Contraindications for Laser Vision Correction

As with any surgical procedure, it is important to weigh the risks and benefits of laser vision correction to ensure risks do not outweigh the potential benefits. This article will highlight the basic differences between laser in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), and small incision lenticule extraction (SMILE) as well as the contraindications related to these common LVC procedures. Although most patients will be very satisfied with the results of their refractive surgery, it is important that physicians know to say “no” when encountering relevant contraindications.

LASIK is one of the most popular and commonly performed refractive surgery techniques due to its superlative safety and efficacy profile.¹ In 2020, despite a global coronavirus pandemic, approximately 718,000 LASIK procedures were performed in the United States.

LASIK involves three fundamental steps:

LASIK corneal flaps are created with a femtosecond laser and corneal stromal bed ablation is carried out with an excimer laser.²

LASIK is efficacious in the treatment of hyperopia, myopia, and astigmatism. It has become the cornerstone of LVC techniques for most patients due to its quick healing time. Studies have shown the mean epithelial healing time to be in the range of three to five days with a known and acceptable safety profile.³

PRK was developed in 1987 and is defined by a lack of a lamellar corneal flap. Instead, PRK involves removing the top layer of corneal epithelium.⁴ Once the epithelial layer of the cornea is removed, an excimer laser is used to pertubate the corneal stroma.

The main advantage of PRK lies in the lack of a lamellar corneal flap which is ideal for patients with thinner corneas. The thicker cornea left behind after PRK can be considered a safer alternative to LASIK due to the lower risk for postoperative complications such as ectasia, which is characterized by abnormal asymmetric steepening of the cornea.⁶ Contrastingly, since the corneal surface is debrided in PRK, patient recovery and healing time are longer.

SMILE is a relatively newer LVC technique and was approved by the United States Food and Drug Administration (FDA) to treat myopia in 2018. The main appeal of SMILE, as compared to other more established refractive surgical techniques, is a preferable safety profile with less postoperative incidence of dry eye and faster recovery times.⁸ Since SMILE was introduced globally, approximately 2 million procedures have been performed.

The SMILE procedure is performed using a femtosecond laser to create a lenticulate (disc-shaped piece of cornea), which is then extracted from the eye through a 2-5 mm corneal incision.⁸ Unlike LASIK, no corneal flap is required to perform this surgery. It also differs from PRK in that the anterior stromal layer is completely preserved. Although the SMILE technique affords better ocular biomechanical integrity, studies have shown that the postoperative risk of ectasia can vary.⁹

Contraindications for LVC with LASIK, PRK, and SMILE include medications, abnormal corneal anatomy, autoimmune conditions, and certain specific periods of corneal structure development (e.g., childhood, pregnancy, lactation periods).¹⁰ Physicians must inquire prior medical history to ensure informed decision-making with patients.

Isotretinoin, commonly known as Accutane, is a relative contraindication for LVC. Due to the high prevalence of acne vulgaris, isotretinoin is routinely prescribed.¹¹ Notwithstanding, the ocular ramifications of LVC on patients actively taking isotretinoin are often overlooked. Since the average age of a patient on isotretinoin is 24 years, it creates significant overlap with the major LVC demographic of 18-30 years.¹²

Specifically, dry eye disease is a major adverse effect of LVC and isotretinoin should not be started if a patient has undergone refractive surgery in the previous six months. Moreover, before performing LVC, ophthalmologists should screen patients for isotretinoin use.¹² Due to the serious nature of post-operative dry eye, both ophthalmologists and dermatologists should actively counsel patients on the effects of LVC on patients actively taking isotretinoin.

Amiodarone, an antiarrhythmic cardiac medication, is known to have an adverse effect profile which can cause optic neuropathy and cyanopsia (vision defect resulting in objects appearing to have a blue tint). Cases show patients on amiodarone can develop visual disturbances such as dysphotopsias (flashes and colored rings around lights) after refractive surgery.¹³ Discontinuation of Amiodarone, in consultation with the patient’s cardiologist, has led to substantial improvements in LVC outcomes.¹³

Patients with a history of rigid contact lenses are more likely to develop corneal topographical anatomical abnormalities. Before LVC is performed, a thorough examination of a patient's cornea is essential to assuring a safe procedure. Contraindicative corneal abnormalities include astigmatism, loss of radial symmetry, and the absence of normal progressive flattening from the center to the periphery of the cornea.¹⁴

Rigid contact lenses are a common possible source for these pathogenic corneal abnormalities. It is worth noting that these conditions can also be seen in people who regularly wear soft contact lenses. The topographic changes in the cornea after contact lens removal can affect postoperative wound healing in an unpredictable and irregular manner.¹⁵ If abnormalities are present and permanent, LVC should not be performed. Complications of progressive corneal thinning like keratoconus can result in severe vision loss.

Collagen vascular diseases(CVD) are a relative contraindication to refractive surgery due to the possible ocular manifestations of these diseases. CVD represents a group of autoimmune diseases, including rheumatoid arthritis (RA), Sjogren's Syndrome (SS), and seronegative spondyloarthropathies.¹⁶

Dry eye or keratoconjunctivitis sicca is the most common ocular manifestation of disease seen in patients with RA. Studies comparing the outcomes of LVC in patients with and without CVD demonstrate variable and inconclusive conclusions.^16,17

Long-term adverse effects of LVC should be extensively discussed between ophthalmologists and their patients with autoimmune conditions. Due to the fact that LASIK has a quicker wound healing time than PRK, it is the preferred form of refractive surgery in patients with autoimmune diseases.

Diabetes mellitus can present with a multitude of ocular manifestations including diabetic keratopathy, diabetic retinopathy, diabetic papillopathy, and refractive instability.¹⁶ In diabetes mellitus, defects in insulin sensitivity produce chronic hyperglycemia.¹⁸ Patients with uncontrolled diabetes mellitus undergoing LVC show high complication rates of 47% compared to only 6.9% in healthy controls.¹⁹ LVC should be avoided on patients with uncontrolled diabetes mellitus or diabetic ocular complications.¹⁶

LVC should be avoided during periods of ocular development and change such as pregnancy and lactation as hormonal changes can lead to changes in refraction.¹⁶ Sex hormone receptors can be found in the cornea, and during pregnancy and lactation the overproduction of estrogen can lead to corneal biomechanical instability.²¹ The evidence suggests that the risk of postoperative corneal ecstasia is significantly elevated during these time periods. Refractive surgeons recommend waiting until after a female's nursing period to perform potential LVC.

Although LVC continues to be a predominantly successful and safe intervention, the need to be cognizant of the relevant contraindications discussed above is paramount. Honest patient-physician rapport is key to effective informed decision making and knowing when to say no to LVC.