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