FR2500740A1 - Contact lens for examination of irradiation of eye e.g. by laser - has input surface situated on wave front of radiation beam - Google Patents

Abstract

The lens, used to examine or irradiate the eye consists of an input face (1) for the 'useful' radiation, a totally reflective surface (2) and a spherical output surface (3) which is in contact with the eye. The input surface (1) is on a wave front of the useful radiation, i.e. treatment laser, illuminating beam etc. The optical breakdown effect and the pressure wave of the eye's internal medium are obtained using a beam radiated energy which is very small. The treatment is therefore more reliable, and repeatable. A set of three such lenses, each with specific dimensions, permits an optimal examination or irradiation of the eye's front chamber.

Description

Contact lens for observation or irradiation of the eye.

 The present invention relates to a contact lens for observing or irradiating the eye.

 Contact lenses of various types are used in ophthalmology for the observation or treatment of the eye by irradiation, in particular for the treatment of the anterior chamber of the eye.

The glasses most often used to date are notably Koeppe contact glass and Goldmann glass type contact glass. The use of such glasses has been described in particular in the publication entitled "Gonioskopie und Goniofotographie" by Winfried Buller and Hans-Peter Brandt, Ferdinand Enke
Verlag Stuttgart 1979.

 The Koeppe contact lens is a lens which has an entry face of the curved bundles and a substantially spherical exit face intended to be applied to the transparent zone of the cornea. However, these glasses have so far only been used for eye observation. The dimensioning of these glasses has been mainly studied with a view to obtaining an image of the anterior chamber of the eye with a magnification of 20 to 30 times during observation operations.

 The contact lens of the Goldmann type essentially comprises an entry face of the flat radiation, a substantially spherical exit face intended to be applied to the transparent zone of the cornea and at least one reflecting face or wall allowing the indirect observation of the anterior chamber of the eye by total reflection of the beams on this wall.

 Despite their undeniable intrinsic qualities for observation operations and, in particular, the maneuverability, the ease and the comfort of use for the ophthalmologist with regard to the contact lens of the Goldmann type, these two types of glasses do not allow the treatment of the eye by irradiation with any guarantee of safety for the patient, reliability and reproducibility of the treatment, in particular in the case of high energy irradiations by laser beam. Indeed, in this type of treatment, an objective essential is to obtain a sufficient energy density in the vicinity of the focal point of the radiation in order to cause, by optical breakdown of the dielectric medium inside the eye, a pressure wave capable of ensuring the perforation of neighboring walls of the anterior eye chamber. However, the patient's safety factors during these treatments require a maximum reduction of the energy density radiated at the level of the cornea - contact lens junction in order to avoid any damage of this in the entry zone into The eye of the laser beam. In addition, in order to ensure that each shot of the laser pulse has reproducible conditions and stable emission of the pressure wave (shock wave) into the eye, it is essential that the contact lens allows, by its qualities of form and composition, the best possible focusing of the useful laser beam and the maintenance of its focusing qualities for any point of the eye, mainly of the anterior chamber of the eye.

 Contact lenses of the prior art do not make it possible to obtain all the conditions necessary for a reliable, safe and constant treatment. In particular, it has been observed that the use of contact lenses of the Goldmann type as described above does not allow, under certain conditions of use, that is to say ultimately for certain points in the anterior chamber, to obtain sufficient energy at the focal point to obtain the desired pressure wave by optical breakdown. In fact, the optical breakdown phenomenon for these points is likely to be obtained only at the cost of an increase substantial of the energy density radiated from the beam, this increase by at least a factor of 2 to 3 being prohibitive because of the risk of damage to the cornea and to the contact lens itself.

 The present invention overcomes the aforementioned drawbacks and relates to the use of a contact lens for the observation and treatment of the anterior chamber of the eye.

 Another object of the present invention is a contact lens allowing, by laser irradiation of the eye through this lens, to obtain the phenomenon of optical breakdown and pressure wave of the internal medium of the eye from energy radiated by the beam - the lowest possible.

Another object of the present invention is a contact lens allowing a stable and good optical breakdown phenomenon to be obtained.
spatially localized, this same contact lens making it possible to obtain substantially identical effects, from the clinical point of view, for identical parameters of the laser emission.

 Another object of the present invention is a contact lens for which all of the aforementioned characteristics must remain substantially invariant whatever the position of the shooting point in the eye, or, for a fixed shooting point, whatever the relative positions of the laser beam and the contact lens with respect to the eye.

Such contact lenses can be used in ophthalmological surgery, in particular for the diagnosis and treatment of conditions such as glaucoma or cataracts. For more details on this subject, see European patent applications no. 80 810 357.6 and American patent no. 211 207 and 211 202 in the name of the applicant.

The invention will be described in detail using the description and the drawings below, in which the same references represent the same elements and where:
- the figure represents, in perspective, a contact lens
according to the invention,
- Figure lb shows, in section along a plane of symmetry
longitudinal, the contact lens of figure la applied con
be the cornea of an eyeball for observation and
treatment of the anterior chamber of the eye,
- Figure 2 shows, also in section along a plane of
longitudinal symmetry, the contact lens of figure la
applied against the cornea of an eyeball and the image of the
useful beam on the entry face of the contact lens
- Figure 3 shows, as a comparative result, the
focusing aberration curves of a useful beam in
the case of using a Goldmann type contact lens
and for a contact lens according to the invention.

In accordance with FIG. 1 a, the contact lens for the observation or the irradiation of the anterior chamber of the eye comprises for the useful radiation an entry face 1, a reflecting face 2 by total reflection of this radiation and a substantially spherical outlet surface 3. The contact lens as shown in FIG. 1 is applied directly to the transparent area of the cornea, the substantially spherical outlet surface 3 being applied to the cornea. A binding product of the kind known under the trade name "Methocel" ensures good bonding between the contact lens and the cornea. In order to minimize aberrations at the beam focusing point, the input surface 1 constitutes for the useful radiation a wave surface. Thus at the air-contact lens interface constituted by the input surface 1 the useful radiation undergoes no deviation, the light energy distribution of the useful beam on the wave surface being generally preserved. The term “useful beam” should be understood to mean converging laser treatment beam, the angle of the focusing canes being substantially of the order of 160, or any combination of beams allowing either the visualization of the
path of the laser beam for treatment by the ophthalmic doctor
gue, that is to say the lighting and the observation of any point of the anterior chamber of the eye to be observed. For more details on the creation of useful radiation, reference may be made to the aforementioned patent applications in the name of the applicant.

As shown in FIGS. 1a and 1b, the wave surface constituting the entry face 1 of the useful radiation is a spherical surface whose center of curvature C is the image, in the glass and after reflection on the reflecting surface 2, from the theoretical point F of the eye to be irradiated. As shown in particular in FIG. 1 a, the contact lens is made of a material transparent to useful radiation, substantially delimited by a shape having a plane of longitudinal syria. The shape consists essentially of a cylindrical surface of revolution 100. Any embodiment in which the cylindrical surface of revolution 100 is replaced by a conical surface admitting the same plane of longitudinal symmetry does not depart from the scope of the present invention. input 1 admits for small circle 10 a guideline of the cylindrical surface 100 or the conical surface. In the case where the shape of the glass is constituted by a cylindrical surface 100, the small circle 10 of the spherical entry surface 1 constituting a guideline of the cylindrical surface 100, represents thereon an ellipse. The spherical exit surface 3 of the useful radiation admits as axis of symmetry, contained in the longitudinal plane of symmetry of the contact lens, a parallel ZZ ′ to a generatrix 1000 of the cylindrical surface 100. The exit surface 3 also admits for small circle 30 a circle of radius smaller than that of the director circle 20 of the cylindrical surface 100 and excres relative to the latter. In figure lb the image of the entry face 1 of the useful radiation is delimited by the circle director 20 of the cylindrical surface 100, the small circle 30 of the outlet surface 3 being shown, offset, in phantom. The useful radiation consists for example of a processing beam 11 whose image on the input face 1 is represented, the processing beam being accompanied by two rotating display beams 110 tangent to the envelope of the beam 11 and for materializing, for the practitioner, the envelope of the treatment beam 11
The spherical inlet face 1 and the outlet surface 3 constitute, for the contact lens, respectively a convex surface and a concave surface.

 The use of the contact lens by the doctor being done by pressure of the glass on the elastic cornea, it can be admitted that the anterior surface of the cornea during the laser irradiation is spherical and has the same radius of curvature as the corneal face of the glass formed by the exit surface 3 of the radiation from the contact lens. The radius of curvature p of the concave spherical outlet surface 3 is substantially equal to 0.8 cm. This value, greater than the radius of curvature of the anterior surface of the cornea of an eye at rest, allows obtaining good contact between glass and cornea by eliminating air bubbles and offers the possibility, during from the observation of the corneal irido angle, to open this angle by pressing the glass on the eye. The risk of folds of Decemet forming can be avoided by movement of the contact lens. The reflecting surface 2 by total reflection is a flat surface delimited by the intersection of a plane and the cylindrical surface 100 or the surface conical. As shown in FIG. 1b, this plane constitutes with a plane containing the axis of symmetry ZZ ′ of the outlet surface 3 and orthogonal to the longitudinal plane of symmetry of the contact lens, a dihedral angle has comprised between 180 and 480 substantially. This plane containing the axis of symmetry ZZ 'and orthogonal to the longitudinal plane of symmetry of the contact lens is represented in FIG. 1b by its trace merged with the axis ZZ'. In FIG. 1 a are also shown faces 4, intersection of a plane and the cylindrical or conical surface 100. These faces 4 make it possible by removing material from the cylinder or the cone to lighten the contact lens. Any embodiment in which a lightening of the contact lens is obtained by a different means does not depart from the scope of the present invention . The material used for the production of the glass is preferably a material which does not exhibit shrinkage after thermal stress, for example a glass of the BK7 type.

 As shown in FIG. 1b, the reflecting surface 2 by total reflection comprises a protective plate 21 forming between the reflecting surface 2 and the plate 21 an air space 210 ensuring the condition of total reflection for the useful radiation 11. This plate allows protection against projections onto the reflecting surface 2 of liquids such as "Metho-cel" which would be likely to degrade the conditions of total reflection and energy density of the treatment laser beam. The plate 210 is bonded for example with a thermosetting resin. The center of curvature C of the spherical entry face of the useful radius 11 is located in the longitudinal plane of symmetry of the contact lens at a distance d close to 1 cm. the axis of symmetry ZZ 'of the outlet surface 3 of the contact lens.

 This characteristic allows standardization of the dimensions of the contact lens and makes it easier to produce.

 The contact lens further comprises at the small circle 10 of the entry face 1 of the radiation and at the small circle 30 of the exit surface 3 a shoulder 101, 300 constitutes respectively by the free cylindrical surface 100 and by a surface defined by the intersection of the cylindrical surface 100 and a cone.

These shoulders 101, 300 make it possible to surround the contact lens with a protective plastic case facilitating the manipulation of the glass in deposit V and in rotation 9 around the axis of symmetry ZZ 'by the doctor during the observation and treatment.

 Thus, for a determined value of the dihedral angle a and for a range of values of the relative incidence of the useful radiation 11 on the entry face 1 of the contact lens obtained by rotation of the lens in bearing, the useful radiation retaining a fixed direction, and by rotation o of the contact lens around the axis ZZ 'the focal point F makes it possible to reach in the eye a treatment zone T substantially in the form of a circular crown centered on the axis ZZ'.

As shown in Figure 2, the anterior face of the iris is assimilated as a first approximation to the tangent plane Q to the anterior face of the lens and perpendicular to the axis ZZ 'coincident in Figure 2 with the optical axis of the eye . The geometric parameters of the eye are for the cornea in the presence of the contact lens:
- radius of curvature p of the anterior face
cornea 0.8 cm
- thickness 0.5 mm
- radius of curvature of the posterior face 0.75 cm.

For a laser emission wavelength
X = 1.06 p, laser Nd: YAG, the index of the cornea is n = 1.377,
aqueous mood index n = 1.337, these values being obtained
naked from the Tagawa curves (Tabulae biologicae).

 Taking into account the various ailments to be treated, the laser shots must be carried out in the corneal irido angle, on the iris, on the lens and in the vicinity of the plane Q tangent to the anterior surface of the lens located approximately 3.6 mm from the anterior surface of the cornea. Strictly speaking, for each point located in this plane at a fixed distance from the axis of the eye, there is a value of a, taking into account the choice of the parameter d distance from the center of curvature C from the input face to the axis ZZ ′ and therefore distance from the axis of the useful beam to this same axis, making it possible to focus the beam on this point under optimal focusing conditions.

However, given the dispersions of the values of the abovementioned parameters depending on the individuals, it is sufficient to define a determined number of treatment zones on this plane Q which, taking into account the practitioner's freedom of manipulation, can each be reached without noticeable degradation of the focusing qualities by means of a contact lens of given characteristics. In FIG. 2, three treatment zones T1, T2, T3, two neighboring zones partially overlapping, have been defined. The center line of these zones, circumference of respective radius yl, y2, y3 corresponds to an average zone. The choice of radii yl = 0, y2 = 2.23 mm and y3 = 5.6 mm was made in order to allow , taking into account the average distance d, axis of the useful beam 11 - axis ZZ ', an optimal inclination of the useful beam after reflection on the reflection face 2. This inclination u relative to the axis ZZ', for a cone of focusing of the beam of about 160, in particular makes it possible to obtain maximum mechanical drilling efficiency because the beams in the vicinity of the plane Q are as close as possible, in accordance with the topography of the area to be treated, from the normal to this This mechanical efficiency is moreover combined with a maximum optical path of the beam in the eye, which has the primary consequence of imposing a minimum energy density of the radiation at the level of the anterior face of the cornea, corneal junction. glass, and thereby ensuring abso security read from the patient. In addition, these values, for shots on the lens, allow shots which however avoid the illumination of very sensitive parts of the retina such as the fovea for example. The corresponding tilt values are:
- ul = 490 central zone of the lens. This value provides
an average optical path for the 4 mm beam. This journey
relatively short does not allow for impulse shots
sion whose energy is greater than 30 to 40 mJ due to
risks of instability of optical breakdown position.

- 22 = 630 intermediate zone mainly corresponding to
iris processing, this value provides an optical path
medium from 5 to 6 mm and allows high energy laser shots
50 to 100 mJ.

- U3 = 710 zone of the corneal irido angle, this value provides
an average optical path of 9 to 10 mm and allows shots to be
very high energy 100 to 150 mJ.

 All of the various preceding parameters make it possible to define a particular contact lens, per treatment area, thus preferably allowing the treatment of the corresponding area. Thus for each zone T1, T2, T3 and for the corresponding parameters Y19 ul; Y2, u2; y3, u3 the dihedral angle constituted by the plane delimiting the reflecting surface by total reflection and the plane orthogonal to the longitudinal plane of symmetry of the glass and containing the axis of symmetry ZZ 'of the exit surface 3 of the useful radiation is chosen among the remarkable values al = 230; a2 = 280, a3 = 320, corresponding respectively to the parameters y1, ul; Y2, Y3 # y3> u3 previously defined.

 The entry face of any contact lens thus obtained preferably has a radius of curvature R substantially equal to 4 cm. Thus, as shown in FIG. 2, the image of a useful beam 11 made up, during observation, by rotating display beams 110, of the processing beam 11 subsequently used by the practitioner, by the beams d 'observation 111 and 111' and by an illumination beam 120 is free of overlap between observation beam and illumination beam thus avoiding the glare of the practitioner by reflection of the illumination beam on the input face 1. For more details on the constitution of the useful bundle 11, reference may be made to the patent applications in the name of the applicant already cited.

 The set of three contact lenses thus defined constitutes a set of contact lenses allowing the practitioner optimal observation or irradiation of the anterior chamber of the eye. Each of the glasses of the game has a dihedral angle constituted by the plane delimiting the reflecting surface by total reflection and the plane perpendicular to the longitudinal plane of symmetry of the glass and containing the axis of symmetry ZZ 'of the exit surface 3 of the useful radiation. a different value equal to one of the three remarkable values. This game ensures irradiation or observation of all the points of the anterior chamber of the eye.

In accordance with FIG. 3, the curves represent the aberration ~ in micrometers measured as the increase in diameter of a focusing spot of 60 μm for a beam whose focusing cone is substantially 160 as a function of the angle of incidence of the useful beam 11 on the reflecting face 2, the lens being subjected to a rotation in bearing #, for the three contact lenses constituting the set according to the invention and for a lens of the lens type
Goldmann for which the radius of curvature of the input face is infinite, R = ~. The hatched zone corresponding to the dispersion of the aberration for a plane entry face of the Goldmann glass type as a function of the dihedral angle a of the plane constituting the reflecting surface and of the plane containing the axis ZZ 'orthogonal to the plane of longitudinal symmetry of the contact lens, it is easy to see that the maximum aberration provided by a contact lens according to the invention, very small compared to the diameter of the focusing spot, is approximately three times less, in the case the most unfavorable, that is to say 3 = 320 cases of glass adapted to the treatment of the iridocorneal angle, than in the case of a glass of the Goldmann type.

 We have thus described a system of contact lenses for observation or laser irradiation for which a high safety factor is achieved for the patient. To this quality must be added that of great user comfort for the practitioner.

Indeed, the useful beam being substantially parallel to the optical axis of the eye, the observation of all the parts to be treated of the anterior chamber of the eye is obtained without noticeable modification of the patient position - doctor alone handling of the contact lens. This manipulation can be carried out by rotation e of 3600 about the axis ZZ 'of symmetry of the exit face 3 of the glass and by rotation in bearing t of the contact glass. The only limitation to consider for the amplitude of the rotations in Y-bearing is that of the loss of the condition of total reflection on the reflecting face 2. For each of the three glasses defined above, the maximum amplitude of rotation of the glass in the direction critical, that is to say the direction tending to close the angle of incidence of the useful beam 11 on the reflecting surface 2, is
= = 17, 430 for al = 230
t2 = 12, 430 for a2 = 280
f3 = 8, 430 for a3 = 320 for a BK7 glass of index 1.507 at X = 1.06p
These limit values of rotation in bearing with respect to an initial starting position correspond substantially to the coincidence of the optical axis of the eye and the axis of symmetry ZZ ′ of the exit surface 3. They are largely sufficient to allow the doctor to compensate, by simple manipulation of the contact lens, for the erratic movements of the eyeball of the existing patient despite prior anesthesia of the eyeball muscles, or to achieve, without appreciable degradation of the beam focusing conditions, therefore with an assurance of reliability and reproducibility of operations, each point of the corresponding processing areas respectively.

Claims (12)

 1. Contact lens for observation or irradiation of the eye comprising, for useful radiation, an entry face, a reflecting surface by total reflection and a substantially spherical exit surface, characterized in that said surface input constitutes, for the useful radiation, a wave surface.  2. Contact lens according to claim 1, characterized in that the wave surface constituting the entry face of the useful radiation is a spherical surface whose center of curvature is the image in the glass and after reflection on the surface reflecting from the theoretical point of the eye to be observed or irradiated.  3. Contact lens according to claim 1 or 2, characterized in that it is made of a transparent material substantially delimited by a shape having a longitudinal plane of symmetry and constituted by a cylindrical surface of revolution, said inlet face, spherical, admitting for a small circle a guideline of the cylindrical surface and the spherical exit surface admitting for axis # of symmetry, contained in the longitudinal plane of symmetry of the glass, a parallel to a generatrix of the cylindrical surface, said surface of outlet admitting furthermore for a small circle a circle of radius smaller than that of the director circle of the cylindrical surface and eccentric with respect to the latter, said inlet face and the spherical outlet surface constituting, for the contact lens, respectively a convex surface and a concave surface, said surface reflecting by total reflection being a plane surface delimited by the intersection of a plane and d e the cylindrical surface, said plane constituting with a plane containing the axis of symmetry of the outlet surface and orthogonal to the longitudinal plane of symmetry of the contact lens a dihedral angle has comprised substantially between 180 and 480.  4. Contact lens according to one of claims 1 to 3, charac terized in that the transparent material is a glass of the BK7 type.  5. Contact lens according to one of claims 3 or 4, characterized in that said reflective surface by total reflection comprises a protective plate providing between the reflective surface and the plate an air gap ensuring the condition of total reflection for useful radiation.  6. Contact lens according to one of claims 3 to 5, characterized in that the concave spherical outlet surface has a radius of curvature substantially equal to 0.8 cm.  7. Contact lens according to one of claims 3 to 6, characterized in that the center of curvature of the spherical entry face of the useful radiation is located, in the longitudinal plane of symmetry of the contact lens, at a distance d close to 1 cm from the axis of symmetry of the contact lens outlet surface.  8. Contact lens according to one of claims 2 to 7, ca acted in that the radius of curvature of the spherical input surface is substantially equal to 4 cm.  9. Contact lens according to one of claims 3 to 8, ca characterized in that the contact lens comprises at the level of the small circle of the entry face of the radiation and at the level of the small circle of the exit surface a shoulder constituted respectively by the free cylindrical surface and by a conical surface delimited by the intersection of the cylindrical surface, the conical surface and the plane constituting the reflecting face.  10. Contact lens according to one of claims 3 to 9, ca characterized in that the dihedral angle a constitutes by the plane delimiting the reflecting surface by total reflection and the plane orthogonal to the plane of longitudinal symmetry of the glass and containing l The axis of symmetry of the exit surface of the useful radiation is chosen from the three remarkable values 320, 280, 230.  11. Set of contact lenses for observation or irradiation of the eye according to one of claims 3 to 10, characterized in that it comprises three contact lenses, each of the contact lenses having the dihedral angle has constituted by the plane delimiting the reflecting surface by total reflection and the plane perpendicular to the longitudinal plane of symmetry of the glass and containing the axis of symmetry of the exit surface of the useful radiation a different value equal to one of the three remarkable values 320, 280, 230, said set allowing the irradiation of all the points of the anterior chamber of the eye.  12. Use of a contact lens or a set of contact lenses according to the preceding claims for the observation or irradiation of the eye by laser beam.