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

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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

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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).
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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.
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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?
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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 700PM) 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.

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Methods (CNX)
In chicks CNX cuts off innervation to both
lenticular and corneal accommodation (Glasser et
al, 1995).
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Methods aberration representation
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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.
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Spherical equivalent refractive error
CNX vs. Norm (Red vs. Blue) 1.356D
p0.0009. Age(Norm) Not significant Diurnal(Norm)
0.755D plt0.0001.
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Astigmatism
CNX vs. Norm (Red vs. Blue) Not
Significant. Age(Norm) -1.077D Plt0.0001. Diurnal(
Norm) Not Significant.
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Spherical Aberration
CNX vs. Norm (Red vs. Blue) 0.21D p0.0402.
Age(Norm) 0.33D P0.005. Diurnal(Norm) 0.09D P0
.064.
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Higher order aberrations
CNX vs. Norm (Red vs. Blue) Not
significant. Age(Norm) -1.337D Plt0.0001. Diurnal(
Norm) -0.319D P0.019.
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Vitreous chamber depth
CNX vs. Norm (Red vs. Blue) 0.028mm
p0.0133. Age(Norm) 0.044mm p lt0.0001.
Diurnal(Norm) 0.019mm plt0.0033.
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Choroid thickness
CNX vs. Norm (Red vs. Blue) 0.028mm
p0.0133. Age(Norm) 0.044mm p lt0.0001.
Diurnal(Norm) -0.019mm plt0.0033.
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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.

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Whats going on?

• Refraction is about 0.8D more hyperopic in the
  evening, while VCD and OAL are both longer???
• Elongation of ACD cant 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.

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Aberration Emmetropization
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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
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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!