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Custom Manipulation of Corneal Asphericity (The Q Factor)

  • Fernando Faria-Correia
  • Renato AmbrósioJr
  • José Ferreira Mendes
  • Arthur B. Cummings
Chapter

Abstract

When ablating the cornea with a myopic wavefront optimized (WFO) or aberration-free profile, the cornea is always going to receive more ablation in the centre than in the periphery of the optical zone and this will lead to the induction of spherical aberration. With manipulation of corneal asphericity, the final corneal asphericity can be influenced to preserve more natural prolateness than would otherwise occur. Asphericity-guided (Q-adjusted) procedures can also be used to induce corneal asphericity that enhances depth of field (hyper-prolate cornea). This is sometimes used in procedures called “Advanced monovision” due to the fact that the reading eye has better distance vision than would be the case in a patient with straight-forward monovision. Additional reasons for using an asphericity-guided ablation profile would be that for higher myopic corrections, the ablation depth is usually less than with a wavefront-optimised profile. Additionally, the refraction can be refined to 0.01D and the optical zone can be increased in 0.1 mm increments as opposed to 0.5 mm increments in WFO treatments. The target-Q can also be used to either attempt to preserve the preoperative Q-value (that is, not inducing any change) or a different Q-value could be targeted to create negative asphericity and increased depth of field for advanced monovision treatments.

Keywords

Asphericity Prolate Hyper-prolate Improved contrast sensitivity Tissue saving Increased depth of focus Q-guided Asphericity-guided Wavefront optimized Q-factor Custom-Q 

References

  1. 1.
    Gatinel D, Haouat M, Hoang-Xuan T. A review of mathematical descriptors of corneal asphericity. J Fr Ophtalmol. 2002;25(1):81–90.PubMedGoogle Scholar
  2. 2.
    Seiler T, Koller T. Asphericity of the cornea and astigmatism. Klin Monatsbl Augenheilkd. 2005;222(12):977–82.CrossRefPubMedGoogle Scholar
  3. 3.
    Amigo A, Bonaque-Gonzalez S. Q factor Presbylasik. Fundamentals and therapeutic approach. J Emmetropia. 2012;3:167–71.Google Scholar
  4. 4.
    Gatinel D, Malet J, Hoang-Xuan T, Azar DT. Analysis of customized corneal ablations: theoretical limitations of increasing negative asphericity. Invest Ophthalmol Vis Sci. 2002;43(4):941–8.PubMedGoogle Scholar
  5. 5.
    Amigo A, Bonaque S, Lopez-Gil N, Thibos L. Simulated effect of corneal asphericity increase (Q-factor) as a refractive therapy for presbyopia. J Refract Surg. 2012;28(6):413–8.CrossRefPubMedGoogle Scholar
  6. 6.
    Calossi A. Corneal asphericity and spherical aberration. J Refract Surg. 2007;23(5):505–14.PubMedGoogle Scholar
  7. 7.
    Dorronsoro C, Remon L, Merayo-Lloves J, Marcos S. Experimental evaluation of optimized ablation patterns for laser refractive surgery. Opt Express. 2009;17(17):15292–307.CrossRefPubMedGoogle Scholar
  8. 8.
    Alio JL, Amparo F, Ortiz D, Moreno L. Corneal multifocality with excimer laser for presbyopia correction. Curr Opin Ophthalmol. 2009;20(4):264–71.CrossRefPubMedGoogle Scholar
  9. 9.
    Vargas-Fragoso V, Alio JL. Corneal compensation of presbyopia: PresbyLASIK: an updated review. Eye Vis (Lond). 2017;4:11.CrossRefGoogle Scholar
  10. 10.
    Courtin R, Saad A, Grise-Dulac A, Guilbert E, Gatinel D. Changes to corneal aberrations and vision after monovision in patients with hyperopia after using a customized aspheric ablation profile to increase corneal asphericity (Q-factor). J Refract Surg. 2016;32(11):734–41.CrossRefPubMedGoogle Scholar
  11. 11.
    Gatinel D. Presbyopia surgery. Rev Prat. 2008;58(10):1049–54.PubMedGoogle Scholar
  12. 12.
    Gatinel D, Azar DT, Dumas L, Malet J. Effect of anterior corneal surface asphericity modification on fourth-order zernike spherical aberrations. J Refract Surg. 2014;30(10):708–15.CrossRefPubMedGoogle Scholar
  13. 13.
    Reinstein DZ, Carp GI, Archer TJ, Gobbe M. LASIK for presbyopia correction in emmetropic patients using aspheric ablation profiles and a micro-monovision protocol with the Carl Zeiss Meditec MEL 80 and VisuMax. J Refract Surg. 2012;28(8):531–41.CrossRefPubMedGoogle Scholar
  14. 14.
    Reinstein DZ, Archer TJ, Gobbe M. LASIK for myopic astigmatism and presbyopia using non-linear aspheric micro-Monovision with the Carl Zeiss Meditec MEL 80 platform. J Refract Surg. 2011;27(1):23–37.CrossRefPubMedGoogle Scholar
  15. 15.
    Reinstein DZ, Archer TJ, Gobbe M. Aspheric ablation profile for presbyopic corneal treatment using the MEL80 and CRS Master Laser blended vision module. J Emmetropia. 2011;2(3):161–75.Google Scholar
  16. 16.
    Wang Yin GH, McAlinden C, Pieri E, Giulardi C, Holweck G, Hoffart L. Surgical treatment of presbyopia with central presbyopic keratomileusis: one-year results. J Cataract Refract Surg. 2016;42(10):1415–23.CrossRefPubMedGoogle Scholar
  17. 17.
    Vastardis I, Gatzioufas Z, Pajic BE, Muller J, Pajic B. Multifocal corneal excimer femtosecond laser in situ Keratomileusis following radial keratotomy: a case report with six months of follow-up. Case Rep Ophthalmol. 2014;5(3):423–8.CrossRefPubMedPubMedCentralGoogle Scholar
  18. 18.
    Koller T, Iseli HP, Hafezi F, Mrochen M, Seiler T. Q-factor customized ablation profile for the correction of myopic astigmatism. J Cataract Refract Surg. 2006;32(4):584–9.CrossRefPubMedGoogle Scholar
  19. 19.
    Stojanovic A, Wang L, Jankov MR, Nitter TA, Wang Q. Wavefront optimized versus custom-Q treatments in surface ablation for myopic astigmatism with the WaveLight ALLEGRETTO laser. J Refract Surg. 2008;24(8):779–89.PubMedGoogle Scholar
  20. 20.
    Matalia H, Francis M, Gangil T, et al. Noncontact quantification of topography of anterior corneal surface and Bowman’s layer with high-speed OCT. J Refract Surg. 2017;33(5):330–6.CrossRefPubMedGoogle Scholar
  21. 21.
    Salomao MQ, Hofling-Lima AL, Lopes BT, et al. Role of the corneal epithelium measurements in keratorefractive surgery. Curr Opin Ophthalmol. 2017;28(4):326–36.CrossRefPubMedGoogle Scholar
  22. 22.
    Gualdi LGF, Rusciano D, Ambrósio R Jr, Salomão MQ, Lopes BT, Capello V, Fintina T, Gualdi M. Ciliary muscle electrostimulation to restore accommodation (CMERA) in patients with early presbyopia: preliminary results. J Refract Surg. 2017;33(9):578.CrossRefPubMedGoogle Scholar

Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  • Fernando Faria-Correia
    • 1
    • 2
    • 3
    • 4
    • 5
    • 6
    • 7
  • Renato AmbrósioJr
    • 5
    • 8
    • 9
    • 10
    • 11
  • José Ferreira Mendes
    • 1
    • 2
    • 3
    • 4
  • Arthur B. Cummings
    • 12
  1. 1.Ophthalmology DepartmentHospital de BragaBragaPortugal
  2. 2.Life and Health Sciences Research Institute (ICVS), School of Health SciencesUniversity of MinhoBragaPortugal
  3. 3.ICVS/3B’s—PT Government Associate LaboratoryBragaPortugal
  4. 4.ICVS/3B’s—PT Government Associate LaboratoryGuimarãesPortugal
  5. 5.Rio de Janeiro Corneal Tomography and Biomechanics Study GroupRio de JaneiroBrazil
  6. 6.CUF PortoPortoPortugal
  7. 7.OftalcondePortoPortugal
  8. 8.Instituto de Olhos Renato AmbrósioRio de JaneiroBrazil
  9. 9.VisareRioRio de JaneiroBrazil
  10. 10.Department of Ophthalmology and Visual SciencesFederal University of São PauloSão PauloBrazil
  11. 11.Federal University of the State of Rio de JaneiroRio de JaneiroBrazil
  12. 12.Wellington Eye ClinicDublinIreland

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