Esotropia Associated Esotropia Associated with Early Presbyopia with Early Presbyopia

Caused by Inappropriate Caused by Inappropriate Muscle Length Muscle Length

AdaptationAdaptation

Raj ChalasaniRaj Chalasani

OMC Journal Club 16/9/08OMC Journal Club 16/9/08

Guyton et alGuyton et al

J AAPOS 2005; 9:563-566J AAPOS 2005; 9:563-566

HypothesisHypothesis EOM adaptationEOM adaptation

– Addition or loss of sarcomeres in response to:Addition or loss of sarcomeres in response to: Chronic extension/contractionChronic extension/contraction Changes in neural stimulationChanges in neural stimulation

In presbyopia a larger accommodative effort is In presbyopia a larger accommodative effort is associated with increased convergence tonusassociated with increased convergence tonus

If fusional divergence mechanisms are If fusional divergence mechanisms are decreased/absent esotropia may resultdecreased/absent esotropia may result

Over time leads to MR shortening and LR Over time leads to MR shortening and LR lengtheninglengthening– Worsening of ETWorsening of ET– Non-accommodative componentNon-accommodative component

Higher occurrence/worsening of ET with the onset of Higher occurrence/worsening of ET with the onset of presbyopia presbyopia

MethodsMethods

Retrospective review of all pts Retrospective review of all pts undergoing surgery for ET 1980 – undergoing surgery for ET 1980 – 19961996– 10 yrs or older10 yrs or older– Clear indication of timing of Clear indication of timing of

onset/recurrence of ETonset/recurrence of ET– No paralytic/restrictive componentNo paralytic/restrictive component– No other ocular diseaseNo other ocular disease

MethodsMethods

Comparison with similar number of Comparison with similar number of consecutive pts undergoing surgery consecutive pts undergoing surgery for XTfor XT

Plot of number of pts versus age of Plot of number of pts versus age of onset/recurrence of deviation for onset/recurrence of deviation for each groupeach group

ResultsResults

617 pts > 10yrs undergoing ET 617 pts > 10yrs undergoing ET surgerysurgery– 105 met other criteria105 met other criteria

72 (69%) no measurable stereoacuity72 (69%) no measurable stereoacuity

Statistically sig (P=0.017) increase in Statistically sig (P=0.017) increase in incidence of esotropic shift in 30-50 incidence of esotropic shift in 30-50 yrs age rangeyrs age range

ResultsResults

ConclusionConclusion Increased occurrence/recurrence of ET in the 30-50 yr Increased occurrence/recurrence of ET in the 30-50 yr

age bracketage bracket

Supports authors’ hypothesisSupports authors’ hypothesis

To avoid excessive accommodative effort with To avoid excessive accommodative effort with accompanying convergence tonus in patients accompanying convergence tonus in patients showing esotropic shift:showing esotropic shift:– Full hyperopic correction for distanceFull hyperopic correction for distance– At least age-appropriate reading add for full-time useAt least age-appropriate reading add for full-time use

MonovisionMonovision– Care in determining which eye preferred for distance/nearCare in determining which eye preferred for distance/near– Appropriate power for each eye to avoid excessive Appropriate power for each eye to avoid excessive

accommodation at the preferred viewing distanceaccommodation at the preferred viewing distance

DiscussionDiscussion WeaknessesWeaknesses

– Retrospective designRetrospective design

– Tertiary centreTertiary centre Referral biasReferral bias

– No mention of visual acuities/amblyopia/rates of No mention of visual acuities/amblyopia/rates of previous surgeryprevious surgery

– Large number of cases excludedLarge number of cases excluded

– XT also shows a peak in 30s/40sXT also shows a peak in 30s/40s Not explained by authors’ theoryNot explained by authors’ theory

Literature ReviewLiterature Review

Oystreck DT and Lyons CJ Oystreck DT and Lyons CJ Can J Can J Ophthalmol 2003; 38(4):272-8Ophthalmol 2003; 38(4):272-8– 1 year prospective trial1 year prospective trial– Patients with pre-existing strabismus or Patients with pre-existing strabismus or

heterophoriaheterophoria– Recent decrease in accommodative Recent decrease in accommodative

amplitudeamplitude– Resulting in new onset diplopiaResulting in new onset diplopia– 11 cases11 cases

Literature ReviewLiterature Review

Kushner BJ Kushner BJ Arch Ophthalmol 2001; Arch Ophthalmol 2001; 119:1795-1801119:1795-1801– Retrospective review of 132 cases with Retrospective review of 132 cases with

strabismus in childhoodstrabismus in childhood– Presenting with new onset diplopia after Presenting with new onset diplopia after

age 18age 18– 9 cases thought to be associated with 9 cases thought to be associated with

presbyopiapresbyopia