<prompt> The most common organism causing chorioretinitis in HIV isCMV retinitisToxoplasma chorioretinitisSyphilitic retinitisPneumocystis carini  <response>: Refer: AK Khurana Comprehensive Ophthalmology, 6th edition, pg no. 470 - 472Cytomegalovirus CMV is the most common cause of chorioretinitis in patients who are HIV positive 