Percival criterion

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criterion, Percival 

Rule proposed by Percival to establish whether a patient is going to experience discomfort in binocular vision. It states that if Donders' line (or demand line) lies within the zone of comfort, which is the middle third of the total range of relative convergence (to the blur points), Percival's criterion of comfortable binocular vision is fulfilled. If it is not, appropriate prisms, spherical lenses or visual training can be used to shift the demand point within the zone of comfort. In this criterion, no reference is made to the actual phoria of the subject and for this reason it has been criticized by several authors. Syn. middle third technique. See relative convergence; binocular vision single zone of clear.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann
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Those who slaughtered 132 Pakistani children had had crossed the Durand Line from their zone of comfort; Germany's armed groups were largely on their own, though the Red 'battalions' did indeed receive some help from communist Russia, itself in chaos.
All of these relics of despair began to diminish with each person who opened up about their feelings and accounts of their struggles. This was a true zone of comfort."
Were you ever afraid or did you ever feel the urge to stay in your zone of comfort instead of fighting the unbeatable foe?
Perhaps it is time to let the children develop their own space and create a zone of comfort.
After all, beyond the zone of comfort they have set, there is the outside world.
In order to stay within their "zone of comfort", commercial bankers have defied the SBP's cautions regarding the dangers of low lending to the private sector as it will hit overall production and result in reducing profits.
Taken away from their "Zone of Comfort," they make a decision to transform their new environment into a "Zone of Conquest."
India, May 7 -- Sense of familiarity and a zone of comfort are two sentiments close to the hearts of a lot of Windows users.
Or that young Turk, Mater Mater, the supposed intellectual (my italics) rebirth of Al Wefaq, now safely sequestered in the Land of the Free and the home of the Brave, who from his zone of comfort over 5,000 miles away, proclaimed that the bombings were "odd" and sounded as though he was somehow excusing them!
He deploys a degree of conceptual rigor and intellectual integrity that has shifted many sociopolitical theorists away from their zone of comfort, and forced many others to think much harder and productively about what makes them comfortable.
But that same zone of comfort became a barrier to accepting my platform premise,; that to stay in that comfort zone, while businesses were in desperate need of a new and better approach to managing risk, was to risk your position as "risk manager." After all, what should an executive team or board expect from a "risk manger" but that all material risks to a company are addressed.