This document discusses the measurement and management of aniseikonia. It describes several instruments used to measure aniseikonia, including the standard eikonometer and space eikonometer. It also discusses predicting aniseikonia through ocular component analysis using spectacle prescriptions, keratometry, A-scan ultrasound, and IOL status. Simple tests like size lenses, Maddox rod, and penlights as well as special tests like the Leaf Room effects and Awaya Aniseikonia test are outlined. Management of aniseikonia includes iseikonic lenses, toric lenses, doublet lenses, and fused bifocal lenses.

1. Measurement of
Aniseikonia
Maclester
OP 1-1

2. Measurement of Aniseikonia
Eikonometer – an instrument used to measure
the aniseikonic condition.
 Standard

3. The standard eikonometer is a special apparatus
designed to measure aniseikonia. It contains the
following elements: a device for securing the
fixation of the eyes in the desired planes by fixing
the head and presenting the targets along the
primary plane and the normal depressed plane
for near; devices which alter the size of the target
without affecting the refraction and measure
discrepancies in percent; a projector which
presents a target which has certain elements
polarized so that each eye sees some part of the
target alone and some parts simultaneously; and
polaroid filters before each eye to select the
target elements for each eye.

5.  Space eikonometer is a special device which performs its
function not by actual measurement of the ocular images
but by measuring the rotations of the observed field as
affected by binocular clues alone.

6. Predicting Aniseikonia: Ocular Component Analysis
 Spectacle Prescription
-Remember, the symptoms aniseikonia is nearly always
caused by the sign anisometropia
-Look for a minimum of 1.50 to 2.00 D to produce
symptoms in patients
-The higher the anisometropia, the more likely aniseikonia,
though it is never a guarantee
 Keratometry
-Use your keratometry readings to measure the optical
power of the eye, as usual
-To confirm the source of aniseikonia, compare the K’sOU

7.  A-Scan ultrasound
-A-scan ultrasound is routinely used in cataract surgery to
calculate IOL power, and IOL’scan cause aniseikonia too
 IOL Status
-More common these days is post-surgical
anisometropiawhen the post-surgical eye is plano, and the
other is at least +/-2 D
Simple Testing for Aniseikonia
 Size Lenses
 Maddox Rod
 Penlights
 Prism Bar

8. Special Testing for Aniseikonia
The Leaf Room Effects
 The leaf room is a cube with no size cues, perhaps
covered with patterned wallpaper, a leaf pattern, say
 This cubical “Leaf Room” doesn’t look square if you have
aniseikonia!
 You can use the Leaf Room to simulate aniseikonia
caused by high monocular astigmatism, even in normals.
How?
 With planocylindrical magnifiers (size lenses) in front of
one eye only, as follows

9.  Awaya Aniseikonia Test
This test, developed by Dr. Awaya of Japan, is very easy to
administer and interpret. The test uses a very clever direct
comparative approach with the patient viewing pairs of adjacent
calibrated half-moon targets - one red and one green.

11. Management of Aniseikonia
1. Iseikonic lenses- a correcting lens or device that
generally acts by altering magnification due to
thickness of the lens and base curve w/o altering its
power
2. Toric lenses- front or back surfaces are made toric or
both
3. Doublet lenses- combination of two lenses, one is
telescopic and the other on microscopic lens.
4. Fused bifocal lenses.