Dutton, Gordon N.

Hamilton, R.

Sidiki, S.

English

PubMed

Enlighten: Publications

Lesson of the week
Fear of the dark in children: is stationary night blindness
the cause?
Sikander S Sidiki, Ruth Hamilton, Gordon N Dutton
Fear of the dark is a common complaint of pre›teenage
children.1 2 It should not be confused with night terrors
or panics, in which a child becomes acutely agitated
and terror›struck at night, appearing to be awake while
in fact asleep and unable to be woken.3 4 In contrast,
fear of the dark can be experienced by the conscious
child in dimly lit or dark conditions. When such fear is
excessive it is often attributed to attention seeking
behaviour or assumed to be an irrational fear that will
abate with time.
Most people can see a little in very dim lighting
conditions after a short period of adaptation.
However, a child with no visual problem obvious to
the parents and who can see normally in well lit con›
ditions can present as being unable to see at all in the
dark even after a period for adaptation. In a child who
cannot yet talk this may simply appear as fear of the
dark. We describe two patients with congenital station›
ary night blindness, a diagnosis which may be missed
without appropriate history taking from the parents,
particularly if there is no family history of visual
problems.
Case 1
A 3 year old girl had been frightened of the dark from
an early age. She had complained to her parents of not
being able to see when the bedroom lights were turned
off, prompting the natural response, “Wait until your
eyes adjust.” She would persist with her complaints of
not seeing and her parents would switch her light back
on again. She had had profound problems getting to
sleep and would not leave her bedroom in the dark,
although she would move from her dark bedroom into
the lit hallway. She also refused to enter her parents’
darkened bedroom.
Her younger sister was born with a history of being
visually unresponsive from birth and was referred at
the age of 3 months for ophthalmological investiga›
tion. She was found to have reduced vision, nystagmus,
and long sightedness but a normal ocular examina›
tion. Her vision improved considerably after glasses
were prescribed, but electrophysiological testing
suggested abnormal retinal function. This finding
prompted the parents to seek investigation of their
older daughter.
The older child’s vision was 6/12 in each eye with
no nystagmus and normal ocular examination. Her
pupils responded by dilating to a bright light
(paradoxical pupil response). Electrophysiology
showed a “negative” electroretinogram, consistent with
a diagnosis of congenital stationary night blindness.
An intensity adjustable night light was suggested
and within days she was more confident and sleeping
through the night. It was also suggested that she could
carry a torch when going out at night and that her par›
ents should draw the curtains before dusk to avoid her
fear of the darkness beyond the windows.
Case 2
A girl of 2 was referred with 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 and was very
frightened. She also needed to have curtains drawn at
night because of her fear of the darkness beyond the
windows. Examination revealed her to have normal
visual acuity and slight long sightedness. She had pen›
dular nystagmus, but pupillary and fundus examina›
tion showed nothing abnormal. There was a family
history of nystagmus and impaired night vision. Elec›
trophysiology revealed a “negative” electroretinogram
consistent with a diagnosis of congenital stationary
night blindness. Now that she is in control of her
lighting by having a bright hall light shining into her
bedroom at night and by carrying a torch outside at
night, her fear of the dark is no longer evident. She
does, however, still have some problems with shadows
on the wall, which appear to her to be holes. Her
parents have got her to feel the shadows with her
hands moving from the light areas to the dark to
appreciate the continuity of the solid wall while
explaining to her the nature of shadows cast by objects
in front of a light.
Discussion
There are many causes of nyctalopia (night blindness),
which can be divided into stationary forms such as
congenital stationary night blindness, fundus albipunc›
tatus, fleck retina of Kandori, and Oguchi’s disease5 6
and the more numerous and severe progressive forms
such as retinitis pigmentosa, Refsum’s disease, cho›
roideremia, vitamin A deficiency, and retinopathy
associated with cancer.6–8
Congenital stationary night blindness is rare and its
prevalence has not been well established, although it is
about three times more common in boys than in girls,
probably reflecting the presence of an X linked mode
of inheritance in addition to the autosomal dominant
and recessive forms.9
Congenital stationary night blindness is an
inherited, non›progressive disorder which affects prin›
cipally rod photoreceptor function in the retina, result›
ing in impaired night vision, although there is
commonly a mild impairment in cone function, which
may affect daytime central visual acuity.10–13 The defec›
tive pathway appears to result from a signal
transmission defect from the photoreceptors. It princi›
pally manifests itself as an increase of the dark adapta›
Clinical review
Fear of the dark
in children may
have a
pathological
basis
Tennent Institute of
Ophthalmology,
Gartnavel General
Hospital, Glasgow
G12 0YN
Sikander S Sidiki
specialist registrar
Department of
Clinical Physics,
Yorkhill NHS Trust,
Glasgow G3 8SJ
Ruth Hamilton
senior medical
physicist
Ophthalmology
Department
Gordon N Dutton
consultant
ophthalmologist
Correspondence to:
Ruth Hamilton
r.hamilton@
clinmed.gla.ac.uk
BMJ 2003;326:211–2
211BMJ VOLUME 326 25 JANUARY 2003 bmj.com
tion threshold, nystagmus, and often moderate to high
short sightedness, although the refractive state may be
long sighted or normal. Squint, pale or tilted optic
discs, and paradoxical pupil responses have all been
reported in association with the condition.6 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, distin›
guishing it from the progressive conditions causing
nyctalopia. The diagnosis can be established by
electroretinography.
There are several well known congenital stationary
night blindness pedigrees worldwide with varied
features,14 15 but despite the phenotypic variability
between patients three characteristics appear to be con›
sistent: night vision impairment; raised or absent rod
thresholds; and absent or diminished electroretinogram
b waves, creating a “negative” waveform (figure).12
The key to diagnosing congenital stationary night
blindness is to listen carefully to the history and to ask
in particular about a family history of visual problems.
Our patients both showed the same features: fear of the
dark, problems with mobility at night, and insisting that
curtains were drawn much earlier than others would
choose. One child had fear of shadows. A detailed his›
tory should be followed by a complete ocular examina›
tion and electroretinography. Once congenital station›
ary night blindness has been diagnosed there are
several strategies that parents can adopt to help their
children cope with and be in control of their environ›
ment. There are also manuals available to parents with
strategies to help reduce a child’s fear of the dark.2 In
addition, genetic counselling may be helpful for
parents with affected offspring. Night blindness in chil›
dren 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.
Contributors: SSS drafted the manuscript. RH provided the
electrophysiology and helped to draft the manuscript. GND
made the diagnoses, had the idea for the paper, and commented
on the draft manuscript.
Funding: None.
Competing interests: None declared.
1 Weems CF, Silverman WK, Saavedra LM, Pina AA, Lumpkin PW. The
discrimination of children’s phobias using the revised fear survey sched›
ule for children. J Child Psychol Psychiat 1999;40:941›52.
2 Giebenhain JE, O’Dell SL. Evaluation of a parent›training manual for
reducing children’s fear of the dark. J Appl Behav Anal 1984;17:121›5.
3 Kales JD, Kales A, Soldatos CR, Caldwell AB, Charney DS, Martin ED.
Night terrors. Arch Gen Psychiatry 1980;37:1413›7.
4 Lask B. Novel and non›toxic treatment for night terrors. BMJ
1988;297:592.
5 Carr RE. Congenital stationary night blindness. In: Heckenlively JR,
Arden GB, eds. Principles and practice of clinical electrophysiology of vision.
St Louis: Mosby, 1991.
6 Moore A. Inherited retinal dystrophies. In: Taylor D, ed. Paediatric ophthal›
mology. Cambridge, MA: Blackwell Scientific, 1990.
7 Purvin V. Through a shade darkly. Surv Ophthalmol 1999;43:335›40.
8 Rayner RJ, Tyrrell JC, Hiller EJ, Marenan C, Neugebauer MA, Vernon SA,
et al. Night blindness and conjunctival xerosis caused by vitamin A defi›
ciency in patients with cystic fibrosis. Arch Dis Child 1989;64:1151›6.
9 Rosner M, Hefetz L, Abraham FA. The prevalence of retinitis pigmentosa
and congenital stationary night blindness in Israel. Am J Ophthalmol
1993;116:373›4.
10 Carr RE, Ripps H, Siegel IM, Weale RA. Rhodopsin and the electrical
activity of the retina in congenital night blindness. Invest Ophthalmol Vis
Sci 1966;5:497›507.
11 Pardue MT, McCall MA, LaVall MM, Gregg RG, Peachey NS. A naturally
occurring mouse model of x›linked congenital stationary night blindness.
Invest Ophthalmol Vis Sci 1998;39:2443›9.
12 Fitzgerald KM, Hashimoto T, Hug TE, Cibis GW, Harris DJ. Autosomal
dominant inheritance of a negative electroretinogram phenotype in
three generations. Am J Ophthalmol 2001;131:495›502.
13 Sandberg MA, Pawlyk BS, Dan J, Arnaud B, Dryja TP, Berson EL. Rod
and cone function in Nougaret form of stationary night blindness. Arch
Ophthalmol 1998;116:867›72.
14 Carroll FD, Haig C. Congenital stationary night blindness without
ophthalmoscopic or other abnormalities. Arch Ophthalmol 1953;50:35›42.
15 Nettleship E. A history of congenital stationary night blindness in nine
consecutive generations. Trans Ophth Society UK 1907;27:269›93.
(Accepted 21 March 2002)
b wave
a wave
20 microvolts
Normal
0 50 100 150 200
Time after flash stimulus (ms)
Congenital stationary night blindness
Mixed rod›cone electroretinograms for normal individual and patient
with congenital stationary night blindness. The a wave is generated
by photoreceptors; the b wave is the result of subsequent
depolarisation of cells in the inner nuclear layer of the retina. In one
form of congenital stationary night blindness the a wave is
preserved, but the b wave is attenuated, giving rise to the negative
electroretinogram shown here
Corrections and clarifications
Visible signs of illness from the 14th to the 20th century:
systematic review of portraits
In this article by C Als and colleagues in the
Christmas issue of the BMJ (21›28 December,
pp 1499›501), we added the wrong affiliation for
one of the authors. Y Stüssi is a medical assistant at
the Burgerbibliothek Bern, in Berne, Switzerland,
not the director, as stated.
Photofinish
And better late than never—here’s a correction to
the Photofinish section of the Christmas issue of
2001. Three authors’ names should have been
published along with P Shah’s for the picture
submitted about the “smiling face” defect (BMJ
2001;323:1498). The missing authors—all from the
Birmingham and Midland Eye Centre, City
Hospital NHS Trust, Birmingham B18 7QU—are B
Mushtaq, senior house officer in ophthalmology; V
Kumar, specialist registrar in ophthalmology; and
U S Ramnathan, senior fellow in ophthalmology.
Endpiece
Mark Twain on evidence based
practice
It ain’t what people don’t know that hurts them it’s
what they know that ain’t so.
Mark Twain
Clinical review
212 BMJ VOLUME 326 25 JANUARY 2003 bmj.com


Fear of the dark in children: is stationary night blindness the cause?

Enlighten

Lesson of the weekFear of the dark in children: is stationary night blindnessthe cause?Sikander S Sidiki, Ruth Hamilton, Gordon N DuttonFear of the dark is a common complaint of pre›teenagechildren.1 2 It should not be confused with night terrorsor panics, in which a child becomes acutely agitatedand terror›struck at night, appearing to be awake whilein fact asleep and unable to be woken.3 4 In contrast,fear of the dark can be experienced by the consciouschild in dimly lit or dark conditions. When such fear isexcessive it is often attributed to attention seekingbehaviour or assumed to be an irrational fear that willabate with time.Most people can see a little in very dim lightingconditions after a short period of adaptation.However, a child with no visual problem obvious tothe parents and who can see normally in well lit con›ditions can present as being unable to see at all in thedark even after a period for adaptation. In a child whocannot yet talk this may simply appear as fear of thedark. We describe two patients with congenital station›ary night blindness, a diagnosis which may be missedwithout appropriate history taking from the parents,particularly if there is no family history of visualproblems.Case 1A 3 year old girl had been frightened of the dark froman early age. She had complained to her parents of notbeing able to see when the bedroom lights were turnedoff, prompting the natural response, “Wait until youreyes adjust.” She would persist with her complaints ofnot seeing and her parents would switch her light backon again. She had had profound problems getting tosleep and would not leave her bedroom in the dark,although she would move from her dark bedroom intothe lit hallway. She also refused to enter her parents’darkened bedroom.Her younger sister was born with a history of beingvisually unresponsive from birth and was referred atthe age of 3 months for ophthalmological investiga›tion. She was found to have reduced vision, nystagmus,and long sightedness but a normal ocular examina›tion. Her vision improved considerably after glasseswere prescribed, but electrophysiological testingsuggested abnormal retinal function. This findingprompted the parents to seek investigation of theirolder daughter.The older child’s vision was 6/12 in each eye withno nystagmus and normal ocular examination. Herpupils responded by dilating to a bright light(paradoxical pupil response). Electrophysiologyshowed a “negative” electroretinogram, consistent witha diagnosis of congenital stationary night blindness.An intensity adjustable night light was suggestedand within days she was more confident and sleepingthrough the night. It was also suggested that she couldcarry a torch when going out at night and that her par›ents should draw the curtains before dusk to avoid herfear of the darkness beyond the windows.Case 2A girl of 2 was referred with a history of frequentlytripping over and bumping into objects as well asproblems seeing in the dark. Her parents reportedthat when she woke at night she would cry but wouldnot go to her parents’ bedroom and was veryfrightened. She also needed to have curtains drawn atnight because of her fear of the darkness beyond thewindows. Examination revealed her to have normalvisual acuity and slight long sightedness. She had pen›dular nystagmus, but pupillary and fundus examina›tion showed nothing abnormal. There was a familyhistory of nystagmus and impaired night vision. Elec›trophysiology revealed a “negative” electroretinogramconsistent with a diagnosis of congenital stationarynight blindness. Now that she is in control of herlighting by having a bright hall light shining into herbedroom at night and by carrying a torch outside atnight, her fear of the dark is no longer evident. Shedoes, however, still have some problems with shadowson the wall, which appear to her to be holes. Herparents have got her to feel the shadows with herhands moving from the light areas to the dark toappreciate the continuity of the solid wall whileexplaining to her the nature of shadows cast by objectsin front of a light.DiscussionThere are many causes of nyctalopia (night blindness),which can be divided into stationary forms such ascongenital stationary night blindness, fundus albipunc›tatus, fleck retina of Kandori, and Oguchi’s disease5 6and the more numerous and severe progressive formssuch as retinitis pigmentosa, Refsum’s disease, cho›roideremia, vitamin A deficiency, and retinopathyassociated with cancer.6–8Congenital stationary night blindness is rare and itsprevalence has not been well established, although it isabout three times more common in boys than in girls,probably reflecting the presence of an X linked modeof inheritance in addition to the autosomal dominantand recessive forms.9Congenital stationary night blindness is aninherited, non›progressive disorder which affects prin›cipally rod photoreceptor function in the retina, result›ing in impaired night vision, although there iscommonly a mild impairment in cone function, whichmay affect daytime central visual acuity.10–13 The defec›tive pathway appears to result from a signaltransmission defect from the photoreceptors. It princi›pally manifests itself as an increase of the dark adapta›Clinical reviewFear of the darkin children mayhave apathologicalbasisTennent Institute ofOphthalmology,Gartnavel GeneralHospital, GlasgowG12 0YNSikander S Sidikispecialist registrarDepartment ofClinical Physics,Yorkhill NHS Trust,Glasgow G3 8SJRuth Hamiltonsenior medicalphysicistOphthalmologyDepartmentGordon N DuttonconsultantophthalmologistCorrespondence to:Ruth Hamiltonr.hamilton@clinmed.gla.ac.ukBMJ 2003;326:211–2211BMJ VOLUME 326 25 JANUARY 2003 bmj.comtion threshold, nystagmus, and often moderate to highshort sightedness, although the refractive state may belong sighted or normal. Squint, pale or tilted opticdiscs, and paradoxical pupil responses have all beenreported in association with the condition.6 There isusually no visual deficit in good lighting conditions butmild central visual loss is common in some inheritedforms. Fundus examination is usually normal, distin›guishing it from the progressive conditions causingnyctalopia. The diagnosis can be established byelectroretinography.There are several well known congenital stationarynight blindness pedigrees worldwide with variedfeatures,14 15 but despite the phenotypic variabilitybetween patients three characteristics appear to be con›sistent: night vision impairment; raised or absent rodthresholds; and absent or diminished electroretinogramb waves, creating a “negative” waveform (figure).12The key to diagnosing congenital stationary nightblindness is to listen carefully to the history and to askin particular about a family history of visual problems.Our patients both showed the same features: fear of thedark, problems with mobility at night, and insisting thatcurtains were drawn much earlier than others wouldchoose. One child had fear of shadows. A detailed his›tory should be followed by a complete ocular examina›tion and electroretinography. Once congenital station›ary night blindness has been diagnosed there areseveral strategies that parents can adopt to help theirchildren cope with and be in control of their environ›ment. There are also manuals available to parents withstrategies to help reduce a child’s fear of the dark.2 Inaddition, genetic counselling may be helpful forparents with affected offspring. Night blindness in chil›dren can bring about profound fear of the dark.Recognition of the diagnosis and the simple expedientof giving the child control of lighting conditions cantransform family life.Contributors: SSS drafted the manuscript. RH provided theelectrophysiology and helped to draft the manuscript. GNDmade the diagnoses, had the idea for the paper, and commentedon the draft manuscript.Funding: None.Competing interests: None declared.1 Weems CF, Silverman WK, Saavedra LM, Pina AA, Lumpkin PW. Thediscrimination of children’s phobias using the revised fear survey sched›ule for children. J Child Psychol Psychiat 1999;40:941›52.2 Giebenhain JE, O’Dell SL. Evaluation of a parent›training manual forreducing children’s fear of the dark. J Appl Behav Anal 1984;17:121›5.3 Kales JD, Kales A, Soldatos CR, Caldwell AB, Charney DS, Martin ED.Night terrors. Arch Gen Psychiatry 1980;37:1413›7.4 Lask B. Novel and non›toxic treatment for night terrors. BMJ1988;297:592.5 Carr RE. Congenital stationary night blindness. In: Heckenlively JR,Arden GB, eds. Principles and practice of clinical electrophysiology of vision.St Louis: Mosby, 1991.6 Moore A. Inherited retinal dystrophies. In: Taylor D, ed. Paediatric ophthal›mology. Cambridge, MA: Blackwell Scientific, 1990.7 Purvin V. Through a shade darkly. Surv Ophthalmol 1999;43:335›40.8 Rayner RJ, Tyrrell JC, Hiller EJ, Marenan C, Neugebauer MA, Vernon SA,et al. Night blindness and conjunctival xerosis caused by vitamin A defi›ciency in patients with cystic fibrosis. Arch Dis Child 1989;64:1151›6.9 Rosner M, Hefetz L, Abraham FA. The prevalence of retinitis pigmentosaand congenital stationary night blindness in Israel. Am J Ophthalmol1993;116:373›4.10 Carr RE, Ripps H, Siegel IM, Weale RA. Rhodopsin and the electricalactivity of the retina in congenital night blindness. Invest Ophthalmol VisSci 1966;5:497›507.11 Pardue MT, McCall MA, LaVall MM, Gregg RG, Peachey NS. A naturallyoccurring mouse model of x›linked congenital stationary night blindness.Invest Ophthalmol Vis Sci 1998;39:2443›9.12 Fitzgerald KM, Hashimoto T, Hug TE, Cibis GW, Harris DJ. Autosomaldominant inheritance of a negative electroretinogram phenotype inthree generations. Am J Ophthalmol 2001;131:495›502.13 Sandberg MA, Pawlyk BS, Dan J, Arnaud B, Dryja TP, Berson EL. Rodand cone function in Nougaret form of stationary night blindness. ArchOphthalmol 1998;116:867›72.14 Carroll FD, Haig C. Congenital stationary night blindness withoutophthalmoscopic or other abnormalities. Arch Ophthalmol 1953;50:35›42.15 Nettleship E. A history of congenital stationary night blindness in nineconsecutive generations. Trans Ophth Society UK 1907;27:269›93.(Accepted 21 March 2002)b wavea wave20 microvoltsNormal0 50 100 150 200Time after flash stimulus (ms)Congenital stationary night blindnessMixed rod›cone electroretinograms for normal individual and patientwith congenital stationary night blindness. The a wave is generatedby photoreceptors; the b wave is the result of subsequentdepolarisation of cells in the inner nuclear layer of the retina. In oneform of congenital stationary night blindness the a wave ispreserved, but the b wave is attenuated, giving rise to the negativeelectroretinogram shown hereCorrections and clarificationsVisible signs of illness from the 14th to the 20th century:systematic review of portraitsIn this article by C Als and colleagues in theChristmas issue of the BMJ (21›28 December,pp 1499›501), we added the wrong affiliation forone of the authors. Y Stüssi is a medical assistant atthe Burgerbibliothek Bern, in Berne, Switzerland,not the director, as stated.PhotofinishAnd better late than never—here’s a correction tothe Photofinish section of the Christmas issue of2001. Three authors’ names should have beenpublished along with P Shah’s for the picturesubmitted about the “smiling face” defect (BMJ2001;323:1498). The missing authors—all from theBirmingham and Midland Eye Centre, CityHospital NHS Trust, Birmingham B18 7QU—are BMushtaq, senior house officer in ophthalmology; VKumar, specialist registrar in ophthalmology; andU S Ramnathan, senior fellow in ophthalmology.EndpieceMark Twain on evidence basedpracticeIt ain’t what people don’t know that hurts them it’swhat they know that ain’t so.Mark TwainClinical review212 BMJ VOLUME 326 25 JANUARY 2003 bmj.com

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Fear of the dark in children: is stationary night blindness the cause?

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