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William J. Benjamin Alabama Eye & Cataract Center, P.C. Michelson Laser Vision, Inc. Material Performance Assessments, LLC Birmingham, Alabama Presented in St. Gallen, Switzerland at the 44th Congress of the INTERNATIONAL SOCIETY OF CONTACT LENS SPECIALISTS August 31, 2015 Interesting Factors on Myopia Control using Contact Lenses William J. Benjamin, OD, PhD Several points should be made in the raging debate about the use of contact lenses to limit the incidence, progression, and severity of myopia: 1. Elimination of peripheral hyperopic defocus or achievement of peripheral myopic defocus aren’t solely performed by contact lenses intended to alter the peripheral refraction. The central retina is also defocused. Myopic progression could be due to central and/or peripheral defocus. 2. Much like in presbyopia, when a bifocal or multifocal contact lens simultaneously covers portions of the pupil with distance, near, and intermediate corrective powers, the focus at the fovea and macula will be degraded. One must investigate the effects of central defocus on the developing visual system before such lenses can be embraced. 3. It is theorized that corneal shaping by orthokeratology allows a peripheral annulus of relatively steeper cornea outside the flattened central zone. This provides a correction for peripheral defocus. Another factor could be that the normally prolate corneal surface is made more spherical. 4. The optical system of the eye may require peripheral defocus to avoid adverse effects of sunlight and ultraviolet radiation. One must investigate peripheral retinal thinning, lattice degeneration, and perhaps other effects of peripherally focused light and radiation, before myopia control with contact lenses can be recommended. The author suggests that members and associates of the International Society of Contact Lens Specialists take the lead in bringing these points up for future discussion. Alabama Eye & Cataract Center, P.C./Michelson Laser Vision, Inc. (January 1, 2015). Material Performance Assessments, LLC (Oct. 1, 2014). Existing, prior research contracts with companies in 12 countries and 15 states in USA. Evaluation of oxygen permeability and/or transmissibility for over 200 prototype and production materials in the form of contact lenses, intraocular lenses, stromal implants, polymeric coatings, and in situ polymerizing hydrogels. Expert witness for U.S. Patent Office (2010-2013), Johnson & Johnson Vision Care (20042009), Bausch & Lomb, Inc. (1999-2004). FDA Microbiology Workshop Consultant, for Alcon Laboratories, Vision Care Division (2014). Consultant, for Coopervision, Inc. (2014-15). No proprietary interest in any product in the contact lens field. Editor/Author, Borish’s Clinical Refraction (Publisher: Elsevier, Inc.) President, International Society of Contact Lens Specialists. Secretary, American National Standards Institute (ANSI), Z80 Committee on Ophthalmic Products. Council Member, International Society for Contact Lens Research. Member and Former Chair, American Optometric Association, Commission on Ophthalmic Standards. Member, National Academies of Practice, National Academy of Optometry. Petzval surface Ideally, in an optical system with flat image plane, the Petzval surface should be flat -- but it is curved! The back of the eye is curved, too. How lucky is that? Idea : Curve the eye’s Petzval surface to match the retinal surface? Flat image plane Petzval surface Theoretically, where is the Petzval surface relative to the retina? Reduce the eye to most essential optical elements: Helmholtz Reduced Eye Constructs of peripheral ametropia Peripheral emmetropia Peripheral hyperopic defocus: theoretical instigator of myopia! Peripheral myopic defocus: theoretical savior of myopia! Ocular Petzval surface Idea : Create peripheral emmetropia or myopic defocus with SCLs! How are contact lenses to be used to attempt the elimination of peripheral hyperopic defocus? Soft contact lenses with oblate front surfaces on the eye Distance-center soft lens multifocals, or similar lenses that are oblate Distance-center soft lens bifocals, or similar lenses Refractive power becomes more plus away from center of lens Corneal reshaping with rigid contact lenses Annular zone of steepening at edge, similar to soft lens bifocal Prolate cornea becomes spherical I have a sense of déjà vu ! Central vision will be diminished Spherical aberration has been increased Entire optical aperture contributes to foveal image Proof: For better visual acuity, -0.25 or -0.50 D will be added over the distance-center lens Peripheral lens power affects central vision, too A central veiling luminance will be present What are the functional visual deficits and long-term visual effects of chronic blur at the fovea for a young person? The Coroneo effect: Visible (blue ?) and ultraviolet (UV) radiation Light incident from temporal and superotemporal, 30º behind iris plane Focuses nasally through the cornea Nasal pingueculae and pterygia Nasal and inferonasal cataract formation When focused, incident peripheral light and UV radiation can have negative impacts on the eye Peripheral retinal atrophy: Lattice degeneration, retinal thinning Thought to be more common in high myopes due to retinal stretching Equatorial, often inferotemporal, with or without atrophic retinal holes A risk factor for retinal detachment Fibrotic peripheral areas might be the result of lack of adequate capillary perfusion with nutrients and oxygen Another theory: Unfocused peripheral light and UV radiation affect the tissue over many years If now, peripheral light & UV radiation are more focused using special lenses for myopia control? Is peripheral blur needed for ocular health? We avoid looking at the sun but radiation still hits our peripheral retinas with intensity Are we interfering with a natural protective mechansim? Microbial keratitis At 5 cases per 10,000 CL wearers in daily wear, if 50% of all persons 10−25 yrs old wear CLs, this is: 78,340 cases in India, per year 69,140 cases in China 31,870 cases in the USA 20,500 cases in Europe Acanthamoeba keratitis At 20 cases per million CL wearers, if 50% of all persons 10−25 yrs old wear CLs, this is: 3,140 cases in India, per year 2,765 cases in China 1,275 cases in the USA 820 cases in Europe Caution The theory of myopia control based on peripheral defocus is not yet proof Use of multifocal or progressively powered contact lenses may have unanticipated, unwanted consequences The risks of contact lens wear are significant and must be balanced against the potential benefit Indiscriminate wear of contact lenses for myopia control is problematic Great hopes … That myopia can be controlled by wearing contact lenses Stem from Practitioners, Academic & Other Researchers, and CL Industry Previously: Bifocal and multifocal soft contact lenses for presbyopia Previously: Silicone-hydrogel lenses were going to solve extended wear Currently: Certain dry eye products, diagnostic techniques, clinical and scientific concepts are overhyped by what has been called the “dry eye combine,” also a “dry eye racket,” or as Dwight Eisenhower might have said, dry eye’s “clinico-academic industrial complex” Be aware of the potential emergence of myopia control’s clinico-academic industrial complex Dwight D. Eisenhower, US President 1953-61; Farewell Speech Jan. 17, 1961.
