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6th Annual Refractive Surgery ReportRefractive Options Come Full Circle ... Back to Contact LensesMany colleagues believe that refractive surgery threatens our contact lens practices. In truth, it’s presenting new opportunities.Barry M. Weiner, O.D. Phoenix, Md. Sidebars: During the last decade, many patients have told us they want to get rid of their spectacles. Fortunately for us, many asked for contact lenses. More recently, however, this same group of discontented spectacle wearers has been turning to refractive surgery. Does this mean our contact lens practices are doomed? No way! Many post-refractive surgery patients will need enhancements—and most of them will be even less inclined to wear glasses than they were before they had the procedure. This ushers in new opportunities for our practices and new challenges. We must contend with very different clinical and psychological factors. We need to handle these patients with kid gloves, but if we can alleviate their problems and provide them with good vision, they’ll become our most loyal patients. Here’s how you can sharpen your skills so you can effectively fit refractive surgery patients and provide them with solutions they can live with. Psychological Barriers Helping failed refractive surgery patients get past their anger and put their faith in you will be your first and, perhaps, most difficult challenge. They’ve been let down. They’ve spent a lot of money on a procedure they believed would free them of their glasses. They didn’t want to wear spectacles before surgery, and most of them won’t want to wear them now. What’s more, many of them feel hopeless because they’ve failed with contact lenses in the past. On the bright side, when you fit these patients you’re giving them a solution that can put an end to years of disappointment. It’s not easy. They’re not only unhappy; they’re difficult to fit. So, you need to make additional time in your schedule. Sometimes the first pair of lenses works well for these patients, but not always. Prepare patients for multiple visits. Let them know they may have to try a few different lenses before they’re satisfied. You also should mention that, ultimately, a fit may not be possible if, for example, the eyes are too dry. Don’t surprise these patients with long, tedious fitting processes. Remember, the individual in your chair is disappointed and was probably a contact lens failure when his corneas were normal. Now, he expects you to perform a miracle. Let him know that this will take time and that you’ll have to work extra hard to solve his problem. If you don’t prepare him, and the first few fittings don’t take, he may lose faith and end up as unhappy with you as he is with his surgeon. Another psychological obstacle you’ll encounter: fees. Patients who have had refractive surgery have already paid a lot of money for something they’re disappointed with. Don’t surprise them with higher-than-normal exam fees and, possibly, expensive specialty lenses that they never thought they would need. Simply explain that your fees will reflect the amount of time the individual requires. The bottom line: You can offer something to failed refractive surgery patients that no one else could—freedom from glasses. For this, they will be eternally grateful. Necessary Tools Refractive surgery patients may present with poor acuity, flare and glare, dry eyes or poor tear flow across the cornea. Some may have irregular astigmatism or corneal distortion due to either poor healing or decentered ablations. You’ll encounter over- and under-corrections, and possibly anisometropia. They’re not your typical contact lens patients. They present complex problems that require more thorough exams, additional instrumentation and innovative solutions. A corneal topographer is essential for selecting the initial lens and for following any lens-induced changes to the cornea. It can also detect irregular astigmatism, decentered ablations or distortion the surgery caused. Corneal topography is also a good starting point to begin your initial fitting. Check the topography and design a lens accordingly. In most cases, you won’t be fitting the central cornea; you’ll be fitting the paracentral cornea (see figure 1). Each patient’s needs differ, so you’ll need to get creative with contact lenses and possibly begin fitting different designs. You’ll need to integrate RGPs into your practice. Some patients may not be able to tolerate RGPs and will need a specialty soft lens, but more often than not, these patients can achieve better acuity with RGP lenses. Reverse geometry lenses also may become part of your armamentarium, as will aspheric designs. And, in almost all cases, you’ll need to use large diameter lenses of 9.5mm or greater. Again, the two major tools you’ll need are empathy and patience. The patient’s disappointment will be as challenging as his corneal health. Radial Keratotomy Although some patients had good results following radial keratotomy (RK), a fairly large number did not. The Prospective Evaluation of Radial Keratotomy (PERK) study concluded that long-term corneal instability is a consequence of RK, and many RK patients who were initially successful have become hyperopic over time.1 The major problem with trying to fit the post-RK cornea is that its curvature is completely different from that of a normal cornea (see figure 2). RK incisions steepen the periphery and flatten the center. Because of the changed topography, post-RK keratometry is practically useless in fitting these individuals. A better indicator for the initial trial lens would be the pre-op K reading. Doctors typically prefer RGP lenses over soft for these eyes. Soft lenses may cause vascularization in the incisions due to the hypoxia that can result from a tight fit. In one study, 48% of post-RK eyes fitted with soft lenses developed significant vascularization within 7 months of fitting.2 This figure was even higher with the early RK procedures that cut through the limbus. Select an RGP lens that is slightly flatter than the pre-op flat K. Do this because you’re fitting the peripheral cornea, which is about the same as it was prior to RK, vs. the central cornea, which had been changed during surgery. Select your trial lens base curve by measuring the K value about 3.5mm superior to the optical axis. Studies have shown this is the optimum K reading.3 The steepest area of an RK patient’s cornea is somewhere in the mid-periphery. Because lenses tend to center around the steepest area, you’ll need a lens diameter of 9.5mm or larger to get good centration. The lens must be large enough to completely cover the pupil. Any infringement of the lens edge or peripheral curves may cause excessive glare in low light. If a speherical lens does not give adequate centration, try an aspheric or reverse geometry lens. The latter have steeper peripheral curves and flatter central curvatures, and the central-to-peripheral flattening ratios vary. This lens shape more closely aligns to the now flatter corneal shape, whereas the peripheral areas of the cornea remain much the same. The criteria for a successful post-RK fit are the same as those for a normal eye: good centration with adequate tear exchange, minimal bearing on any area of the cornea, good lens movement and good visual acuity. However, fits can be more difficult when patients present with more serious, immediate postoperative complications. The PERK study reported immediate post-RK complications of corneal perforations, scarring, corneal vascularization, microcysts in the RK incisions, band keratopathy, glare and diurnal visual fluctuations.1 Corneal distortion and irregular astigmatism have also been reported. When such cases present, follow-up evaluations are more necessary than ever to further reduce the risk of complications during the fitting period. After you complete the fitting, see these patients at least every 6 months. Many physical factors make fitting post-RK patients difficult: irregular corneal topography, decreased endothelial function, a disrupted tear film, fluctuating VA and unstable corneal rigidity. Each case is unique, so don’t be afraid to experiment with RGPs, reverse geometry lenses, and soft torics or bifocals. It depends entirely on the patient’s unique needs. Be creative. Laser Vision Correction Laser vision correction is now the big boy on the block, with more centers opening and greater advertising hype pulling patients into this visual correcting modality. Thorough pre-op evaluations and improved surgical techniques usually produce good results, but occasionally problems can arise that decrease the patient’s vision. The primary challenge you’ll face with post-LASIK is irregular astigmatism. Typically, it’s due to poor flap positioning, poor healing or decentered ablations. In such cases, clinicians prefer RGPs because RGPs mask irregular astigmatism. Selecting an initial trial lens for these patients is problematic because their topography is different from the normal, unoperated eye. A good rule of thumb is to try to align the base curve with the curvature of the cornea in the transition zone of the ablation. Fitting the transition zone curvature will give a mid-peripheral alignment fit. As with RK, however, there will be central tear pooling over the ablated area (see figure 3). If this vaulting is excessive and you notice air bubbles, you may need a reverse geometry design to achieve better centration and physiology. If central pooling is excessive, reverse geometry will align the lens better to the changed corneal topography. Remember, it’s flatter in the center and steeper in the periphery. Also, you’ll need large-diameter lenses. Large RGPs such as the Infinity Post Surgical lens or the MacroLens, with diameters of 10.0mm-15.0mm, may achieve good centration. You can counter post-LASIK complications such as flare and glare with tinted lenses. Or, if large pupils cause these phenomena, try a lens with an artificial pupil. I’ve also found that you can reduce pupil size and help alleviate glare by recommending diluted pilocarpine at night for driving. However, this is a controversial treatment. Central islands after LASIK usually flatten by themselves with time, but contact lenses can provide better vision until then. Patients who have been under- or over-corrected but otherwise have no problems can usually get an enhancement after waiting 2-3 months to ensure complete healing. If there’s little or no irregular astigmatism, you can fit many post-PRK and -LASIK patients with soft lenses. One study found that 38% of post-PRK subjects could be successfully fit with hydrophilic lenses.4 But, keep in mind that vaulting of the central cornea may cause the patient’s vision to fluctuate between blinks. If this is more tolerable to the patient than an RGP, there’s no reason not to use a soft lens. Refractive surgery is here to stay, and it may decrease the pool of potential contact lens wearers. But it will also open a new door when the surgical result is not what the patient expected, when the effect regresses or when the patient’s needs change. When this occurs—and it’s beginning to now—you can welcome your new specialty lens patient with open arms. u
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| Case History:
RK followed by LASIK
A 46-year-old male had RK on his right eye only in 1989. In 1992, when he first came to our office, he had eight RK incisions and still showed fluorescein in almost all the incisions. He needed a contact lens to restore his vision. His pre-op Rx was -3.50 -0.50 x 90 with 20/20 acuity. His post-op Rx in 1992 was +7.50 -0.50 x 90 with 20/50 best-corrected spectacle acuity. The untouched left eye had an Rx of -3.00D sphere with 20/20 acuity, and he opted not to have RK in that eye. We tried numerous lenses, including reverse geometry designs. The lens that centered best and seemed to move well was an Envision biaspheric lens with an 8.30mm base curve, a 9.60mm overall diameter and an Rx of -2.75D. With this lens, his acuity was 20/25. The lens centered temporally but moved well enough to give a good physiological response, and was large enough to give complete pupillary coverage and adequate vision. He wore this lens up to 14 hours a day until December 1999 when he underwent bilateral LASIK. After one LASIK enhancement, he is no longer wearing contact lenses. He is now 20/25 in his right eye and 20/20 in the left. |
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| Case History: Epithelial Fold A 33-year-old female high myope who had LASIK in 1998 had successfully worn RGP lenses for 15 years prior to that. Her pre-op Rx was -10.75 -2.00 x 170 O.D., -11.00 -2.00 x 180 O.S. Her visual acuity with the contact lenses was 20/20 O.U. The left eye had a normal healing course with no complications. The right eye had a vertical fold in the epithelium and extremely distorted topography. This central distortion was treated with steroids. Following surgery, her best-corrected visual acuity in the right eye was 20/50 with a spectacle Rx of +5.00 -3.00 x 15 (see figure 4). The left eye was 20/20 uncorrected. We trial fit her with several different lens designs, including spherical and aspheric lenses, Plateau reverse geometry lenses, and Infinity Post Surgical lenses. None centered well enough to give her usable vision. A reverse geometry aspheric lens (RK Bridge II by Conforma Laboratories) gave centration and a good visual result with acuity of 20/25. The lens has a 38.00D central base curve with a 42.00D peripheral aspheric curve and an overall size of 10.00mm with a -5.00D power. The patient is currently wearing this lens for more than 14 hours a day with no problems. Biocompatibles’ survey found that 75% of soft contact lens wearers would enjoy learning about new products and advances, and 68% say they would pay more if they would benefit. That gives you something to work with over the next decade.—J.S.E. |
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