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Boston K-Pro retention in Stevens-Johnson syndrome can be improved
Surgeons explain how they perform conjunctival rearrangement procedures to cover the donor cornea with either bulbar or tarsal conjunctiva.
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Prosthetic devices have been used in most medical specialties to largely improve the functionality of the target tissue or organ and thus augment and/or prolong the quality of life of the recipient. However, when foreign material comes into contact with and is housed in a bed of human tissue, the integration process and biocompatibility are often challenging and can potentially result in tissue melt, inflammation, infection, tissue retraction, and extrusion or dislocation of the prosthetic device. Hence, improved surgical techniques combined with anti-inflammatory and anti-infective coverage often result in a beneficial effect in increasing the retention longevity of the implanted prosthetic device.
The use of an artificial cornea was initially conceptualized more than 200 years ago. In 1789, Pellier de Quengsy first described a keratoprosthesis, and in 1855, Nussbaum used a quartz crystal implant in the first reported human keratoprosthesis surgery. Continued research in the use of various synthetic corneas has resulted in three surgeon-preferred approaches: Boston K-Pro, AlphaCor and osteo-odonto keratoprosthesis. The Boston K-Pro, developed by Dohlman and approved by the U.S. Food and Drug Administration in 1992, has become the most popular option among corneal surgeons. However, there can be potential complications, especially when the surgeon is dealing with ocular diseases such as Stevens-Johnson syndrome.
Thomas "TJ" John
In this column, Drs. Alexander, Rootman and Aldave describe their proactive surgical techniques to prolong the ocular retention of Boston K-Pro in patients with Stevens-Johnson syndrome.
Thomas “TJ” John, MD
OSN Surgical Maneuvers Editor
Anthony J. Aldave
The most common indication for the Boston type 1 keratoprosthesis (Boston K-Pro) in most published series is repeat corneal transplant failure. Although the Boston K-Pro has been used for a wide variety of indications, some, such as Stevens-Johnson syndrome, are associated with less favorable outcomes, limiting the number of procedures performed. Complications after Boston K-Pro implantation in patients with cicatrizing conjunctivitis usually result from donor corneal stromal necrosis. Thus, we have modified our surgical technique when performing the Boston K-Pro in patients with cicatrizing conjunctivitis to cover the donor cornea at the time of surgery as opposed to doing so after a persistent epithelial defect and secondary stromal necrosis have developed. This has resulted in improved retention of the Boston K-Pro and prolongation of improved vision. At present, the Boston K-Pro is retained in 70% of the eyes of patients with Stevens-Johnson syndrome, with corrected distance visual acuity better than 20/200 in 86% of eyes at an average follow-up of 17.3 months (range: 7.1 to 59.5 months). We attribute much of this success to the proactive performance of tarsorrhaphies and conjunctival rearrangement procedures at the time of Boston K-Pro implantation or early in the postoperative period.
Figure 1. Extensive medial and lateral tarsorrhaphies in a patient following Boston type 1 keratoprosthesis implantation for ocular complications from Stevens-Johnson syndrome.
Source: Image: Aldave AJ, Alexander JK, Rootman DB
We have adopted a strategy of performing near complete medial and lateral posterior lamella-sparing tarsorrhaphies at the time of Boston K-Pro surgery (Figure 1). With such extensive closure of the eyelids, resulting in only the optic of the Boston K-Pro being visible, bandage contact lenses are not used because the lens would not be able to be replaced. Despite this aggressive management, a significant percentage of these eyes may develop a persistent corneal epithelial defect with or without secondary sterile corneal stromal necrosis. In such situations, we have adopted a proactive, rather than reactive, surgical approach and now prefer to perform conjunctival rearrangement procedures to cover the donor cornea with either bulbar or tarsal conjunctiva. Mobilization of the conjunctiva can be a great challenge in patients with extensive conjunctival cicatrization, particularly in eyes with previous retina and glaucoma procedures, which is the case for many eyes undergoing Boston K-Pro implantation. However, our experience with free-grafting of nasal and buccal mucosal membranes and dermis in such eyes has not been encouraging, with most grafts retracting or becoming necrotic within several weeks. Thus, we are now exclusively utilizing vascularized flaps to cover the donor cornea and have found the use of forniceal tissue on either a pedicle or bucket handle flap to be reasonably effective for coverage of quadrantic and hemispheric corneal epithelial defects, respectively. Such flaps can be combined and modified for coverage of more extensive or multifocal epithelial defects as well.
Surgical technique
Figure 2. Linear bucket handle flap incisions (a). Interpolated flap covering epithelial defect with cardinal sutures (b). Reconstruction of secondary defect with buccal mucous membrane graft (c). Reproduced with permission from Wolters Kluwer Health.
Figure 3. Pedicle flap incisions (a). Interpolated flap covering epithelial defect with cardinal sutures (b). Reconstruction of secondary defect with buccal mucous membrane graft (c). Reproduced with permission from Wolters Kluwer Health.
A fornix-based bucket handle flap can be created by first making a conjunctival incision along the superior or inferior border of the tarsus of the lower or upper eyelid, respectively. A second parallel incision is made at the reflection point of the bulbar conjunctiva (Figure 2a). The lateral and medial pedicles are maintained as wide as possible to improve blood supply to the flap. The flap is then undermined and mobilized to cover the corneal epithelial defect. An interpolation flap can be fashioned if desired, in which the pedicles lie over a bridge of intact conjunctiva, as this may allow for future mobilization. A more stable and permanent configuration involves making an incision in the conjunctiva along the pathway of the pedicles and then insetting the flap. Any remaining corneal epithelium is then debrided from the area that will be covered by the conjunctival flap, which is secured at the corneal limbus adjacent to the Boston K-Pro optic using a dissolvable suture on a spatulated needle (Figure 2b). Overcorrecting the flap to partially cover the optic is acceptable because the flap will retract slightly early in the postoperative period. Finally, the secondary forniceal defect is reconstructed with a free mucous membrane graft (Figure 2c).
A quadrantic flap can be performed in much the same way. The parallel linear incisions along the tarsus and at the forniceal reflection are fashioned to a length appropriate for mobilization to the corneal epithelial defect (Figure 3a). The two incisions are joined at one end, creating a pedicle flap of appropriate length. The flap can then be undermined, mobilized and rotated into place over the defect (Figure 3b) and secured in place with interrupted sutures. Again, the forniceal defect is reconstructed with free grafted mucous membrane (Figure 3c).
In either case, medial and lateral tarsorrhaphies are placed at the end of the case, leaving a 5-mm viewing window centrally. These can be taken down successively, if desired, as the ocular surface stabilizes.
References:
Aldave AJ, et al. Ophthalmology. 2012;doi:10.1016/j.ophtha.2012.02.015.
Alexander JK. Outcomes of the Boston type 1 keratoprosthesis in Stevens-Johnson syndrome. Paper presented at: American Society of Cataract and Refractive Surgery meeting; April 28, 2014; Boston.
Bradley JC, et al. Cornea. 2009;doi:10.1097/ICO.0b013e31818b8bfa.
Chew HF, et al. Cornea. 2009;doi:10.1097/ICO.0b013e3181a186dc.
Dohlman CH, et al. Adv Exp Med Biol. 1998;438:1021-1025.
Sayegh LP, et al. Am J Ophthalmol. 2008;doi:10.1016/j.ajo.2007.11.002.
Yaghouti F, et al. Cornea. 2001;20(1):19-23.
Zerbe BL, et al. Ophthalmology. 2006;doi:10.1016/j.ophtha.2006.05.015.
For more information:
Anthony J. Aldave, MD, can be reached at Jules Stein Eye Institute, 100 Stein Plaza, UCLA, Los Angeles, CA 90095; 310-206-7202; email: aldave@jsei.ucla.edu.
Edited by Thomas “TJ” John, MD, a clinical associate professor at Loyola University at Chicago and in private practice in Oak Brook, Tinley Park and Oak Lawn, Ill. He can be reached at 708-429-2223; email: tjcornea@gmail.com.
Disclosure: Aldave and John have no relevant financial disclosures.