Abstract
Purpose:
Arginine-Vasopressin (AVP) is a naturally occurring anti-diuretic hormone that acts to control osmolarity and body fluid volume. AVP has been localized to the inner retina, reduces IOP and is associated with retinal AQP-4 expression (ARVO 2009). Thus we aimed to determine whether AVP’s anti-diuretic action would affect refraction and ocular growth compensation to optical defocus especially in the presence of asymmetric flicker, a physiologically stressful stimulus of environmental origin.
Methods:
Chicks were raised from days 5-9 post-hatching in one of 3 lens (+, -10D or No Lens) and in one of 3 light conditions (a Normal Diurnal 12 hr day/night cycle or either Fast ON/Slow OFF or Fast OFF/Slow ON sawtooth flicker generated by a light emitting diode array at 1 Hz) following a single intravitreal injection of 5μl of either PBS alone or as the carrier solution for Vasopressin (1.84 x 10-4 mM) or the dual V1/V2 Vasopressin receptor antagonist ([des-Gly9-β-Mercapto-β, β-cyclopentamethylenepropionyl1, O-Et-Tyr2, Val4, Arg8]-Vasopressin) (5.53 x 10-4 mM). Retinoscopy and A-scan ultrasonography was performed on Day 9.
Results:
AVP-injected, -10D lens-wearing eyes all showed a myopic shift as expected of an anti-diuretic agent in all light conditions, as did the +10D eyes reared under Fast ON flicker. In comparison, the AVP antagonist prevented the myopic shift typically induced by flicker conditions in the +10D lensed eyes. Changes in refraction were closely mirrored by changes in posterior eye growth. Significant interaction effects between drug, light and lens conditions were observed for refractive state, axial length and vitreous chamber depth, while more variable growth patterns were observed for anterior chamber depth.
Conclusions:
The finding that the natural anti-diuretic hormone, AVP, but not its antagonist, increased myopia and axial elongation in the presence of negative defocus highlights the importance of the interaction between modulation of fluid dynamics and responses to light-induced environmental stress in ocular growth and refractive compensation.
Keywords: 688 retina •
605 myopia •
726 stress response