Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Methods of use
Reexamination Certificate
2002-05-23
2004-06-22
Casler, Brian L. (Department: 3737)
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Methods of use
C351S161000
Reexamination Certificate
active
06752499
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to methods and systems for the treatment of myopia progression. In particular, the present invention relates to methods and systems for treating myopia progression in myopic patients who also exhibit near point esophoria, esophoria at near, eso fixation disparity, and/or eso associated phoria.
Myopia, also known as nearsightedness, is a visual defect in which distant objects appear blurred because their images are focused in front of the retina rather than on it causing a retinal blur. Myopia is one of the more prevalent human visual disorders, affecting up to 25% of American adults, with associated cost of correction and management having been estimated at several billion dollars per year. In some regions of the world, up to 75% of people may have myopia. Moreover, the prevalence of myopia may even be increasing. In some instances, high levels of myopia may result in grave consequences, such as, blindness from retinal detachment, myopic macular degeneration, cataract, glaucoma, or severe side effects or complications from myopia correction. Thus, treatments which control, reduce, inhibit, or even reverse myopia progression would have a widespread benefit.
It is believed that myopia may be caused by environmental factors, particularly intensive and excessive near work, with hereditary/genetic factors further defining susceptibility. Numerous animal studies have demonstrated that prolonged hyperopic defocus triggers an increase in eye growth, typically along an axial length of the eye, which can cause myopic change, as shown in FIG.
1
. The dotted line in
FIG. 1
denotes expansion of the eye, particularly the vitreous body by growth of the choroid and/or sclera. Prolonged hyperopic defocus may be caused by naturally occurring refractive errors. More importantly, people engaged in intense near work while in a state of inadequate accommodation (i.e. accommodation deficiencies during near work tasks) often encounter hyperopic defocus. Both accommodation deficiencies and life styles or occupations involving intensive near work result in frequent exposure to hyperopic defocus which in turn induces myopia. It has further been reported in several studies that larger than normal “accommodative lags” have been measured in progressing myopes. The term “accommodative lags” refers to hyperopic accommodative errors during intensive near work.
A number of techniques have been developed over the years to control or prevent myopia progression. These techniques include rigid contact lenses, spectacles, pharmacological delivery of atropine, biofeedback, vision training, and intentional undercorrection. Surgical correction of myopia includes refractive surgery, including myopic keratomileusis, radial keratotomy, and photorefractive keratotomy. While all these techniques have enjoyed varying levels of success, no one of these procedures is proven to provide significant myopia progression reduction or prevention in all cases.
Of particular interest to the present invention is the relationship of decreased accommodation to esophoria at near in defining the causes of progressive myopia. The term “esophoria” refers to a tendency of the eyes to turn inward. About 25% of myopic people have this eye crossing tendency. In particular, near esophoria or near point esophoria may cause decreased accommodation of the eyes during near work tasks, increasing accommodation lag. This may induce hyperopic defocus and ocular growth and thus drive myopia progression. Alternatively, decreased accommodative response may be compensated by convergence accommodation which in turn causes esophoria.
Several studies have suggested the use of bifocal spectacles or glasses to reduce the rate of myopia progression in near point esophoric children. While these proposals appear promising, they have not provided the desired evidence of myopia progression control. Moreover, the use of bifocal spectacles suffer from several inherent disadvantages that may limit their effectiveness in myopia control. For example, bifocal power is often avoided or improperly used by children (e.g. not lowering their gaze to read through the bifocal power or raise their chin to view a computer screen through the bifocal power) as well as the fact that bifocal spectacles do not provide coverage for all angles of view.
In light of the above, it would be desirable to provide improved methods and systems for the treatment of myopia progression. In particular, it would be desirable to provide improved methods and systems for controlling myopia progression in near point esophoric myope patients with a significant level of success. It would be further desirable if such treatment methods could not be avoided or used incorrectly by the patient and provide sufficient coverage for all angles of view. At least some of these objectives will be met by the invention described hereinafter.
2. Description of Background Art
Myopia progression control using bifocal contact lenses is described in a poster abstract by T. A. Aller and D. Grisham in
Optometry and Vision Science
, Vol. 77, No. 12s, Poster 92, page 182 (December 2000). Bifocal spectacle control of myopia progression in children with nearpoint esophoria is described by Goss et al. in
Optometry and Vision Science
, 67:637-640 (1990) and Goss et al. in
Journal of Optometric Vision Development
, 30:25-32 (1999). Progressive spectacles in slowing myopia is described by Leung et al. in
Optometry and Vision Science
, 76:346-54 (1999). An editorial by J. T. Barr in
Contact Lens Spectrum
, August (1999) speculates on the use of soft bifocal contact lenses for treating myopes. U.S. Pat. No. 6,045,578 describes the use of contact lenses to alter a degree of spherical aberration stop or slow myopia. U.S. Pat. No. 5,838,419 describes a method for treating myopia by altering the spectral distribution of incident light on the eye by filter or tints provided on contact lenses. U.S. Pat. Nos. 5,695,509 and 3,760,807 describe optical molds applied as hard contact lenses to reshape a surface of the cornea to reverse myopia.
The full disclosures of each of the above references are incorporated herein by reference.
BRIEF SUMMARY OF THE INVENTION
The present invention provides new methods and systems for treating myopia progression in myopic patients who also exhibit near point esophoria, esophoria at near, eso fixation disparity, and/or eso associated phoria by selectively prescribing bifocal (soft or rigid gas permeable) contact lenses to such patients. In particular, the myopigenic effects of accommodation lag during intensive near work and hyperopic defocus are addressed by treating patients who also suffer from near point esophoria. The present invention further provides a significant level of success in controlling myopia progression in esophoric myopes through the prescription of bifocal contact lenses. Bifocal contact lenses advantageously allow for effective myopia progression control as most bifocal contacts act on the principal of simultaneous vision where add powers are available independent of gaze. As such, it is less likely that a bifocal contact lens patient can avoid use of the bifocal power or otherwise use it incorrectly. Moreover, bifocal contact lenses provide sufficient coverage for all angles the eye may scan.
In a first aspect, the present invention provides methods for selectively prescribing bifocal contact lenses for controlling myopia progression. One method comprises identifying a myopic patient who exhibits near point esophoria, eso fixation disparity, or eso associated phoria, measuring an amount of fixation disparity, and prescribing a bifocal contact lens add power prescription. The bifocal near power prescription is based on the fixation disparity measurement and the bifocal distance prescription is based upon a distance prescription of the patient's eye.
Common ophthalmic measurements, such as alternating cover test, Van Graefe phoria test, Maddox rod phoria test, Titmus vision screening, vec
Casler Brian L.
Sanders John R
Townsend and Townsend / and Crew LLP
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