Does cataract surgery somehow worsen AMD? The answer to this controversial question depends on which study you believe. For every study that finds a correlation between cataract surgery and progression of AMD, you can find another that doesn’t—or at least admits to uncertainty.

The Debate Continues
Evidence gleaned from small case series and large epidemiological studies offers conflicting opinions. The earliest reference to this question, which appeared in 1996, cited an association between surgery and progression.¹ A more recent reference, presented last fall by the Age-Related Eye Disease Study (AREDS) group, found little or no relation.²

“We cannot make a definitive statement that cataract surgery does or does not accelerate progression of AMD,” said retina specialist George A. Williams, MD, chairman of ophthalmology at William Beaumont Hospital in Royal Oak, Mich.

Steven T. Charles, MD, agreed. AMD is a common cause of vision loss in persons over 65, and cataract surgery is one of the most frequently performed surgical procedures in the world, noted Dr. Charles, clinical professor of ophthalmology at the University of Tennessee. “By chance alone, X number will have worsening after cataract surgery.”

Many of those who hold to the belief that there is little or no association argue that the vision loss attributed to the cataract was really due to AMD. For instance, the AREDS report says, “It is especially difficult in these studies to rule out the possibility that early retinal changes causing some vision loss were not the reason for the cataract surgery.”

Caption: If a connection between cataract surgery and AMD
progression does exist, what’s the causal link? Theories include
hypotony, inflammation and blue light.

As Dr. Charles pointed out, the cataract often prohibits sufficient view of the macula preoperatively to determine if AMD is present. What’s more, angiography or optical coherence tomography is not likely to be performed before surgery, since most cataract surgery patients are not examined by
a retinal specialist.

Dr. Williams deals with this situation regularly. Patients will tell him that after cataract surgery their vision is no better. “I say, ‘That’s because you have macular degeneration.’ They say, ‘I didn’t have macular degeneration before I had my cataract.’ It’s clear [that] they had macular degeneration long before they had the cataract surgery,” he said, adding, “That’s a communication problem.”

Data Update
The first report of a possible association came out of Israel when researchers reported that AMD progression occurred more often in eyes that underwent cataract surgery than in control eyes.¹ But the study was small. What’s more, the 47 patients underwent extracapsular cataract extraction, not phacoemulsification. “One could question whether it’s applicable in the phacoemulsification era,” Dr. Williams said.

In 2003, a group in Scotland reported no increased risk of progression of maculopathy in patients with mild and moderate degrees of AMD. Moreover, one year postoperatively, quality of life benefits were maintained.³

In the meantime, a number of epidemiologic studies have proved just as conflicting as the reported case series. Data extracted from the Beaver Dam Study suggest that eyes that had undergone cataract surgery were more likely to have progression of AMD after five years. But there are concerns about whether the results from this relatively homogenous population can be extrapolated to the general population.

On the other hand, neither the Blue Mountain Eye Study nor the Rotterdam Eye Study showed any association.

“Basically, the large epidemiologic studies are not consistent in showing any association,” Dr. Williams said. “For every one that does show an association, one doesn’t.”

For now, Dr. Williams finds the conclusions teased from the AREDS data to be most compelling. The AREDS data show that cataract surgery, as a time-dependent covariate, does not appear to significantly accelerate progression to neovascular AMD among persons at moderate risk for progression. (The study did, however, find a possible increased risk of marginal statistical significance in the development of geographic atrophy following cataract surgery.)² 

The AREDS research group argues that other studies looking for a risk association lack reliable information regarding the preoperative status of the retina. “It is especially difficult in these studies to rule out the possibility that early retinal changes causing some vision loss were not the reason for the cataract surgery,” the group states. That is one reason Dr. Williams, a member of the study group, prefers the AREDS data set to others. Other strengths include its well-defined AMD population and the detailed follow-up over a long period of time (6.15 years).

Theoretical Links
Even those who believe that a connection may exist do not understand its theoretical framework. Several theories have been posited to explain why cataract surgery might exacerbate AMD:

Hypotony. One hypothesis suggests that when the eye is opened during cataract surgery, the pressure lowers for a few minutes, causing possible bleeding in patients with neovascularization. But hypotony is not a problem with current cataract surgery. 

Inflammation. Another theory suggests that the eye becomes inflamed after cataract surgery, and that somehow the inflammation reaches the back of the eye.

Blue light. Then there is the theory that blue light exposure may accelerate AMD following cataract surgery. This hypothesis might have the most credence given that it has led to the development and marketing of IOLs that absorb blue wavelengths. The idea is that the human lens, as it becomes more yellow in color with age, filters ultraviolet radiation and reduces the amount of blue wavelength light that reaches the retina, which is susceptible to blue light damage. While lens implants filter UV light, most fail to block the visible blue wavelengths.

What to Do
So where does all of this conflicting evidence leave the clinician? “The data suggest there is no compelling evidence that cataract extraction aggravates visual loss. But this needs to be discussed with patients prior to removal of the cataract,” Dr. Williams said. He advises physicians to have a detailed discussion with their patients before surgery about the natural history of macular degeneration so that they understand that even with successful cataract surgery it is possible that AMD progression will occur.

“Ophthalmologists should consider cataract surgery in patients with macular degeneration in whom they believe the cataract is consistent with functionally significant visual loss,” Dr. Williams said. “Although we cannot be absolutely certain at this time, the best data suggest that there’s no compelling reason not to perform cataract surgery when it’s visually indicated.”

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1 Pollack, A. et al. Ophthalmology 1996; 103(10):1546–1554.
2 AREDS data presented at Retina Subspecialty Day, Nov. 15, 2003, Anaheim, Calif.
3 Armbrecht, A. M. et al. J Cataract Refract Surg 2003;29(4):686–693.

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Dr. Charles is a consultant for Alcon. Dr. Williams has no related financial interests.

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Yellow-Tinted IOLs?

If you accept the theory that blue light is harmful to the retina and accelerates the progression of AMD, does it make sense to use yellow-tinted IOL rather than a clear lens? Two companies—Hoya (in Japan) and Alcon—have introduced lenses intended to mimic the natural yellowing of the aging lens, which filters blue light.
    
Janet Sparrow, PhD, a retinal cell biologist who studies the effect of blue light on the retina, says that it’s not been proven that the association between cataract surgery and AMD progression (if one exists) is due to an increased postsurgical exposure to blue light. “Blue light may be an important factor, but we haven’t shown it yet,” said Dr. Sparrow, associate professor of ophthalmic science at Columbia University.

Samuel Masket, MD, a cataract surgeon, finds Dr. Sparrow’s lab studies “suggestive and intriguing.” But whether they “correlate to the long-term clinical situation regarding AMD is unknown at this time,” said Dr. Masket, clinical professor of ophthalmology at the University of California, Los Angeles. He added that there is some evidence of benefit to yellow-tinted lenses with respect to contrast sensitivity function.

In Dr. Masket’s view, appropriate studies regarding risks and benefits of yellow-tinted IOLs have yet to be performed. In the meantime, he remains “neutral on the natural,” a reference to Alcon’s Acrysof Natural IOL.

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Dr. Masket is a consultant for Alcon.