Transcript Cong nystagmus - Private Eye Clinic

6yo
 CN
 PHx & FHx: nil; no consanguinity
 c/o: AHP
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
O/E:
› AHP - L face turn 25 degrees
› H Nystagmus, with RG (LFT) and
›
›
›
›
convergence Nulls
VA (D) R 6/38
L 6/48
BEO 6/30
(N) R 6/63
L 6/400 BEO 6/19
Titmus: 400’’
CR: R+L -0.25D
F: difficult. No Cyclotorsion
Convergence
null, traditionally
checked for D
with Bilateral
7pd BO and 1.50D to address
induced
accommodation
Improved AHP
with 12 BO
prisms
& bilateral -2.00
VA with BEO:
6/21
Foveation timeL beating to R beating
Wave form
Amplitude
Frequency
Nystagmus is an oscillation of the ocular
motor system.
 It can be: pendular-no fast and slow phases
jerk-a slow phase away from the
target, followed by a return saccade
a combination of both .
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--------------------------------------------------------------------Khanna and Dell’Osso: Diagnosis and Treatment of INS.
TheScientificWorldJOURNAL (2006) 6, 1385–1397
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Several types of Nystagmus in infancy:
1. Infantile Nystagmus Syndrome, INS
(=Congenital Nystagmus, CN). Most
common form.
2. The Fusion Maldevelopment Nystagmus
Syndrome, FMNS (= Latent Manifest Latent
Nystagmus, LMLN).
3. The Spasmus Nutans Syndrome (SNS).
4. Nystagmus secondary to known
cerebellar or vestibular disease.
Appear at birth/early infancy, persists throughout life.
Causes: 1. The usual cause: a bilateral symmetric sensory
defect at a critical period of life (high refraction, albinism,
aniridia, retinal dystrophies, optic nerve hypoplasia,
congenital cataract).
2. Normal sensory state and an inherited waveform
(Most well studied is FRMD7)
3. Abnormal sensory state and a pathognomonic
waveform – a type of CSNB.
 Waveform recordings: Pendular/ jerk waveforms.
 Unlike CN, LMLN has linear or decreasing velocity slow
phases;
 Clinically, only eye movement recordings can reliably
differentiate the two.
 Both CN and LMLN are more frequent in children with
periventricular leukomalacia (PVL).
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Caused by an asymmetric sensory
and/or motor defect at a critical period
(usually strabismus).
 Present only with occlusion of one eye or
when both eyes open,- only one eye
fixating.
 It is always associated with strabismus
and has a directional change with
ocular cover, beating away from the
covered eye towards the fixating eye.
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Spasmus nutans is a dysconjugate
asymmetric high frequency Nystagmus
with head nodding and tilt.
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A complete ocular exam, (VA at different gaze angles, AHP
assessment, identification of asymmetric (a)periodic
alternating nystagmus (APAN)- (*if undetected, may result in
improper muscle-shifting surgery),- ask parents if AHP is stable
(if EVER seen FT to the other side)? If they have  possible
cong PAN [waveform is same as CN]. Must observe in office
for >10 minutes.

Slit-lamp examination (iris transillumination and fundus)
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Cycloplegic refraction (correct with glasses or contact lenses).
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Paradoxical pupils – only seen in some retinal dystrophies
1. Base-out prisms - induce convergence null in a
binocular patient.
Usually 7D base-out prisms are added to the patient’s
refraction with a –1.0D added.
Once converged, CN remains damped at most gaze
angles (especially those in the central ±20° of gaze).
2. Soft contact lens- corrects refractive errors and
improve the Nystagmus waveform.
Surgical treatment has classically been
performed for two main reasons:
correction of anomalous head posture
and improvement of VA.
 Oscillopsia is not a characteristic of CN
and thus not an indication for
treatment (unlike acquired Nystagmus).
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(1) Kestenbaum surgery — takes
advantage of gaze-angle null and
compensatory head posture with a
“null” zone. A four-muscle surgery
consisting of yoke paired recessions and
resections of the horizontal recti, to shift
the resting position of the eyes in the
direction of the head turn.
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(2) Artificial Divergence Surgery . Bilat medial
small recessions, that create mild divergence
(exophoria) of the eyes such that the patient is
forced to employ his fusional convergence to
see, and this convergence damps the
Nystagmus.
Used only if the patient has fusion and
responded to a trial with base-out prisms.
beware:
Albinos all have positive angle kappa and look
slightly divergent when perfectly straight to
cover test. Artificial divergence surgery can
make these look worse.
(3) four- horizontal rectus
tenotomy_resuture procedure –
recommended If there are neither
convergence nor gaze nulls.
 Tenotomy is thought to affect eyemuscle proprioceptives and reduce the
slow-phase, damping the Nystagmus
w/o altering the motor balance (*also
successful in damping oscillopsia in
acquired Nystagmus).
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(4) Large recessions of all the horizontal
recti- recommended by some strabismus
surgeons.
 It affects the ocular motility and causes
XT.
 Not recommend for patients who have
binocularity (at risk to develop diplopia).
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(5) Strabismus surgery- should be combined
with Nystagmus surgery;
E.g. If an ET is present, bimedial horizontal
rectus recessions may be added to
Nystagmus surgery to correct the
strabismus.
Two null points recorded: at RG 15-20
degrees and even more markedly at
near.
 An intervention which could take
advantage of both of these - might be
the most beneficial to the boy.
 A bilateral BO prism trial –> if AHP
relieved – can continue conservative tx/
operate for convergence null. If still
adapt AHP- consider Sx for RG null.

Brit. J. Ophthal. (1953) 37, 267. CAUSES AND TREATMENT OF
CONGENITAL ECCENTRIC NYSTAGMUS BY J. RINGLAND
ANDERSON Melbourne, Australia