1. Proximal Convergence

3. Proximal Convergence:
P = T + N – F – A
P = proximal vergence
T = angle of total convergence = 10 x Pd(mm)
N = near phoria distance(cm)
F = far phoria
A = accommodative convergence = gradient AC/A x accommodative demand (diopters)

6. Problem 29: Perlita
Distance: ortho Near: 6 eso Near +1.00: 3eso
BI: x / 11 / 3 BI: 7 / 13 / 3 Near -1.00: 9eso
BO: x / 17 / 10 BO: 19 / 21 / 9
1. What is the gradient AC/A?
2. What is the calculated AC/A?
3. What could account for the difference?
4. On the basis of the gradient phoria line, what is the anticipated distance phoria? The difference between the measured distance phoria and the anticipated distance phoria is an estimate of proximal vergence.
5. Calculate the amount of proximal vergence from the equation:
P = T + N – F – A.

8. Problem 30: Erelio
Distance: 3eso Near: 6eso Near -1.00: 10 eso
BI: x / 8 / 0 BI: 10 / 18 / 8
BO: 24 / 32 / 12 BO: x / 30 / 26
1. What is the gradient AC/A?
2. What is the calculated AC/A?
3. What could account for the difference?
4. On the basis of the gradient phoria line, what is the anticipated distance phoria? The difference between the measured distance phoria and the anticipated distance phoria is an estimate of proximal vergence.
5. Calculate the amount of proximal vergence from the equation: P = T + N – F – A.

11. Reading Add: initial power
calculation using the measured amplitude of accommodation with Donder’s rule: Add = working distance (D) – ½ amplitude Landolt’s rule: Add = working distance (D) – 2/3 amplitude
dynamic retinoscopy
binocular fused cross-cylinder

13. Reading add: power refinement
Adjust the add power so that the NRA = PRA and perform all of your binocular phorometrics through this add power at 40 cm. This standardizes test conditions so that you can compare results over time and across patients.
Trial frame the distance lens and the reading add to demonstrate that 2 powers are needed for 2 viewing distances and to refine add power depending on preferred near working distance.

15. Apparent Convergence Insufficiency:
Presbyopes routinely show high exophorias at near with not enough PFV to meet Sheard’s criterion (apparent CI).
Usually they are asymptomatic.
Sheedy & Saladin (1975) proposed that presbyopes use accommodative convergence free of accommodation in addition to PFV when fused and so really have no problem.

16. True Convergence Insufficiency:
If your presbyope is symptomatic, measure the associated phoria at near through the reading add.
Incorporate any BI prism found into the reading Rx by decentering the add or by prescribing single vision readers.
Or train PFV.

18. Problem 27: NPA: 3.50D
Distance: 1 exo Near with +0.50D: 8 exo
BI: x / 12 / 4 BI: x / 22 / 16 NRA: +2.00
BO: x / 18 / 12 BO: x / 12 / 4 PRA: -1.50
1. What reading lens power should be prescribed?
2. Does the patient have adequate binocularity at near through the reading add?
3. He is complaining of eyestrain while reading through his current glasses, which are virtually the same as what you are finding.
4. Your plan is to measure his ____________________at near through the reading add and to prescribe prism on this basis.
5. Failing this, you could use Sheard’s criterion, which would recommend __________.

20. Problem 28: NPA: 2.00D
Distance: 2 exo At 33cm with +1.75D add:11 exo
BI: x / 12 / 8 BI: x / 24 / 14 NRA: +0.75
BO: x / 12 / 4 BO: x / 8 / 2 PRA:-0.75
1. Does the patient have adequate binocularity at the preferred working distance through appropriate the reading add?
2. He does not complain of any discomfort when doing near work.
3. What is your diagnosis?
4. What is your plan?