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Inside Eyetube.net | Jun 2012

Enhancement After PRK

In this case presentation, the patient preferred a procedure with fast visual rehabilitation and less postoperative pain.

Perhaps the most common complication following refractive surgery is failure to achieve the planned refraction. Photorefractive (excimer laser) procedures tend to produce more accurate postoperative refractions than lens-based refractive procedures, especially in patients with low ametropia, but outcomes are not always perfect, and patients sometimes need retreatment. An undesired postoperative refraction may be the result of human error, such as wrong data entry or poor preoperative refraction; mechanical error, such as poor laser calibration (eg, homogeneity and fluence testing), eye-tracker malfunction, or inappropriate room settings; or conditions related to the individual patient, such as wound-healing response.

Most cases have no residual refractive error, or the error is minimal and does not affect the overall outcome; however, we have all had the misfortune of counseling dissatisfied patients with poor outcomes after refractive surgery. Additionally, it is not uncommon for patients to return years after the original procedure, complaining of reduced visual acuity and general discontent. Regardless of when visual complaints arise, a good surgical enhancement strategy can make these seemingly impossible cases more bearable. Below I review a recent case that required enhancement after PRK and outline the surgical steps I took to resolve the patient’s complaints.

A 38-year-old woman came to our center complaining of reduced visual acuity following previous PRK surgery done 5 yeas ago. Clinical examination of the patient revealed the following: UCVA of 0.5 OD and 0.7 OS and BCVA of 1.2 OU using -0.50 -1.00 X 180º OD and 0.00 -1.00 X 180º OS. Corneal topography revealed an oblate cornea (K1= 41.26 D; K2=42.28 D), and pachymetry showed central corneal thicknesses of 514 μm OD and 520 μm OS (K1= 40.26 D; K2=41.42 D).

SURGICAL OPTIONS

The patient was counseled, and several corrective surgical procedures were explained, including their potential complications:

Option No. 1: A second PRK session to enhance the first procedure. This option carried risks of postoperative regression, corneal haze, and corneal ectasia. The patient was also told that she would likely experience pain until complete reepithelialization occurred postoperatively. This was a point of concern for the patient after experiencing it with the first PRK procedure.

Option No. 2: Thin-flap LASIK enhancement. The main risk associated with this surgical option is postoperative corneal ectasia.

Option No. 3: Thin-flap LASIK Xtra enhancement. Like standard LASIK, visual recovery is faster with LASIK Xtra than with surface ablation procedures. In addition to the laser ablation, LASIK Xtra includes a concomitant accelerated corneal crosslinking (CXL) treatment to lessen the reduction of biomechanical corneal strength from the LASIK procedure and guard against the development of postoperative corneal ectasia.

Option No. 4: Phakic IOL implantation. This option must be considered only for sensible residual visual defects (extremely rare).

PATIENT PREFERENCE

The patient preferred a procedure with fast visual rehabilitation and less postoperative pain, and she therefore chose option No. 3. She also liked that this procedure enhanced corneal strength. Bilateral LASIK Xtra enhancement was carried out under topical anesthesia. Nasally hinged flaps were created using the Lasitome microkeratome (Gebauer Medizintechnik GmbH) with a planned thickness of 90 μm and an overall diameter of 9 mm. After lifting the flaps, an excimer laser ablation was carried out using the Technolas Excimer Workstation 217 (Bausch + Lomb), and remaining debris was washed from the ablation bed using balanced saline solution. The cornea was then soaked with VibeX (0.1% riboflavin in 20% dextran; Avedro, Inc.) for 1 minute, the bed was rinsed with balanced saline solution, and the flaps were repositioned.

Next, 75 seconds of ultraviolet-A irradiation (30 mW/cm2) commenced using the KXL System (Avedro, Inc.). The patient was examined shortly afterward at the slit lamp to ensure optimal flap shape and position (Figure 1). The patient had a stable UCVA of 0.9 OU shortly after the procedure, and we have followed her for 6 months. She continues to be satisfied with the improvement in her UCVA, and she was particularly satisfied that the immediate postoperative period was pain-free and that visual improvements were noticeable within a few hours after surgery.

Roberto Pinelli, MD, is the Scientific Director of Istituto Laser Microchirurgia Oculare, Brescia, Italy. Dr. Pinelli states that he is a member of the medical advisory board of Avedro, Inc., and previously sold a patent to the company. He is a member of the CRST Europe Editorial Board and may be reached at tel: +39 030 24 28 343; e-mail: pinelli@ilmo.it.

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