<prompt> A powerful cycloplegia is:AtropineTropicomidePhenylephrineHomatropine  <response>: Atorpine 147-Parson 20th Atorpine - is the most potent and has longest duration of action for 7 days or more Homatropine - are less potent. It affects lasts for 4-5 days Tropicamide - short acting, though effective for upto 3 hours. Phenylephrine - a selective alpha - 1 - agonist, sympathomimetics. 