Monochromatic Aberrations and Emmetropization

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2 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

3 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.

4 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.

5 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

$The Chick as an Animal Model of Refractive Development Some time ago we showed in our laboratory that the growth of the chick eye and its refraction could be altered by lenses.$

6 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):

7 Results of raising chicks with negative or positive lenses Positive Lenses Negative Lenses

8 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, Smith, E.L.I., & Hung, L.-F. (1999). The role of optical defocus in regulating refractive development in infant monkeys. Vision Research, 39, 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,

9 Are monochromatic aberrations a help or a hindrance in the emmetropization of sphere and cylinder? 1.Evidence for emmetropization. Animals Humans

10 Orthogonal Photorefraction of 4113 Left Eyes L of 1311 Subjects in a Longitudinal Study Y = * X; R^2 =.071 p < Age in years

11 Reduction of Left Eye Cylinder Powers As Measured by Orthogonal Photorefraction 6 5 Lcyl power [D] Age in Years

12 Emmetropization of Mean Cylinders and Equivalent Spheres in Humans Ln (mean L Cyl, Eq Sph) Ln(Mean L Sphere) Slope = Age in Years Ln(Mean L Cyl) Slope = Diopters 0.082

13 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.

14 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

15 Defocus represents a low pass filtering of the image Slide from Frank Schaeffel, Tuebingen

16 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

17 Orthogonal Photorefractive Attachment Attach to camera. Place next to flash gun

18 Gentoo Penguin Photorefracted in Air

19 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

20 Ophthalmic Astigmatism Focusing with 1.5 Diopter Cylinder through an f/4 optical system D 0 D D Focus relative to target

21 Off-Axis Astigmatism Saggital or radial image Tangential image Diagram from M.V. Klein Optics, 1970, p 157.

22 Pointspreads with Pure Spherical Aberration RMS =.099 RMS = 011 RMS =.014

23 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.

24 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?

25 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

26 Topcon KR9000PW Wave Front Analyzer

27 Mean Absolute Values of Corneal and Ocular Zernike Coefficients for 6 mm pupils Mean Absolute value of Zernike Coefficient [microns] Horizontal/vertical Astigmatism Lateral Coma Corneal coefficients Ocular coefficients Spherical Aberration 0 3 5* 6 7** 8* * Corneal/Ocular Zernike Term

28 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) ± ± % Lateral Coma (Z8) ± ± % Spherical Aberration (Z12) ± ± % 0.004

29 Plots of Internal vs. Corneal Coefficients 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 Corneal Zernike coefficient [microns]

30 Compensation for Horizontal/Vertical Astigmatism m s i t a m g i t s A Z ( y = -x r = Corneal H/V Astigmatism (Z5) [microns]

31 Compensation for Lateral Coma l a r e t a L y = -x r = l a n r e t Corneal n Lateral Coma (Z8) [microns]

32 Compensation for Spherical Aberration y = -x l a c i r e h p S r = l a n r Corneal e Spherical (Z12) [microns]

33 Coma vs. Purkinje Image Eccentricity ) 8 Z ( a m o c l a r e t a L Corneal; y = *x; R^2 = Ocular; y = *x; R^2 =.005 Internal; y = *x; R^2 = Lateral distance Purkinje image to pupil center [mm]

34 Lateral Coma as a function of Foveal Eccentricity in two Model Eyes Lateral coma [microns] Ocular Corneal Internal (a) Navarro et al Object field angle [degrees] (b) Liou & Brennan

35 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.

36 Thank you for your attention!

38 Lateral Coma as a function of Pupil Shift in two Model Eyes Coma Augmented [ a m o c l a r e t a L Corneal Ocular Internal (a) Navarro et al Lateral pupil shift [mm] Coma Overcompensated (b) Liou and Brennan

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