Predicting Visual Acuity in Early Onset Nystagmus

Abstract

In preverbal children, it is difficult to assess visual acuity accurately. If nystagmus waveforms can be used to predict visual acuity in these young patients, then they would be a useful additional clinical tool. Existing acuity predictors were assessed in 10 adults with idiopathic early onset nystagmus. The most reliable predictor in this group of patients was mean velocity of the waveform. The mean velocity of the waveform may be used in preverbal children to give an estimate of best potential visual acuity in adulthood, and estimated best potential visual acuity at the current age.

Soft Contact Lenses to Optimize Vision in Adults with Idiopathic Infantile Nystagmus: A Pilot Parallel Randomized Controlled Trial

“…The standard remains the NAFX, an acuity factor based on the NAF which takes extended foveation periods into account (Dell'Osso and Jacobs, 2002). However, velocity parameters may correlate more closely with high contrast visual acuity (Theodorou, 2006;Theodorou, 2009), and in the present study, velocity also improved in both treatment arms. There was also an improvement in amplitude which, although not correlating well with visual acuity (Bedell and Loshin, 1991), may play an important role in the psychosocial effects of nystagmus.…”

The development of infantile nystagmus

“…The potential for improvement in visual function as a result of therapy in subjects beyond the amblyopic sensitive period is likely to be limited,21 22 although there is evidence of brain plasticity even in adulthood 23 24. At least part of the visual deprivation in nystagmus may be due to amblyopia 14 25. Consequently, visual acuity is better estimated in young children if a nystagmus-induced ‘deprivation factor’ is considered in addition to the foveation characteristics 25…”

A new algorithm for automated nystagmus acuity function analysis

“…The inconsistent results from different studies may be because different weighting was given to the variation of foveation. Mean velocity alone has been shown to produce an accurate estimation of the nystagmus acuity function 11. However, only typical waveform nystagmus was analysed.…”

“…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.…”