Curvature of field transformation of OCT images during vitreoretinal surgery

Curvature of field transformation of OCT images during ophthalmic surgery may be performed with an OCT scanning controller that interfaces to an OCT scanner used with a surgical microscope. Real-time OCT images may be acquired by the OCT scanner, while an anamorphic transformation is applied to the OCT images to match the curvature of field for optical images viewed using the surgical microscope. The transformed OCT images may be displayed during surgery.

BACKGROUND

Field of the Disclosure

The present disclosure relates to ophthalmic surgery, and more specifically, to curvature of field transformation of optical coherence tomography (OCT) images during vitreoretinal surgery.

Description of the Related Art

In ophthalmology, eye surgery, or ophthalmic surgery, saves and improves the vision of tens of thousands of patients every year. However, given the sensitivity of vision to even small changes in the eye and the minute and delicate nature of many eye structures, ophthalmic surgery is difficult to perform and the reduction of even minor or uncommon surgical errors or modest improvements in accuracy of surgical techniques can make an enormous difference in the patient's vision after the surgery.

Ophthalmic surgery is performed on the eye and accessory visual structures. More specifically, vitreoretinal surgery encompasses various delicate procedures involving internal portions of the eye, such as the vitreous humor and the retina. Different vitreoretinal surgical procedures are used, sometimes with lasers, to improve visual sensory performance in the treatment of many eye diseases, including epimacular membranes, diabetic retinopathy, vitreous hemorrhage, macular hole, detached retina, and complications of cataract surgery, among others.

During vitreoretinal surgery, an ophthalmologist typically uses a surgical microscope to view the fundus through the cornea, while surgical instruments that penetrate the sclera may be introduced to perform any of a variety of different procedures. The surgical microscope provides imaging and optionally illumination of the fundus during vitreoretinal surgery. The patient typically lies supine under the surgical microscope during vitreoretinal surgery and a speculum is used to keep the eye exposed. Depending on a type of optical system used, the ophthalmologist has a given field of view of the fundus, which may vary from a narrow field of view to a wide field of view that can extend to peripheral regions of the fundus.

In addition to viewing the fundus, surgical microscopes may be equipped with optical coherence tomography (OCT) scanners to provide additional information about portions of eye tissue involved with the vitreoretinal surgery. The OCT scanner may enable imaging below a visible surface of the eye tissue during vitreoretinal surgery. However, the curvature of field of OCT images may be different than microscopy optical images viewed by the surgeon.

SUMMARY

In one aspect, a disclosed method is for performing ophthalmic surgery using curvature of field transformation of OCT images. The method may include viewing an interior portion of an eye of a patient using a surgical microscope and an ophthalmic lens generating an optical image of the interior portion of the eye. The method may also include sending a command to an OCT scanning controller coupled to the surgical microscope to generate first scan data from the interior portion of the eye. In the method, the OCT scanning controller is in communication with an OCT scanner enabled for acquiring the first scan data. In the method, the OCT scanning controller is enabled for receiving the first scan data from the OCT scanner. In the method, the first scan data are usable to generate an en face view of the interior portion of the eye. Based on optical characteristics of the surgical microscope and the ophthalmic lens, in the method, the OCT scanning controller is further enabled for applying an anamorphic transformation to the first scan data to generate second scan data that matches a curvature of field of the optical image in the en face view, and causing the second scan data to be displayed in the en face view.

In any of the disclosed embodiments of the method, the second scan data may be displayed in an ocular of the surgical microscope. In any of the disclosed embodiments of the method, the second scan data may be displayed in an external display.

In any of the disclosed embodiments of the method, the first scan data may be received as a video signal, while the second scan data may be displayed as a video signal.

In any of the disclosed embodiments of the method, applying the anamorphic transformation may further include aligning first tissue features in the first scan data with corresponding second tissue features in the optical image to determine the curvature of field. In any of the disclosed embodiments of the method, the first tissue features and the second tissue features may include retinal blood vessels.

In any of the disclosed embodiments of the method, the optical characteristics may include anamorphic distortion of an objective lens included in the surgical microscope. In any of the disclosed embodiments of the method, the optical characteristics may include anamorphic distortion of the ophthalmic lens.

In any of the disclosed embodiments, the method may include receiving an indication of desired tissue layers captured in the first scan data, and generating the second scan data to image only the desired tissue layers in the en face view.

In another aspect, a disclosed OCT scanning controller performs curvature of field transformation of OCT images during ophthalmic surgery. The OCT scanning controller may include a processor having access to memory media storing instructions executable by the processor. In the OCT scanning controller, the instructions may be executable for receiving a first command to generate first scan data from an interior portion of an eye of a patient, and sending a second command to an OCT scanner to acquire the first scan data via a surgical microscope and an ophthalmic lens. In the OCT scanning controller, the surgical microscope and the ophthalmic lens may also be used to generate an optical image of the interior portion of the eye. In the OCT scanning controller, the instructions may also be executable for receiving the first scan data from the OCT scanner. In the OCT scanning controller, the first scan data may be usable to generate an en face view of the interior portion of the eye. Based on optical characteristics of the surgical microscope and the ophthalmic lens, in the OCT scanning controller, the instructions may also be executable for applying an anamorphic transformation to the first scan data to generate second scan data that matches a curvature of field of the optical image in the en face view, and causing the second scan data to be displayed in the en face view.

In any of the disclosed embodiments of the OCT scanning controller, the instructions for causing the second scan data to be displayed in the en face view may include instructions for causing the second scan data to be displayed in an ocular of the surgical microscope.

In any of the disclosed embodiments of the OCT scanning controller, the instructions for causing the second scan data to be displayed in the en face view may include instructions for causing the second scan data to be displayed in an external display.

In any of the disclosed embodiments of the OCT scanning controller, the first scan data may be received as a video signal, while the second scan data may be displayed as a video signal.

In any of the disclosed embodiments of the OCT scanning controller, the instructions for applying the anamorphic transformation may further include instructions for aligning first tissue features in the first scan data with corresponding second tissue features in the optical image to determine the curvature of field. In any of the disclosed embodiments of the OCT scanning controller, the first tissue features and the second tissue features may include retinal blood vessels.

In any of the disclosed embodiments of the OCT scanning controller, the optical characteristics may include anamorphic distortion of an objective lens included in the surgical microscope. In any of the disclosed embodiments of the OCT scanning controller, the optical characteristics may include anamorphic distortion of the ophthalmic lens.

In any of the disclosed embodiments, the OCT scanning controller may further include instructions for receiving an indication of desired tissue layers captured in the first scan data, and generating the second scan data to image only the desired tissue layers in the en face view.

Additional disclosed embodiments include an OCT scanner, a surgical microscope, and an image processing system.

DESCRIPTION OF PARTICULAR EMBODIMENTS

As used herein, a hyphenated form of a reference numeral refers to a specific instance of an element and the un-hyphenated form of the reference numeral refers to the collective element. Thus, for example, device ‘12-1’ refers to an instance of a device class, which may be referred to collectively as devices ‘12’ and any one of which may be referred to generically as a device ‘12’.

As noted above, during vitreoretinal surgery a surgeon may view the fundus of an eye of a patient using a surgical microscope, for example, in conjunction with an ophthalmic lens for viewing through the cornea, such as a contact or non-contact lens. In order to perform any of a variety of surgical procedures, the surgeon may desire to optically scan certain portions of the fundus to generate profile depth scans of the corresponding eye tissue, such as by using an OCT scanner. The profile depth scans may reveal information about eye tissue that is not readily visible from optical images generated by the surgical microscope. The profile depth scans may be point scans (A-scan), line scans (B-scan), or area scans (C-scan). An image from a B-scan will image the depth of eye tissue along a line, while a C-scan results in 3-dimensional (3D) data that can be sectioned to provide various views, including an en face view from the optical view perspective, but which can be generated at various depths and for selected tissue layers.

Although OCT scanners have been integrated with the optics of surgical microscopes, the imagery that can be provided using OCT may be different in certain aspects than the optical images that the surgeon views intraoperatively. For example, because of the optical properties of various ophthalmic lenses used to image interior portions of the eye, the curvature of field of the optical images may be substantially different than OCT images acquired for the same tissue. Such disparities in the curvature of field may create difficulties for the surgeon to adapt to the differing views. While the human brain is adept at adapting to a given visual distortion, adapting to two different curvatures of field for the same image is more difficult and potentially prone to errors, such as errors in perceiving a depth of eye tissue, which can be crucial during surgery. In particular, en face OCT imaging will experience the most significant distortions due to disparate curvature of field as compared to the optical image.

The present disclosure relates to curvature of field transformation of OCT images during vitreoretinal surgery. The methods and systems for curvature of field transformation of OCT images during vitreoretinal surgery disclosed herein may enable the surgeon to view en face OCT images that are corrected to match a curvature of field of the optical image viewed by the surgeon using the surgical microscope.

As will be described in further detail, curvature of field transformation of OCT images during vitreoretinal surgery disclosed herein is performed using an OCT scanning controller that is integrated with the OCT scanner and the surgical microscope. The OCT scanning controller may send commands to control operation of the OCT scanner, including for positioning as indicated by a user, typically the surgeon. The OCT scanning controller may receive user input and may communicate with the OCT scanner to acquire first scan data that is usable to generate an en face view of an interior of an eye of a patient. The OCT scanning controller may apply an anamorphic transformation to the first scan data to generate second scan data that matches a curvature of field of the optical image.

Referring now to the drawings,FIG. 1is a block diagram showing a surgical microscopy scanning instrument100. Instrument100is not drawn to scale but is a schematic representation. As will be described in further detail, instrument100may be used during vitreoretinal surgery to view and analyze a human eye110. As shown, instrument100includes surgical microscope120, OCT scanning controller150, external display152, and OCT scanner134. Also shown inFIG. 1are imaging system140, ophthalmic lens112, as well as surgical tool116and illuminator114.

As shown, surgical microscope120is depicted in schematic form to illustrate optical functionality. It will be understood that surgical microscope120may include various other electronic and mechanical components, in different embodiments. Accordingly, objective124may represent a selectable objective to provide a desired magnification or field of view of the fundus. Objective124may receive light from the fundus of eye110via ophthalmic lens112that rests on a cornea of eye110. It is noted that various types of ophthalmic lenses112may be used with surgical microscope120, including contact lenses and non-contact lenses. To perform vitreoretinal surgery, various tools and instruments may be used, including tools that penetrate the sclera, represented by surgical tool116. Illuminator114may be a special tool that provides a light source from within the fundus of eye110.

InFIG. 1, surgical microscope120is shown with a binocular arrangement with two distinct but substantially equal light paths that enable viewing with binoculars126that comprise a left ocular126-L and a right ocular126-R. From objective124, a left light beam may be split at beam splitter128, from where imaging system140and left ocular126-L receive the optical image. Also from objective124, a right light beam may be split at partial mirror129, which also receives sample beam130from OCT scanner134, and outputs measurement beam132to OCT scanner134. Partial mirror129also directs a portion of the right light beam to right ocular126-R. Display122may represent an opto-electronic component, such as an image processing system that receives the data from OCT scanning controller150and generates image output for left ocular126-L and right ocular126-R, respectively. In some embodiments, display122includes miniature display devices that output images to binoculars126for viewing by the user. It is noted that the optical arrangement depicted inFIG. 1is exemplary and may be implemented differently in other embodiments.

InFIG. 1, OCT scanning controller150may have an electrical interface with display122, for example, for outputting display data. In this manner, OCT scanning controller150may output a display image to display122that is viewed at binoculars126. Because the electrical interface between imaging system140and OCT scanning controller150may support digital image data, OCT scanning controller150may perform image processing in real-time with relatively high frame refresh rates, such that a user of surgical microscope120may experience substantially instantaneous feedback to user input for controlling the selected portion of eye110for scanning, as well as other operations. External display152may output similar images as display122, but may represent a stand-alone monitor for viewing by various personnel during vitreoretinal surgery. Display122or external display152may be implemented as a liquid crystal display screen, a computer monitor, a television or the like. Display122or external display152may comply with a display standard for the corresponding type of display, such as video graphics array (VGA), extended graphics array (XGA), digital visual interface (DVI), high-definition multimedia interface (HDMI), etc.

With the binocular arrangement of surgical microscope120inFIG. 1, imaging system140may receive a portion of the left light beam that enables imaging system140to independently process, display, store, and otherwise manipulate light beams and image data. Accordingly, imaging system140may represent any of a variety of different kinds of imaging systems, as desired.

As shown, OCT scanner134may represent an embodiment of various kinds of OCT scanners. It is noted that other types of optical scanners may be used with the arrangement depicted inFIG. 1. OCT scanner134may control output of sample beam130and may receive measurement beam132that is reflected back in response to photons of sample beam130interacting with tissue in eye110. OCT scanner134may also be enabled to move sample beam130to the selected location indicated by the user. OCT scanning controller150may interface with OCT scanner134, for example, to send commands to OCT scanner134indicating the selected location to generate scan data, and to receive the scan data from OCT scanner134. It is noted that OCT scanner134may represent various types of OCT instruments and configurations, as desired, such as but not limited to time domain OCT (TD-OCT) and frequency domain OCT (FD-OCT). In particular, the scan data generated by OCT scanner134may include two-dimensional (2D) scan data of a line scan and three-dimensional (3D) scan data for an area scan. The scan data may represent a depth profile of the scanned tissue that enables imaging below a visible surface within the fundus of eye110.

In operation of instrument100, the user may view the fundus of eye110using binoculars while vitreoretinal surgery is performed on eye110. The user may provide user input to OCT scanning controller150to initiate an OCT scan. OCT scanning controller150may, in turn, communicate with OCT scanner134to control scanning operations and perform a real-time OCT scan to generate first scan data. However, the first scan data generated by OCT scanner134intraoperatively may not match a curvature of field of the optical image viewed, as discussed previously. Therefore, instead of displaying the first scan data at display122, OCT scanning controller150may apply an anamorphic transformation to the first scan data to generate second scan data matching the curvature of field. The anamorphic transformation may be an affine transform, or another type of transform. Various methods may be used to determine parameters for the anamorphic transformation. In one embodiment, optical properties of instrument100, such as known anamorphic distortion of objective124or ophthalmic lens112, among other optical components, may be determined and used for the anamorphic transformation. In some embodiments, certain tissue features in the optical image, such as retinal blood vessels, may be used to align corresponding tissue features in the first scan data (the raw OCT image) or to determine parameters of the anamorphic transformation being applied.

Modifications, additions, or omissions may be made to surgical microscopy scanning instrument100without departing from the scope of the disclosure. The components and elements of surgical microscopy scanning instrument100, as described herein, may be integrated or separated according to particular applications. Surgical microscopy scanning instrument100may be implemented using more, fewer, or different components in some embodiments.

Referring now toFIG. 2, a block diagram illustrating selected elements of an embodiment of OCT scanning controller150, described above with respect toFIG. 1, is presented. In the embodiment depicted inFIG. 2, OCT scanning controller150includes processor201coupled via shared bus202to memory media collectively identified as memory210.

OCT scanning controller150, as depicted inFIG. 2, further includes communication interface220that can interface OCT scanning controller150to various external entities, such as OCT scanner134or imaging system140, among other devices. In some embodiments, communication interface220is operable to enable OCT scanning controller150to connect to a network (not shown inFIG. 2). In embodiments suitable for resolution enhancement of OCT images during vitreoretinal surgery, OCT scanning controller150, as depicted inFIG. 2, includes display interface204that connects shared bus202, or another bus, with an output port for one or more displays, such as display122or external display152.

InFIG. 2, memory210encompasses persistent and volatile media, fixed and removable media, and magnetic and semiconductor media. Memory210is operable to store instructions, data, or both. Memory210as shown includes sets or sequences of instructions, namely, an operating system212, and a curvature of field control application214. Operating system212may be a UNIX or UNIX-like operating system, a Windows® family operating system, or another suitable operating system.

Referring now toFIG. 3, a flow chart of selected elements of an embodiment of a method300for curvature of field transformation of OCT images during vitreoretinal surgery, as described herein, is depicted in flowchart form. Method300describes steps and procedures that may be performed while surgical microscopy scanning instrument100is operated to view the fundus of an eye and perform surgical procedures based on the view of the fundus. Accordingly, at least certain portions of method300may be performed by curvature of field control application214. It is noted that certain operations described in method300may be optional or may be rearranged in different embodiments. Method300may be performed by curvature of field control application214to interact with a surgeon or other medical personnel, referred to herein as a “user”.

Prior to method300, it may be assumed that surgical microscopy scanning instrument100is being used to view an interior portion of an eye of a patient, such as described inFIG. 1. Then, method300may begin, at step302, by receiving a first command to generate first scan data usable to generate an en face view of the interior portion of the eye. The first scan data are C-scans (volumetric scans) of the interior portion of the eye. At step304, a second command is sent to an OCT scanner to acquire the first scan data via the surgical microscope and an ophthalmic lens also used to generate an optical image of the interior portion of the eye. At step306, the first scan data may be received from the OCT scanner. At step308, based on optical characteristics of the surgical microscope and the ophthalmic lens, an anamorphic transformation may be applied to the first scan data to generate second scan data that matches a curvature of field of the optical image in the en face view. The second scan data are also C-scans (volumetric scans) of the interior portion of the eye. Additionally, it is noted that the anamorphic transformation in step308is dependent on a number of variables and factors associated with instrument100. For example, the anamorphic transformation is dependent on a microscope magnification or selection of a given objective124, as well as on a type of ophthalmic lens112used. The anamorphic transformation may also be dependent on a distance between an optical element, such as a non-contact lens used for ophthalmic lens112, and the eye. Thus, upon a change in such operative variables, at least step308in method300may be repeated to refresh the second scan data.

At step310, the second scan data may be caused to be displayed in the en face view. It is noted that the second scan data are displayed in addition to the optical image provided by the surgical microscope that is a live optical view of the interior portion of the eye. Various other OCT operations on the en face view of the second scan data may be performed, such as selection of certain depths or depth ranges for viewing. In some embodiments, the OCT scanning controller may be enabled to image only desired tissue layers in the en face view of the second scan data, responsive to an indication by the user to select the desired tissue layers. The second scan data may be displayed in the en face view at binoculars126or at external display152or both.

As disclosed herein, curvature of field transformation of OCT images during ophthalmic surgery may be performed with an OCT scanning controller that interfaces to an OCT scanner used with a surgical microscope. Real-time OCT images may be acquired by the OCT scanner, while an anamorphic transformation is applied to the OCT images to match the curvature of field for optical images viewed using the surgical microscope. The transformed OCT images may be displayed during surgery.