Sensory causes of diplopia- Aniseikonia - Private Eye Clinic
Sensory causes of diplopia- Aniseikonia LIONEL KOWAL RVEEH MELBOURNE Financial involvement: Patients paid their bills Diplopia 2 images, one seen by each eye, are separated and the patients motor and sensory fusion are inadequate to bring them together Usually only consider the motor aspect of
separation Motor fusion impaired by sensory problems - the 2 images need to be fairly similar to be fused: Aniseikonia - difference in image size - will prevent fusion
Metamorphopsia Field defect Often treatable with glasses You miss more by not asking than by not knowing ..after John Colvin ASK EVERY PATIENT WHOSE DIPLOPIA IS NOT EASILY COMPENSATED FOR WITH PRISM: Is the image seen by the R Larger / smaller than the L
The same shape as L Paler / darker than L Tilted [not aniseikonia: torsion] Materials and methods Retrospective chart study
11 patients Aged 29-86 M:F 8:3 Results n=11
10 vision 6/8 worse eye 10 complained of diplopia
1 had wobbling of words or better in the Results n=11 Anisometropia in 7
Macular causes in 4 2/4 had ERM on macula NO ERM SURGERY 1/4 had previous ERM peel with residual or recurrent ERM temporal to macula 1/4 had macular hole surgery & anisometropia RESPONDED TO GLASSES FOR ANISOMETROPIA Measuring aniseikonia
The least amount of aniseikonia causing disruption of fusion was 2% Largest amount of aniseikonia was 20 % which was corrected with telescopic lenses (+CLs with equal in glasses) Other techniques: Synoptophore Free space techniques
AWAYAS NEW ANISEIKONIA TEST Use R-G glasses. Find the pair of semicircles where the difference in size compensates for the patients aniseikonia Measuring aniseikonia Free space estimation Separate with prism. Which eye sees the bigger / smaller image? If each bar of the E is ~20%, how much bigger / smaller is the image seen by L? R? Check with prism in front of other eye prisms can cause magnification
CONFOUNDER: MEASUREMENT ARTEFACT - each technique can give a VERY different answer Ask pt to look @ both 6/60 E. RE sees the higher image. Which one is bigger? Does it look like an E should? Are all parts of it bigger [mmorphopsia]? Is the E Tilted? If a bar of the E is worth 20%, how much bigger is it? Also check with BD prism in front of other eye - prisms can also cause magnification Results
7 /11 n=11 had vertical deviation ?vertical fusion is more fragile than horizontal 3 /7 also had horizontal
deviations 2 had exophoria with poor FR Results 5 n=11 modified spectacles + prisms 1 contact lenses 1 reduced prescription of near add on one lens
Results n=11 1 had telescopic lenses (+ve CL and ve spectacle lens) FOR 20% ANISEIKONIA 2 had surgery for exotropia 1 declined treatment Results In most patients, aniseikonia
precipitates small angle strabismus due to loss of sensory fusion wch in turn impairs motor fusion Compensation for the strabismus with prisms along with lenses modified to compensate for the aniseikonia worked in 5/7 optically corrected patients Discussion
Two main clinical causes of Aniseikonia Macular causes Anisometropia ~ 1% of aniseikonia per DS of anisometropia A Prospective Study of Binocular Visual Function before and after Successful Surgery to Remove a Unilateral
Epiretinal Membrane Ophthalmology November 2008 2/27: diplopia Measured stereo, motor fusion & VA. Stereo & total motor fusion ranges reduced
After successful surgery, stereo function, VA & motor fusion improved mainly in those with shorter duration of symptoms [esp < 18mo] Stereo function improved mainly in those with better preoperative stereo Optical solutions to increase image size
Increase front base curve Increase central thickness Decreased vertex distance increases image size in lens [and decreases in +] increase refractive index .often successful NOT known to average optometrist / dispenser Aniseikonia as a substantial factor in
causing diplopia Probably rare Always unrecognised by referring doctor or optom Need to ask about it - pt always knows but needs to be asked the right Q
Often fixable with prisms and aniseikonic modifications THANK YOU Discussion
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