Field of the invention:

The present invention relates to measuring corneal astigmatism with it’s axis and assist in axis alignment of toric lenses in an eye during surgery. More particularly, the present invention relates to the method for measuring comeal astigmatism with it’s axis and simultaneously use the same data to assist in error free axis alignment of toric lens in the eye .

Background of the invention

An intraocular toric lens is a lens with different optical power and focal length in two orientations perpendicular to each other. Such a lens behaves like a combination of a spherical lens and a cylindrical lens. These intraocular toric lenses are used during surgery to correct astigmatism. The importance of selection of proper lens and proper axis alignment to get desirable outcome depends on different parameters of a particular eye. To measure these parameters requires multiple complex systems which are relatively expensive and unaffordable for most patients/examinees

Devices available for measuring eye parameters includes topographers, tomographers, synaptophore, keratometers, optical biometers, image guided systems and the like. These are either placcido based, wavefront based, OCT based or Scheimpflug based devices. Mainly these instruments require complex systems and hence may have multiple possibilities of failure. Also they require learning curve to understand and interpret the system.

Specifically, an US Patent 7976163B2 discloses system for measuring comeal topography of an eye. The system includes a group of first light sources arranged around a central axis, the group being separated from the axis by a radial distance defining an aperture in the group; a plurality of second light sources; a detector array; and an optical system adapted to provide light from the second light sources through the aperture to a cornea of an eye, and to provide images of the first light sources and images of the second light sources from the cornea, through the aperture, to the detector array. The optical system includes an optical element having a focal length, f. The second light sources are disposed to be in an optical path approximately one focal length, f, away from the optical element.

Another European Patent EP0395831 discloses a three-dimensional contour measuring apparatus is provided with first light beams (29) directed onto the surface (28) being measured. Reflections from the surface are received by a photo-detecting device (19) for generating electrical output signals which are processed to determine the radius of curvature of the surface (28) being measured. A higher spatial resolution can be achieved without changing the spacing of the array (11) of light points (30).

However, the result displayed by the available systems is not easily understandable by layman and in many cases even by an expert in the field. Hence ophthalmologist faces a difficulty while trying to educate/explain the patient/examinee about their eye condition. Also the cost required for setup and maintenance of these instruments is much high.

Accordingly, there exists a need to provide a method which determines assist in axis alignment of toric lens which overcomes the drawbacks of the prior art.

Objects of the invention:

An object of the present invention is to measure comeal astigmatism with it’s axis. . Another object of the present invention is to assist in axis alignment of toric lens in the eye.

Yet another object of the present invention is to measure total corneal astigmatism with its axis, pupil size, angles and also assist in axis alignment of toric lenses in the eye which is useful in different surgical and non-surgical procedures.

Still another object of the present invention is to evaluate suitability of a lens for each individual and outcome of surgical procedure.

One more object of the present invention is provide a novel , easy to use, reliable, non-cumbersome, examiner and examinee friendly system to measure total corneal astigmatism with its axis, pupil size, different angles.

Summary of the invention

Accordingly, the present invention provides a method for measuring comeal astigmatism with it’s axis and assisting in toric lens axis alignment in the eye using a module configured on a communication device. The method comprises capturing an image/video of the examinee eye in different pharmacological and light condition using a photographic device, processing the image by a processor of the module to make landmark structures more prominent and storing in the storage device of a communication module, measuring comeal power by the processor of the module by points illuminated by the LED lights on comeal front (anterior) and back (posterior) surface, measuring the comeal astigmatism with its axis by the processor by using diagonal points; calculating by the processor an axis of astigmatism, axis of alignment of toric lens, site of incision, landmark points, marking the axis of alignment of toric lens, site of incision, landmark points on the image captured to measure comeal astigmatism with it’s axis, displaying a silhouette of lens in center along the axis of alignment and saving the image and printing the processed images or transmitting the images to a display device for use during surgery in order to perform error free axis alignment of toric lenses.

Brief description of drawings

Figure 1 shows schematic representation of the device used to measure total corneal astigmatism with it axis , pupil sizes, different angles and also assist in alignment of toric lenses in eye;

Figure 2 shows a schematic representation of a workflow chart used for measurement of axis and power of anterior and posterior surface of cornea and finally total corneal astigmatism;

Figure 3 shows a schematic representation of a workflow chart used for measurement of apparent chord length mu, chord length mu. angle alpha, angle kappa angle lambda of the eye;

Figure 4 shows a schematic representation of a workflow chart used for measurement of size of cornea, size of pupil and pupil center shift in the eye;

Figure 5 shows the schematic representation of a workflow chart used for axis alignment of toric lenses;

Figure 6 shows reflection of LED lights by anterior and posterior corneal surfaces;

Figure 7 shows the through-focus image for exemplary measures of angle alpha, angle kappa and angle lambda in eye when enlightened;

Figure 8 shows the icon used for indicating chord mu;

Figure 9 shows an exemplary of coinciding chord mu icon with co-axially sighted corneal light reflex for checking the lens compatibility; Figure 10 shows the image for exemplary measure of size of cornea, size of pupil and pupil center shift in the eye; and

Figure 11 shows the simple method to compare variation of pupil size by bar graph.

Detailed description of the embodiments:

The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.

The present invention provides a method and system for measuring corneal astigmatism with its axis and assisting in alignment of the toric lenses in the eye. The method using the imaging device can capture the image/video of eye, store, and process which assist in alignment of toric lenses in eye. The method of the present invention provides an economical, easy to use and easy to interpret system for these measurements and assist in proper implantation of lenses. The method can also be used in demonstration and education of patient/examinee about their eye condition.

Referring now to figures 1, there is shown a system (100) for measuring total corneal astigmatism with it axis, pupil sizes, different angles and which assist in alignment of toric lenses in eye, in accordance with the present invention.

The system (100) comprises a photographic device (102), a processing unit (103), a display unit (104), a printing device (105), and communication network (106) connecting all the unit wirelessly to each other. In an embodiment, the photographic device (102) comprises any one of a camera, lenses and light source configured around the lens or camera. In an embodiment, the light source is octagon shaped unit having at least one array of LED configured thereon. In preferred embodiment, the light source is an illuminating unit having octagon shaped unit with colored LEDs arranged in multiple circular like pattern (107).

The photographic device (102) is capable of being operated by an examiner/opthmalogist to capture an image of an eye (101) of an examinee. The captured image of the eye is then saved as an electric signal and shared to a processing unit (103) through a wired or wireless communication network (106).

A processing unit (103) is configured to act as means for reading image/video data stored in the storage device and perform processing thereon. In an embodiment, the processing unit (103) is any one of a computer, laptop, mobile or tablet with/without a display. The keyboard and a mouse acts as signal input means for the processing unit (103).

Further, the display unit (104) for example, a monitor (104) operatively controlled by the processing unit (103) and display image/video data transmitted from the storage device to the processing unit (103).

Further, the printing device (105) is operatively controlled by the processing unit (103) and provides output calculation results and pictures.

Referring now to figure 2, there is shown a flowchart of a method (200) for measurement of axis and power of anterior and posterior surface of cornea of the eye (101) of the examinee. The method (200) is described in conjunction with system (100). The method (200) works in conjunction with a module configured in a communication device, for example, a computing device, laptop, tablet and mobile phone. The method (200) comprises capturing image/video of the eye of the examinee in a condition with different illumination through a photographic device (102). The method (200) further comprises selecting the preferred image/video by the processing unit (103).

The method (200) furthermore comprises calculating the comeal power. Specifically, the comeal power is calculated by using images of the anterior surface and posterior surface of the cornea. The combination of the comeal power, the anterior surface and posterior surface provides comeal topography map.

The method (200) furthermore comprises calculating the comeal axis. Specifically, the comeal axis is calculated by using images of the anterior surface and posterior surface of the cornea which gives final comeal axis.

Specifically, the processing unit (200) process the information and presents as a colored topographic map in a hill and valley pattern and stored in the storage device.

The method (200) comprises calculating comeal power by a processor of the communication device having module configured therein using images of the anterior surface and posterior surface of the cornea taken by the LED light source. The comeal power is also represented in coloured topography map on the display of the communication device.

The method (200) furthermore comprises calculating final comeal of astigmatism by the module using images of anterior and posterior surface of cornea which give final comeal axis of. The comeal axis of astigmatism is also calculated by comparing identical diagonal points of different zones. As described earlier, the method (200) of the present invention works in conjunction with a module configured on a communication device such laptop, computer, tablet and the like. The doctor/surgeon opens the app in his communication device and then imports the captured and processed image of the eye taken by the photographic device in to the module of the communication device. The surgeon then enters the value of axis of site on incision and value of axis of alignment of the toric lens in the module.

The surgeon then submits the keratometry data and increases size of the picture of the eye and fix it onto centre of the image. Then the surgeon then increases size of the axis marker of the image to coincide with cornea of the eye. Thereafter, the surgeon adjust size of the lens silhouette and rotate it in axis of alignment of toric lens.

The surgeon further marks the landmark points on the image and save the image. In an embodiment, the image can be rotated and magnified. These saved images can be then displayed on the monitor or printed and used as reference during axis alignment of the toric lens in OT during surgery..

Referring now to figure 3, there is shown a method (300) for measurement of apparent chord length mu, chord length mu, angle alpha, angle kappa and angle lambda of the eye (101). The method (300) is described in conjunction with system (100).

The method (300) comprises capturing coaxially sighted comeal light reflex image/video of the examinee eye (101) using a photographic device (102) and stored in the storage device.

The method (300) further comprises selecting the preferred image/video to be used for analysis. The method (300) furthermore comprises calculating the apparent Chord Mu.

The method (300) furthermore comprises calculating angle Lambda i.e. pulillary axis and line of sight of the eye using ACD and integrated formulas.

The method (300) moreover comprises calculating Chord Mu and angle Kappa i.e. pupillary axis and visual axis and angle alpha i.e. optical axis and visual axis of te eye of the examinee using ACDs, lens thickness, nodal points and integrated formulas.

Referring now to figure 4, there is shown a method (400) for measurement of size of cornea, size of pupil and pupil center shift in the eye. The method (400) is described in conjunction with system (100).

The method (400) comprises capturing image/video of the examinee eye in different pharmacological and light conditions and stored in the storage device.

The method (400) further comprises selecting the preferred image/video.

The method (400) furthermore comprises calculating size and center of the cornea, the pupil size (Photopic), and locating center of pupil.

The method (400) moreover comprises calculating pupil size (mesopic/dilate) and locating center for pupil.

The method (400) also comprises calculating center shift of the pupil using scotopic, photopic and mesopic data and the same is displayed as bar chart.

The information obtained using the method (400) can be used for easy comparison by the surgeon, easy interpretation and for education of the patients. Referring now to figure 5, there is shown a flowchart of a method (500) for toric axis alignment in the eye, in accordance with the present invention. The method works in conjunction with the module for assisting a doctor/surgeon in alignment of the toric in the eye. The module is configured on a communication device such laptop, computer, tablet and the like.

The method (500) comprises capturing the image/video of the examinee eye captured in different pharmacological and light condition using the photographic device. In an embodiment, the different pharmalogical condition includes examination of eye when a pupil of the eye is normal and dilated. Further, the image/video of the eye is taken in different light condition using the photographic device.

The photographic device for capturing the image/video includes a camera, addressable LEDs as light source configured around the lens or camera. In an embodiment, the LED light source is octagon shaped unit having at least one array of addressable LED configured thereon. In preferred embodiment, the light source is an illuminating unit having octagon shaped unit with colored LEDs arranged in multiple circular like pattern. Multiple pictures of the eyes are taken in different color and pattern combination of LED lights. For example, in an embodiment, out of multiple circular LEDs, either one or multiple array is made on. Similarly, in another embodiment, LEDs of either side are made on while taking the image and so on. The LEDs are lighted in different pattern and colours during capturing the picture of the eye.

The method (500) further comprises processing the image by a processor of the communication device to make landmark structures more prominent and storing in the storage device of the communication module. The landmark structure means identifying prominent blood vessels, spots on iris and sclera which are easy to identify in color image of the eye. Specifically, processing of an image is done by processor of the module which is configured to adjust different features of coloured picture like exposure, brilliance, highlight, shadows, contrast brightness, black point, saturation, vibrancy, warmth, tint, sharpness, definition, noise reduction, vignette and the like.

The method (500) furthermore comprises calculating and marking by the processor an axis of alignment of toric lens, site of incision, landmark points. These parameters are also marked on the image and saved in the memory of the communication device.

The module includes a 360 degree marking tool. The tool has data entry feature for axis of alignment, site of incision. The tool displays axis of landmark points. Using the module, in the center of 360 degree marking ring image of lens is incorporated. The size of this image can be changed and rotated by keys or control buttons of the communication device.

The method (500) moreover comprises displaying a silhouette of lens in center along the axis of alignment and saved. Silhouette of the lens means image of the lens which is displayed on the display monitor of the communication device. The module is configured to increase the size of the lens and rotate the same.

The method (500) also comprises printing the processed images or transmitting the images to a display device, for example, on a monitor or other devices for use during surgery in order to perform error free axis alignment of toric lenses.

The image can be stored and displayed on the display device and can be used by the examiner for operative procedures or for educating the examinee/patient about the suitability of their eye for multifocal lens and refractive procedures. Referring now to figure 6, there is shown a schematic drawing showing reflection of LED lights as a light source by anterior and posterior comeal surfaces. Specifically, each LED light of the light source produces two images on cornea, one brighter (108) from anterior surface of the cornea and other fainter (109) from posterior surface of cornea. In an embodiment, the figure 6A shows LED light source.

In another embodiment, for calculation of axis and total power of cornea, a photokeratoscopy, computerised video keratoscopy along with computer based image processing system ( through AI and digital image pixel) is used.

The axis and total power of cornea is measured by measuring position of image by computer based image processing system. The information from comeal image is automatically presented in colored comeal topography map in a hill and valley pattern.

Referring now to figure 7, there is shown a through-focus image for exemplary measures of angle alpha, angle kappa and angle lambda in eye when enlightened, in accordance with the present invention.

Specifically, the angles are described where a cross sectional view of an eye is represented by the cornea (110), pupil (111) and lens (112). The angle between pupillary axis (113) and visual axis (114) is angle kappa (K) (115), the angle between pupillary axis (113) and line of sight (116) is angle lambda (l) (117), and the angle between optical axis (118) and visual axis (114) is angle alpha (a) (119).

The calculation of apparent chord mu is performed by selecting a captured picture or video. Specifically, by using anterior chamber depth (ACD) and integrated formula, angle lambda (l) (117) is calculated, which is the angle between pupillary axis and line of sight. Further, the anterior chamber depth (ACD), lens thickness, nodal point and integrated formula together calculate the chord mu, angle kappa (K) (115), which is the angle between the pupillary axis. Furthermore, the visual axis and angle alpha (a) (119) is the angle between optical axis and visual axis. These calculations are carried out it processing unit (103) as described hereinabove.

Referring now to figure 8, there is shown system (100) in accordance with an embodiment of the present invention. In this embodiment, the icon used for chord mu is made of three concentric rings of three different colors. The current embodiment uses a red color for the outermost ring (120), a yellow color for the middle ring (121) and a green color for the innermost ring (122). The colors may be same or different in different embodiments of the invention.

Referring now to figure 9, there is shown another embodiment of the system (100) for alignment of chord mu icon (123) with corneal light reflex image of an eye of an examinee. The comeal light reflex image of an eye of an examinee stored in the storing device is selected, optic size (124) and pupil size (125) can be adjusted by moving, rotating or zooming in or out the image. Finally coinciding the co axial sighted comeal light reflex (126) with the chord mu icon (123) developed in the present invention is used to check the compatibility of the lens. The picture comparing comeal light reflex (126) and chord Mu icon (123) can be saved in the storing device, retrieved back to any display unit and can be magnified. The position of the comeal light reflex (126) on the chord mu icon (123) decides whether the lens is suitable for the examinee’s eye or not. If the comeal light reflex (126) coincides with the innermost circle (122) on the chord mu icon (123), the lens under test may be suitable for the examinee’s eye. If the comeal light reflex (126) does not coincides with the innermost circle (122) on the chord mu icon (123), the lens under test may not be suitable for the examinee’s eye.

This image can be stored and displayed on the display device and can be used by the examiner for operative procedure or for educating the examinee about his eye suitability for the lens under test. Referring now to figure 10, for calculation of size of cornea, size of pupil and pupil center shift, picture/video captured by the photographic device (102) is selected. The size of cornea (127) and center of optical axis (129) is marked and calculated. Further, the pupil size in bright light (photopic) (128) and pupil center

(130) is calculated. The pupil size in dim light (scotopic) or pharmacologically dilated (131) and pupil center (132) is calculated. The distance between these two pupil centers- bright light (130) and dilated pupil (132) is calculated (133) which is a pupil center shift. More specifically, the pupil size in different conditions are displayed in bar and picture for comparison, interpretation by surgeon, to educate the patient and to share data.

The size of cornea (127) has optical center (129). The pupil size (128) in bright light has pupillary center (130). The pupil size in low light condition (dilated)

(131) has center of pupil (132). The pupil center shift (133) which is the distance between (130) and (132) is calculated.

Referring now to figure 11, an example of one of the embodiment of the present invention for representation of pupil size in different conditions by bar diagram is shown, wherein (136) represents size of pupil in millimeters, (137) represents pupil size in bright light (photopic), (138) represents pupil size in normal light, (139) represents pupil size in dim light (mesopic) or pharmacologically dilated pupil, (134) recommends upper limit for the procedure, (135) recommends lower limit for the procedure and (140) represents pupil center shift.

The image can be stored and displayed on the display device and can be used by the examiner for operative procedures or for educating the examinee/patient about the suitability of their eye for multifocal lens and refractive procedures

Advantages of the invention 1. The method (100) of the present invention is to measure comeal astigmatism it’s axis and assists in alignment of toric lenses in the eye. The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the scope of the present invention.