R. Michael Siatkowski MD Dean McGee Eye Institute University of Oklahoma

Oklahoma City, OK

No Financial Disclosure

¨  1936 ¡  Pugh: Small angle deviations different

¨  1951 ¡  Gittoes-Davis: small ET “fixation disparity” ¡  Levinge: new concept of ARC

¨  1953 ¡  Bryer: BJO letter “Flicker cases”

¨  Other observations: Lyle, Foley, Helveston, von Noorden, Epstein, Tredici

¨  Arthur Jampolsky ¡  1951: small ET and “retinal slip” ¡  1956: Phorias > tropias – NRC possible ¡  1962: bifoveation not possible despite orthoptic

therapy

¨  Marshall Parks ¡  1961: “monofixational phoria” ¡  1969: AOS thesis “The Monofixation Syndrome”

¨  Obligate characteristics: ¡  ET or XT < 8 PD (orthotropia possible) ¡  Monocular facultative suppression binocularly ¡  Good fusional vergence amplitudes ¡  Inability to convert to bifixation

¨  Variable characteristics ¡  Usually results from:

­  Prior strabismus surgery ­  Anisometropia ­  Unilateral macular lesion ­  Primary

¡  ET more common than XT ¡  Amblyopia in ¾ ¡  Large phorias ¡  Stereoacuity not better than 60 arc sec

¨  Receptive field of neuron in V1 = 2.5 degrees (4.4 PD)

¨  Adjacent neurons join fields up to 8.7 PD

¨  Develop fusion through ocular dominance columns 2 axonal lengths apart

¨  “symptomless” ¨  “…remain unchanged with increasing age.” ¨  “…static alignment state.” ¨  “Over the years their eyes remain aligned…” ¨  “…persist unchanged over the years.”

¡  Parks MM, Trans Am Ophthalmol Soc, 1969

¨  58 yo pilot ¨  h/o accom ET

¡  Glassses through teens, d/c’ed till 40s ¡  Diplopia x 1 year

¨  5 pairs glasses/CT/MRI/LP/EEG

¨  VA 20/15 OD , 20/20 OS ¨  Full ductions and versions ¨  SPCT: LET 8-10 ¨  APCT: LET 18 ¨  Stereo with prism 200 arc sec

¨  Rx: PAT: ET 25, ET’ 30 ¨  EMS ¨  ET = ET’ = 2’, stereo 80”

¨  Arthur, 1989 ¨  Shauly, 1994 ¨  Ganser, Siatkowski 1997 ¨  Siatkowski, Cobo-Lewis, 1997 ¨  Arnoldi, 2001 ¨  Hunt and Keech, 2005

¨  No definitive association between instability and amblyopia, oblique dysfunction, DSC, stereopsis—etiology of change obscure

¨  Peripheral fusion is not normal in patients with MFS, and may degrade over time, causing decompensation with a change in ocular alignment and/or diplopia.

¨  Adults with MFS by Parks criteria ¡  Stable cohort: no diplopia or change in angle ¡  Decompensated cohort: acquired diplopia with or

without a change in angle of squint ¨  Clinical variables

¡  VA, muscle balance, versions, DSC ¡  W4D, Stereo, Bangerter foil ¡  Horizontal and vertical fusion amplitudes in free

space ¡  Synoptophore: torsional fusional amplitudes, retinal

correspondence

¨  8/1/1999 – 7/31/2009 ¡  12,079 patients

ú  221 (1.84%) MFS ­  32 (14.5%) worsening angle but no diplopia ­  26 (11.8%) “decompensated” MFS with diplopia    10 exclusions (children, neuro disease, functional)    14/16 gave consent

   14 with decompensated MFS    16 age/sex matched controls with “stable” MFS

¨  No difference between groups in: ¡  Age at decompensation/Years of prior stability ¡  Glasses wear ¡  Prior patching or orthoptics ¡  Prior # of EMS ¡  Visual acuity or amblyopia ¡  Original diagnosis ¡  Refractive error

¡  Trend: age at original dx ú  Decompensated 21.5 yrs/stable 4.7 yrs (p=0.074)

¨  No difference between groups: ¡  DVD ¡  Versions ¡  Pattern ¡  Overall angle of squint ¡  Size of phorias

¨  Vertical strabismus ¡  Decompensated 50% ¡  Stable 6%

¡  P=0.018

¨  No difference between groups in: ¡  Bangerter strength ¡  Stereoacuity ¡  Bagolini responses ¡  Synoptophore fusion ¡  Retinal correspondence ¡  Vertical fusion amplitudes

ú  Although both groups increased with a mean of 4 PD for decomp and 5 PD for stable patients

¨  Mean horizontal fusion amplitudes (dist/near)

¡  Convergence ú  Decompensated 6.4 / 8.1 ú  Stable 16.9/ 20.6

   P=0.001/0.004

¡  Divergence ú  Decompensated 4.0 / 4.5 ú  Stable 9.9 / 11.3

­  P=0.049/0.10

¨  Mean cyclovertical fusional amplitudes

¡  Excyclovergence (degrees) ú  Decompensated 9.1 ú  Stable 3.3 ú  P<0.001

¡  Incyclovergence (degrees) ú  Decompensated 7.1 ú  Stable 3.1 ú  P=0.041

¨  Worth 4 dot ¡  Stable patients more likely to fuse ¡  Stable patients less likely to have diplopia ¡  Stable patients more likely to have constant, rather

than alternating, suppression

¨  No patient with decompensated MFS had normal values for all fusional amplitudes

¨  Decompensated group means: ¡  3 pairs glasses (range 0-10) ¡  3 prior exams (range 0-5) ¡  $1168 in unnecessary workup (including

neuroimaging, Tensilon test, echography)

¨  13/14 decompensated patients had rx ¡  6 surgery

ú  100% MFS angle of squint at 15 months post-op ú  Stereopsis improved only in 1/6

¡  4 orthoptic exercises ú  Stereopsis improved in 1/4

¡  3 prisms ¡  2 glasses change ¡  1 Bangerter foil occlusion

¨  9/14 diplopia free ¡  2 had recurrence several years later

ú  1 treated successfully with orthoptics ú  1 to require more surgery

¨  1/14 improved (constant to intermittent) ¨  3/14 unchanged

¡  2 constant, 1 intermittent

¨  MFS is usually static and asymptomatic ¨  14.5% of patients with MFS seen over a decade

had increase in angle and/or diplopia ¨  Decompensation risk:

¡  <5% under age 30 ¡  Approximately 10% rate of decompensation per

decade after age 40

¨  Approx 20,000 cases/yr in US ¡  1 case/month per pedi/neuro-ophthalmologist

¨  Proposed etiologies

¡  Change in refractive error ú  Presbyopia onset ú  Development of anisometropia

¡  Loss of prior suppression ¡  Amblyopia density ¡  Loss of prior bifoveation (eg X(T) to XT) ¡  Protective effect of amblyopia/stereopsis ¡  Changes in neural and/or muscular adaptation

¡  No compelling evidence for any of these

¨  Associated factors in this study:

¡  Later dx/rx of original problem ¡  Presence of a vertical strabismus ¡  Decreased horizontal fusional amplitudes ¡  Increased cyclovertical fusional amplitudes

¨  Normal Decomp Stable

¨  Conv dist 18 6.4 16.9 PD ¨  Conv near 38 8.1 20.6 PD ¨  Div dist 6 4.0 9.9 PD ¨  Div near 16 4.5 11.3 PD ¨  Vertical 2.5 3.8 5.9 PD ¨  Cyclo 6 8.0 3.2 deg

¨  1. Loss of fusional amplitudes , first at near, later at distance

¨  2. Sensory torsion + small vertical strabismus

¨  3. Compensatory increase in vertical and torsional fusional amplitudes

¨  4. System overwhelmed , leads to decompensation

¨  1. Most MFS patients remain asymptomatic over a lifetime, but 7% per decade (10% per decade > age 40) decompensate and develop diplopia, often with a worsening of alignment.

¨  2. MFS is not a static condition. Even “stable” asymptomatic MFS patients lose horizontal fusional amplitudes over time, first at near, later at distance.

¨  3. The process of decompensation follows this sequence:

¡  Loss of horizontal fusional amplitudes ¡  Development of sensory ocular torsion ¡  Adaptative increase in torsional amplitudes

ú  Possible small HT with increase in vertical amplitudes ¡  Overwhelming of adaptative mechanisms

ú  Diplopia +/- change in angle of deviation ú  Pattern squint and oblique dysfunction absent

¨  4. Prevention of decompensation may be aided by:

¡  Early dx and management of original condition ¡  Aggressive amblyopia management ¡  Routine measurement of fusional amplitudes in

asymptomatic patients ú  Institution of orthoptic exercises when amplitudes

subnormal, even if asymptomatic

¨  5. Treatment of decompensation should include:

¡  Managing refractive changes and presbyopia ¡  Avoiding fixation switch ¡  Orthoptics/prisms/surgery

ú  Surgery has 100% motor success, 75% sensory success ú  Recurrences may occur in 20% over 5 year period

¨  Lauren Pendarvis, CO ¨  William Feuer, MS ¨  Greg Skuta, MD ¨  Prior authors ¨  John T. Flynn, MD and Edward A. Jaeger, MD ¨  Rhea, Abi, Eli, and Josh Siatkowski