Control of intermittent exotropia should be assessed with: Control of intermittent exotropia should be assessed with


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Control of intermittent exotropia should be assessed with:



The current evidence suggests



5 year-old boy

  • 5 year-old boy

  • Hx - “left eye wanders particularly when tired or at end of day”

  • VA 20/20 20/20

  • Full ductions

  • D 25 X(T) comitant

  • N 25 X(T)

  • SLE Fundus Normal

  • Cret +0.50 R +0.50 L





Observe

  • Observe

  • Alternate patching e.g. 3hrs/day

  • (? Anti-suppression therapy)

  • Convergence exercises

  • Surgery



Overminus spectacles e.g. adding -2.50 sphere to each spectacle lens

  • Overminus spectacles e.g. adding -2.50 sphere to each spectacle lens

  • E.g. Cret -1.00 sph R -1.00 sph L

  • Overminus Rx -3.50 sph R -3.50 sph L

  • E.g. Cret +1.00 sph R +1.00 sph L

  • Overminus Rx -1.50 sph R -1.50 sph L



Overminus stimulates accommodation which then stimulates convergence

  • Overminus stimulates accommodation which then stimulates convergence

  • (therefore high AC/A ratio may be beneficial)

  • Fusional vergence stimulates accommodation

  • (we have a CA/A ratio)

  • accommodation blurs distance VA requiring overminus for clarity



Small case series

  • Small case series

  • Differing amounts of overminus (-0.50 to -5.00)

  • Differing methods of prescription (fixed versus titrated to control of IXT)

  • No control groups

  • No standardized outcome assessment

  • No masking of outcome assessment









Angle of deviation?

  • Angle of deviation?



Proportion of the time the eyes are manifestly exotropic



Proportion of the time the eyes are manifestly exotropic

  • Proportion of the time the eyes are manifestly exotropic

  • Ease of recovery when dissociated





Constant exotropia – Grade 5

  • Constant exotropia – Grade 5

  • Exotropia > 50% of 30 seconds before dissociation – Grade 4

  • Exotropia < 50% of 30 seconds before dissociation – Grade 3

  • Score distance and near fixation separately















To assess initial short-term response to overminus treatment

  • To assess initial short-term response to overminus treatment

  • Compare:

  • Study group mean of distance IXT control scores (primary outcome)*

  • Proportion of patients with improvement >=1 point in distance IXT control score*

  • Adverse symptoms, near VA, & compliance

  • *The distance IXT control score is the mean of 3 control tests at the visit.



Age: 3 to <7 years

  • Age: 3 to <7 years

  • IXT

    • Distance control score ≥ 2 (mean of 3)
    • Near control score ≠ 5 (mean of 3)
    • ≥ 15∆ exo at distance by PACT
    • Near deviation does not exceed distance deviation by >10 ∆ on PACT


No previous strabismus surgery

  • No previous strabismus surgery

  • No previous substantial overminus (>=1.00D)

  • No non-surgical treatment for IXT within past 6 months (other than refractive correction)

  • SE in both eyes between +1.00 and -6.00 inclusive

  • No ADHD drugs or other drugs known to affect accommodation

  • Wearing appropriate correction for ≥1wk if refractive error meets certain criteria





58 patients enrolled at 21 sites

  • 58 patients enrolled at 21 sites

  • We planned 50 patients, knowing that we would have 88% power to detect a 0.75 pt difference with a SD of 0.926 (1-sided test with alpha of 0.05)

  • 58 patients enrolled and randomized (1:1) to:

  • Observation (N=31)

      • Non-overminus spectacles or no spectacles (if correction not needed)
  • Overminus (N=27)

      • Spectacles with 2.50D overminus


































































Pilot study, small sample size

  • Pilot study, small sample size

  • Generalizable only to children 3 to 7 yrs with similar characteristics

      • Includes hyperopia only up to +1.00 D
      • We don’t know if works over wider range of refractive error
  • Likely overestimated % with response

      • 1-line of control improvement within test-retest. Expected ~20% to ‘respond’ by chance alone.


Overminus spectacles improve distance control (after 8 weeks)

  • Overminus spectacles improve distance control (after 8 weeks)

  • Overminus spectacles appear to improve distance control particularly well in patients with very poor control (with a control score of 4 to 5)









Control of intermittent exotropia should be assessed with:

  • Control of intermittent exotropia should be assessed with:

  • Standardized timing of the tropic phase

  • Prism and alternate cover test

  • Near stereoacuity

  • Standardized assessment on the synoptophore



Control of intermittent exotropia should be assessed with:

  • Control of intermittent exotropia should be assessed with:

  • Standardized timing of the tropic phase

  • Prism and alternate cover test

  • Near stereoacuity

  • Standardized assessment on the synoptophore



The current evidence suggests

  • The current evidence suggests

  • Overminus may be more effective when control is moderate

  • Overminus may be more effective when control is poor

  • There is no relationship between the effectiveness of overminus and level of control

  • Overminus is ineffective as a treatment for intermittent exotropia



The current evidence suggests

  • The current evidence suggests

  • Overminus may be more effective when control is moderate

  • Overminus may be more effective when control is poor

  • There is no relationship between the effectiveness of overminus and level of control

  • Overminus is ineffective as a treatment for intermittent exotropia





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