CASE PRESENTATION
A 44-year-old white male presented for a routine LASIK consultation. He was a high myope who had undergone an epikeratoplasty (epikeratophakia) in his left eye 15 years earlier in an effort to decrease or eliminate his refractive error. At that time, the patient had decided against undergoing a procedure on his right, dominant eye, due to the slow and relatively painful postoperative course that the left eye had followed.

Upon presentation in my office, the patient's right, virgin eye had a UCVA of count fingers and a manifest refraction of -12.00 -2.00 X 030 yielding 20/25 vision. His left eye had a similar UCVA with a manifest refraction of -6.00 -1.00 X 145, which corrected his vision to 20/30. I measured his pachymetry using the Orbscan IIz (Bausch & Lomb, Claremont, CA); the patient was 580 µm OD and 797 µm OS centrally, which was confirmed ultrasonically. His maximum pupil size when measured in dim illumination with a Colvard Pupillometer (OASIS Medical, Glendora, CA) was 6.5 mm OU. The average keratometric values were 45.0 D in the right eye and 43.0 D in the left eye. Topographically, the left eye showed a characteristic central area of flattening and a relatively abrupt transitional steepening near the 3-mm zone, which was consistent with the patient's history of epikeratoplasty (Figure 1).

The patient was completely intolerant of wearing a rigid contact lens in his left eye and had not done so over the previous 8 years. He wore a soft contact lens in his right eye comfortably, and did not have backup spectacles, presumably due to the relatively high degree of refractive aniseikonia present. The patient also reported some age-appropriate symptoms consistent with presbyopia.

HOW WOULD YOU PROCEED?
1. Perform LASIK or PRK directly over the epikeratoplasty?
2. Remove the donor lenticule first and then perform LASIK or PRK?
3. Recommend a clear lensectomy or intraocular contact lens when available?
4. Revisit a rigid lens with a different design and not perform any further corneal surgery?

SURGICAL COURSE
After much discussion, we decided to address the residual refractive error in the patient's left eye in an effort to maximize its acuity, and then, if appropriate, correct the right eye. The protracted postoperative course following the patient's initial epikeratoplasty virtually eliminated any consideration of first removing the donor lenticule, allowing the eye to heal, and then proceeding with LASIK. Ideally, the patient's acuity would improve enough in the left eye to allow him to function without wearing a contact lens in his right eye prior to correcting that eye. I also decided to create the LASIK flap and perform the laser treatment on the same day.

During the initial slit lamp examination, the OS cornea showed a healthy tear film and what appeared to be a well-centered and healthy donor lenticule measuring 7.5 mm in diameter. All of the patient's sutures had previously been removed. Based on the right eye's pachymetry, I was able to determine that the onlay lamellar graft was approximately 200 µm thick centrally. I used a 9.5-mm ring and 180-µm head of a Hansatome microkeratome (Bausch & Lomb) in an effort to achieve a keratectomy of maximum depth, diameter, and integrity (Figure 2).

I used the Star S3 ActiveTrak laser (VISX, Santa Clara, CA). The initial refraction of -6.00 -1.25 X 145 called for a nomogram-adjusted treatment of -4.35 to 1.00 X 145, which I hoped would fully correct the refractive error or, alternatively, leave the patient slightly myopic. I was able to successfully create a large LASIK flap, well beyond the epikeratoplasty cicatrix and with a smooth central bed (approximately 5 to 6 mm), but with peripheral areas that appeared to have a very thin, irregular layer of tissue originating from the margin of the epikeratoplasty. I felt this was due to an intersection with and dissection of the prior epikeratoplasty. I placed a bandage contact lens over the eye after a successfully tracked laser ablation.

On the first postoperative day, the patient's visual acuity in the left eye was 20/200, the flap was smooth and well positioned, and I removed the bandage contact lens. Three weeks postoperatively, his UCVA was 20/80, improving to 20/40 with a refraction of +2.00 -1.75 X 160, and the patient was pleased.

I then focused on the patient's right eye. He was given a spectacle prescription so that he could remove the soft lens, and we scheduled LASIK surgery in that eye for 4 weeks later. On the scheduled day of the procedure, the right eye's refractive error was -12.50 -1.50 X 010 yielding 20/30 visual acuity, which was similar to the refraction and acuity obtained at the time the patient had first removed his contact lens and transitioned to eyeglasses. His left eye, however, had a UCVA of 20/400 and a dry refraction of +5.25 -1.00 X 090 yielding 20/25 vision. The slit lamp examination was normal. After discussing all the options, we decided to proceed with LASIK OD and to try a soft contact lens OS as an interim measure.

Again, I used a 9.5-mm ring and 180-µm Hansatome head, and I treated the refractive error in the right eye with a nomogram-adjusted ablation of -8.75 -1.20 X 010. The entire right eye procedure was uneventful.

One day following the LASIK surgery, the patient had UCVA of 20/50 OD and a healthy flap. I fitted him with an 8.7-mm Acuvue lens (Johnson & Johnson Vision Care, Inc., Jacksonville, FL) with a power of +4.00 for the left eye, which he tolerated well. Although I instructed the patient to return in 1 week, he cancelled the appointment, but noted over the telephone that he was comfortable and doing well. At a follow-up examination 2 weeks after his right eye LASIK procedure (and 9 weeks following his left eye procedure), his UCVA was 20/50 OD improving to 20/25 with -0.75 -0.75 X 050 and 20/400 OS improving to 20/25 with a refraction of +5.00 -0.25 X 085. The patient was happy with his vision overall, and had not been wearing the contact lens in his left eye, similar to his preoperative routine. He also reported that he was reading more comfortably.

At the 6-month examination after the primary LASIK OS, the patient's UCVA was 20/800 and his refraction, confirmed with cycloplegia, had progressed to +7.25 -0.50 X 090, which corrected his vision to 20/25. His LASIK flap was healthy, and his UCVA OD was 20/40, correcting to 20/25 with -0.50 -0.75 X 180. I decided to wait 2 weeks, repeat the refraction, and proceed with an enhancement of the left eye.

On the day of the enhancement, I used a Sinskey hook (Katena Eye Instruments, Denville, NJ) to initiate lifting of the existing LASIK flap. I programmed +3.75 into the laser in an attempt to conservatively correct the total refractive error of +7.25 -0.50 X 090. Again, I noted the bed had a very thin, irregular layer of peripheral tissue extending from the margin of the epikeratoplasty, well within the diameter of the LASIK flap.

OUTCOME
On the first day following the enhancement in the left eye, the patient's UCVA was 20/30 OS, and the flap was smooth and well positioned. He was comfortable and reported a dramatic improvement in his depth perception. I did not perform a refraction. At the patient's most recent follow-up examination, 10 months after the myopic ablation on his left eye and 4 months after the hyperopic enhancement on the same eye, his UCVA had remained at 20/30 OS with a refraction of +0.50 -1.25 X 167, correcting his visual acuity to 20/25. His right eye remained slightly myopic with a UCVA of 20/30.

This case highlights the fact that LASIK is less exacting on nonvirgin corneas than on virgin corneas, and can provide a multitude of refractive results in various settings. The initial overcorrection and progressive hyperopia in this instance most likely was due to the inherent biomechanical changes induced by an epikeratoplasty followed by an additional lamellar keratectomy, which could have been compounded by a laser ablation.

The only true, long-term healing between a donor tissue lenticule and host cornea after an epikeratoplasty occurs at the edge of the epikeratoplasty where there is stroma-to-stroma contact following the initial annular keratectomy. Centrally, where the stromal surface of the donor tissue lies directly on top of the host Bowman's membrane, there is no scar formation, which makes this area particularly susceptible to disruption (such as by a microkeratome) for an indefinite period of time following the initial epikeratoplasty. Such a lack of permanent healing in the central cornea following an epikeratoplasty, coupled with the manner in which it can respond to a microkeratome pass, is analogous to the way in which a cornea could potentially respond if a second LASIK flap was created, for the purpose of enhancement, too soon following an initial LASIK procedure. It is also interesting that the 7.5-mm diameter of the original epikeratoplasty lies just beyond but in close approximation to the edge of the 6.5-mm X 5.5-mm elliptical ablation zone used for the initial myopic treatment for the left eye.

Stephen C. Coleman, MD, is Director of Coleman Vision in Albuquerque, New Mexico. He holds no financial interest in any product mentioned herein. Dr. Coleman may be reached at (505) 821-8880; stephen@colemanvision.com