The complications associated with LASIK are primarily related to flap creation, postoperative flap positioning, or interface problems.
In the past, the more severe complications associated with LASIK were related to problems with the manual microkeratome, which caused the planned LASIK procedure to be abandoned in an estimated 0.6%–1.6% of cases. In current practice, advances in microkeratome technology and the advent of femtosecond laser–created flaps have substantially reduced the incidence of severe, sight-threatening complications.
When a manual microkeratome is used, meticulous care must be taken in the cleaning and assembly of the instrument to ensure a smooth, uninterrupted keratectomy. Defects in the blade, poor suction, or uneven progression of the microkeratome across the cornea can produce an irregular, thin, or buttonhole flap (Fig 6-9), which can result in irregular astigmatism with loss of BCVA. Steep corneal curvature can result in a nonuniform fit of the keratome suction device, exposing additional corneal surface area to the cutting blade, leading to the risk of thin, irregular, or buttonhole flaps. If a thin or buttonhole flap is created, or if an incomplete flap does not provide a sufficiently large corneal stromal surface to perform the laser ablation, the flap should ideally not be lifted. If it was, it should be replaced and the ablation should not be done. Substantial vision loss can be prevented if, under such circumstances, the ablation is not performed and the flap is allowed to heal before another refractive procedure is attempted, typically 3–6 months later. In such cases, a bandage contact lens is applied to stabilize the flap, typically for several days to a week. Although a new flap can usually be cut safely using a deeper cut after at least 3 months of healing, most surgeons prefer to use a surface ablation technique.
Figure 6-9 LASIK flap with buttonhole.
(Reproduced with permission from Feder RS, Rapuano CJ. The LASIK Handbook: A Case-Based Approach. Philadelphia: Lippincott Williams & Wilkins; 2007:95, fig 5.1. Image courtesy of Christopher J. Rapuano, MD.)
Occasionally, a free cap is created instead of a hinged flap (Fig 6-10). In these cases, if the stromal bed is large enough to accommodate the laser treatment, the corneal cap is placed in a moist chamber while the ablation is performed. It is important to replace the cap with the epithelial side up and to position it properly on a dried stromal bed, using previously placed radial marks, a prudent step before microkeratome cases. A temporary 10-0 nylon suture can be placed to create an artificial hinge, but the physiologic dehydration of the stroma by the endothelial pump will generally keep the cap secured in proper position. A bandage contact lens can help protect the cap. A flat corneal curvature (<40.00 D) is a risk factor for creating a free cap because the flap diameter is often smaller than average in flat corneas.
Corneal perforation is a rare but devastating intraoperative complication that can occur if the microkeratome is not properly assembled or if the depth plate in an older-model microkeratome is not properly placed. It is imperative for the surgeon to double-check that the microkeratome has been properly assembled before beginning the procedure. Modern microkeratomes are constructed with a prefixed depth plate, which eliminates this source of error. Corneal perforation can also occur when LASIK is performed on an excessively thin cornea. Corneal thickness must be measured with pachymetry prior to the LASIK procedure, especially in patients who are undergoing re-treatment.
Figure 6-10 A free cap resulting from transection of the hinge. The cap is being lifted from the microkeratome with forceps (arrow), and care is being taken to maintain the orientation of the epithelial external layer to prevent accidental inversion of the cap when it is replaced.
(Courtesy of Roger F. Steinert, MD.)
Jacobs JM, Taravella MJ. Incidence of intraoperative flap complications in laser in situ keratomileusis. J Cataract Refract Surg. 2002;28(1):23–28.
Lee JK, Nkyekyer EW, Chuck RS. Microkeratome complications. Curr Opin Ophthalmol. 2009; 20(4):260–263.
Nakano K, Nakano E, Oliveira M, Portellinha W, Alvarenga L. Intraoperative microkeratome complications in 47,094 laser in situ keratomileusis surgeries. J Refract Surg. 2004;20 (Suppl 5):S723–726.
Excerpted from BCSC 2020-2021 series: Section 13 - Refractive Surgery. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.