Pushing the Boundaries of Refractive Surgery
Conversations with refractive surgeons who have “the right stuff.”
Nearly 50 years ago, when President Kennedy announced his intention to land a man on the moon within a decade, he famously preempted critics who might question the wisdom of the Apollo program by saying that Americans choose to tackle such high-stakes challenges “not because they are easy, but because they are hard.”
Enthusiastically accepting a challenge, and marshalling the intellectual and technological resources to overcome it, is quintessentially American, Kennedy argued, “because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win.”
Have refractive surgeons, in effect, landed a man on the moon yet? Many of the patients who now see 20/16 uncorrected might say so. Treating the garden-variety 4 D myope has indeed been mastered with NASA-like precision. But the plenitude of poor candidates who are dissuaded from refractive surgery each year suggests frontiers still open for exploration. We asked several refractive surgeons for their approach to less-than-ideal patients, those who may be well-served by corrective lenses but the surgeon takes on anyway — “not because they are easy, but because they are hard.”
Making the Keratoconus Call
Robert Maloney MD, a private practice refractive surgeon from Los Angeles, defines a challenging case as any in which he is unsure of the outcome. At the top of his list is a preop evaluation showing a slightly irregular corneal topography. “Does that patient have keratoconus or not? It's often a very difficult call to make,” says Dr. Maloney, who describes it as the most-frequently encountered refractive surgery challenge.
Karl G. Stonecipher, MD, of Greensboro, NC, agrees that patients with abnormal corneas and those with forme fruste keratoconus present tough judgment calls for the surgeon. He says collagen crosslinking, a treatment not widely available in the United States, may someday provide help by stabilizing the cornea. The treatment can be combined with the Intacs corneal implant, says Brian Boxer Wachler, MD, also of Los Angeles. At that point, he checks the patients best-corrected visual acuity. “If it's 20/30 or 20/25, or 20/20 even, maybe 20/40, then I'll consider doing a Visian ICL,” he says.
The Mixed Astigmat
According to Dr. Stonecipher, the mixed astigmatic patient is one of the most significant refractive surgery challenges. “There's the challenge of registration,” he explains, with different laser makers offering different packages for trying to improve that layer.”
The greater the astigmatism, the more influence it has on the spherical equivalent outcome, he says. Even patients who start with a spherical equivalent of zero and a refractive error of-1/+2 or −2/+4 must turn out zero at the conclusion of surgery without any astigmatism, says Dr. Stonecipher. If a surgeon can eliminate a patient's astigmatism entirely, but his refraction ends up a −1 or a +1 after the procedure, the surgeon will learn that a big challenge still remains.
“The patient says, ‘OK, I paid you all this money and I still can't see,’” Dr. Stonecipher explains. “In my patient's mind, an enhancement is a failure of the procedure.”
For these patients, he says there are three surgical options: (1) a surface treatment such as a transepithelial PRK, (2) relifting the flap, with its attendant risks, and doing a refractive error treatment, or (3) doing a customized wavefront treatment for those patients who come out of the initial procedure with low higher-order aberrations (HOAs).
According to the surgeons we spoke with, these retreatments after a previous refractive procedure constitute another of the most challenging refractive surgery cases.
Fixing Previous Refractive Surgery
Some of the most challenging cases are the result of previous refractive procedures. These include radial keratotomy (RK) and astigmatic keratotomy (AK), as well as LASIK. With patients who have had these procedures in the past, “It's all crazy refractive errors,” says Mitchell A. Jackson, MD, of Lake Villa, 111. The most demanding problem, he says, is dealing with irregular astigmatism.
“That's probably the most challenging, when you have someone come in with irregular astigmatism and it's not from keratoconus.”
Dr. Jackson points out that solutions for surgically induced irregular astigmatism are currently limited in the United States. The topography-driven surface treatments that he favors are not yet available domestically. In the meantime, he recommends correction with gas-permeable contact lenses as the first line of treatment. Alternately, clinicians can try a soft toric lens, but Dr. Jackson notes that gas permeable lenses give better vision.
Partly because of the risk involved in recutting flaps, Dr. Maloney says he will do LASIK on an individual patient just once. “If they're still not right, I then do a PRK retreatment,” he says.
Other problematic astigmat cases, according to Dan Durrie, MD, of Overland Park, Kan., are ones in which the axis of astigmatism was flipped in his original survey refractive surgery. “Instead of getting rid of the astigmatism, the surgery doubled the patient's astigmatism.”
For cases such as these, close communication with the patient is necessary. Dr. Durrie says that he does not perform LASIK on previous RK or AK patients. He, too, recommends PRK surface ablation. And because some RK patients are about cataract patient age, an IOL may ultimately be the preferred solution.
Postop corneal ectasia is a challenge refractive surgeons still confront, though Dr. Jackson believes they will encounter it less over time. “The criteria we use now, we didn't use back in the day, 10 years ago,” he says. Improved screening and advancements in surgical technology and technique have cut down on its incidence, he says.
To deal with the relatively few cases that do occur, implanting Intacs is the best option, Dr. Jackson says. He notes that collagen crosslinking shows promise for the treatment of ectasia in FDA clinical trials, but is not available for US patients who have undergone previous refractive procedures. “You can't get in to the clinical trial if you've had previous surgery done on your eye,” he explains. “It has to be a virgin keratoconus eye.”
When addressing glare and halos following LASIK, often the result is from a too-small optical zone with the laser. Dr. Boxer Wachler recommends a wavefront-guided optical zone enlargement using PRK. “It works very well at reducing the higher-order aberrations,” he says. “I say ‘reduce,’ not ‘eliminate’ the HOAs, because it's not often that we can eliminate them.”
Reduction, however, is possible, and according to Dr. Boxer Wachler, that's usually enough to satisfy patients with glare or halo improvement.
High Hopes for High Myopes
Myopes from approximately -8 to -10 D provide their own challenges. And many refractive surgeons increasingly agree that they are best met with phakic IOLs.
“My personal feeling is that above 10 D, implantable lenses are always better,” says Dr. Maloney. And for slightly lower myopia, from 8 D to 10 D, he favors them as well. “I really like phakic IOLs in that range because they are more accurate than LASIK and give better night vision,” he says.
An informal survey of community-based refractive surgeons, done at the 2009 ASCRS meeting by Dr. Stonecipher, shows that they are only slightly more hesitant to choose phakic IOLs than Dr. Maloney. While only 2% chose them to treat myopia of 7 D to 9 D, that number grew to 65% when it came to myopia of 9 D to 12 D.
According to Dr. Stonecipher, when deciding between a laser correction and a phakic IOL, certain questions must first be addressed. “Does the person have a thick enough cornea for a laser procedure?”And if they have a thick enough cornea, is it a regular cornea?”
Should the surgeon decide to go with laser correction, Dr. Jackson warns the patient must be willing to accept the possible need for residual correction after surgery. “Hopefully the expectation was set ahead of time that you told them they had a limited amount of tissue,” he says. For these cases, he too regards phakic IOL as the preferred procedure — or cataract surgery.
What About Autoimmune Patients?
If you're ambivalent about operating on patients with autoimmune disorders, you are not alone. When Dr. Stonecipher surveyed his ASCRS audience on whether they would perform refractive surgery on those with diagnosed arthritis who were taking a systemic immunosuppressant, only 10% answered “yes.” Twenty-seven percent answered “no,” but the majority (63%) answered “sometimes.”
The surgeons we spoke with seemed to fall squarely in the category of, “Sure — if the conditions are right.”
Dr. Jackson says that for these patients, he does a careful slit lamp evaluation that includes lissamine green staining, tear break-up time and Schirmer's testing. “I always talk to the patient's rheumatologist or internist who's managing the autoimmune disease,” he continues. “If they say the disease is very stable, and the patient has no ocular findings preop, then I'll operate.” Because these patients have a higher risk for developing dry eye after surgery, he puts them on Restasis pre-emptively.
Under these conditions, when patient's autoimmune disease is “well-controlled,” Dr. Maloney agrees, refractive surgery is safe. In a paper he wrote reviewing the outcome of LASIK in 94 eyes of autoimmune patients, he saw no incidence of corneal melting.
Dr. Boxer Wachler, however, will not perform PRK in these patients. The risk of corneal melting is too great, he believes. “For these patients, it would either be LASIK, or, depending on the autoimmune disease in question, a phakic IOL.”
He also urges surgeons to remember to counsel these patients that they are at risk for dry eye after any surgery. “That has to be part of the informed consent discussion,” Dr. Boxer Wachler says.
HSV Considerations
Many surgeons remain wary of surgical procedures in patients with a history of HSV. In Dr. Stonecipher's survey on the topic, 58% responded that they would not perform a refractive procedure on these patients. Only 16% answered “yes,” while 26% answered “depends what type.”
While once these patients could not have undergone a refractive procedure, Dr. Stonecipher says, modern antivirals and antibacterials have changed that. “Although not every patient can be treated, some can,” he says, such as patients with a ‘soft’ history of whether it actually was herpetic or not, or those with corneal scarring from a successfully-treated bacterial or fungal ulcer who require correction of residual refractive error.
Dry Eye Dilemmas
Dry eye patients are another group that can successfully undergo refractive surgery, provided it is treated prior to surgery. “You don't want to operate on someone who doesn't have good tear film and good Meibomian gland function,” says Dr. Durrie. “You treat them and see them back; if they're not under control, you get them under control.”
Dr. Jackson believes that advancements in treatment and diagnosis of dry eye syndrome means that it is much easier to get control of the problem before surgery and keep it from worsening. And if the patient's dry eye is contact lens related, refractive surgery will help their problem. “Usually contact lenses are like sponges and just soak up tear film,” he points out.
Dr. Maloney is cautious about patients who have been diagnosed with significant dry eye preoperatively He says he is far less likely to recommend LASIK in that circumstance. Further, a study he conducted found no evidence that PRK reduces the risk of dry eye as compared with LASIK. “We compared the incidence after PRK and LASIK in more than 1,000 patients, and it was exactly the same. If they have significant dry eye, I lean toward a phakic IOL, refractive lens exchange, or no surgery at all,” says Dr. Maloney.
Surgeons caution that dry eye patients do need careful counseling beforehand. Dr. Durrie advises making sure that patients know that the dryness is a problem that existed before the surgery. “I think of LASIK as being kind of a stress test for dry eyes, because we're going to cut across the nerves and we're going to make it a temporarily more difficult environment,” he says. If the ocular surface is already compromised, “that stress test can get to the point where it gives them a lot of symptoms.”
The Final Frontier
The need to provide careful counseling to patients that tempers optimism with a frank discussion of potential adverse outcomes may be the most significant challenge in refractive surgery, no matter what the procedure or how straightforward the refractive error.
“I think most doctors now have realized that they need to spend a lot more time than they originally thought with the patient before surgery,” Dr. Durrie says. The investment greatly boosts a procedure s chance of satisfying the patient. “When I'm teaching residents and fellows, I want them to understand that the challenge is 95% figuring out what to do and 5% doing it.”
Presbyopic patients offer a perfect illustration of this principle. Dr. Durrie notes that surgeons don't currently have an “ideal” presbyopia correction procedure. While there are good ones, they absolutely require patient education. Monovision and blended vision patients can do very well, but first they must go through a period of adaptation, so it is crucial they understand that that is coming. Dr. Maloney reports that he has patients undergo a contact lens trial for monovision for a couple of days before he will do the surgery.
Dr. Jackson agrees that strong communication with the patient is critical. “You've got to find out what the patient's needs are,” he advises. “Find out what their jobs and hobbies are.”
Low myopes who remove their glasses to read can be miserable after what otherwise seems to be a successful LASIK procedure because they can no longer do that. To avoid this, the surgeon needs to inform the patient that he or she will function with glasses on for up close.
“With these patients, you have to pick and choose,” Dr. Jackson says. “You can always tell them that there's a lens implant technology that's coming and that will be even better by the time they reach cataract age, so they might as well wait.”
For patients who experience residual refractive error, the surgeon's challenge becomes finding a way to correct it that works both economically and surgically for patient and surgeon alike.
What you don't want to do is lose contact with the patient when the surgical result has been less than ideal. “What I like to do is spend some really good time with the patient and the family if at all possible, and say, ‘OK, let's put this in perspective,’ says Dr. Durrie. ‘This is something we're probably going to be able to fix. We're probably going to be able to control it and get your vision reasonably good, but it may take some time, extra surgery and office visits, and you may be on medications for an extended time — but we can improve your vision.” Patients who know what to expect are willing to go along with the enhancement method.
Along the lines of patient counseling, Dr. Stonecipher thinks that there may be one more significant refractive surgery challenge. “The biggest refractive surgery challenge is knowing when to say ‘no’ to a patient.”
Dr. Boxer Wachler concurs. “I think also it's always prudent to be conservative as well,” he says. “Don't be afraid to tell patients if they're not suitable candidates.” OM
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