© Copyright 2018 Orlando Alves da Silva

Classic prisms or passive prisms typically aim to compensate a visual deviationThe French ophthalmologist and physiologist Professor Baron used low potency prisms, usually 2 prismatic diopters, temporal base, in front of the left eye to treat XXXXXX.  He also published some variations of this, including placing low potency prisms on both sides and at oblique angles to treat migraines XXXXXX.  Rather than using a particular methodology to decide on the placement of prisms, Baron he did not use a predefined prismatic angulation, and used instead trial and error 

 

 

 

 

 

 

Active Prisms, also known as Proprioceptive or Postural Prisms, aim to trigger a neurological mechanism.  They are at 125 and 55 spraexternal base, to stimulate preferentially the inferior obliques; or in only 2 or 3% of all cases, horizontal external base in the case of pure right and pure left, in which it is the external rectae that are being preferencially stimulated 0D 2L or 2d 0l; 0-3, 3-0. or 0-4, 4-0.

But never above 4 prismatic diopters.

Variations on this includes recent work by Quercia and Marino who start by using the angles according to Orlando Alves da Silva, and then vary these angles to reach concordance to the Maddox test.  However, the angles should never be changed because these are the angles at which the oculormotor angles are, and when you vary the primes angles you decrease the stimulus or you stop stimulating those particular muscles.  The assumption that there are individual variations in the angle of the muscles is incorrect as if that was the case, individuals would present with strabismus.  For example, if the inferior oblique was not at the angle it should, the individual would present with strabismus as it would not be compensating the other muscles.  The patients we are talking about are non-strabic patients.