DESC:
FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

Complete Specification
(See section 10 and rule 13)

1.Title of the Invention :

New procedure of Identification and documentation of the exact Cyclotorsion Angle involved in a Human Eye with a unique Calculation methodology using the Virtual Toric Align Software during Eye Surgeries

2. Applicant Name : Appasamy Associates

Nationality : Indian

Address : No.20, 1st Street, SBI Officer's Colony,

P.H.Road, Arumbakkam, Chennai-600106

3. Preamble to the Description :

The following specification particularly describes the invention and the manner in which it is to be performed.

Description
Field of the invention
This invention relates to the field of cataract surgery which involves implantation of an intra-ocular lens (IOL) as a replacement for the Cataractous Natural Lens.
Background of the invention
Eye movement and improper positioning of the IOL during surgery can affect the outcome of a surgery to a great extent. Toric Intra Ocular Lens are used to correct astigmatism which aims to provide postoperative spectacle independence. To obtain a successful result after surgery, it is imperative that determination of astigmatism should be accurate. Further the IOL should be aligned with the target axis. The implanted Toric IOL needs to be stable without rotation. A 15 degree angle or error results in about 50% reduction in the magnitude of correction of astigmatism. Therefore Surgeons have the onerous task of placing the Toric IOL axis exactly on the astigmatism axis. Any misalignment will result in a compounding of error.
A major reason for errors in axis marking is due to position-induced cyclotorsion error. This error occurs when patient move from a seated / upright position to a supine position. Previous studies have found that these postural changes can induce a ocular cyclotorsional effect of 0.4 to 4.2 degrees (range 0 to 16 degrees). Although a small angle of cyclotorsion will not significantly affect results, a larger rotational error can lead to unacceptable outcomes. To compensate for ocular cyclotorsion, preoperative marking is done at the 0 and 180 degree positions on the corneal limbus under slit lamp biomicroscopy. This is a horizontal reference which is used during the surgery, when the patient is in a supine position. This technique does not guarantee or offer a perfect result.
Axial misalignment is therefore the main cause for residual astigmatism after toric IOL implantation. The most important factor for this axial misalignment is the ocular cylcotorsion.
The prior art has many defects. There is no accurate method of determining the exact cyclotorsion angle. Further marking the 0 – 180 axis on the patient’s eye can cause injury. Moreover, any improper marking on the eye together with a parallax error caused due to the thickness of the marked line can cause incorrect placement of the Toric IOL.
This invention discloses a safe, easy to implement and accurate method of determination of the exact cyclotorsion angle on the Surgical Table and also a reverse methodology to reconfirm and verify the applied Cyclotorsion compensation Angle's accuracy level.
Summary of the invention
A prominent landmark feature is identified from the Patient's Eye as a Landmark Angle from the Slit lamp scale while preoperative observation of the Patient's selected Eye, by alignment of a thin slit beam inline with the selected blood vessel after fixating the central reference of the VTA (Virtual Toric Align) software crosswire coinciding with the Central Purkinje image reflection on the Cornea surface, the location of which is noted from the scale of the slit-lamp in degrees. This is considered to be the reference to compensate for cyclotorsion effect in the lying position of the Patient on the operation table during the Surgical procedure. A circular angle-scale as a video overlay appears on the display of the newly developed VTA ( Virtual Toric Align software ) which works in the Toric MAX Equipment which will guide the Surgeon in real time for indicating the Toric IOL placement location with due compensation of the Cyclotorsion effect for that particular Patient's eye.
Detailed description of the invention with respect to the drawings
Fig 1 and Fig 2 : The first step involves identification of a prominent landmark feature from the Patient’s eye as a landmark angle, the location of which is noted from the scale of the slit-lamp. For this purpose a novel virtual toric alignment software is designed. This software is designed to overlay the axis using thin, accurate and visible lines of three distinct colours on the surgical video obtained from Operating Microscope CCD camera. This facilitates the Operating Surgeon with the three axis, viz: Toric IOL placement axis, 0-180 axis and landmark axis located as per the slit-lamp reference angle (for compensating cyclotorsion effect) on the circular angle-scale as a video overlay.
Fig 3 : Once all these angle data are fed in the respective Patient database then the “SAVE” key and “TORIC OVERLAY” may be pressed to finalize all the three axis locations, which result in the creation of a Toric Overlay to appear on the Surgical video from the Microscope CCD Camera connected to the Non-contact Real-time Intraocular Toric IOL Alignment and marking system (earlier Indian Patent application number 201641001325).
Surgical Technique:
The Surgeon performs his Cataract Surgery as usual but on four different occasions he needs to gaze at the display of this Non-contact Real-time Intraocular Toric IOL Alignment and marking system equipment for the following Steps to be accomplished:
Step 1:
The operating microscope optical head is fixed based on whether the Patient is operated from Superior or Temporal or Supra temporal approach by the Surgeon accordingly to suit the comfort zone. After this fixation reference, the Landmark identification noted in the slit-lamp needs to be identified on the Operating table by the Surgeon visually looking at the Video insert window in the VTA software. Firstly, The Microscope has to be set at its lowest magnification setting, and later, the Slider provided in the software is moved to exactly locate the white line in the Video Overlay representing the 0 -180 axis in correlation to the Canthus to Canthus reference of the operating Eye or to orient inline with the major horizontal Oval shaped Cornea's Limbal arcade. To accomplish this process the Key indicating " Move slider click here once to fix 0- -180 " button is pressed to freeze this as a reference axis, once clicked then the same key will now indicate " Reset Toric overlay to its home position " this is to facilitate the operating Surgeon to realign the 0-180 reference if it falls short or overshoots from the required exact Canthus to Canthus alignment or the maximum length horizontal diameter white to white end of the Limbal arcade boundary of the Cornea to which it has to be inline and fixed.
Step 2:
The central crosswire or the RED dot central reference mark in the Toric Overlay has to be positioned in such a way to coincide with the naturally formed central Purkinje image reflection from the anterior Cornea which facilitates the Surgeon for Central fixation of the Eye ball without any high tech Eye tracking systems.
After accomplishing the central fixation, the software slider is again moved to coincide the Orange coloured overlay line which represents the Landmark axis corresponding to the slit-lamp Angle data fed to the software which is the identified landmark in the upright position of the Patient in the sitting posture observed and its location noted during the Slit-lamp examination. Since most of the Patient's eyes tend to rotate in lying position on the Surgical table, compared to the sitting-up position, Toric overlay markings needs to compensated for this cyclo-torsion effect.
Fig 4: Software slider is again moved from its central home position (After fixating the 0 - 180 ) to coincide the Orange coloured overlay line which represents the Landmark axis corresponding to the slit-lamp observed Landmark Angle data fed to the software which is the identified by the Surgeon earlier and recorded in the Case sheet.
Once the Toric Overlay scale along with these three axis lines are rotated to coincide this landmark on the Surgical table then the shift observed in this Landmark emissary blood vessel or Episcleral blood vessel or a mole indicates the exact cyclotorsion involved in that Eye and displayed in the Cyclotorsion angle box in "degrees". When viewed on a simple two dimensional display monitor this Toric overlay (with the patient eye in the background) eliminates any possible parallax error. Also a separate arrow mark indicates the exact site of the incision angle calculated after compensating for the cyclotorsion effect.
Step 3:
The Primary incision is made as indicated by the RED arrow mark on the overlayed Circular scale which circumscribes the Limbal arcade to exactly guide the Operating Surgeon on the pre Calculated Incision angle preferred by the Surgeon after compensating for the Cyclotorsion effect. The Surgeon should look for a moment at the Monitor display while placing the distal tip end of the Blade exactly on the indicated Incision location by the RED arrow mark in the Toric Overlay with perfect Centration of the Purkinje image reference.

Reverse Cyclotorsion- Surgical table data:
Immediately after this the Surgeon will make a second side port incision which is unique for each Eye and individual Surgeon's hand comfort zone and this step could be captured as an Image file by clicking on the " Capture " key. The circular scale circumscribing the limbal arcade will indicate the exact angular position of this side port incision location made after Cyclotorsion compensation, With this angle documented in the Case sheet could be used for reverse calculation and verification of the applied Cyclotorsion angle.
Thus, the surgeon apart from positioning the Toric IOL to its designated axis by looking directly at the video of Patient's eye he can use the overlay to accurately locate the incision position, use visual landmarks to accurately correct for cyclotorsion effect and note the amount of cyclotorsion involved in each eye, make the incision considering the cyclotorsion, Non-contact marking system which is based on measured parameters from the A-Scan machine and toric calculator, eliminating marker instrument's edge thickness error, human error and parallax errors. Ink-less marking that does not require scratching the patient’s cornea with a marker pen or a needle can be done without compromising sterility minimizing number of patient - instrument contact by transferring measured parameters directly to the virtual video overlay system. No extra ink is required to be placed for marks. This method uses very thin lines of distinct colors to mark the various axes virtually in a video overlay, thereby eliminating errors due to parallax, marker instrument thickness, and human visual estimation. Direct overlay based on measured parameters eliminates compounding of errors and real-time compensation for accurate alignment of the lens. Automated computation and graphical representation of axis marked in a video overlay eliminates any induced human errors. This method uses the proven Surgeon's skill level on identifying a scleral, epi-scleral or emissary blood vessel or a mole, as a reference mark to accurately measure and record the landmark axis. This eliminates the need for high tech image recognition softwares and complex modifications in the Microscope setup and does not alter any Surgical workflow.
Enables real-time verification of toric parameters using the overlay thereby drastically reducing compounded errors and matching patient expectations. Enables quantitative real-time documentation of the procedure that can be authenticated independently and additional parameter of Cyclotorsion angle could be noted for the operated eye.
Reverse Cyclotorsion verification:
The Patient can be made to sit upright on a Slitlamp later the following day postoperative period after the Surgery and the Slit beam could be aligned in-line with the angular positional location of the Sideport incision to re-confirm and verify the applied Cyclotorsion angle's accuracy level by comparing its numerical angular difference with the On Table noted data of this same sideport location angle we can arrive at the Reverse Cyclotorsion angle calculation to verify the originally applied Cyclotorsion Angle with reference to the identification of the Slitlamp landmark angle.
Enables documentation of possible error in each step, quantification of errors due to every effect and identify any possibility of manufacturing defects in the Toric IOL or Toric Calculation Errors or Surgeon induced Astigmatic factors could be analytically and statistically verified postoperatively with all support documentation.
In the case of a Limbal Relaxing Incision (LRI) procedure performed for correcting residual astigmatism, this system has the option of rotating the angle scale. This video overlay enables direct indication of the angulations on the cornea, helping the surgeon to accurately make the incision (taking into account landmarks for compensating the cyclotorsion effect).
Description of Drawings
Fig. 1 : View of the landmark angle in the slit lamp
Fig. 2 : Noting of landmark angle on the slit lamp scale

Fig. 3 : View of creation of toric overlay
Fig. 4 : View of the cyclotorsion angle

Senthil Kumar B
(Agent for the applicant)
IN/PA-1549

.


Se
,CLAIMS:CLAIMS

We Claim :

1. A system of determination of the exact cyclotorsion angle of an eye, comprising:
a. identification of at least one prominent landmark feature from the Patient’s eye as a landmark angle from the Slit Lamp scale during a pre-operative observation of the Patient’s eye;
b. aligning of a thin slit beam inline with the selected blood vessel after fixating the central reference of the VTA (Virtual Toric Align) software crosswire, coinciding with the Central Purkinje image reflection on the Cornea surface, the location of which is noted from the scale of the slit-lamp in degrees which is taken as the landmark angle;
c. such landmark angle considered to be the reference to compensate for cyclotorsion effect in the lying position of the Patient on the operation table during the Surgical procedure, wherein a circular angle-scale as a video overlay appears on the display of the newly developed VTA which works in the Toric MAX Equipment to guide the Surgeon in real time for indicating the Toric IOL placement location with due compensation of the Cyclotorsion effect for that particular Patient's eye.
2. The invention according to claim 1, wherein, the virtual toric alignment software is designed to overlay the axis using thin, accurate and visible lines of three distinct colours on the surgical video obtained from Operating Microscope CCD camera. This facilitates the Operating Surgeon with the three axis, viz: Toric IOL placement axis, 0-180 axis and landmark axis located as per the slit-lamp reference angle (for compensating cyclotorsion effect) on the circular angle-scale as a video overlay.
3. A system and method for non-contact real-time intraocular Toric IOL alignment and marking, comprising:
a. identification of the landmark noted in the slit-lamp on the operating table by the surgeon by visually looking at a video insert window in the VTA software and moving of a slider provided in the software to exactly locate the white line in the Video Overlay representing the 0 -180 axis in correlation to the Canthus to Canthus reference of the operating Eye or to orient inline with the major horizontal Oval shaped Cornea's Limbal arcade and freezing this as a reference axis, by pressing a button provided;
b. wherein after the pressing of such button, the indication will change to " Reset Toric overlay to its home position " and the slider may be moved to facilitate the operating Surgeon to realign the 0-180 reference if it falls short or overshoots from the required exact Canthus to Canthus alignment or the maximum length horizontal diameter white to white end of the Limbal arcade boundary of the Cornea to which it has to be inline and fixed;
c. positioning of the central crosswire or the RED dot central reference mark in the Toric Overlay to coincide with the naturally formed central Purkinje image reflection from the anterior Cornea which facilitates the Surgeon for Central fixation of the Eye ball without the need for any high tech Eye tracking systems;
d. moving the software slider again to coincide to coincide the Orange coloured overlay line which represents the Landmark axis corresponding to the slit-lamp Angle data fed to the software which is the identified landmark in the upright position of the Patient in the sitting posture observed and its location noted during the Slit-lamp examination, thereby allowing for compensation of the cyclo-torsion effect;
e. moving of the Software slider again from its central home position (After fixating the 0 - 180 ) to coincide with the Orange coloured overlay line which is the Landmark axis corresponding to the slit-lamp observed Landmark Angle data fed in to the software;
f. wherein, once the Toric Overlay scale along with these three axis lines are rotated to coincide this landmark on the Surgical table then the shift observed in this Landmark emissary blood vessel or Episcleral blood vessel or a mole indicates the exact cyclotorsion involved in that Eye and displayed in the Cyclotorsion angle box in "degrees" and when viewed on a simple two dimensional display monitor this Toric overlay (with the patient eye in the background) eliminates any possible parallax error;
g. and wherein a separate arrow mark on the overlayed circular scale which circumscribes the Limbal arcade to exactly guide the Operating Surgeon on the pre-calculated Incision angle preferred by the Surgeon after compensating for the Cyclotorsion effect.
4. The invention as claimed in claim 3, wherein, the software provides for capturing and documenting of the exact angular position of the side port incision location made after cyclotorsion compensation which could be used for reverse calculation and verification of the applied cyclotorsion angle.
5. The invention as claimed in claim 4, wherein the Patient can be made to sit upright on a Slitlamp on the day following the postoperative period after the Surgery and the Slit beam could be aligned in-line with the angular positional location of the Sideport incision to re-confirm and verify the applied Cyclotorsion angle's accuracy level by comparing its numerical angular difference with the noted data of the same sideport location angle, to verify the originally applied Cyclotorsion Angle with reference to the identification of the Slitlamp landmark angle.
6. The invention as claimed in claim 5, further allowing for documentation of possible error in each step, quantification of errors due to every effect and identification of any possibility of manufacturing defects in the Toric IOL or Toric Calculation Errors or Surgeon induced Astigmatic factors analytically and statistically with all support documentation.

Senthil Kumar B
(Agent for the applicant)
IN/PA-1549