Which of the following is the commonest infection causing blindness in adult man?

Acquired infection is the cause of the majority of ocular toxoplasmosis. Typically, ocular toxoplasmosis presents as a focal necrotizing retinochoroiditis often associated with a preexistent chorioretinal scar, and variable involvement of the vitreous, retinal blood vessels, optic nerve, and anterior segment of the eye and about 50% will have severe visual impairment. Congenitally infected individuals are usually asymptomatic until the second or third decade of life when symptomatic eye disease occurs due to the rupture of tissue cysts and the release of bradyzoites and tachyzoites into the retina. Ref: Dominguez S.R., Levin M.J. (2012). Chapter 43. Infections: Parasitic & Mycotic. In W.W. Hay, Jr., M.J. Levin, R.R. Deterding, J.J. Ross, J.M. Sondheimer (Eds), CURRENT Diagnosis & Treatment: Pediatrics, 21e.