1. Sensory causes of diplopia- Aniseikonia
LIONEL KOWAL
RVEEH MELBOURNE
Financial involvement:
Patients paid their bills

2. Diplopia
2 images, one seen by each eye, are separated and the patient’s 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

3. 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]

4. Materials and methods Retrospective chart study 11 patients Aged 29-86
M:F 8:3

5. Results n=11 10 vision 6/8 or better in the worse eye
10 complained of diplopia
1 had wobbling of words

6. 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

7. 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

8. AWAYA’S NEW ANISEIKONIA TEST
Use R-G glasses. Find the pair of semi-
circles where the difference in size compensates for the patient’s aniseikonia

9. 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

10. 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 [m’morphopsia]? 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

11. Results n=11 7 /11 had vertical deviation
?vertical fusion is more fragile than horizontal
3 /7 also had horizontal deviations
2 had exophoria with poor FR

12. Results n=11 5 modified spectacles + prisms 1 contact lenses
1 reduced prescription of near add on one lens

13. Results n=11
1 had telescopic lenses (+ve CL and –ve spectacle lens) FOR 20% ANISEIKONIA
2 had surgery for exotropia
1 declined treatment

14. 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

15. Discussion Two main clinical causes of Aniseikonia Macular causes
Anisometropia
~ 1% of aniseikonia per DS of anisometropia

16. Measured stereo, motor fusion & VA.
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

17. 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

18. 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

22. Discussion