CATARACTS
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Cataract Surgery: Past and Present
Cataract surgery is one of the most
common surgical procedures performed world wide today. Greater
than 85% of people over the age 65 have a clinically significant,
possibly treatable cataract. Dramatic, modern advancements
in cataract surgical technique have profoundly affected
its predictable ability to improve the quality of life for
most patients.
The word cataract means “waterfall,
or downpour”, and was derived originally to describe
the “white” appearance of these spectacles of
nature. A very mature, advanced human cataract has a white,
or opaque appearance.
Cataract is a gradual, natural change,
which affects the clarity of the lens of the eye. The human
lens is a convex, discoid structure located just behind
the pupil. This physiologic lens has dioptric, or “light
focusing” power for vision, which is similar to the
power in spectacles. In its normal state the lens is optically
clear, without significant discoloration or opacification.
Light from the viewing environment must pass through the
lens to reach the retina, which sends a “vision message”
to the brain. If the lens is not clear, vision will not
be optimal.
With age, the human lens undergoes “sclerosis”
(yellowing and hardening), as well as “cortical change”
(development of irregular opacifications). In the clinical
arena, these changes are termed “cataractous”;
a lens with cataractous change is called a “cataract”.
Cataractous change usually occurs gradually
over time, and when significant, causes blurred vision,
decreased clarity of color perception, and glare in the
presence of bright light. If these problems affect a person’s
ability to function well in the activities of daily life,
it is appropriate for the ophthalmologist to offer cataract
surgery. Modern cataract surgery is not only among the most
commonly performed surgeries today; it is also among the
most successful.
Over the past two centuries, cataract
surgery has progressed through a continuum of advancement,
with the most far-reaching improvements in the procedure
being developed over the past twenty years.
Prior to the mid 18th century, cataract
was recognized as an “opacity behind the pupil”,
which “obstructed the visual spirits”, yet the
fact that it was actually an opacified lens which could
be removed and replaced, was poorly understood.
At that time in history, initial surgical
attempts at eliminating the vision blurring effects of cataract
involved simply inserting a long needle into the eye, engaging
the cataract with the needle, and displacing it inferiorly,
effectively removing the opacity from behind the pupil.
This primitive procedure was called “couching”,
or “depression” of the lens, which basically
remained in the eye, but outside the “visual axis”.
Due to the fact that a ruptured lens, which remains inside
the eye, causes severe inflammation, and because the dioptric
power of the lens was not restored with couching, patients’
vision would predictably remain very poor after this procedure,
and its success rate was limited.
The first clear reference to actual
extraction or removal of the cataractous lens from the human
eye, was written by a scientist named Daviel, in the mid
18th century. Scientists at that time had gained understanding
of the importance of removal of the cataractous lens from
the eye, but these early cataract surgical incisions were
extremely large, and techniques for removal of the lens
were very primitive, traumatic, and commonly calamitous.
From that time to the present, increasingly
sophisticated, more atraumatic methods of lens extraction,
through increasingly smaller surgical incisions, have very
dramatically improved the success rate of cataract surgery.
We now perform cataract extraction by
inserting a “phacoemulsification tip” (a pencil-shaped
instrument which very gently aspirates the cataract from
its capsular bag), through a very small, three- millimeter
corneal incision. The decrease in trauma to the
eye with more sophisticated lens removal technique, as well
as the decrease in the surgical incision size,
have been the most important reasons for modern day, “state
of the art” cataract surgery’s minimal recovery
time and extremely high success rate.
Also, very importantly, we can now successfully
replace the physiologic lens with a lens implant, negating
the need for very thick, “coke bottle” (aphakic)
spectacles, which patients commonly had to wear after cataract
surgery in the “not too distant” past. In fact,
the advent of successful intraocular lens implantation has
given cataract surgery patients relative independence from
spectacles in most cases, especially for distance vision.
The most successful intraocular lens
implant materials today are polymethylmethacrylate (PMMA),
silicone, and most recently, acrylic. PMMA is rigid, and
not “foldable”, so a larger incision size is
required for this implant material. Silicone and acrylic
implants are the only currently available soft (foldable)
intraocular lens implants; the fact that they are foldable
means that they may be inserted through a very small incision;
they then unfold inside the eye, behind the pupil, just
after insertion into the physiologic capsular bag.
The advent of these foldable intraocular
lenses has allowed surgeons to decrease the incision size
so dramatically that sutures are usually no longer required.
A smaller incision size also translates into better vision
after surgery, and a much shortened recovery period for
the patient. Today’s cataract surgery has become so
relatively atraumatic, and its recovery period so short,
that the risks associated with surgery are now extremely
low.
In fact, clear lens extraction
with intraocular lens implantation is becoming a reality,
as an alternative to LASIK, for younger patients who have
not yet developed cataracts, but who desire correction of
refractive errors, in order to decrease dependence on spectacles
or contact lenses.
With the advent of “multifocal”
intraocular lens implants, (which, unlike LASIK, will give
patients uncorrected “bifocal” vision),
experts are now arguing that “clear lensectomy”
(with multifocal intraocular lens implantation) will be
the “refractive procedure of choice” in the
very near future.
We live in an amazing technological
era; there’s no better example of this than today’s
state of the art cataract surgery.
