The most common complication of cataract surgery is opacification of the
posterior capsule, typically due to proliferation of lens epithelial cells.
This results in decreased vision for the patient because the visual axis is no
The Nd:YAG laser, which uses a neodymium:yttrium-aluminium-garnet
crystal as the active laser medium, allows ophthalmologists to safely and
effectively address posterior capsule opacification by performing a posterior
capsulotomy. The Nd:YAG laser can also help adjust the position of the IOL
implant and effect a change in the refractive state of the eye.
PCO occurs in 20% to 50% of patients who undergo cataract surgery, and
it can occur anytime from months to years after the initial surgery. Certain
lens implant designs, such as those with square edges, have a lower incidence
of PCO because the edge helps to prevent migration of lens epithelial cells
toward the visual axis.
The Nd:YAG laser is used to punch small openings in the posterior
capsule that can be connected to form a larger opening. While the laser
capsulotomy is a noninvasive and safe procedure, there are potential
complications, such as retinal detachment, acute spikes in IOP, inflammation
and pitting of the lens optic.
|PCO can be addressed using the
YAG laser to perform a capsulotomy to clear the visual axis. The inset picture
shows the appearance prior to the treatment with an opacification leading to a
decrease in vision to the 20/60 level. After the treatment, the cleared visual
axis results in an improvement of vision to 20/20 within minutes.
Images: Devgan U
|The small capsulorrhexis in
this patient has led to capsular phimosis that has pushed and tilted the
Crystalens optic posteriorly, inducing a hyperopic shift and refractive
astigmatism. Using a YAG laser to release the tension on the anterior capsular
rim by making relaxing incisions at the cardinal meridians can help to
reposition the lens and improve vision.
|Fibrotic bands along the
posterior capsule have shifted the lens optic anteriorly and induced optic
tilt, resulting in induced myopia and astigmatism. Using the YAG laser to open
the posterior capsule and release the tension along the fibrotic bands will
help to flatten the lens and return it to a more appropriate position in the
eye and improve vision.
Using the Nd:YAG laser to make a circular pattern in the posterior
capsule avoids the risk of pitting the optic in the central visual axis;
however, it can create a large floater. Applying the Nd:YAG laser spots in a
cruciate or radial pattern may minimize the risk of a large floater, but
careful aiming of the laser is required to avoid pitting the center of the lens
optic. While minor pitting of the lens optic goes unnoticed by patients,
multiple pits near the center of the optic can result in degradation of the
Modulating lens position
As the PCO progresses, fibrosis of the capsular bag can occur and the
lens implant can shift out of its original position. Lenses that are
accommodating in nature, such as the Crystalens (Bausch + Lomb), are more
flexible and may shift or tilt within the capsular bag, inducing a change in
the refractive state of the eye. Modulating the lens position and refraction
using the Nd:YAG laser is an important part of achieving good results with the
A tilt of the lens optic can induce refractive astigmatism. This can be
measured be comparing the cylinder of the refraction to the corneal
astigmatism. Significant refractive astigmatism in the absence of cornea
astigmatism can indicate a tilt of the optic. Capsular phimosis or contraction
of the anterior capsular rim can cause the lens to be shifted posteriorly in
the capsular bag, which induces a hyperopic shift to the refraction. Using the
Nd:YAG laser to perform relaxing incisions of the anterior capsular rim can
release the tension of the phimosis and allow the optic to return to its
appropriate position, bringing the refraction closer to plano. Fibrosis of the
posterior capsule can cause the lens optic to be pushed anteriorly, resulting
in a myopic shift to the refraction. In this case, releasing the tension of
these fibrotic bands via a posterior capsulotomy can aid in returning the optic
to a more appropriate position away from the iris, again bringing the
refraction closer to plano. Initial energy levels should be low, starting at
about 1 mJ and titrating upward as needed. Judicious use of the Nd:YAG laser
should be employed because it is relatively easy to bring the patient back for
further treatment, but once laser shots are placed into ocular tissue they
cannot be undone.
By carefully applying the Nd:YAG laser we can improve the vision of our
cataract surgery patients by clearing the visual axis as well as modulating the
position of the lens within the capsular bag.
- Uday Devgan, MD, FACS, is in private practice at Devgan Eye Surgery
in Los Angeles, Beverly Hills and Newport Beach, Calif. He is also chief of
ophthalmology at Olive View UCLA Medical Center and associate clinical
professor at the UCLA School of Medicine. Dr. Devgan can be reached at 11600
Wilshire Blvd., Suite 200, Los Angeles, CA 90025; 800-337-1969; fax
310-388-3028; e-mail: firstname.lastname@example.org;
website: www.devganeye.com. Dr
Devgan is a consultant to Bausch + Lomb and other ophthalmic companies but has
no direct financial interest in any of the products mentioned.