Retinal dystrophy in the oculo-auricular syndrome due to HMX1 mutation

PURPOSE

To report on the clinical and electrophysiological findings in a patient with oculo-auricular syndrome due to HMX1 mutation, with a follow-up of 12 years.

BACKGROUND

Oculo-auricular syndrome (MIM: 612109) is a rare developmental recessive condition affecting the eye and external ear that results from a mutation in the HMX1 gene. Previously described ocular abnormalities include bilateral microcornea, posterior synechiae, cataract, chorioretinal colobomas and rod-cone dystrophy.

METHODS

Retrospective chart review of an affected boy followed over a period of 12 years who had serial complete ophthalmologic examinations, fundus photographs, Goldmann perimetry and full-field electroretinograms (ERG).

RESULTS

Initial ERG tracings revealed generalized rod more than cone dysfunction. Thereafter, a rapid deterioration in rod and cone function was detected on follow up ERGs.

CONCLUSION

The retinal degeneration in the recessively inherited oculo-auricular syndrome is a progressive rod-cone dystrophy. Visual prognosis is guarded considering the progressive nature of the retinal dystrophy in early infancy.

Dog phobia in a motion-blind patient

INTRODUCTION

A prominent neurophysiological model of phobia generation holds that specific phobia might result from the uncoupling of unaware subcortical fear responses from aware cortical fear responses. Former responses are thought to be automatic and fast, providing approximate information about the external stimulus, whereas the latter responses are more controlled and allow comparison with previous experience. Since only the cortical pathway carries information available to awareness, this model also accounts for the striking irrationality of specific phobia in humans.

METHODS

Here, we report neuropsychological and neuro-ophthalmological findings in a 41-year-old patient who developed severe dog phobia following bilateral parietal lobe damage.

RESULTS

The examinations showed a severe deficit in visual motion perception (visual motion blindness or akinetopsia) as well as spatial vision. Importantly, the patient was largely unaware of his visual deficits.

CONCLUSION

Based on the present observation it is argued that irrational fear, as found in specific phobia, might not only result from a general uncoupling of aware cortical from unaware subcortical fear responses, but also from a functionally similar dissociation at the cortical level.