The Best Refractive Surgery AAO 2008
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The Best Refractive Surgery AAO 2008 The Best Refractive Surgery AAO 2008 Document Transcript

  • EyeNet of REFRACTIVE S The Best SELECTIONS A SUPPLEMENT TO EYENET MAGAZINE The Best of CATARACT & REFRACTIVE SURGERY The Best of RETINA
  • EyeNet SELECTIONS S U B S P E C I A LT Y D AY AT L A N TA 2 0 0 8 clinical update 5 New Pupil Expansion Ring for Floppy Iris A new expansion ring could help surgeons facing a tamsulosin- affected iris. 7 Capsular Tension Rings: Innovation and Debate Surgeons discuss new approaches to zonular weakness, but differ on the criteria for using a tension ring. 9 The Value and Vagaries of Sterile Technique What is the standard for infection control? Surprisingly, refrac- tive surgeons often have very different ideas on what is warranted. 11 The Origins and Treatment of Childhood Cataract Treatment timing and an understanding of the genetic under- pinnings are improving the outlook for congenital cataract. 13 IOL Calculations: When Millimeters Counts How to improve the precision of your IOL calculations. feature Ectasia After LASIK 17 Ectasia induced by refractive surgery can be puzzling. A grow- ing consensus on safeguards and a new registry to track its incidence may solve that. Letter From the Editor Dear Subspecialty Day Attendee, tive medicine? Start by reviewing what Cataract and refractive surgeons find some of the top experts in your field had themselves at a crossroads at this year’s to say in the stories compiled for you Joint Meeting. The technologies available here in EyeNet Selections. Then enjoy for improving refraction on both corneal your Atlanta Meeting to the fullest. and lenticular planes are the best we’ve ever had, and yet the small fraction of patients dissatisfied with the results of their ablation or lens implant has gar- nered much public attention. Richard P. Mills, MD, MPH How can you avoid the pitfalls and Chief Medical Editor gather the pearls of cataract and refrac- EyeNet Magazine/EyeNet Selections ON THE COVER: Injection of a CTR through a microincision controlled by a Lester hook. I. Howard Fine, MD e y e n e t s e l e c t i o n s 3
  • Clinical Update tools and techniques CATARACT New Pupil Expansion Ring for Floppy Iris by barbara boughton, contributing writer A s the population ages, an increasing number of oph- Malyugin Ring Goes to Work thalmology patients are like- 1 2 3 ly to present with the condi- tion known as intraoperative floppy iris syndrome (IFIS). Resulting from treatment with tamsulosin (Flo- max) as well as other systemic alpha antagonists prescribed for benign pro- static hyperplasia, IFIS can result in poor pupil dilation, iris billowing and floppiness, iris prolapse to the incisions and progressive miosis. There are a number of techniques (1) After insertion into the anterior chamber with a disposable injector, the lead that the cataract surgeon can use to and lateral scrolls of the Malyugin ring engage the iris margin. (2) A Lester deal with IFIS, including preoperative hook is used to position final scroll. (3) The ring creates 6-mm diameter pupil. atropine drops, intracameral injection of alpha agonists, the use of Healon 5 Malyugin ring has the thin profile of an to both insert and remove the ring from with low aspiration flow and vacuum, IOL haptic, and so it doesn’t get in the the anterior chamber,” Dr. Chang noted. and, finally, mechanical devices that way of our instruments during surgery. “The learning curve is very fast, and it expand and maintain the pupil diame- It’s easy to avoid corneal contact during can be inserted more quickly than iris ter during surgery. Such devices include insertion,” said Dr. Chang, who is clini- retractors, making this an ideal tech- iris retractors and a variety of different cal professor of ophthalmology at the nique for resident cases,” he added. pupil expansion rings. University of California, San Francisco. Dr. Chang noted that he has done The loading and injection system, in 30 IFIS and small-pupil cases with the New Ring on the Block contrast to those for other pupil expan- Malyugin ring, and the outcomes have The newest of the expansion rings is sion rings, is also disposable. The flexi- been excellent. As with other devices the Malyugin ring (MicroSurgical ble device is injected into the anterior that mechanically expand the pupil, the Technology, or MST). Developed by chamber, where its four circular coils Malyugin ring is particularly useful for Boris Malyugin of Russia, the foldable engage the pupil edge to expand it, severe IFIS. “Because the ring is so thin square device is made of polypropylene according to Dr. Chang. and light, it is still mobile enough to and is much thinner than other rings, Go easy on the iris. Because of how allow the iris to occasionally prolapse to making it easier and safer to manipu- the iris drapes over it, the Malyugin ring, the side port incision,” Dr. Chang added. late inside the eye, according to David in contrast to iris retractors, creates a “However, the pupil obviously cannot D A V I D F. C H A N G , M D F. Chang, MD, who, along with John rounded rather than a square pupillary constrict,” he said. “If the ring seems to R. Campbell, MD, first reported IFIS opening. It expands the pupil without de-center to one side, one lateral scroll syndrome in cataract patients.1 “The overly stretching or traumatizing it, has probably hooked the edge of the and is therefore very gentle on the iris, capsulorhexis, and can simply be disen- This article originally appeared in the January according to Dr. Chang. “The clever gaged with a Lester hook.” 2008 issue of EyeNet Magazine. injector system devised by MST is used I. Howard Fine, MD, has also used e y e n e t s e l e c t i o n s 5
  • Cataract the Malyugin ring and calls it “very and removal after surgery. It is inserted manufacturer of Flomax now includes atraumatic. It goes in quite easily, and through an unenlarged clear corneal a warning in its direct-to-consumer holds the pupil in an expanded way incision, according to Dr. Kershner, who advertisements. with a nice 6-mm pupillary opening. is clinical professor of ophthalmology When using iris retractors, Dr. Chang It’s very easy to work with; rather than at the University of Utah in Salt Lake recommends placing them in a diamond being a full 1 mm, it’s like a thin paper City. Capsulorhexis, hydrodissection, configuration.3 The subincisional hook clip,” said Dr. Fine, clinical professor of phacoemulsification and IOL insertion retracts the iris downward and out of ophthalmology at Oregon Health & can all be safely carried out with the the path of the phaco tip—in contrast to Science University in Portland. Perfect Pupil expansion ring in place. a square iris hook configuration, which “It’s easy to get in and out, and it can tents the iris up into the path. Older Rings expand the pupil to 7 to 8 mm,” said Dr. In an audience poll on complicated Pupil expansion rings that have been in Kershner. It also covers the pupillary cases at the 2007 Annual Meeting in use for a while now include the Morcher sphincter on both sides. “This provides New Orleans, iris retractors were the 5S Pupil Ring and the Milvella Perfect added protection because it’s possible most popular method for dealing with Pupil—both of which are threaded along during surgery to hit the pupil with IFIS during cataract surgery. the pupillary margin using a metal the phaco tip.” Dr. Kershner has used it Plan ahead. When the surgeon knows injector. The Eagle Vision Graether ring with a variety of IFIS cases. “Often the the patient is taking tamsulosin, avail- is a disposable silicone pupil expansion choice a surgeon will make in IFIS cases able strategies can provide positive ring that uses a plastic injector. How- depends on their experience as well as outcomes. In a prospective multicenter ever, all of these rings are difficult to their comfort level with different study published in Ophthalmology, Dr. position if the anterior chamber is shal- devices,” he said. Chang and fellow researchers studied low or the pupil is less than 4 mm wide. Morcher. Dr. Fine has used the 167 consecutive eyes in 135 patients Graether. The Graether is a soft sili- Morcher pupil expansion ring as well taking tamsulosin. Phacoemulsification cone ring grooved to engage the iris as the Malyugin ring and notes that was performed with at least one of four sphincter and maintain pupil dilation. removal technique is important with different IFIS strategies, including The pupil expander is preloaded onto a the Morcher ring. When removing the topical atropine, iris retractors, pupil disposable insertion tool that allows the Morcher, he noted, the leading edge of expansion rings or Healon 5 with ring to be inserted through the primary the ring should be perpendicular to the reduced fluidic parameters.4 surgical incision. An iris-glide retractor incision, and the ring can then be caught The results showed that although fixates the iris sphincter at the incision with the hook of the injection system. 73 percent of patients had moderate or prior to insertion, according to John M. “If you use this technique, the ring can severe IFIS, the rate of posterior capsu- Graether, MD, who developed the ring be removed comfortably and safely.” lar rupture and vitreous loss was only and is in private practice in Marshall- 0.6 percent. The study revealed that 95 town, Iowa. IFIS Update percent of the eyes also achieved a best- Dr. Graether estimates that in his IFIS was first described in 2005 by Drs. corrected visual acuity of at least 20/40. practice, he sees IFIS in 3 to 4 percent Chang and Campbell in a retrospective/ “When experienced surgeons could of his patients, and he uses the Graether prospective study of 1,600 patients. Dr. anticipate IFIS and employ compen- ring on up to 10 to 15 percent of his Chang agreed that while IFIS was first satory surgical techniques, the compli- patients because they may have either reported with the use of tamsulosin, it cation rate from cataract surgery was IFIS or another condition in which the is also seen with other alpha1 blockers low and the visual outcomes were excel- pupil does not dilate well. In contrast, such as doxazosin (Cardura), terazosin lent in eyes of patients with a history of he finds iris retractors problematic. (Hytrin) and alfuzosin (Uroxatral), a tamsulosin use,” Dr. Chang and fellow “They put pressure and indentations on possibility that had been suggested early authors concluded. the iris,” he said. Dr. Graether estimates on by Dr. Kershner.2 However, the fre- that his ring can be inserted in about 30 quency and severity of IFIS is apparent- Drs. Chang, Fine and Kershner report no seconds. ly more severe with Flomax, perhaps related financial interests. Dr. Graether has Milvella. Strategies for dealing with because of its greater affinity for the a patent interest in the Eagle Vision ring. IFIS often depend on the preference of alpha1a receptor subtype, which is pres- the surgeon, according to Robert M. ent in both the prostate and the iris 1 Chang D. F. and J. R. Campbell. J Cataract Kershner, MD. He prefers using the dilator muscle, according to Dr. Chang. Refract Surg 2005;31:664–673. Perfect Pupil expansion ring for severe Following the 2005 report by Drs. 2 Kershner, R. M. J Cataract Refract Surg cases of IFIS. It was developed in the Chang and Campbell, the FDA approved 2005;31:2239–2240. 1990s by John E. Milverton, MD, of a labeling change for Flomax, noting 3 Oetting, T. A. and L. C. Omphroy. J Australia, and is a sterile, disposable, that “the patient’s ophthalmologist Cataract Refract Surg 2002;28:596–598. polyurethane ring with an integrated should be prepared for possible modifi- 4 Chang, D. F. et al. Ophthalmology 2007; arm that allows for insertion into the eye cations to their surgical technique.” The 114(5):957–964. 6 s u p p l e m e n t
  • Clinical Update tools and techniques CATARACT Capsular Tension Rings: Innovation and Debate by lori baker schena, contributing writer I t is difficult to believe that a tiny, round device no thicker than 0.22 Te n s i o n t o t h e R e s c u e mm could cause lively discussion and dissension among cataract surgeons. But recent innovations to the capsular tension ring (CTR)— and the fact that the government refuses to reimburse its use—make for a charged topic. The basics of CTRs are straightfor- ward enough, said Samuel Masket, MD, clinical professor of ophthalmology at the University of California, Los Angeles. Capsular tension rings are designed to stabilize the capsular bag in cases of zonular dehiscence, he said, allowing an IOL to be implanted in the bag when it might otherwise have had to be posi- tioned elsewhere. The open-ended ring has a flexible horseshoe shape and is made of PMMA filament, with eyelets Injection of a CTR through a microincision controlled by a Lester hook. at either end. The ring works by supporting areas in 2003, and Ophtec received approval ● Bonnie A. Henderson, MD, assistant of zonular weakness and allow redistri- for its Oculaid and Stableyes in 2004. clinical professor of ophthalmology at bution of the existing zonules. Dr. Mas- There also have been some modifica- Harvard University, modified the origi- ket noted that a standard tension ring is tions since then: nal 14C Morcher CTR. The new ring, used in patients with less than 4 clock ● Robert J. Cionni, MD, medical direc- aptly named the Henderson Capsule hours of zonule loss and both finite tor at the Cincinnati Eye Institute, intro- Tension Ring, is an open C-shaped loop zonule loss and diffuse zonular weak- duced the modified Morcher ring, which made of PMMA. Its uniqueness comes ness. “In some patients, CTRs can be has a fixation hook that can be sutured from eight equally spaced indentations used in anticipation of later problems,” to the scleral wall without piercing the of 0.15 mm, which are intended to he said. capsular bag. improve the surgeon’s ability to remove ● Ike K. Ahmed, MD, assistant profes- nuclear and cortical material while Originals Followed by Innovations sor of ophthalmology at the University maintaining equal expansion of the I. HOWARD FINE, MD Two manufacturers originally introduced of Toronto, developed the Ahmed Cap- capsular bag. rings to the market. Morcher received sular Tension Segment, a partial ring ● Ehud I. Assia, MD, and colleagues approval for its models 14, 14A and 14C with a fixation hook that can be placed introduced the Capsular Anchor (Hani- following anterior capsulotomy and fix- ta Lenses) at the Academy’s 2007 Annu- This article originally appeared in the March ated using an iris retractor. It can also al Meeting in New Orleans. Dr. Assia is 2008 issue of EyeNet Magazine. be permanently fixated with a suture. chairman of ophthalmology at Meir e y e n e t s e l e c t i o n s 7
  • Cataract Medical Center in Kfar-Saba, Israel, as many of those eyes. So we use CTRs in piece or bimanual irrigation/aspiration. well as associate professor at Tel-Aviv all cases just to be sure. We also use A retentive viscoelastic is then placed University. This device for securing the CTRs in all eyes longer than 27 mm, within the capsular bag, which displaces capsular bag to the scleral wall is a one- where there is a tendency to weaken the nucleus and any leftover cortical plane intraocular implant made of the zonules with cataract surgery.” fibers posteriorly. “You next slip the PMMA. Robert H. Osher, MD, profes- In contrast, Dr. Osher said, “I do not capsular tension ring just under the rim sor of ophthalmology at the University agree that surgeons should implant a of the anterior capsule,” he added. “The of Cincinnati, explained that the Cap- ring in every possible case of suspected cortex will not be trapped because the sular Anchor works like a paper clip, zonular weakness, or make a blanket ring is placed anterior and the remain- with a central rod that is placed in front statement that all patients with pseudo- ing lens material is posterior.” of the capsule, and two lateral arms exfoliation should have a ring. Other- Dr. Fine maintains that a ring inserted through the capsulorhexis and wise we would have implanted thousands should be placed right away, before placed behind the capsule. A suture can of rings for naught. You shouldn’t have doing phacoemulsification and as soon then be looped through the “paper clip” to be more aggressive than you need to as hydrodissection is completed. “In and anchored to the eye. be.” He added that while the CTR is my experience, the ring stabilizes the “I must say that at the Academy very safe, there have been reports of cataract and makes the surgery safer,” meeting, Bonnie and Ehud’s modifica- problems. He recalled cases where a he said. “We sever the cortical connec- tions were among the most interesting ring was accidentally placed into the tions before inserting the ring, which devices presented at the lectures,” Dr. anterior chamber, another ring frac- we do with an injector through a 1-mm Osher said. Drs. Osher and Cionni were tured, and another went through the sideport incision. We use a Lester hook the first surgeons to use CTRs in the capsular bag. “The ring may also cause and a second hook 90 degrees away, United States, in 1993. Differences of damage to the zonules if the bag is which allows us to neutralize the forces opinion about the optimal use of CTRs, dragged during the insertion, which on the capsule during implantation of however, were not ironed out at the is why we fully inflate the bag with the ring. We can then inject the ring meeting. Healon 5,” Dr. Osher said. “Our experi- toward the zonular weakness.” ence indicates that you should only put Controversy #1: Who Needs a CTR? in a ring when you need it.” Controversy #3: Perhaps no one demonstrates more Dr. Osher did stress that while not Who Will Pay for These? enthusiasm for the CTR than Howard every case of weak zonules requires a While contention swirls around CTRs, Fine, MD, clinical professor ophthal- CTR, having the CTR available is imper- all of these surgeons stressed the value mology at the Oregon Health & Science ative when performing any phaco pro- of having this device available in their University in Portland. He has been using cedure because one never knows when practice. Said Dr. Fine, “We just think them for more than a decade, serving as a zonular problem will be encountered. CTRs provide a great advantage, and we a medical monitor in the device’s initial use them every time there is a question studies. “Capsular tension rings stabi- Controversy #2: of zonular weakness.” A major hurdle, lize the cataract and make the surgery When Should Rings Be Placed? however, is that the device is not reim- safer,” noted Dr. Fine, who inserted 450 Dr. Osher recommends that a ring be bursed by the government. CTRs during the early clinical studies used “when you need it and not before “Medicare has decided not to reim- alone. “They convert most cases of you have to. Surgeons should always burse physicians for using CTRs, calling compromised zonular integrity from hold off until you have to put it in.” them an instrument rather than an complex to routine, and give a level of Kenneth J. Rosenthal, MD, in private implant,” noted Dr. Fine, who cited sta- protection from decentration.” practice in Manhattan and Great Neck, tistics in which 17 percent of patients Dr. Fine has a long list of indications N.Y., is also an advocate of “trying to with compromised zonular integrity for CTRs: all cases of trauma, any meta- place the ring as late as you can and as who underwent surgery without a ring bolic or endocrine disease, all cataract early as you need to, preferably after required reintervention. “The govern- patients with previous glaucoma filter- cortical cleanup.” He explained that ment is being penny-wise and pound- ing surgery, all cases of radial keratotomy placing it early is more challenging, with foolish,” Dr. Fine said. “As a result, there (RK) where there are more than eight a higher likelihood of entrapment of is a reluctance among surgeons to use incisions, and progressive zonular dis- the cortex between the ring and the bag. them because of the cost. Yet they are a ease. “There may be weakened zonules However, Dr. Rosenthal has devel- very valuable tool.” even when they look intact,” Dr. Fine oped a technique that obviates the risk said. “RK is a good example of how we of cortex entrapment. He explained that Dr. Masket reports no related financial use CTR in a preventive capacity. When after capsulorhexis, but before nuclear interests. Dr. Fine is a medical monitor for there are more than eight incisions, the disassembly, the surgeon removes as Morcher. Dr. Osher is a consultant with surgeon was trying to achieve maximal much anterior and equatorial cortex Alcon and AMO. Dr. Rosenthal has received effect, and the zonules are now weak in as possible with either the phaco hand travel assistance from Ophtec and AMO. 8 s u p p l e m e n t
  • Clinical Update tools and techniques REFRACTIVE The Value and Vagaries of Sterile Technique by leslie burling-phillips, contributing writer M ost surgeons agree that some level of infection Precautions: Universal control should be achieved in refractive procedures, but there is little agree- ment about what level that should be. It is an issue unique to refractive surgery. “No authoritative institution has estab- lished any parameters. We have all adapted to what is reasonable under the circumstances by taking bits and pieces of knowledge and putting them together in a way that makes sense for this procedure,” said Mark F. Ozog, MD, in private practice in Great Falls, Mont. Dr. O’Day’s practice employs consistent infection controls during refractive Gloves or No Gloves? surgery: gloves, sterile instruments and protected surgical field on every patient. As a result of this ambiguity, the selec- tion of protective wear worn by surgeons my hands to come into contact with Woodhams, MD, an ophthalmologist and their staff members falls along a anything in the surgical field,” said Dr. in private practice in Atlanta, began his continuum that ranges from full garb— Ozog. “However, the entire surgical career in the traditional fashion but gown, hat, goggles, booties and gloves team wears scrubs, hats and shoes that subsequently started wearing gloves. —to almost none at all. The choice to are worn only in the LASIK suite.” “In the early days of anterior lamellar wear or not to wear sterile gloves during Stuart A. Terry, MD, a private practi- keratoplasty and LASIK, I did not wear refractive procedures inspires an espe- tioner in San Antonio, observes a com- gloves because I wanted to reproduce cially contentious debate among refrac- parable protocol: “I do not wear goggles the surgery as I saw it performed by the tive surgeons. or gloves,” said Dr. Terry, who referred South American doctors who originated Did your teacher wear gloves? Dif- to a survey by the American Society of it. However, I later switched to gloves. ferences in medical training can influ- Cataract and Refractive Surgery, which Once learned, gloved surgery did not ence this choice. Some surgeons were indicates that approximately 50 percent offer any significant compromises in taught the “no-glove” technique, the of refractive surgeons wear gloves.1 touch or feel so I have never had an traditional method of performing the To protect the surgical field, Dr. Terry occasion to operate gloveless again.” procedure. “I trained at a time when said he “avoids touching any part of an Daniel J. Ritacca, MD, in private gloves were not used with a keratome, instrument that will come into contact practice in Vernon Hills, Ill., has always D A V I D G . O ’ D A Y, M D and I do not wear gloves unless I have with the eye or lids.” In more than worn gloves, even when he performed an open wound, hangnail or other con- 12,000 procedures, only two of Dr. radial keratotomies. “I was trained at dition where I should not be allowing Terry’s patients have acquired eye infec- the University of Illinois in a large hos- tions, and, he said, “Both healed to 20/20 pital. We did a lot of intensive surgery, This article originally appeared in the April vision with the appropriate treatment.” and, as a result, I have always been con- 2008 issue of EyeNet Magazine. Erring on the side of gloves. J. Trevor cerned about keeping a procedure as e y e n e t s e l e c t i o n s 9
  • Refractive have been recorded in the United States, 1 2 Ti p s o n I n f e c t i o n C o n t r o l for example, and none were in conjunc- tion with an ophthalmic procedure. ● Observe universal precautions: Assume that blood and body fluids—of both Low risk is not no risk. “The chal- patient and provider—could be infectious. lenge becomes determining that there ● Adhere to hand hygiene without exception. This is the best defense against is no chance of exposure. This is an transmitting pathogens and should be observed by staff before and after every important issue when you are talking patient encounter. about any type of invasive procedure, ● Use HVAC filters to thoroughly filter all air that enters the surgical environment. even if the procedure is generally bloodless and minimally invasive,” said ● Do not wear jewelry in surgery; jewelry can harbor microbes. Arjun Srinivasan, MD, who is head of ● Sterilize equipment meticulously and conduct microscopic inspections to ensure the response team in the Division of there are no remaining particles. Healthcare Quality Promotion at the ● Keep nonsterile items out of a sterile field. CDC. “We encourage those who are ● Do not rely on alcohol to sterilize equipment; it is not an approved sterilizing performing invasive procedures, even method and could compromise a sterile field. when there is a perception that the risk ● Use a no-touch technique so that nothing nonsterile touches the eye. is very, very low, to practice standard ● Never touch the working end of a surgical instrument. precautions because it is the prudent thing to do. And these recommendations ● Use sterilized covers on laser joystick knobs and change them between patients. are not solely directed at pathogens like ● Change the speculum when operating on both eyes of a patient; the chances of HIV and hepatitis. They are also directed bacterial contamination increase when an instrument is transferred from one eye at bacterial infections such as methi- to the other. cillin-resistant Staphylococcus aureus ● Do not reuse any instruments without sterilizing them first. [MRSA] or adenovirus.” Protect both patient and provider. clean as possible. Someone on the sur- gies to adjust microscope oculars. “It is a two-way street,” said Adelisa gical staff may touch the instrument Dr. O’Day uses sterile powderless Panlilio, MD, MPH, a medical epidemi- that you were previously using in the gloves in his LASIK suite, and has not ologist who also works in the Division same place where you were touching it. encountered any problem with flap of Healthcare Quality Promotion at the If you don’t wear gloves, bacteria can interface debris from glove use. CDC. “The personal protective equip- spread everywhere.” ment that a surgeon wears when he or David G. O’Day, MD, agreed. “I’m a Occupational Safety she performs a surgical procedure is also glove wearer; I always have been,” Dr. Protection for the patient’s sake is only to protect the patient and prevent prob- O’Day is in private practice in Charle- one side of the equation for infection lems with surgical site infections. We ston, S.C. “However, LASIK and the control. The physicians and ancillary have microorganisms living on our skin corneal refractive procedures that we staff should also be protected from and hair and do not want to transmit perform are not conducted as ‘true’ blood-borne infections that might be those to the patient.” sterile procedures. I treat them as asep- acquired from the patient, such as bac- tically as I can. Even in the operating terial infections, hepatitis B and C, or A New World of Bad Bugs room with sterile gloves on, there is a the human immunodeficiency virus. “Infection scares everyone, especially possibility of contamination, so gloves The sterile gold standard. Universal when we continue to identify bacteria are just the extra safety margin that we precautions delineate a set of measures that do not respond to antibiotics. And employ.” designed to prevent the transmission of that list continues to expand,” warned Simply wearing gloves does not all blood-borne pathogens to health care Dr. Ritacca. “It is not just MRSA any ensure that a surgeon’s hands will workers. Under these parameters, blood more. And it is not just in the hospitals remain sterile. Once an object outside and some body fluids of all patients, anymore. These problems are migrating of the sterile field is handled, such as a regardless of their history, are consid- into surgery centers. We used to be safe, patient’s chart or the microscope ocu- ered potentially infectious. These pre- but things are changing; caution is lars, the gloves are no longer sterile. “In cautions do not apply to tears unless essential. If you get a staph infection these cases, the sterile gloves are not they contain visible traces of blood. in a cornea, it could be a disaster.” doing any good. But it is easy enough That relative risk of infection, in fact, to cover the working surfaces that you often factors into a surgeon’s decision 1 Helga P., et al. J Cataract Refract Surg 2005; need to touch so that you do not have to to wear or not wear protective barriers. 31(1):221–233. contaminate the gloves while you are Ophthalmologists have a very low risk performing surgery,” said Dr. O’Day. of becoming infected by patients. More The physicians interviewed report no relat- Some surgeons use sterile plastic bag- than a million cases of HIV infection ed financial interests. 10 s u p p l e m e n t
  • Clinical Update tools and techniques PEDIATRICS The Origins and Treatment of Childhood Cataract by barbara boughton, contributing writer A lthough cataract surgery for a cohort of Chilean families that mani- adults is a routine procedure fests pediatric cataracts inherited in an Clouded Childhood around the world, the same autosomal dominant pattern. cannot be said for pediatric Same mutation, various presenta- cataract. Surgery in children tions. In a paper soon to be published can be complex and challenging, not in the American Journal of Medical simply, of course, because cataracts Genetics, Dr. Bateman and her col- obscure the image received by the retina leagues studied 28 individuals from four but because the retinal deprivation generations of a Chilean family with a retards the development of the visual high incidence of congenital cataracts. pathway, possibly leading to an intrac- Thirteen of the family members had table form of amblyopia. cataracts caused by mutations in the Worldwide, cataracts are one of the CRYAA crystalline lens gene, but clini- most important causes of blindness in cally the cataracts varied widely and Dense nuclear cataract in a 5-week- children and one of the most preventable exhibited some novel features. “What we old infant at the time of surgery. An causes of lifelong visual impairment. were seeing was enormous variability identical cataract was removed from Visual loss from untreated cataract is in the clinical features of the cataracts, the other eye one week later. uncommon in Western countries but is including the age at diagnosis, the nat- still problematic in some developing ural history of the cataract and how it Concepción Guillermo Grant Benavente. nations. affected the development of vision,” Dr. “But often, when the family members Bateman said. “When you have a large see the results of these surgeries, those A Chilean Cohor t family with hereditary cataracts, such as who had been unwilling before decide One ophthalmologist on the front lines those we worked with in Chile, you can to have the surgery,” he said. of research into the cause of congenital trace the polymorphic DNA markers When to wait, when to act. Dr. Bate- cataracts is J. Bronwyn Bateman, MD, through the family and see which mark- man noted that resolution of infantile a geneticist and professor of ophthal- ers are inherited with the cataract.” cataracts often depends on individual mology at the University of Colorado characteristics of the patient. “If the in Denver. Over the past 15 years, Dr. Tr eatment Timing cataract is particularly dense and Bateman has studied more than 50 large, Some of the Chilean patients have not obstructs vision, then you want to sur- multigenerational families in Latin had their cataracts removed, although gically remove it early in life,” she said. America to isolate the genetic causes of the surgery is provided free of charge However, she said that some people cataracts and to catalog their character- in Chile. “Many of the families are very with hereditary cataracts can do quite M. EDWARD WILSON JR., MD istics. Through this work she identified poor. Although some are treated with well without surgery. Some patients she a new locus for autosomal dominant cataract extraction, a lot of them are met in Chile did not have their cataracts cataract on chromosome 19. Most afraid of the surgery and don’t want to removed until the age of 30. recently, she has been interested in the undergo it,” said Fernando Barria, MD. Underlying systemic disease? Con- clinical variability of cataracts among Dr. Barria is an assistant professor of genital cataracts can be unilateral or ophthalmology at the Universidad de bilateral. “When bilateral, an examina- This article originally appeared in the May Concepción and is on the ophthalmology tion of the parents may help determine 2008 issue of EyeNet Magazine. staff at the Hospital Clinico Regional de if the cataracts are genetic,” said M. e y e n e t s e l e c t i o n s 11
  • Pediatrics you delay longer there may be more Grateful Patients and Patient Chickens amblyopia, which will become more and more difficult to reverse over time,” A lthough many had limited eco- he said. However, lamellar cortical nomic resources, Dr. Bateman’s cataracts, which are also often genetic, patients in Chile were often will- tend to appear after birth and progress ing to travel for several hours to meet more slowly, he said. with her. “The patients I’ve worked with How to manage the surgery. The in Chile are very concerned about the treatment of cataracts in children is reasons why people have this disease. more serious than in adults because As well as wanting to help their family children have to be put under general members, they want to help society by anesthesia for cataract surgery. So the participating in this research project.” timing for cataract removal in a child is Dr. Bateman examines a young Chilean boy. Dr. Bateman, who speaks Spanish, often an issue that needs to be analyzed got to know some of the Chilean families quite well through her work. “Often they and discussed with the parents. would have a family reunion while they met with us.” Dr. Wilson said that while adult On one recent trip involving the families’ blood samples, she tangled with the cataracts are usually hard and brittle, Chilean police. Dr. Bateman had arrived at the local airport in Concepción, where those in children are often soft and she was doing her research, to take a flight to Santiago to meet with ophthalmolo- gummy. “So they can be removed with gists there. In her carry-on bag she had the blood specimens of the families she aspiration alone,” he said. “Another had been working with in Concepción. When the airport officials heard of blood in major difference in children is the way her luggage, they told her the specimens would need to travel in the luggage com- we handle the posterior capsule. In chil- partment rather than under her seat. Concerned that the tubes might rupture, Dr. dren from birth to about 6 years of age, Bateman instead decided to take the local bus to Santiago—a five-hour trip. As she I perform a primary posterior capsulec- sat holding the blood samples, the man sitting next to her held a chicken. “He was tomy and anterior vitrectomy. My pre- very nice,” Dr. Bateman said. “He helped me with my Spanish verb conjugations!” ferred method is to first place the IOL in the capsular bag with the posterior Edward Wilson Jr., MD, professor and corrected later with lenses,” he said. Put capsule intact. I then remove the vis- chairman of ophthalmology at the Med- another way, removing the lens will leave coelastic from the eye. With the irriga- ical University of South Carolina in a refractive error and surgically induced tion cannula remaining in the anterior Charleston. “It’s important to look for a presbyopia.“So we want to think carefully chamber, I make a single microvitreo- cause if the cataracts are bilateral because before we create premature presbyopia. retinal stab incision through the pars if the cause is metabolic, then other spe- Often whether we do cataract surgery plana and place the vitrectomy hand cialists may need to be called in to treat will depend on the amount of visual piece through the incision. I remove the the underlying disease,” he said. trouble the child is having with the central 4.5 mm of posterior capsule with Dr. Bateman explained that cataract cataract. A mild cataract may not be the vitrector and then perform enough surgery for children is quite different worth sacrificing accommodation.” of a vitrectomy so that cells that grow from that for adults. Although cataract How to avoid amblyopia. If the out from the equator of the remaining extraction can be done when a child is patient has a cataract in only one eye lens capsule cannot use the childhood several weeks old, she said, “You have to and already has severe amblyopia, the vitreous face as a scaffolding. This take into account how the eye and the most pressing need might be to rehabil- approach is needed, at times, even in vision will develop as the child ages in itate the eye right away. In this case, the older children who have a posterior deciding when to do surgery,” she said. best choice, again, might be a lens with capsular plaque or those who will not Dr. Wilson agreed. In kids, he said, the the proper correction, anticipating near- cooperate for a YAG laser capsulotomy, eye is still growing. As the eye becomes sightedness later on, Dr. Wilson said. or those older children whose YAG cap- longer front to back, the lens changes “However, if the cataract is in both eyes sulotomy closes spontaneously after it its shape to adapt. “However, when we and there’s no amblyopia, we might is successfully opened.” remove the lens, that natural progression decide to have the child be somewhat The cataract of the future. “Under- J . B R O N W Y N B AT E M A N , M D disappears, and we have to decide if we farsighted. It’s all a question of whether standing the genes that cause these will make the eye farsighted, so that as you want to have thicker glasses now to cataracts can help reduce blindness in it grows the child will have as near-to- avoid thicker glasses later,” he said. children,” Dr. Bateman said. “It may normal vision as possible, or instead fix Dr. Wilson noted that some infantile even be helpful, one day, in predicting the eye with the proper lens at a young cataracts worsen over time and some who will get age-related cataracts.” age, and anticipate that the child will don’t. If the cataract is a dense nuclear become nearsighted as he or she gets opacity present at birth, surgery is best None of the physicians interviewed report older—a problem that will need to be done at 4 to 6 weeks of age, he said. “If financial interests related to this story. 12 s u p p l e m e n t
  • Clinical Update tools and techniques REFRACTIVE IOL Calculations: When Millimeters Count by lori baker schena, contributing writer A s cataract and refractive sur- geons undoubtedly know, a Calculation Ease relatively small axial length miscalculation during intraocular lens calculations can result in poor vision—and a very unhappy patient. And in an era when refractive considerations have crept into every aspect of IOL surgery, even 80- year-old cataract patients expect out- standing outcomes, said Parag A. Maj- mudar, MD, associate professor of ophthalmology at Rush University in Chicago and in private practice at Chicago Cornea Consultants. “Meeting these expectations starts with correctly calculating IOL power. Of course, prop- er surgical technique is always crucial, but even in patients who have never had prior ocular surgery, the calculations are a very important part of IOL im- plantation surgery.” Spot-On Biometr y William B. Trattler, MD, in private prac- tice in Miami, said the most important One of several algorithms available on the Web for calculating IOL powers, this step in calculating IOL power is accu- was designed by Drs. Warren Hill, Douglas Koch, Jianzhong Ma and Li Wang. rate biometry. This can prove difficult in the eyes of patients who have under- length has dramatically improved with measurements, producing variable gone prior ocular surgery. And it is a the advent of the IOLMaster (Carl Zeiss results. The newer technology is more challenge that will continue to intensify Meditec), a device that measures the standardized, and more reproducible— with the increasing number of individ- shape and axial length of the eye to help leading to better results.” uals needing cataract surgery who have the surgeon fine-tune the power. Its lat- Assessing corneal shape. While the undergone previous RK, PRK and est version features new axial length ability to accurately measure axial LASIK procedures. algorithms and an advanced keratome- length has improved, measuring Measuring axial length. Dr. Trattler try mode. corneal topography is more complex. noted that technology to measure axial “Only about five years ago, we were Dr. Majmudar explained that ker- using A-scan ultrasound biometry,” Dr. atometers measure the curvature of the This article originally appeared in the June Majmudar noted. “This technology was anterior surface about 3.2 mm from the 2008 issue of EyeNet Magazine. dependent on the person taking the center of the cornea. “In patients who e y e n e t s e l e c t i o n s 13
  • Refractive have not undergone previous surgery, the value at the center of the cornea is Calculate This! roughly the same as the value at 3.2 mil- limeters,” he said. “However, patients D r. Majmudar knows the challenges of accurate IOL calculations, which is who have undergone LASIK or PRK can why he and colleague Dennis H. Goldsberry, MD, who is in private practice have altered corneas, and the value at in Richardson, Texas, created a free, online spreadsheet and calculator. the central cornea, which is the goal of “The advantage of our site is that it is extremely simple to use,” Dr. Majmudar measurement, may be very different said. “There are some sophisticated calculators out there, and ours is modest. We from that at 3.2 millimeters. Conse- just want to make life a little easier for our colleagues, and one advantage of our quently, if you just rely on the topogra- calculator is that specific topography units are not required in order to be able to phy, you may be off, and for every 1 use it.” This Web site can be found at www.ocularmd.com. diopter you are off in measuring the Dr. Rosenfeld also recommended these calculation tools: corneal curvature, a roughly 1 diopter ● Doctor-Hill.com, created by Warren E. Hill, MD, is a Web site for IOL calculations. miscalculation will result for the ● DocHolladay.com, created by Jack T. Holladay, MD, contains the International patient’s refractive outcome.” IOL Registry and information about Dr. Holladay’s IOL Consultant Software. Working with (or without) preop ● Douglas D. Koch, MD, and Warren E. Hill, MD, working with Li Wang, MD, and records. Steven I. Rosenfeld, MD, asso- Jianzhong Ma, MD, developed an IOL calculation tool for patients who have under- ciate clinical professor of ophthalmolo- gone previous RK, myopic LASIK and hyperopic LASIK. It is available at http:// gy at the Bascom Palmer Eye Institute iol.ascrs.org/. and in private practice in Delray Beach, Fla., also pointed to the challenges of inserting a contact lens of known base of these RK cuts, which can permanent- ascertaining accurate corneal topogra- curve and power on the eye in question, ly weaken the cornea,” Dr. Rosenfeld phy. “There are ways to get around these and doing an overrefraction to predict pointed out. “I will be operating on two limitations, and the first one is having the corneal power. It represents an indi- patients within the next month who historical data to help you calculate the rect way to obtain information about presented with this challenge. One is a lens implant power,” Dr. Rosenfeld said. the shape of the cornea, which can then gentleman with a four-cut RK, and he “If you are lucky enough to have the be plugged into an IOL calculation for- now needs cataract surgery, and anoth- patient’s preoperative information mula. “Yet even this approach has its er has a 16-cut RK. Both their vision before they underwent PRK or LASIK, drawbacks because ophthalmologists and corneal curvature fluctuate during and you know their postoperative have varying levels of confidence in mak- the day, and thus it will be virtually results, that can help guide you and give ing these estimations,” he said. “Recent- impossible to achieve a perfect IOL cal- you a more accurate reading. You can ly, several studies have demonstrated culation. Instead, we do the best we can plug that into your formulas.” the value of using the central corneal given these anatomic limitations.” However, obtaining these preopera- measurements from the Humphrey PRK suspects. Dr. Rosenfeld noted tive data may be easier said than done, Atlas corneal topographer, the Orbscan that Baby Boomers seeking cataract especially in places such as Boca Raton, II and the Pentacam, to more accurately surgery who have had LASIK and previ- which attract retirees who may have calculate the correct IOL power.” ous RK are easy to detect on clinical undergone a refractive procedure in one Both Drs. Trattler and Majmudar examination. However, this is not the area of the country and decided to have also noted that the Pentacam can image case with PRK. “If the patient doesn’t cataract surgery in their new retirement the front and rear surfaces of the cornea tell you he or she had previous surgery, city. “Patients rarely carry this informa- in patients who have previously under- the surgeon can easily make a calcula- tion with them,” Dr. Rosenfeld said. gone RK, PRK or LASIK, and it can pro- tion mistake. Obviously, a thorough “And many ophthalmologists purge vide a keratometry value that may be put history is an important component of their old records after seven years. Con- into the IOLMaster. With this equiva- accurate IOL calculations,” he said. sequently, if a patient had LASIK 10 lent K reading, they said, the surgeon Contact corruption. Even patients years ago and now needs cataract sur- may not need previous LASIK records. who have worn contact lenses most of gery, there is a good chance that the their lives, especially the hard, gas per- physician may not even have these rec- Refractive Rogues Galler y meable or extended-wear lenses, may ords. We have experienced many situa- Previous refractive surgery can compli- present challenges. “Contact lenses are tions in which we send a record release cate IOL calculations unexpectedly. not benign,” Dr. Rosenfeld said. “They to an ophthalmologist up north just to RK weaklings. Patients who had RK can cause corneal stress, which can be learn that the records no longer exist.” can experience fluctuations in the shape manifested in many ways. The cornea Corneal measurement: backup tools. of the cornea in the course of a single can become swollen. In addition, con- Dr. Rosenfeld said that without previ- day, let alone week to week, making it tact lenses can change the shape of the ous records, the next alternative is a con- extremely difficult to obtain an accurate endothelial cells and alter the normal tact lens overrefraction. This involves IOL calculation. “Some patients had 16 mosaic pattern, and some individuals 14 s u p p l e m e n t
  • have experienced loss of endothelial cells after decades of use.” Corneal warpage is also a real condition in these patients. Dr. Rosenfeld recommends that these patients stay out of contact lenses for weeks or even months prior to surgery, so that the ophthalmologist can obtain accurate keratometry. This also holds true for patients undergoing refractive surgery, as the cornea needs to resume its natural shape before a proce- dure can be done accurately. “We don’t proceed with refractive surgery until the patient has two visits where the corneal topography is the same,” he said. Accuracy Is Ever ything Dr. Trattler noted that the introduction of and increasing demand for presbyopia correcting IOLs necessitates even more accurate biometry, as these implants need to be right on target. “If you end up a quarter- or a half-diopter off with the ReStor or ReZoom multifocal lens- es, patients will be unhappy,” he said. “This also holds true for the Crystalens accommodative IOL. Presbyopic patients tend to be extremely sensitive to any miscalculation.” He said that in his presbyopic popu- lation, he experiences a 10 percent to 12 percent enhancement rate. “In these patients, it is important that you can offer solutions such as laser vision cor- rection or limbal relaxation surgery,” Dr. Trattler said. “The more accurate you can be with your calculations, the lower the enhancement rate.” Anatomy is money. Dr. Trattler stressed that the “unhappiness factor” associated with miscalculating IOL strength results in added costs for the practice.” He also stressed the impor- tance of informed consent with any cataract or refractive lens exchange patient. “Managing expectations is of vital importance when working with increasingly challenging patient anato- my and lens technology.” Dr. Majmudar reports interests in Alcon, Allergan, AMO and Inspire Pharmaceuti- cals; Dr. Rosenfeld reports interests in Allergan; Dr. Trattler reports interests in Allergan, AMO, Bausch & Lomb, Inspire Pharmaceuticals and Vistakon. e y e n e t s e l e c t i o n s 15
  • “WHEN WE STARTED DOING LASIK, WE DIDN’T really understand that ectasia was a significant issue,” said William B. Trattler, MD. It took awhile, he said, “to better understand who was at risk or to see this was really an issue.” Today, nearly 10 years after the first case was reported, iatrogenic, post-LASIK ectasia is one of the most controversial issues in refractive surgery. The etiology is unknown, and, as Dr. Trattler pointed out,“there are significant differences in opinion” regard- ing the relevance of risk factors. Yet surgeons may avoid this particularly insidious complication of LASIK by heeding the possible risk factors, which include: high myopia, patient age, reduced preoperative corneal thickness, reduced residual stromal bed thickness after laser ablation and asymmetrical corneal steepening (forme fruste keratoconus, keratoconus or pellucid marginal degeneration). Understanding a safe threshold. Still, questions abound. How thick should the cornea be to maintain structural integrity? How deep can the surgeon go? And why do some patients with abnormal topographies not develop ectasia following LASIK, while some patients with normal-looking eyes do? “There’s still an evolution of trying to understand who is an appropriate patient for LASIK and who should not be offered LASIK,” said Dr. Trattler. Until post-LASIK ectasia is better understood, there will be unhappy patients. And there will be doctors who are wary of the medicolegal consequences. BY MIRIAM KARMEL, CONTRIBUTING WRITER This article originally appeared in the January 2008 issue of EyeNet Magazine. e y e n e t s e l e c t i o n s 17
  • Consensus and Consequences “We estimated one in 2,500 cases, with older screening In an attempt to clarify some of the issues surrounding post- technology,” Dr. Randleman said. “I think there’s a good LASIK ectasia, a committee of cornea and refractive surgeons chance that it should be lower. With appropriate screening it assembled by the International Society of Refractive Surgery/ will be one in 5,000 or less.” American Academy of Ophthalmology and the American Society of Cataract and Refractive Surgery issued a consensus Anticipating the Major Risks report in November 2005.1 The group was convened following Poor preoperative screening was the focus of two multimil- a multimillion-dollar legal judgment in favor of a young man lion-dollar ectasia lawsuits that found in favor of the plain- who developed ectasia following LASIK. The consensus group tiffs. In one, a 32-year-old man claimed his surgery in October spelled out the known risk factors for weeding out unsuitable 2000 never should have been performed because of kerato- candidates for LASIK. The group also stated that ectasia is a conus, which he said was present before the surgery or could known risk of laser vision correction. When complications have been anticipated. In 2005, a jury awarded him $7.25 mil- arise, “it does not necessarily mean that the patient was a poor lion, nearly doubling the previous record. candidate for surgery, that the surgery was contraindicated or As the major risk factors for ectasia become clearer, two that there was a violation of the standard of care.” (For an exam- vital considerations can help guide the refractive surgeon ple of such a complication, see “Iatrogenic Ectasia,” next page.) around those factors: The group described a continuum of clinical findings that Topography. “Most people believe the most common risk ranged from the “clearly normal” to the “clearly pathologic” factor is abnormal topography,” said Dr. Rabinowitz. “If you cornea. The difficulty of accurately predicting which patients look at the literature and take out all the other risk factors, in will develop this dreaded complication of LASIK lies in the the vast number of cases there was abnormal topography.” Yet ambiguous middle. clearly, he added, ectasia can occur in the presence of normal So just how common is it? Fortunately, surgically induced topography. ectasia is rare, though the number of cases is not known. “We He added that there are still suspicious topographic pat- don’t know the answer to what percentage of LASIK patients terns that aren’t well understood. “Some are high risk and develops ectasia,” said J. Bradley Randleman, MD, who sus- others not high risk. That still needs to be worked out.” But, pects the number is underreported. “We’ve been pretty good said Dr. Rabinowitz, “knowingly performing LASIK on a at screening out a lot of cases,” said Yaron S. Rabinowitz, MD, patient with keratoconus or pellucid marginal degeneration,” a member of the 2005 consensus committee. “I’m amazed would be a deviation from the standard of care. there aren’t a lot more.” Dr. Randleman, who has developed a risk assessment tool (see “Ectasia Risk Assessment”) for post-LASIK ectasia, agrees. “Abnormal topography stands alone as something ECTASIA REGISTRY that can exclude people,” he said. “There are some firm pat- A registry for reporting cases of ectasia after LASIK had its terns that we know are abnormal,” he said. “If a patient has debut recently. The purpose of the registry “is to identify risk a topographic pattern that indicates keratoconus, pellucid factors that are not currently known and to serve as a basis marginal degeneration or forme fruste keratoconus, then for clinical trials in the future,” said Dr. Stulting, who is they should absolutely be excluded from LASIK, even if the directing the project. remainder of their examination is normal.” There are two Pachymetry. Another important factor is preserving anticipated phases to enough residual stromal bed; the question, though, is how the project. The first much is that? Traditionally the accepted range has been 200 phase will establish to 325 µm, with 250 µm chosen as the arbitrary cutoff. “But a database for sub- for each cornea it’s different. Nobody knows what the magic mission of informa- number is,” said Dr. Rabinowitz. tion on patients who To preserve enough residual stromal bed, Dr. Trattler developed ectasia added, “it’s most important to measure the patient’s flaps at after LASIK. These the time of surgery.” Yet unpublished data from 2005 survey cases will be evaluat- conducted by Magill Research Center at the Medical Univer- ed against a control sity of South Carolina found only 34 percent of U.S. refrac- group of LASIK patients who did not develop ectasia, in an tive surgeons routinely perform intraoperative pachymetry, effort to validate known risk factors and discover new ones. he said. Phase two will include prospective clinical trials of LASIK Dr. Rabinowitz agreed that pachymetry during surgery is in cases involving unproven risk factors. essential because keratomes produce such variation in the Ophthalmologists who care for patients with ectasia are thickness of the flap. “You cut the flap and lift it up, then you encouraged to participate in the online registry by entering measure it,” he said. If the measurement is too low, abort the data on their patients at www.ectasiaregistry.com. procedure, he said. “If you don’t have enough tissue, a few months later you can do PRK.” 18 s u p p l e m e n t
  • IATROGENIC ECTASIA candidate for LASIK. Her case is representative of one that the consensus report said “does not necessarily mean that the A young woman in an ectasia support group shared the history patient was a poor candidate for surgery, that the surgery was of her ectasia, below, with Dr. Trattler, who noted that her contraindicated or that there was a violation of the standard topography initially made her seem like a very appropriate of care.” BEFORE REFRACTIVE SURGERY. 27-year-old patient with preoperative corneal thicknesses of 521µm OD and 524µm OS. The posterior floats are normal, and there is no sign of early keratoconus. TEN MONTHS POSTOP. LASIK ablation depth was 52 µm OD and 62 µm OS, and the refractive correction was –4.75 + 0.25 x 140 = 20/20 OD and –6.25 + 0.75 x 070 = 20/20 OS. A confocal microscope exam determined the corneal flap thicknesses were 120 µm OD and 140 µm OS. But 10 months later, post-LASIK ectasia was diagnosed OU. The map looks like pellucid marginal degeneration. ONGOING THINNING. Topography taken two years later shows progression of ectasia. e y e n e t s e l e c t i o n s 19
  • Other Red Flags dures performed elsewhere. Age. Since 2005, doctors have become increasingly aware of In the meantime, patients who are not good candidates for the role that the patient’s age plays as a predictive factor, said LASIK need not despair. PRK is becoming a more commonly R. Doyle Stulting, MD, PhD, who was a member of the con- accepted alternative, Dr. Rabinowitz said. sensus committee. “Early on we focused on parameters that Dr. Koch agreed. “If there is a good likelihood of leaving we can measure in the clinic, like corneal curvature, corneal too little tissue, avoid LASIK and switch to PRK. In eyes with thickness, residual stromal bed and the degree of myopia. Then questionable topography, consider PRK or no surgery at all.” we began seeing people who did not have any of these predic- tive factors and they still developed ectasia,” Dr. Stulting said. Treating Ectasia “It turned out they’re significantly younger than the ones who Treatments for post-LASIK ectasia are the same as for kerato- have identifiable risk factors. We believe those are people who conus, said Dr. Randleman. Treating with contact lenses is may have developed keratoconus or forme fruste keratoconus most common; penetrating keratoplasty (PK) is the treat- had they not had LASIK.” ment of last resort. Even if an eye warrants PK, the prognosis Douglas D. Koch, MD, agrees. “Be especially wary of ques- is excellent, according to the 2005 consensus group, which tionable topography in young patients who need large correc- reported graft survival rates of 97 percent and 92 percent at tions, as this group has been shown to have a higher incidence five and 10 years, respectively. of ectasia.” But in the vast majority of cases, PK can be avoided. At Asymmetry. Another red flag is asymmetry between the Emory University, where Dr. Randleman has treated some eyes, said Dr. Trattler. He described a patient whose eyes 75 ectasia cases, only about 8 percent have required a corneal appeared normal, but who had astigmatism at 90 degrees in transplant. one eye and at 180 degrees in the other. Asymmetry may be There are surgical alternatives to conventional penetrating a sign that one eye is progressing toward keratoconus or pel- keratoplasty, including anterior lamellar keratoplasty, which lucid marginal degeneration, he said. enables targeted replacement or augmentation of corneal Enhancements. Dr. Trattler also urged caution before pro- stroma, without replacement of endothelium.2 ceeding with LASIK enhancements. Because LASIK patients Additional interventions designed to enhance corneal sta- who present for an enhancement with myopic astigmatism bility include: may potentially have early ectasia, he advised carefully exam- ● Intacs. Intrasomal corneal ring segments can be inserted ining the topography for asymmetry. Also, it is important into the thinned cornea of contact lens–intolerant patients to to confirm that the topography and refraction are relatively serve as a “crutch.” They flatten the central area of the cornea stable, which means obtaining old records for LASIK proce- and correct myopic refractive error. Intacs may halt progres- a low, moderate or high risk for ectasia. ECTASIA RISK ASSESSMENT “Our current paper was written to put some science behind Researchers at Emory University have come up with a risk the anecdotes of what may or may not be risk factors,” said factor stratification scale intended to help prevent ectasia Dr. Randleman, lead author of the study. “We developed the after LASIK. ectasia scale using the literature that was available. Then we After conducting a meta-analysis of published results from followed that up with another study where we validated the 1998 to 2005 related to post-LASIK ectasia, the researchers risk factors.” found that, compared with controls, ectasia cases had abnor- The scoring system, which identified more than 90 percent mal preoperative topographies (35.7 percent vs. 0 percent); of abnormal patients, was replicated using a separate popula- were significantly younger (34.4 years vs. 40); were more tion. Dr. Randleman noted that there have been numerous myopic (–8.53 vs. –5.09 D); had thinner corneas before surgery proposed contraindications to LASIK, including a residual (521.0 vs. 546.5 µm); and had less residual stromal bed stromal bed thickness less than 250 µm, a preoperative thickness (256.3 vs. 317.3µm).1 corneal thickness less than 500 µm, keratometry greater than Point system. After analyzing the data, they assigned numer- 47 D and an Orbscan posterior float value greater than 50 µm. ical scores to the various risk factors, which included topogra- On the other hand, he said that “there were actually very few phy pattern, residual stromal bed thickness, age, preoperative ‘absolute’ cut-off values.” corneal thickness and preoperative spherical equivalent mani- All about thresholds. “However, when there are too many fest refraction. In the topography category, for example, they abnormalities in combination, then the patient should be assigned four points to forme fruste keratoconus; three points excluded from LASIK,” added Dr. Randleman. The scoring to inferior steepening/skewed radial axis; one point to asym- system shows that “you can’t look at things in isolation.” metric bowtie. Zero points were assigned to normal/symmetric bowtie. By adding up the points for all the risk categories, a 1 Randleman, B. J. et al. Ophthalmology 2008;115:37–50. Also surgeon should have a better sense of whether the patient has published online July 12, 2007. 20 s u p p l e m e n t
  • sion, make patients more tolerant to contact lenses and, hopefully, obviate the need for a corneal transplant. ● Collagen cross-linking. This potential treatment, for which clinical trials should soon begin, promotes the integration of the natural anchors within the cornea. Collagen cross-linking inhibits the cornea from bulging out and becoming steep and irregular. This treatment avoids ablation or cutting across the visual axis. Early reports suggest that it may halt the progres- sion of keratoconus and that it also causes keratoconic corneas to assume a more normal shape, with consequent improvements in visual acuity. What’s In Store? Today researchers are looking for the gene or genes responsi- ble for keratoconus, which could lead to the development of blood tests that would enable surgeons to identify patients at risk of ectasia before any clinical signs are evident. Dr. Rabi- nowitz’s group at Cedars-Sinai Medical Center is working on one such molecular genetic test. In the meantime, questions remain. Not known is whether currently identified risk factors are sufficient to allow the pre- diction of ectasia, or whether researchers ought to be looking at other factors, said Dr. Stulting. “We believe that there is an inherent instability in the corneas of people who are going to develop ectasia,” he said, adding, “We may be directly able to measure that instability.” 1 Binder, P. S. et al. J Cataract Refract Surg 2005;31:2035–2038. 2 Curr Opin Ophthalmol 2007;18(4):284–289. MEET THE EXPERTS DOUGLAS D. KOCH, MD Professor of ophthal- mology, Baylor College of Medicine, Houston. Finan- cial disclosure: Consultant with Alcon and AMO. YARON S. RABINOWITZ, MD Director of eye research at Cedars-Sinai Medical Center, Los Angeles, and clinical professor of ophthalmology, University of California, Los Angeles. Financial disclosure: Consultant for Wavelight and Intralase. J. BRADLEY RANDLEMAN, MD Assistant profes- sor of ophthalmology, Emory University. Financial disclosure: None. R. DOYLE STULTING, MD, PHD Professor of ophthalmology, and director of the cornea service, Emory University. Financial disclosure: None. WILLIAM B. TRATTLER, MD In private practice at the Center for Excellence in Eye Care, Miami. Financial disclosure: None. e y e n e t s e l e c t i o n s 21