PURPOSE: To provide an overview of the currently available retreatment methods 
after myopic small-incision lenticule extraction (SMILE).
DESIGN: Systematic literature review.
METHODS: The PubMed library was searched for articles containing the terms 
"small-incision lenticule extraction" and "enhancement" or "retreatment". The 
last search was performed on May 1, 2019.
RESULTS: In contrast to laser in-situ keratomileusis (LASIK), which can be 
retreated by a flap relift, repeat SMILE retreatment is currently not approved 
and only seldomly performed. As substitutes, surface ablation, cap-to-flap 
conversion using the CIRCLE program in the VisuMax platform, and thin-flap LASIK 
have been recently established. While all options offer safety and efficacy 
comparable to LASIK retreatments, each has its patient-specific advantages and 
disadvantages. While surface ablation preserves the flap-free approach of the 
primary procedure, the aspect of pain and a slow visual recovery might render it 
less attractive as compared with CIRCLE and thin-flap LASIK which offer quick 
recovery, however at the price of flap creation. Besides, each retreatment 
method generates specific tissue responses and has a different impact on corneal 
biomechanics, which is strongly dependent on the previous SMILE parameters, 
especially the cap thickness.
CONCLUSIONS: Refractive enhancement after SMILE is currently mostly performed by 
surface ablation, CIRCLE cap-to-flap conversion or thin-flap LASIK, which all 
offer safety and efficacy comparable to LASIK retreatments. In this review, a 
detailed overview over each method, its technical aspects, and specific 
advantages and disadvantages is given.