A team led by Professor Li Ying from the Department of Ophthalmology, PUMCH led the world in using cornea materials from SMILE surgery on cornea transplantation. Since 2014 it has completed dozens of operations and provided a new solution to the severe shortage of cornea donations in China. The project has recently won the third prize of PUMCH 2017 Medical Achievements Award.

Rheumatism will erode collagen in the human system and cause pains. Corneal tissues, chiefly made of collagen type I, have a stronger sense of pain when damaged, as their nerve fibers conveying the sense of pain are ten times denser than in skin. In the case of Mooren's ulcer, the cornea will be gradually eaten up from the edge, causing perforation and threatening the eyeball. According to Jiang Yang from the Department of Ophthalmology, due to a lack of corneal materials, in Mooren's ulcer cases only thin amniotic membrane could be used to mend the wound, not only causing scars but also affecting the surgical results. Other corneal diseases, including keratoconus, leucoma and perforation, faced the same problem.

Every year, PUMCH performs numerous surgeries treating myopia, more than 70% of which are SMILE. Unlike LASIK, which corrects refractive errors through cutting and vaporizing the corneal stroma, in SMILE, the surgeon uses a femtosecond laser to create a small, lens-shaped bit of tissue (lenticule) within the cornea. Then, with the same laser, a small arc-shaped incision is made in the surface of the cornea, and the surgeon extracts the lenticule through this incision and discards it. The lenticule, which is an incomplete part of corneal tissue, is also called corneal stroma material. Professor Li’s team hit the idea that the numerous and fresh stroma material left from SMILE can be “recycled” for corneal transplantation. The team’s proposal to use this material in tectonic keratoplasty has been approved by the hospital’s Ethics Committee.

Tectonic keratoplasty (TK) is a procedure in which only the diseased part of cornea is replaced, so as to keep the eyeball and cornea complete. A corneal material with the same size and thickness of the diseased part will be planted in. The key points of TK is pre-procedure assessment of the scale and depth of the damage, and choose from single or multiple lenticule plans; in operation, the epithelium surrounding the diseased part and the diseased part in the bed will firstly be removed, and the optical zones will be avoided. After the operation hormone drugs shall be used, close follow-up carried out, and stitches can be removed usually after three months. Through this operation an old lady Liu was freed from a long-year eye trouble and managed to keep her 0.8 eyesight.

Compared with regular cornea trnasplantation, TK requires more from stitching due to the tiny size of lenticule, but produces better results. So far nearly a hundred operations have been performed, which totally kept the completeness of the planted part and the eyeball. Patients reported stable eyesight and no rejection. According to Associate Professor Liu Xiaowei from the Department of Ophthalmology, they have never seen any rejection in three years because TK will not touch the endothelium but will only “patch”small diseased parts, and the planted part will not exceed 6.5mm in diameter.

TK also features low expenses and low cost in cornea storing. According to Professor Li Ying, more than 200 hospitals across China are now able to perform SMILE, which can provide plenty of materials for TK if consent is abtained from healthy cornea providers. This technique is expected to open a new source of supply for cornea transplanation, shorten the waiting time and therefore benefit patients.

(By Wang Lu, Duan Wenli)