I.    Cover Test (CT) without Prism
    A.    Assure proper conditions - illumination, target size, Rx, etc.
    B.    Unilateral Cover Test (UCT) - aka Cover/Uncover test
      i.    Differentiates between phorias and tropias
      ii.   If tropia, determines if alternating or constant
      iii.  Does not determine magnitude - does indicate direction
    C.    Alternate Cover Test (ACT)
      i.    Measures magnitude of tropia or phoria
      ii.   Confirms direction of deviation

  II.   Lateral Cover Test with Prism
    A.    Perform CT without prism to determine initial estimated deviation
      i.    If no movement is seen, use 4 BO to rule out micro-squint
      ii.   May also use 4 BI to check for movement reversal
    B.    Then perform the CT with prism
      i.    Place compensating prism in front of either eye
        a.    Use BO prism to compensate for ESO phoria or tropia
        b.    Use BI prism to compensate for EXO phoria or tropia
      ii.   Using ACT, increase prism amount from zero until no lateral
            movement of the eye is noted
      iii.  Using ACT, increase prism amount until opposite movement from
            initial estimate is just detected
        a.    ie; Eso --> Exo   OR   Exo --> Eso
      iv.   Continue using ACT and reduce prism amount until same movement as
            initial estimated is just detected
        a.    ie; Exo --> Eso   OR   Eso --> Exo
      v.    Compensating prism is amount half-way between just detected
            opposite movements [Bracket Technique]
        a.  Use prism values as close to just detectable movements as possible
        b.  Should be same as initial estimate without prism (+/- 2 PD)
        c.  Should match value at which no lateral movement was detected

  III.  Vertical Cover Test with prism
    A.    Performed CT the same as with lateral prism -- determine initial
          estimated deviation
    B.    Then perform the CT with prism
      i.    Place compensating prism in front of either eye
        a.    Use BD/BU prism on OD/OS to compensate for Right/Left Hyper/Hypo
        b.    Use BU/BD prism on OD/OS to compensate for Right/Left Hypo/Hyper
      ii.   Using ACT, increase prism amount from zero until no vertical
            movement of the eye is noted
      iii.  Using ACT, increase prism until opposite movement from initial
            estimated is just detected
        a.    ie; Hyper --> Hypo   OR   Hypo --> Hyper
      iv.   Continue using ACT and reduce prism amount until same movement as
            initial estimated is just detected
        a.    ie; Hypo --> Hyper   OR   Hyper --> Hypo
      v.    Compensating prism is amount half-way between just detected
            opposite movements
        a.  Use prism values as close to just detectable movements as possible
        b.  Should be same as initial estimate without prism (+/- 2 PD)
        c.  Should match value at which no vertical movement is detected

  IV.   References:
    A.    Clinical Procedures for Ocular Examination 
    B.    Clinical Procedures in Optometry