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Up Front | Oct 2002

Refractive Challenge

Incomplete LASIK Flaps

CASE PRESENTATION
A 47-year-old white male presented for bilateral hyperopic LASIK. The patient's UCVA was 20/100 OD and 20/150 OS. His manifest refraction was +3.25 sphere OD and +3.5 sphere OS, and his cycloplegic refraction was +3.75 sphere OD and +4.0 sphere OS. The BSCVA was 20/20 in each eye. His pupils measured at 5.7 mm OU in dim light with the PupilScan II (Keeler Instruments, Broomall, PA). Schirmer 1 testing was normal, as were the slit lamp, dilated retinal, and external examinations. The patient's IOP and visual fields were also normal. Topographic examination with the Orbscan (Bausch & Lomb, Rochester, NY) revealed a normal anterior and posterior corneal surface of both eyes (Figure 1).

We conducted a thorough informed consent process. The patient then underwent bilateral hyperopic LASIK with an SKBM nasal-hinge microkeratome (Alcon Laboratories, Fort Worth, TX) and the LADARVision Excimer Laser System (Alcon Laboratories). Surgery in the right eye was uneventful, but the left eye suffered an incomplete flap; the vertical hinge essentially transected the visual axis (Figure 2).

After a careful review, I decided to abort the surgery, because I did not feel that safe laser ablation was possible. I irrigated and replaced the incomplete, but otherwise normal, flap in a standard fashion. Finally, I advised the patient that surgery could not be completed in his left eye, and we discharged him following standard protocols.

HOW WOULD YOU PROCEED?
1. Would you have completed the flap by manually dissecting the lamellar bed until the hinge was out of the treatment zone?
2. Would you position the excimer laser ablation within the available lamellar space and protect the hinge?
3. Wait 3 to 6 months (managing the patient with contact lenses or spectacles), recut the flap, and proceed with the treatment?
4. Perform PRK?
5. Consider an alternate surgical modality, such as CK, implanting a phakic IOL, or refractive lens exchange with or without a multifocal IOL?

SURGICAL COURSE
Despite advances in keratome design and our understanding of the procedure, incomplete LASIK flaps still occur, although rarely. Several researchers estimate that the incidence of incomplete keratectomy is between 0.064% and 4.0%, with a lower rate for newer microkeratomes.1-7 Nevertheless, the incomplete keratectomy is generally considered a relatively common intraoperative complication.

Incomplete flaps occur due to (1) a mechanical interference of the traversing microkeratome head by the lids, drapes, speculum, or conjunctiva (Figure 3); (2) a loss of vacuum in the suction ring during microkeratome translation; (3) a mechanical failure of the microkeratome; and (4) an electrical failure of the microkeratome motor(s) or console. A patient's anatomy or sudden movement may cause mechanical interference or a sudden loss of ring suction, both of which may produce an incomplete flap.

If the hinge significantly obscures the centered ablation profile, then laser treatment of the exposed lamellar bed immediately after an incomplete keratectomy is not advisable. The treatment has resulted in severe irregular astigmatism and corneal haze, which both lead to a loss in BCVA, glare, halos, and poor night vision.8,9 Some surgeons recommend completing the lamellar dissection manually with a sharp corneal blade in cases of an incomplete flap, but this technique risks creating an irregular, multiplanar flap and bed, and possibly a free cap, unless the hinge is outside the treatment zone.

When the incomplete flap occurs on the second eye during bilateral LASIK surgery, the patient is at a greater inconvenience due to anisometropia and aniseikonia. These patients do not tend to tolerate their spectacles and require a contact lens for the eye with the incomplete flap. Lens intolerance can lead to a period of patient dissatisfaction. For that reason, upon creating an incomplete flap, some ophthalmologists propose performing transepithelial PRK. With the advent of mitomycin C for corneal surface ablation, this technique may be helpful, as noted by A. Hastis, MD (written electronic communication, 2002). The common practice in such cases has been to evaluate the exposed lamellar bed immediately after creating an incomplete LASIK flap in order to determine if there is sufficient space for safely placing a centered excimer beam. If caliper measurements or projecting the beam profile on the exposed bed show that the area is insufficient, the surgeon aborts the procedure, replaces the flap, and reschedules surgery within 3 to 6 months. These patients' BCVA returns promptly, with minimal to no refractive or topographic change, according to study findings.10 After flap replacement and the patient's documented return to preoperative measurements, the surgeon discusses with him the available surgical and nonsurgical options. Most patients elect to have the corneal flap recut.

I saw the patient in this case on postoperative day 1. He was quite pleased with the early results in his right eye but was disappointed in general because of his imbalanced visual acuity. Examination of the right eye revealed a UCVA of 20/30, correctable to 20/20 with -1.00 sphere. The LASIK flap was secure with no folds or striae, and the interface was clear. The UCVA of the left eye was 20/200, and the BCVA, remarkably, was 20/25 with +3.5 sphere. The left eye's LASIK flap was secure without folds or striae, and the interface was clear. The hinge of the incomplete flap was vertically oriented in the mid-pupillary plane. I started the patient on a routine course of topical steroids and antibiotics and ordered a +4.0 D sphere, soft contact lens (Soflens 66 Toric, Bausch & Lomb) for him.

I carefully analyzed the instruments I had used and my surgical technique. After a discussion with my surgical staff, I identified the probable cause of the complication: The microkeratome's drive band might have disconnected from the suction ring as a result of the inadvertent incorporation of the surgical drape. Immediately, we replaced all the drive bands with newly modified “protected” ones, and we visually and aurally verified the proper connection between the microkeratome and drive band. We alerted the patient to these modifications and discussed his surgical and nonsurgical options.

Five months postoperatively, he underwent LASIK in his left eye by flap recutting. Again I used the SKBM microkeratome but incorporated the larger applanating H-head and new drive band design. I carefully placed the suction ring so that the new flap began temporal to the original. With the new H-head, I easily visualized a larger flap, as I had expected. The view through the applanation window further allowed me to place the hinge sufficiently nasally to allow laser ablation. After programming the appropriate microkeratome travel into the control unit, I was able to create an excellent-quality lamellar flap with a horizontal hinge.

The purpose of creating the new flap temporal to the original was to ease identification of the “true” flap if the patient needed an enhancement with relifting of the flap in the future. After creating the new flap, I completed the excimer laser treatment for hyperopia in the standard fashion. The patient received routine postoperative instructions and medications.

OUTCOME
On postoperative day 1, the UCVA of the patient's left eye was 20/60, which improved to 20/30 with -1.5 sphere. The slit lamp examination showed a secure LASIK flap without folds or striae. The interface was clear, and the new hinge was located near the nasal limbus. Careful examination revealed edema of the incomplete flap and the underlying, newly created complete flap. I increased the patient's topical steroids to once every 2 hours and carefully monitored him.

One week postoperatively, the patient had a UCVA of 20/30 with minimal flap edema. I tapered his topical steroids. By 1 month postoperatively, the patient's UCVA was 20/20, and it has remained stable through his 1-year examination. His manifest refraction is -0.5 -0.25 X 130 OS, and Orbscan topography shows central elevation consistent with hyperopic corneal surgery (Figure 4).

Although rare, incomplete LASIK flaps can happen to any surgeon. For that reason, the entire operative staff must diligently watch for the conditions that can lead to this complication. When incomplete flaps occur, it is appropriate to advise patients of their options, including RK, corneal intrastromal ring segments, refractive lensectomy with IOL placement, phakic IOLs, CK, and LTK. The patient may prefer to remain in spectacles or to be fit with newer contact lens designs.

When considering LASIK with recutting of the incomplete flap, it is imperative to completely understand and address the cause of the original complication. Although there are several approaches to these cases, I have found simply recutting at 3 to 6 months postoperatively to be rewarding for both the patient and surgeon.

Shachar Tauber, MD, is Assistant Professor and Director of Cornea, External Disease, Contact Lens, and Refractive Surgery for the Department of Ophthalmology and Visual Sciences, Yale University School of Medicine. He is also Medical Director of the Yale New Haven Eye Laser Center. Dr. Tauber is a member of the Alcon Refractive Speakers Bureau. He may be reached at (203) 752-2020; shachar.tauber@yale.edu.

1. Farah SG, Azar DT, Gurdal C, et al. Laser in situ keratomileusis: Literature review of a developing technique. J Cataract Refract Surg. 1998;24:989-1006.
2. Gimbel HV, Penno EEA, van Westenbrugge JA, et al. Incidence and management of intraoperative and early postoperative complication of 1000 laser in situ keratomileusis cases. Ophthalmology. 1998;105:1839-1847.
3. Stulting RD, Carr JD, Thompson KP, et al. Complications of laser in situ keratomileusis for correction of myopia. Ophthalmology. 1999;106:13-20.
4. Lin RT, Maloney RK. Flap complications associated with lamellar refractive surgery. Am J Ophthalmology. 1999;127:129-136.
5. Tham VMB, Maloney RK. Microkeratome complications in laser in situ keratomileusis. Ophthalmology. 2000;107:920-924.
6. Yildirim R, Devranoglu K, Ozdamar A, et al. Flap complications in our learning curve of laser in situ keratomileusis using the Hansatome microkeratome. Eur J Ophthalmology. 2001;11:328-332.
7. Jacobs JM, Taravella MJ. Incidence of intraoperative flap complications of laser in situ keratomileusis. J Cataract Refract Surg. 2002;28:23-28.
8. Holland SP, Srivannaboon S, Reinstein DZ. Avoiding serious corneal complications of laser assisted in situ keratomileusis and photorefractive keratectomy. Ophthalmology. 2000;107:640-652.
9. Kohnen T, ed. Refractive Surgery Problem Consultation Section. J Cataract Refract Surg. 2000;26:166-172.
10. Stulting RD, Carr JD, Thompson KP, et al. Complications of laser in situ keratomileusis for correction of myopia. Ophthalmology. 1999;106:13-20.
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