Visual and Perceptual Consequences of Congenital Nystagmus

Abstract

One way to assess the influence of retinal image motion on visual functioning in congenital nystagmus (CN) is to examine the effects of comparable image motion in observers with normal vision. A second approach is to evaluate visual functioning in subjects with CN when the retinal image motion is reduced. Using these approaches, we determined that spatial contrast sensitivity and visual acuity are not limited by the parameters of retinal image motion in some subjects with CN, but rather by a form of amblyopia. Clinical evidence from patients with bilateral refractive amblyopia suggests that a gradual improvement of visual acuity may be possible in persons with CN, if the optimal refractive correction is worn and parameters of the retinal image motion undergo long-term amelioration.

Spatial and temporal limits of motion perception across variations in speed, eccentricity, and low vision

“…Temporal frequencies of oscillation typically are in the range of 2-6 Hz, with amplitudes about 2-8-and peak slow-phase velocities often above 100-/s (Abadi & Dickinson, 1986;Abadi et al, 1999;Abadi & Worfolk, 1989;Clement et al, 2002;Jacobs & Dell'Osso, 2004;Shallo-Hoffman, Dell'Osso, & Dun, 2004). Reduced contrast sensitivity, orientation discrimination, and acuity of CN patients are believed to reflect cortical mechanisms, perhaps related to amblyopia (Abadi & King-Smith, 1979;Bedell, 2006;Chung & Bedell, 1995;Ukwade, Bedell, & White, 2002). Nystagmus also reduces motion sensitivity (Abadi et al, 1999;Acheson et al, 1997).…”

Spatial-bisection acuity in infantile nystagmus

“…Previously, we found that the amplitude, frequency and type of the simulated IN waveform has relatively little impact on normal observers’ visual performance. Rather, visual acuity and contrast sensitivity depend primarily on the characteristics of the foveation periods, both when nystagmus image motion is simulated in normal observers and when measurements are made in observers with IN (Bedell, 2006; Currie et al, 1993; Chung & Bedell, 1995; Dell’Osso & Jacobs, 2002; Dickinson & Abadi, 1985; Sheth, Dell’Osso, Leigh et al 1995). Accordingly, the simulated jerk IN waveform in the current study included a simulated foveation period which, during each block of 70 trials, had a duration of 20, 40, 80 or 120 ms.…”

“…Persons with so-called idiopathic infantile nystagmus (IN) exhibit no detectable abnormalities in the eye or the afferent visual pathways. Nevertheless, persons with idiopathic IN typically have visual acuity within the range of 20/20 to 20/100 (Abadi & Bjerre, 2002; Hanson, Bedell, White & Ukwade, 2006) and elevated thresholds on several other visual spatial tasks (Abadi & Sandikcioglu, 1975; Bedell, 2006; Bedell & Loshin, 1991; Bedell & Ukwade, 1997; Goddé-Jolly & Larmande, 1973; Guo, Reinecke, Fendick & Calhoun, 1989; Liu & Yang, 1997; Ukwade & Bedell, 1999; Ukwade, Bedell & White, 2002). …”

“…The measured reduction of contrast sensitivity therefore can be attributed to a sensory deficit. A second way to evaluate whether a sensory deficit exists in observers with idiopathic IN is to assess the visual performance of normal observers in the presence of target motion that simulates the retinal image motion in observers with IN (Bedell, 2006; Bedell & Ukwade, 1997; Currie, Bedell & Song, 1993; Chung and Bedell, 1995; 1996; 1997; Dickinson & Abadi, 1985; Ukwade & Bedell, 1999). This strategy reveals the magnitude of visual impairment that is attributable specifically to the retinal image motion in observers with IN.…”

Clinical Contrast Sensitivity Function in Patients with Infantile Nystagmus Syndrome Before and After Eye Muscle Surgery

“…Visual functions directly affected include high spatial acuity vision, contrast sensitivity, motion detection, visual recognition time, gaze and time dependent vision, depth, stereopsis, smooth pursuit, vestibular and proprioceptive functions [23,[28][29][30][31][32]. Tests of these visual based functions are usually not part of routine eye evaluations and are more commonly used in research settings but may be important measures of visual function outside the office.…”