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Regan Ashby, Cindy Karouta; Egr-1 mRNA Expression in Response to Myopic Defocus. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5640.
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The expression of the transcription factor Egr-1 appears to act as a biomarker of ocular growth, showing, for the most part, a bi-directional response to opposing growth stimuli. However, in response to lens-induced hyperopia (LIH), Egr-1 mRNA levels do not follow the expected up-regulation normally associated with growth suppression, but rather are down-regulated similar to that seen during periods of enhanced growth. This study investigated if this unexpected directional change in Egr-1 expression may be associated with the growth state of the eye prior to lens-wear. Specifically, Egr-1 expression is up-regulated in response to myopic defocus associated with the removal of translucent diffusers or negative lenses from already myopic eyes. In both of these paradigms, the eye is in a state of increased growth before the optical device is removed. In contrast, in LIH, myopic defocus is applied to an eye that was previously in a state of normal growth.
Egr-1 mRNA levels were measured in the chick retina using RT-PCR after 4 and 24 hrs in response to the following conditions: 1) Fitment of +5D or +10D lenses to otherwise normal eyes (n=7); 2) Fitment of +5D lenses following compensation to -10D lenses (n=7); 3) Fitment of +10D lenses after compensation to -5D lenses (n=7); 4) Fitment of +5D lenses after partial compensation to -10D lenses (i.e. the eye is still in a state of excessive growth; n=7); 5) Fitment of +5D lenses following four days of diffuser-wear (i.e. again, the eye is in a state of excessive growth; n=7).
Egr-1 mRNA expression was significantly down-regulated in the retina following 4 and 24hrs of plus lens-wear irrespective of the previous state of eye growth (one-way ANOVA, treated (five conditions x two time points) vs untreated control values; F(10, 84) = 1816.8, p<0.0001).
Egr-1 mRNA levels are normally up-regulated in response to myopic defocus associated with the removal of translucent diffusers or negative lenses. In contrast, plus lens-wear, which also induces myopic defocus, induces a down-regulation in Egr-1 levels. This down-regulation occurs irrespective of whether the eye was in a normal or excessive state of growth prior to plus lens-wear. Together, these results suggest that myopic defocus induced by plus lens-wear is somehow processed differently at the level of the retina to that seen following diffuser or negative-lens removal.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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