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Published byHenry Briggs Modified over 9 years ago
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Author: Roger F. Steinert, M.D. Dr. Steinert is a paid Medical Monitor for ReVision Optics
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Near Power in Pupil Center Distance Power in Pupil Center Pinhole Effect
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Excimer ablation implemented with either PRK or LASIK is used to alter the anterior corneal surface, creating either a “near center” or “distance center” ablation profiles. Not FDA approved. US Patent 6 280 435 B1 US Patent 6 969 386 B2
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The INTRACOR® (Technolas Perfect Vision) procedure causes steepening of the central cornea by cutting a set of concentric cylinders. The width of the cylinders is very small, resulting in minimal loss of corneal tissue. The cuts begin below Bowman’s layer and extend through most of the stromal thickness (see cross-sectional sketch below). The cylindrical boundaries facilitate remodeling of the stroma, causing an increased central corneal curvature and a resulting near center zone. Not FDA approved.
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The KAMRA™ (formerly AcuFocus) intracorneal inlay is an opaque, polyvinylidene flouride, 3.8 mm diameter ring with a 1.6 mm diameter central opening. It is 5 microns thick and the body is fenestrated with 8400 randomly placed holes to facilitate nutritional flow. Application of the pinhole effect to the human dioptric awaits the judgment of the ongoing US Clinical trial (KAMRA™ ). KAMRA™ Corneal Inlay Contact Lens
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The PresbyLens® (ReVision Optics®) is a clear, 2 mm diameter, sub 50 micron thick, hydrogel inlay placed under a LASIK-like flap, which steepens the central corneal curvature – creating a near center zone. The inlay has no intrinsic power ; its index of refraction is the same as the cornea’s. In FDA clinical trial. The Flexivue™ (Presbia™) intracorneal micro-lens is a 3 mm diameter, hydrophilic polymer disk with a 20 micron edge thickness. The center has no intrinsic power, creating a distance center zone for emmetropes, while the peripheral “donut” has additional intrinsic refractive power for near. Not FDA approved. PresbyLens Inlay
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Near Center LASIK Profile: 6m Data; (1) J Ref Surg, 2009 25(1-suppl) : S148-S155 Near Center LASIK Profile: 6M Data; (2) J Cataract Ref Surg, 2008 34(2): 205-210 Near Center Stromal Relaxing Profile (Intracor): 3M Data; (3) J Ref Surg, 2009 25(10): 855-861 Pinhole Mechanism (AcuFocus): 24 M Data; (4) J Ref Surg, 2010 26(10): 707-715 Near Center Corneal Elevation Change (PresbyLens): 3M Data; (5) ReVision Optics, September 2010
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Pinhole Mechanism (AcuFocus): 24 M Data; (4) J Ref Surg, 2010 26(10): 707-715 Near Center Corneal Elevation Change (PresbyLens): 3M Data; (5) ReVision Optics, September 2010
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Near Center LASIK Profile: 6m Data; (1) J Ref Surg, 2009 25(1-suppl) : S148-S155 Near Center Stromal Relaxing Profile (Intracor): 3M Data; (3) J Ref Surg, 2009 25(10): 855-861 Pinhole Mechanism (AcuFocus): 24 M Data; (4) J Ref Surg, 2010 26(10): 707-715 Near Center Corneal Elevation Change (PresbyLens): 3M Data; (5) ReVision Optics, September 2010
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Easily Reversible Maximizes Available Light “Wow” Factor (Rapid Visual Improvement) Cosmetic Appeal Refractive Inlays Pinhole Inlays ___ PresbyLASIK / PRK ___ Laser Remodeling of Stroma ___
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All procedures examined provide a clear improvement in uncorrected near acuity, with only a minor loss in uncorrected distance acuity. Of the solutions discussed, the PresbyLens® appears to give best correction of near and intermediate vision whereas PresbyLASIK from Nidek results in the least loss of distance vision. Very good near and intermediate visions provided by hydrogel corneal inlays, as well as reversibility, are attractive though very long term biocompatibility is yet to be proved. “Wow factor” is a plus. The reversibility of pinhole inlays is attractive though very long term biocompatibility is yet to be proved and reduced light may result in reduced vision in low light. Use of a femtosecond laser system alone is attractive though long- term corneal stability is yet to be proved and reversibility may prove difficult. “Wow factor” is a plus. Not compatible with prior or simultaneous LASIK. LASIK solutions are attractive though reversing the procedure may prove difficult and stability may be suboptimal.
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