Proper processing of materials can result in low infection, rejection risks.
This article was reviewed by Fengju Zhang, MD
The use of lenticular tissue acquired during the SMILE procedure seems to be the same with a minimal risk of infection, and the risk of rejection can be reduced by using an appropriate preservation method.
Myopia has an extremely high incidence in China, and as a result, numerous patients undergo the SMILE procedure, according to Fengju Zhang, MD.
“Because of this, we have accumulated many transparent lenticules after the surgeries and they are being reused in a number of corneal procedures, such as patching corneal perforations and correcting hyperopia, keratoconus, and ectasia after LASIK,” said Dr. Zhang, from the Beijing Tongren Eye Center, Beijing Tongren Hospital, and the Beijing Ophthalmology and Visual Sciences Key Lab, Capital Medical University, Beijing City, China.
However, the recycling of this tissue does not come without inherent risks. Possible infections that can take hold include herpes simplex virus (HSV), which can be latent in corneal stromal tissue for an extended period as well as bacteria, fungi, and Acanthamoeba that may be lurking in the normal conjunctival sac, she explained.
Another potential problem is immunologic rejection following implantation of the lenticules.
One Chinese study reported that at the one-year follow-up of 29 cases (53 eyes) that underwent allogeneic corneal stromal lenticule implantation to treat hyperopia, rejection of the tissue occurred in three eyes (5.66%) of two patients, Dr. Zhang noted.
In light of these complications, Dr. Zhang and colleagues undertook a study to detect pathogens and antigens in the fresh lenticules obtained during the SMILE procedure.
A total of 167 patients who underwent the SMILE procedure from October 2018 to April 2019 were chosen randomly. Those included had no systemic diseases, no history of use of systemic hormones or immunosuppressive drugs, no ocular diseases except for a refractive error, no history of ocular surgery or trauma. Patients had a stable refractive with no change exceeding 0.5 D annually for two years.
Patients also could not have used soft spherical contact lenses within one week, toric soft contacts and hard contacts within two weeks, or orthokeratology lenses within three months before surgery.
Any eyes with or suspected of having corneal ectasia, moderate to severe dry eye, severe meibomian gland disease, or an allergy induced by contact lenses were excluded. SMILE lenticules were collected in 128 eyes of 64 patients with myopia.
The donor specimens from each patient were divided into two groups in order to detect pathogens: specimens from 64 eyes (32 left and right eyes) and specimens from 64 eyes (32 left and 32 right); in the latter group, each specimen was divided into three pieces.