<prompt> Minimum angle of resolution when visual acuity is 661 min of arc5 min of arc10 min of arc15 min of arc  <response>: Answer-A. 1 min of arcVisual acuity is the first test performed after taking history.Measurement of the central visual acuity is essentially an assessment of function of the fovea centralis.An object must be presented so that each poion of it is separated by a difinite interval, known as minimum angle of resolution MAR. Customarily, this interval has become one minute of an arc.The test object should subtends an angle of five minutes of an arc. 