ACTIVE TREATMENT OF CONGENITAL NYSTAGMUS: RATIONALE & RESULTS

1. Squint Club 2006

2. ACTIVE TREATMENT OFCONGENITAL NYSTAGMUS:RATIONALE & RESULTS LIONEL KOWAL LOTS of assistance from Drs Elaine Wong, Steven Bush, Joanne Dondey & Larry Abel SQUINT CLUB 2006

3. OVERVIEW OF THIS TALK • 1. Overview of cong N • 2. Treatments • 3. Audit of recordings • 4. Audit of surgeries Squint Club 2006

4. APOGOLIES FOR DIFFICLUT TERNIMOLOGY • Congenital Aperiodic Periodic Alternating Nystagmus  PAN • Latent Manifest Latent Nystagmus  LMLN, aka Fusion Maldevelopment Syndrome or FMS • Dual Jerk nystagmus : Not a personal insult - combination pendular plus jerk nystagmus Nystagmus usu referred to as N Squint Club 2006

5. IN OFFICE ASSESSMENT OF CONGENITAL NYSTAGMUS Types of congenital nystagmus - how to differentiate them in the office

6. 2 Main types of congenital N: Lower case ‘cN’ = congenital N = any sort of very early onset N 1.Congenital N Upper case ‘CN’ - a specific type of cN Synonyms: Congenital Motor N Idiopathic Infantile N IIN

7. 2 Main types of congenital N: 2. LMLN Latent Manifest Latent N Synonyms: Manifest Latent N Fusion Maldevelopment N FMNS

8. Congenital N • Result of abnormal bilateral symmetric acuity development @ a CRITICAL PERIOD in very early visual devpt. • Hence frequent association with : OCA [foveal ± disc dys- / hypo-plasia], high refractive errors, bilateral optic n hypoplasia, PVL, bilateral cong cataracts, ….. Squint Club 2006

9. LMLN • Result of Asymmetric acuity development and/or abnormal development of binocularity @ a CRITICAL PERIOD in very early visual devpt hence associated with CET, early monocular visual loss, PVL, … Squint Club 2006

10. CN • Involuntary, bilateral, conjugate [RE = LE] oscillation beginning ≤ 6 mo • Usually horizontal ± torsional • Decreased at certain angle[s] = null zone NZ • Blocked with convergence [also NZ] Squint Club 2006

11. CN Commonly gaze evoked: • R beating in R gaze • actually to R of NZ • L beating in L gaze • actually to L of NZ Usual CN waveform [decreasing velocity slow phase] is UNIQUE Squint Club 2006

12. Acuity in CN : FOVEATION When eye changes direction, speed of oscillation slows down in order to reverse direction = foveation period [velocity < 5 º/sec; flat part of the EMR] Squint Club 2006

13. Acuity in CN : FOVEATION • BCVA depends on: • Duration of foveation period • Persistence and effect of factors that initiated the CN [foveal hypoplasia, optic n hypoplasia, high cyls, …] Squint Club 2006

14. CN: 2 NZs LITTLE / NO N • ECCENTRIC NZ : drives AHP • Usu stable / ‘hard wired’ • but can vary time / age • Can be turn, tip, tilt [T3] or combo. • Same with either eye fixing • CONVERGENCE NZ • near acuity better than distance • medial recti ‘brake’ the CN Squint Club 2006

15. CN Natural history: 3 phases over the first 12mo Phase I : first 2-3 mo of life • Purposeless eye mvmts - as if blind • No jerk N • large amp, low frequency ‘triangular’ • No voluntary horizontal pursuit / saccades • Normal vertical OKN, pursuit and saccades - excludes apparent blindness & avoids MRI Squint Club 2006

16. Natural history : Phase II pendular Age 6-12 mo Symmetrical, low-amplitude, pendular N May remain phase II without proceeding to phase III Squint Club 2006

17. Natural history: Phase III adult waveform • Age 12+ mo • ‘Adult’ jerk waveform • development of eccentric null zone with AHP • ± compensatory head nodding • Phases are per Reinecke • Hertle does not show same evolution • Difference: ?sampling ?selection bias Squint Club 2006

18. CN variant : P A N • Relatively common • VERY under diagnosed • Melbourne: ?30% of albinos • FAT SCAN IMPORTANT - are there ANY photos that shows a face turn the other way? Squint Club 2006

19. CN variant : P A N • Oscillates between 2 NZs approx 90° apart • O/wise identical to CN • NZ changes : cycle of 1 to 10 min Acquired PAN : cycle usu 2 min • Usu Aperiodic e.g. 8 min to L & 1 min to R Squint Club 2006

20. Latent Manifest Latent Nystagmus LMLN • Main EMR feature: Decreasing velocity slow phase [not unique - also gaze paretic N] Squint Club 2006

21. Latent Manifest Latent N LMLN • Main clinical feature: Fast phase to fixing eye - UNIQUE LMLN : is a conjugate bilateral monocularly ‘driven’ N - waveform depends on which eye is fixing, and whether that eye is in the AD- or AB- ducted position Slit lamp: T component common Squint Club 2006

22. LMLN can resemble CN Null in adduction for each eye [less N, vision better] - can look like CN conv null Nystagmus on lateral gaze: • LE in LG: BE have N  L • RE in RG: BE have N  R SUPERFICIALLY SIMILAR TO GAZE EVOKED N OF CN Squint Club 2006

23. LMLN Face turn to fixing eye • 2 NZs improve VA:H & Thence 2 types of AHP • NZs in LMLN are monocular • NZ for blocking the H component of LMLN: fixation in adduction • Medial rectus acts as a ‘brake’ • Face turn to fixing eye - can superficially resemble PAN Squint Club 2006

24. LMLN Head tilt to fixing eye • NZ for blocking T component of LMLN : in intorsion • sup oblique acts as a ‘brake’ Head tilt to fixing eye Same mechanism causes DVD of other eye Squint Club 2006

25. CN / PAN & LMLN • RECAP …. Squint Club 2006

26. Congenital N • Result of abnormal bilateral symmetric acuity development Squint Club 2006

27. WHY LMLN? • Result of Asymmetric acuity development &/or abnormal development of binocularity • BOTH LMLN & CN seen together in very early onset Cong ET Squint Club 2006

28. Both CN & LMLN may have: • N greater in lateral gaze • Latent component N worse with monocular cf binocular fixation different mechanisms in CN / LMLN • Strabismus CN: some. LN: nearly all Squint Club 2006

29. Both CN/PAN & LMLN may have: • Conv null different mechanisms • Alternating face turns different mechanisms Squint Club 2006

30. CN vs. LMLNIN OFFICE GUIDELINES • T: prob LMLN • OCA :  bilateral VA  CN • N  fixing eye: LMLN Squint Club 2006

31. CN vs. LMLNIN OFFICE GUIDELINES 2 • Pref for fixation in ABduction : CN • Smooth pursuit asymmetry: LMLN Squint Club 2006

32. P A N • Prolonged in- office exam - check AHP while talking to parents for PAN [show age appropriate DVD] • FAT scan to determine consistency Squint Club 2006

33. SLIT LAMP EXAM • Look for TIDs of iris with decentred beam in a darkened room • Makes OCA likely • Hermansky Pudlak looks just like OCA : ask re: any possible bleeding diathesis Squint Club 2006

34. SLIT LAMP EXAM • The ‘Designs for Vision’ examination paddle with reduced Snellen chart is a good way to • determine conv null • any T component [usu LMLN] • fast phase to fixing eye • Smooth pursuit asymmetry [usu accompanies LMLN] Squint Club 2006

35. When to record and why record eye movements for nystagmus diagnosis?

36. Does everyone with wiggly eyes need to be recorded? • Usually - not if you’re absolutely certain about the diagnosis and have all the information you need for management • EMR is to cN today what ECG was to arrhythmia 50 y ago - would you dream of managing an arrhythmia without ECG? Squint Club 2006

37. What if you’re not sure? • CN waveforms are unique - can confirm diagnosis Can save patient expensive imaging studies (esp. small children) Squint Club 2006

38. What if you’re not sure? • What distinctions can you make? • Acquired vs. cong types N • CN vs. cong PAN • CN vs. LMLN • N vs. saccadic oscillations Squint Club 2006

39. CN waveforms • Pathognomonic for CN • Approx 15 waveforms described • ‘Jerk’ or ‘pendular’ on basis of slow component Jerk waveforms may appear pendular clinically • Analysis of waveform may  prognostic information about potential VA Squint Club 2006

40. Latent nystagmus • EMR often required to determine whether LN is due to CN or LMLN • “The eye is quicker than the eye” Squint Club 2006

41. Assessing effects of treating CN • CN’s variability makes clinical assessment of change difficult • Recording can objectively document • Changes in foveation • Can facilitate better VA • Shift in null position • Will reduce or eliminate AHP • Broadening of null • having best possible vision over a wider range of gaze angles improves patients’ functionalfield of vision …all best demonstrated with EMR Squint Club 2006

42. Summary • EMR can provide clinicians with two major forms of assistance: • 1) establishing / confirming a diagnosis when the clinical presentation is atypical or ambiguous • 2) Document outcome of treatment Squint Club 2006

43. Modern Treatment Options In congenital Nystagmus

44. Directly Improve VA Treat refractive error Treat amblyopia Stabilize/ reduce intensity N (increase “foveation”) to improve VA Prisms CLs Surgery Treatment goals in CN 1 Squint Club 2006

45. Normalize head posture Prisms Surgery Broaden NZ to expand effective visual field Prisms CLs Surgery Treatment goals in CN 2 Squint Club 2006

46. Drugs - barely explored New epilepsy drugs Lyrica, Memantine, Neurontin Medical treatments Squint Club 2006

47. Prisms - for convergence null • Induce fusional convergence • 7 ∆ base out prisms with -1 DS OU to compensate for convergence induced accommodation [CA/C ratio] • Can be used long term • Useful preop test for suitability for artificial divergence surgery Squint Club 2006

48. Contact lenses •  VA ≥ optical effect alone • CL sometimes expands NZ & improves foveation time • ? Stimulates conjunctival proprioceptors Dell’Osso 1988. Contact lenses and congenital nystagmus. Clin. Vision. Sci. 3:229-232 Squint Club 2006

49. #1: ARTIFICIAL DIVERGENCE #2: KESTENBAUM / ANDERSON #3: HERTLE TENOTOMY #3A: 4 MUSCLE RECESSION #4: LMLN SURGERY Surgical treatments Squint Club 2006

50. #1: ARTIFICIAL DIVERGENCE SURGERY • Cuppers,1970’s. Popularised by Spielman 1990’s. >100 cases to AAPOS 10y ago • If there is a conv null for distance with ∆, BMR creates an exophoria that ‘drives’ a conv null • INDICATIONS • CN / PAN • Convergence null for distance • Some sensory and motor fusion or BMR  constant XT Squint Club 2006