Multifocal IOLs (Intraocular Lens Implants) are the most
popular and successful of the various IOL designs meant to provide good
uncorrected distance and near vision after cataract surgery. So why wouldn't
every ophthalmologist suggest them to their patients?
There are two main reasons: 1) Multifocal IOLs
work in a different way to provide near vision than the natural human lens: The
"rings" in the IOL are each set at a progressively closer focal distance rather
than having the lens change shape. The biggest "negative" to this is the
appearance of concentric rings around lights at night (although these tends to
fade away with time).
2) To work the best, the focus of the eye at distance has to
be near perfect after surgery -no residual astigmatism or nearsightedness. This
is more difficult to achieve than you might think. Selecting the right
prescription is based on a regression analysis of past patients and not
directly on the actual measurement of the prescription of the natural lens in
the eye to be operated on. Even in the hands of the most precise and
perfectionist eye surgeons, the accuracy of getting a perfect distance focus is
plus or minus 0.5 diopters about 70% of the time. That is simply not good
enough for refractive surgery (like LASIK).
So the ophthalmologist is faced with a challenge: the patient
is going to be paying much more money out-of-pocket and might not be satisfied
with the results. Getting it right in such cases may require more surgery or
perhaps a laser adjustment of the cornea to make it right. Most
ophthalmologists do not have their own laser to do LASIK with or their own
operating room, if needed.
So it is easier to just recommend the single vision, or
monofocal IOL.
_Written by J. Trevor Woodhams, M.D. - Chief
of Surgery, Woodhams Eye Clinic
