Ocular dominance, sometimes called eye preference or eyedness, is the tendency
to prefer visual input from one eye to the other. It is somewhat analogous to
the laterality of right- or left-handedness; however, the side of
the dominant eye and the dominant hand do not always match. This is because
both hemispheres control both eyes, but each one takes charge of a different
half of the field of vision, and therefore a different half of both
retinas. There is thus no direct analogy between "handedness" and "eyedness" as
lateral phenomena. Approximately two-thirds of the
population is right-eye dominant and one-third left-eye dominant; however in
a small portion of the population neither eye is dominant. Dominance does
appear to change depending upon direction of gaze due to image size
changes on the retinas. There also appears to be a higher prevalence of
left-eye dominance in those with Williams–Beuren syndrome, and possibly
in migraine sufferers as well. Eye dominance has been categorized as "weak"
or "strong"; highly profound cases are sometimes caused by amblyopia or
strabismus. In those with anisometropic myopia, the
dominant eye has typically been found to be the one with more myopia. As far as
regards subjects with normal binocular vision, the widespread notion that the
individual's better-sighted eye would tend to be the dominant eye has been
challenged as lacking empirical basis. Importance
In normal binocular vision there is an effect of parallax, and therefore the
dominant eye is the one that is primarily relied on for precise
positional information. This may be extremely important in sports which
require aim, such as archery, darts or shooting sports. Ocular dominance and
dominant hand should be ideally the same.
It has been asserted that cross-dominance is advantageous in
sports requiring side-on stances; however, studies within the last 20
years have shown this not to be the case. In a 1998 study of professional
baseball players, hand–ocular dominance patterns did not show an effect on
batting average or ERA. Similarly, in 2005, a South African study found that
"cricketers were not more likely to have crossed dominance" than the normal
population. Ocular dominance is an important
consideration in predicting patient satisfaction with monovision correction
in cataract surgery refractive surgery, also laser eye surgery, and contact lens
wear. Determination
A person's dominant eye "is determined by subjective alignment of two objects
presented at a stereodisparity far beyond Panum's area". There are a number
of ways to do this: The Miles test. The observer extends
both arms, brings both hands together to create a small opening, then with both
eyes open views a distant object through the opening. The observer then
alternates closing the eyes or slowly draws opening back to the head to
determine which eye is viewing the object.
The Porta test. The observer extends one arm, then with both eyes open aligns the
thumb or index finger with a distant object. The observer then alternates
closing the eyes or slowly draws the thumb/finger back to the head to
determine which eye is viewing the object.
The Dolman method, also known as the hole-in-the-card test. The subject is
given a card with a small hole in the middle, instructed to hold it with both
hands, then instructed to view a distant object through the hole with both eyes
open. The observer then alternates closing the eyes or slowly draws the
opening back to the head to determine which eye is viewing the object.
The convergence near-point test. The subject fixates an object that is moved
toward the nose until divergence of one eye occurs. It is an objective test of
ocular dominance. Certain stereograms.
The pinhole test. The ring test.
Lens fogging technique. The subject fixates a distant object with both eyes
open and appropriate correction in place. A +2.00 or +2.50 lens is
alternately introduced in front of each eye, which blurs the distant object. The
subject is then asked to state in which eye is the blur more noticeable. This is
the dominant eye. A dichoptic motion coherence threshold
test yields a quantified indication of ocular dominance.
The Spinning Dancer optical illusion may also reveal the same result as these
other determinants. Forced choice tests of dominance, such
as the Dolman method, allow only a right or left eye result.
Treatment It is possible to change eye dominance
by actively suppressing the visual field of the dominant eye. This is achieved
with an eye patch bandage that covers the dominant eye, with adhesive tape
around the patch perimeter. Another form of treatment is laser eye
surgery. The eye patch does not need to be black
to blot out all light, and the dominant eye does not need to stay closed. The
eye patch simply presents the dominant eye with a static unchanging visual
field containing nothing of visual importance, and the brain is forced to
rely on the suppressed eye for visual information.
The experience does cause irritation and frustration for the eye patch wearer
since their visual capabilities for comprehension will be reduced until the
brain starts to adapt to not being able to use the dominant eye.
See also Ocular dominance column
Right- and left-hand traffic References