility is to use OCT scan data from several horizontal and/or vertical and/or centralized sections from the same depth. Any OCT system can be used to implement the teachings of the present invention. Also, 3D reconstruction from 2D scans does not require any prior knowledge about the specific imaging system.

Turning back to Fig. 2, the data indicative of the optic disc 3D structure (being either input data to the system or data obtained from the first-stage processing of 2D retinal images) is analyzed (stage 110). This stage is aimed at analyzing different surfaces of the optic disc. To this end, a mesh is derived from a point cloud (step 112). The mesh is constructed from triangular structures with different areas. Then, summation of areas of different triangles is performed (step 114), and this data is used to provide characterization of the surface areas of at least the cup potion of the optic disc but possibly also the entire optic disc area (step 116). As described above, the optic disc area may the surface area of the 2D projection (2D image) of the optic disc. These characteristics of the optic disc and cap portion thereof are then used to calculate the ratio Ri between the surface are of the cup portion and the optic disc area, and possibly also either one or both of ratios R2 and R3 (i.e. cup-volume to disc-area ratio (mm) R2, and squared cup depth to disc area ratio R3).

The optic disc area A_disc required for all the characteristic parameters Ri, R2 and R3 can be derived from a 2D surface and can be calculated by any known in the art technique, i.e., either from a 2D image directly (e.g., from images provided in step 104 in Fig. 2) or from the 3D point cloud (step 116 in Fig. 2) representing the 3D structure of the optic disc.

Cup-volume to optic disc area (R2) being a dimensional parameter (in mm) uses the cup's volume which is defined by an integral of cup's depths times the surface area at each depth. It should be noted that the volume of a large- area and shallow cup might be substantially equal to the volume of a small-area and deep cup, and therefore this parameter R2 should be considered in combination with the dimensionless parameter Ri (ratio between the surface area of the cup portion and the optic disc area) which would be of different values in such two cases, thereby enabling to evaluate the pathology condition.

As already stated above, as the ganglion cells in the retina and their axonal extensions within the optic nerve start dying (erode/erosion process) due to certain pathology (for example glaucoma), the first structural changes in the optic disc will be manifested as increased volume and depth of the optic cup. These changes can be quantitatively described by the parameters Ri, R2 and R3.

As the depth of the optic cap reaches its limits, the loss of axons progresses in a concentric manner, widening the optic cup which is manifested as increased diameter and surface area of the inner walls of the optic cap. The parameter Ri is a unitless (dimensionless) ratio between the surface are of the cup portion of the optic disc and the optic disc area and is accurately representing the pathology.

It is important to note that the technique of the present invention significantly facilitates the identification of the cup portion of the optic disc which is an essential parameter in detecting, for example, glaucoma. Even with most advanced known in the art image segmentation techniques, locating the boundary of the optic cap is still a challenging task. According to the teachings of the present invention, the cup portion border can be accurately found in the 3D point cloud data (step 116 of Fig. 2) where the first derivative of the surface is non-zero, considering appropriate thresholds above general 3D reconstruction noise.

Reference is now made to Figs. 7A-7D and 7A’-7D’ which exemplify different cap portion conditions including different pathologies as seen in 2D images (Figs. 7A-7D) and those which are important while cannot be seen in 2D images but can be properly identified from 3D image data (Figs. 7A’-7D’).

Figs. 7A and 7A’ correspond to the optic disc with a normal cup condition, i.e. no or weak optic nerve cupping effect. Figs. 7B-7B’ and 7C-7C’ correspond to early and advanced stages, respectively, of the cup's pathological changes. As can be seen in Figs. 7B’ and 7C\ the cup applanation increases with the development of the pathology.

Figs. 7D-7D’ show the papilledema condition (although this is not evolution of the pathology of Figs. 7B-7B’ and 7C-7C’). The term "papilledema" refers to swelling of the optic disc caused by elevated intracranial pressure (ICP). Papilledema can be regarded as an optic neuropathy akin to "glaucoma of the brain", where elevated ICP is a key pathogenic factor. The pathophysiological process involves interstitial edema of the optic nerves without functional axonal loss or functional visual loss, at least at the early stages. Functional visual loss occurs at more advanced stages, where axoplasmic stasis leads to neuronal dysfunction, with visual function often correlating to optic disc appearance in the acute setting. Papilledema is typically bilateral, symmetric in both eyes, and can be classified into 4 stages - early, fully developed, chronic and atrophic. The earliest sign of papilledema is obscuration of the optic disc margins, affecting superior and inferior poles first, followed by nasal and temporal portions of the optic disc. Venous engorgement is another typical sign of early papilledema. In fully developed papilledema the surface of the optic disc is clearly above the plane of the retina and is typically accompanied by flame-shaped hemorrhages and cotton wool spots caused by retinal nerve fiber layer ischemia. As this stage advances, the cup portion of the optic disc may begin to disappear (as shown in Fig. 7D and better seen in Fig. 7D’). In chronic papilledema, the optic disc develops a "champagne cork" milky gray appearance with obliteration of the cup portion. Finally, in the atrophic phase, the optic disc atrophies, the retinal vessels become narrow and sheathed, and the disc itself has grayish white to diffusely white appearance. Shunt vessels, resulting from central retinal venous drainage obstruction may occur and retinal pigment epithelial changes secondary to edema or subretinal hemorrhage can be seen.

There is maximal cup depth in advanced pathologies. When reaching the maximal depth the cup starts losing concentric edge tissue (as can be seen in Figs. 7C-7C’ relative to Figs. 7B-7B’).

Figs. 8A-8E show another example of 3D reconstruction of optic disc using the technique of the present invention. Here, Figs. 8A-8C correspond to a patient with a pathology condition, and Figs. 8D-8E correspond to a healthy condition.

Fig. 8A shows 2D image of the retina obtained with a fundus camera. The optic disc region is extracted from this image using segmentation techniques (which may be any known suitable techniques), and is shown in Fig. 8B. It should be noted that already at this stage the optic disc area may be calculated.

However, the structural parameter(s) of the cup portion (i.e., surface area, and possibly also volume and/or depth) that is/ are needed to calculate the characteristic parameter(s) (Ri, and possibly also R2 and/or R3) cannot be extracted from 2D images. Several 2D images were taken to produce the 3D reconstruction of the optic disc using, for example, the bundle adjustment algorithm and the result is shown in Fig. 8C. The use of bundle adjustment algorithm (being a specific, but not limiting example) provides the cameras positions) parameters estimation, and then any known suitable technique is used to utilize the camera position parameters to produce point cloud data and dense point cloud data followed by 3D reconstruction as a mesh. The border of the cap portion in Fig. 8C is clearly discernible, in contrast to that of Fig. 8B. In general, the cup portion segmentation is very tedious due to its interlink with many surrounding tissues and blood vessels, and the 3D reconstruction used in the present invention significantly improves the accuracy of the cup portion segmentation. The size of the cup portion extracted from Fig. 8C is indicative of that the respective patient might have a glaucoma.

Fig. 8D shows a 2D image of the optic disc of a healthy patient and the respective 3D reconstruction is shown in Fig. 8E. When the two images in Fig. 8B and Fig. 8D are compared and pathology in

Fig. 8B may be suspected, it is difficult to determine the parameters (at least the surface area) of the cup portion in Fig. 8B and its borders, whereas the 3D reconstructed images (Fig. 8C and Fig. 8E) using the technique of the present invention provide a significant improvement in the detection and characterization of pathologies. Thus, the present invention provides a relatively simple and effective technique for monitoring development of pathological processes affecting the optic disc changes. The technique of the present invention can be performed using any available fundus camera, stereovision, structured light, and any direct interferometric techniques and can be performed on a multispectral image, color image, grey-scale image, processed image, etc. As mentioned above, the present invention does not require input data about camera/optics parameters, and does not require prior 3D calibration of the system. The improvement in optic disc segmentation and classification approaches using the techniques of the present invention may help for the early diagnosis of various pathologies, in particular glaucoma.

Claims

CLAIMS:

1. A method for monitoring conditions of optic disc of an eye, the method comprising: providing data indicative of a 3D structure of the optic disc; and analyzing said data indicative of the 3D structure of the optic disc and determining at least a ratio between a surface area of a cup portion of the optic disc and an optic disc area, thereby enabling to determine the condition of the optic disc and classify said condition in association with at least one predetermined pathology.

2. The method according to claim 1, wherein said analyzing of the data indicative of the 3D structure of the optic disc further comprises determining at least one of the following parameters: a ratio between a volume of the cup portion and the optic disc area; and a ratio between a squared depth of the cup portion and the optic disc area.

3. The method according to claim 1 or 2, wherein the data indicative of the 3D structure of the optic disc includes 3D point cloud data.

4. The method according to any one of the preceding claims, wherein said providing of the data indicative of the 3D structure of the optic disc comprises data communication with an image data provider to receive said data therefrom.

5. The method according to any one of claims 1 to 3, wherein said providing of the data indicative of the 3D structure of the optic disc comprises receiving and processing image data indicative of two or more 2D retinal images acquired at different angles.

6. The method according to claim 5, wherein said two or more 2D retinal images are acquired by a fundus camera system.

7. The method according to claim 5, wherein said two or more 2D retinal images are acquired by one or more of the following imaging techniques: stereovision, structured light based imaging, and direct interferometric imaging.

8. The method according to claim 7, wherein said direct interferometric imaging technique is optical coherent tomography (OCT).

9. The method according to any one of claims 5 to 8, wherein said data indicative of the 3D structure of the optic disc comprises 3D point cloud data derived from stitching of said two or more 2D retinal images.

10. The method according to claim 9, wherein said 3D point cloud data is either dense or sparse.

11. The method according to any one of claims 5 to 10, wherein said processing of the image data comprises applying to said image data a 3D reconstruction data from video processing based on bundle adjustment algorithm.

12. The method according to any one of the preceding claims, wherein said analyzing of the data indicative of the 3D structure of the optic disc comprises: deriving from 3D point cloud data a mesh in the form of triangular structures with different areas; performing summation of areas of different triangular structures; and determining at least the surface area of the cup portion of the optic disc.

13. A method for monitoring conditions of an optic disc of an eye, the method comprising: providing data indicative of a 3D structure of the optic disc; and analyzing said data indicative of the 3D structure of the optic disc and deriving therefrom data indicative of a degree of applanation of a cup portion of the optic disc, thereby enabling to utilize said degree of applanation to determine the condition of the optic disc and classify said condition in association with at least one predetermined pathology, said data indicative of the degree of applanation of the cup portion of the optic disc comprising one or more of the following parameters: a ratio between a surface area of the cup portion of the optic disc and an optic disc area; a ratio between a volume of the cup portion and the optic disc area; and a ratio between a squared depth of the cup portion and the optic disc area.

14. The method according to claim 13, wherein the data indicative of the 3D structure of the optic disc includes 3D point cloud data.

15. The method according to claim 13 or 14, wherein said providing of the data indicative of the 3D structure of the optic disc comprises data communication with an image data provider to receive said data therefrom.

16. The method according to claim 13 or 14, wherein said providing of the data indicative of the 3D structure of the optic disc comprises receiving and processing image data indicative of two or more 2D retinal images acquired at different angles.

17. The method according to claim 16, wherein said two or more 2D retinal images are acquired by fundus camera system.

18. The method according to claim 16, wherein said two or more 2D retinal images are acquired by one or more of the following imaging techniques: stereo vision, structured light based imaging, and direct interferometric imaging.

19. The method according to claim 18, wherein said direct interferometric imaging technique is optical coherence tomography (OCT).

20. The method according to claim 19, wherein OCT data used to provide the data indicative of the 3D structure of the optic disc comprises 2D OCT images of several sections of the retina including one or more of the following sections: horizontal sections, vertical sections, and centralized sections.

21. The method according to claim 15, wherein said data indicative of the 3D structure of the optic disc comprises 3D point cloud data derived from stitching of said two or more 2D retinal images.

22. The method according to any one of claims 16 to 21, wherein said processing of the image data comprises applying to said image data a 3D reconstruction data from video processing based on bundle adjustment algorithm.

23. The method according to claim 13 or 14, wherein the data indicative of the 3D structure of the optic disc is obtained by a 3D photography system.

24. The method according to any one of claims 13 to 23, wherein said analyzing of the data indicative of the 3D structure of the optic disc comprises: deriving from 3D point cloud data a mesh in the form of triangular structures with different areas; performing summation of areas of different triangular structures; and determining surface areas of the optic disc and cup region thereof.

25. A monitoring system for monitoring conditions of optic disc of an eye, the monitoring system being configured as a computer system in data communication with retinal image data provider and comprising data input utility, memory and data processor, the data processor comprising: an analyzer configured and operable to analyze image data indicative of a 3D structure of the optic disc and determine at least a ratio between a surface area of a cup portion of the optic disc and an optic disc area, and an optic disc condition classifier configured and operable to utilize at least said ratio between the surface area of the cup portion and the optic disc area to determine the condition of the optic disc and classify said condition in association with at least one predetermined pathology.

26. The monitoring system according to claim 25, wherein the data processor is further configured to extract from said image data one or more of the following parameters: a ratio between a volume of the cup portion and the optic disc area, and a ratio between a squared depth of the cup portion and the optic disc area; and utilizes said one or more parameters to determine the condition of the optic disc.

27. The monitoring system according to claim 25 or 26, wherein the data processor further comprises a 3D image generator configured and operable to process image data comprising two or more 2D retinal images acquired with different angles and generate said data indicative of the 3D structure of the optic disc.

28. A retinal imaging system comprising: a fundus camera system and the monitoring system of any one of claims 14 to 27.

29. A monitoring system configured and operable for carrying out the method of any one of claims 1 to 24.