Transcript Slide 1
Measurement of Higher Order Aberrations in Contact Lenses James J. Butler Pacific University Physics Department Forest Grove, OR Matt Lampa Pacific University College of Optometry Forest Grove, OR Pacific University Physics Department Pacific University Physics • Small, liberal arts college setting ~ 1500 undergraduates • Innovative teaching • All physics majors have senior capstone research experience • Faculty connected with College of Optometry Physics Department Optics Tools • Nd:YAG pumped OPO laser system • Continuously tunable from 420 nm to 2500 nm • 4 ns pulses @ 10 Hz repetition rate • Shack-Hartmann wavefront sensor • Zernike representations of tilt, defocus, astigmatism, coma, spherical, and higher order aberrations • 39 x 31 element lenslet array provides λ/50 wavefront sensitivity over a 6 mm x 5 mm aperture Optics Research in the Physics Department • Optical Limiting – collaboration with Naval Research Laboratory – eye and sensor protection – scope sights, binoculars, and fiber optic systems – must operate at visible and infrared wavelengths Lens • “nonlinear absorbers” - increase absorption as irradiance of incident light increases Capillary fiber Incident Light • capillary fiber makes high irradiance beam interact with nonlinear absorber for large distance Nonlinear Core Optical Limiting Experimental Setup P.C. Running LabVIEW Energy Detector Frequency Doubled Nd:YAG Laser or Nd:YAG pumped OPO Energy Ratiometer Sample Holder Fiber Cladding 8% Pick Off Energy Detector or CCD camera Objective Core Objective Nonlinear Transmission at 1050 nm Relative Transmission Energy out of core (nJ) 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0.0 90 80 70 60 50 40 30 20 10 0 0.1 1.0 10.0 100.0 1000.0 Energy coupled into core (nJ) 1 nJ into core 0 100 200 Energy coupled into core (nJ) 300 nJ into core 300 Contact Lens Aberrations A new collaboration between Dr. Butler and Dr. Lampa Initial Funding: Pacific Research Institute for Science and Mathematics Collaborator: Shannon Soper – physics major, Pacific University Wavefront Aberrations Ideal Image Formation Spherical wavefronts Real image point Real object point Real Image Formation exit pupil of optical system Ideal (paraxial) image plane ideal wavefront ideal image point aberrated wavefront Wavefront aberrations quantified using Zernike polynomials http://wyant.optics.arizona.edu/ zernikes/zernikes.htm Wavefront Aberrations Notes • Piston, tilt, and power (defocus) are ignored in discussions of aberrations • 2nd order Zernike polynomials – astigmatism • 3rd order Zernike polynomials – coma & trefoil • 4th order Zernike polynomials – spherical, secondary astigmatism, & tetrafoil astigmatism coma spherical Contact Lens Aberrations • Liang et al. (1994) measured aberrations of 2 uncorrected eyes Eye type 2nd order (μm) 3rd order (μm) 4th order (μm) -1.5 D myope 1 0.5 0.3 emmetrope 0.8 0.8 0.2 • Dietze et al. (2003) measured spherical aberration (4th order Zernike) of 17 eyes Eye type Uncorrected (μm) myope (up to -8.5 D) -0.1 to +0.4 emmetrope -0.1 to +0.2 hyperope (up to +4.5 D) -0.05 to +0.6 • SA of off-eye soft contact lenses theoretically calculated and ranged from about -0.2 to +0.1 μm (approximately linear with lens power) • Change in SA of eyes wearing soft contact lenses approximately equal to calculated SA of off-eye soft contact lenses (although theory was consistently below measured) More Contact Lens Aberrations • Lu et al. (2003) measured Zernike aberrations up to 5th order for 54 myopic eyes (-2 to -8 D) Average RMS aberrations 2nd order (μm) 3rd order (μm) 4th order (μm) 5th order (μm) uncorrected 0.75 0.35 0.2 0.3 Soft contact lens corrected 0.8 0.4 0.25 0.4 Hard contact lens corrected 0.5 0.3 0.2 0.3 • Numbers in red significantly different than uncorrected • Eye conforms to hard lens shape leading to reduction in 2nd order (astigmatism) • Increase in high order aberrations for soft contact lens correction not explained • Off-eye aberrations of lenses not measured • Jeong et al. (2005) and Kollbaum et al. (2008) measured aberrations of off-eye contact lenses in a wet cell but did not compare to on-eye lenses • Bakaraju et al. (2010) developed sophisticated bench-top model eye that could be used to compare on-eye and off-eye contact lens aberrations but no reports have been made yet. Proposed Work • Develop physical model eye that closely matches optical characteristics of actual eye - Use gelatin with appropriate water content to obtain n ~ 1.37 (Dr. Dan Boye, Physics Department, Davidson College) - Gelatin promises to allow the fabrication of model eye with appropriate refractive index and any desired optical properties (e.g. astigmatism, keratoconus, etc.) • Carefully measure and characterize aberrations of physical model eyes • Measure and characterize aberrations of various contact lenses (single vision and multifocal) off-eye using a wet cell. • Measure aberrations of physical model eyes with contact lenses in place • Determine a relationship between off-eye and on-eye aberrations of contact lenses and characteristics of model eye References • J. Liang, B. Grimm, S. Goelz, and J.F. Bille, “Objective measurement of wave aberrations of the human eye with the use of a Hartmann-Shack wave-front sensor,” Journal of the Optical Society of America A, Vol. 11, pp. 1949-1957 (1994). • H.H. Dietze and M.J. Cox, “On- and off-eye spherical aberration of soft contact lenses and consequent changes in effective lens power,” Optometry and Vision Science, Vol. 80, pp. 126-134 (2003). • F. Lu, X. Mao, J. Qu, D. Xu, and J.C. He, “Monochromatic wavefront aberrations in the human eye with contact lenses,” Optometry and Vision Science, Vol. 80, pp. 135-141(2003). • T.M. Jeong, M. Menon, and G. Yoon, “Measurement of wave-front aberration in soft contact lenses by use of a Shack-Hartmann wave-front sensor,” Applied Optics, Vol. 44, pp. 4523-4527 (2005). • P. Kollbaum, M. Jansen, L. Thibos, and A. Bradley, “Validation of an off-eye contact lens ShackHartmann wavefront aberrometer,” Optometry and Vision Science, Vol. 85, pp. E817-E828 (2008). • R.C. Bakaraju, K. Ehrmann, D. Falk, A. Ho, and E. Papas, “Physical human model eye and methods of its use to analyse optical performance of soft contact lenses,” Optics Express, Vol. 18, pp. 16868-16882 (2010).