Download Et associated with early Presbyopia

Esotropia Associated with
Early Presbyopia Caused by
Inappropriate Muscle
Length Adaptation
Guyton et al
J AAPOS 2005; 9:563-566
Raj Chalasani
OMC Journal Club 16/9/08
Hypothesis

EOM adaptation
– Addition or loss of sarcomeres in response to:
 Chronic extension/contraction
 Changes in neural stimulation

In presbyopia a larger accommodative effort is
associated with increased convergence tonus

If fusional divergence mechanisms are decreased/absent
esotropia may result

Over time leads to MR shortening and LR lengthening
– Worsening of ET
– Non-accommodative component

Higher occurrence/worsening of ET with the onset of
presbyopia
Methods

Retrospective review of all pts undergoing
surgery for ET 1980 – 1996
– 10 yrs or older
– Clear indication of timing of onset/recurrence
of ET
– No paralytic/restrictive component
– No other ocular disease
Methods

Comparison with similar number of
consecutive pts undergoing surgery for XT

Plot of number of pts versus age of
onset/recurrence of deviation for each
group
Results

617 pts > 10yrs undergoing ET surgery
– 105 met other criteria
 72 (69%) no measurable stereoacuity

Statistically sig (P=0.017) increase in
incidence of esotropic shift in 30-50 yrs
age range
Results
Conclusion

Increased occurrence/recurrence of ET in the 30-50 yr
age bracket

Supports authors’ hypothesis

To avoid excessive accommodative effort with
accompanying convergence tonus in patients showing
esotropic shift:
– Full hyperopic correction for distance
– At least age-appropriate reading add for full-time use

Monovision
– Care in determining which eye preferred for distance/near
– Appropriate power for each eye to avoid excessive
accommodation at the preferred viewing distance
Discussion

Weaknesses
– Retrospective design
– Tertiary centre
 Referral bias
– No mention of visual acuities/amblyopia/rates of
previous surgery
– Large number of cases excluded
– XT also shows a peak in 30s/40s
 Not explained by authors’ theory
Literature Review

Oystreck DT and Lyons CJ Can J
Ophthalmol 2003; 38(4):272-8
– 1 year prospective trial
– Patients with pre-existing strabismus or
heterophoria
– Recent decrease in accommodative amplitude
– Resulting in new onset diplopia
– 11 cases
Literature Review

Kushner BJ Arch Ophthalmol 2001;
119:1795-1801
– Retrospective review of 132 cases with
strabismus in childhood
– Presenting with new onset diplopia after age
18
– 9 cases thought to be associated with
presbyopia