Achiasmia and unilateral optic nerve hypoplasia in an otherwise healthy infant

Pomeranz, Howard D.; Agadzi, Anthony K.; Ekesten, Björn

doi:10.1111/j.1600-0420.2005.00523.x

Cited by 12 publications

(18 citation statements)

References 15 publications

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“…A third, unilateral VEP asymmetry defined the absence of optic-nerve-fibre decussation at the chiasm from the one eye, while from the other eye with severe optic nerve hypoplasia, the VEP was absent. Such unilateral VEP asymmetry has been observed previously with flash stimulation in one child [11], although in the present study, this was observed with pattern onset stimulation in two of these achiasmatic children.…”

Section: Ocular Findings and Mri Characteristicscontrasting

confidence: 66%

“…Therefore, the lack of uniformity in VEP asymmetries shown previously has also been found in the present study. In the majority of previous studies, ipsilateral asymmetry was observed with flash and pattern onset stimulation [3][4][5][6][7], while crossed asymmetry and crossed contralateral positivity have also been associated with achiasmia [8][9][10][11][12]36]. In the present study, the ipsilateral asymmetry defines the absent optic-nervefibre decussation at the chiasm for both of the eyes.…”

Section: Ocular Findings and Mri Characteristicsmentioning

confidence: 47%

“…Colour vision was tested with Ishihara plates, while visual field testing was performed with Goldmann perimetry and static perimetry (Octopus perimeter, G2 top programme). Table 1 gives the ophthalmological findings of the children with achiasmia (children 1-4) and with ocular albinism (children [5][6][7][8][9][10][11][12][13][14][15][16][17][18]. All of these children had infantile nystagmus, normal near vision and normal colour vision (analphabetic or Ishihara colour plates).…”

Section: Ophthalmological Examinationmentioning

confidence: 99%

“…In achiasmia, a number of VEP asymmetries have been described, with all of them defining absence of or reduced optic-nerve-fibre decussation at the chiasm. From each eye, the optic nerve fibres that mainly or solely project into the ipsilateral hemisphere produce VEP distributions that have been defined as: ipsilateral asymmetry [3][4][5][6][7], crossed asymmetry [8][9][10][11] and crossed contralateral positivity [12]. In all forms of albinism, VEP asymmetries have been described as contralateral asymmetry [13,14] and albino crossed asymmetry [15][16][17].…”

Section: Introductionmentioning

confidence: 99%

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VEP characteristics in children with achiasmia, in comparison to albino and healthy children

et al. 2012

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Achiasmia is a rare disorder of visual pathway maldevelopment that can show diverse clinical and magnetic resonance imaging spectra. The aim of this study was to define the characteristics of visual evoked potentials (VEPs) that differentiate abnormal optic-nerve-fibre decussation in children with achiasmia versus children with albinism and healthy children. In four children with achiasmia, the following VEP characteristics were studied and compared to children with ocular albinism and with healthy control children: (a) flash and pattern onset VEP interhemispheric asymmetry; (b) flash N2, P2 and onset C1 amplitudes and latencies; (c) interocular polarity differences in interhemisphere potentials; and (d) chiasm coefficients (CCs). In the children with achiasmia, VEPs were related to an absence of or reduced optic-nerve-fibre decussation at the chiasm and showed: ipsilateral asymmetry, significantly higher VEP amplitudes over the ipsilateral hemisphere (p < 0.05), interocular inverse polarity and negative CC. Other VEP features (uncrossed asymmetry and positive CC) were also seen if additional visual pathway maldevelopment (such as severe optic nerve hypoplasia and/or absence of the optic tractus on one side) were associated with achiasmia. In the children with albinism, the VEPs were related to excess optic-nerve-fibre decussation at the chiasm and showed: contralateral asymmetry, significantly higher VEP amplitudes over the contralateral hemisphere (p < 0.001), interocular inverse polarity and negative CC. In achiasmia and albinism, the VEPs to flash stimulation were more robust and more clearly distinguished between the conditions compared with the VEPs to pattern onset stimulation. VEPs in achiasmia are associated with absent or reduced optic-nerve-fibre decussation, where ipsilateral interhemispheric asymmetry is associated with interocular inverse polarity and a negative CC.

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Section: Ocular Findings and Mri Characteristicscontrasting

confidence: 66%

Section: Ocular Findings and Mri Characteristicsmentioning

confidence: 47%

Section: Ophthalmological Examinationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

VEP characteristics in children with achiasmia, in comparison to albino and healthy children

et al. 2012

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“…Cases have been reported with this anomalous asymmetry of response detected using the pattern onset VEP [1][2][3] and flash VEP [4][5][6][7][8], and similar cases have been reported in which the absence of the chiasm is the only significant abnormality (e.g. [9]).…”

Section: Discussionmentioning

confidence: 88%

Congenital absence of optic chiasm: demonstration of an uncrossed visual pathway using monocular flash visual evoked potentials

Brown

Southern²,

Anbarasu

et al. 2006

Doc Ophthalmol

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A 35 month old child was referred for electrophysiology testing with pendular nystagmus, corresponding head oscillations and reduced vision. Flash visual evoked potential (VEP) revealed large responses at the right occiput (but not the left occiput) from the right eye and similar large responses at only the left occiput from the left eye, indicating absent/deficient crossover at the chiasm. A magnetic resonance imaging (MRI) scan subsequently confirmed absence of the optic chiasm. There was no other evidence of midline brain defects. Her subsequent development to age 11 has been followed. The nystagmus has remained mainly horizontal but a torsional component was noted from age 5 years and described as see-saw at age 6 years. A small right esotropia was noted at 6 years and spectacles prescribed for low hypermetropic refractive error. Bilateral superior rectus recessions at age 7 years produced an improved head posture. Her visual acuity has remained stable at around 6/24 from age 4 years. No binocularity nor stereopsis has been demonstrated over subsequent visits.

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VEP asymmetry with ophthalmological and MRI findings in two achiasmatic children

et al. 2007

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Achiasmia is a rarely diagnosed visual pathway maldevelopment where all or the majority of nasal retinal fibres fail to decussate at the optic chiasm. It has been identified by neuroimaging and also by visual evoked potential (VEP) asymmetry. VEP asymmetry has not been defined consistently in previous studies. The aim was to study VEP asymmetry to flash stimulation in two children with maldevelopment of the optic chiasm in comparison to control children. Both children had congenital nystagmus, optic nerve hypoplasia with a bilateral small double ring, bitemporal visual field defect and normal colour vision. In child 1 visual acuity in both eyes was 0.1, in child 2 it was 0.2. MRI showed reduced chiasmal size in child 1, while in child 2 it was combined with other midline abnormalities. VEP to monocular flash stimulation showed in both children distinctive occipital distribution, which was not observed in control children. The N2 wave was distributed asymmetrically over the ipsilateral hemisphere to the stimulated eye, while the P2 wave was distributed over both hemispheres. The P2 wave was however better defined over the ipsilateral hemisphere. Flash VEP occipital distribution remained similar in child 1, who was followed from 10 months to 9 years. These cases of achiasmia demonstrate a distinctive VEP asymmetry in the distribution of the flash VEP N2 wave, as well as the expected structural defect determined by neuroimaging.

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Achiasmia and unilateral optic nerve hypoplasia in an otherwise healthy infant

Cited by 12 publications

References 15 publications

VEP characteristics in children with achiasmia, in comparison to albino and healthy children

VEP characteristics in children with achiasmia, in comparison to albino and healthy children

Congenital absence of optic chiasm: demonstration of an uncrossed visual pathway using monocular flash visual evoked potentials

VEP asymmetry with ophthalmological and MRI findings in two achiasmatic children

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