12 What is Nystagmus?Nystagmus is an oscillation of the ocular motor system.It can be: pendular-no fast and slow phasesjerk-a slow phase away from the target, followed by a return saccadea combination of both .Khanna and Dell’Osso: Diagnosis and Treatment of INS. TheScientificWorldJOURNAL (2006) 6, 1385–1397
13 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.
14 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).
15 LMLNCaused 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.
16 Nystagmus Blockage Syndrome NBS is a special case of CN whereby the patient produces a purpose esotropia to either damp the Nystagmus or convert it into a low amplitude FMN
17 Spasmus nutansSpasmus nutans is a dysconjugate asymmetric high frequency Nystagmus with head nodding and tilt.
18 Clinical ExaminationA 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
19 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.
20 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).
21 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.
22 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.
23 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).
24 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).
25 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.
27 NI - TxTwo null points recorded: at RG 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.
28 Brit. J. Ophthal. (1953) 37, 267. CAUSES AND TREATMENT OF CONGENITAL ECCENTRIC NYSTAGMUS BY J. RINGLAND ANDERSON Melbourne, Australia