Most SMILE complications are mild and diminish in frequency with experience
SMILE has a rate of complications similar to that of LASIK, and when complications occur they are generally resolved with a good visual outcome for the patient, Catherine Albou-Ganem MD, Paris, France, told the XXXV Congress of the ESCRS in Lisbon, Portugal.
“Most of SMILE’s complications are related to experience and are included in the technique’s learning curve,” Dr Albou-Ganem reported.
She noted that an American Academy of Ophthalmology report in 2013 showed that the overall frequency of hazards and complications for SMILE was 8.6%, which is comparable to what is expected after LASIK.
Some complications that occur in SMILE procedures are the same as those that occur in LASIK, such as decentration and epithelial defects. She noted that epithelial defects occur in around 40% of patients. However, it is generally a mild problem that resolves in one or two days with the use of artificial tears. It has no effect on visual acuity and is present only in the area around the incision.
Dr Albou-Ganem pointed out that dryness of the corneal surface is less frequent, less intense and it does not last as long after SMILE as it does after LASIK. Diffuse lamellar keratitis is also less frequent and there can be a hazy interface. There can also be epithelial in-growth, but more generally it is a case of epithelial “seeds” that are easily rinsed away. Infection can also occur.
An intraoperative complication that is very specific to SMILE is suction loss. It generally results from excessive ocular movement by the patient immediately after docking the laser interface. The complication has been reported in 0.8-to-4.4% of SMILE-treated eyes.
“The incidence of suction loss decreases with experience but it cannot be eliminated completely,” Dr Albou-Ganem stressed.
Depending on when during the procedure suction loss occurs, the surgeon can either abort the procedure or re-dock the eye and continue. If suction loss occurs during the creation of the lenticules, the possible strategies include aborting the procedure, re-scheduling the procedure after the reabsorption of the cavitation bubbles, conversion to into thin-flap LASIK, or immediate re-docking and resumption of the procedure.
If suction loss occurs after the sculpting of the lenticules and during the creation of the incision, the best option is to restart the incision with a decreased distance from the centre and an increased side-cut depth.
Intraoperative black spots are
reported in 11-to-14% of cases
Black spots are reported in 11-to-14% of cases. They result from the presence of water droplets, debris or air between the laser and the coupling device and the ocular surface. They leave an area of untreated lenticule interface, making dissection more difficult.
Opaque bubbles lead to the same consequence. They are more common in eyes with a thicker cornea and a thinner lenticule, but they do not affect the overall clinical outcome, she said.
Lenticule ruptures often occur during the learning curve after difficult lenticule dissection. They can lead to remnant lenticule fragments between the stromal interfaces.
Incision ruptures during the enlargement of the small incision also occur more frequently during the learning curve. However, the problem can be overcome by very careful removal of the lenticule through the ruptured incision and adding a bandage contact lens.
The primary options for eyes that need retreatment for refractive enhancement include the circle, the side-cut and PRK, as recommended by Zeiss. Other options, suggested independently, include LASIK and subcap lenticule extraction.
The circle option converts the cap into a large diameter flap with the femtosecond laser, followed by lifting of the flaps and the performance of a refractive ablation on the exposed stroma. The circle option is indicated for corneas where lenticule creation leaves a thin anterior wall and thick posterior walls.
The side-cut option is indicated for eyes with thin residual posterior stroma, but it can only correct small refractive errors with a small optical zone. PRK is indicated in eyes with thin residual posterior walls where the final pachymetry will be over 350µm.
Catherine Albou-Ganem: firstname.lastname@example.org