Crystalline lens dislocation

Example of a dislocated IOL (in the bag nasally-left side and temporal side through the capsular rent); crystalline lens dislocation also can be a problem due to trauma, spontaneous dislocation, and now possibly because of argon laser iridotomy
Source: S. Holtz, M.D.

Facts—old and new—about crystalline lens dislocation

The crystalline lens has traditionally dislocated due to trauma, spontaneous dislocation, and for hereditary reasons

Argon laser iridotomy might cause lens dislocation in special circumstances

Specifically, intermittent pupillary block along with angle closure could weaken the iris and ciliary body. Laser iridotomy treatment could nonetheless cause further zonular damage, creating the conditions for lens dislocation

Source: Myoung Joon Kim, M.D.

Historically, the crystalline lens has dislocated due to trauma, spontaneous dislocation, and for hereditary reasons. New evidence suggests another possible reason: argon laser iridotomy.
For now, Myoung Joon Kim, M.D., Department of Ophthalmology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea, and colleagues report a single case of anterior dislocation of the crystalline lens after argon laser iridotomy.
But the case falls on the heels of other similar reports, suggesting the potential for argon laser iridotomy to cause such a problem should not be ignored.
“Kawashima et al. report a case of spontaneous anterior lens dislocation that developed in a patient with a history of uneventful laser iridotomy for narrow-angle glaucoma,” Dr. Kim noted in his study, published in the January 2009 issue of the Journal of Cataract & Refractive Surgery. “Kwon et al. report bilateral spontaneous anterior lens dislocation in a patient with retinitis pigmentosa who was treated with laser iridotomy. The lens dislocations developed after uneventful laser iridotomy, as in our case.”

What happened

This case study reports that a 55-year-old Korean woman presented with decreased visual acuity in the right eye and ongoing headaches. After examination, she was diagnosed with angle closure glaucoma. Uneventful argon laser iridotomy was performed in both eyes.
“With its decreased risk for hemorrhage and corneal endothelial cell loss, argon laser iridotomy was used rather than neodymium:YAG (Nd:YAG) laser iridotomy because of the patient’s thick brown irides,” Dr. Kim noted.
Ten months after the operation, the patient once again had decreased vision in the right eye. “On slitlamp examination, a clear crystalline lens was seen in the anterior chamber,” Dr. Kim reported. “The laser iridotomy was patent at the 10:30 position. There was pupillary peaking at the 11:30 position due to the zonular fibers, which were still attached to the crystalline lens.”
Physicians realized there was nothing ordinary about this case. “Our case is unique in that the patient did not have a history of trauma, a systemic disease associated with lens dislocation, or a family history of lens dislocation,” Dr. Kim noted.
Instead, Dr. Kim suggested that intermittent pupillary block and angle closure “induces a mid-dilated pupil with weakened iris and ciliary body and could result in zonular laxity.”
Then, the additional zonular damage via laser iridotomy could have caused the lens dislocation, Dr. Kim reported. In other words, the lens likely was subluxed due to progressive zonular dehiscence, Dr. Kim suggested.
In this case, cataract surgery along with anterior vitrectomy was the solution, yielding a good result: BCVA of 20/20 by one month post-op—a result that was maintained through the last examination at two years.
“The use of a 2.75 mm incision decreased the risk for expulsive hemorrhage and postoperative corneal astigmatism,” Dr. Kim reported. “The corneal endothelium was protected by performing the intracapsular phacoemulsification through a small anterior capsulotomy and using an OVD.”
Although this research may be helpful to some, Mohan Rajan, M.D., medical director, Rajan Eye Care Hospital, Chennai, India, suggested that argon lasers are out of fashion.
“They produce slightly more heat and don’t penetrate the iris,” Dr. Rajan said. “They only flatten the iris. Subsequently you have to use a YAG laser to make an opening in the iris. The argon laser is not a good one.”
There also is potentially more damage of the crystalline lens using an argon laser, he said.
“We used to use the argon laser a long time ago to flatten the iris or thin the iris and in the central area use the YAG,” Dr. Rajan said. “Now we only use the YAG laser.”
As a result, Dr. Rajan suggests the research may have minimal implications in the world of iridotomy.
Nonetheless, Dr. Kim did mention the thick brown irides of this patient would have posed a problem for the YAG laser.
A report in the January 2008 issue of the British Journal of Ophthalmology offers a third opinion.
“A YAG laser reduces the amount of thermal injury caused by ALI [argon laser iridotomy] to the overlying cornea,” according to Ian C. Francis, F.R.A.N.Z.C.O., Department of Ophthalmology, Prince of Wales Hospital, Randwick, Australia, and colleagues. “Nevertheless, the application of YAG laser alone in dark irides is also not without side effects, as the energy required increases the risk of iris haemorrhage. However, this is a minor complication and is almost always controlled by pressure on the laser contact lens.”
Other research, meanwhile, has found that sequential argon laser and YAG laser iridotomy in dark irides is safe and efficacious.

Editors’ note: Drs. Kim and Francis have no financial interests related to their studies. Dr. Rajan has no financial interests related to his comments.

Contact information

Francis: iancfrancis@gmail.com
Kim: joon@amc.seoul.kr
Rajan: +65 6254 6330, rajaneye@vsnl.com