Implantable Lenses (Phakic IOLs)
By Marilyn Haddrill;
reviewed by Dr. Vance Thompson
and Dr. Brian Boxer Wachler
Surgically implanted lenses, also called phakic IOLs (intraocular lenses), are
a new option for people seeking more permanent correction of common vision errors such as myopia
(nearsightedness).
These implants, which resemble contact lenses, are placed between the clear front covering of the eye
(cornea) and the
iris
(colored portion of the eye) or just behind the iris.
Implantable lenses are a surgical alternative to LASIK.
Both procedures alter the way light rays enter the eye to achieve sharper focus.
LASIK does this by removing tissue from the eye's cornea to change its shape;
implantable lenses function like glasses or contact lenses, except they do it
from within your eye. Implantable lenses do not require tissue to be removed from
the eye as with LASIK; these lenses are effectively added to the eye.
Implantable lenses are similar to the intraocular lenses (IOLs) used in
cataract surgery. However, implantable lenses are
placed in eyes that retain their natural lens, unlike in cataract surgery where IOLs replace
a natural lens that has turned cloudy.
Eye surgeons may consider implantable lenses for their patients when other vision correction
procedures aren't a good option, such as in cases of thin corneas or myopia between -3.00 diopters
and -20.00. With some patients receiving phakic IOLs, LASIK may be used as a follow-up to
refine vision correction.
Two Food and Drug Administration-approved implantable lenses now are available in the United States,
including:
- Verisyse (Advanced Medical Optics, Santa Ana, Calif. Marketed as the Artisan outside the
United States
by Ophtec, Groningen, The Netherlands) In September 2004, one phakic IOL known as the Verisyse received
FDA approval for correcting nearsightedness in moderate to severe ranges of -5 to -20 diopters; patients
must be 21 years or older. Made of a type of plastic known as PMMA, this lens has been marketed for a
number of years in Europe under the trade name Artisan.
- Visian ICL (Staar Surgical, Monrovia, Calif.) A second lens, the Visian ICL or Implantable Collamer Lens,
received final FDA approval for marketing in the United States in late December 2005. The Visian ICL is made partly
from a biocompatible material known as collagen. The ICL is foldable, which means smaller surgical entry incisions
and potentially reduced recovery times. FDA approval is for patients older than 21 with nearsightedness in
moderate to severe ranges of -3 to -20 diopters. Many years before FDA approval, the Visian ICL was approved and marketed in many countries
outside the United States, including in Europe.
Both the Verisyse and ICL implantable lenses are FDA-approved for treating nearsightedness only.
Clinical trials for the two lenses are continuing for potential FDA approval for treating near vision defects
(farsightedness,
or hyperopia). A version of the Visian ICL
(toric)
also is being studied for correction of higher levels of
astigmatism.
Look for other types of phakic IOLs eventually to become available in the
United States, including additional
foldable styles that can be implanted with smaller incisions. Research also continues on
multifocal phakic IOLs
that potentially could simultaneously correct vision defects in near, middle, and distant ranges
similar to the functionality of multifocal eyeglasses and contact lenses.
[See also: Multifocal Contact Lenses]
How the Procedure Is Done
Prior to surgery, drops are placed in the eye to reduce pupil size.
An instrument is attached to hold open the eyelids during the procedure,
and a local anesthetic is given to numb the eye's surface. An incision
then is made into the eye. The Verisyse phakic IOL is inserted and attached to
the colored portion of the eye (iris). Tiny, dissolvable stitches are used to
close the wound. An eye shield will need to be worn for a short time
following the procedure, which lasts about 15-30 minutes.
The folded Visian ICL is inserted just behind the eye's iris and in front of the
natural lens. After being placed through the microincision, the artificial lens then unfolds to its full width following implantation,
which requires no sutures. Once inserted during about a six-minute procedure,
the Visian ICL is invisible to the naked eye because of its location behind the
iris. It can only be seen with a microscope during eye examinations.
|