Determining the Add for the Presbyope
PURPOSE To determine the near prescription for the presbyopic patient．
Note：Near corrections are generally prescribed based on the final distance refraction．The add is the difference between the distance correction and the near correction．




EQUIPMENT
·Phoropter with a near point rod.
·Trial frame．
·Trial lens set．
·Near point card with small block of 20/30 letters.
·Near VA card．




SET-UP
·Complete the distance refraction and leave these lenses in the phoropter for subsequent testing．This provides the distance portion on which to base the final near prescription．
·Seat the patient behind the phoropter, which is set to his near PD．
·Place the near point card with a block of 20/30 letters on the near point rod at 40 cm from the patient．
·Brightly illuminate the near point card．




STEP-BY-STEP PROCEDURE
1．Select the tentative add．Choose the tentative add by one of the following techniques．The order of presentation here is not meant to imply order of preference．
a．Age and refractive status(see Table 3-2)．

b．Fused cross cylinder(see procedure in Chapter 4)．The endpoint of the fused cross cylinder technique can be used as the tentative add．
c．“Half the amp in reserve” rule．Convert the patient’s customary near working distance into its dioptric equivalent．From this quantity subtract 50% of the patient’s amplitude of accommodation，as determined by the push- method (see procedure in Chapter 2)．The remainder can be used as the tentative add (see Figure 3-22)．
d．Entering prescription and VA．Add +0.25 D to the patient’s entering net near prescription，as determined by lensometry, for each line of reduction in the near VA below 20/20．If the distance prescription is to be changed，this change must be taken into account in making the calculation of the tentative add(see Figure 3-23)．




2．Refine the add．Algebraically add the NRA and PRA findings (see Chapter 4) and divide the sum by 2．Algebraically add the resulting quantity to the tentative add from step 1．




3．Finalize the add．
a．To this point, testing has been done at 40 cm．However，large individuals tend to hold reading material at distances greater than 40cm and small individuals tend to hold reading material at distances closer than 40cm．Assess the stature of the patient and adjust the add by decreasing it by +0.25 D for The large patient and increasing it by +0.25 D for the small patient．
b．Compare the adjusted，relined near prescription to the patient’s entering near prescription．If you plan to increase the near prescription, the amount of the increase should be as small as possible and should correspond to the increase in near VA．
c．Trial frame the adjusted, relined near prescription．
d．Through this correction，take the near VA monocularly and binocularly．The best corrected VA at near should be equivalent to the best corrected distance VA．If it is not．consider increasing the add．
e．Measure the linear range of clear vision as follows．Instruct the patient to bring some printed material in toward himself until it just blurs．Measure the distance from the trial flame to the printed material．Then, instruct the patient to move the material away from himself until it just blurs．Measure this distance．Record the blur in point and the blur out point in inches or centimeters．
f．The patient’s customary near working distance should be at the dioptric midpoint of the linear range of clear vision．Increase the add if the midpoint of the range is too far removed from the patient．Decrease the add if the midpoint of the range is too close to the patient．
g．Recheck the near VA through the final add．The VA at near should be equivalent to the distance VA．If it is not, consider increasing the add and repeat step 3．
h．The add should be responsive to the patient’s visual needs．The final considerations are patient comfort and satisfaction with the add．




RECORDING
·For each eye write the word “add” followed by the dioptric power of the final add (not the net near Rx)．
·Record the near VA for each eye through the final add．
·Write “range OU．”
·Record the distance from the patient at which print first began to blur when the patient，with both eyes unoccluded，brought the material toward himself．This is his near point through the add．
·Write a dash．
·Record the distance from the patient at which the print first began to blur when the patient，with both eyes unoccluded，pushed the material away from himself. This is his far point through the add.




EXAMPLE
OD add +1.25 VA 20/20 @ 16″
OS add +1.25 VA 20/20 @ 16″
range OU 10″-21″