WO2013015743A1

WO2013015743A1 - Optical lens for slowing myopia progression

Info

Publication number: WO2013015743A1
Application number: PCT/SG2012/000255
Authority: WO
Inventors: Seang Mei Saw; Siu Yin Carly LAM; Chi-Ho TO; Yan-Yin TSE
Original assignee: National University Of Singapore; The Hong Kong Polytechnic University
Priority date: 2011-07-27
Filing date: 2012-07-17
Publication date: 2013-01-31
Also published as: CN104094164A; CN104094164B; TW201307942A; TWI561885B

Abstract

An optical lens for a human eye is disclosed herein. In a described embodiment, the optical lens is in the form of a contact lens 100 which comprises a plurality of alternating optic zones 102 arranged between a centre 104 and a periphery 106 of the contact lens 100. The alternating optic zones 102 include a plurality of annular vision correction regions CZ₁CZ₅ having first refractive powers for correcting myopic refractive errors to create a focused retina image. The first refractive powers are more hyperopic at the lens' periphery 106 than at the lens' centre 104. The optic zones 102 further includes a plurality of annular vision defocus regions DZ₁DZ₅ having second refractive powers for creating a defocused retina image, wherein the plurality of annular vision defocus regions (DZ₁DZ₅) are arranged to alternate with respective ones of the plurality of annular vision correction regions (CZ₁CZ₅). With such a configuration, the contact lens 100 is useful for slowing myopia progression.

Description

Optical Lens for Slowing Myopia Progression

Background and Field of the Invention The invention relates to an optical lens for slowing myopia progression, particularly but not exclusively to a contact lens.

The economic costs of myopia have been estimated to be $250 million per year in the United States. Adults with high myopia may have blinding ocular complications such as retinal tears and macular degeneration. The prevalence rates of myopia are highest in adults in urban Asian cities, including Singapore (38.7%) and lower in the United States (22.7%). The myopia rates are 27.8% in 7 year old Singapore children. It is of paramount importance to elucidate efficacious interventions that may decrease myopia progression.

Optical interventions such as multifocal spectacles and contact lenses (CL) have not been proven to slow myopia progression. Only atropine and pirenzipine may effectively retard progression, but possible long-term side effects preclude recommendation to the general population.

There are approximately 220,000 myopic children between 5 to 16 years in Singapore. All myopic children worldwide could wear the CL till adulthood and benefit from the intervention. As 83% of young Singapore adults are myopic, this problem is of growing concern.

It is an object of the invention to provide an optical lens which addresses the disadvantages of prior art and/or to provide the public with a useful choice.

Summary of the Invention

In a first aspect, there is provided an optical lens for a human eye, the optical lens comprising a plurality of alternating optic zones arranged between a centre and a periphery of the optical lens, the alternating optic zones including (i) a plurality of annular vision correction regions having first refractive powers for correcting myopic refractive errors to create a focused retina image, the first refractive powers being more hyperopic at the lens' periphery than at the lens' centre; and (ii) a plurality of annular vision defocus regions having second refractive powers for creating a defocused retina image, the plurality of annular vision defocus regions arranged to alternate with respective ones of the plurality of annular vision correction regions. . With such an arrangement, it has been found that this is more effective in slowing progression of myopia, especially in children.

Preferably, respective ones of the plurality of the annular vision correction regions and the annular vision defocus regions are grouped as pairs for deriving the corresponding first and second refractive powers in the same pair. In this way, the first refractive powers may be derived based on:

where:

x is refractive error of the human eye;

n is the number of pairs; and

i is pair number of the annular vision correction region and annular vision defocus region.

The second refractive powers may be derived based on:

(_X+ 2Q - 1) _D)+2_,5D_i

n -l

where:

x is refractive error of the human eye;

n is the number of pairs; and

Preferably, the optical lens further includes four or more alternating optic zones. More particularly, the optical lens includes even number of alternating optic zones such as 4, 6, 8, 10, 12 zones. Advantageously, there are ten alternating optic zones.

The first refractive powers may include varying refractive power values for each of the plurality of vision correction regions. The second refractive powers may also include varying refractive power values for each of the myopic defocus regions. It should be appreciated that the optical lens may be in the form of a contact lens, or as a lens of a spectacle. Brief Description of the Drawings

An example of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 illustrates a contact lens having ten optic zones for correcting myopic refractive error of -3.00D according to an embodiment of this invention;

Figure 2 is a schematic diagram showing effects of the contact lens of

Figure 1 on a myopic eye;

Figure 3 shows a contact lens having ten optic zones for correcting myopic refractive error of -2D as a variation to the contact lens of Figure 1 ;

Figure 4 shows a contact lens having ten optic zones for correcting myopic refractive error of -4D as a variation to the contact lens of Figure 1 ;

Figure 5 shows a contact lens having eight optic zones for correcting refractive error of -3D as a variation to the contact lens of Figure 1 ; and

Figure 6 shows a contact lens having six optic zones for correcting refractive error of -3D as a variation to the contact lens of Figure 1.

Detailed Description of Preferred Embodiment Figure 1 illustrates an optical lens 100 in the form of a contact lens (CLs) according to an embodiment of this invention. The contact lens 100 is preferably of the daily disposable soft type with increasing peripheral hyperopia and alternating myopic defocus zones to decrease or retard myopia progression. The contact lens 00 comprises a plurality of alternating optic zones 02 for correcting myopic refractive error of -3.00 diopters(D), and in this embodiment, there are ten optic zones 102. The ten optic zones 102 starts from a centre 104 to periphery 106 of the contact lens 100 and having varying refractive or optical powers at each optic zone 102 distributed between the centre 104 to the periphery 106 in the following manner: x, X+2.5D, (X+0.5D), (x+0.5D)+2.5D, (x+1.0D), (x+1.0D)+2.5D, (X+1.5D), (x+1.5D)+2.5D, from the centre to the periphery of the ten optic zones 102 are -3.0D, -0.5D, -2.5D, 0D, -2D, +0.5D, -1.5D, +1 D, -1 D, and +1.5D. In this embodiment, the optic zones 102 are annular or concentric rings with an equal width share covering the pupil area. The alternating optic zones 102 includes a number of annular vision correction zones (or simply "clear zones" (CZ)) for creating a focused image at the retina and a number of annular vision defocused regions (or simply "defocus zones" (DZ)). In Figure 1 , there are five clear zones CZ: CZ^ CZ₂, CZ₃, CZ₄ and CZ₅ arranged to alternate with the five defocus zones DZ: DZi, DZ₂, DZ₃, DZ₄ and DZ₅.

As it can be appreciated, the clear zones (CZ) of Figure 1 include refractive power values to compensate for any peripheral hyperopic defocus which may occur if the clear zones CZ do not accurately correct for the more hyperopic refractive error found in the periphery. Specifically, the refractive power values for the clear zones (CZ) are (X+0.5D), (X+1.0D), (X+1.5D) and (X+2.0D) resulting in values of -2.5D, -2.0D, -1.5D and -1.0D as shown in Figure 1. In other words, the refractive powers are more hyperopic at the periphery 106 of the contact lens 102 than near or at the centre of the lens in order to create a focused image at the retina. The defocus zones (DZ), on the other hand, have refractive powers arranged to create a defocused retina image and in this embodiment, the defocus zones (DZ) have the following refractive powers: X+2.5D, (x+0.5D)+2.5D, (x+1.0D)+2.5D, (x+1.5D)+2.5D, and (x+2.0D)+2.5D to give values of -0.5D, 0D, +0.5D, +1 D and +1.5D. Figure 2 is a schematic diagram showing effects of the contact lens 100 on a myopic eye 200. Light rays 202 entering the contact lens 100 via the clear zones CZ are focused onto the retina 206 at a focus point FP(CZ) for the clear zones CZ to create a focused image FP(CZ) due to the varying refractive powers which are more hyperopic or are greater at the periphery 106 than at the centre 104 of the contact lens 00. Simultaneously, light rays 204 entering the contact lens 00 via the defocus zones DZ are focused at a focus point FP(DZ) for the defocus zones DZ in front of the retina 206 due to the refractive powers of the defocus zones DZ.

As it can be appreciated, the contact lens 100 corrects myopia while also compensating for peripheral hyperopic defocus and thus, the contact lens 102 provides The contact lens 100 has multi-annular zones configured for different functions to more effectively treat or combat myopia, particularly in children. The contact lens also slows the progression of myopia. It is envisaged that the configuration of the contact lens 100 may be extended to any number of optic zones 02 and/or for compensating different refractive errors. This may be achieved by grouping the clear zones (CZ) and the defocus zones (DZ) into pairs of zones. For any 'n' pairs of zones (n≥2), the refractive power distribution which would be more hyperopic at the periphery for the clear zones CZ and the corresponding defocus zones DZ in the same pair may be generalised as (from the centre 104 to the periphery 106):

Clear Zone: ( + ^^{' " 1}) D)— — (1 ); and ·

M -1

Defocus Zone: (x+ ^{2(;' ~ 1)} D)+2.5D (2);

n - l

where

x = refractive error;

i = pair number of the zone.

In the example of Figures 1 and 2, it would be appreciated that the clear zones CZ and the defocus zones DZ are already grouped into pairs based on the subscripts:

Pair l : (CZ!, D¾);

Pair 2: (CZ₂, DZ₂);

Pair 3: (CZ_3> DZ₃);

Pair 4: (CZ₄, DZ₄); and

Pair 5: (CZ_5l DZ₅).

Based on equations (1) and (2), taking Pair 3 as an example, with the pair number, i=3 and n=5 and for correcting a refractive error, x, of -3D, the corresponding refractive powers of CZ₃, DZ₃ are:

CZ₃ = -2D

DZ₃ = +0.5D; which are the values shown in Figure 1. Based on equations (1 ) and (2), power distributions of a 10-zgne contact lens to compensate for different refractive errors (-2D, -3D, -4D and -5D) are shown in Table 1 below.

Table 1

For all the refractive powers, it should be appreciated that, the refractive power at the periphery (i.e. clear zone CZ₅) would be more hyperopic than the refractive power at the centre (i.e. clear zone CZ .

Figure 3 shows a contact lens 300 for compensating refractive error of -2D and which has the refractive power distribution of Table 1 for ten alternating optic zones 302. Figure 4 shows a contact lens 400 for compensating refractive error of -4D and which has the refractive power distribution of Table 1 for ten optic zones 402.

It is also envisaged that the embodiment of Figure 1 may be extended to different zones, similarly based on the equations (1 ) and (2). Table 2 shows the refractive powers to achieve more hyperopic effects at periphery of a contact lens having 8, 6 and 4 optic zones for correcting refractive error of - 3D:

Figure 5 illustrates a contact lens 500 having eight alternating optic zones 502 (i.e. n=4 pairs) for compensating refractive error of -3D. The eight optic zones 502 are configured to have refractive powers based on Table 2 to be more hyperopic at the periphery of the contact lens 500. Figure 6 illustrates a contact lens 600 having six alternating optic zones 602 (i.e. n=3 pairs) for compensating refractive error of -3D. The six optic zones 602 are configured to have refractive powers based on Table 2 to be more hyperopic at the periphery of the contact lens 500.

The described embodiment is not to be construed as limitative. In the described embodiment, it is proposed to use a soft lens with myopic defocus and increasing peripheral hyperopia. However, other types of lens are envisaged for example, rigid ones. The shape and size of the contact lens may be varied and likewise the contact lens may be adapted to slow myopia for different levels of myopia. For example, the lenses may have 8mm, 8.3mm and 8.6mm in curvature with 13.5, 13.8 or 14 mm in diameter. The centre thickness for refractive power of -3.00D is 0.12mm. For each additional refractive power, a pair of inserts may be developed using a mould base. The widths of the optic zones 102 are illustrated/described to be equidistant but this may not be so and the width of the optic zones 102 may vary accordingly.

Also, although the described embodiment uses contact lens as an example, it should be appreciated that the embodiment may be adapted for other types of optical lens for example, an optical lens used for spectacles/glasses. Although the described embodiment may be used for spectacles, this may not be preferred. This is because of inevitable ocular movement that is associated with changing gaze fixation which alters registration between the spectacle lens and the eye position. On the other hand, contact lens are fixed and centered around the pupil and thus the contact lens move along with the movement of the eye and this can overcome the limitation of continuous changing fixation glaze in humans, particularly children.

In the described embodiment, the contact lens has multi-annular zones (≥4) designed for different functions to more effectively treat myopia and thus, it should be appreciated that the contact lens 100 may be configured with any number of zones depending on application.

Having now fully described the invention, it should be apparent to one of ordinary skill in the art that many modifications can be made hereto without departing from the scope as claimed.

Claims

1. An optical lens for a human eye, the optical lens comprising a plurality of alternating optic zones arranged between a centre and a periphery of the optical lens, the alternating optic zones including

(i) a plurality of annular vision correction regions having first refractive powers for correcting myopic refractive errors to create a focused retina image, the first refractive powers being more hyperopic at the lens' periphery than at the lens' centre; and

(ii) a plurality of annular vision defocus regions having second refractive powers for creating a defocused retina image, the plurality of annular vision defocus regions arranged to alternate with respective ones of the plurality of annular vision correction regions.

2. An optical lens according to claim 1 , wherein respective ones of the plurality of the annular vision correction regions and the annular vision defocus regions are grouped as pairs for deriving the corresponding first and second refractive powers in the same pair.

3. An optical lens according to claim 2, wherein the first refractive powers are derived based on:

(_X+ 2Q -1) _D)|

n - l

where:

x is refractive error of the human eye;

n is the number of pairs; and

4. An optical lens according to claim 2 or 3, wherein the second refractive powers are derived based on:

(_x+ 2(» - l) p)+2,5D,

n - l

where:

x is refractive error of the human eye;

n is the number of pairs; and i is pair number of the annular vision correction region and annular vision defocus region.

5. An optical lens according to any preceding claim, further including four or more alternating optic zones.

6. An optical lens according to any preceding claim, wherein there are ten alternating optic zones.

7. An optical lens according to any preceding claim, wherein the first refractive powers include varying refractive power values for each of the plurality of vision correction regions.

8. An optical lens according to any preceding claim, wherein the second refractive powers include varying refractive power values for each of the myopic defocus regions.

9. An optical lens according to any preceding claim, wherein the optical lens is in the form of a contact lens.

10. A spectacle including the optical lens of any of claims 1-8.