Monochromatic Aberrations and Emmetropization Howard C. Howland* Department of Neurobiology and Behavior Cornell University, Ithaca N.Y. Jennifer Kelly Toshifumi Mihashi Topcon Corporation Tokyo *paid consultant of Topcon Corporation
Definition of Emmetropization Emmetropization is the growth or reshaping of the optical components of the eye over time so that the image surface of a distant object approaches the surface of the retina.
Outline of Talk 1.Are monochromatic aberrations a help or a hindrance in the emmetropization of sphere and cylinder? Probably neither. 2. Are high order monochromatic aberrations of the eye themselves emmetropized? Most are not. Horizontal coma may be.
Are monochromatic aberrations a help or a hindrance in the emmetropization of sphere and cylinder? 1. Evidence for emmetropization. Animals Humans 2. Possible cues for emmetropization Non Directional: Blur Directional: Chromatic aberration Ophthalmic Astigmatism Off axis astigmatism High order aberrations
The Chick as an Animal Model of Refractive Development Some time ago we showed in our laboratory that the growth of the chick eye and its refraction could be altered by lenses. We raised chicks with positive or negative lenses which were mounted on leather hoods. Schaeffel, F., A. Glasser, and H.C. Howland (1988) Accommodation, refractive error and eye growth in chickens. Vision Res. 28(5):639-657.
Results of raising chicks with negative or positive lenses Positive Lenses Negative Lenses
Studies showing emmetropization to lenses in primates Siegwart, J.T., & Norton, T.T. (1993). Refractive and ocular changes in tree shrews raised with plus or minus lenses. Invest Ophthalmol Vis Sci, 34, 1208. Smith, E.L.I., & Hung, L.-F. (1999). The role of optical defocus in regulating refractive development in infant monkeys. Vision Research, 39, 1415-1435. Whatham, A.R., & Judge, S.J. (2001). Compensatory changes in eye growth and refraction induced by daily wear of soft contact lenses in young marmosets. Vision Research, 41, 267-273.
Are monochromatic aberrations a help or a hindrance in the emmetropization of sphere and cylinder? 1.Evidence for emmetropization. Animals Humans
Orthogonal Photorefraction of 4113 Left Eyes L of 1311 Subjects in a Longitudinal Study 3 2.5 2 1.5 1.5 0 -.5-1 -1.5-2 Y =.181 -.027 * X; R^2 =.071 p < 0.0001-2.5-2.5 0 2.5 5 7.5 10 12.5 15 17.5 20 22.5 Age in years
Reduction of Left Eye Cylinder Powers As Measured by Orthogonal Photorefraction 6 5 Lcyl power [D] 4 3 2 1 0 0 2 4 6 8 10 12 14 16 18 20 Age in Years
Emmetropization of Mean Cylinders and Equivalent Spheres in Humans 0 1.0 Ln (mean L Cyl, Eq Sph) -.5-1 -1.5-2 -2.5 Ln(Mean L Sphere) Slope = 0.076 0 1 2 3 4 5 6 7 8 9 10 Age in Years Ln(Mean L Cyl) Slope = 0.239 0.27 Diopters 0.082
Summary of Emmetropization Results 1.) All vertebrates investigated, including primates, exhibit emmetropization of equivalent sphere. 2.) Humans exhibit emmetropization of sphere and cylinder,but with different rate constants.
Possible Cues for Emmetropizaton 1.) Non directional cue for defocus: Lower contrast 2.) Directional cues: Chromatic aberration Ophthalmic Astigmatism Off-axis astigmatism High order aberrations
Defocus represents a low pass filtering of the image Slide from Frank Schaeffel, Tuebingen
Possible Cues for Emmetropizaton 1.) Non directional cue for defocus: Lower contrast 2.) Directional cues: Chromatic aberration Ophthalmic Astigmatism Off-axis astigmatism High order aberrations
Orthogonal Photorefractive Attachment Attach to camera. Place next to flash gun
Gentoo Penguin Photorefracted in Air
Pointspreads from Gullstrand Eye with 5 deg. Fovea and 6 mm Pupil 9.3 mu rms 5.24 mu rms 6.9mu rms -100 mu 0.0 mu 100 mu Plane of focus
Ophthalmic Astigmatism Focusing with 1.5 Diopter Cylinder through an f/4 optical system -0.75 D 0 D +0.75 D Focus relative to target
Off-Axis Astigmatism Saggital or radial image Tangential image Diagram from M.V. Klein Optics, 1970, p 157.
Pointspreads with Pure Spherical Aberration RMS =.099 RMS = 011 RMS =.014
Summary of Possible Cues for Emmetropizaton 1.) The main cue for defocus without regard to sign is most likely contrast reduction. 2.) The possible cues for the sign of defocus (myopic or hyperopic) are: chromatic aberration, ophthalmic and off axis astigmatism and spherical aberration. 3.) Chromatic aberration and ophthalmic astigmatism have been shown to be cues for accommodative defocus; off axis astigmatism and spherical abberation have not.
Outline of Talk 1.Are monochromatic aberrations a help or a hindrance in the emmetropization of sphere and cylinder? 2. Are high order monochromatic aberrations of the cornea themselves emmetropized?
Compensation of Corneal Horizontal/Vertical Astigmatism, Lateral Coma, and Spherical Aberration by Internal Optics of the Eye Jennifer E. KellyDepartment of Neurobiology and Behavior Cornell University, Ithaca, NY, USA Toshifumi MihashiTechnical Research Institute, Topcon CorporationTokyo, Japan Howard C. HowlandDepartment of Neurobiology and Behavior Cornell University, Ithaca, NY, USA In Press, Journal of Vision
Topcon KR9000PW Wave Front Analyzer
Mean Absolute Values of Corneal and Ocular Zernike Coefficients for 6 mm pupils Mean Absolute value of Zernike Coefficient [microns] 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 Horizontal/vertical Astigmatism Lateral Coma Corneal coefficients Ocular coefficients Spherical Aberration 0 3 5* 6 7** 8* 9 10 11 12* 13 14 Corneal/Ocular Zernike Term
Reduction of Corneal Aberrations by Ocular Compensation for 6 mm Pupils RMS Mean ± SE [microns] Reduction (Corneal to Ocular) Aberration Corneal Ocular RMS [microns] % C coef p-value H/V Astigmatism (Z5) 0.634 ± 0.097 0.372 ± 0.077 0.262 41% 0.043 Lateral Coma (Z8) 0.171 ± 0.016 0.084 ± 0.011 0.087 51% 0.009 Spherical Aberration (Z12) 0.207 ± 0.012 0.132 ± 0.017 0.075 36% 0.004
Plots of Internal vs. Corneal Coefficients 5 3 1-1 -3-5 i f f e y = -2x o c y = - x e k i n r e Z l a n r e t n I Augmentation Augmentation Undercompensation Overcompensation -5-4 -3-2 -1 0 1 2 3 4 5 Corneal Zernike coefficient [microns]
Compensation for Horizontal/Vertical Astigmatism 1.4 1.2 1.8.6.4.2 0 m s i t a m g i t s A -.2-2.5-2 -1.5-1 -.5 0.5 1 1.5 5 Z ( y = -x r = -.524 Corneal H/V Astigmatism (Z5) [microns]
Compensation for Lateral Coma.1 0 -.1 -.2 l a r e t a L y = -x r = -0.381 -.3 -.4 l a n r e t Corneal n Lateral Coma (Z8) [microns] -.5 -.1 0.1.2.3.4.5
Compensation for Spherical Aberration.2.15.1.05 0 -.05 -.1 -.15 -.2 -.25 -.3 -.35 y = -x l a c i r e h p S r = -0.289 l a n r Corneal e Spherical (Z12) [microns] 0.05.1.15.2.25.3.35.4
Coma vs. Purkinje Image Eccentricity ) 8 Z ( a m o c l a r e t a L 1.8.6.4.2 0 -.2 -.4 Corneal; y = 0.073 + 0.309*x; R^2 = 0.148 Ocular; y = 0.21-0.065*x; R^2 =.005 Internal; y = -0.052-0.374*x; R^2 = 0.179 -.6 0.1.2.3.4.5.6 Lateral distance Purkinje image to pupil center [mm]
Lateral Coma as a function of Foveal Eccentricity in two Model Eyes Lateral coma [microns] 1 0-1 -2 Ocular Corneal Internal -5 0 5 10 15 (a) Navarro et al. 1 0-1 -2 Object field angle [degrees] -5 0 5 10 15 (b) Liou & Brennan
Summary of Compensation and Emmetropization of High Order Aberrations 1. Horizontal/Vertical Astigmatism (not a HOA) is compensated and emmetropized. 2. Spherical aberration is compensated but most probably not emmetropized. 3. Lateral coma is compensated and may or may not be emmetropized. 4. None of the other high order aberrations are compensated or emmetropized.
Thank you for your attention!
1.5 1.5 0 -.5-1 -1.5 Lateral Coma as a function of Pupil Shift in two Model Eyes Coma Augmented [ a m o c l a r e -2 -.4 -.2 0.2.4.6.8 1 1.2 t a L Corneal Ocular Internal (a) Navarro et al. 1.5.5 -.5-1 -1.5 Lateral pupil shift [mm] Coma Overcompensated 1 0-2 -.4 -.2 0.2.4.6.8 1 1.2 (b) Liou and Brennan