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Up Front | Jan 2003

Refractive Challenge

LASIK Epithelial Sliders


CASE HISTORY
A 48-year-old white female with a 30-year history of RGP lens wear presented for bilateral LASIK. She had a preoperative manifest and cycloplegic refraction of -11.00 +5.50 X 27 OD and -11.00 +5.00 X 135 OS. Her BCVA was 20/25- OD and 20/30 OS. The slit lamp examination was unremarkable for any sign of map-dot-fingerprint dystrophy or other corneal abnormalities, and the fundus examination was within normal limits OU. Topography revealed bilateral, symmetric, regular bowtie astigmatism (Figure 1).

My surgical staff prepped the patient with povidone-iodine and took great care not to let it touch the ocular surface. Using moist sponges, they rinsed the povidone-iodine from the eyelids. They guided the patient into the laser suite and placed one drop of 0.5% proparacaine hydrochloride ophthalmic solution in her right eye. A 3M Steri-Drape 1024 (St. Paul, MN) was used to cover the meibomian gland orifices and evert the eyelashes. After placing a Barraquer wire speculum, I applied another drop of 0.5% proparacaine and performed central corneal pachymetry, which showed 596 µm of central tissue. I thoroughly dried the inferior and superior cul-de-sac with Merocel sponges (Medtronic Merocel, Mystic, CT) and then introduced the Amadeus microkeratome (Advanced Medical Optics, Inc., Santa Ana, CA) into the field. Having previously tested the microkeratome, I confirmed an 8.5-mm ring and a 140-µm head. I obtained suction, and tonometry revealed an IOP of greater than 100 mm Hg.

I thoroughly moistened the corneal surface, and the microkeratome advanced with a steady pass. Upon reversal, however, there were multiple areas of central and peripheral epithelial sliding, sloughing, and defects (Figure 2). During retraction of the corneal flap, I found that the bed was smooth and the stromal flap was symmetrically intact.

I commenced laser ablation using the Star S3 excimer laser system with ActiveTrak 3-D active eye tracking (VISX, Inc., Santa Clara, CA). Next, I floated the corneal flap back into position with a Kritzinger-Updegraff cannula (Bausch & Lomb Surgical, San Dimas, CA). I used multiple Merocel sponges to dry the gutter and confirm the proper alignment of the flap. After 2 minutes of drying the cul-de-sacs and gutters, I used a slightly moistened Merocel spear to paint the epithelium back into its original position. The epithelium was dried for an additional 6 minutes, after which I placed a 1-DAY ACUVUE contact lens (Johnson & Johnson Vision Care, Inc., Jacksonville, FL) on the eye as a bandage.

HOW WOULD YOU PROCEED?
1. Would you perform LASIK in the opposite eye on the same day?
2. If not, would you allow the operated eye to heal and then proceed with LASIK in the second eye?
3. If there were sloughing but no epithelial defects, would you use a bandage contact lens?

SURGICAL COURSE
Due to the severity and location of the epithelial sloughing in the operated eye, I decided not to proceed with the second eye and informed the patient of the following strategy. First, I advised her to resume wearing her contact lens in the unoperated eye and to wait several weeks for the complete epithelial remodeling of her right eye, at which time I would determine the UCVA and BCVA. I recommended that, once the vision stabilized, she undergo a superficial keratectomy with a diamond bur to improve the epithelial attachments, but I also advised her that a flap-lift re-treatment might be required following the superficial keratectomy. I did not recommend lifting the flap and re-treating the eye without first performing a superficial keratectomy due to the possibility that a single lifting of the flap would activate uncontrolled epithelial remodeling and hypertrophy.1 Lastly, I planned to perform a superficial keratectomy in the left eye prior to the primary LASIK procedure.

Three days following the initial LASIK procedure, corneal topography of the right eye showed significant epithelial irregularities as compared with the preoperative topography (Figure 3). The slit lamp examination revealed multiple punctate changes of the epithelium with no evidence of Bowman's folds or flap wrinkles. The UCVA was 20/400 with pinhole vision to 20/40.

Ten days later, the patient's UCVA was 20/200 OD, but it improved to 20/25 -1 with a correction of -4.00 +2.25 X 167. Topography revealed a regular central cornea. One week later, the patient underwent a complete superficial keratectomy. After the eye had been prepped and draped in the usual manner, I used a 7-mm optical zone marker to create a groove in the corneal epithelium. I removed the epithelium with a No. 64 Beaver Blade (Beaver Inc., Boston). I also employed multiple dry and wet Merocel sponges to polish Bowman's layer. When it was thoroughly dried, I used an Ophtho-Burr (Medtronic Solan, Jacksonville, FL), a 5-mm-diameter, handheld, diamond polishing ball, to create fine scratches vertically and horizontally in Bowman's layer. Finally, I placed a bandage contact lens and applied Ciloxan (Alcon Laboratories, Inc., Fort Worth, TX) and Acular (Allergan, Inc., Irvine, CA) drops.

The patient re-epithelialized 3 days after undergoing the superficial keratectomy, and corneal topography revealed central corneal epithelial steepening typically seen after re-epithelialization. Over the ensuing 3 weeks, the central steepening resolved. The refraction showed a significant reduction in the astigmatism but also an increase in the degree of myopia. The patient's manifest refraction was -5.00 +1.25 X 175, and her BCVA was 20/25. I lifted the flap and performed a retreatment for the residual myopic astigmatism. Interestingly, there was no evidence of loose epithelium or sloughing during the lifting of the flap.

OUTCOME
One day after undergoing flap-lift retreatment, the patient's UCVA was 20/25, which matched her preoperative BCVA. The patient has maintained that visual acuity for 6 months since undergoing the retreatment, and her corneal topography has remained stable and regular (Figure 4).

The patient elected to undergo a superficial keratectomy in her left eye prior to proceeding with LASIK. During the superficial keratectomy, I observed that the epithelium was poorly adherent and easily removed with a No. 64 blade. Two weeks following the superficial keratectomy of the left eye, the patient underwent uncomplicated LASIK with the Chiron ACS microkeratome (Bausch & Lomb Surgical). The preoperative manifest refraction after the superficial keratectomy was -11.25 +4.50 X 135. There was no evidence of epithelial sloughing during the keratectomy. The patient's UCVA was 20/30 on the following morning. Six months postoperatively, I relifted the flap and re-treated her left eye for residual myopic astigmatism of -1.50 +0.75 X 106, and the patient achieved a UCVA of 20/25+.

DISCUSSION
Another way to manage this case might have been to contemplate a surface ablation procedure for the left eye. The patient's high correction could have led to corneal haze with PRK or LASEK, and the surgeon would have lost the ability to adjust the refractive outcome. LASIK offers the ophthalmologist the incredible ability to fine-tune the surgical outcome with a retreatment. Nevertheless, my experience has been that the LASIK surgeon loses this adjustability factor when operating on a weak, unstable epithelium. Addressing this problem at its root (by performing a superficial keratectomy) restores the advantages of LASIK's adjustability and accuracy.

Preoperatively, I make epithelial sloughing a key point in my discussion of risks with patients and inform them that I may not proceed with LASIK in the second eye if sloughing occurs in the first eye. Interestingly, a weakness in epithelial attachments is not always directly related to visible map-dot-fingerprint dystrophy. I believe that this sloughing represents a forme fruste degenerative condition of the corneal epithelium. I aggressively look for epithelial abnormalities preoperatively, and none of my cases of severe epithelial sloughing have had visible signs of map-dot-fingerprint dystrophy. Ophthalmologists often approach me at courses

I am teaching, and this is one of their most frequent complications. Many surgeons are frustrated because they believe that they missed the diagnosis preoperatively. That is not the case with this complication. I have attempted to test epithelial adherence at the slit lamp and have found that those patients I expected to slough did not do so during the keratectomy. I do not know of an accurately predictive test, and slit lamp manipulation alone yields too many false-positives to be a valid test.

In total, I have had five patients with severe anterior basement membrane dystrophy and histories of recurrent erosion who have undergone a superficial keratectomy before LASIK. Two patients chose LASIK over PRK or LASEK because they wanted a procedure that had the potential for fine-tuning. The remaining patients were poor candidates for surface ablation or a refractive IOL due to their extreme astigmatism and high myopia. These individuals had no sloughing with LASIK after their superficial keratectomy and have had stable results with no erosions for 2 or more years. It is important to note that all of these eyes had a refractive change following their superficial keratectomy. I believe that PRK or LASEK is not accurate in these patients, because the surgeon is operating on the manifest refraction of a diseased, irregular epithelium.

The microkeratome pass is the ultimate stress test of the epithelial attachments. Undoubtedly, the amount of stress varies greatly between microkeratomes and even between units of the same brand. For example, I have four ACS units that have rarely resulted in significant central sloughing (<1%), but, in my hands, the Moria CB (Moria Inc., Doylestown, PA) and the Amadeus microkeratomes resulted in an 11% and 40% rate of sloughing, respectively. I have even seen epithelial sloughing with the INTRALASE FS laser (IntraLase Corp., Irvine, CA), in which case the plate glass that gently applanates the cornea caused the epithelium to slide. It appears as if no one unit or technique is immune to this complication. Even if we had a femtosecond laser that did not require touching the epithelium, I doubt that this complication would disappear due to the reactive quality of the epithelium in these patients when the flap is lifted. Most likely, there is microscopic sliding of the epithelium, which results in focal areas of epithelial hypertrophy. I call this “reactive epithelium syndrome,” because simply lifting a flap with loose epithelium can result in a severe punctate epithelial keratopathy on the following day. I believe that the keratopathy can cause epithelial hypertrophy that, if patchy, can create an irregular surface and result in a loss of BCVA.

For this reason, surgeons should rule out a history of primary epithelial sloughing and reactive epithelial syndrome before recommending a wavefront-guided, smoothing laser treatment. Over my last 8 years of performing high-volume LASIK, reactive epithelial syndrome, diffuse lamellar keratitis, and epithelial ingrowth secondary to forme fruste epithelial basement membrane degeneration have been the most important unexpected complication of the procedure, and its management has been critical to maintaining both happy patients and a healthy refractive practice.

Stephen A. Updegraff, MD, FACS, is Medical Director of Updegraff Vision in St. Petersburg, Florida, and he specializes in corneal diseases and anterior segment surgery. He holds no financial interest in the products mentioned herein. Dr. Updegraff may be reached at (727) 822-4714; updegraffmd@upvision.com.

1. Updegraff SA. Reactive epithelial syndrome: A case report. Paper presented at: ISRS World Refractive Surgery Symposium; July 1999; Miami, FL.

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