LaserVision.gr | Prevention and Management of LASIK Complications

There is no doubt that laser in situ keratomileusis (LASIK) has enjoyed enormous popularity and, for the most part, well-deserved success as the procedure of choice among patients and surgeons for the majority of refractive errors. Of the 940,000 laser refractive procedures performed in the United States last year, 846,000 were LASIK; a significant increase from the 360,000 LASIK procedures done in 1998. Optimistic projections for the year 2000 put total laser refractive procedures at 1.65 million, of which 1.485 million are expected to be LASIK. (Source: Spectrum Consulting)

As with any medical procedure, an increase in the number of surgeries is usually accompanied by a concomitant rise in that procedure's complication rate. LASIK is no exception. This roundtable brings together a group of highly experienced refractive surgeons to share their hard-won expertise in helping you lower the LASIK learning curve, avoid mistakes and maximize patient outcomes.
- Leslie B. Sabbagh

MS. SABBAGH: What in the preoperative exam helps you to prevent potential complications?

DR. WILSON: I look for ectatic dystrophies and contact lens warpage on topography. Recently, I have paid much more attention to evidence of dry eye disease because it helps me predict patients at risk for LASIK-induced neurotrophic epitheliopathy (LINE). Although the condition occurs independently of dry eye disease, those with dry eyes have a much greater incidence of LINE. I use nonreserved artificial tears, ointments, and punctal plugs for dry eyes, and treat meibomian gland disease.

DR. DONNENFELD: I screen for corneal ectasia and irregular astigmatism, and perform pachymetry. I pretreat mei- bomianitis with doxycycline, 100 mg b.i.d. for two weeks, hot compresses and good hygiene; and I prescribe non-preserved lubricating drops. If patients have conjunctival staining, then I maximize the ocular surface. Frank corneal staining preoperatively is a strong contraindication not to do surgery. I look at the preoperative topography, refraction and autorefraction. If the axis is off 10 degrees between one of them, I always double-check the refraction to make certain that I have the right prescription.

DR. POP: Patient expectations are key. Some patients have enjoyed 20/15 corrected vision from their teens. Post-LASIK, they may be less than pleased with 20/20 uncorrected. Although I agree that contact lens-intolerant patients can experience difficulty, many of these patients do very well postop. In my hands, often the least happy patients are low myopes who have no preop pathology, yet acquire dry eye syndrome. I believe patients with any amount of asymmetrical astigmatism should not be treated because the potential for keratic disease is much higher.

DR. CARLSON: In my practice, every patient receives a detailed examination to ensure that there are no medical or psychological contraindications to surgery. The ability to achieve outcomes that satisfy patients relates directly to the ability to meet or exceed their expectations.

DR. KANELLOPOULOS: I routinely plug the lower puncta of patients at risk for dry eye disease immediately after the procedure and give viscous, preservative-free tears, such as Celluvisc, for the first day. I co-manage most of my patients, and it's helpful to explain what they will experience in the first month. For example, I discuss postop dryness; a slight hyperopic shift in over-40 patients and the need for transient presbyopic glasses; and the possibility of retreatment, especially in patients over -6 D.

DR. WILSON: Screening for anterior basement membrane dystrophy must be done preoperatively. These patients have a much higher likelihood for epithelial slough during flap creation. The majority do well, but have a more protracted recovery period and a tendency for regression of effect. If these patients are also low myopes, I consider PRK.

DR. CARLSON: Contact lens intolerance should alert the surgeon to the possibility of basement membrane dystrophy or loose epithelium. I'm also wary of patients who are only happy with rigid gas permeable contact lens vision, especially if they have high degrees of regular astigmatism or significant amounts of irregular astigmatism. They may not be satisfied with LASIK. There is obvious concern over creating a free cap in a patient with extremely flat corneas, but I'm also concerned about the quality of vision in a patient who may end up with a final keratometry reading below 35 D. Unusually steep cases, particular- ly hyperopic patients, also require caution. Patients with axial hyperopia occasionally have steep corneas preoperatively, and LASIK may produce an unacceptably steep topography resembling keratoconus.

DR. DONNENFELD: I treat patients with normal or mini- mally compromised visual fields if they are in the care of a good glaucoma specialist. I discontinue all glaucoma medications preop to avoid epithelial toxicity and prescribe an oral medication, such as Neptazine 50 mg b.i.d., to achieve glaucoma control.

DR. POP: Treating patients with another ocular pathology, such as glaucoma, can be difficult from a psychological standpoint. For example, if their glaucoma worsens postop, they may blame LASIK, even though their condition is unrelated to the surgery. If their visual field is com- promised, I don't perform LASIK.

DR. KANELLOPOULOS: The glaucoma patient brings three challenges: potential epithelial toxicity; possible neuronal damage caused by the high vacuum stage of the microkeratome; and the measurement of IOP postoperatively. In a patient with a visual field deficit, I avoid LASIK. The jury is still out on whether an efficient LASIK surgeon causes any neuronal damage by significantly increasing pressure for about 15 seconds, but this needs to be better evaluated.

DR. WILSON: I agree with being very careful about treating glaucoma patients. But whether we damage the nerve fiber layer or the optic nerve itself is controversial. I think that most preliminary reports using nerve fiber layer analyzers are confounded by LASIK-induced corneal changes, which alter the measurements.

DR. DONNENFELD: Glaucoma patients have a 50 percent chance to be steroid-responders; I am much more comfortable raising the IOP for 15 seconds with the microkeratome vacuum than putting a patient on a three- month steroid course due to PRK-induced corneal haze. I perform LASIK routinely on patients with mild glaucoma. Patients with advanced glaucoma should not have refractive procedures.

DR. CARLSON: I share the concern about performing LASIK on patients with advanced or poorly controlled glaucoma. I've operated successfully on several prospective trabeculectomy patients with high degrees of refractive error and astigmatism. LASIK is not an option in eyes that already have a filtering mechanism.

DR. WILSON: I have not yet seen late haze in patients treated for less than -5 D with PRK in about 3,000 PRK procedures. But as patients become progressively more myopic, my concern heightens; my typical PRK patient receives FML q.i.d. for one week - never longer. It may even be possible to stop treatment after the first day, according to John Marshall's study. 1

DR. POP: The new techniques with PRK are much safer and more effective with the second-generation lasers. Using my laser with a slit-scanning system, I see no haze; topical steroids are unnecessary for treatments of-5 D and lower.

DR. CARLSON: I refer any patient with a suspicious peripheral retinal pathology or previous retinal treatment. We have a large retinal service at Duke, and many of my patients have had scleral buckling procedures. I like to have the blessing of the retina subspecialist before performing laser refractive surgery on these patients.

DR. DONNENFELD: A retinal subspecialist should evaluate any patient with obvious preoperative pathology. I get a preop retinal consultation for any patient who has more than -8 D because of the high risk for postop problems. In addition, after their postoperative care is complete, I advise high myopes to have annual dilated exams.

DR. KANELLOPOULOS: In my international practice, I use bioptics, a combination of LASIK and a phakic intraocular lens, on patients who have from 10 D to 25 D of myopia. A microkeratome flap is made, then an Artisan lens is inserted; the patient is refracted six weeks later when the refraction is stable and some of the cylinder induced by intraoperative cautery has resolved. Finally, LASIK is performed for the residual refractive error.

DR. WILSON: I have seen two posterior vitreous detachments very early after LASIK in patients with more than -8 to-10 D.I advise patients that studies have not shown that LASIK is associated with retinal detachment, but I still have some concern.

MS. SABBAGH: What role does topography play?

DR. KANELLOPOULOS: There's general agreement that topography is the essential tool for refractive surgery, with wavefront technology taking on a larger role to further evaluate LASIK patients. For patients who show any sign of asymmetric astigmatism, I obtain an Orbscan image. I'm particularly interested in the posterior corneal curvature of patients with irregular astigmatism.

DR. POP: I use the EyeSys 2000, version 2.1 and the Tomey TMS-I. In cases of astigmatism or corneal surface change, I look for a skewed pattern deviation on the steep meridian. I also regularly use the asphericity index or Q value if asymmetry or astigmatism is seen on topography.

DR. DONNENFELD: We use topography in every patient. Keratectasia must be suspected in cases of pro- gressive myopia following LASIK. Retreatments are con- traindicated in eyes with progressive corneal steepening post-LASIK.

DR. KANELLOPOULOS: Often I see topographic images that consist of two small pictures on one piece of paper. I prefer full-page topography because it reveals a great deal of anterior pathology that is not apparent clinically.

DR. CARLSON: I find it helpful to perform a repeat topography while watching the stability of the corneal mires on the screen. This helps assess the stability of the image between blinking and also whether surface pathology is interfering with the quality of the mires. I use topography with other measurements, including manifest and cycloplegic refractions for overall consistency evaluating both the magnitude and the quality of corneal astigmatism prior to treatment. Topography is extremely helpful in identifying patients with contact lens over-wear or improperly fitting contact lenses. I ask tone soft lens patients to remove their lenses three weeks prior to surgery. I ask RGP patients to stay out of their lenses three to four weeks for every decade of wear. Still, I've had several patients who did not have stable refractions and topographies six months out of Phakic contact lenses.

DR. WILSON: Any of the available corneal topography instruments do a great job imaging the anterior surface topography. I have concerns about the accuracy and reliability of posterior curvature changes measured with the Orbscan. Robert Maloney has made important points about some of these apparent ectasias in patients who had LASIK for 3 or 4 D of myopia being attributable to errors inherent in measurement with that instnunent.2

DR. KANELLOPOULOS: The Orbscan may not be the most accurate instrument in measuring corneal pachymetry, but it leads us in the right direction. Dan Reinstein has done some interesting work with high frequency, digital ultrasound pachymetric mapping of LASIK's effects on the corneal epithelium and stromil.3

DR. CARLSON: Assessing the retinoscopic reflex is very helpful in determining why patients, who may have improved from 20/200 to 20/20 on their first day, still complain about the quality of their vision. You can see edema on retinoscopy that you cannot see by slit lamp examination. Also, this is the most helpful way of assessing the visual significance of striae.

MS. SABBAGH: How important is pupil size and how do you measure it in normal and low light?

DR. CARLSON: Our technicians measure the pupils with a pupil gauge under normal illumination, then under scotopic illumination. The significance of the pupil size increases in patients with high degrees of spherical correction and astigmatism; these patients may also be intolerant of glare or have reduced contrast sensitivity. There's a significant psychological factor: Some patients are more tolerant than others are, and I think that plays a role in their ultimate satisfaction with the outcome.

DR. DONNENFELD: We don't use a pupil-measuring device: I initially evaluate patients in a dark room. The second evaluation of pupil size occurs during the procedure. The non-operative eye is covered and I turn the light down on the operating microscope and look at the operative under the microscope with the reticle, which gives the exact size of the pupil.

We treat patients with larger pupils, significant cylinder and/or high myopia with larger ablation zones. We use the VisX Star II for most procedures, however, for larger pupils we've had great results, with minimal glare, using the Chiron/B&L Technolas laser. We can achieve ablation zones of 14 and 15 mm and optical zones of 7 mm.

DR. POP: We studied glare and halos in 1,300 patients' and discovered only two risk factors for glare: myopia over 5 D, and 6-mm optical zone ablation without a transition zone. In these eyes I suggest using a transition zone 1to 2 mm from the optical zone.

DR. KANELLOPOULOS: I use the Oasis pupillometer routinely. Patients with high astigmatism and myopia and large pupils have more problems with glare and halos when a small zone ablation is used. I think LASIK creates a large amount of aberration in higher myopes.

DR. WILSON: I use the Humphrey 992 topographer with a printout including corneal maps and video keratoscope images on the same page. Pupil size seems more important in high myopia, but even there the correlation isn't always strong.

MS. SABBAGH: How do you prepare the surgical field to avoid intraoperative problems?

DR. CARLSON: I use a Betadine prep and drape the upper and lower lids to isolate the lashes and meibomian glands. I use one drop ofproparacaine on the ocular surface, then use a Merocel sponge soaked with proparacaine in the fomix prior to draping. I have used a locking speculum, but now use a non-locking wire speculum; patients find it more comfortable and we achieve better exposure.

DR. DONNENFELD: Early on, we gave anesthetics up to half-hour before surgery and saw a significant number of epithelial sloughs intraoperatively. We now instill the anesthetic in the operating suite. I generally only drape the upper lids and use a locking lid speculum. Patients who have the most flap complications are usually those in whom you can't get good exposure. We just finished clinical trials on a new microkeratome, Allergan's Amadeus, and were very impressed with the exposure we achieved with the instrument.

DR. WILSON: I instill anesthetic in the first eye when the patient is in the laser room, then I mark both corneas. I don't instill anesthetic in the second eye until the first eye is finished and we're about to prep the second eye. We've done a small study that showed inconsistency between the first and second eyes when both are anesthetized at the same time. Since we stopped instilling anesthetic in both eyes simultaneously, we no longer see that variability.

DR. DONNENFELD: We place Celluvisc, about 30 seconds after the procedure, to apply focal pressure to the cornea, remove striae and protect the epithelium until the anesthetic wears off. Since we've begun using this technique, we've been very pleased with the clarity of the corneas and the lack ofepitheliopathy.

DR. WILSON: An aspirating lid speculum is very helpful in removing any material from the surface of the eye during irrigation, including meibomian gland secretions. Removal of this material helps keep the interface cleaner. DR. POP: My staff and I wear sterile gloves, but I don't drape the patient nor do I scrub the eyelids; in more than 20,000 refractive surgery cases, we've seen no infection. I wipe all the instruments inserted beneath the flap on a wet sponge that also isolates the lashes. I often don't use a speculum for cases with tight lids; instead I find that the Moria LSK ONE microkeratome plate does a good job separating the lids.

During surgery, I use the Chayet sponge to protect the flap. After the cut is made, I fold the flap on itself so that the epithelial surface is exposed rather than the stroma, and the inside of the flap is completely protected from any meibomian gland secretions. Because it is folded like a sandwich, the edge of the flap protects the hinge during ablation. We've seen no difference in the flap postop.

DR. DONNENFELD: If I see significant meibomian gland secretion, I tilt the patient's head to the side and copiously irrigate the cul-de-sac. Trying to irrigate without tilting pools the meibomian gland secretions, but turning the patient's head to the side lets them flow out of the eye. Intraoperatively, I irrigate copiously to create a positive hydrostatic pressure before replacing the flap.

DR. KANELLOPOULOS: I use nonpowdered gloves and an aspirating speculum. I avoid any manipulation of the flap. I drape patients' upper lids when using the ACS or Krumeich-Barraquer microkeratome to avoid interference with the upper lashes; and I drape the lower lids when using the Hansatome or Moria because those devices touch the lower lashes.

DR. CARLSON: Prior to reflecting the corneal flap, I wring out a Merocel sponge that was moistened with BSS and dry the gutter. This produces a dry bed when the flap is lifted, allowing treatment without further drying or manipulating. My co-managing doctors have noticed a significantly improved interface with this technique.

TREATING FLAP COMPLICATIONS

DR. WILSON: For partial cuts, I replace the flap, wait three months and recut the cornea. For buttonhole flaps with central scarring or epithelial ingrowth, I use transepithelial PRK to remove the central flap completely. I've performed this in two of my own patients and about 15 referred patients. The transepithelial PRK is done two weeks after the first attempt when BCVA is as close to preop as possible.

Relation Between Optical Zone, Transition Zone, Refraction and Halos
Measure	Statistical Relation to Halos
Pupil size	No
Limbus	No
Optical zone	No
Keratometry	No
Pachymetry	No
Transition zone	Yes
Preoperative refraction	Yes

- MIHAI POP, M.D.

DR. DONNENFELD: I treat a free cap with a bandage contact lens for patient comfort; an antibiotic until the eye re-epithelializes and Pred Forte q.i.d. tapered over three months. Well-healed eyes usually achieve 20/30; a poor result might require lamellar keratoplasty.

DR. CARLSON: Once the flap is created, I lift it to make sure that it's not exposed to asymmetric hydration. The ablation is performed efficiently; the flap is repositioned; and the bed is briskly irrigated with 2 cc of BSS.

DR. DONNENFELD: I try to maintain an intact epithelium to maximize adherence to the flap. I examine every patient 15 minutes after LASIK, and use a Q-Tip to gently smooth out any microstriae. This works extremely well for high myopes.

DR. POP: I immediately remove the speculum to stop corneal dehydration after the flap is replaced; striae are created through excessive flap desiccation that can occur within a minute or two of the procedure. The most important thing is to examine the gutter after 10 to 15 minutes. If the gutter is not completely symmetric, I irrigate the flap slightly and replace it.

We no longer shield the eye. Many patients displace their flap by wiping their eyes and they'll try to reach under any shield. Patients are instructed to go home and sleep for three to four hours. Since using this protocol, our striae rate is less than I percent.

DR. KANELLOPOULOS: I try to create a thick flap, and agree that sufficient lubrication is key immediately postop to prevent the flap from dislodging due to blinking. I prefer that the eye remain open with the aspirating speculum for two minutes to avoid the mechanical stresses of the lids on the flap. I examine the patient 15 minutes postop for any striae.

DR. WILSON: I allow the flap to adhere for 30 seconds. We insert a Soflens 66 bandage contact lens for the first night. This adds to patient comfort and protects the edge of the flap from eyelid movement. Even a slight displace-ment, just a partial lifting of the flap, can be enough to produce significant striae or allow epithelial ingrowth.

DR. CARLSON: I exam the patients at the slit lamp with indirect retroillumination. In the early postoperative period, in cases of central striae, I perform a retinoscopy. This is extremely helpful to assess the significance, particularly if I can see that the defect on the retinoscopic streak matches with what I see at the slit lamp. Other tests include fluorescein staining for pooling in the trough of the striae, and comparing the quality of vision with a rigid contact lens to their best-corrected spectacle acuity. This can help determine if a corneal irregularity exists causing reduced quality of vision.

DR. DONNENFELD: I massage striae on the first day of surgery with a Q-Tip and a topical anesthesia. For striae between one and four days, I refloat and slightly stretch the flap. From five to 10 days, I refloat the flap and apply heat to relax the collagen fibrils so we can reposition the cornea with hypotonic saline. For folds or striae of two weeks and longer, I debride the epithelium, then using hypotonic saline, lift and heat the flap. I replace and massage it with a Merocel sponge and apply a bandage contact lens. A very hypotonic tear soaks the bandage contact lens, keeping the cornea edemic and preventing reformation of the striae.

DR. WILSON: If a patient complains about vision in the first few days after surgery and has striae, I refloat the flap using 50% BSS to maintain a hypotonic environment. When the flap is first replaced, some striae are apparent at the slit lamp; over the next 24 hours these resolve.

DR. KANELLOPOULOS: I take no action when striae are present in a happy 20/20 patient. If they reduce BCVA, cause glare or irregular topography, I use a combination of hypotonic solution and hyperthermia. I use a golf-club spatula dipped in a sterile hypotonic solution preheated to 65° C; applying this irons out the striae from the retracted flap by softening the collagen fibrils. A preheated Johnston applanator is placed over the repositioned flap at the end of the procedure to press out the folds.

DIFFUSE LAMELLAR KERATITIS

DR. CARLSON: I aggressively treat patients who present on day one with even mild DLK with topical corticosteroids. I have placed a few patients on oral corticosteroids, and sometimes oral doxycycime. If patients on hourly topical corticosteroids worsen the next day, then I irrigate under the flap. All my patients with DLK also had some degree of rosacea and significant meibomian gland disease. It's possible that these patients have a propensity for white cell migration into the cornea. Infection must be considered in the differential diagnosis in any patient with corneal inflammation postoperatively.

DR. POP: It is difficult to overtreat DLK. Often, the condition presents only in the upper or inferior quadrant of the cornea and extends only I or 2 mm. It's best to prescribe Pred Forte every hour and watch patients carefully, because the condition can worsen over two to three days.

DR. DONNENFELD: I use 60 mg ofprednisone for three days orally for significant DLK. My threshold for lifting the flap and irrigating is low. I am careful not to scrape the stroma and irrigate aggressively with BSS.

DR. KANELLOPOULOS: I'm very aggressive in irrigating the interface. Although I can't statistically support it, I see more DLK when I am unable to use an aspirating speculum. I recently had a case diagnosed as DLK that was actually ciprofloxacin deposits. Now I strictly adhere to more soluble antibiotics.

DR. WILSON: Appropriate irrigation after ablation is critical in reducing DLK. In substantial DLK cases, lift the flap and irrigate to avoid necrosis along the interface.

DR. WILSON: After taking fungal and bacterial cultures, I immediately prescribe fortified antibiotics; my regimen of choice is vancomycin 15 mg/mL and amikacin 20 mg/mL every hour around the clock.

DR. KANELLOPOULOS: I have not seen bacterial keratitis, but my choice would be fortified tobramycin 12 to 14 mg/mL with a cephalosporin (Cefuroxime 50 mg/mL). I have consulted internationally in a referred fungal keratitis case. That is challenging clinically, because the cultures usually take several weeks, and meanwhile it's difficult to treat a LASIK patient with antifungals, even if it is the differential diagnosis. This is one of the reasons why I adhere to a strict sterility protocol.

DR. CARLSON: I've treated a patient with culture-proven Bacillus cereus keratitis following flap lifting and irrigation for DLK. It returned aggressively with an opaque flap and a melting, necrosing hinge. I immediately lifted the flap, irrigated and applied amikacin and vancomycin under it. The patient was admitted to the hospital and eventually recovered 20/25 visual acuity, and was happy enough to have the other eye treated. If identified early and treated aggressively, these patients can still have a good outcome.

DR. POP: I re-treat undercorrections as soon as I diagnose them, but regression requires a stable refraction before re-treatment, usually two to three months. Overcorrected patients may also be treated immediately postop.

DR. WILSON: I wait three months to treat an undercorrection or regression. I have never seen epithelial ingrowth beneath flaps I've lifted, even on cases more than a year out. On the other hand, I've consulted on patients who have had displaced slivers of stroma that occurred during flap recutting for enhancement. Where there's crossing of the initial interface with the enhancement interface you risk some unusual tissue displacement. If this happens, severe irregular astigmatism can occur.

DR. KANELLOPOULOS: When recutting a flap, it's very important to use the same microkeratome to avoid transecting the original flap. With proper technique, it is possible to lift the flap one-year postop.

DR. POP: I lift the flap for all re-treatments. I don't use a contact lens after the initial surgery, but I always place a contact lens after a re-treatment.

DR. CARLSON: I recut only if there is a significant anomaly of the initial flap. Initially, we were taught that lifting was best for re-treatments in the first six months; recutting was suggested after six months. The current thinking is that there is no time limit for flap lifting in eyes with no neovascularization or scarring at the flap edge.

Drs. Donnenfeld and Wilson consult for Allergan; Drs. Carlson, Kanellopoulos and Pop do not consult for any of the products or manufacturers mentioned.