Keratoprosthesis Implantation Research Articles

Boston type 1 keratoprosthesis for severe blinding vernal keratoconjunctivitis and Mooren’s ulcer

Indications for the Boston keratoprosthesis differ throughout the world depending on the prevailing regional causes of end-stage corneal disease. We report the short term anatomical and functional outcomes of the Boston type 1 keratoprosthesis for severe bilaterally blinding vernal keratoconjunctivitis and Mooren's ulcer. A retrospective chart review was conducted of 2 patients who underwent several unsuccessful ocular surface reconstruction procedures before Boston type 1 keratoprosthesis implantation. The anatomical and visual outcomes of the Boston type 1 keratoprosthesis at 1year of follow-up were assessed clinically and by anterior segment optical coherence tomography imaging. The keratoprosthesis was retained in both the eyes at 1year postoperatively with a best-corrected visual acuity of 20/30 in both patients. To our knowledge this is the first report of successful Boston keratoprosthesis implantation for these two unusual indications.

Longer-Term Vision Outcomes and Complications with the Boston Type 1 Keratoprosthesis at the University of California, Davis

To evaluate retention of visual acuity and development of complications after Boston type 1 keratoprosthesis implantation over a longer follow-up period than previously reported. Cohort study. Forty eyes of 35 patients who underwent Boston type 1 keratoprosthesis surgery at the University of California, Davis, between 2004 and 2010. Preoperative, intraoperative, and postoperative parameters were collected and analyzed. Best-corrected visual acuity (BCVA) and postoperative complications. Preoperative visual acuity ranged from 20/150 to light perception and was ≤20/400 in 38 eyes (95%). Preoperative diagnoses included failed corneal transplants (19 eyes, 47.5%), chemical injury (10 eyes, 25%), and aniridia (5 eyes, 12.5%). Mean follow-up duration was 33.6 months (range, 5-72 months). Of 36 eyes followed for ≥1 year, 32 eyes (89%) achieved postoperative BCVA ≥20/200. Of eyes that achieved BCVA ≥20/200, at last follow-up, 19 of 32 eyes (59%) followed for ≥1 year retained BCVA ≥20/200; 16 of 27 eyes (59%) followed for ≥2 years retained BCVA ≥20/200; 7 of 14 eyes (50%) followed for ≥3 years retained BCVA ≥20/200; and 2 of 7 eyes (29%) followed for ≥4 years retained BCVA ≥20/200. End-stage glaucoma most commonly caused vision loss (7 of 13 eyes, 54%) when BCVA ≥20/200 was not retained (follow-up ≥1 year). Glaucoma was newly diagnosed in 11 eyes (27.5%); progression was noted in 9 eyes (22.5%). Glaucoma drainage device erosion occurred in 9 eyes (22.5%). Retroprosthetic membrane formed in 22 eyes (55%), 5 eyes (12.5%) developed endophthalmitis, 6 eyes (15%) developed corneal melt, 7 eyes (17.5%) underwent keratoprosthesis replacement, and 23 eyes (57.5%) required major surgery to treat postoperative complications. The initial keratoprosthesis was retained in 32 eyes (80%). Keratoprosthesis implantation remains a viable option for salvaging vision. A significant number of patients lost vision over the postoperative course. Glaucoma and complications related to glaucoma surgery are significant challenges to maintaining good vision after keratoprosthesis surgery. Our study highlights the need for long-term follow-up and a team approach to management, and points to a more guarded long-term visual prognosis after surgery. The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Cost effectiveness of the type II Boston keratoprosthesis

Despite demonstrated cost effectiveness, not all corneal disorders are amenable to type I Boston keratoprosthesis (KPro) implantation. This includes patients with autoimmune diseases, such as Stevens-Johnson syndrome/toxic epidermal necrolysis. Type II KPro is implanted through the eyelids in severe dry eye and cicatricial diseases, and its cost effectiveness was sought. In a retrospective chart review, 29 patients who underwent type II KPro surgery at the Massachusetts Eye and Ear Infirmary between the years 2000 and 2009 were identified. A total of 11 patients had 5-year follow-up data. Average cost effectiveness was determined by cost-utility analysis, comparing type II KPro surgery with no further intervention. Using the current parameters, the cost utility of KPro from third-party insurer (Medicare) perspective was 63,196 $/quality-adjusted life year . Efforts to refer those less likely to benefit from traditional corneal transplantation or type I KPro, for type II KPro surgery, may decrease both patient and societal costs.

Special Considerations for Pars Plana Tube-Shunt Placement in Boston Type 1 Keratoprosthesis

The Boston type 1 keratoprosthesis has been successfully used in eyes with a poor prognosis for a conventional penetrating keratoplasty. The Boston Type 1 Keratoprosthesis Study Group reported significant postoperative vision improvement with a high rate of graft retention. However, glaucoma has significantly limited visual potential in patients with otherwise successful transplants. Given a crowded anterior chamber, scarring, and/or inability to visualize the anterior segment after the keratoprosthesis implantation, vitrectomy and pars plana tube placement is frequently necessary for intraocular pressure control. In addition, the need for optimal contact lens fitting after surgery necessitates a modified surgical technique for the combined procedure to avoid complications and to achieve optimal visual rehabilitation. We present our technique in a case series of combined vitrectomy and pars plana glaucoma shunt placement for the Boston type 1 keratoprosthesis.

Keratoprosthesis with retrocorneal fixation: preliminary results in dogs with corneal blindness

To evaluate the use and complications of a penetrating keratoprosthesis implantation in the management of corneal opacification in dogs. A retrospective clinical study describes the indications for the surgical technique utilized and the outcomes of this procedure in 20 eyes of 19 dogs with blindness of corneal origin. A successful surgical outcome was defined as a clear keratoprosthesis optic and improvement or restoration of functional vision over a follow-up period ranging from at least 8 months to a maximum of 7 years. Eyes with total corneal opacification resulting from chronic superficial keratitis (n = 11), keratoconjunctivitis sicca (n = 5), endothelial dystrophy (n = 3) and chemical burn (n = 1) were treated by unilateral (n = 18) or bilateral (n = 1) full-thickness implantation of a keratoprosthesis. Keratoprostheses were retained in 15 eyes (75%) which regained vision to the date of reporting. Among these eyes, six had uncomplicated postoperative course, five developed retroprosthetic membranes and four developed granulation tissue over the optic of the keratoprostheses. These complications were successfully removed surgically in the nine eyes. The five remaining eyes (25%) developed serious early postoperative complications, for which enucleation had to be performed. In keratopathies in which the corneal opacification could not be treated by standard medical or surgical procedures, this keratoprosthesis appears to be promising to restore vision in chronic superficial keratitis and deep corneal dystrophy. It appears to have a poor prognosis in keratoconjunctivitis sicca in brachycephalic dogs. The post operative complications retro-prosthetic membranes and granulomatous overgrowth could be treated well.

Moscow Eye Microsurgery Complex in Russia Keratoprosthesis in Beijing

To evaluate the efficacy and preliminary safety of the Moscow Eye Microsurgery Complex in Russia (MICOF) keratoprosthesis in eyes with complicated corneal opacities unsuitable for keratoplasty. Retrospective review of consecutive clinical case series. We analyzed 85 eyes of 85 patients who previously underwent MICOF keratoprosthesis implantation at the Chinese PLA General Hospital between April 1, 2000, and August 31, 2009. The mean follow-up after MICOF keratoprosthesis implantation (measured after the second stage of the implantation) was 34.7 months (range, 3-107 months). The MICOF keratoprosthesis surgery involves 2 procedures. In stage 1, a supporting titanium frame is inserted into the lamellar pocket; a polymethyl methacrylate (PMMA) optical cylinder is implanted 3 months later (stage 2). Data were collected from the preoperative, intraoperative, and postoperative courses. Statistical analysis was performed to identify factors influencing postoperative complications. Visual acuity (VA), keratoprosthesis retention, and significant postoperative complications. The MICOF keratoprosthesis dramatically improved vision in most patients. The percentage of eyes with postoperative VA of 20/100 or better was 80.7% (67/83) at 6 months after stage 2, 82.4% (61/74) at 1 year, 72.7% (40/55) at 2 years, 78.8% (26/33) at 3 years, 78.9% (15/19) at 4 years, 100% (8/8) at 5 years, 80% (4/5) at 6 years, 100% (2/2) at 7 and 8 years, and 100% (1/1) at 9 years. The most common complication, retroprosthetic membrane formation, occurred in 39 of 85 eyes. The overall keratoprosthesis retention rate was 81.2% at an average follow-up of 34.7 months (range, 3-107 months). Ten eyes presented with elevated intraocular pressure after implantation; 3 of these had underlying glaucoma. All 3 eyes received cyclocryotherapy to control intraocular pressure. Sterile vitreitis occurred in 2 eyes, and retinal detachment occurred in 1 eye. The MICOF keratoprosthesis is an effective alternative for patients with corneal blindness and a poor prognosis for penetrating keratoplasty.

Fyodorov–Zuev keratoprosthesis implantation: long-term results in patients with multiple failed corneal grafts

The long term results of the Fyodorov-Zuev keratoprosthesis are presented for ten patients with repeated graft failures. The study took place at Dr Khodadoust Eye Hospital. The Fyodorov-Zuev keratoprosthesis was implanted in ten patients with repeated graft failures, including seven patients with old trachoma, two patients with chemical injury, and a patient with thermal injury. The outcome measures were visual acuity, retention, and complications of the keratoprosthesis. Preoperative best-uncorrected visual acuity (BUVA) ranged from counting fingers to light perception (median: light perception). The keratoprosthesis dramatically improved vision in most patients. Patients retained BUVA of 20/200-20/50 in 50%, 20/60-20/100 in 30%, 20/200 in 10% and 20/400 in 10%. Overall, 90% had 1 year postoperative vision of 20/200 or better. 70% of cases had BUVA of 20/200 or better at the last follow-up (average 52 months). Of ten keratoprosthesis implanted, three have been removed, and as a result, retention rate was 70% during average follow-up of 52 months .The most common postoperative complications were retroprosthetic membrane formation (40%), uveitis (20%), glaucoma (20%), tissue overgrowth (20%), early leakage (20%), late leakage (20%), aseptic necrosis (20%), retinal detachment (10%), endophthalmitis (10%), and granulation tissue growth (10%). Fyodorov-Zuev keratoprosthesis is an effective means of managing repeated corneal graft failure.

Crescenteric Amniotic Membrane Grafting in Keratoprosthesis-Associated Corneal Melt

We herein present a surgical technique for the management of corneal melt following Boston type I keratoprosthesis implantation. The technique was performed using new-generation dehydrated human amniotic membrane. The membrane was fashioned in the shape of 2 crescentic patches using disposable corneal trephines. A double layer of grafts was then sutured into the host bed with interrupted 10-0 nylon sutures. Rapid healing with corneal epithelization and vascularization was noted within days. The main advantage of the amniotic membrane that we used is that it is thicker than the older generation (110 vs 40 microm) and suitable for tectonic purposes. It is also readily available with a long shelf life and does not require a lamellar dissection unlike a donor corneal patch. This surgical technique may potentially serve as another tool in a cornea surgeon's armamentarium.

Binocular visual function following boston type 1 keratoprostheses

Purpose: To report the postoperative binocular function of patients with Boston type I keratoprosthesis implantation for unilateral visual impairment.

Evaluation of anterior chamber depth in aphakic and pseudophakic patients with Boston type 1 keratoprosthesis

Abstract Purpose To assess anterior chamber depth in aphakic and pseudophakic patients with Type 1 Boston Keratoprosthesis using anterior segment optical coherence tomography. Methods Sixteen patients who underwent Boston Type 1 Keratoprosthesis implantation were evaluated for anterior chamber depth by the non‐contact technique of AS‐OCT. Longitudinal cuts were used in evaluation of AC depth. Functional AC depth was defined as the distance between the back plate of the KPro and the anterior surface of the iris. Anatomic AC depth was defined as the distance from the posterior surface of donor cornea to the iris. Both functional and anatomic AC depths were measured nasally and temporally. The distance between the back plate of the KPro and anterior surface of the posterior chamber intraocular lens (PCIOL) was also measured in pseudophakic patients. Results A total of 16 patients were included in this study. There were 9 pseudophakic and 7 aphakic patients. Anatomic AC depths ranged between 0.86mm to 3.2mm. Functional AC depths ranged from 0mm to 2.2mm. Pseudophakic patients had anatomic AC depths between 0.92mm and 3.1mm and functional AC depths between 0mm and 2.2mm. Aphakic patients had anatomic AC depths between 0.86mm and 3.2mm, and functional AC depths between 0mm and 2.2mm. The distance between the back plate of the KPro and PCIOL in pseudophakic patients ranged from 0.14mm to 2mm. Conclusion Anterior chamber depth measurement, combined with AC angle data provide valuable information in the setting of KPro implantation. This may be helpful in monitoring patients post‐operatively for anterior segment complications such as crowding of the AC, or occlusion of the angle.

Retinal detachments after Boston keratoprosthesis: incidence, predisposing factors and outcomes of repair

Abstract Purpose Knowledge of predisposing factors to retinal detachments in certain patient populations can guide surgical planning in Boston keratoprosthesis placement. Methods This is a retrospective, noncomparative, interventional case series. A review of 166 patients (203 eyes) who underwent Boston Keratoprosthesis implantation at the Massachusetts Eye and Ear Infirmary from 1993 to 2008 was performed. Most patients had very advanced ocular disease. Predisposing factors to retinal detachment and details of timing after surgery were investigated. Anatomical and visual outcomes of retinal detachment repair were analyzed. Results Table 1. Retinal detachment after K‐Pro implantation Category Number of Eyes Eyes with RD Autoimmune systemic disease 72 24 (33%) Chemical burns 14 3 (21%) Non‐autoimmune etiology 117 10 (8.5%) Eighty‐nine (89%) of patients with retinal detachments have visual outcomes of less than 20/200 despite surgical repair. Majority of retinal detachments in all three subgroups occurred within the first six months after K‐Pro placement. Conclusion These data suggest that a retinal detachment following K‐Pro implantation is more frequent in patients with autoimmune disease (where K‐Pro is generally not recommended). When they do occur, they portend a poor visual prognosis. Patients with underlying autoimmune systemic disorders should be warned of the higher risk of developing retinal detachments after keratoprosthetic surgery and warrant close co‐management with a vitreoretinal specialist.

The Boston Type I Keratoprosthesis: Improving Outcomes and Expanding Indications

To report the usefulness of the Boston type I keratoprosthesis (Massachusetts Eye and Ear Infirmary, Boston, MA) in the management of corneal opacification, corneal limbal stem cell failure, or both in a large single-surgeon series. Retrospective review of consecutive clinical case series. All patients undergoing keratoprosthesis implantation by a single surgeon (AJA) between May 1, 2004, and May 31, 2008. Data were collected regarding the preoperative characteristics of each eye undergoing keratoprosthesis implantation, the surgical procedure(s) performed, and the postoperative course. Statistical analysis was performed to identify factors influencing the incidence and severity of postoperative complications. Interval visual acuities, keratoprosthesis retention, and significant postoperative complications. Fifty-seven keratoprosthesis procedures were performed in 50 eyes of 49 patients. The primary indication for surgery was repeat corneal transplantation failure (68%), although no prior corneal surgery had been performed in 16% of eyes. Preoperative visual acuity was 20/200 or worse in all eyes, with 88% of eyes having preoperative vision of counting fingers, hand movements, or light perception. The percentage of eyes with postoperative visual acuity of 20/100 or better was 67% at 6 months (n = 45), 75% at 1 year (n = 28), 69% at 2 years (n = 13), and 100% at 3 years (n = 7). In the 31% of patients in whom preoperative vision in the contralateral eye was 20/50 or better, the postoperative vision in the operative eye improved to 20/50 or better in 47% at the last follow-up (average, 18 months; range, 4-49 months). The overall keratoprosthesis retention rate was 84% at an average follow-up of 17 months (79 person-years of follow-up), with 100% retention in 8 eyes with no history of prior corneal transplantation (14.8 person-years of follow-up). The most common postoperative complications were retroprosthetic membrane formation (22 eyes) and persistent epithelial defects (19 eyes). No cases of infectious endophthalmitis were encountered, and only 1 patient with a history of glaucoma required additional glaucoma surgery during the postoperative period. The Boston type I keratoprosthesis is an effective means of managing repeat corneal graft failure and corneal limbal stem cell failure with or without corneal opacification in patients with both unilateral and bilateral visual impairment.

Boston KPro experience in Barcelona

Abstract Purpose To describe the indications, intraoperative complications, post‐operative complications and anatomical and functional results of Type I Boston keratoprosthesis at our eye center in Barcelona. Methods Retrospective interventional case series on 24 eyes of 22 patients who underwent Boston keratoprosthesis implant from May 2006 to May 2008. Results The main indication for Boston keratoprosthesis implantation was a repeated failed graft (mean = 2.33 previous grafts). The most common principal pathologies were: bullous keratopathy, herpetic keratitis, aniridic keratopathy, corneal ectasia, calcific band keratopathy. No major intraoperative complications were noted and average time of surgery was 47 minutes. The mean follow‐up time was 7.42 months. The major post‐operative complications encountered were retroprosthetic membrane in 2 eyes, endophthalmitis in 2 eyes and corneal graft melting in 1 eye. The mean best corrected visual acuity improved from 0.015 pre‐operatively to 0.1 post‐operatively. Only one case of extrusion due to melting was encountered which was resolved by a reimplantation of the keratoprosthesis. Conclusion Our short‐term experience with the type I Boston Keratoprosthesis is a good alternative for patients with repeated graft failures. Improvement in visual acuity is immediate and only minor complications were encountered.

Complications of AlphaCor Keratoprosthesis

To describe the clinical and histopathologic features of intractable secondary glaucoma induced by AlphaCor keratoprosthesis. An elderly woman with pseudoexfoliation glaucoma and pseudophakic bullous keratopathy in the right eye had graft failures after penetrating keratoplasty. Her best-corrected visual acuity at presentation was counting fingers in the right eye and 20/30 in the left eye. Examination showed severe corneal neovascularization. Chirila keratoprosthesis type II was implanted in 2 stages. Ten months later, the patient developed dense retrocorneal membrane, 360 degrees occlusion of angles, intractable glaucoma, no light perception, and nasal stromal melting associated with partial extrusion of the keratoprosthesis. Histopathology revealed invasion of the porous material of the keratoprosthesis by reactive fibroblasts and multinucleated foreign-body giant cells. In the area of dehiscence, we noted thinning and lysis of the collagen fibers, infiltration of lymphocytes, and plasma cells with a sheet of fibroinflammatory tissue extending into the anterior chamber. Corneal stromal melting and retrocorneal prosthetic membrane formation after AlphaCor keratoprosthesis implantation led to intractable glaucoma and extrusion of the implant.

Strampelli's osteo‐odonto‐keratoprosthesis

Abstract Purpose: This presentation is meant for the keratoprosthesis session organized by Christopher Liu. The early technique for "osteo‐odonto‐keratoprosthesis" described first by Strampelli in 1963 is demonstrated converting the inclusion of an acrylic prosthesis into an "heterotopic autoplastic transplantation" for the management of chemical and thermal burns, autoimmune disease (Stevens‐Johnsons, Lyell), trachoma or pemphigoid scarring, etc. Methods: The surgery comprises three phases. Phase 1: Superficial keratectomy, cleaning and repair of the ocular surface and the fornices and transplantation of buccal mucosa from the internal lip onto the ocular surface. Phase 2: Removal of a superior canine surrounded by dentine and bone. After shaping an adequate lamina of tooth and bone a central trephination is performed to receive the optical PMMA cylinder which is glued into place with dental glue. Then the entire block is placed into the inferior orbital space for biointegration. Phase 3 consists in removal of the osteo‐odonto‐keratoprosthesis from the orbital socket, dissection of the buccal mucosa, central trephination of thehost cornea and fixation of the osteo‐odonto.keratoprosthesis into the corneo‐scleral bed. Results: Some results and variations of the early technique are illustrated and discussed. Conclusions: Although the technique was primitive and complicated, Strampelli's idea to use autoplastic tissue to incorporate the artificial prothesis into the ocular surface has to be coinsidered of great importance for the evolution of modern techniques of keratoprosthesis implantation.

Femtosecond Laser-Assisted Intracorneal Keratoprosthesis Implantation

To demonstrate femtosecond laser-assisted intracorneal keratoprosthesis implantation and determine the mechanical stability as a function of intraocular pressure. Eight human corneoscleral rims were mounted on an artificial anterior chamber. The femtosecond laser microkeratome was used to create a 2.5-mm diameter posterior corneal cap. A 7.2-mm-diameter lamellar stromal pocket was then created at mid-corneal depth. Finally, a 6-mm arc opening to the corneal surface was created at the periphery of the lamellar cut. The posterior lenticule was removed using corneal forceps and a 7.0-mm biopolymer keratoprosthesis was inserted into the stromal pocket. The surface wound was sealed using two 10-0 nylon sutures. A 3.0-mm anterior corneal opening was trephined to expose the keratoprosthesis. Intrachamber pressure was raised until wound leak was observed. Seven of the 8 implants withstood pressures of at least 135 mm Hg without implant extrusion. Femtosecond laser corneal dissection provides an alternative to more challenging manual dissection methods for keratoprosthesis implantation. Use of the femtosecond laser microkeratome will further refine keratoprosthesis surgical technique and may allow rapid and easy execution of the surgery.

Melting after keratoprosthesis implantation: the effects of medroxyprogesterone.

This study was conducted to evaluate the effect of topical medroxyprogesterone (MPG) following KPro implantation in human subjects in whom donor tissue grafts had been contraindicated by high risk of failure. Outcomes of implantation of the Chirila KPro, now known as AlphaCor, were reviewed with respect to postoperative MPG therapy. Ten of 45 (22%) patients had received MPG for a period of 12 months, while 35/45 (78%) had not. MPG treatment was halted because the drug is not approved as an adjunctive treatment of KPro patients. The main outcome measures were the incidence and timing of corneal stromal melting and visual acuity. Of those untreated with MPG, 34% developed a melt (mean follow-up 9.7 months), whereas of those who received MPG, 60% developed a melt (mean follow-up 28.4 months). However, mean time to melt onset for untreated cases was 8.8 months, whereas mean time to melt onset for treated cases was 23.2 months. There is a statistically significant association between time to melt onset, where melts occurred, and MPG therapy (chi2 = 0.001). In both groups, melts were strongly associated with a history of ocular HSV, which represented 17.1% of untreated and 20% of treated cases and is now considered a contraindication for AlphaCor. Preoperative visual acuities were in the range Perception Light (PL)-Count Fingers (CF) in all cases, whereas mean best postoperative best corrected visual acuity was 20/200 (range PL-20/30) in untreated cases and was 20/120 [range Hand Movements (HM)-20/30)] in MPG-treated cases. Although MPG may not influence the underlying incidence of melt-related complications, which are likely to be associated with other risk factors especially HSV, it may have a protective effect with regard to melt onset and severity. Controlled studies would assist evaluation of its use in this indication.