Laser capsulotomy techniques address opacification
Careful application of Nd:YAG laser helps position the lens within the capsular bag and improve vision.
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 longer clear.
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.
Images: Devgan U
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 vision.
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 Crystalens.
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.