title: Comparing the optical properties of soft contact lenses on and off the eye.
abstract: OBJECTIVE
  The purpose of the current study was to examine the on- and off-eye optical performance of two types of soft contact lenses (hydrogel and silicone hydrogel).
  
  
  METHODS
  The monochromatic aberrations (λ = 850 nm) of contact lenses were measured on-eye using a clinical Shack-Hartmann ocular aberrometer. In addition, we used an off-eye single-pass contact lens aberrometer (λ = 540 nm) in which the soft contact lens was placed within a wet cell. Comparison of the lower and higher order aberrations measured with these two methods required compensation for different wavelengths and knowledge of the refractive index of the contact lens materials.
  
  
  RESULTS
  The measured on-eye sphere and spherical aberration values were generally similar to those measured off-eye and those specified by the lens manufacturers for both types of soft contact lenses. However, there were notable differences, especially for high plus-powered lenses, which typically exhibited lower sphere power on the eye than expected from the lens specifications and from the off-eye measured powers, both of which were almost identical. Longitudinal spherical aberration varied with lens power in the hydrogel lenses, as expected from geometric optics theory. Longitudinal spherical aberration measurements on- and off-eye, however, deviated significantly from that expected of a thin lens with spherical surfaces due to surface asphericities. The difference between on- and off-eye optics can be modeled as a tear lens or as relative lens thickness changes caused by lens flexure.
  
  
  CONCLUSIONS
  The results of the current study reveal that the major difference between the on-eye lens optics and the manufacturers' specifications is not due to lens errors but due to eye-lens interactions, which could be either lens flexure or a tear lens forming behind the soft contact lens.
authors: School of Optometry, Indiana University, Bloomington, IN, USA. kollbaum@indiana.edu
authors: Pete S
authors: PS
authors: Kollbaum
authors: Arthur
authors: A
authors: Bradley
authors: Larry N
authors: LN
authors: Thibos
mesh_terms: D057128:Aberrometry; D003263:Contact Lenses, Hydrophilic; D003315:Cornea / Q000502:physiology*; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D009184:Mydriatics / Q000008:administration & dosage; D055095:Optics and Photonics; D011680:Pupil / Q000187:drug effects; D012029:Refraction, Ocular / Q000502:physiology*; D012031:Refractometry
chemical_list: D009184:Mydriatics; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate
references: Appl Opt. 2005 Jul 20;44(21):4523-7
references: 16047902
references: Cont Lens Anterior Eye. 2008 Aug;31(4):189-93
references: 18602857
references: Am J Optom Physiol Opt. 1975 Jul;52(7):470-3
references: 1180322
references: Optom Vis Sci. 1998 Jan;75(1):44-54
references: 9460786
references: Am J Optom Physiol Opt. 1984 Jul;61(7):465-8
references: 6465278
references: Optom Vis Sci. 1997 Jul;74(7):548-56
references: 9293524
references: Am J Optom Physiol Opt. 1980 Oct;57(10):697-710
references: 7446678
references: Int Ophthalmol Clin. 1981;21(2):105-12
references: 7239806
references: Clin Exp Optom. 2009 May;92(3):283-8
references: 19351378
references: J Vis. 2004 Apr 23;4(4):329-51
references: 15134480
references: Ophthalmic Physiol Opt. 2009 Nov;29(6):593-601
references: 19663925
references: Optom Vis Sci. 1997 Jun;74(6):367-75
references: 9255814
references: Ophthalmic Physiol Opt. 2003 Nov;23(6):517-25
references: 14622355
references: Invest Ophthalmol Vis Sci. 2003 Jan;44(1):68-77
references: 12506057
references: J Am Optom Assoc. 1978 Apr;49(4):437-41
references: 649925
references: Lancet. 1986 Feb 8;1(8476):307-10
references: 2868172
references: Invest Ophthalmol Vis Sci. 2004 Jan;45(1):351-60
references: 14691194
references: Optom Vis Sci. 2008 Sep;85(9):E817-28
references: 18772713
references: J Opt Soc Am A Opt Image Sci Vis. 2008 Oct;25(10):2395-407
references: 18830317
references: Am J Optom Physiol Opt. 1979 Dec;56(12):727-33
references: 551732
references: Ophthalmic Physiol Opt. 1988;8(3):253-6
references: 3269505
references: Appl Opt. 1980 Jul 1;19(13):2226-34
references: 20221212
references: Graefes Arch Clin Exp Ophthalmol. 2011 Apr;249(4):607-12
references: 20694473
references: J Opt Soc Am A Opt Image Sci Vis. 2001 May;18(5):1003-15
references: 11336203
references: Ophthalmic Physiol Opt. 1987;7(4):485-90
references: 3454926
references: Invest Ophthalmol Vis Sci. 2003 Jun;44(6):2524-8
references: 12766052
references: Optom Vis Sci. 2003 Aug;80(8):587-95
references: 12917578
references: Am J Optom Physiol Opt. 1979 Oct;56(10):613-7
references: 525664
references: Am J Optom Physiol Opt. 1980 Oct;57(10):711-3
references: 7446679
references: Optom Vis Sci. 2003 Feb;80(2):126-34
references: 12597327
references: Am J Optom Physiol Opt. 1981 Jan;58(1):2-5
references: 7212012
references: Am J Optom Physiol Opt. 1981 Feb;58(2):139-43
references: 7223840
references: CLAO J. 1983 Jan-Mar;9(1):32-8
references: 6839432
references: Optom Vis Sci. 2009 Jul;86(7):900-3
references: 19525882
references: Am J Optom Physiol Opt. 1984 Apr;61(4):239-45
references: 6547274
references: Invest Ophthalmol Vis Sci. 1999 Nov;40(12):2833-9
references: 10549643