Abstract
Purpose: :
Muscaranic antagonists such as atropine are the most potent anti-myopia drugs available. Atropine also blocks experimental myopia in several species and thickens choroids in chicks. To explore whether choroidal thickness is linked to changes in ocular elongation, we measured the effect of agonists on both. To see whether the effects on choroidal thickness were local to the choroid, we treated choroids in vitro.
Methods: :
In vivo
Results: :
In vivo
Conclusions: :
Activation of muscarinic receptors thins the choroid and may partly compensate for hyperopic defocus. We speculate that acetylcholine increases the tonus of the non-vascular smooth muscle spanning the choroidal stroma, thus opposing the osmotic forces that expand the fluid-filled lacunae. Oxotremorine's biphasic choroidal thickening and then thinning linked to inhibition and then stimulation of ocular elongation is further evidence of the choroid modulating eye growth.
Keywords: choroid • emmetropization • acetylcholine