Orthokeratological contact lenses and design methods therefor

#The present invention is directed generally to contact lenses and more particularly to rigid orthokeratological contact lenses and methods for prescribing the same.

#Millions of people experience difficulties with their vision due to a number of common refractive conditions such as myopia (nearsightedness) and hyperopia, (farsightedness). Myopia is a visual abnormality where an eye cannot focus on far-away objects because the cornea is curved too steeply and/or the eye is elongated axially front to back, such that it fails to provide a sharp focus of light at the retinal plane of the eye. On the other hand a hyperopic eye cannot focus on either far or near objects because the curvature of the cornea of the eye is too flat and/or too short axially front to back to provide adequate focusing at the retinal plane of the eye.

#Another common refractive vision problem is astigmatism, which may exist alone or in combination with either myopia or hyperopia. With astigmatism, unequal curvatures of one or more refractive surfaces of the eye prevent light rays from focusing sharply at the plane on the retina, thereby resulting in blurred vision. Yet another common vision problem is presbyopia, which may occur with other refractive problems such as hyperopia, myopia, and/or astigmatism. Presbyopia is the most common vision problem in adults 40 years of age and older. At this age, many people begin to experience difficulty focusing on close objects, most commonly due to the loss of flexibility of the eye's focusing apparatus.

#FIG. 1 (prior art) illustrates a cross sectional view of a cornea illustrating the cornea's five layers of tissue.

#FIG. 2 (prior art) illustrates a cross sectional view of a cornea illustrating a known approach to an orthokeratological reshaping of the cornea by central corneal thinning.

#FIG. 3 illustrates a cross sectional view of an embodiment of an orthokeratological contact lens for reshaping a patient's cornea by epithelium tissue movement, in accordance with the principles of the present invention.

#In the following paragraphs, the present invention will be described in detail by way of example with reference to the attached drawings. Throughout this description, the preferred embodiment and examples shown should be considered as exemplars, rather than as limitations on the present invention. As used herein, the “present invention” refers to any one of the embodiments of the invention described herein, and any equivalents. Furthermore, reference to various feature(s) of the “present invention” throughout this document does not mean that all claimed embodiments or methods must include the referenced feature(s).

#The present invention is directed to contact lenses, methods of producing the contact lenses, methods of prescribing the contact lenses and methods of treatment of myopia using the contact lenses. Particularly, each contact lens preferably is designed based on physiological and anatomical considerations of a patient's eye to obtain a rapid and predictable orthokeratological change in the refractive power of the eye for the purpose of correcting myopia.

#Referring to FIG. 3, a cornea 10 having centerline 20 is depicted for treatment with a parabolic contact lens 14 having an inner surface facing epithelium 12. Epithelium 12 includes an outer surface 13 and an inner surface 16. In accordance with the principles of the present invention, in a pre-treatment configuration, outer surface 13 of epithelium 12 does not conform to the contours of the inner surface of contact lens 14 such that there exits a gap 18 or hypertrophy volume 18 between the epithelium 12 and the contact lens 14. The hypertrophy volume 18 is created due to the relative flatness of the contact lens 14 relative to cornea 10. The contact lens 14 helps reshape the cornea 10 when worn by a patient because over time the epithelium 12 conforms the contours of the inner surface of contact lens 14 as outer surface 13 moves outwardly toward contact lens 14. Outward movement in this context refers to movement of the outer surface 13 toward contact lens 14 (e.g., as may be caused by epithelium or stromal tissue growth) and does not refer to migration of epithelium cells such as that caused by conventional orthokeratology treatments. After the contact lens 14 has been worn by the patient for a sufficient amount of time, the hypertrophy volume 18 is filled by the outward movement of epithelium 12, thereby achieving the desired refractive adjustment of the eye.