GB1573748A

GB1573748A - Laser ophthalmological units

Info

Publication number: GB1573748A
Application number: GB37274/77A
Authority: GB
Original assignee: FIZ INST IM P N LEBEDEVA AKAD; VNII GLAZNYKH BOLEZNEI
Current assignee: FIZ INST IM P N LEBEDEVA AKAD; VNII GLAZNYKH BOLEZNEI
Priority date: 1977-09-07
Filing date: 1977-09-07
Publication date: 1980-08-28

Description

(54) IMPROVEMENTS IN OR RELATING TO LASER OPHTHALMOLOGICAL UNITS (71) We, FIZICHESKY INSTITUT IMENI P.N. LEBEDEVA AKADEMII NAUK SSSR, a Corporation organised and existing under the laws of the Union of Soviet Socialist Republics, of Leninsky prospekt, 53, Moscow, U.S.S.R., and VSESOJUZNY NAUCHNO ISSLEDOVATELSKY INSTITUT GLAZNYKH BOLEZNEI, a Corporation organised and existing under the laws of the Union of Soviet Socialist Republics, of ulitsa Pogodinskaya, 5, Moscow, U.S.S.R., do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to laser ophthalmological units.

According to the present invention there is provided a laser ophthalmological unit comprising a laser, a system for directing the laser beam emitted by the laser, a slit light source provided with a light transmitting element arranged to produce an optical mark, a system for directing light from the slit light source, and a microscope, the laser and the slit light source being rigidly interconnected and accommodated in a housing and the housing and the microscope being mounted for independent rotation about a common axis, the system for directing the laser beam, the system for directing light from the slit source and the microscope being so arranged that the laser beam, the light from the slit source and the microscope can be focused in a common focal plane which contains said common axis.

The unit is arranged so that the optical mark produced by the light transmitting element within the slit source indicates the point at which the laser beam is focused.

This provides a simple method for aiming the laser beam at any particular point within the surgery field. Although the elements of the systems directing the laser beam and the light from the slit source can be installed in various parts of the ophthalmological unit, it is preferable that the elements are secured to the above-mentioned housing. This embodiment is technically simple and the dimensions of the laser together with the slit source and the laser beam directing system are the minimum possible.

A laser ophthalmological unit embodying the invention will now be particularly described by way of example with reference to the accompanying diagrammatic drawing the sole figure of which is a side view, partially in section, of the unit. The illustrated laser ophthalmological unit comprises a microscope mounted upon a bracket 2 and focused on a surgery field 3 in the patient's eye. A laser 4 is provided and an optical system 5 is arranged to direct and focus the laser beam on the surgery field 3.

The emission from a slit light source 6 is deflected by a deflecting element 7, also onto the surgery field 3. Any known microscope of sufficient magnification can be used in the unit.

The laser 4 is any usual Q-switched laser, e.g. a ruby laser.

The slit source 6 comprises a casing 7' accommodating a light source 9 (for example, an iodine incandescent lamp), a lens 10 arranged to produce a parallel beam from the source 9, two slit apertures 11 and a lens 12 formed by a double-convex and a plano-concave lens, all having a common optical axis 8.

Located between the slit apertures 11, again on the optical axis 8, is a light transmitting element in the form of a neutral light filter 13 whose edge portion has a transmission coefficient of the order of 10% and whose central portion is clear, having a transmission coefficient close to 100% and a diameter of about 0.2 mm. This filter 13 acts as an optical marker creating a mark in the form of an area of higher illumination with a diameter of the order of 0.2 mm in the central part of the surgery field 3. This mark enables the operator to select a particular spot to which the laser beam is to be applied.

Other forms of optical marker are also possible, for example it can be a plate with a transmission coefficient close to 100% with a central marker portion tinted in some colour.

The laser 4 and the slit source 6 are placed in a housing 14 and rigidly connected together by means of fastenings 15 on a post 16 which is in its turn rigidly secured to the housing 14 by means not shown. The upper part of the housing 14 is provided with windows 17 to allow the beams of the laser 4 and the slit source 6 to pass through. The housing 14 is hinged on the bracket 2 of the microscope 1 (the hinged connection is indicated by the dotted line 18) so that the housing 16 has all the degrees of freedom required to manipulate the laser beam and the light beam from the slit-source 6 with respect to the microscope 1 and the surgery field 3. The hinged connection should be arranged so that the axis lies in the focal plane common to the optical system 5, the microscope 1 and the slit source 6.

A holder 19 is rigidly secured on the wall of the housing 14 and carries the lightdeflecting element 7 (in this embodiment- an aluminium mirror) by way of an adjustment mechanism which allows the element 7 to be rotated in the direction indicated by arrow 20 and moved perpendicular to the axis 8 of the slit source beam as indicated by arrow 21. The slit source 6 is arranged in the housing 14 so that its optical axis 8 is directed to the central part of the deflecting element 7 such that the beam is reflected along a path in the same plane as the optical axis 22 of the microscope 1. The holder 19 also carries elements 23 and 24 of the optical system for directing and focusing the laser beam on the surgery field 3. In this case the deflecting element 23 is provided with an adjustment mechanism so that it can be rotated in the direction indicated by arrow 25 and also moved along the path of the laser beam after it has been deflected as indicated by the arrow 26. In order to increase the resistance of the element 23 to intense laser emission and to minimize losses of the laser beam, the deflecting element 23 is formed as a prism having respective angles of the reflecting surface selected so that the incident and reflected beams are perpendicular to the respective prism faces.

It should be noted that the laser 4 and the slit illumination system are arranged within the housing 14 so that their optical axes lie in one plane and the angle between them is between 0 and 150. The restriction of the angle between the optical axes of said elements is due to the dimensions of the housing 14.

Before the described unit is used, it must be adjusted. This is done by first moving the prism 23 along the axis of the lens 24 in the direction indicated by the arrow 26 and turning it perpendicular to said axis until the path of the laser beam after it has passed through the prism 23 is coincident with the axis of the lens 24. Then the lens 24 is moved along its optical axis so that the laser beam is brought into focus on the image plane of the slit apertures 11. The mirror 7 is then shifted in the direction indicated by the arrows 20 and 21 until the image of the marker in the filter 13 is coincident with the point at which the laser beam is focused.

The laser is then switched off.

After the ophthalmologist had made the usual microscopic inspection of the patient's eye, he selects the spot to which the laser is to be applied using light from the slit source 6. This is done by moving the unit in the directions indicated by the arms 27 and 28 by means of known devices, and rotating it about the axis 18. The optical mark produced by the filter 13 is then centred on the selected spot, again moving the unit in the directions indicated by arrows 27, 28 and 18. The spot is thus automatically brought in the focal plane of the microscope lens, so that the image of both the surgery field 3 and the mark are sharply focused. The laser can now be started by means of a button or a foot pedal.

The spot is subjected to the laser beam whose parameters have been preselected and can be controlled by the ophthalmologist by means of a control unit included in the power supply unit.

The described unit has the advantage that existing slit illumination sources can be employed with only slight modifications.

These modifications consist in the introduction of an optical marker and installation of a laser 4 which poses no problems since there is more than enough space within the housing 14. The attachment of the elements of the optical system 5 also presents no difficulties.

The described unit is also advantageous in that it has a wide range of clinical applications. It is applicable in clinical cases where the laser beam is to be applied simultaneously with the observation of the area undergoing treatment, or when the laser beam is to be applied at a large angle to the observation axis or when peripheral parts of the eye globe are to be treated.

The rigid attachment of all components of the laser and the slit source in a housing hinged on the microscope bracket is advantageous in that it gives the ophthalmologist complete freedom to manipulate the laser beam with respect to the microscope. Also, it means that the system for directing the laser beam on to the surgery field need only comprise a minimum number of optical elements, i.e. a deflecting element and a focusing element. This reduces losses of laser emission along the optical path due to the small number of reflecting surfaces and also reduces aberrations of the focusing element.

Therefore the clinical efficiency of the unit is high as the power density of the laser beam at the selected spot is high and the diameter of the focused laser beam is small. The described unit can be employed in the treatment of glaucoma cataracts and some other diseases of the eye, where previously known units are hard to use due to the focused beam being insufficiently powerful and having a rather large diameter.

The inclusion in the slit source of a lighttransmitting element which is able to produce an optical mark eliminates the need for an additional source and so it is possible to use one white light source both for illuminating the spot to be treated and for aiming the laser beam.

WHAT WE CLAIM IS: 1. A laser ophthalmological unit comprising a laser, a system for directing the laser beam emitted by the laser, a slit light source provided with a light transmitting element arranged to produce an optical mark, a system for directing light from the slit light source, and a microscope, the laser and the slit light source being rigidly interconnected and accommodated in a housing and the housing and the microscope being mounted for independent rotation about a common axis, the system for directing the laser beam, the system for directing light from the slit source and the microscope being so arranged that the laser beam, the light from the slit source and the microscope can be focused in a common focal plane which contains said common axis.

2. A laser ophthalmological unit according to Claim 1, wherein the housing is hinged to a bracket carrying the microscope.

3. A laser ophthalmological unit as claimed in Claim 1 or Claim 2 wherein the system for directing the laser beam comprises a reflecting element secured to the housing in such a manner that it can be moved in two mutually perpendicular planes and along the path taken by the laser beam after reflection.

4. A laser ophthalmological unit according to any one of Claims 1 to 3, wherein the axis of the laser and the optical axis of the slit source lie in one plane and form an angle of from 0 to 150.

5. A laser ophthalmological unit substantially as described hereinabove with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the microscope. Also, it means that the system for directing the laser beam on to the surgery field need only comprise a minimum number of optical elements, i.e. a deflecting element and a focusing element. This reduces losses of laser emission along the optical path due to the small number of reflecting surfaces and also reduces aberrations of the focusing element. Therefore the clinical efficiency of the unit is high as the power density of the laser beam at the selected spot is high and the diameter of the focused laser beam is small. The described unit can be employed in the treatment of glaucoma cataracts and some other diseases of the eye, where previously known units are hard to use due to the focused beam being insufficiently powerful and having a rather large diameter. The inclusion in the slit source of a lighttransmitting element which is able to produce an optical mark eliminates the need for an additional source and so it is possible to use one white light source both for illuminating the spot to be treated and for aiming the laser beam. WHAT WE CLAIM IS:

1. A laser ophthalmological unit comprising a laser, a system for directing the laser beam emitted by the laser, a slit light source provided with a light transmitting element arranged to produce an optical mark, a system for directing light from the slit light source, and a microscope, the laser and the slit light source being rigidly interconnected and accommodated in a housing and the housing and the microscope being mounted for independent rotation about a common axis, the system for directing the laser beam, the system for directing light from the slit source and the microscope being so arranged that the laser beam, the light from the slit source and the microscope can be focused in a common focal plane which contains said common axis.