May 2008
Volume 49, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2008
Eye Shape and Off-Axis Refractive State Following Induced Axial Refractive Errors in Marmoset Monkeys
Author Affiliations & Notes
  • K. Totonelly
    The New England College of Optometry, Boston, Massachusetts
  • D. Troilo
    The New England College of Optometry, Boston, Massachusetts
  • Footnotes
    Commercial Relationships  K. Totonelly, None; D. Troilo, None.
  • Footnotes
    Support  NIH EY011228
Investigative Ophthalmology & Visual Science May 2008, Vol.49, 3589. doi:https://doi.org/
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    • Get Citation

      K. Totonelly, D. Troilo; Eye Shape and Off-Axis Refractive State Following Induced Axial Refractive Errors in Marmoset Monkeys. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3589. doi: https://doi.org/.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: : Eye shape and off-axis refractive state differ between emmetropes and myopes suggesting that they may be factors in the development of on-axis refractive state. We examined the development of eye shape and off-axis refractive state in our primate model of eye growth to determine whether changes occur after axial refractive errors are induced.

Methods: : Marmosets wore soft contact lenses to impose hyperopic or myopic defocus and produce changes in axial length and refractive state. Treatment groups include monocular and binocular conditions (R/L): -/plano, +/plano, -/+. Untreated marmosets were used as controls. Following treatment, cycloplegic refractive state was measured on- and off-axis and MRI was performed to analyze eye shape and vitreous chamber (VC) depth on a central horizontal plane.

Results: : Using a simple measure (equatorial diameter/axial VC depth) we found that eye shape is significantly correlated with the powers of the lenses used (r=0.60), the degree of axial refractive error induced (r=0.47), and the depth of the VC on-axis (r=0.44). Negative lenses induced eyes to grow significantly longer and more myopic on-axis, and become less oblate (wider-than-long) or, in some cases, prolate (longer-than-wide). Eyes that wore positive lenses were significantly shorter, more hyperopic on-axis, and more oblate. Marmoset eyes exhibit a nasal-temporal asymmetry in shape: the VC depth 20-40 deg nasal to the optic axis is significantly shallower than along the central 20 deg or from 20-40 deg temporal to the optic axis, which were not significantly different from each other. The nasal VC depth in negative-lens-treated eyes was significantly shallower than in positive-lens-treated eyes and corresponds to differences in off-axis refractive state in the two groups. Relative to the on-axis refractions, off-axis refractive state measured along the nasal retina in the negative-lens-treated eyes was significantly more hyperopic than in positive-lens treated or control eyes. The relative off-axis refractive state measured along the temporal retina did not differ between the experimental groups and controls.

Conclusions: : Lens-induced axial myopia is associated with a change in overall eye shape and an increase in nasal-temporal asymmetry that corresponds to an increase in off-axis hyperopia on the nasal retina. While these changes are consequences of the response to lens rearing, the altered shape and off-axis refractive state in myopic eyes may increase their risk for developing more axial myopia.

Keywords: myopia • refractive error development 
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