Saccadic oscillations and intrusions preceding the postnatal appearance of congenital nystagmus

Positional ocular flutter and thickened optic nerves as sentinel signs of Krabbe disease

A 5-month-old boy developed a large-amplitude, horizontal pendular flutterlike oscillation of the eyes, when placed in the supine position. Magnetic resonance imaging (MRI) 1 month earlier had shown isolated thickening of the optic nerves and chiasm without other central nervous system signal abnormalities. Repeat MRI at 5½ months of age showed a constellation of central nervous system signal abnormalities suggestive of Krabbe disease. The diagnosis was confirmed with serum enzymatic and genetic testing. This case demonstrates that positional ocular flutter can be a presenting sign of Krabbe disease and reinforces the observation that isolated thickening of the anterior visual pathways can antedate other central nervous system abnormalities on MRI.

Ocular motor outcomes after bilateral and unilateral infantile cataracts

We wished to study how the severity and duration of early onset visual deprivation affects eye alignment and ocular stability. Thirty-three patients (aged 1 week to 12.8 years) with infantile cataracts (16 bilateral, 17 unilateral) were examined for periods up to 61 months. Twenty-three patients were considered to have cataracts, which were a major obstacle to vision (major form deprivation), 9 of whom underwent surgery within 8 weeks of birth (mean and SD=5.2+/-2.3 weeks) and 10 after 8 weeks (mean and SD=33.9+/-29.7 months). Eye alignment and fixation stability was measured using infrared recording systems and video. Visual acuity was assessed using forced-choice preferential looking techniques in the neonates and infants and with optotypes in the children. Fifteen of the 23 (65%) patients who experienced major form deprivation exhibited a nystagmus, of which 11 (73%) were manifest latent nystagmus (MLN). Nineteen of the 23 (85%) had strabismus. Of the nine patients who underwent early surgery (< or =8 weeks), two displayed a preoperative nystagmus whilst between 10 and 39 months post-operatively 8 (89%) exhibited a nystagmus. Of the group of 10 patients with minor cataracts only 2 (1 late surgery, 1 no surgery) had nystagmus and 2 strabismus. We conclude that following optimal post-operative management of infantile cataracts a sustained nystagmus--typically an MLN--is the most likely ocular motor outcome, even when the period of deprivation is as short as 3 weeks.

Fixational eye movements in normal and pathological vision

Most of our visual experience is driven by the eye movements we produce while we fixate our gaze. In a sense, our visual system thus has a built-in contradiction: when we direct our gaze at an object of interest, our eyes are never still. Therefore the perception, physiology, and computational modeling of fixational eye movements is critical to our understanding of vision in general, and also to the understanding of the neural computations that work to overcome neural adaptation in normal subjects as well as in clinical patients. Moreover, because we are not aware of our fixational eye movements, they can also help us understand the underpinnings of visual awareness. Research in the field of fixational eye movements faded in importance for several decades during the late 20th century. However, new electrophysiological and psychophysical data have now rejuvenated the field. The last decade has brought significant advances to our understanding of the neuronal and perceptual effects of fixational eye movements, with crucial implications for neural coding, visual awareness, and perception in normal and pathological vision. This chapter will review the type of neural activity generated by fixational eye movements at different levels in the visual system, as well as the importance of fixational eye movements for visual perception in normal vision and in visual disease. Special attention will be given to microsaccades, the fastest and largest type of fixational eye movement.

X-linked infantile periodic alternating nystagmus

OBJECTIVE

To describe the clinical and electrophysiological characterization of four family members from three generations who have X-linked infantile periodic alternating nystagmus (XIPAN).

METHODS

Complete clinical ophthalmological evaluation, pedigree analysis, electroretinograms (ERG), eye movement recordings (EMR), color vision, and fundus photography were performed on all subjects.

RESULTS

Three males in two generations and one female were examined. Clinical examinations showed a jerk/pendular nystagmus with a latent component, strabismus, and a significant refractive error in the three affected males, while the female had only myopic astigmatism. ERG, color contrast, and fundus examinations were normal in all four family members. All four family members showed EMR abnormalities with infantile jerk/dual jerk and pendular nystagmus waveforms. The female had nystagmus present on EMR only and all patients showed (a)periodicity to their nystagmus.

CONCLUSIONS

In this family with no other congenital visual sensory system disease, affected males had obvious periodic alternating nystagmus, strabismus, and refractive errors, while the female had clinically "silent" periodic nystagmus that is probably a marker for the carrier state.