1. We have discussed some of the disadvantages of in instrument therapy. Can you see any benefits of the AN, EC, BU or bioptogram series of stereograms? What patients would most benefit from the artificial envirnment they create?

Pts. that have significant sensory fusion challenges (strabs/amblyopes) will benefit from the BU and early AN series and any non-strab pt. that is stuck (particularily with suppression) will benefit from the more challenging series

2. Your patient has difficulty fusing the targets in the aperture rule with the single aperture. What prism (BO or BI) would you use to help the patient fuse? Why (be specific)? What dioptric lenses (plus or minus) would you use to help the patient fuse? Why (be specific)?

BI/ minus lenses BI: This patient is analogous to an high XP; BI prisms reduce the converge load and still allow fusion. Minus: This patient would gain accommodative vergence without blur if he/she accommodates accurately to the lens. It is hoped ultimately, that the pt. would be able to utilize fusional vergence to maintain fusion

3. Your patient has fused the targets in the aperture rule with the double aperture. What prism (BO or BI) would you use to increase the fusional demand on the patient? Why (be specific)? What dioptric lenses (plus or minus) would you use to help the patient fuse? Why (be specific)?

BI/ minus lenses BI/ minus lenses BI: BI prisms increase the divergence load, making this task more difficult. Minus: This patient would gain accommodative vergence that must be compensated for with increased fusional divergence. The NET vergence response must be at a steady state. Otherwise, the patient would over-converge and lose fusion

4. The idea that moving the carriage IN on a Brewster stereoscope is comparable to divergence training on an aperture rule (i.e. bringing the card series inward and using the double aperture). Please compare between the two instruments:

B. vergence demand as the card is moved inward:

Stereoscope: BI demand increase (or BO decreases) as target moves closer

Aperture rule: Single (chiascopic fusion) aperture will increase BO demand as target is moved closer

Double (orthoptic fusion) aperture will increase BI demand as target is moved closer 

C. accommodative demand as the card is moved inward:

Accommodative demand increases as any target is moved closer

5. Your patient is having significant difficulty fusing a divergence stereogram (i.e. AN series jump vergence card) at the distance setting. What would you do to help your pt. fuse (present 2 options). Are plus lenses a good option? Why or why not?

Option 1: move the carriage OUT, reducing the B I demand. (the limit here is moving the target back more than 1-3 cm will cause a blur)

Option 2: go to a jump vergence card with less demand

Option 3: apply BO prism (6 BO should do it)

Plus is not one of these options, because if applied to a pt. viewing a target at optical infinity, it will blur the patient