The role of ocular movement recordings in the treatment of

Congenital Nystagmus

Orly Halachmi, Lionel KowalAlumni 17/10/11 RVEEH

Case presentation - NI

6 y o CN PHx & FHx: nil; no consanguinity c/o: AHP

NI

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

Eye movements recording:

Foveation time -L beating to R beating

Wave formAmplitudeFrequency

What is Nystagmus?

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 .

---------------------------------------------------------------------Khanna and Dell’Osso: Diagnosis and Treatment of INS. TheScientificWorldJOURNAL (2006) 6, 1385–1397

Nystagmus in Infancy

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.

CN 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).

LMLN

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.

Spasmus nutans

Spasmus nutans is a dysconjugate asymmetric high frequency Nystagmus with head nodding and tilt.

Clinical Examination

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)

Cycloplegic refraction (correct with glasses or contact

lenses).

Paradoxical pupils – only seen in some retinal

dystrophies 

Nonsurgical Management in CN

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 Management(1)

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).

Surgical Management (2)the main types of surgeries:

(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.

Surgical Management(2)

(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.

Surgical Management(3)

(3) four- horizontal rectus tenotomy_resuture procedure –recommended If there are neither convergence nor gaze nulls.

Tenotomy is thought to affect eye-muscle proprioceptives and reduce the slow-phase, damping the Nystagmus w/o altering the motor balance (*also successful in damping oscillopsia in acquired Nystagmus).

Surgical Management(4)

(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).

Surgical Management(4)

(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.

The role of eye movement recordings in NI

NI - Tx

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