The College of Optometrists

we should measure npc with the near correction, agreed?

Using a trial frame without full aperture lenses, i find that the target often dissappears from one eye's view before diplopia occurs.

I always adjust the pd to be as small as possible on the trial frame without excessively squashing the nose.

Any tips/suggestions?

Also, would you expect npc to become greater with age? As levels of accommodation decrease, does this drive less convergence?

i dont think npc changes with age, it stays the same unless there are other problems (Pathology?)

i always measure npc with trial frame and appreciate the problem, but is it not sufficient to right down the closest point we can measure? not sure...sorry!

NPC gets longer with increasing presbyopia by a few cm. Infact conv insuf is fairly common in the elderly.

To do NPC the px must be fixing on a tiny target acurately - so may well need spex on to see the target. As NPC is closer than the near point - the target will blur anyway. If the v is poor anyway - you can use a pen torch and watch the corneal reflex for symetry.