Annular mask contact lenses

#This invention concerns vision correction and, in particular, annular mask contact lenses and related methodology.

#Contact lenses are commonplace today. Most individuals with minor vision ailments can quickly acquire and use these lenses in place of prescription eye glasses. This is not true, however, for individuals stricken with poor vision or even for those presbyopic persons requiring bifocal glasses. These individuals are left with little choice in selecting contact lenses; and the lenses which are available typically encumber these patients with other difficulties. For example, presbyopic individuals can opt for bifocal contact lenses, but usually find it difficult to maintain focus during eye movement, or only see clearly at one viewing distance.

#The long felt need to develop more versatile lenses has led designers to pinhole contact lenses. These lenses endeavor to utilize the known theories of pinhole imaging, commonly understood in optics as a method to reduce geometrical aberrations, e.g., astigmatism, spherical aberration, and coma. By restricting a person's vision to a small "pinhole" aperture, visual deficiencies are greatly reduced or effectively removed. Unfortunately, the utility of this technology has been diluted because of designs and approaches inappropriate for corrective optometry. For upwards of 50 years pinhole contact lenses have been under consideration, yet they remain today commercially unsuccessful and largely unavailable. As a result, patients afflicted with relatively poor vision are typically unaided by contact lenses.

#For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description and the accompanying drawings, in which:

#FIG. 1 is a plan view of an annular mask contact lens constructed in accordance with the invention;

#FIG. 1A is a diametrical sectional view of the lens of FIG. 1.

#FIGS. 1 and 1A show a contact lens 10 constructed in accordance with the invention having a transparent lens body 12 fabricated with two curvatures, a concave surface 14, and a convex surface 16. The concave surface 14 is optically powered to adapt to the patient's eye curvature. The convex surface 16 is optically powered to correct the patient's vision for an intermediate distance, typically midway between near and far objects. Focusing is achieved both by the contact lens 10 and by the eye's own refractive capability.

#The contact lens 10 has an annular light-blocking mask 18 This annular mask 18 is optically arranged to form a small, pinhole-like aperture 20 at approximately the center of the lens body 12 and at the patient's optical line-of-sight 22.

#Constructed in this fashion, the contact lens 10 operates as a pinhole imager and increases the depth of focus. Light rays from a single object in the field of view, and entering the pinhole aperture 20, are more tightly imaged at the retina than in the absence of the lens 10. This reduces the blurring at the retinal image and increases the patient's visual acuity. Normally, the typical geometrical vision deficiencies encountered in patients, like myopia, hyperopia, astigmatism, and presbyopia, spread out the light rays reaching the retina from a single object point in the field of view, thereby reducing image contrast. The pinhole aperture 20 limits these light rays to a small bundle entering the eye pupil, and thereby improves image contrast. Visual acuity is also improved over a large range of viewing distances because defocus effects are less noticeable with the reduced blurring of the image at the retina.