Introduction

Nystagmus is a relatively common oculomotor disorder in which vision is degraded by rhythmical, involuntary ocular oscillations.1 2 A nystagmus acuity function is often used to quantify effects of surgical or pharmaceutical intervention. To calculate the nystagmus acuity function for nystagmus patients, a series of parameters, such as foveation duration,3–6 foveation eye positions,5–10 mean velocity of nystagmus slow phase,11 and a combination of foveation eye positions and eye velocities12–14 have been used. Dynamic system analysis,15 fixed point analysis16 and wavelet spectrum17 18 have also been used for nystagmus acuity evaluation. A well-known method in the field of nystagmus research is the expanded nystagmus acuity function (NAFX). The NAFX uses both foveation eye position and eye velocity criteria to calculate acuity function according …