Night blindness casts bogeyman
into the shadows
in Glasgow, Scotland
THE bogeyman has traditionally taken the blame for children’s
fear of the dark. But researchers in Scotland believe that a type
of nyctalopia — or night blindness — could be the real
culprit in some cases.
In an article published in the British Medical Journal, consultant
ophthalmologist Gordon Dutton MD and his colleagues at Gartnavel
General Hospital in Glasgow describe two children with an inherited
form of stationary night blindness.
Both were very frightened of the dark, had a history of bumping
into things at night and one child expressed a fear of shadows.
The first case was a three-year-old girl with no apparent visual
problems who had always been scared of the dark. She complained
to her parents of being able to see when the bedroom lights were
off and refused to go to the bathroom, which was down a dark hallway,
during the night. It was only when the girl’s younger sister
was diagnosed with retinal problems that the parents had the older
child’s eyes tested.
The second girl, aged two, also had a history of frequently tripping
over and bumping into objects as well as problems seeing in the
dark. Her parents reported that when she woke at night she would
cry but would not go to her parents’ bedroom. She also needed
to have curtains drawn at night because of her fear of the darkness
beyond the windows.
In both cases, electrophysiology tests revealed a “negative”
electroretinogram consistent with a diagnosis of congenital stationary
Congenital stationary night blindness — so called because
it doesn’t change throughout life — is rare and its
prevalence has not been well established, although it is about three
times more common in boys than in girls, according to the researchers.
The condition is an inherited, non-progressive disorder principally
affecting rod photoreceptor function in the retina, resulting in
impaired night vision, although there is commonly a mild impairment
in cone function, which may affect daytime central visual acuity.
The defective pathway appears to result from a signal transmission
defect from the photoreceptors.
It principally manifests itself as an increase of the dark adaptation
threshold, nystagmus, and often moderate to high short-sightedness,
although the refractive state may be far-sighted or normal. Squint,
pale or tilted optic discs, and paradoxical pupil responses have
all been linked to the condition.
There is usually no visual deficit in good lighting conditions but
mild central visual loss is common in some inherited forms. Fundus
examination is usually normal, distinguishing it from the progressive
conditions causing nyctalopia.
The researchers said children’s fear of the dark is often
dismissed as little more than attention-seeking behaviour or irrational
fear that will fade over time.
They recommend that in cases where children are afraid of the dark,
doctors need to take a full family history to find out about visual
problems. This should then be followed by a complete ocular examination
and electroretinography to determine whether the children are suffering
from night blindness.
“Night blindness in children can bring about profound fear
of the dark. Recognition of the diagnosis and the simple expedient
of giving the child control of lighting conditions can transform
family life,” the researchers’ report concluded.