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Mushroom keratoplasty optimizes postoperative refraction, graft survival
The technique involves removing less recipient epithelium than penetrating keratoplasty, reducing the chances of graft rejection.
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Microkeratome-assisted mushroom keratoplasty involves less replacement of the corneal endothelium than standard penetrating keratoplasty, a surgeon told colleagues at the American Ophthalmological Society meeting in Colorado Springs, U.S.A.
The novel technique minimizes corneal astigmatism and optimizes postoperative refraction and graft survival, Massimo Busin, MD, told Ocular Surgery News in a subsequent interview.
“The idea of performing a shaped keratoplasty is not new,” Busin said. “Lately, there has been substantial advancement in technique. The development of lasers has allowed us to revive shaped keratoplasty. Unfortunately, the femtosecond laser is not suitable because you often have to cut through vascularized corneas, and when you cut with a femtosecond, if you cut through a vessel, blood goes all over and it doesn’t work.”
In addition, microkeratome-assisted two-piece mushroom keratoplasty can also be used for low-risk patients with a healthy endothelium, Busin said.
Mushroom keratoplasty technique
The two-piece mushroom keratoplasty technique involves splitting the donor cornea into two halves, combining a large anterior lamellar keratoplasty with a small posterior lamellar keratoplasty.
“The advantage of this shape is that you have a large anterior surface of the graft, which serves the purpose of optimizing postoperative refraction and minimizing astigmatism while you minimize removal of the recipient endothelium, which is the layer that covers the internal side of the cornea,” Busin said.
The graft has a 9-mm anterior surface and a 6-mm posterior surface. This configuration reduces the risk of graft rejection, he said.
“The substantial advantage is that by reducing the amount of endothelium that you remove, on one hand you leave in place about 75% of the recipient endothelium, which in theory can repopulate the surface of the graft in case the donor endothelium is rejected and disappears,” Busin said. “But also, by transplanting only such a small amount of endothelium, the antigenic load of the new system is minimized, so it’s difficult for the immune system to recognize these endothelial antigens and develop an immunologic rejection.”
Postoperative astigmatism can be corrected with relaxing incisions, Busin said.
“It’s a self-sealing wound, so we can open it up all the way into the anterior chamber as opposed to straight wounds of conventional PK where you have to stop short before reaching the anterior chamber. Otherwise, you would have a leak. There is an overlap between recipient and donor, so you can enter all the way, 100%, and maximize the effect,” he said.
Study results
At the meeting, Busin reported results of a study that included 379 eyes of 375 patients. Mean follow-up was 3.1 years. Data were available for 310 patients at 12 months.
The mushroom technique was indicated for 93 high-risk eyes including those with herpes simplex keratitis or 2 or more clock hours of deep corneal neovascularization and 286 low-risk eyes with less than 2 clock hours of deep corneal neovascularization.
Mushroom keratoplasty was combined with extracapsular cataract extraction and IOL implantation in 11 eyes and with pupilloplasty in three eyes. It was combined with phacoemulsification and IOL implantation in 13 eyes and with scleral IOL fixation in one eye.
At 1 year, best corrected visual acuity was 20/20 or better in 7.4% of eyes and 20/40 or better in 71.8% of eyes. At 5 years, BCVA was 20/20 or better in 39.5% of eyes and 20/40 or better in 97.4% of eyes. At 9 years, BCVA was 20/20 or better in 57.1% of eyes and 20/40 or better in 100% of eyes.
“In terms of visual acuity, there is a progression in improvement over time,” Busin said.
Refractive astigmatism at 1 year was 4.5 D or less in 210 eyes, 4.5 D to 8 D in 39 eyes and 8 D or more in no eyes. Refractive astigmatism at 6 years was 4.5 D or less in 77 eyes, 4.5 D to 8 D in four eyes and 8 D or more in no eyes.
In those with herpes simplex keratitis, 5-year graft survival rates were 93.9% among patients who underwent mushroom keratoplasty and 78.8% among patients who underwent PK.
Overall graft survival rates with mushroom keratoplasty were 98.3% at 1 year, 97.5% at 2 years and 95.3% at 5 years, Busin said. – by Matt Hasson
- Reference:
- Busin M. Long-term results of two-piece microkeratome-assisted mushroom keratoplasty. Presented at: American Ophthalmological Society meeting; May 19-22, 2016; Colorado Springs, Colo.
- For more information:
- Massimo Busin, MD, can be reached at Villa Igea Hospital, Via le Gramsci 42, 47122 Forlì, Italy; email: mbusin@yahoo.com.
Disclosure: Busin reports he has received royalties and travel reimbursement from Moria.