RA 39-year-old male underwent uneventful, bilateral, myopic LASIK with nasal hinges in 1996. His visual acuity regressed to -1.50D OU. By slit-lamp examination, the diameter of the flap in his right eye was 6mm with a nasal hinge. The surgeon performed a recut enhancement on the patient's dominant right eye in February 2004. He used the Hansatome microkeratome (Bausch & Lomb, Rochester, NY) with a 180-µm–depth plate and a 9.5-mm ring and the Star S4 excimer laser (Visx, Incorporated, Santa Clara, CA). After the laser ablation, a free sliver of stromal bed tissue was present that the surgeon could not reposition and therefore discarded. The crescent-shaped tissue was approximately 2.0 X 0.5mm and had been located along the temporal edge of the pupillary border.
The patient's postoperative course was complicated by severe, visually significant microstriae, which the surgeon successfully managed by relifting and refloating the flap and placing interrupted sutures that were removed 1 month later.
At present (4 years after the original procedure), the patient's UCVA is 20/200 OD, and his BCVA is 20/100 OD with a correction of -2.50 + 3.25 X 55. Slit-lamp examination shows the flap's edge but is otherwise normal. Orbscan topography (Bausch & Lomb) reveals irregular astigmatism (Figure 1), and Customvue wavefront maps (Visx, Incorporated) show mixed astigmatism with a higher-order RMS of 0.6µm.The patient was referred to a tertiary care center to determine if he were a candidate for treatment with the Custom Contoured Ablation Pattern (C-CAP; Visx, Incorporated), but the software could not formulate a treatment plan. Because the patient's right eye is dominant, he is visually disabled for many tasks. In addition, a fitting with rigid gas permeable (RGP) lenses failed to significantly improve his visual acuity. He is contact lens intolerant, and medical management to improve his success with contact lenses failed. The patient voices concern about relifting his flap because of the previous suture-related discomfort he experienced. He consults you regarding possible treatment options. A. JOHN KANELLOPOULOS, MD
This is a difficult case because of the highly irregular nature of the patient's cornea, a finding supported clinically by the refraction with high astigmatism and the loss of BSCVA. The wavefront map also shows a great degree of higher-order aberrations, the most notable of which is coma. The Orbscan axial map shows high astigmatism in the center that becomes very irregular toward the periphery around the 3- to 4-mm optical zone area. Of special note is the flattened inferior and temporal area straddling the pupillary border. This location is likely where the sliver of stroma was accidentally removed during the recut. On this highly irregular cornea, an enhancement with a wavefront-guided excimer laser platform will not work well, because the aberrations may well be out of the range of most wavefront measuring devices. In simple terms, the cornea may be too irregular to be treated with a wavefront-based procedure. Another consideration is tissue reserve. Wavefront-guided ablations remove tissue according to this rough formula: 3 X (maximal deviation - minimal deviation in microns). It may not be feasible to proceed with wavefront-guided ablation, even if the treatment could be calculated.
My colleagues and I have worked with the Allegretto Wave topography-guided platform (Wavelight Laser Technologie AG, Erlangen, Germany) during the last 3 years. We presented our data at the 2004 AAO annual meeting.1 I would attempt an enhancement with a topography-guided system, because the aberration/irregularity is corneal in origin. It will probably be feasible to obtain reproducible topographies and create a treatment plan.
The topography-guided software from Wavelight Laser Technologie AG that we have used will treat only the relatively steep areas of the cornea—somewhat like a selective phototherapeutic keratectomy (PTK)—in order to generate a smooth central corneal surface. Although we have been pleasantly surprised by such treatments in the past, I should note two caveats from our experience. First, one should not attempt to correct tilt during the topography-guided treatment (an option with the Wavelight platform), because this cornea is so irregular. Second, one should expect a smoothing effect on the cornea but also a possible refractive surprise, because the ablation will be highly irregular to match the irregular nature of this cornea.
My guess is that this eye would experience a myopic shift after such a treatment. I would perform surface ablation in order to avoid any additional flap-related complications. Specifically, I would proceed with a topography-guided PRK using adjunctive 0.2% mitomycin C (MMC) for 1 to 2 minutes, and I would explain to the patient that a second PRK might be necessary to treat residual spherical error.
I had a similar case; Figure 2 shows the pre- and postoperative topographies of the cornea. This eye had an old, contact-lens–related Pseudomonas corneal ulcer that was located slightly temporal to the visual axis. The paracentral cornea was relatively flatter and thinner as a result. In this case, I treated the -3.00 to -3.50D of irregular cylinder with a topography-guided procedure and believe I achieved a relatively satisfactory result. The difference map shown in Figure 2 depicts the actual laser ablation profile.DANIEL H. CHANG, MD,
AND DAVID R. HARDTEN, MD
This patient has mixed astigmatism and significant irregular astigmatism after a recut LASIK enhancement with a loss of tissue and postoperative microstriae. If the fitting with an RGP contact lens failed to improve his visual acuity, an etiology other than corneal astigmatism is highly likely. We would perform a careful slit-lamp examination for cataracts, other media opacity, and retinal pathology. An examination of the retinoscopic streak as well as the red reflex with an RGP lens in place would also be helpful.
On the Wavescan report provided, the quality index has two red boxes, which limit the report's reliability. Nevertheless, the wavefront pattern matches the topography fairly well. Assuming the slit-lamp examination reveals no obvious displacement of the flap or residual fragments in the interface, lifting the flap for further treatment would put the patient at risk for additional striae, irregular astigmatism, and other flap-related problems. Before beginning treatment, we would counsel the patient as to his potential future need for a corneal transplant.
The first treatment option in this case would be surface PTK (if possible, postponed until wavefront-guided mixed-astigmatism treatment packages for this level of astigmatism are available) with the application of MMC. If attempts at surface ablation failed to improve the patient's BCVA, we would consider flap amputation with MMC treatment. With only a 6-mm flap present, removing it would still not take away tissue from any area outside a future keratoplasty. Because patients are frequently myopic after flap amputation, customized PTK might then be an option. Finally, if further excimer laser treatment failed to improve his visual acuity, a penetrating keratoplasty would be the final option.Y. RALPH CHU, MD
This case demonstrates the risk of recutting a flap, even 8 years after the original LASIK surgery. Possible options for treating this type of irregular astigmatism include transepithelial PTK, flap removal, lamellar keratoplasty, and penetrating keratoplasty. Because it is impossible to determine from which part of the cornea the discarded tissue originated—stromal bed or flap—it is difficult to know whether managing this case with flap removal or transepithelial PTK would improve the patient's visual symptoms. Flap removal carries the risk of corneal haze and further development of irregular astigmatism through poor epithelial remodeling. Transepithelial PTK, meanwhile, has a limited role, because it would involve the removal of a potentially large amount of tissue in order to reach the level of the irregularity.
Another, more aggressive trial of RGP lenses could be tried. If the patient truly fails medical management, then I might perform a lamellar or penetrating keratoplasty to help resolve the irregular astigmatism. I would advise the patient that he will most likely still need some form of corrective eyewear after either of these procedures, but the goal would be to reduce his irregular astigmatism and improve his BCVA and functional vision.STEPHEN COLEMAN, MD
This particular patient has essentially two viable options. Initially, however, it is important to determine what not to do and then to choose between the two alternatives. It would be inadvisable to attempt to relift either LASIK flap in this setting due to (1) the evidence of a flap intersection from the two prior flaps oriented 90º apart by two different keratomes and resulting in a documented sliver of discarded stroma, (2) the 1-month history of sutures for microstriae that may reflect poor flap quality in general or poor side-cut quality specifically, and (3) the current Orbscan image that shows relatively thin central pachymetry and an area less than 2mm away that is 21µm thinner, both with a posterior float greater than 0.040mm, which may reflect ectasia.
Initially, I would leave the LASIK flaps as they are, particularly because the slit-lamp appearance (aside from an obvious flap edge) is reportedly normal. An RGP contact lens has been tried and failed, and a crystalline lens-based procedure would avoid altogether the area where the problem resides. A C-CAP procedure on a Star S4 excimer laser could improve this patient's vision, but, as is the case here, it is often difficult to capture data and formulate a treatment plan for an eye that has a surface topography this complex. My experience with C-CAP is that it effectively treats prior decentrations, particularly those that are post-PRK, but that the technology is not as efficient in postoperative eyes with keratome-related irregular topography.
The two remaining alternatives are a relatively aggressive grafting procedure (either lamellar or penetrating) or, more simply, a wavefront-guided PRK as an initial procedure. I would recommend the latter for obvious reasons in hopes that at least some normal surface topography could be restored and that visual rehabilitation, on some level, would become less difficult. I would counsel the patient that he will likely require at least two surface treatments to achieve a satisfactory result using this approach.
Although it is normally my preference, using the laser to remove the epithelium in this setting would not provide a sufficiently large diameter to accommodate the refractive treatment profile. Additionally, I would avoid using the larger, hyperopic Amoils brush (Innova Medical Ophthalmics, Mississagua, Ontario, Canada), which could disrupt the underlying flaps that have already been difficult to seat, and heal, smoothly. Using 20% diluted ethanol, similar to a LASEK procedure, is the safest option, and I would add 10 to 15 seconds to my customary waiting time to ensure easy removal of the entire intended area of epithelium. Next, I would perform a straightforward PRK procedure using the wavefront data, which closely correlate with the objective manifest findings despite the fact that the BCVA is limited. A preoperative refraction over a hard contact lens would provide additional useful information.
In December 2004, the Visx laser received approval from the FDA for customized wavefront-guided hyperopic astigmatic corrections. I have found that, because highly aberrated eyes such as this one often present a broad range of varying wavefront information, serial measurements at different times (taken to get at least one measurement that falls within the currently approved parameters) can be beneficial. Alternatively, it may be necessary to wait until the treatment of this particular prescription is available commercially.Section editor Karl G. Stonecipher, MD, is Director of Refractive Surgery at Southeastern Eye Center in Greensboro, North Carolina. Dr. Stonecipher may be reached at (800) 632-0428; firstname.lastname@example.org.
Daniel H. Chang, MD, is Attending Surgeon at Minnesota Eye Consultants, PA, in Minneapolis. He states that he does not hold a financial interest in any product or company mentioned herein. Dr. Chang may be reached at (612) 813-3692; email@example.com.
Y. Ralph Chu, MD, is Medical Director of the Chu Vision Institute in Edina, Minnesota. He states that he does not hold a financial interest in any product or company mentioned herein. Dr. Chu may be reached at (952) 835-1235; firstname.lastname@example.org.
Stephen Coleman, MD, is Director of Coleman Vision in Albuquerque, New Mexico. He states that he does not hold a financial interest in any product or company mentioned herein. Dr. Coleman may be reached at (505) 821-8880; email@example.com.
David R. Hardten, MD, is Director of Refractive Surgery at Minnesota Eye Consultants in Minneapolis. He is a consultant to Visx, Incorporated, and TLCVision. Dr. Hardten may be reached at (612) 813-3632; firstname.lastname@example.org.
A. John Kanellopoulos, MD, is a corneal and refractive surgery specialist. Dr. Kanellopoulos is Director of Laservision.gr Eye Institute in Athens, Greece, and practices in New York as well. He is Attending Surgeon for the Department of Ophthalmology at the Manhattan Eye, Ear, and Throat Hospital in New York and Clinical Associate Professor of Ophthalmology at New York University Medical School in New York. He states that he does not hold a financial interest in any product or company mentioned herein. Dr. Kanellopoulos may be reached at +30 21 07 47 27 77; email@example.com. Kanellopoulos AJ. Topography-guided LASIK enhancements: early experience in 17 symptomatic eyes. Paper presented at: The AAO/SOE Joint Meeting; October 26, 2004; New Orleans, LA.