Ultra-thin lens reveals mystery
NICE - A new thin-as-a-hair IOL (ThinOptX®) which is implantable
through an incision smaller than 2.0 mm provides good visual results
and may even impart some pseudoaccommodation, a Spanish ophthalmologist
told the XX ESCRS Congress.
"The ThinOptx IOL is a plastic polymer lens which is 40 microns
thick with a special optical design such that the lens has the same
thickness regardless of the refractive power.
"It can be rolled for insertion into a 1.4 mm to 1.5 mm incision
and unfolds completely within 10 seconds of implantation,"
Jorge Alió MD said.
In six eyes of six cataract patients who underwent micro-incision
implantation of a ThinOptX IOL, the mean postoperative spherical
equivalent (SE) was -1.48 D and mean BCVA was 20/27 after a follow-up
of six months.
Postoperative refractive sphere was -0.4 D and astigmatism did not
change according to the preoperative level.
In addition, near visual acuity was 20/25 without correction and
20/27 with best correction for distance. All achieved a BCVA for
near of 20/20 or better with mean add of 1.9 D, Dr Alió reported.
"We got the A constant to target at about -0.5 D of final refractive
sphere. At this point, the predictability of the refraction was
"But we did have a surprise finding in the good near visual
acuity achieved with BCVA. This lens probably provides some accommodation
and this needs to be confirmed because it may be an additional advantage
of this technology," he said.
Implantation of the lens did not appear to induce any astigmatism.
In fact, the cylinder was slightly lower but without reaching significant
In addition, there was no difference in contrast sensitivity in
the eyes implanted with the ThinOptX lens and that of their fellow
eyes, which were implanted with a conventional acrylic IOL.
The patients included three men and three women with LOCS 3 classification
senile cataracts. All had normal axial lengths and normal keratometry.
Patients underwent micro-incision cataract surgery with the Dodick
Laser PhotolysisTM system.
The mean incision size was 1.6 mm; mean power of the lens 18.83
D; and the A constant was 118.84, he noted.
"Incision size is inversely correlated with surgical control.
With micro-incision cataract surgery, we create a much more controllable
environment. To make this surgery possible we need to have a separation
of irrigation and aspiration and work with both hands at the same
"We need lasers to reduce the trauma to intraocular structures.
And finally we need new IOL technology so that surgeons performing
these procedures will not need to enlarge the wound," Dr Alió
The ThinOptX lens is manufactured in such a way that while the anterior
surface has a continuous curvature like a conventional lens, the
posterior surface is divided into steps which serve to focus all
the rays on a single point, thereby eliminating spherical aberration.
The manufacturers assert that the lens is not a diffractive Fresnel
lens, but rather should be termed a diffractive lens.
"The optical quality of this lens has been studied and modulation
transfer function (MTF) and other optical variables have been analysed.
"This really proves this lens provides adequate optical quality
to match the standards of current IOLs, something that corresponds
to our preliminary clinical results," Dr Alió explained.
The means by which the lens appears to afford patients accommodation
remains somewhat a mystery, Dr Alió noted.
Ultrasound biomicroscopy images of the lens show that it bends slightly
forward at least at the early postoperative period up to the third
month which might account for the good near visual acuity with best
correction for distance.
William Callahan, one of the designers of the lens, suggested an
alternative theory which is that the accommodative effect results
from the greater depth of field the lens achieves.
Dr Alió noted that in his first few implantations, he rolled
the lens prior to implantation with his fingertips.
Since then, ThinOptx manufacturers have developed a new folding
and insertion device enabling surgeons to roll the lens instrumentally
and which he now uses.
"We now have a lens we can implant through a 1.4 mm incision.
The new improvements in rolling technique with the ThinOptX lens
will further promote its use in cataract surgery," Dr Alió