The throw is tightened keeping both sides of the loop loose and equal so that the loop remains round as it comes down. Placing unequal tension on either side reverses the throw into a half hitch which is a slip knot.
With this fine suture material there is no proprioceptive sense of when a throw is tight enough. The proper tension is achieved when the light in the center of the loop winks out. This can only be seen under high power. With experience, the surgeon will be able to achieve the proper tension without zooming back and forth for each throw.
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