EyeNet Magazine


 
Clinical Update: Cataract
Iatrogenic Cataract: The Problem Caused by a Solution
By Laura J. Rongé, Contributing Writer
 
 

First, do no harm. Those words embody the long-standing dismay with which Medicine regards iatrogenic problems; that is, problems inadvertently created by well-intentioned medical treatment.

A number of ophthalmic surgical procedures and medications can precipitate the development of cataracts, necessitating the replacement of the lens. And, unfortunately, “No technology that we have available to date comes close to matching the vision of the accommodating crystalline lens,” said Randall J. Olson, MD, professor and chairman of ophthalmology and visual sciences, and director, John A. Moran Eye Center, University of Utah, Salt Lake City.

When Treating One Trouble Creates Another

According to David F. Chang, MD, the leading causes of iatrogenic cataract include medications, radiation and prior intraocular surgery, including vitrectomy, trabeculectomy, penetrating keratoplasty and peripheral iridectomy. “Another new cause of iatrogenic cataracts is phakic IOLs,” said Dr. Chang, clinical professor of ophthalmology at the University of California, San Francisco, and in private practice in Los Altos, Calif.

Steroid therapy. “I would say 95 percent of the cases of iatrogenic cataracts that I see are caused by the overuse of topical steroids. Intraoperative and systemic steroids are also a problem,” Dr. Olson said.

Mark Packer, MD, agreed. “Cataracts certainly occur with topical steroid use, for example, in cases of prolonged application for the treatment of uveitis. I have also seen posterior subcapsular cataracts caused by topical steroids prescribed for blepharitis and allergic conjunctivitis.” Dr. Packer is clinical assistant professor of ophthalmology, Oregon Health & Science University, Eugene.

Dr. Chang added, “A newer cause of steroid cataracts is the use of intravitreal triamcinolone injections for retinal problems.”

Cataract prevention becomes more difficult when physicians outside ophthalmology prescribe steroid medications. “You often see posterior subcapsular cataracts in patients taking oral steroids for pulmonary problems or arthritis,” explained Monica L. Monica, MD, PhD, in private practice in New Orleans.

Dr. Olson added that oftentimes primary care physicians prescribe steroid medications for patients with allergies or asthma without completely understanding the repercussions these medications can have. He cited his own case as an example. “I have taken inhaled steroids long-term for asthma and nasal decongestion. I worry that I could develop a cataract and/or glaucoma someday as a result of this. I did not understand the risk because the prevailing wisdom was that there was no systemic impact from the dose I was on. Now the risk is clearly not zero but is still poorly understood.”

Phakic IOLs. There is no question that posterior chamber phakic IOLs can cause cataracts, according to Dr. Olson. Complicating matters, the patients most likely to get these implants are young high myopes, he explained.

“If they need cataract surgery, they are most at risk for retinal detachment. That is to say, the most likely candidates for these devices are also the patients with the highest risk for complications. I am waiting to see what happens with this technology,” Dr. Olson said. He pointed out that anterior chamber and iris-supported phakic IOLs seem to do better, “but even with these, it is too early to tell the long-term effects.”

Dr. Packer reported that with the iris-supported Verisyse phakic IOL (AMO), the incidence of cataract surgery was 1.3 percent.

With the V4 ICL (Staar Surgical) it was 0.9 percent. The incidence of anterior subcapsular opacification with the ICL was 2.2 percent. Both of these phakic IOLs have been approved by the FDA for patients with high myopia.

Dr. Olson pointed out, however, that “when it comes to induced cataract, five years’ worth of data is considered short-term. We just don’t know yet.”

What we do know, according to Dr. Packer, is that “cataract is a well-recognized complication of phakic IOL implantation and should be discussed with all candidates.”

Intraocular surgery. Vitrectomy is the most common cause of iatrogenic cataract in Dr. Chang’s practice. “The incidence is essentially 100 percent,” he said.

“One theory is that higher oxygen levels near the crystalline lens induce a nuclear cataract. With vitreous syneresis, or after vitreous removal, the lens has much greater exposure to oxygen levels from the choroid, and this induces nuclear sclerosis.”

Dr. Packer noted that he removed a cataract from a relatively young, active general surgeon who had developed dense nuclear sclerosis after a vitrectomy.

“The vitrectomy was performed for a posterior vitreous detachment. The floater became intolerable to her when she was performing surgery. We had an interesting discussion about IOL choice. Eventually she decided on a monofocal IOL with a target refraction of –0.75 D,” he said.

An antioxidant treatment may soon be available to prevent cataracts after vitrectomy. The drug, OT-551 (Othera Pharmaceuticals), is a topical eye drop that entered phase 2 clinical trials last year.1

Dr. Packer noted that the rate of cataract after trabeculectomy for glaucoma is also very high. He noted that one study reported a 24 percent incidence of cataract after trabeculectomy in young patients.2

What About LASIK?

Can LASIK cause cataracts? Ironically and unfortunately, the reverse may be true. According to Dr. Packer, “Cataracts have actually been reported to cause LASIK!”

He cited a study of five patients with oil-drop cataracts. The study noted that ophthalmologists had missed the underlying lenticular cause of myopic regression after LASIK in these patients. As a result, the patients were scheduled for or had had LASIK enhancement before presenting to the study authors.3

Dr. Packer reported that he, too, has performed cataract surgery for a patient who had two LASIK enhancements for “myopic regression.”

The patient had dense nuclear sclerosis. “The patient told me that he suspected the cataract was developing prior to the first enhancement. Of course, the history of LASIK made his IOL calculations problematic. He achieved 20/30 uncorrected acuity at distance and near with a Crystalens implant,” Dr. Packer said.

According to Dr. Olson, cataract can occur after complicated LASIK, although “I think the numbers are low, certainly less than 1 in 10,000.”

Dr. Monica added, “We have not seen cataracts developing soon after LASIK. We do have patients who have had cataract surgery 15 years later after LASIK.”

When the First Problem May Justify the Second

Even given a clear risk of inducing an iatrogenic cataract, overriding medical priorities may justify it.

Dr. Chang explained it this way: “In most cases, iatrogenic cataracts are caused by medical or surgical treatments for serious ocular or general medical problems. Cataracts can be eliminated with surgery, so the risk of cataract development usually is not a contraindication to the primary treatment, such as prednisone for asthma, or vitrectomy for macular hole.”

He noted, “One exception is elective phakic IOL refractive surgery, which is usually performed in high myopes. Because cataract surgery increases the incidence of retinal detachment, the risk of iatrogenic cataract in this population of other-wise healthy eyes is more onerous.

“If I were choosing a phakic IOL for a high myope, I would prefer the one that has the lowest risk of iatrogenic cataract. To me, this would be a much more important consideration than, say, incision size, said Dr. Chang.

“We certainly need more long-term studies in order to better quantify and compare the relative cataract risk of different phakic IOL models,” he said.

“Any time one operates on a phakic eye, one must be cognizant of the risk of cataract,” Dr. Packer said. “Informed consent for surgical procedures on phakic eyes must include the risk of cataract and the potential complications of cataract surgery, such as the potential increased risk of retinal detachment in high myopia.”

If the well-informed patient opts for a procedure, then “meticulous surgical technique may help to reduce the risk, particularly in phakic IOL implantation,” Dr. Packer said.

Cataract as Usual, Unless It Isn’t

When iatrogenic cataracts make an appearance, the diagnostic considerations are usually no different than they would be if the cataract occurred naturally, according to Dr. Chang. “One exception would be the rapid development of a mature white lens following vitrectomy surgery,” he said. “In this situation, one must suspect a surgical violation of the posterior capsule.

“In general, eyes that have undergone vitrectomy are more likely to have weak zonules, and a greater likelihood of lens-iris diaphragm retropulsion syndrome,” he said. In any case, ophthalmologists share with all physicians the risk of iatrogenic effects: the problems induced by solutions.

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1 EyeNet 2006;10(2):15.

2 Adelman, R. A. et al. Ophthalmology 2003;110(3):625–629.

3 Soong, H. K. J Cataract Refract Surg 2004;30(11):2438–2440.

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Dr. Chang reports financial interests in AMO, Visiogen, Cataract & Refractive Surgery Today, Slack and Alcon. Dr. Monica has no related interests. Dr. Olson reports interests in Allergan, AMO, Calhoun Vision and Becton-Dickson. Dr. Packer has received travel, research and honoraria funds from Eyeonics, Staar Surgical and Alcon, and he has consulted for AMO and Advanced Vision Science.

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