WO2022208551A1

WO2022208551A1 - A device and method for positioning the binocular head of a surgical microscope

Info

Publication number: WO2022208551A1
Application number: PCT/IN2022/050324
Authority: WO
Inventors: Prabhat Kumar Baghel; Sandeep Singhai; Shravana Kumar R R; Vinod Karar; Sanjay Sharma; Goraj SINGH
Original assignee: Council Of Scientific And Industrial Research (An Indian Registered Body Incorporated Under The Regn. Of Soc. Act (Act Xxi Of 1860))
Priority date: 2021-03-31
Filing date: 2022-03-31
Publication date: 2022-10-06

Abstract

A microscope system and method for positioning a binocular head of the system, comprising a plurality of light guided projection based graticule modules (4a and 4b), at the working distance with reference to the subject for ophthalmic surgery is described herein. Functionally, the system enables micro manipulation and positioning of the binocular head for setting the binocular head at the working distance during an ophthalmic surgery. The system employs light guided graticule based projection modules (4a and 4b) to micro-manipulate the position of the binocular head at the desired position using the mechanical controls.

Description

1. Title of the invention

A DEVICE AND METHOD FOR POSITIONING THE BINOCULAR HEAD OF A SURGICAL MICROSCOPE

2. FIELD OF THE INVENTION

The present invention relates to a Medical Device. 3. BACK GROUND OF THE INVENTION

Surgical Microscope is a medical instrument to assist the doctors for cataract surgeries and many other eye related diseases. It is used for precision surgical applications like ophthalmic diagnosis, keratoplasty, keratoprothitics and cataract operations. For clear visualization of the operating field so as to enhance the surgeon’s view of the microscopic structures, the design is on the principle of telescopic magnifier and four steps magnification are achieved by using two telescopes of desired power in direct and reverse direction. The fifth step magnification is achieved by direct viewing. The opto mechanical design has been perceived specifically to meet the requirements of eye surgical applications like keratoplasty, keratoprothitics and cataract operations.

The optical components of a basic stereo microscope includes a binocular head, a magnification changer, an objective lens and an illuminator which beams light through the objective lens and onto the operating field. The binocular head includes two telescopes with adjustable eyepieces for users with refractive error. The magnification can be changed by turning a knob (which selects different magnification lenses) or by using a motorized zoom controlled by a foot pedal.

The working distance is the distance from the microscope objective lens to the point of focus of the optical system. This value is fixed and is dependent on the chosen focal length of the objective lens. The choice of working distance depends on the type of surgery. For modern ophthalmic surgery that involves delicate work in the posterior chamber, the commonly used objective focal lengths are 150 mm, 175 mm and 200 mm. The optical system often includes a beam splitter and a second set of teaching binoculars so that two people can view the operation simultaneously.

The optical system is attached to a suspension arm of the floor stand. The suspension arm makes it possible to position the optics exactly and to fix them in place. The floor stand has wheels and can be moved around the floor and fixed into place using the brakes.

A foot pedal connected to the floor stand allows the surgeon to control the focus, the zoom, the position of the optics over the eye (the x,y position on the horizontal plane) and to turn the illumination on and off.

The illumination system is usually housed in the floor stand in order to keep the bulb heat away from the operating field. In this case, the light is transmitted to the operating field by means of a fibre optic cable. The light in ophthalmic micro scopes is usually coaxial, meaning that it follows the same path as the image in order to avoid shadows.

In the current state of the art systems, the adjustment of surgical microscope head to focus on the subject and in particular achieving required working distance in the region of interest on the subject is done manually before the start of operation by either at predefined approximate setting and fine tuned later by focusing or looking through the binocular head. This process leads to wastage of time and also may be irritating for the Surgeon and Patient. It is an additional workload for the Surgeon and may also become critical in certain operational emergencies.

US20030223109A1 describes a reticule illuminated by a light source for superimposing a focusing mark image in main beam path for assisting an observer in adjusting eyepiece. It also mentions about automatic switching on and off of the illumination source once the superimposition is achieved. Though this mentions the use of a superimposition apparatus, the super imposition is at the intermediate plane and not at the object location. W02002069049A2 teaches the concept of superimposing images formed from two reticules on to a focal point (here it is a wafer). However, the applicability of this is in a lithographic system and there is no reference to pre-fixing and pre-aligning of Light Guided Graticule Based Projection Module on either side of objective lens.

Further US4639587A refers to an automatic focusing system for a microscope. This also refers to the usage of reticule being illuminated through optical fiber channels one after the other. Auto adjustment related to superimposing of the images is done by adjusting the objective lens.

However, none of the documents, individually or in combination teach the concept of placing Light Guided Graticule Based Projection Modules on either side of the objective lens, (pre-fixed and pre-aligned in respect of angle with the focal point), in a surgical microscope to set the surgical microscope head at the working distance.

4. OBJECTIVES OF THE INVENTION

It is a singularly important objective of the present invention to provide a system for positioning of a surgical microscope head or a binocular head with the objective focused at the subject precisely. Such a system would be effective in addressing the known limitations of existing art having manual ways to adjust the focus that result in chances of approximation error and is time consuming.

5. SUMMARY OF THE INVENTION

A method and a system for setting of a binocular head or a surgical microscope head at working distance comprising of a plurality of light guided graticule based projection modules for accurate positioning of ophthalmic surgical microscope head in reference to the subject for ophthalmic surgery are presented in the present disclosure. Functionally, the system enables micro manipulation and positioning of the binocular head or the surgical microscope head for setting the surgical microscope head at the working distance during an ophthalmic surgery. The system employs light guided graticule based projection modules to micro-manipulate the position of the surgical microscope head at the desired position using the mechanical controls.

6. BRIEF DESCRIPTION OF THE DRAWING A system and its essential components for setting up of working distance with image projections by two light guided graticule based projection modules, are described in FIG.l. The present invention is illustrated with respect to the system comprising components as shown in FIG.1 and FIG. 2. List of parts

1. MECHANICAL HOUSING OF SURGICAL HEAD

2. OBJECTIVE LENS ASSEMBLY.

3. PROJECTION SYSTEM HOLDING ASSEMBLY.

4a. LIGHT GUIDED GRATICULE BASED PROJECTION MODULE (RIGHT SIDE) 4b . LIGHT GUIDED GRATICULE BASED PROJECTION MODULE (LEFT SIDE)

5. OPERATING PLANE

6. MAGNIFICATION LENS TURRET

7. KNOB FOR MAGNIFICATION SELECTION

8. LIGHT SOURCE OF PROJECTION UNIT 9. CONDENSOR LENS ASSEMBLY.

10. GRATICULE

11. PROJECTION LENS ASSEMBLY.

12. PROJECTION MODULE HOUSING

13. SPACERS OF PROJECTION LENS MODULE 14. SPACERS OF CONDENSOR LENS MODULE

7. DETAILED DESCRIPTION OF THE INVENTION

The system shown in fig.l comprises of a mechanical housing (1) having an ophthalmic surgical microscope head (interchangeably referred to as a binocular head in the description herein), which is supported by a column and have the objective lens assembly (2) at the end. The optical lens assembly (2) includes an objective lens. The distance between the objective lens (2) and the operating plane (5) is the working distance (h). on one side of the objective lens assembly (2) is attached a light guided graticule based projection modules (4a) and on the other side of the objective lens assembly (2) is attached another light guided graticule based projection module (4b), such that both the light guided graticule based projection modules (4a) and (4b) are equidistant from the optical axis of the optical lens assembly (2) and inclined at a particular angle as per the requirement of working distance (h). The light guided graticule based projection modules (4a) and (4b) are attached to a projection system holding assembly (3) and are inclined inwards at pre-calculated tilt angles with respect to the plane perpendicular to the optical axis of the objective lens assembly (2). The projection system holding assembly (3) is attached and/or embedded to the mechanical housing (1).

The position and inclination of the light guided graticule based projection module (4a) and the light guided graticule based projection module (4b) are pre-fixed and pre aligned in respect of angle with the focal point in the operating plane (5) and the distance between the light guided graticule based projection module (4a) and the light guided graticule based projection module (4b) so as to achieve the required height which happens to coincide the projection images from both the modules (4a) and (4b) at the working distance (h) which is also the focus point of the objective lens assembly (2).

The functional block diagram illustrating operational and set-up assembly details of the light guided graticule based projection modules (4a & 4b) are depicted in FIG.2. Each of the light guided graticule based projection modules (4a) and (4b) basically comprises of a light source (8), a condensor lens assembly working as a condensing system (9), a graticule (10) and a projection lens assembly (11) working as a projection system for projecting an image of the graticule in the region of interest. In an example, the light source (8) is placed at the top end of the respective light guided graticule based projection module (4a) and (4b). In an example, the light source (8) is an LED, a bulb, or any other light source. When two or more graticule based images project towards the operating plane with known distance and inclination, they coincide at operating plane (5). If surgical microscope head is moved away from operating plane (5), then the distance between graticule based images starts increasing. This distance between graticule based images will reflect the movement of surgical microscope head position or distance from the operating plane (5). Further, the distance between the projected graticule based images of the light guided graticule based projection module (4a) and the light guided graticule based projection module (4b) depicts the trend of movement of the surgical microscope head with reference to the operating plane (5). If the distance between the projected graticule based images of the light guided graticule based projection module (4a) and the light guided graticule based projection module (4b) decreases, it indicates that the surgical microscope head is approaching the operating plane (5) and vice versa. The light guided graticule based projection modules (4a & 4b) are so positioned and inclined to such a pre-calculated value, that their projected graticule based images coincide at the operating plane (5) only. Further the center of the coincided projected graticule based images is at the center of the field of view of the objective lens assembly and assist in center alignment.

The following steps are to be executed to achieve the intended focus (FIG.3):

Step 1: Switch on the light sources (8) of the light guided graticule based projection modules (4a) and (4b).

Step 2: Make slight adjustment of the surgical microscope head in either direction to gauge the relative position of the individual projected graticule based images from the light guided graticule based projection modules (4a) and (4b).

Step 3: Based on the observation in Step 2, move the surgical microscope head towards the area of interest in the operating plane (5) if the projected graticule based images get closer to each other or in the reverse direction if the projected graticule based images move away from each other.

Step 4: On achieving the superimposition of the projected graticule based images on the area of interest in the operating plane (5), it is deterministically determined visually that the working distance is achieved and the surgeon can go ahead with the operation.

Step 5: Switch off the light sources (8) of the light guided graticule based projection modules (4a) and (4b).

Step 6: Now surgical microscope head is positioned at the center of the field of view and at working distance from subject. 8. EXAMPLES

The light guided graticule based projection modules (4a) and (4b) are attached to the projection system holding assembly (3) and are inclined inwards at pre-calculated tilt angles (qi and Q2) with respect to the plane perpendicular to the optical axis of the objective lens assembly (2). The values of pre-calculated tilt angles (qi and Q2) for various working distance (h) are as below (refer to FIG.4):

Example-1

Calculation of qi & Q2 for

Distance between graticule modules X = 50 mm

Working distance h = 200 mm

Tan (qi) = h / (X/2)

(qi) = Tan ¹(200/25) qi = 82.875 degree qi = Q2 = 82.875 degree

Example-2

Calculation of qi & Q2 for

Distance between graticule modules X = 50 mm

Working distance h = 150 mm

Tan (qi) = h / (X/2)

(qi) = Tan ll 50/25) qi = 80.538 degree qi = Q2 = 80.538 degree

Example-3

Calculation of qi & Q2 for

Distance between graticule modules X = 50 mm

Working distance h = 175 mm

Tan (qi) = h / (X/2) (Oi) = Tan ¹(175/25)

Oi = 81.870 degree Oi = Q2 = 81.870 degree

9. ADVANTAGES

One advantage of the present invention over prior methods of controlling position of the surgical microscope head of an ophthalmic surgical microscope head based system by manual means is that the present invention incorporates pre-located and pre-arranged graticule based projection modules which enables the present invention to function for the adjustment of binocular head to achieve working distance with ease and consistency without actually looking through the binocular head.

Another advantage of the present invention over prior art is that incorporation of the light guided graticule based projection modules as in FIG.l allows the adjustment of binocular head to achieve working distance in real time with reference to the actual position of the target subject. Therefore, present invention is safer and convenient. Another advantage of the present invention over prior art is that incorporation of graticule based projection modules as in FIG.l enable restricting approximation errors based on image based guidance and also enable the user to easily locate the centre of Objective Field of View with projected image guidance.

Claims

We Claim:

1: An ophthalmic surgical microscope system for setting of a binocular head at a working distance with reference to a region of interest in an operating plane (5) of the ophthalmic surgical microscope system, the system comprising: a mechanical housing (1) for the binocular head; an optical lens assembly (2) at one end of the mechanical housing (1); and a light guided graticule based projection module (4a and 4b) on either side of the optical lens assembly, wherein the light guided graticule based projection module (4a and 4b) comprises:

(a) a light source (8);

(b) a condenser lens assembly (9);

(c) a graticule (10); and

(d) a projection lens assembly (11).

2: The ophthalmic surgical microscope system as claimed in claim 1, wherein the light guided graticule based projection modules (4a and 4b) are placed at equidistance on either side of the optical axis of the objective lens assembly (2).

3: The ophthalmic surgical microscope system as claimed in claim 1, wherein the light guided graticule based projection modules (4a and 4b) are attached to a projection system holding assembly (3) and are inclined inwards at pre-calculated tilt angles (qi and Q2) with respect to the plane perpendicular to the optical axis of the objective lens assembly (2).

4: The ophthalmic surgical microscope system as claimed in claim 3, wherein the projection system holding assembly (3) is attached and/or embedded to the mechanical housing (1).

5: The ophthalmic surgical microscope system as claimed in claim 1, wherein the light source (8) is an LED, a bulb, or any other light source.

6: The ophthalmic surgical microscope system as claimed in claim 1, wherein the light source (8) is placed at the top end of the respective light guided graticule based projection module (4a and 4b). 7: The ophthalmic surgical microscope system as claimed in claim 1, wherein each light guided graticule based projection module (4a and 4b) projects an image of the graticule (10), wherein images of the graticules (10) of both the light guided graticule based projection modules (4a and 4b) are focused and coincide at the operating plane (5). 8: A method for setting of a binocular head at a working distance with reference to a region of interest in an operating plane (5) of an ophthalmic surgical microscope system, the method comprising of the following serial steps:

Step 1: switching on light sources (8) of light guided graticule based projection modules (4a and 4b) of the system; Step 2: making an adjustment of the binocular head of the system in either direction to gauge the relative position of individual projected graticule based images from the light guided graticule based projection modules (4a and 4b);

Step 3: based on the observation in Step 2, moving the binocular head towards an area of Interest in the operating plane (5) if the projected graticule based images get closer to each other or in the reverse direction if the projected graticule based images move away from each other;

Step 4: on achieving the superimposition of the projected graticule based images on the area of interest in the operating plane (5), determining visually that the working distance is achieved; Step 5: switching off the light sources (8) of the light guided graticule based projection modules (4a and 4b); and

Step 6: positioning the binocular head at the center of the field of view and at the working distance from subject.