Hi to everybody and welcome to OptoTubeChannel, the first Italian YouTubeChannel dedicated to Optometry
Tosay let's talk about NPC test or near point of convergence which is that point in the near space
over which is not longer possible to have a single vision. The test is performed in a space full binocular
with the patient sit in front of the patient and the target which is a wolf ball for his features about sphericity
and specularity, letting to the patient to see him/her self into it, so to abtract more attention
At this point the practicioner place the target simmetrically to the patient's body, moving 
along his/her sagittal plan, starting from a distance of 0.50 meters and bringing it near
During the bringing near phase, the practicioner aske to the patient, when and if he/she sees the target blur
then when and if he/she sees the target double, and then with a come back movement, the practicioner
ask to the patient when he/she got back a single binocular vision. So at this point all these three results
have to be wrote down, blur-break of binocular vision-single vision, and this triple result represents
the NPC test result. Now, each component of this result has a meaning, infact the blur represents
the spatial point in which the link between vergence and accomodation, changes, this bond deteriorates, it loses
Then the break point in which there's a double vision is the spatial point in which our visual system
from the fusional point of view cannot hold a binocular vision, so it becomes a biocular vision
so there's diplopia. then we have recovery which represents from a functional point of view
the solution which our visual system offers to recovery a single binocular vision.
There could be some situations more particular in which the NPC arrives at the nouse and the patient doesn't
percept diplopia nor blur, but we can see an ocular deviation of one eye. In that case he/she is
suppressing and is happened a deviation tring to hold a single vision but with performance drops
switching from a binocular to monocular vision, even if he/she doesn't percepts diplopia. In that case we have 
to write down the distance, or better the spatial point, at which happends the deviation and that will be the break
So this is write down as NPC data. Then we could have that the patient, during the bringing phase, moves
in some direction or goes back, and all those movements must be wrote down
as "pseudo-break-data" because the patient make them to avoid double vision, they are a first disconfort 
element which could be always write down. NPC to be considered normal has to be at nouse
so 0.02 - 0.03 meters from the eyes or to be considered sufficient it must be abou 0.05 - 0.06 meters from nouse
while insufficien NPC  is for result higher than 0.1 meters like in convergence insufficiency.
So this is all for  NPC test, if you liked subscribe channel and leave a like!
Let's see at the next opto-video!
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