Combined temporary keratoprosthesis (TKP), pars plana vitrectomy (PPV), and penetrating keratoplasty (PKP) enable the corneal surgeon to rehabilitate or preserve eyes that have severe ocular pathology, such as retinal detachment. TKP, a temporary plastic device fixated to the eye to allow retina surgeons to perform surgery on an eye that also requires a corneal transplant, facilitates PPV.
Specifically, it enables the retina surgeon to see the posterior segment despite the presence of a corneal opacity (which can occur from an eye infection or trauma). This is significant because corneal opacities can otherwise delay time-sensitive PPV.1
Here are several tips for preoperative and intraoperative steps for TKP/PKP in the setting of a PPV.
1. Provide Patient Education
So that there are no post-surgical surprises for the patient, the cornea surgeon should make the patient aware of the risks of TKP and PKP. These include graft rejection in the future, lifelong use of steroid eye drops to prevent graft failure, the need for eye protection in this full-thickness transplant, suprachoroidal hemorrhage, IOP increase, and glaucoma.
Additionally, the cornea surgeon should educate patients that a history of ocular inflammation or herpetic disease places patients at high risk for PKP graft replacement, despite the successful outcome of the PPV. Specifically, the success rate for maintaining a graft ranges from 27.3% to 79% in various studies.1-3
Something else the cornea surgeon should inform patients about: Visual prognosis is difficult to assess. To highlight this to patients, I use a recent case study that revealed postoperative vision ranged from 20/30 to no light perception.
Additionally, the study showed that eyes that had chronic hypotony, active microbial keratitis, epithelial downgrowth, and exposure to silicone oil were more likely to have postoperative graft failure.
Further, postoperative repeat retinal detachments were more common in eyes that had a history of trauma and, thus, developed proliferative vitreoretinopathy.
2. Coordinate Co-Management
Decisions need to be made about preoperative and postoperative medication. Specifically, one surgeon picks the preoperative and postoperative medications, including antibiotic and steroid.
Communication about surgical technique is critical, especially the order of each procedure and location of incisions. For example, in our practice, we document ahead of time who will start the case and draw where we would like the retina surgeon to avoid placing their trocar and infusion.
The postoperative appointment should be set up in a way that allows both surgeons to examine the patient without a burden on the patient.
As an example, alternating the location of postoperative appointments can be helpful.
Regarding billing/coding, co-surgeons should be documented in the operative report and billing forms and whether they work at the same practice or two different practices.
3. Perform the Surgery
Typically, the corneal surgeon employs general anesthesia. (In cases where a retrobulbar block is warranted, I often defer this to the retina surgeon.)
The TKP options:
- Landers Widefield Temporary Keratoprosthesis. This is comprised of polymethylmethacrylate (PMMA) and is available in two versions: one with a central trunk 1 mm in length and 6.2 mm, 7.2 mm, or 8.2 mm in diameter, and the other a trunkless version. This product has specific cleaning instructions that not all surgery centers can perform but it has flexibility in its uses.
- Eckardt Temporary Kerato-prosthesis. This has a “trunk” that fits into the open sky area and is made of silicone.
Silicone oil is often used in these eyes, so the corneal surgeon should be aware that extra sets of instruments may be needed. Silicone oil is difficult to wash off, so changing instruments throughout the procedure is more efficient. (See “Alternatives to TKP,” below.)
After the PPV, the corneal surgeon removes the TKP and performs PKP.
ALTERNATIVES TO TKP
New vitrectomy techniques may provide the ability to treat retina pathology without the need for direct visualization through the anterior segment. Specifically, a less-taught technique called endoscopy-guided vitrectomy can be performed without the need for replacing the cornea. The endoscope allows visualization of the retina without a clear cornea. This technique is also useful to visualize IOL haptics and the angle in cases of uveitis glaucoma hyphema syndrome.
Additionally, microscope improvement and add-ons, such as a chandelier, can illuminate through mild-to-moderate corneal opacities.
The Power of 3
Combined TKP/PPV/PKP is an excellent approach to treating retina pathology when the cornea is not optically clear. Careful counseling and communication between surgeons are essential for success. CP
- Bové Álvarez M, Arumí CG, Distéfano L, et al. Comparative study of penetrating keratoplasty and vitreoretinal surgery with Eckardt temporary keratoprosthesis in ocular trauma versus non-trauma patients. Graefes Arch Clin Exp Ophthalmol. 2019;257(11):2547-2558.
- Dong X, Wang W, Xie L, Chiu AM. Long-term outcome of combined penetrating keratoplasty and vitreoretinal surgery using temporary keratoprosthesis. Eye (Lond). 2006;20(1):59-63.
- Khouri AS, Vaccaro A, Zarbin MA, Chu DS. Clinical results with the use of a temporary keratoprosthesis in combined penetrating keratoplasty and vitreoretinal surgery. Eur J Ophthalmol. 2010;20(5):885-891.
- Lee DS, Heo JW, Choi HJ, Kim MK, Wee WR, Oh JY. Combined corneal allotransplantation and vitreoretinal surgery using an Eckardt temporary keratoprosthesis: analysis for factors determining corneal allograft survival. Clin Ophthalmol. 2014;8:449-454.
- Skevos C, Bigdon E, Steinhorst A, et al. A novel temporary keratoprosthesis technique for vitreoretinal surgery. Int Ophthalmol. 2021;14(11):1791-1795.