Multifocal Lens Implants

Vision Correction At All Distances

Bring Your World Into Focus
Another tremendous improvement in an already great technology, multifocal lens implants
are providing people with an even greater level of visual freedom. Intraocular lens implants
(IOLs) were first developed over 50 years ago and have been used routinely to correct
vision after cataract surgery since the 1980’s. Traditional lens implants do an excellent job
for many people in restoring vision after the removal of their natural lens. These implants
provide good focusing at one specific distance (monofocal) usually resulting in excellent
distance vision and pretty good intermediate vision. To be able to also have excellent
reading or near vision, reading lasses are usually required.
Multifocal Lens Implants
For people with more demanding lifestyles, new multifocal lens implants provide much
greater visual freedom. Multifocal lens implants offer a more complete range of good vision,
from distance to near reading vision, without cumbersome or unsightly reading glasses or
bifocals.
Normal Vision
Vision occurs when light passes through the cornea and the lens of the eye and is focused
onto the retina. The retina then transmits the image to the brain via the optic nerve. When
light passes through a curved surface the rays are bent (refracted). The steeper the curved
surface, the greater the bend or refraction of light and the shorter the focal length. The
curve of the cornea provides most of the focusing for the eye. The curve of the lens of the
eye fine tunes vision to adjust focus (accommodate) between distant and near objects.
At rest, the lens of the eye is in a flatter state and focuses on distant objects. The shape of
the lens in controlled by relaxation or contraction of small fibers (zonules) and muscles
(ciliary body) which hold the lens in place. When we change attention from a distant object
to a near object, the lens almost instantly, gets rounder and the focal length is shortened
until the near object of our attention comes into focus.
Presbyopia
At birth the natural lens is soft and flexible, and its shape is easily controlled. As we mature,
it becomes less elastic and its ability to change shape is reduced. About the age of 40, the
elasticity of the lens has diminished to the point where its ability to change shape can no
longer accommodate focusing changes from distance to near. This lack of accommodation is
called Presbyopia and results in blurred near vision and difficulty doing close work like
reading. When presbyopia begins many people find reading difficult and hold reading
material further away in an attempt to see more clearly. Initially, the reading glasses or
bifocals are prescribed for presbyopia and eventually some people need trifocals. Multifocal
IOL’s can be a great choice for people with presbyopia.
The lens implant procedure
Although similar to traditional cataract and lens implant surgery, multifocal lens implant
surgery is more complex and precise. Sophisticated testing and preparation before surgery
is required by the doctors and the patient. Pre-surgery examinations are conducted and
questions asked to determine unique distant, intermediate and near vision needs. The
patient and doctor together must determine the most appropriate implant solution.
What to expect
The lens implant procedure is typically performed on an outpatient basis. You will be asked
to arrive about an hour before the procedure. The doctor will place drops in your eye to
numb it and dilate your pupil. You may also be given medication to help you relax.
The entire procedure should take less than 30-45 minutes. As you lie on your back, the
doctor will use a device to hold your eyelid open and you will be asked to look up into a
light. There may be a feeling of slight pressure, but you shouldn’t feel any pain. The doctor
will then make a small incision in your eye, remove the natural lens and replace it with a
lens implant.
Following the procedure, drops will be put into your eye to prevent infection and
inflammation. It’s a good idea to rest for the remainder of the day after your surgery.
The day after the procedure, your eyes will be checked and you may be given more drops to
promote healing. Due to increased light sensitivity you may also need to wear protective
sunglasses while outdoors.
After multifocal lens implants
You should be able to resume your normal activities with a day or so after your procedure,
but avoid heavy lifting or rubbing your eye. Complications following the implant surgery are
rare, but can include infection, bleeding, and retinal detachment. People with diabetes, high
blood pressure, and chronic infections are at higher risk for complications.
For the first few days after the procedure, your distance vision should be clear. You might
experience blurry intermediate or near vision until your visual system adapts to your new
multifocal lens implants. Lens implants are usually implanted in one eye at a time. After the
first eye has healed the second implant procedure is performed. With multifocal lens
implants most people find their ability to adapt to the intermediate and near focusing
characteristics of the lens is much better after both lenses have been implanted. Some
people find they need reading glasses for close up viewing during the short healing and
adjustment period.
Although your vision should improve with the implant, your eyes might take several months
to reach their full focusing potential. Reading and viewing objects up close without wearing
glasses can help strengthen your eyes. Because everyone’s eyes are different, some
patients will not be able to see 20/20 at all distances without glasses.
Phacoemulsification
A small incision is made using special micro surgery tools. Your surgeon will removal a small
cap from the lens capsule. Like a grape, your natural lens has an inner material (nucleus)
and an outer skin (capsule). Next, using a special phacoemulsification probe, the exposed
nucleus is removed using gentle ultrasound waves. Ultrasound reduces the material into
small particles that can be aspirated through the “phaco” probe. Removal of the nucleus in
this manner leaves the capsule in place to act as a container to hold the new lens implant.
How Do Multifocal Lens Implants Work?
ReZoom and ReSTOR Multiple Optical Zone IOL’S
Multifocal IOL’s with multiple optical zones have a series of concentric focusing rings
extending from the center of the lens to the lens periphery. Each ring section has it own
focusing power and corresponding focal point. With these lens designs distant vision is very
good right after surgery but intermediate and near vision may be blurry during the healing
period. Over a short adjustment period the brain learns to “look” through the best area of
the lens to provide good distant, intermediate or near vision as required by the object of
attention.
ReZoom Multifocal IOL
The ReZoom IOL has 5 focusing zones. The zones are designed to give good distance,
intermediate and near vision in a variety of bring or dim lighting conditions.
AcrySof Restor Multifocal IOL
The AcrySof ReStor IOL has 2 regions, a central region with 12 concentric rings with
apodized (gradually decreasing or blended) step heights and a peripheral refractive region
dedicated to distance vision. The peripheral region is also designed to enhance distance
vision under dim light conditions.
Crystalens Hinged IOL
The crystalens IOL uses the eyes zonules and ciliary body muscles to move the lens either
forward or backward to adjust the focal point for good vision. Relaxation and contraction of
the Ciliary Muscle (a.) results in either an increase or decrease in the tension of the zonules
holding the lens capsule and crystalens IOL. This change in tension causes the lens implant
to move either forward (b.), or backward (c.), adjusting the focal point for clear near vision
or clear distance vision. With this lens design distant vision is good right after surgery, and
over time, the brain learns how to manage the zonule and ciliary muscle combination to
control movement of the crystalens IOL and provide good distant, intermediate or near
vision as needed.
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