Contact sports such as boxing and wrestling can potentially cause serious eye injury, with or without prior eye surgery such as ICL surgery.
In one study (https://www.ncbi.nlm.nih.gov/pubmed/3627707), at least one eye injury was found in 66% of a group of boxers applying for a new or renewal license. Almost a quarter had retinal tears, and almost a fifth had pathologic cataracts.
In terms of eye health, therefore, contact sports are not a good idea in general, unless eye protection is worn.
If we talk about the post-ICL situation, the person can still get any of the above mentioned injuries, plus a few others.
For example, anterior subluxation of the haptics (footplates) of the ICL has been described after blunt eye injury from a fist. (Schmitz JW, McEwan GC, Hofmeister EM. Delayed presentation of traumatic dislocation of a visian implantable collamer lens. J Refract Surg. 2012;28(5):365–7)
Theoretically, it is also possible for an ICL to move or rotate after a hard blunt impact, which may affect the intended astigmatism correction.
If the ICL or part of it slips forward and touches the cornea, some amount of permanent corneal damage may potentially occur. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4066362/)
To put things in perspective, the above ICL related problems have only rarely been reported.
But in general, it is far better to engage in other types of sports, or to make sure one wears eye protection whenever engaging in risky contact sports.
