This document discusses aniseikonia, which is a condition where the two eyes perceive images as being different in size. It can be caused by differences in the dioptric images formed by the retina or differences in retinal element distribution. The document describes static aniseikonia, where peripheral images differ in size with static gaze, and dynamic aniseikonia, where the eyes must rotate different amounts to gaze. Signs include aphakia, anisometropia, astigmatism, low stereopsis, and strabismus. Symptoms include headaches, asthenopia, reading difficulty, photophobia, nausea, vertigo, and fatigue. Aniseikonia is measured using an e

1. Causes and
Management
of
Aniseikonia
Maclester OP 1-1

2. Causes of Aniseikonia
 1. Differences in size of dioptric images formed by the retina.
 2. Difference in the distribution of retinal elements.
Fig. 1: Schematic presentation of static aniseikonia (left) and
dynamic aniseikonia / anisophoria (right).

3.  Static aniseikonia or aniseikonia in short means that in a
static situation where the eyes are gazing in a certain
direction, the perceived (peripheral) images are different in
size.
 Dynamic aniseikonia or (optically induced) anisophoria
means that the eyes have to rotate a different amount to
gaze
Signs of Aniseikonia
 Aphakia
 Anisometropia
 Astigmatism
 Low Stereopsis
 Strabismus
 Amblyopia

4. Symptoms Associated with Aniseikonia
 Headache
 Asthenopia
 Reading difficulty
 Photophobia
 Nausea
 Vertigo and dizziness
 General fatigue

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

6.  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.

8.  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.

9. 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

10.  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

11. 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

12.  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.

14. 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.