MULTIFOCAL CONTACT LENSES INTRODUCTION

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Mario Giovanzana Milano, 15 th december 00 MULTIFOCAL CONTACT LENSES INTRODUCTION In my professional experience over the years I ve developed both support in the production of contact lense as well

1 Mario Giovanzana Milano, 15 th december 00 MULTIFOCAL CONTACT LENSES INTRODUCTION In my professional experience over the years I ve developed both support in the production of contact lense as well their design and planning with the help of computerized systems that allow me to guarantee their reproduction in time. In the midst of this professional activity, and starting from the know-how I had acquired in the geometry of aspheric lenses, I have been able to realize a project that has led me to the realization of progressive eccentricity multifocal contact lenses, which I have patented in 1988 in Italy and in other countries around the world. Fig,1 1

By using a single dioptric medium, the eccentricity progressive multifocal contact lens insures the correction of visual defects to both long-distance vision with regard myopia or hipermetropia in

All this without limitation of the field of vision. With my system, negative or positive contact lenses Fig.2 e Fig.

2 By using a single dioptric medium, the eccentricity progressive multifocal contact lens insures the correction of visual defects to both long-distance vision with regard myopia or hipermetropia in combination with astigmatism as well as short distance vision, presbyopia. It allows therefore a natural focus, with an optimal vision from far, near and of the so called average distance. All this without limitation of the field of vision. With my system, negative or positive contact lenses Fig.2 e Fig.3 can be constructed of any material, hard or soft, and with positive or negative addition, since it is the external surface of the lens which functions optically while the shape of the internal surface is designed in relation to the shape of the cornea. Fig.2 Fig.3 Therefore it is possible to use the internal surface to correct the astigmatism generating a toric surface. As regards the stabilization of these types of contact lenses will be possible to use, for soft, the systems by now tested and sure which dynamic and prismatic, while for hard the stabilization will come for contact with the toric surface of the cornea. A good stability is fundamental for fitting this type of contact lenses because the movement of the lens determines an image fluctuation for long or short distance vision. 2

vision taking advance of the concentric zone having an aspheric curve with progressive eccentricity.

3 This negative contact lens Fig.4 is based on the principle of a spherical central zone in the planned external surface so as to allow a perfect vision from far in whichever condition of light and an optimal near vision taking advance of the concentric zone having an aspheric curve with progressive eccentricity. It s obvious that fitting this type of contact lens depends in determining way on the well balanced and on the movement of the same in the eye. Fig.4 Only by using a progressive eccentricity curve can the variations in the power of the lens be obtained in such a limited space; and the greater the difference between the correction for long and short distance vision, the more accentuated the progression should be. Fig.5 3

In picture 6 and 7 is demonstrated as it is possible, with a negative lens, to use the central zone for long vision or near vision giving to this the intentional power and consequently to use the

4 In picture 6 and 7 is demonstrated as it is possible, with a negative lens, to use the central zone for long vision or near vision giving to this the intentional power and consequently to use the peripheral zone for near or far vision with a progressive eccentricity course. NEGATIVE MULTIFOCAL CONTACT LENS WITH CENTRAL ZONE FOR FAR AND PERIPHERICAL FOR NEAR VISION Fig.6 NEGATIVE MULTIFOCAL CONTACT LENS WITH CENTRAL ZONE FOR NEAR AND PERIPHERICAL FOR FAR VISION Fig.7 4

5 In picture 8 and 9 it is demonstrated how it is possible, with a positive lens, using a central zone for near or far vision giving to this the intentional power and consequently to use the peripheral zone for far or near vision with a progressive eccentricity course. POSITIVE MULTIFOCAL CONTACT LENS WITH A CENTRAL ZONE FOR NEAR AND PERIPHERICAL FOR FAR VISION Fig.8 POSITIVE MULTIFOCAL CONTACT LENS WITH A CENTRAL ZONE FOR FAR AND PERIPHERICAL FOR NEAR VISION Fig.9 5

CONFIGURATION OF THE SPHERIC ZONE AND PROGRESSIVE ECCENTRICITY ZONE Fig.

6 Picture 10 shows a negative lens with a central zone for far and peripherical zone with progressive eccentricity for near. This kind of configuration allows to obtain the best correction for myopic-presbyopic patients. CONFIGURATION OF THE SPHERIC ZONE AND PROGRESSIVE ECCENTRICITY ZONE Fig.10 Picture 11 shows a positive lens with a central zone for near and progressive eccentricity peripherical zone for far. This kind of configuration allows to obtain the best correction for hypermetropic-presbyopic patients. CONFIGURATION OF THE SPHERIC ZONE AND PROGRESSIVE ECCENTRICITY ZONE Fig.11 6

7 Spherical aberration of a spheric lens Picture 12 shows the spherical aberration of a positive lens. The rays coming from infinite parallels to the optical axis don t form one focal only, crossing the lens, but they form a fire series. The marginal rays, compared with paraxial ones, undergo one grater deviation. Fig.12 The diagram represented in figure 13 evidences that varying the pupillar diameter, the power progrssively increases. Such condition is always present in a spheric lens. Fig13 7

fires. The rays crossing the two central and marginal zone, come had in various way as changes the curvature ray.

8 Spherical aberration of a bifocal lens In picture 14 is represented a positive bifocal spheric lens. The rays coming from infinite parallels to the optic axis don t form a series of fires, crossing the lens but they form two groups of fires. The rays crossing the two central and marginal zone, come had in various way as changes the curvature ray. deviati in modo diverso in quanto cambia il raggio di curvatura. Fig.14 The diagram represented in figure 15 evidences the two groups of fires. Such condition is always present in a bifocal lens. Fig.15 8

This kind of lens is planned to eliminate every type of aberration.

9 Aplanatic lens In figure 16 is represented an aplanatic lens. The rays crossing the lens form an only focal. This kind of lens is planned to eliminate every type of aberration. eliminare ogni tipo di aberrazione. Fig.16 The diagram represented in figure 17 evidences that varying the pupillar diameter the power of the lens doesn t change. Fig.17 9

series in function to the addition for near and to the predestinated area. Fig.

10 Progressive eccentricity lens In picture 18 is represented a progressive eccentricity lens. The rays coming from infinite parallels to the optic axis don t form an only focal, crossing the lens but a fire series in function to the addition for near and to the predestinated area. Fig.18 The diagram represented in figure 19 evidences that the central zone is for near and the peripherical one is for far vision and is used a progressive eccentricity. Fig.19 10

HARD TORIC CONTACT LENSES ASTIGMATISM DEFINITION AND OPTIC BASIS

Mario Giovanzana Milano 20.06.01 HARD TORIC CONTACT LENSES ASTIGMATISM DEFINITION AND OPTIC BASIS An astigmatism, according to Whevell (1817) has been defined as astigmatism or astigmatic ametropia; the