April 2010
Volume 51, Issue 13
ARVO Annual Meeting Abstract  |   April 2010
What Causes Nightblindness-Associated Transient Tonic Downgaze (NATTD) and Horizontal Nystagmus in Infant Boys With CSNB ?
Author Affiliations & Notes
  • H. J. Simonsz
    Ophthalmology, EMC, Rotterdam, The Netherlands
  • R. J. Florijn
    Molecular Ophthalmogenetics, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands
  • A. A. B. Bergen
    Molecular Ophthalmogenetics, Netherlands Inst for Neuroscience, Amsterdam, The Netherlands
  • M. Kamermans
    Retinal Signal Processing, Netherlands Insitute for Neuroscience, Amsterdam, The Netherlands
  • Footnotes
    Commercial Relationships  H.J. Simonsz, None; R.J. Florijn, None; A.A.B. Bergen, None; M. Kamermans, None.
  • Footnotes
    Support  None.
Investigative Ophthalmology & Visual Science April 2010, Vol.51, 1466. doi:
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      H. J. Simonsz, R. J. Florijn, A. A. B. Bergen, M. Kamermans; What Causes Nightblindness-Associated Transient Tonic Downgaze (NATTD) and Horizontal Nystagmus in Infant Boys With CSNB ?. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1466.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose: : In congenital stationary nightblindness (CSNB), apart from a rapid horizontal nystagmus, a transient tonic downgaze occurs. The coexistence of horizontal and vertical nystagmus has been previously described in dark-reared cats. We explored its causes.

Methods: : Eleven infant boys presented with chin-up head posture, tonic downgaze and, on attempted upgaze, large-amplitude upward saccades with deceleration during the slow phase downward. The gaze-evoked upward saccades disappeared at the age of two or three years. They also had high-frequency, small-amplitude horizontal pendular nystagmus that remained. Among the infant boys were two pairs of maternally related half-brothers, two cousins, and two siblings. We sought for underlying mutations in CACNA1F and NYX.

Results: : Visual acuity ranged from 0.1 to 0.6. ERG-amplitudes (both A- and B-wave) were reduced. Severe myopia was found in five cases. Eight boys had CACNA1F mutations, and one boy had a NYX mutation, compatible with iCSNB or cCSNB, respectively.

Conclusions: : CACNA1F is located on the rod side of the rod - ON-bipolar-cell synapse, whereas NYX is located on the side of the ON-bipolar cell. Under scotopic conditions the rod signals travel via the rod ON-bipolar cell via AII amacrine cells to cone ON- and OFF-bipolar cells. Under photopic circumstances these AII amacrine cells may play a role in the detection of approaching objects. Under conditions where the rod ON-bipolar cells are not receiving a proper synaptic input, the receptive field structure of ganglion cells may be different or ganglion cells may spontaneously oscillate. It is conceivable that a resulting bias in motion detection and / or oscillation of retinal ganglion cells is related to the emergence of nystagmus or tonic downgaze.

Keywords: nystagmus • photoreceptors • genetics 

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