The College of Optometrists

with regards to a pre pres,i wouldnt adjust the PD for near testing,since the specs are to be used to distance work,but for near CT should i,as i dont want to induce any prismatic effect,and for A.O.A & NPC i should so that the prismatic effect does not influence the readings?

yes you should. monocular AOA should not really be affected, but binocular AOA, convergence, and near cover test could all be affected by induced prismatic effect. obviously this effect will be more significant in higher refractive errors.

don't recall changing to near pd for these or being advised to do so.

If a pre-pres, wearing spex near cover would be expected to be done in habitual situation ie distance pd. If you quantify the prisms involved ie 0.6prism for a -2.00D Rx should make no difference to what you see on cover. yes -6D gives 1.8prism but should not alter situation. Obviously theoretically may be more significant for hyperopes due to the base out nature of the prism. So time saved not adjusting pd could be used to verify associated phoria on mallett.

if binoc status is so fragile surely you'd want to test AOA and NPC under real conditions.

thanks dburns - clearly explained and I would have to agree - think I was too quick to reply earlier without thinking it through!

I agree in a pre-presbyope it is much more useful clinically to measure all of the above with distance Rx set to distance pd. Apologies for causing confusion.