Contact lens for use in the treatment of macular degeneration associated disease

Abstract

The invention concerns a contact lens (1 ) comprising: - a lens body (10) having an optical centre (O) and an optical axis (OA) passing through the optical centre, - a prismatic element (20) intersecting with the optical axis of the lens body so as to enable a deflection of the light along with a deflection axis (A), - a counterweight (30) arranged to keep a gravity centre (GL) of the lens at a stable equilibrium point when the contact lens (1 ) is turned around the optical axis to make sure that the deflection axis reaches the target zone (C) of the retina of the patient.

Description

Field of the invention The present invention relates to contact lenses, especially contact lenses aiming to deflect the visible light at the entrance of a patient eyes. The contact lens of the present invention is particularly suitable for macular degeneration disease such as age-related macular degeneration (AMD). Description of the Related Art Macular degeneration is an eye condition affecting close to 200 million older people worldwide. This retinal disease is caused by either an accumulation of cell debris or leaking extracellular plasma, causing the death of the photoreceptors in the macular area, and particularly in the fovea centralis, small, central pit located in the centre of the macula of the retina. The symptoms associated with this eye condition vary in function of the stage of AMD. The patient generally undergoes a worsening of vision which is associated to a blurred vision, reduced visual acuity, reduced macular sensitivity and the apparition of a central scotoma, leading to a central vision loss. In some cases, this macular degeneration can generate central lesions in one or two of the eyes. There are two types of AMD: dry (atrophic) or wet (exsudative) AMD. For the dry AMD, there is not any treatment. A vitamin supplement, known as the AREDS formula, is likely to slow the progression of the disease for some patients. For the wet AMD, a treatment exists for stabilising the macular degeneration by intravitreal injection of an anti-vascular endothelial growth factor. However, this treatment does not restore the patient’s vision. At this time, the deterioration of the macula caused by AMD cannot be repaired by surgery or medication. A comprehensive understanding of the protective mechanisms naturally developed by the patients affected by AMD could help in reducing the impact of this disease on their social life. In people non affected by AMD or a macular disease, when the light incident to the eye propagates along with a central optical axis of the eye without being deviated and reaching the fovea centralis of the macula. A maximum visual acuity and a sharp vision may be obtained at this point of the macula, except when the person is affected by another eye condition such as hypermetropia and myopia. Clinical trials evidenced that the patients affected by AMD generally develop preferred retinal locus (PRL) in one or the two eyes spontaneously or within a few months after the first symptoms have occurred. The patient’s viewing is no longer central, but rather eccentric and the patient develops preferred retinal locus in a peripheral region of the retina not affected or slightly affected by macular degeneration. For this reason, PRL is also called pseudo fovea as patients often experience in this new point an improved visual acuity (VA) compared to the degenerated macular region. Various methods have been implemented to identify the PRL in patients affected by AMD, among which the most commonly employed is microperimetry, and optical coherence tomography (OCT) combined with scanning laser ophthalmoscope (SLO). To perform a complete diagnostic of the patient, the practitioner may determine the precise localisation of the PRL, the distance between the PRL and the fovea centralis, the distance between the PRL and a border of a retinal scar and the stability of the PRL. A low vision rehabilitation is generally considered to realign the patient’s vision toward the PRL. Contact lenses have been widely used to improve, and even correct patient’s vision for various eye conditions such as hypermetropia, myopia, astigmatism, presbyopia, etc. It is worth noting that only one or few contact lens types may be used for correcting the patient’s vision for each eye condition. For instance, presbyopia is treated by using either multifocal contact lenses or monovision-type contact lenses. Until recently, there were no contact lenses specifically adapted for patients affected by AMD. However, recently, contact lenses comprising a prismatic element have been described to deviate the light entering in patient’s eyes, out of the scotoma related to AMD, and facilitate the eye rehabilitation, and particularly low vision rehabilitation, for patients experiencing AMD. For example, documents US6139145 and US6197057 disclose contact lenses for use in the treatment of AMD, the contact lenses comprising at least one prismatic element for deflecting the light toward a specific portion of the eye. The prismatic element is generally arranged substantially centrally in the contact lens and has a weight evenly distributed in the contact lens. Document WO 2017 / 051185 discloses a contact lens which includes one or more prismatically active surfaces, such that when in place on the eye of a patient, the prismatically active surfaces act to deflect light incident thereon away from a central region of the macula of said eye. The one or more prismatically active surfaces of the contact lens are discrete and distinguishable from the continuously arcuate exterior or interior surface of said contact lens in which they are provided. By deflecting or diverting the light on optically receptive regions of the macula, such a contact lens could provide correction for patients affected by AMD. The contact lens comprises two continuous arcuate shape exterior surfaces, both or one having one or more discontinuities. These discontinuities result in a sudden increase or decrease of the thickness of the contact lens at specific regions of the exterior surfaces. Such modifications of the contact lens thickness generate prismatically active surfaces, thereby surfaces that deflects the light entering to the eye of the patient. According to a first configuration, the weight of the prismatically active surfaces is evenly distributed in the contact lens volume. Thus, once the alignment operation for deflecting the incident light toward the PRL has been done by the practitioner, the contact lens has no reason to move. However, in other cases, it may not only be complicated for the practitioner to find the ideal alignment but also to maintain this ideal alignment after the alignment operation has been done. Indeed, the contact lens will tend to move in order to have its gravity centre aligned with the unequal distribution of the weight caused by the prismatically active surfaces. In such a situation the patient must return to his or her practitioner to perform the alignment operation again. The present invention offers a solution for contact lens comprising at least one prismatic element having unequal distribution of their weight within the volume of the contact lens. Summary of the invention The present invention proposes a contact lens comprising: - a lens body made of a material with a first refractive index, having an optical centre and an optical axis passing through the optical centre, said optical axis being intended to be aligned with the fovea centralis of a patient’s retina where the contact lens is installed on a patient’s eye, - at least one prismatic element made of a material having a second refractive index different from said first refractive index and intersecting with the optical axis of the lens body so as to enable a deflection of the light along with a deflection axis, said deflection axis forming a nonzero acute deflection angle with the optical axis of the lens body and being intended to cross a target zone of the retina of the patient that differs from the fovea centralis, - at least one counterweight element arranged to keep a gravity centre of the contact lens at a stable equilibrium point when the contact lens is turned around the optical axis to make sure that the deflection axis reaches the target zone of the retina of the patient. In the contact lens according to the present invention, the counterweight element acts as a permanent rebalancer for the prismatic element, thereby it prevents any rotation of the contact lens. The prismatic element is always well-balanced whatever the angle of rotation of the contact lens around the optical axis, which guarantees that the centre of gravity of the contact lens is always at a stable equilibrium point when the contact is turned around the optical axis. According to different additional characteristics that can be taken together or separately: - said at least one counterweight element is arranged around said at least one prismatic element; - said at least one prismatic element is a triangular prism; - said triangular prism has a first active face perpendicular to the optical axis and a second active face forming a prism angle p with the first active face, said optical axis intersecting the first and second active faces, respectively, at a first and a second crossing points; - the prism angle 3 is comprised between 1 ° and 20° and the second refractive index is comprised between 1.4 and 1.9; - the deflection angle is comprised between 1° and 20°; - the lens body and said at least one prismatic element are made of different materials; - the lens comprises two triangular prisms as prismatic elements, said triangular prisms being arranged head to tail; - said triangular prisms are identical so as to form, together, parallel plates; - the lens body further comprises parallel plates; - the parallel plates are separated by a distance comprised between 0.5 mm and 2 mm; - the contact lens is soft, semi-rigid or rigid or a combination thereof. The present invention also proposes another contact lens comprising: - a lens body having an optical centre and an optical axis passing through the optical centre, said optical axis being intended to be aligned with the fovea centralis of a patient’s retina where the contact lens is installed on a patient’s eye, said lens body having a first active face with a first centre of curvature and a second active face with a second centre of curvature different from the first centre of curvature to provide for a prismatic effect to said lens body so as to enable a deflection of the light along with a deflection axis, said deflection axis forming a non-zero acute deflection angle with the optical axis of the lens body and being intended to cross a target zone of the retina of the patient that differs from the fovea centralis, - at least one counterweight element arranged to keep a gravity centre of the lens at a stable equilibrium point when the contact lens is turned around the optical axis to make sure that the deflection axis reaches the target C of the retina of the patient. In any case, a contact lens according to the invention may be used in the treatment of age-related macular degeneration or other macular degeneration. Brief description of the drawings Other features, aims and advantages of the invention will become apparent from the following description, which is purely illustrative and non-limiting, and must be read with reference to the appended drawing wherein: - Figure 1a is a cross sectional schematic view of a contact lens according to a first illustrative embodiment of the invention and the optical path taken by the incident light; - Figure 1b is a cross sectional schematic view of a contact lens according to a second illustrative embodiment of the invention and the optical path taken by the incident light; - Figure 2a illustrates the distribution of the preferred retinal locus in the visual field in patients with age-related macular degeneration according to a first prior art reference; - Figure 2b illustrates an example of preferred retinal locus (PRL) location coordinates in relation to scotoma for patients with age-related macular degeneration according to a second prior art reference; - Figure 3 illustrates the evolution of the deflection angle as a function of the light angle of incidence for different contact lens parameters of a contact lens according to the illustrative embodiment of figure 1a; - Figure 4 is a front schematic view of the contact lens according to an illustrative embodiment of the invention, such as that one of figure 1 a or figure 1 b; - Figure 5 illustrates an advantageous embodiment of the invention; - Figure 6 is a cross sectional schematic view of a contact lens according to another alternative embodiment of the invention. Detailed description of the invention In reference to the figures, the invention concerns a contact lens 1 intended to be in intimate contact with an eye of a patient. The contact lens 1 according to the invention aims at improving the vision of a patient affected by age-related macular degeneration. Nevertheless, the contact lens 1 may find application in other diseases affecting the macula of the retina as patients suffering from one or several of these diseases, generally develop preferred retinal locus (PRL). Reference is made to the preamble of the present description which describes how macular degeneration affects the patient’s vision and how the retina adapts to the central vision loss that occurs under such a situation. With reference to figure 1a, the contact lens 1 according to a first illustrative embodiment of the invention comprises a lens body 10 and a prismatic element 20 arranged in the lens body 10. The lens body 10 aims at deflecting the light entering the eye. It comprises an optical centre O, and an optical axis OA passing through the optical centre O. The lens body 10 also comprises a plane lens PL perpendicular to the optical axis OA. The optical axis OA is intended to cross the fovea centralis F of a retina of the eye when the contact lens is placed on the cornea of the patient. The lens body 10 is configured to be turned around the optical axis OA in order to find the PRL specific to the patient. In the invention as in most contact lenses of the prior art, the optical axis OA coincides with an axis of symmetry of the contact lens 1. When the contact lens 1 of the invention is placed on the cornea of the patient, the light crosses the contact lens 1 and enters into the eye of the patient in a direction of propagation A deviated from the optical axis OA by said at least one prismatic element. In the description, the “incident light” refers to the portion of the light reaching the contact lens 1 and the eye of the patient before being directed by the contact lens 1 and / or before entering the eye. As mentioned above, the optical axis OA crosses the plane PL perpendicularly by passing through the optical centre O of the contact lens 1. The plane PL is defined by a transversal axis X and a vertical axis Y, preferably intersecting at their origin, their origin being the optical centre O. In practice, the plane lens PL is a part of a three-dimensional Euclidean space wherein a first direction is defined along the transversal axis X, a second direction is defined along the vertical axis Y and a third direction is defined along the optical axis OA. Thus, the optical centre O has an (x,y) coordinate with a value (0;0) in the plane lens PL. The lens body 10 is made of a material with a first refractive index n. The material is selected among the soft, semi-rigid and rigid contact lens from material known of the skilled person. For example, hydrogels or hydrogels / PMMA are well-known. The refractive index is typically comprised between 1.4 and 1.9. In the illustrative embodiment of figure 1a, the lens body 10 has two faces, more precisely a first face 11 and a second face 12 which correspond to its exterior surfaces. The first and second faces 11,12 are the active optical faces of the contact lens 1, that is the faces intended to interact with the incident light. The faces 11, 12 of the lens body extend in the plane lens PL. The contact lens 1 may be a converging concave-convex contact lens, namely a positive meniscus contact lens. The two faces 11, 12 of the lens body 10 are spherical faces 11, 12. A first spherical face 11 is a convex surface whilst a second spherical face 12 is a concave surface, both having for example a same pre-determined radius of curvature with a same curvature centre. The invention is not limited by these configurations and various adjustments may be performed to fit the eye condition of the patient. The radii of curvature of the spherical faces 11, 12, as well as other parameters of the contact lens 1 may be adapted to correct other eye conditions affecting the patient’s vision. The prismatic element 20 is arranged in the lens body 10 and more specifically located between the two faces 11, 12 of the lens body 10. The prismatic element 20 is made of a material having a second refractive index r2 which is different from the refractive index h of the lens body 10 and intersects with the optical axis OA of the lens body 10 so as to enable deflection of the light along with a deflection axis A. In practice, the lens body 10 and the prismatic element 20 may be made of different materials. The materials chosen may have a refractive index comprised between 1.4 and 1.9. The deflection axis A forms a non-zero angle a with the optical axis OA. In such a condition, when the contact lens 1 is placed on the cornea of the eye, the light entering the eye of the patient is deflected toward a zone of the retina of the patient that differs from the fovea centralis F, called “target zone C” in the present invention. The deflection effect of the prismatic element 20 is for example used to help the patient during the rehabilitation of his or her eye by retargeting the light toward the PRL, thereby toward privileged areas of the retina. The prismatic element 20 may advantageously comprise a plurality of active faces 21, 22 intersecting with the optical axis OA so as to enable a deflection of the light along with the deflection axis A. The prismatic element 20 may comprise other faces than the active faces 21, 22, but only the active faces 21,22 interact with the light in order to produce the prismatic effect. The contact lens 1 illustrated in figure 1a comprises another face 24 which is a nonactive face 24. According to the illustrative embodiment, when the light enters the contact lens 1, it successively passes through the first face 11 of the lens body 10, optionally the material of the lens body 10, a first active face 21 of the prismatic element 20, the material of the prismatic element 20, a second active face 22 of the prismatic element 20, optionally the material of the lens body 10 and the second face 12 of the lens body 10. After having been deflected in the contact lens 1 the light enters the eye with a deflection, according to a deflection angle a with the prismatic element 20 of figure 1a. In a possible embodiment, the prismatic element 20 is a triangular prism (Figure 1a). In this embodiment, the first active surface 21 is perpendicular to the optical axis OA whilst the second active surface 22 forms a prism angle 3 with the first active surface 21. The second active surface 22 is therefore not perpendicular to the optical axis OA. First and second active surfaces 21, 22 both intersect with the optical axis OA at, respectively, a first and a second crossing points. When the light falls on the second active surface 22, it is deflected from the optical axis OA of the non-zero sharp angle a along the deflection axis A in such manner that it goes toward a different region from the fovea, namely the target zone C, when the patient wears said contact lens 1. As an example, the prism angle 3 (figure 1a) is between 1° and 20° and the second refractive index is between 1.4 and 1.9. Considering light arriving perpendicularly to a prism face, these parameters allow deviation of the light toward the target zone C which corresponds to common locations of the PRL. For example for patients suffering from AMD, having a prism angle 3 in the range 1° - 15° and a refractive index in the range 1.4 - 1.9 allows obtaining a deflection angle a in the range 1° - 15° (Figure3). In this regard, referring now to figure 2a, we have an example of a possible distribution of the PRL in the retinal (left panel) and visual field (right panel) in patients with AMD (Jonathan Denniss er al., 2017, Properties of visual field defects around the monocular preferred retinal locus in age-related macular degeneration). The white cross represents the presumed location of the anatomic fovea. The grey circle (left image) indicates the optic disc location. In this regard also, referring now to figure 2(b), we have an example of PRL coordinates in relation with the retina of an AMD affected patients (Luminita Tarita-Nistor et aL, 2023, What is a preferred retinal locus ?) In the left image, we can see an eye with its optic disc centre and the fovea, as well as the PRL (Preferred Retinal Locus) to reach with the lens of the invention. The right image better shows a schematic example of the PRL position with regard to the fovea which is at the centre of the image. In figure 3, we have represented the deviation angle as a function of the incidence angle for several types of triangular prisms, for which 3 represents the prism angle and n the refractive index of the prism (For example 3 = 10° and n = 1,74 for the highest curve). By comparing the different curves, one can understand that the features of the triangular prisms allow obtaining different deviation angles. It should be noted that for each curve the flat part allows limiting the deformation of the image in the macular region. In addition, the rotation of the triangular prism around the optical axis allows choosing the direction of the deviation. As can be seen in figure 1a the contact lens 1 also comprises a counterweight element 30 to keep a gravity centre of the contact lens 1 at a stable equilibrium point when the contact lens 1 is turned around the optical axis OA to make sure that the deflection axis A reaches the target zone C of the retina of the patient. The counterweight element 30 therefore acts as a permanent rebalancer for the prismatic element 20 and keeps the gravity centre of the contact lens 1 at a stable equilibrium point when the contact lens 1 is turned around the optical axis OA. Furthermore, as the prismatic element is always well-balanced whatever the angle of rotation of the contact lens 1, the contact lens 1 in the eye of the patient is prevented from displacing during the alignment of the contact lens 1 in the eye and after the alignment operation has been performed by the practitioner. It should be noted that the prismatic element 20 may also have another shape than the triangular one as illustrated in Figure 1a. In particular, the prismatic element 20 may have a trapezoidal shape. In particular here, the trapezius comprises active faces 21, 22 parallel with each other but that are not perpendicular to the incident light. Such an embodiment brings about a deviation of the light at the output of the contact lens with an optical path A parallel to the optical axis. It should be noted that the trapezoidal shape corresponds geometrically to the association of two triangular prisms arranged head to tail. Accordingly, the embodiment of figure 1b may be seen as an embodiment wherein two identical triangular prisms arranged head to tail are present in the contact lens to form parallel plates. In a more general way, the triangular prisms are not identical but arranged head to tail to obtain more complex deviations. According to the invention, the contact lens 1 of figure 1b also comprises a counterweight element 30 to keep a gravity centre of the contact lens 1 at a stable equilibrium point when the contact lens 1 is turned around the optical axis OA to make sure that the deflection axis A reaches the target zone C of the retina of the patient. Figure 4 is a front schematic view of the contact lens 1 according to an illustrative embodiment of the invention showing the geometrical configuration of the contact lens 1, for example of a contact as illustrated in figure 1 a or figure 1 b. Only the first face 11 of the contact lens 1 is visible. Considering the contact lens 1 as a clock face, the reference point O is placed at the centre of the clock face, the transversal axis X is located on the three o’clock - nine o’clock line, the vertical axis Y is located on the twelve o’clock - six o’clock line whilst the optical axis OA is perpendicular to the clock face. Still by analogy to the clock face, the contact lens 1 may be divided in a plurality of zones with reference to the different hours. For instance, an element located between two o’clock and three o’clock is in the upper right quarter of the clock face whilst an element located between seven o’clock and eight o’clock is in the lower left quarter of the clock face. Still in reference to figure 4,it is assumed the depicted contact lens 1 is oriented as in the eye of a patient, thereby having a lower end located at the lower portion of the eye and an upper end located at an upper portion of the eye. We assume that the lens body 10 is selfbalanced with a gravity centre placed in O. We also assume that the addition of a prismatic element 20 put in place to reach a specific PRL zone brings about a disequilibrium. We also assume that the gravity centre Gpe of the prismatic element 20 is in the lower right side of the first face 11, by analogy with the clock face. The counterweight element 30 of the contact lens 1 of the invention, once its mass chosen, will be placed to keep the gravity centre Gl of the contact lens 1 (lens body 10 + prismatic element 20 + counterweight 30) at an equilibrium point. For that, we can for example choose a counterweight element 30 with a mass identical to the mass of the prismatic element, its gravity centre Gce being placed in the lower left-side of the first face 11 so that the equilibrium point is at the intersection point between the vertical axis Y and the line (Gce, Gpe). Otherwise said, the counterweight 30 brings about a rebalancing effect. Beyond the above-mentioned example, it should be noted that finally, the position of the prismatic element 20 is imposed by the light deviation to obtain. After that, we have an infinite number of counterweight element masses and positions of the counterweight element that can be suitable to make sure that the calculation of the barycentre (equilibrium point) is on the vertical axis Y and at or below the horizontal axis X. The equilibrium point advantageously has a (x,y) coordinate with a value (0, y < 0) in the plane lens PL, and is thereby located on a lower portion of the vertical axis Y. The equilibrium point may however have a (x,y) coordinate with a value (0,0), indicating that it coincides with the optical centre O of the plane lens PL. The rebalancing effect of the counterweight element 30 is more pronounced when the gravity centre of the prismatic element 20 tends to be in the upper left side, i.e. between nine o’clock and twelve o’clock, or in the upper right side, i.e. between twelve o’clock and three o’clock, of the first face 11, by analogy with the clock face. Indeed, in these configurations, the gravity centre of the prismatic element 20 (gravity centre of the lens body 10 merged with the optical centre O, counterweight not taken into account) is far away from a stable equilibrium point for the contact lens. In the aforementioned example, the gravity centre of the lens body 10 was considered to be merged with the optical centre O of the contact lens 1. Of course, it is not always the case, but the method to find the equilibrium point is the same except we have an additional component in the calculation of the barycentre (equilibrium point) between the lens body 10, the prismatic element 20 and the counterweight element 30. According to an advantageous embodiment illustrated in figure 5, the counterweight element 30 is arranged around the prismatic element 20. This figure only illustrates a component both comprising the prismatic element 20 and the counterweight element 30, not yet integrated within a lens body. This component can be for example integrated within a lens body as that one described with regard to figure 1a or figure 1b. Such a component highly facilitates the manufacturing. According to another configuration (not illustrated), the lens body 10 may comprise parallel plates in addition to the prismatic element, for example of triangular shape. Such a configuration is actually a combination of the embodiments of Figure 1 a and Figure 1 b. Varying the location of the parallel plates allows a variation of the deflection deep of the light. Thus, at constant prismatic element parameters and without rotating the contact lens 1, the deflection deeply varies along the optical axis. Preferably, the parallel plates have a thickness ranging from 0.5 mm to 2 mm. The deflection range may therefore vary from a few tenth of mm to 1 mm, depending on the refractive index of the parallel plates. Figure 6 is a cross sectional schematic view of a contact lens according to another alternative embodiment of the invention. In this embodiment, there is no additional prismatic element having a refractive index different from the refractive index of the lens body but instead a lens body with a given refractive index is shaped of the active faces 11,12, chosen to additionally provide for a prismatic effect to the lens body 10. More precisely, this embodiment proposes a contact lens comprising: - a lens body 10 having an optical centre O and an optical axis OA passing through the optical centre O, said optical axis OA being intended to be aligned with the fovea centralis F of a patient’s retina where the contact lens is installed on a patient’s eye, said lens body 10 having a first active face 11 with a first centre of curvature and a second active face 12 with a second centre of curvature different from the first centre of curvature to provide for a prismatic effect to said lens body 10 so as to enable a deflection of the light along with a deflection axis A, said deflection axis A forming a non-zero acute deflection angle a with the optical axis OA of the lens body 10 and being intended to cross a target zone C of the retina of the patient that differs from the fovea centralis F, - at least one counterweight element 30 arranged to keep a gravity centre Gl of the lens 1 at a stable equilibrium point when the contact lens 1 is turned around the optical axis OA to make sure that the deflection axis A reaches the target zone C of the retina of the patient. In this embodiment, a counterweight 30 is however also necessary to reach a stable equilibrium point for the whole contact lens 1, as the shape of the lens body implies a mass repartition with a gravity centre which is no longer merged with the optical centre. From a mathematical viewpoint, the situation is completely similar to the case presented before in view of the embodiment of figure 1a, wherein there is a lens body equilibrated plus a prismatic element which displaces the gravity centre of the set “lens body plus prismatic element” away from the optical centre.

Claims

1. A contact lens (1) comprising:- a lens body (10) made of a material with a first refractive index (h), having an optical centre (0) and an optical axis (OA) passing through the optical centre (O), said optical axis (OA) being intended to be aligned with the fovea centralis (F) of a patient’s retina where the contact lens is installed on a patient’s eye,- at least one prismatic element (20) made of a material having a second refractive index (r2) different from said first refractive index (n) and intersecting with the optical axis (OA) of the lens body (10) so as to enable a deflection of the light along with a deflection axis (A), said deflection axis (A) forming a non-zero acute deflection angle (a) with the optical axis (OA) of the lens body (10) and being intended to cross a target zone (C) of the retina of the patient that differs from the fovea centralis (F), - at least one counterweight element (30) arranged to keep a gravity centre (GL) of the lens (1) at a stable equilibrium point when the contact lens (1) is turned around the optical axis (OA) to make sure that the deflection axis (A) reaches the target zone (C) of the retina of the patient.

2. A contact lens (1) according to claim 1, wherein the counterweight element (30) is arranged around said at least one prismatic element (20).

3. A contact lens (1) according to claim 1 or 2, wherein said at least one prismatic element (20) is a triangular prism.

4. A contact lens (1) according to claim 3, wherein said triangular prism (20) has a first active face (21) perpendicular to the optical axis (OA) and a second active face (22) forming a prism angle (P) with the first active face (22), said optical axis (OA) intersecting the first and second active faces (21, 22), respectively, at a first and a second crossing points.

5. A contact lens (1) according to claim 4, wherein the prism angle (3) is between 1° and 20° and the second refractive index r2 is between 1.4 and 1.9.

6. A contact lens (1) according to claim 5, wherein the deflection angle (a) is between 1° and 20°.

7. A contact lens (1) according to any of the preceding claims, wherein the lens body (10) and said at least one prismatic element (20) are made of different materials.

8. A contact lens (1) according to one of the preceding claims, comprising two triangular prisms as prismatic elements, said triangular prisms being arranged head to tail.

9. A contact lens (1) according to the preceding claim, wherein said triangular prisms are identical so as to form, together, parallel plates.

10. A contact lens (1) according to claims 1 to 8, wherein the lens body further (10) comprises parallel plates (15).

11. A contact lens (1) according to claim 10, wherein the parallel plates (15) are separated by a thickness between 0.5 mm and 2 mm.

12. A contact lens (1) according to any of the preceding claims, wherein the contact lens (1) is soft, semi-rigid, rigid or a combination thereof.

13. A contact lens (1) comprising:- a lens body (10) having an optical centre (0) and an optical axis (OA) passing through the optical centre (O), said optical axis (OA) being intended to be aligned with the fovea centralis (F) of a patient’s retina where the contact lens is installed on a patient’s eye, said lens body (10) having a first active face (11) with a first centre of curvature and a second active face (12) with a second centre of curvature different from the first centre of curvature to provide for a prismatic effect to said lens body (10) so as to enable a deflection of the light along with a deflection axis (A), said deflection axis (A) forming a non-zero acute deflection angle (a) with the optical axis (OA) of the lens body (10) and being intended to cross a target zone (C) of the retina of the patient that differs from the fovea centralis (F),- at least one counterweight element (30) arranged to keep a gravity centre (Gl) of the lens (1) at a stable equilibrium point when the contact lens (1) is turned around the optical axis (OA) to make sure that the deflection axis (A) reaches the target zone (C) of the retina of the patient.

14. A contact lens (1) according to any of the preceding for use in the treatment of age-related macular degeneration or other macular degeneration.

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