PhD, Biology, City College of The City University of New York
Animal models have shown that the growth of the eye is regulated by visual experience, however, the cellular and molecular pathways that mediate this “emmetropization” are as yet unknown. The changes that occur in the sclera and choroid in the posterior part of the eye are responsible for the ocular growth that can lead to myopia.
One of the focuses of Dr. Nickla’s research is to investigate the effects of specific drugs on both the choroidal and scleral responses to defocus in an effort to address the question of why some people become myopic while others do not. Dr. Nickla’s latest research shows evidence that muscarinic antagonists such as atropine and pirenzepine have effects on the choroid that, in turn, act on the sclera to mediate ocular growth changes in chickens. Specifically, these drugs produce a transient thickening of the choroid, which is associated with ocular growth inhibition. Muscarinic agonists, on the other hand, produce the opposite changes: choroidal thinning and growth stimulation. She has been studying these effects both in vivo and in eyecup preparations. She believes that acetylcholine might play a role in the changes in choroidal thickness by affecting the tonus of the non-vascular smooth muscles in the stromal layer of the choroid, which in turn may mediate changes in eye growth.
Another molecule of interest in eye growth regulation is the gaseous neurotransmitter nitric oxide. Dr. Nickla has studied the effects of the nitric oxide synthase inhibitor L-NAME and found that this inhibits the transient choroidal thickening normally seen in response to myopic defocus. This in turn disinhibits ocular growth, linking the two responses, and supporting nitric oxide as a candidate molecule in eye growth regulation.
Xiao Ying Zhu (City College of The City University of New York)
Falk Schroedl (Paracelsus University, Austria)