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Diurnal Fluctuations of Ocular Dimensions and Aberrations: Implication for Eye Growth Regulation

Diurnal Fluctuations of Ocular Dimensions and Aberrations: Implication for Eye Growth Regulation. Yibin Tian & Christine F Wildsoet School of Optometry University of California at Berkeley. The eye is not static. Recent findings:

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Diurnal Fluctuations of Ocular Dimensions and Aberrations: Implication for Eye Growth Regulation

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  1. Diurnal Fluctuations of Ocular Dimensions and Aberrations: Implication for Eye Growth Regulation Yibin Tian & Christine F Wildsoet School of Optometry University of California at Berkeley

  2. The eye is not static Recent findings: Aberrational changes on the scale of seconds, days, weeks and months in humans (Cheng et al, 2004; Hofer et al, 2001). Diurnal axial length and choroid thickness changes in chicks, rabbits, and monkeys (Nickla et al, 1998; Nickla et al, 2002). Diurnal dimensional change in human eyes (Stone et al, 2004).

  3. Why aberrations? • Image quality is important for normal eye growth (Animal studies, Wallman et al, 2005; Wildsoet, 1997). Ocular aberrations degrade retinal image, and myopes have more aberrations (Marcos et al, 2001; Collins et al, 1995). So, aberrations MIGHT play some role in eye growth. 2. Understanding ocular aberrations can improve optical and surgical corrections for myopia.

  4. Questions How do aberrations change with age in growing eyes? Are there diurnal patterns in aberration change? If there is, then are there connections between diurnal ocular dimensional changes and aberration changes?

  5. Methods • Subjects: 8 Ciliary nerve sectioned (CNX) and 8 normal chicks raised in constant temperature, 12/12 light cycle. • The lengths of anterior chamber, crystalline lens and vitreous chamber, retina and choroid were measured with A-scan ultrasonography 4 times a day (9AM, 12PM, 3PM & 7:00PM) on days 11, 14, 18, 21, 32. • The aberrations of the same eyes were measured the next day (days 12, 15, 19, 22, 33) with aberrometer around the same time points.

  6. Methods (CNX) In chicks CNX cuts off innervation to both lenticular and corneal accommodation (Glasser et al, 1995).

  7. Methods: aberration representation

  8. Methods: aberration representation Spherical equivalent refractive error (SERE) and astigmatism can be derived from Zernike coefficients. Equivalent defocus power for higher order aberrations (Thibos et al, 2001) Analyses were done on 2mm pupil diameter.

  9. Spherical equivalent refractive error CNX vs. Norm (Red vs. Blue) 1.356D; p=0.0009. Age(Norm) Not significant Diurnal(Norm) 0.755D; p<0.0001.

  10. Astigmatism CNX vs. Norm (Red vs. Blue) Not Significant. Age(Norm) -1.077D; P<0.0001. Diurnal(Norm) Not Significant.

  11. CNX vs. Norm (Red vs. Blue) 0.21D; p=0.0402. Age(Norm) 0.33D; P=0.005. Diurnal(Norm) 0.09D; P=0.064. Spherical Aberration

  12. Higher order aberrations CNX vs. Norm (Red vs. Blue) Not significant. Age(Norm) -1.337D; P<0.0001. Diurnal(Norm) -0.319D; P=0.019.

  13. Vitreous chamber depth CNX vs. Norm (Red vs. Blue) 0.028mm; p=0.0133. Age(Norm) 0.044mm; p <0.0001. Diurnal(Norm) 0.019mm; p<0.0033.

  14. Choroid thickness CNX vs. Norm (Red vs. Blue) 0.028mm; p=0.0133. Age(Norm) 0.044mm; p <0.0001. Diurnal(Norm) -0.019mm; p<0.0033.

  15. Summary of results • Astigmatism and HOA significantly decreased from day 12 to day 33 on the same pupil size; decrease in SERE was not significant; spherical aberration remained positive in CNS eyes, while shifted from negative to positive in normal eyes; • ACD, LT and VCD significantly increased with age; • SERE was significantly more hyperopic in the evening than in the morning; there were also significant diurnal variations in HOA; • Significant diurnal changes in ACD, LT,VCD and OAL, all of which were longer in the evening than in the morning; while CT was shorter in the evening.

  16. What’s going on? • Refraction is about 0.8D more hyperopic in the evening, while VCD and OAL are both longer??? Elongation of ACD can’t account for it. 0.01mm increase in ACD only contributes about 0.04D (Let Pcornea = 100D; Plens = 50D); 0.05mm increase in VCD can lead to refraction change of –0.9D; Flattening of lens and/or cornea??? 0.05mm RC cornea flattening contributes 1.4D.

  17. Aberration Emmetropization

  18. I B1(t) B0 B2(t) S0 S B0 B3(t) L(I) B0 T1 T2 Possible role of diurnal fluctuation Microfluctuations can provide accommodation cues (Kotulak et al, 1986) It has been shown that DoF of young chick eyes are smaller than 1D (Schimid et al, 1997) Time

  19. Acknowledgements • NEI grant NEI R01 EY12392-06 (to CFW) • Thanks to Wildsoet lab members, especially Kandy Guan for taking ultrasonogarphy readings in pilot study. Thank you!

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