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Mono Vision & Blended Vision
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Monovision is a method for providing a combination of distance
and near vision in order to achieve maximum visual freedom. Contact lenses,
glasses and virtually all surgical methods for correcting vision can take advantage
of the Monovision method. This includes LASIK, LASEK, Verisyse Lenses, Cataract surgery
and RLE/CLE. Even multifocal and accomodating lens implants often take advantage of
the Monovision approach.
The Monovision method, has been used for years
with contact lens and LASIK patients, and is still used extensively for
such patients who are 40 years or older and desire maximum freedom from
both distance and reading glasses.
When combined with removal of the eye's natural lens in Cataract surgery or Refractive
Lens Exchange, monovision uses highly-refined, single-focus lenses that can even correct
astigmatism. These lenses fix focus for one distance, usually either driving distance or
reading distance. When both eyes are to have surgery, the choice of lens implant strength
or focus can be made so that one eye sees best off in the distance and the other eye can
read. This is the essence of Monovision and it is a method that has been used with lens
implant patients for many years with good success.
The term Blended Vision is used to describe essentially this same approach
but using a slightly farther out reading distance in the near-vision eye. This is especially
useful for being in focus for computer monitors, seeing papers across the top of a desk,
reading at a podium, seeing instruments on a dashboard and like activities performed at around
arms length. These activities usually require a reading distance that is farther out than
the distance at which you might read a book - especially if reading in bed, or for sewing,
knitting, needle-point, reading small labels and the like. An advantage of Blended
Vision is that the difference between the focusing of the two eyes
is less significant and this can make it easier to adjust to this difference.
Monovision and Blended Vision are even combined with the
newest, high-tech multifocal lens implants, such as the AcrySof ReSTOR
multifocal lens and the Eyeonics Crystalens.
These lenses are disigned to focus both at distance and near; however, even these advanced
lenses are often fine-tuned for individual patients using the monovision technique. Impressively,
even without the benefit of monovision, 80% of ReSTOR
patients used no glasses after their Cataract surgery in one study.
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More About Monovision and Blended Vision for Reading and Distance Vision |
Vision-correcting surgery such as LASIK, PRK, Verisyse, RLE and Cataract surgery
can precisely and accurately correct fixed focal errors of the eye
such as nearsightedness, farsightedness, and astigmatism. These optical conditions
are fundamentally different than presbyopia, the loss of
adjustability of focus for near viewing. Presbyopia is the reason that
reading glasses (magnifiers) become necessary, typically in the mid-40's, even for
people who have excellent unaided distance vision. For those that require prescriptive
correction to see clearly at distance, bifocals or separate (different prescription)
reading glasses become necessary at that age to see clearly at close range.
There are several options available to those who are presbyopic, besides wearing
bifocals or separate distance and reading glasses. If you are mildly nearsighted,
you might simply remove your distance glasses for near viewing. Contact lenses can
be worn for distance correction in both eyes, and dime-store reading glasses
("granny glasses") can be put on to read.
For some individuals, wearing a contact lens in one eye for distance vision,
and a contact in the other eye for reading, affords a reasonable solution.
This is called Monovision
(mono for one; one eye for distance, one eye for near vision). The approach referred
to as Blended Vision provides for the reading eye to have more of
a blend between close reading vision and full distance vision.
The same option can be created on a more permanent basis with vision-correcting surgery
such as LASIK, PRK, Verisyse Lens, RLE and Cataract surgery. If you are contemplating
such correction for yourself, it is important to understand the advantages and drawbacks
of such care.
At this time, there is no perfect treatment or cure for presbyopia.
The typical solutions described above are all to some extent a compromise of one form or
another. For many people, wearing eyeglasses for distance correction is troublesome enough,
and wearing bifocals is even less pleasant. Many people dislike bifocals with a distinct
line visible in the lenses, and are willing to sacrifice some degree of sharpness and clarity
to eliminate the line (progressive, blended, or Varilux lenses, for example). With increasing
use of computers in our home and work, additional problems arise because we view computer
monitors at a different distance and a different angle (from the horizontal) than typical
written material.
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Vision, Depth Perception and Balance:
Since Monovision and Blended Vision are compromises, like other forms of near
vision correction, it is important to understand what you can expect from Mono-
or Blended Vision with LASIK, PRK, Verisyse Lens, RLE and Cataract surgery in the areas
of Vision, Depth Perception and Balance. Being accustomed to seeing distant objects clearly
with both eyes together using glasses or contacts, you will find one compromise to be that
your distance vision will be affected somewhat by your monovision (reading) eye. This eye
will focus best on near objects and, therefore, will be somewhat blurred looking off in
the distance. It is most noticeable when you test each eye separately and compare to
two eyes.
However, when using both eyes together for distance, the dominant eye "takes over"
and the brain makes the two eyes work together but gives more "weight" to the dominant eye.
If both eyes were focused for distance, sharpness would somewhat greater than with monovision,
though distance vision with monovision is usually quite adequate. The reverse is true for reading
vision where now the monovision eye will be the clearer eye, but the two eyes usually work quite
well together as strange as this sounds, Keep in mind that with monovision both eyes are used
together 100% of the time, however the brain automatically favors one or the other eye depending on
the distance you are viewing. You do not have to decide which eye to use, you will be using
both eyes together and the brain will decide for you how to make this vision sharpest for you.
For most people, depth perception is best when viewing with both eyes optimally corrected
and "balanced" for distance. Eye care professionals refer to this as binocular
vision. Monovision and, usually to a somewhat lesser degree, Blended Vision can impair depth
perception and balance to some extent, because the eyes are not focused together at the same
distance. For most patients, these visual symptoms are relatively mild and the compromise
is generally worthwhile since it usually results in the ability to see reasonably well both
at distance and near thus providing greater visual freedom.
However, because monovision can
reduce optimum depth perception and balance, it will be demonstrated as an option in order
for you to see for yourself what this might look like prior to any decision. This usually can
be demonstrated adequately using glasses lenses during your consultation and may require more
than one demonstration. It is sometimes recommended that this option be tried with contact
lenses (which are removable) prior to contemplating a surgical correction (which is permanent).
This can be helpful and this is recommended if you have a desire to do so and you are able to
tolerate a trial of contact lenses. At ARROWSMITH EYE INSTITUTE, if you would like to attempt
Mono- or Blended Vision with soft contact lenses, we will often be able to provide, at no charge,
the contacts you would need on a trial basis.
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Ocular dominance, and choosing the 'distance' and 'near' eye correctly:
This can be
helpful if you are contemplating Mono- / Blended Vision with your LASIK or other vision-correction
surgery. Ocular dominance is analogous to right or left-handedness. Typically, eye care professionals
believe that for most individuals, one eye is the dominant or preferred eye for viewing. Several
tests can be performed to determine which eye, right or left, is dominant in a particular person;
however, your history of taking pictures with a camera, shooting a gun or performing some other
one-eyed function is often the most reliable way of determining ocular dominance. Conventional
wisdom holds that if contemplating monovision, the dominant eye should be corrected for distance,
and the non-dominant eye corrected for near.
While this is a good guideline, it is not an absolute
rule. A small percentage of persons may be co-dominant (rather analogous to being ambidextrous), and
in some circumstances a person may actually prefer using the dominant eye for near viewing. The
methods for testing and determining ocular dominance are not always 100% accurate; there is some
subjective component in the measurement process; and different eye doctors may use slightly different
methods of testing. It is important to determine through your history and the use of lenses
(glasses or contacts) which combination is best for each person (right eye for distance, left
for near; or vice versa) prior to undergoing surgery.
Be sure you understand this and have discussed
with your surgeon which eye should be corrected for distance, and which for near. If you or the doctor
have any doubts or uncertainty about eye dominance or your comfort level with monovision, further
testing will usually resolve such questions. Should you have monovision as the result of your surgery
and feel that it is not working for you, further surgery can usually be done to adjust your result
either by increasing or decreasing the strength of your monovision. In rare instances, a person might
decide to convert the near eye to a distance eye and the wear readers, usually over-the-counter
readers, for near vision.
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Will I have to wear glasses at times?
Because extremely strong monovision is
avoided except in special circumstances, Vision, Depth Perception and Balance are generally not greatly
affected. Therefore, your monovision should provide a lot of freedom from readers, but it is not perfect
and generally will not be totally adequate under all circumstances. For example, the extra help of
readers is often desirable when in poor lighting, reading very small print, working very close to your
material and reading for extended periods of time. For such occasions, over-the counter readers are
usually adequate even though the focus of your two eyes is not equal and the reading lenses are the
same for both eyes. Distance glasses might be needed also, for example, if driving at night in poorly
lighted and unfamiliar areas where you need to be able to read road signs as soon as possible. If desirable,
such glasses are usually provided by our office at no charge to you.
As your eyes mature, more of your natural reading ability will, of course, decrease. Reading
difficulty beginning about age 40 will be moderate usually about age 45 and more significant
by age 50. This loss of natural focusing tends to start to level off around 55 to 60 and
the process is essentially complete by around age 65. At each age, the amount of monovision
given you with LASIK should be an amount appropriate for your age and your
activities. It would be too much, and unnecessary, to give you at 40-45 the same amount
needed for someone 55-60. The more mature your eyes are when you have monovision created,
the stronger and more lasting the monovision will tend to be. If you have monovision created
when you are less than about age 50, you may want to have this enhanced in the future.
There are now additional options for providing both distance and near vision with some
surgical procedures. With both RLE and Cataract surgery, there are now advanced multifocal
or accommodative lens implants. These include the ReSTOR multifocal
and the Crystalens accomodative lenses. Follow these links to learn more about these options.
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