A 49-year-old black male presented to my office for a routine LASIK consultation as a result of the poor tolerance for contact lenses (worse in his right eye) that he had developed over the previous few years. The patient had no history of medical or ocular problems prior to this evaluation.
His preoperative examination revealed a UCVA of 20/200 OU. The patient had manifest refractions of -5.00 -1.00 X 75 OD and -4.25 sphere OS, both yielding 20/20 BCVA. Central pachymetry as measured by ultrasound was 476 µm OD and 496 µm OS. The patient's keratometry readings were 45.50/47.25 D OD and 45.25/46.25 D OS. The corneal slit-lamp examination revealed no scarring in either eye, but corneal topography showed a typical keratoconic pattern in the patient's right eye (Figure 1).
I diagnosed stage I asymmetric keratoconus based on Krumeich's original classification of the disease.1 Stage I is defined as eccentric corneal steepening, induced myopia, astigmatism of less than 6.00 D, keratometry readings of less than 48.00 D, and no corneal scarring.HOW WOULD YOU PROCEED?
1. Is this patient a good candidate for LASIK?
2. If not, which refractive surgery procedure would you offer to this patient?
3. Would you instead propose a penetrating keratoplasty as a definitive treatment?
LASIK performed in a patient who has clinically evident true or forme fruste keratoconus is known to worsen the cone or induce keratoconus.2 This patient was a poor candidate for LASIK owing to his eccentric steep and thin corneas—an unexpected finding in moderately high, compound myopic astigmatism. Nevertheless, I considered it premature to rush the patient into undergoing a relatively high-risk and longer-rehabilitative procedure such as penetrating keratoplasty, especially because he lacked corneal scarring in either eye.
The FDA approved intrastromal corneal ring segments (Intacs; Addition Technology, Inc., Des Plaines, IL) for the treatment of low levels of myopia, and these segments have been popular in the international ophthalmic community for the treatment of keratoconus.3 In his recently published surgical review article, Joseph Colin, MD, of Bordeaux, France, showed 4-year stability in the cone progression of the first keratoconic patient he treated with Intacs implantation.4 He also proposed a nomogram for using the segments to treat Krumeich stage I and II cones.
My patient underwent the standard 10-step Prolate System procedure in his right eye for Intacs as used to treat myopia, with three exceptions. First, I made the initial corneal incision temporally at 180º. Second, the depth of this incision was based on my setting the diamond blade to 70% of the thickness of the average measured pachymetry reading over the incision site. Third, I employed a thicker, 0.35-mm segment inferiorly in order to move the cone upward, and I used a thinner, 0.25-mm segment superiorly to achieve an additional flattening effect centrally. The 0.35-mm and 0.45-mm segments are still unavailable to US surgeons. I placed a single 10–0 nylon interrupted suture in the incision and removed it at the 2-week postoperative visit.
The patient's refraction and corneal topography remained stable from months 6 through 12 during the postoperative period, and his manifest refraction at 1 year was -2.25 -2.25 X 85, which was correctable to 20/20 and much reduced from his preoperative starting point.
As noted by Dr. Colin (oral communication, October 2002) and Britt Buckley, MD, of Colorado Springs, Colorado (oral communication, May 2001), there are few reported cases of performing PRK or LASEK over Intacs placed for keratoconus. I presented this option to the patient after his refraction stabilized at 1 year. He understood that the ultimate risks of the procedure were the inducement of frank ectasia and a loss of BCVA that would necessitate a corneal transplant.
The patient decided to undergo LASEK on his right eye 1 year after its treatment with Intacs segments. I used a standard technique of 20% ethanol diluted with BSS (Alcon Laboratories, Inc., Fort Worth, TX) for 20 seconds. His epithelium completely re-epithelialized at 3 days, and I removed his bandage soft contact lens.
Five months after the LASEK procedure, the patient's UCVA was 20/20 with a residual manifest refraction of +0.25 -0.75 X 65. At this postoperative examination, the Orbscan IIz topographer (Bausch & Lomb Surgical, Inc., San Dimas, CA) displayed surprisingly unremarkable axial topography with persistent steepening of the posterior float, a finding still suggestive of his keratoconic disease (Figure 2). The patient used topical steroids for
3 months after surgery but demonstrated no corneal haze at his most recent examination 5 months postoperatively. He claimed that the UCVA in his right eye was superior to and more comfortable than that of his left eye, corrected by a gas-permeable contact lens. Within the next few months, the patient will undergo implantation of Intacs segments in his left eye as part of this two-step procedure.
Despite the success of LASEK performed over Intacs segments in this patient, I do not believe that this procedure is the answer for all patients with keratoconus. As iterated by Dr. Colin,4 Intacs segments are an effective alternate treatment option for keratoconus in patients with Krumeich's disease stage I or II. Patients with corneal scarring are definitely poor candidates for the procedure. In addition, the nomograms for ideal ring selection and positioning are still undefined but are under investigation. More importantly, patients must complete an exhaustive informed consent process before undergoing any surface ablation technique after receiving Intacs to treat their keratoconus.
1. Krumeich JH, Daniel J, Knulle A. Live-epikeratophakia for keratoconus. J Cataract Refract Surg. 1998;24:456-463.
2. Lafond G, Bazin R, Lajoie C. Bilateral severe keratoconus after laser in situ keratomileusis in a patient with forme fruste keratoconus. J Cataract Refract Surg. 2001;27:1115-1118.
3. Colin J, Cochener B, Savary G, et al. Intacs inserts for treating keratoconus; one year results. Ophthalmology. 2001;108:1409-1414.
4. Colin J, Velou S. Current surgical options for keratoconus. J Cataract Refract Surg. 2003;29:379-386.