CASE PRESENTATION
A 54-year-old female wants to have corrective laser surgery for her high myopia and astigmatism. Her BCVA is 0.8 with sph -10 cyl -3.5 axis 5 at her right eye and 0.9 with sph -7.25 cyl -2.75 axis 5 at her left eye. Her preoperative data are as follows: right eye dominant; pupillometry in scotopic circumstances OD 6.67 mm, OS 6.50 mm; pachymetry (Haag-Streit interferometry; Haag-Streit AG, Koeniz, Switzerland) OD 521 µm, OS 524 µm; normal standard and elevation topography.

A LASIK procedure may still be considered since (1) a -1.50 D undercorrection to obtain monovision is targeted in the right eye and (2) the surgery will be performed using thin flaps (target 110 µm) and a Wavelight Allegretto (Wavelight Laser Technologie AG, Erlangen, Germany) excimer laser that allows for less tissue consumption than many other lasers.

The surgeon used a Moria M2 microkeratome (Antony, France) with a single-use 90 head at speed two. LASIK in the right eye was uneventful. Preoperative flap thickness measurement was 100 µm. In the left eye, the surgeon used the same microkeratome with a new head. Unfortunately, surgery was complicated by a small buttonhole slightly inferiorly and nasally to the pupil center. The flap was repositioned without treatment and a bandage contact lens was applied.

Three months after initial surgery, BCVA recovered to 1.00 D with sph -7 cyl -3 axis 180, and the buttonhole was no longer visible at the slit lamp. A retreatment is performed using a One Use-Plus (Moria) microkeratome with the disposable 130 head and a lateral translation with a nasal hinge. Unfortunately, the buttonhole reopens and, during the reverse movement of the microkeratome, a tissue sheet protrudes at the margin of the flap. This represents the stromal tissue between the two cuts.

Since the bed is perfect, the laser treatment is performed. When replacing the flap, the interface tissue is repositioned as well as possible, the buttonhole tissue being the only reference to guide the repositioning. The second flap is larger than the first; in manipulating the flap, the margin of the first reopens inferiorly. A bandage contact lens is applied.

Healing occurs uneventfully, leaving a small scar at the level of the buttonhole and an irregular astigmatism. Even though the BCVA is still 1.00 D with sph +0.5 cyl -2.75 axis 70 and UCVA 0.50 D, the patient complains of slightly double vision. The pachymetry is 411 µm. With the Pentacam Scheimpflug (Oculus Optikgerate GmbH, Wetzlar, Germany) camera, the thinnest part of the cornea is 359 µm. With Visante (Carl Zeiss Meditec AG, Jena, Germany), anterior segment optical coherence topography, the thinnest part of the cornea is 407 µm, and the residual stromal bed is estimated at 305 µm.

How would you retreat the left eye of that patient?

DAVID T.C. LIN, MD, FRCSC
This case illustrates the difficulty of managing a buttonhole following LASIK. Once a buttonhole occurs, the key is to reposition the flap and let it heal. The author did this during the initial management, which allows the cornea to heal back to its original refraction. Recutting the flap in the second treatment only works if the flap has time to completely heal—a factor that varies between patients. The difficulty results from the incomplete healing of the interface or slippage during the cut. Irregular astigmatism always occurs if the pieces of the flap are not put back exactly, especially if parts of the flap are in slivers. This is much akin to putting a jigsaw puzzle back without all the pieces correctly matching up. The irregular astigmatism is compounded if a laser treatment is done at this time (eg, resultant irregular topography.)

The safest way to manage buttonholes is to treat with surface PRK after healing. This is especially true in thin corneas. I try to wait at least 6 months, and preferably 1 year prior to retreatment. Patients often demand an earlier retreatment; however, proper counseling as to the merits of waiting (ie, less haze, better surface regularity from epithelial remodelling) usually allows for a better result. Transepithelial phototherapeutic keratechomy (PTK) is the method of choice for epithelial removal as it is least disruptive to the fragile buttonhole adhesions.

For regular topographies, a standard PRK is fine.

In regard to an irregular topography and a thin cornea, I would stick to the above principles and retreat with a topography-guided PRK after transepithelial PTK. An irregular cornea will most likely not be measurable with a wavefront device.

I have performed over 500 cases with the Allegretto topography-guided system. The topography-guided software flattens the steep areas and steepens the flat areas, as illustrated in the case below. Topography-guided software only treats the surface irregularity and does not treat the refractive component of eye. For this reason, we counsel patients that they may need an additional treatment after the initial smoothing to treat the residual refractive error. Algorithms are developed to incorporate the refractive induced effect from surface smoothing, in addition to the patient's refractive treatment to reduce the rate of a subsequent enhancement. This was presented at the 2006 American Society of Cataract and Refractive Surgery meeting.¹

In this case, after the initial plano topography-guided treatment following a PTK, I would treat the estimated induced refractive change from the topography-guided treatment at the same time, probably -1.00 D to -2.00 D. I would also use mitomycin C 0.02% for 20 seconds and flush copiously with balance salt saline for 2 minutes. I would allow the surface to heal and stabilize without haze, using steroids for 3 months. A repeat refraction would then be performed to determine a final PRK, if necessary. The final refractive PRK should be performed with a standard wavefront-optimized software, as the surface aberrations should be significantly reduced.

ALBERTO VILLARRUBIA, MD
Despite advances in cataract surgery, a subluxated lens remains one of the most challenging surgeries for an anterior segment surgeon. Before addressing surgical strategies, I would like to comment that every patient with a traumatic eye should be aware of the potential for a subluxated lens, since this pathology is not always immediately diagnosed. If a subluxated lens is discovered, it is important to quickly determine the opacification of the lens. I recommend surgery if a soft opacification is diagnosed, despite a good BSCVA.

Special care should be taken during the procedure because of the possibility of an augmentation of the zonulolisis. Additionally, peribulbar anesthesia could achieve an overpressure during the surgery, and preoperative compression of the globe must be avoided. Surgeries should be performed using only 2 mL of retrobulbar anesthesia.

After opening the conjuntiva, a scleral flap of 2 x 2 mm limbus based (2/3 in depth) is dissected in the middle of the subluxation. This is followed by the creation of a small paracentesis and a dispersive ophthalmic viscosurgical device (OVD) is injected under the endothelium. The next step is to create a 2.7-mm corneal incision in front of the subluxation in the same manner as a standard phacoemulsification. A minimal anterior vitrectomy should be done if the vitreous was previously seen in the anterior chamber through the zonular weakness; be aware that if a great anterior vitrectomy is performed, subluxation could enlarge due to the loss of the vitreous bed behind the lens. Cohesive OVD will then be injected between the lens, and the anterior dispersive OVD to facilitate maneuvers over the lens. After this, four limbal paracentesis are created at 90º, separately one from the other. Two of them are created 45º to the right and left of the center of the subluxation. A 5 x 5 mm capsulorrhexis (CCC) must be done with a special care. I always use CCC forceps because this maneuver is more controllable with the tool. Stay away from the equator of the subluxation, or you risk breaking the anterior rim of the CCC after the insertion of the iris hooks.

Once the CCC has been finished, four iris hooks are introduced through the previously opened limbal paracentesis. These hooks are carefully attached in the rim of the CCC to fixate/support the lens. After this, gentle hydrodissection is performed under the anterior CCC. I do not recommend doing only one injection of balanced salt solution, because this could result in an overpressure inside the capsular bag, followed by an increase of the zonular weakness. If the opacification of the lens is not hard, the hydrodissection should be enough to begin with the phacoemulsification in an almost aspiration approach. In these cases, my preferred aspiration setting is the slow-motion technique. Once the nucleus has been emulsificated and the capsular bag has been filled with cohesive OVD, a modified Cionni capsular tension ring (CTR) is introduced inside the bag throughout the main incision. The CTR has been previously prepared with a 10/0 prolene suture double armed with two needles (STC-6). This is not an easy step because minimal trauma in the capsular bag could end in a tear—forcing us to change the strategy. The sutures are passed throughout the main incision and over the rim of the CCC and, once out of the sclera, both needles are cut and sutures are knotted. This maneuver produces a confident fixation of the bag. The cortex is aspirated with tangential movements due to the difficulty of removing such a material beside and behind of the CTR. Iris hooks are removed, and the capsular bag is filled again with cohesive OVD. An acrylic lens with PMMA haptics (ie, MA60BM; Alcon Laboratories Inc, Forth Worth, Texas) is introduced with an injector and unfolded inside the bag. OVD is aspirated, scleral tape sutured with nylon 10/0 and the main corneal incision is hydrated or sutured with nylon 10/0 if needed.

JÉRÔME C. VRYGHEM, MD
When I was faced with this complication, I waited 6 months after the second buttonhole and the initial treatment, and I relifted the peripheral flap very carefully using the Moria Vryghem flap manipulator. At this point, I was able to retrieve the surface that had already been treated—without damaging the flap. A topography-guided treatment (Wavelight T-CAT software) was applied with a target of -1.25 D. The final result, 4 months after that last retreatment, was UCVA 0.6-, BCVA 0.8 with -1 cyl -1 axis 150. Central pachymetry was 376 µm. Topograhy is still irregular, but the patient is satisfied, even if she still perceives some double vision.

David T.C. Lin, MD, FRSCS, is the clinical assistant professor of ophthalmology at the University of British Columbia, a surgeon at Pacific Laser Eye Center, and a fellow of the Royal College of Physicians and Surgeons of Canada. Dr. Lin states that he is a paid employee of Wavelight. He may be reached at info@pacific-laser.com.

Albertio Villarrubia is a surgeon at Clinica La Arruzata, in Codoba, Spain. Dr. Villarubia did not provide any financial disclosure information. He may be reached at alvillarrubia@yahoo.com.

Jérôme C. Vryghem, MD, is from the Brussels Eye Doctors in Brussels, Belgium. Dr. Vryghem states that he has no financial interest in the products or companies mentioned. He may be reached at j.c.vryghem@vryghem.be or +32 2 741 69 99. Dr. Vryghem is a member of the Cataract & Refractive Surgery Today Europe Editorial Board.

1. David T.C. Lin, MD. FRCSC . Custom Topographic Neutralizing Technique for Optical Zone Enlargement after Lasik. Presented at the ASCRS meeting: March 17, 2006. San Francisco, CA.