Nystagmus in Infancy andChildhood: Characteristics andEvidence for Treatment

Richard W. Hertle, M.D.

ABSTRACTPurpose: To discuss the common characteristics of infants and children with

nystagmus and review treatments and their evidence.Methods: The NEI-sponsored classification of eye movement abnormalities and

strabismus and a PubMed search for papers from 1995 through 2005 on interven-tions for Infantile Nystagmus Syndrome (INS) are reviewed.

Results: The review of treatments revealed 18 papers on surgical or pharmaco-logical interventions and six papers describing other interventions. There is onlyone randomized controlled trial, with all the other studies being uncontrolledtrials/case series.

Conclusions: Previous science and studies on interventions for nystagmus ininfancy and childhood have laid an important foundation for future work in thisfield, which should include a randomized clinical trial.

INTRODUCTION AND BACKGROUND

Eye care professionals are among themost common to evaluate infants and chil-dren with involuntary ocular movements.

From the Medical Center of Akron, Children's Hospital, andThe Lahoratory of Visual and Ocular Motor Physiology, Ak-ron, Ohio,

Requests for reprints should be addressed to: Richard W,Hertle, M,D,, 300 Locust St,, Ste, 490, Akron, OH 44302-1804; e-mail: rslpshot@aol,com

Presented as part of a symposium at the Joint Meeting oftheAmerican Orthoptic Council, the American Association ofCertified Orthoptists, and the American Academy of Oph-thalmology, San Francisco, CA, October 25, 2009,

producing anxiety in the medical care pro-vider as well as the family. The eye careprofessional choosing to specialize in in-fants and children may, in fact, see morepatients with nystagmus than any otherspecialist. This is due to the frequent as-sociation of nystagmus with strabismus.It may be that nystagmus gets less press(e.g., literature, teaehing, researeh, eduea-tion) beeause there is less we understandor ean do about it compared to strabismusor other childhood eye diseases.

Nystagmus comes from the Greek wordnystagmos (to nod, drowsiness) and fromnystazein (to doze), probably akin to Lithu-anian snusti (also to doze). It is a rhyth-

© 2010 Board of Regents ofthe University of Wisconsin System, American Orthoptic Journal, Volume 60, 2010, ISSN 0065-955X, E-ISSN 1553-4448

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mie, involuntary oscillation of one or botheyes.

Using the information obtained from acomplete history, physical examination,radiographie and oculographic evalua-tions over two dozen types of nystagmuswere organized and classified accordingto a National Eye Institute supportedcollaborative effort by interdisciplinarynational experts and is called the Classi-fication of Eye Movement Abnormalitiesand Strabismus (CEMAS).i Some formsof nystagmus are physiologic, whereasothers are pathologic. Although the nys-tagmus is typically described by its moreeasily observable fast (jerk) phase, thesalient clinical and pathologic feature isthe presence of a slow phase in one or bothdirections. Thus, clinical descriptions ofnystagmus are usually based on the direc-tion ofthe fast phase and termed horizon-tal, vertical, rotary, or any combination ofthese. The nystagmus may be conjugateor dysconjugate, or predominantly pendu-lar or jerky, the former referring to equalvelocity to-and-fro movement ofthe eyes,and the latter referring to the eyes movingfaster in one direction and slower in theother. Involuntary ocular oscillations con-taining only fast phases are saccadic oscil-lations and intrusions and not nystagmus(see CEMAS classification in Table 1).̂ Itis well documented that these differencesmay be difficult, if not impossible, to dif-ferentiate clinically. Recent advances ineye movement recording technology haveincreased its application in infants andchildren who have clinical disturbances ofthe ocular motor system.^

ETIOLOGY

Although the theoretical neuronal mech-anisms of nystagmus are constantly evolv-ing and beyond the scope of this paper, itis important to state that central ocularmotor control areas are either primarily

TABLE 1CEMAS CLASSIFICATION OF

NYSTAGMUS TYPES

Classification of Eye Movement Abnormalitiesand Strabismus (CEMAS) Involuntary

Ocular Oscillations

1. Peripheral Vestibular ImbalanceMeniere, Drug toxicity

2. Central Vestibular ImbalanceDownbeat, Upbeat, Drug toxicity

3. Instability of Vestibular MechanismsPeriodic Alternating Nystagmus

4. Disorders of Visual FixationVision Loss, See-Saw Nystagmus, Drugtoxicity

5. Disorders of Gaze HoldingGaze Evoked, Acquired Pendular, Drugtoxicity

6. Acquired Pendular NystagmusCentral myelin, Oculopalatal, Whipple,Drug toxicity

7. Saccadic Intrusions and OscillationsSquare Wave Jerks, Macro-saccadicoscillations, opsoclonus, nutter, pulses

8. Miscellaneous Eye MovementsSuperior Oblique Myokyriiia, Ocular motorneuromyotonia

9. Infantile Nystagmus SyndromeCongenital, motor, sensory, idiopathic,nystagmus blockage

10. Fusion Maldevelopment Nystagmus SyndromeOld "Latent, manifest latent," nystagmusblockage

11. Spasmus Nutans SyndromeWithout optic pathway gliomaWith optic pathway glioma

or secondarily responsible for generationofthe anomalous ocular motor signal(s).^Particularly controversial is the role of cor-tical motion processing in the developmentof nystagmus.* However, major supranu-clear inputs to the oculomotor system arereasonably well accepted for their role instabilization of eye movements. These in-clude the pursuit system, vestibular sys-tem, and a part of the vestibular nucleiresponsible for gaze holding called theneural integrator. ^

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TABLE 2CEMAS CRITERIA FOR INFANTILE NYSTAGMUS SYNDROME

INFANTILE NYSTAGMUS SYNDROME (INS)Disease Name [previously Old Congenital Nystagmus and "Motor and Sensory" Nystagmus]

Criteria

Common AssociatedFindings

General Comments

Infantile onset, ocular motor recordings show diagnostic (accelerating) slow phases

Conjugate, horizontal-torsional, increases with fixation attempt, progression frompendular to jerk, family history often positive, constant, conjugate, with or withoutassociated sensory system deficits (e.g., alhinism, achromatopsia), associatedstrahismus or refractive error, decreases with convergence, null and neutral zonespresent, associated head posture or head shaking, may exhihit a "latent" component,"reversal" with OKN stimulus, or (a)periodicity to the oscillation. Candidates onChromosome X and 6. May decrease with induced convergence, increased fusion,extraocular muscle surgery, contact lenses, and sedation.

Waveforms may change in early infancy, head posture usually evident by 4 years ofage. Vision prognosis dependent on integrity of sensory system.

CLINICAL FEATURES OF NYSTAGMUSIN INFANCY AND CHILDHOOD

Neonatal and Early Infantile Nystagmus

Distinguishing aequired from the benignneonatal/infantile forms of nystagmus isimportant because of the implication forunderlying neurologic disease in acquirednystagmus. Essentially, any pattern ofnystagmus with onset in the first month oflife could be eonsidered eongenital and be-nign. However, the term "CN" has becomesynonymous with the most common formof neonatal nystagmus characterized hyan accelerating slow phase on electronys-tagmography. We will replace the term CNwith Infantile Nystagmus Syndrome (INS)different from the historically accepted no-menclature. "̂̂

In general, a clearly documented historyof onset of any form of nystagmus in thefirst months of life should put the exam-iner at ease. Unfortunately, such historyis not usually available since neonatalonset nystagmus is frequently not noticeduntil later in life. However, two forms ofneonatal nystagmus, INS and latent/FDN(Fusion-Defect Nystagmus), are so typicalthat they can be assumed to have begun inthe neonatal period. All other forms of nys-

tagmus should be assumed to have beenacquired, unless there is clear documenta-tion of their neonatal onset.

Infantile Nystagmus SyndromeINS (Previously Congenital "Motor"Nystagmus or "CN")

Familiarity with the clinieal features ofINS is essential (Table 2). INS is an oeularmotor disorder of unknown etiology thatpresents at birth or early infancy and isclinically characterized by involuntaryoscillations of the eyes. They are usuallyhorizontal with a small torsional compo-nent and may (rarely) have a vertical com-ponent. Other clinical characteristics, withvariable association, include: increased in-tensity with fixation and decreased withsleep or inattention; variable intensity indifferent positions of gaze (usually about anull position); changing direction in differ-ent positions of gaze (about a neutral posi-tion); decreased intensity (damping) withconvergence; anomalous head posturing;strahismus; and the inereased ineidenee ofsignifieant refraetive errors. INS can occurin assoeiation with congenital or acquireddefects in the visual sensory system (e.g.,albinism, achromatopsia, and congenitalcataracts). The cause and precise mecha-

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nism of INS has not heen elueidated. Chil-dren with this eondition frequently presentwith a head turn, whieh is used to maintainthe eyes in the position of gaze of the nullpoint (point of minimum nystagmus). Thisis partieularly prominent when the childis concentrating on a distant objeet, sineethis form of nystagmus tends to worsenwith attempted fixation. The head turn isan attempt to stabilize the image underthese eonditions.®"®

Head oseillations are common in INS,but are not used as the strategy to improvevision, except in those rare patients withabnormal gain of their vestihulo-ocularrefiex. Head oscillations in most patientswith INS probably reflect underlying in-stability of cervical motor control. ̂

Oscillopsia is almost never present inINS. The reason for this is unclear, butmay be explained by efference copy mech-anisms. Absence of oscillopsia is usuallynot helpful in distinguishing congenitalfrom acquired nystagmus, since even withacquired nystagmus in infancy or earlyehildhood, suppression of oseillopsia eanoeeur.

Fusion Defect Nystagmus (FDN)(Previously Called Latent /ManifestLatent Nystagmus)

Fusion defeet nystagmus (FDN) is a be-nign, jerk nystagmus that begins in earlyinfaney and is easily observed under mon-oeular viewing eonditions. It is bilateraland eonjugate, with the slow phase towardthe covered eye and the fast phase towardthe viewing or suppressed eye. Strahismus,usually in the form of esotropia, is almostalways present. It may be difficult to dis-tinguish from INS since patients with INS,esotropia and a latent component will ap-pear clinically identical to patients withFDN. The only sure way to diagnose FDNis by ocular motor recordings. FDN pa-tients have slow phases that are predomi-nantly deereasing veloeity and linear.'̂ ^

Spasmus Nutans (SN)

Spasmus nutans (Table 3) is the thirdmost common nonaequired oseillation be-ginning in infancy and consisting of highfrequency, small amplitude, dyseonjugateoseillations, a head nodding oscillation anda head tilt. This usually becomes less no-ticeable as the infant becomes a toddler.Unlike INS, the head nodding may resultin improvement of vision and decrease inthe nystagmus. The reason for this is un-clear. The characteristic feature of spas-mus nutans is the very fine, rapid pen-dular nature of the nystagmus. The eyesappear to have a shimmering movement.It may be horizontal, vertical, or torsional,and is usually asymmetric to the point thatit may appear unilateral. Pure unilateralforms are not uncommon. It may appearto switch eyes with ehanges in direetion ofgaze, and frequently appears worse in theabdueting eye. Tremendous asymmetry isassoeiated with amblyopia of the more in-volved eye."

Spasmus nutans may be a completelybenign condition with onset in infancyand resolution within two years. However,tumors of the diencephalon can eause acondition indistinguishable from spasmusnutans. Consequently, neuroimaging orcareful monitoring for visual, neurological,or endocrinological decline is essential. Anintraeranial tumor should be strongly sus-peeted in any ehild who develops spasmusnutans after three years of age.

TREATMENTS

There are a number of signs and symp-toms due to nystagmus that are amenableto treatment. The first and most obviousis deereased vision (central visual acuity,gaze-angle acuity, near acuity). Correetionof signifieant refraetive errors in ehildrenwith nystagmus is the single most power-ful therapeutie intervention for improvingvision and visual funetion in these pa-

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Disease Name

TABLE 3CEMAS CRITERIA FOR SPASMUS NUTANS NYSTAGMUS SYNDROME

SPASMUS NUTANS SYNDROME (SNS)

Criteria

Common Associated

Findings

General Comments

Infantile onset, variable conjugacy, small frequency, low amplitude oscillation,abnormal head posture and head oscillation, improves ("disappears") duringchildhood. Normal MRI/CT Scan of visual pathways. Ocular Motility Recordings—high frequency (>10 Hz), asymmetric, variable conjugacy, pendular oscillations.Dysconjugate, asymmetric, multiplanar, family history of strabismus, may be greaterin one (aBDucting) eye, constant, head posture/oscillation (horizontal or vertical),usually no associated sensory system deficits may have associated strabismus andamblyopia, may increase with convergence, head bobbing, head posture may becompensatory. Normal fundus exam Decreases with increased fusion (binocularfunction).Usually spontaneously remits clinically in 2-8 years, remains present with eyemovement recordings.

TABLE 4CEMAS CRITERIA FOR FUSION MALDEVELOPMENT NYSTAGMUS SYNDROME

Disease Name FUSION MALDEVELOPMENT NYSTAGMUS SYNDROME (FMNS)[previously Old Latent/Manifest Latent Nystagmus]

Criteria

Common AssociatedFindings

General Comments

Infantile onset, associated strabismus, ocular motor recordings show two types ofslow phases (linear and decelerating) plus high-frequency, low amplitude pendularnystagmus (dual-jerk waveform), jerk in direction of fixing eye.

Conjugate, horizontal, uniplanar, usually no associated sensory system deficits(e.g., albinism, achromatopsia), may change with exaggerated convergence("blockage"), head posture associated with fixing eye in adduction, no head shaking,may exhibit "reversal" with OKN stimulus, no (a)periodicity to the oscillation.Dissociated strabismus may be present. Decreases with increased fusion (binocularfunction).

Intensity decreases with age.

tients. Refractive etiologies of decreasedvision include either one or a combinationof conditions—e.g., myopia, hyperopia,astigmatism, and anisometropia. Theserefractive conditions can contribute sig-nificantly to already impaired vision inpatients with other organic etiologies ofdecreased vision—e.g., amblyopia, opticnerve and/or retinal disease, oscillopsia,and the oscillation itself. The second isanomalous head posturing (AHP). Theetiology of the AHP includes: a gaze nulldue to INS or acquired nystagmus (e.g.,chin-down in down-beat nystagmus), anadduction null due to FMNS (manifest

strabismus with the preferred eye fixingin adduction) (Table 4), convergence damp-ing due to INS (nystagmus blockage), anda periodically changing head posture dueto periodic alternating nystagmus. Thethird is oscillopsia, which is usually due toeither acquired nystagmus or a change inthe sensory/motor status of patient withINS (e.g., decompensated strabismus, achange in the gaze null angle or decreas-ing acuity). Other less common associatedsigns and symptoms include hypoaccom-modation (can be associated with acquirednystagmus and/or INS) and photophobia(INS associated with the congenital cone

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TABLE 5MEDICAL TREATMENT OF NYSTAGMUS

NYSTAGMUS TYPE TREATMENT

Infantile Nystagmus Syndrome

Acquired Pendular Nystagmus

Peripheral VestibularDownbeatUpbeatPeriodic AlternatingSee-SawSaccadic Intrusions/OscillationsSuperior Oblique MyokymiaOpsoclonusOcular Motor NeuromyotoniaVoluntary Ocular FlutterChronic Internuclear

Ophthalmoplegia

Fresnel Prisms, Orthoptics, Gabapentin, Baclofen, Biofeedback,AcupunctureFresnel Prisms, Orthoptics, Gabapentin, Baclofen, Clonazepam, Cannabis,Alcohol, Carbamazepine, 5-Hydroxytryptophan, Scopolamine, Memantine,BotoxPositional Exercises, Betahistine, Cinnarizine, Acetazolamide3,4 Diaminopyridine, Clonazepam, GabapentinBaclofen, Clonazepam, GabapentinBaclofen, BotoxBaclofenBaclofen, Propanolol, ClonazepamCarbamazepine, Propanolol, TimololCorticosteroids, Propanolol, Clonazepam, BaclofenCarbamazepinePrism, OrthopticsPrism, Orthoptics

dystrophy's and albinism). General treat-ment medical and surgical indications andguidelines are outlined in Tables 5-7.

REVIEW OF LITERATURE

A PubMed''"'̂ search was carried out forthe keywords: congenital nystagmus orearly onset nystagmus or infantile nys-tagmus combined with treatment or ther-apy or intervention or trial. The searchrevealed 18 studies published after 1994of surgieal or pharmaeologieal interven-tions, all of which are uncontrolled caseseries. There were also six studies pub-lished after 1994 of other interventions,all of which were uncontrolled case seriesexcept for one randomized controlled trial.The improvement in visual acuity in thegroup receiving the experimental treat-ment from the first to the last visual acu-ity assessment was small (0.033 logMARunits), although this did reach significancewith a paired t-test.

It is readily acknowledged that some ofthe improvements obtained in studies inTables 7 and 8 are impressive. There isconsiderable face validity to some of the

treatments (eye muscle surgery for abnor-mal head positions). Some have used so-phisticated measures of ocular motor andvisual function and some have gone to con-siderable lengths to make measurementsas objective as possible, and to minimizeplacebo effect. One study demonstratedan improvement in nystagmoid eye move-ments in an individual with soft contactlenses and showed that the improvementwas negated by topical anaesthetic, im-plicating a role for tactile feedback. Theonly randomized controlled trial (RCT) ofa nystagmus intervention that the pres-ent review discovered had modest samplesize and did not measure ocular motorvariables. One of the reasons why RCTsare considered so important in evidence-based healthcare is beeause they eontrolfor the plaeebo effeet. People with INS maybe partieularly prone to the plaeebo eifeetbeeause they are highly motivated, andaneedotal reports suggest that their vi-sual aeuity and nystagmus are worse whenthey are under stress and so may improvewith repeated measurements as patientsbeeome more relaxed in the researeh elinie.The plaeebo effeet influences objective re-

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TABLE 6NYSTAGMUS SURGICAL PROCEDURES

Operation 1—Induced Convergence (Artificial Divergence)

IndicationBinocular function (stereopsis) with observable convergence damping

PreparationPrism adapt with 7 BO each eye, not Fresnel

TechniqueBilateral medial rectus recess and bilateral lateral rectus tenotomy -i- reattachment

Operation 2—Eccentric Horizontal Null Position Alone

IndicationClinically observable eccentric gaze null with head posture in opposite direction

PreparationRule out Aperiodic or periodic infantile subtype, no changing posture over 10 minutes of observation.

TechniqueRecess lateral rectus 10.0 in the abducted eye and medial rectus 7.0 in the adducted eye with tenotomies andreattachment of other horizontal recti for turns up to 20°.Recess lateral rectus 10.0 in the abducted eye and medial rectus 7.0 in the adducted eye 10.0 and resect the medialrectus 7.0 in the abducted eye and resect the lateral rectus 11.0 in the adducted eye for turns greater than 20°

Operation 3—Torsional Head Posture

IndicationTorsional head posture alone

PreparationRule out aperiodic or periodic infantile subtype, no changing posture over 10 minutes of observation

TechniqueHorizontal transposition of vertical recti one full tendon width

Operation 4—Chin Up Head Posture

IndicationChin-up head posture alone, nystagmus changes intensity in up-gaze

PreparationRule out aperiodic or periodic infantile subtype, no changing posture over 10 minutes of observation

TechniqueBilateral superior oblique 5.0 mm tenectomy + bilateral inferior rectus 4.0 recessions

Operation 5—Chin Down Head Posture

IndicationChin-down head posture alone, nystagmus changes intensity in down-gaze

PreparationRule out aperiodic or periodic infantile subtype, no change posture over 10 minutes

TechniqueBilateral inferior oblique myectomy plus bilateral superior rectus 4.0 recessions

Operation 6—Head Posture—Nystagmus—Strabismus

IndicationHead posture plus strabismus

PreparationRule out aperiodic or periodic infantile subtype or esotropia with adduction null, i.e., no changing posture over 10minutes of observation. Determine fixing eye (eye driving the head posture)

TechniqueStraighten the head with prism correction over the preferred eye, neutralize the resulting strabismic deviation withprism over the nonpreferred eye. Perform bilateral recess/resect on each eye's respective measured prism correction

{continued)

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TABLE 6 (continued)

Operation 7—Multiplanar Head Posture

IndicationCombination chin-up/down and face turn

PreparationRule out aperiodic or periodic infantile subtype or esotropia with adduction null, i.e., no changing posture over 10minutes of observation

TechniqueThree muscles each eye. Combine respective oblique plus vertical recti (above) for chin-up/down with 10.0 recess oflateral rectus of abducting eye and 7.0 recess of medial rectus of adducting eye

Operation 8—Nystagmus and Strabismus

IndicationNystagmus and horizontal strabismus with no head posture

PreparationTreat refractive errors

TechniqueRecess/resect of all four horizontal recti for the total deviation or bilateral recess for the total deviation + tenotomyon the remaining two horizontal recti

Operation 9—Nystagmus Alone

IndicationINS witb or without periodicity and no strabismus, static anomalous bead posture or fusion with convergencedamping

PreparationRule out strabismus, static head posture or convergence damping

TkchniqueBilateral horizontal recti tenotomy witb reattachment or bilateral horizontal rectus recess (lateral recti recess 10 to12, bilateral medial recess 8 to 10)

TABLE 7MEDICAL-SURGICAL INTERVENTION 1995-2005

Authors Year Type of study Surgery & Pharmacological Outcome

Carruthers'^

Gradstein,Reinecke,Wizov,Goldstein"

Dell'Osso,Hertle,Williams,Jacobs"

Graf,Droutsas,Kaufmann'^

Lee, Lee, Kim,Lew,

GraP'

1995 Case series

1997

1999

Case seriesN = 9CongenitalPAN

Case studyN=l ,canine

2000 Case seriesN = 34

2000 Case seriesN = 63

2002 Case seriesN = 78

BotoxN = 4

3 prior Kestenbaum procedures,5 recessions of horizontal recti,1 had Baclofen

Severed & re-attached thetendons of the extra-ocularmuscles

Kestenbaum surgery forhorizontal HT

Mod. Kestenbaum surgery (HT),var3dng degrees, follow up > 5 m

Kestenbaum (N = 31)Artificial divergence (N = 27)Combined (N = 20)

VA t i n 3/4

Kestenbaum: VA unchangedRec.:AHP& VA Tall casesBaclofen: unsuccessful

Immediate & persistentvisible, behavioural, & EOGeffects

Long-term dose/responseeffect of 1.5°/mm

Mean pre-op HT 32°Mean post-op HT 5°

HT i from 30° to 10°HT i from 30° to 5°HT i from 30° to 7°

{continued)

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TABLE 7 (continued)

Authors

Hertle, Maybodi,Mellow, Yang^'

Wong,Tychsen'"

Alio, Chipont,Mulet,U G ÍJSL irloz

Hertle,DeirOsso,GitzGihbon,Thompson,Yang, Mellow^'

Kose, Egrilmez,Uretmen,Celehisoy,

Miura, Hertle,FitzGibbon,

Miura, Hertle,FitzGibbon,Optican^''

Cao, Xin,Wang, Wang,Zhang, Liu

Erhagci,Gungor,

Hertle,Dell'Osso,FitzGibbon,Yang, Mellow^'

Hertle,Anninger,Yang, HilP«

Oleszczynska-

Year

2002

2002

2003

2003

2003

2003

2003

2004

2004

2004

2004

2004

Type of study

Case studyN = l

Case seriesN = 2,macaque

Case seriesN = 42

Case seriesN=10

Case seriesN = 12

Case seriesN = 8

Case seriesN = 8

Case seriesN = 21

Case seriesN = 7

Case seriesN = 5

Case seriesN = 15

Case seriesN = 32

Surgery & Pharmacological

Anti-anorexic drug(diethylproprionate)

Severed & re-attached thetendons of the extra-ocularmuscles

Extensive recessions of the 4horizontal rectus muscles

Horizontal rectus tenotomyFollowed-up after lyr+

Retroequatorial recession ofall 4 horizontal rectiFollow-up ranged 6-26 months

Horizontal rectus tenotomyWavelet spectral analysis

Horizontal rectus tenotomyDynamical systems analysis

Parks shift of neutral zone

Large recessions of 4horizontal recti

Simple tenotomy of all 4horizontal recti withreattachment at originalinsertion

Various surgery on all 4horizontal recti

Botox

Outcome

T foveationbroadened null zoneVA 20/70 to 20/50

Velocity & intensity T in 2/2VA i 20%

HT i in all cases21% T by 0.2 logMARConsecutive XOT 3 cases

Mean foveation times T in 9/10VA Tin 5/10NEI-VFQ-25 T in 9/10

Amplitude & intensity I sigin all patientsVA Tin 10/12Improvements post-op

None, or minimal, effect onwaveform structure

None, or minimal, effect onunderlying mechanisms of theCN beats

Nystagmus iVA T 2-5 linesHT i in all cases

VA T in 5/7In 5 with HT, HT & intensity i

1 yr post-op, 2/3 hadpersistent significant T inNAFX & foveation timesVA T in 4/5

VA T > 0.1 LogMAR in 14/15HTTNystagmus i

Amplitude i in 29-50%VA T in all casesHTT

Table 7: Summary of papers describing surgical and pharmacological interventions for INS from 1995-2005.VA, visual acuity; T, improvement or increase; i , worsening or decrease; EOG, electro-oculograph; Mod.,modified; XOT, exotropia; NEI-VFQ-25, National Eye Institute Visual Function Questionnaire; HT, head turn;PAN, periodic alternating nystagmus; NAFX, nystagmus acuity function.

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TABLE 8NON-MEDICAL/SURGICAL INTERVENTIONS 1995-2005

Authors

Sheth, Dell'Osso,Leigh, et al. •'"'

Leung, Wick,Bedell ̂ i

Blekher,Yamada,Yee, AbeP2

Evans, Evans,Jordabl-Moroz,Nabee-"

Sharma,Tandon, Kumar,Anand^"

Biousse, Tusa,Russell, et al.'*''

Year

1995

1996N = 6

1998N = 6

1998

2000

2004

TVpe of study

Case seriesN = 13

Case series

Case series

RCTN = 38

Case seriesN=10

Case seriesN = 4

Therapy

Somatosensory stimulation(vibration or electrical) toforehead or neck

Variety of treatments, includingrefraction, contact lenses,IPS, biofeedback

Acupuncture ofsternocleidomastoids

IPS & visual (after-image)visual biofeedback

Auditory biofeedback

Contact lenses (CL)

Outcome

Positive effects in 9, of 8 testedwith Snellen VA, 5 T by 1-4letters

VAT by 0-3 lines

4/6 T foveation

No significant treatment effect:placebo group î as much asexperimental group

Amplitude & intensity iduring treatment, did notpersist. No objective effect onVAorCS.

No change in nystagmus, butpreferred CL to specs. SuggestCL better optical correctionrather than dampennystagmus

Table 8: Summary of papers describing nonmedical and nonsurgical interventions for INS since 1995.VA, visual acuity; T, improvement or increase; 4-, worsening or decrease; IPS, intermittent photic stimulation;CS, contrast sensitivity; CL, contact lenses.

sponses and is not strongly related to intel-ligence, suggestibility, or personality. Evensurgical interventions are prone to placeboeffects.

The studies reviewed in Tables 7 and 8are important, representing a good startfor the highest level of evidence basedtreatments. It is suggested that the nextstage in the investigation of interventionsfor INS is to carry out RCTs. RCTs willprobably have to be collaborative in orderto obtain adequate sample sizes. Clearly,it would be unethical to give patients aplacebo surgical intervention that wasknown to be ineffective. Many objectiveand subjective visual and electrophysi-ological variables or outcome measuresimprove as a result of intervention in pa-tients with INS, suggesting that neuro vi-sual changes take place as a result of the

intervention itself. Taken as a whole thescience of nystagmus research has affir-matively answered the question. Can wechange the nystagmus? This is not an endbut, rather, another larger beginning.

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Key words: infantile nystagmus, treat-ment, eye muscle surgery

58 Volume 60, 2010

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