In fusional vergence dysfunction, which finding would you LEAST expect?

• A. Reduced Accommodative Testing
• B. Reduced NFV Ranges
• C. Reduced PFV Ranges
• D. Normal Phoria Measurement at Distance and Near

Answer: (A)

Fusional vergence dysfunction presents with a problem in the vergence system—the ability to fuse images—while the basic alignment at rest and the accommodation system are typically normal. The defining feature is reduced fusional vergence ranges, both negative fusional vergence (NFV) and positive fusional vergence (PFV). That means the patient struggles to sustain single vision when prism demands or vergence demands increase, even though their phoria at distance and near tends to be within normal limits.

Because the accommodation system is preserved in this condition, accommodative testing usually comes back normal. So, you wouldn’t expect reduced accommodative testing in fusional vergence dysfunction. The normal phoria measurements at distance and near fit the same pattern: alignment at rest is not the primary issue, the difficulty is in the ability to fuse images under vergence stress, reflected by the reduced NFV and PFV ranges.