Esotropia Associated with Early Presbyopia Caused by Inappropriate Muscle Length Adaptation Raj Chalasani OMC Journal Club 16/9/08 Guyton et al J AAPOS 2005; 9:

Hypothesis EOM adaptation 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 In presbyopia a larger accommodative effort is associated with increased convergence tonus If fusional divergence mechanisms are decreased/absent esotropia may result If fusional divergence mechanisms are decreased/absent esotropia may result Over time leads to MR shortening and LR lengthening 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 Higher occurrence/worsening of ET with the onset of presbyopia

Methods Retrospective review of all pts undergoing surgery for ET 1980 – 1996 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 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 Plot of number of pts versus age of onset/recurrence of deviation for each group

Results 617 pts > 10yrs undergoing ET surgery 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 yrs age range Statistically sig (P=0.017) increase in incidence of esotropic shift in yrs age range

Results

Conclusion Increased occurrence/recurrence of ET in the yr age bracket Increased occurrence/recurrence of ET in the yr age bracket Supports authors’ hypothesis Supports authors’ hypothesis To avoid excessive accommodative effort with accompanying convergence tonus in patients showing esotropic shift: 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 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 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 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: Kushner BJ Arch Ophthalmol 2001; 119: –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