May 2005
Volume 46, Issue 13
ARVO Annual Meeting Abstract  |   May 2005
Retinoic Acid Induces Extremely Rapid Eye Elongation
Author Affiliations & Notes
  • C. Sheng
    Biology, The City College of New York, New York, NY
  • J. Wallman
    Biology, The City College of New York, New York, NY
  • Footnotes
    Commercial Relationships  C. Sheng, None; J. Wallman, None.
  • Footnotes
    Support  NIH Grant EY002727–25
Investigative Ophthalmology & Visual Science May 2005, Vol.46, 3340. doi:
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      C. Sheng, J. Wallman; Retinoic Acid Induces Extremely Rapid Eye Elongation . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3340.

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

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Abstract: : Purpose: It has been shown that positive and negative lenses have opposite effects on eye growth. Retinoic acid (RA) may be a sign–dependent mediator in regulating ocular elongation: The rate of synthesis of RA in both retina and choroid changes in opposite directions during the wearing of positive and negative lenses in chicks (Mertz & Wallman, 2000; Richiert et al., ARVO 2004). Feeding young chicks or guinea pigs with all–trans retinoic acid (RA) resulted in a rapid increase in eye–size (McFadden et al., 2003; Howlett PhD Dissertation, 2003). This study examines the time–course of the effect of RA on ocular elongation during the first 5 hours after feeding. Methods: One–week old chicks were fed with either 24 mg/Kg all–trans RA or vehicle (peanut oil, PO) at noon. Eyes were measured by A–scan ultrasonography before feeding RA and hourly thereafter. Results: Three out of four chicks fed RA showed the rapid ocular expansion previously described. In these birds the eyes grew many times more rapidly over the 5–hour period after feeding than in those fed PO (13 µm/hour vs. 0.4 µm/hour; unpaired 1–tailed student t–test, p<0.005). Even by the second hour the eyes of chicks fed RA had elongated significantly more than the control birds (42 µm vs. 0 µm, p<0.005), as well as at the 4th (mean of growth, RA vs. PO: 60 µm vs. 0 µm, p<0.01) and the 5th hour (mean of growth, RA vs. PO: 67 µm vs. 0 µm, p<0.01). The rate of elongation over the first 2 hr was 7 times the normal daily rate of 70 µm/day. Moreover, in normal birds, the rate of ocular elongation at this time of day is near zero (Nickla et al., 1998), as it was in the birds fed PO in this experiment. Conclusions: Although most actions of retinoic acid are mediated at the transcriptional level, the extreme rapidity of ocular expansion after feeding retinoic acid to chicks, suggests that mechanisms other than transcriptional modulation of synthetic pathways may be at work.

Keywords: myopia • emmetropization 

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