Which vergence range is reduced in fusional vergence dysfunction?

Which vergence range is reduced in fusional vergence dysfunction?

• A. NFV Ranges
• B. PFV Ranges
• C. Both NFV and PFV Ranges
• D. Normal Ranges

Answer: (C)

Fusional vergence dysfunction involves a reduced ability to fuse images across a range of vergence demands, so both directions of fusional vergence are diminished. Positive fusional vergence is the convergence you use to overcome base-in demand, while negative fusional vergence is the divergence you use to overcome base-out demand. In this condition, the reserves for both convergence and divergence are limited, so fusion breaks with smaller prism values in either direction. Clinically, you’ll see reduced PFV and reduced NFV amplitudes, leading to symptoms like asthenopia or headaches during near work even if basic alignment is within normal limits.

Fusional vergence dysfunction involves a reduced ability to fuse images across a range of vergence demands, so both directions of fusional vergence are diminished. Positive fusional vergence is the convergence you use to overcome base-in demand, while negative fusional vergence is the divergence you use to overcome base-out demand. In this condition, the reserves for both convergence and divergence are limited, so fusion breaks with smaller prism values in either direction. Clinically, you’ll see reduced PFV and reduced NFV amplitudes, leading to symptoms like asthenopia or headaches during near work even if basic alignment is within normal limits.