Retroprosthetic Membrane Formation Research Articles

Outcomes Following Boston Type 1 Keratoprosthesis Implantation in Aniridia Patients at the University of Montreal

To describe outcomes after Boston Type 1 Keratoprosthesis (KPro) surgery in aniridic eyes. Retrospective, interventional case series. University-based tertiary care institution. Twenty-six aniridic eyes of 19 patients who underwent KPro implantation by a single experienced surgeon (M.H.-D.) between October 27, 2008 and January 16, 2012. Preoperative and postoperative best-corrected visual acuity (BCVA), intraoperative and postoperative complications, and keratoprosthesis retention. Mean age was 56 years (range, 28-72); 10 patients were male. Seven patients had bilateral procedures. No intraoperative complications were encountered. Preoperatively, BCVA was 20/300 or worse in all eyes. After a mean follow-up time of 28.7±13.5 months (range 4-50), the most recent BCVA was 20/200 or better in 14 eyes. Visual potential was limited by preexisting terminal glaucoma (n=2), phthisis after retinal detachment (n=4), and suprachoroidal hemorrhage (n=2). Other postoperative complications included retroprosthetic membrane formation (n=15), infectious keratitis (n=1), extrusion (n=2), and corneal melt (n=4). Uncomplicated vitritis was reported in 6 eyes. No endophthalmitis occurred in this series. Most eyes have glaucoma and are on medical treatment. The overall retention rate of the initial prosthesis was 77%. The prognosis in aniridic patients after KPro is variable. Meticulous follow-up and a subspecialty team approach are of utmost importance.

Gamma-Irradiated Corneas as Carriers for the Boston Type 1 Keratoprosthesis

The Boston keratoprosthesis (KPro) is the most commonly used KPro worldwide. There are limited data on the outcomes when irradiated corneas are used as KPro carriers. We report a retrospective analysis of corneal transplantations performed in a regular surgical mission setting in Beirut, Lebanon, using the Boston KPro type 1 and gamma-irradiated carrier corneas, and we describe visual outcomes, complications, and retention percentage. We conducted a retrospective analysis of 17 consecutive eyes from 16 patients who underwent Boston KPro type 1 implantation at the Beirut Eye Specialist Hospital between December 2010 and July 2012. Patient medical records were reviewed for preoperative, intraoperative, and postoperative details. Postoperatively, 9 (52.9%), 5 (29.4%), and 2 (11.7%) eyes had a corrected visual acuity of 20/400 or better, 20/100 or better, and 20/40 or better, respectively, at the most recent follow-up visit. A total of 16 eyes (94.1%) improved in corrected visual acuity over the course of follow-up. Overall, 13 eyes (76.4%) developed at least 1 complication after surgery. Retroprosthetic membrane formation was the most common complication, occurring in 10 eyes (58.8%). Neither infectious keratitis nor corneal stromal necrosis was noted during the follow-up period. The retention percentage was 94.1%. The visual acuity outcomes, incidence of complications, and retention percentage of the KPro using gamma-irradiated carrier corneas are comparable with the outcomes of KPro implantation reported in the literature using fresh grafts as carriers. KPro with irradiated corneal carrier grafts seems to be an effective option to increase the supply of transplantation suitable corneas in remote areas, where fresh corneal grafts may be scarce.

Wound Anatomy After Type 1 Boston KPro Using Oversized Back Plates

To compare the anatomy of the graft-host junction and anterior chamber angle after Boston Keratoprosthesis (KPro) placement using oversized (9.5-mm) and standard (8.5-mm) back plates. Six patients with 9.5-mm titanium back plates and 10 patients with 8.5-mm titanium back plates were imaged by anterior segment optical coherence tomography 6 to 12 months after KPro placement. The location of the graft-host junction in relation to the back plate, the corneal thickness at the graft-host junction, and the anterior chamber angle were assessed. The clinical outcomes and incidence of retroprosthetic membrane (RPM) formation in this cohort were retrospectively evaluated. The oversized back plates completely covered the graft-host junction in all quadrants, allowing the complete apposition of the posterior surface of the carrier graft with the host cornea, with decreased graft-host junction wound thickness. The standard back plates covered the posterior aspect of the carrier graft but not the graft-host junction or the host cornea, resulting in a significantly thicker graft-host junction. None of the patients with larger back plates developed a significant RPM during a 12-month follow-up period. One patient with a larger back plate developed a corneal melt at the KPro stem as a result of chronic exposure. Oversized KPro back plates effectively cover the graft-host junction without any adverse effects on angle anatomy or wound healing. This may be a strategy to provide better wound apposition, reduce RPM formation, and reduce angle closure from iris synechiae to the wound.

Boston type 1 KPros in India ‐ Indications, contraindications and device modifications

AbstractBoston Keratoprosthesis is the most commonly used Keratoprosthesis worldwide. It is a collar button kind of Keratoprosthesis carried on a corneal graft. The prerequisites for a type 1 Boston Keratoprosthesis include the following 1) Bilateral corneal blindness 2) Reasonably healthy posterior segment 3) Well controlled Intraocular pressure or combine a shunt surgery with the Keratoprosthesis 4) Moist eye 5) Good blink 6) Well formed fornices 7) Committed to regular follow ups and Understands the potential risk involved in the surgery The current indications for Boston type 1 Keratoprosthesis are 1) Multiple failed grafts 2) Limbal stem cell deficiency 3) Ocular burns( chemical/thermal) 4) Aniridia 5) Pediatric corneal opacities 6) Silicone oil induced keratopathy Contraindications 1) Poor /Incomplete blink 2) Severely damaged lid apparatus post chemical injuries 3) Keratinized ocular surface (would be an indication for Boston type 2/MOOKP) Design modifications like addition of more holes in the back plate, the use of the titanium locking ring, Use of a bandage contact lens and prophylaxis with antibiotics with the present design have improved the outcome and retention rates of the Keratoprosthesis. Further research in the form of a titanium back plate to reduce the rates of retroprosthetic membrane formation is being tried.

High-Resolution Spectral Domain Anterior Segment Optical Coherence Tomography in Type 1 Boston Keratoprosthesis

To report the results of imaging using high-resolution, Fourier domain anterior segment optical coherence tomography (AS-OCT) to evaluate patients with a type 1 Boston Keratoprosthesis (KPro). We performed a retrospective comparative study of patients in whom we implanted the Boston KPro. A total of 26 eyes of 23 patients from the Cornea Service at the University of California Davis Eye Center were included. Subjects were evaluated with the Spectralis AS-OCT (Heidelberg Engineering GmbH). Preoperative diagnoses for KPro surgery included failed corneal transplant (69%), chemical burn (23%), and aniridia (8%). The average age of patients was 63.2 years (range, 17-88 years). Fifty-four percent of the patients were female. The mean duration between the KPro surgery and the acquisition of high-resolution AS-OCT imaging was 35.8 months (range, 2-90 months). The most commonly observed finding was retroprosthetic membrane formation, which we found in 77% of KPro eyes. In 65% of KPro eyes, we identified epithelium behind the front plate, and in 54%, we identified an epithelial lip over the anterior surface of the KPro front plate. In 31% of KPro eyes, we identified periprosthetic cysts, gaps or spaces, and thinning in the corneal carrier graft. Fourier domain AS-OCT is a useful noninvasive imaging technique in patients with a KPro and provides the ability to identify changes that are sometimes difficult to appreciate by clinical evaluation. The higher resolution Fourier domain systems may aid in the clinical diagnosis and management of pathology that might not be imaged with instruments of lower resolution. AS-OCT has the potential for monitoring the anatomic stability of an implanted KPro and may also help to monitor for complications. Moreover, high-resolution imaging may enhance our understanding of periprosthetic anatomy.

Boston type 1 keratoprosthesis outcomes in ocular burns

To report the outcomes of Boston type I keratoprosthesis (BKPro) in the management of ocular burn injuries. This was a prospective study including all cases of BKPro implantation for ocular burns at the External Diseases and Cornea Service of the Federal University of São Paulo, between February 2008 and February 2010. Ten patients (10 eyes) were enrolled. Procedures performed to manage ocular injury were identified, and data were collected regarding patients' ocular history, surgical procedure(s) performed, and postoperative outcomes, including visual acuity, retention, complications and required surgical procedures. A total of 11 Type 1 BKPro were implanted in 10 eyes of 10 patients. The mean follow-up period was 25.7 ± 10.8 months. Preoperative best-corrected visual acuity (BCVA) ranged from count fingers to light perception. Postoperative BCVA was better than 20/200 in 90% of the patients and better than 20/60 in 60% of the patients. The overall BKPro retention rate was 90%. The most common complications were retroprosthetic membrane formation (50%) and persistent corneal epithelial defect evolving to corneal melting (40%). Patients who underwent ocular surface procedures such as limbal transplantation prior to BKPRo implantation had a lower incidence of corneal melting/thinning (p = 0.07), although this was not statistically significant. The anatomical and functional results identified in this study support the use of BKPro in managing bilateral limbal stem cell deficiency secondary to ocular burns.

Visual Outcomes of Boston Keratoprosthesis Implantation as the Primary Penetrating Corneal Procedure

To report the short-term visual outcomes and complications of keratoprosthesis surgery as the primary penetrating corneal procedure for patients at high risk for conventional corneal transplantation. A retrospective chart review was conducted of 21 eyes of 19 patients who underwent either Boston keratoprosthesis type I or type II as the primary penetrating corneal procedure from February 2007 to March 2011. Nineteen type I (90.5%) and 2 type II (9.5%) Boston keratoprosthesis procedures were performed in 19 patients. Mean follow-up was 14.6 months (range, 6-36.3 mo). Primary indications for surgery included chemical or thermal injury, aniridia, and Stevens-Johnson syndrome. Preoperative best-corrected visual acuity (BCVA) ranged from 20/100 to light perception and was count fingers or worse in 20 eyes (95.2%). At last follow-up for all eyes, 15 eyes (71.4%) achieved BCVA≥20/200 and 4 eyes (19%) improved to BCVA≥20/50. No intraoperative complications occurred. Postoperative complications include retroprosthetic membrane formation (47.6%), cystoid macular edema (33.3%), elevated intraocular pressure (23.8%), glaucoma progression (14.3%), and endophthalmitis (4.8%). The initial keratoprosthesis was retained in 19 eyes (90.5%). The Boston keratoprosthesis, based on early follow-up, is a good alternative as a primary penetrating corneal procedure in a select group of patients with very poor prognosis for penetrating keratoplasty. Although complications can occur and require close monitoring, visual acuity significantly improved in the majority of patients.

Chronic Hypotony Associated With the Boston Type 1 Keratoprosthesis

To report the occurrence of chronic hypotony as a complication following Boston type 1 keratoprosthesis (KPro) implantation and to determine associated risk factors. Retrospective case series. The medical records of all patients undergoing KPro implantation between January 2004 and November 2010 at the Wilmer Eye Institute were reviewed. Patients who developed chronic hypotony following Boston type 1 KPro implantation not attributable to anatomic problems (eg, retinal detachment, overfiltering glaucoma tube shunts, tissue necrosis with aqueous leak) or other causes were identified. Demographics and preoperative, intraoperative, and postoperative clinical findings were analyzed. Light microscopic examination of an enucleated globe as well as fibrous retroprosthetic membranes excised at the time of vitrectomy from another patient was performed. Sixty-eight eyes received KPro implantation over the study period. Six eyes experienced chronic hypotony, with a median time of 18.5 months between KPro implantation and the onset of hypotony. The incidence of chronic hypotony in this series was calculated to be 3.7% at 1 year (95% CI = 0.9%-14.0%) and 13.3% at 2 years (95% CI = 5.5%-30.0%). Of the 6 eyes that developed chronic hypotony, 5 had a previous history of glaucoma or ocular hypertension, but only 3 had a glaucoma drainage implant. All eyes progressing to chronic hypotony were noted to have a retroprosthetic membrane prior to the onset of hypotony. Cox regression modeling demonstrated an increased risk of chronic hypotony in eyes with retroprosthetic membranes (P < .01) but no increase in risk for older patients (P > .1), eyes with glaucoma drainage implants (P > .5), or a previous history of multiple donor corneal transplants (P > .5). Chronic hypotony can be a significant complication of KPro implantation and should be assessed carefully in eyes with retroprosthetic membranes. Further study of an association between hypotony and retroprosthetic membrane formation may be useful to gain insight into the mechanism of this complication and potential prevention or treatment options.

International Results with the Boston Type I Keratoprosthesis

To determine the indications and outcomes of Boston type 1 keratoprosthesis (Massachusetts Eye and Ear Infirmary, Boston, MA) surgery performed outside of North America and to compare them with those obtained in the United States by the surgeon who trained the international surgeons. Retrospective review of consecutive clinical case series. One hundred ninety-four patients (223 keratoprosthesis procedures performed in 205 eyes) who received Boston type 1 keratoprosthesis at 11 ophthalmology centers in Armenia, India, Indonesia, Nepal, Philippines, Russia, and Saudi Arabia between May 1, 2006, and July 1, 2011 (international series), and at the Jules Stein Eye Institute between May 1, 2004, and July 1, 2011 (University of California, Los Angeles [UCLA] series). Data were collected for each procedure regarding the preoperative characteristics of each eye, the surgical procedure(s) performed, and the postoperative outcomes. Statistical analysis was performed to identify significant differences between the international and UCLA series in terms of retention and complications. Interval visual acuities, keratoprosthesis retention, and significant postoperative complications. In the international series, 113 Boston type I keratoprostheses were implanted in 107 eyes of 100 patients. The most common indication for surgery was corneal graft failure (n = 50; 44%) followed by chemical injury (n = 30; 27%). Although only 2% of eyes had a preoperative corrected distance visual acuity (CDVA) of 20/20 to 20/200, 70%, 68%, and 59% of eyes had a postoperative CDVA of 20/20 to 20/200 at 6 months, 1 year, and 2 years after surgery, respectively. Ninety-one of the 113 keratoprostheses implanted (80.5%) were retained at a mean follow-up of 14.2 months, for a retention failure rate of 22 per 134.6 eye-years (0.163/eye-year). The most common postoperative complications were retroprosthetic membrane formation (27%) and sterile corneal necrosis (18%). The only postoperative complication that was more common in the international series than in the UCLA series was infectious endophthalmitis, which developed in 9% of eyes. Boston keratoprosthesis is a viable means of managing repeat graft failure and ocular chemical injury outside of North America, with similar visual acuity outcomes, retention rates, and incidence rates of postoperative complications to those obtained by North American surgeons.

Boston Keratoprosthesis Type 1 Surgery

This study aims to determine whether frozen corneas can be successfully used as carriers of the Boston keratoprosthesis (KPro). Prospective study of 37 patients undergoing KPro surgery with fresh or frozen corneas as carriers. Patients were randomized to receive either a fresh corneal graft or a frozen corneal graft during implantation of the Boston KPro. The randomization depended on availability of fresh versus frozen corneas offered by the local eye bank. All surgeries were performed by the same experienced surgeon. Outcome measures included retention of the device, level of preoperative and postoperative visual acuities (VAs), and complications. The indication for Boston KPro was corneal graft failure in 24 eyes; 13 patients had KPro as a primary procedure. The assembly of the Boston KPro and surgery were uneventful in all cases. Mean follow-up was 9.65 months. Median preoperative VA was counting fingers (range, 20/100 to light perception) in the fresh cornea group (19 eyes) and hand motions (range, 20/150 to light perception) in the frozen cornea group (18 eyes). Median postoperative VA were 20/150 (range, 20/30 to hand motions) and 20/150 (range, 20/40 to counting fingers) in the fresh and frozen cornea groups, respectively. Inflammation and retroprosthetic membrane formation were the most common complications with similar rates between the 2 groups. The device retention rate was 100% at the end of the follow-up period. Frozen and fresh corneal donors seem equally efficient and safe as carriers of the Boston KPro with similar recuperation of VA and no untoward complications, such as melt, leaks, or endophthalmitis.

Risk Factors for the Development of Retroprosthetic Membranes with Boston Keratoprosthesis Type 1: Multicenter Study Results

The purpose of this study was to identify possible risk factors for retroprosthetic membrane (RPM) development in a large, multicenter cohort of patients receiving a Boston type 1 keratoprosthesis. Cohort study. The final analysis included 265 eyes of 265 patients who underwent implantation of a Boston keratoprosthesis type I device between January 2003 and July 2008 by 1 of 19 surgeons at 18 medical centers. Forms reporting preoperative, intraoperative, and postoperative parameters were prospectively collected and subsequently analyzed at a central data collection site. The primary outcome was the presence or absence of an RPM during the follow-up period. The average age of patients was 63.3±19.1 years, 48.5% of the patients were female, and 52.5% of procedures were performed on the right eye. The mean follow-up time was 17.8±14.9 months. The majority (85.4%; n = 222) had undergone an average of 2.2±1.2 (range, 1-8) penetrating keratoplasties before keratoprosthesis implantation, and 38 eyes (14.6%) received a primary keratoprosthesis. The overall RPM formation rate was 31.7% (n = 84). The most significant risk factor for RPM development was infectious keratitis (as a surgical indication for keratoprosthesis surgery itself), resulting in a rate of RPM formation of 70.6%. As an independent risk factor, the hazard ratio (HR) of RPM development in these eyes was 3.20 (95% confidence interval, 1.66-6.17). Aniridia was also an independent risk factor for RPM development (HR, 3.13; 95% confidence interval, 1.10-8.89). Formation of RPM is a common complication of keratoprosthesis surgery, occurring in approximately one-third of cases. Eyes at the highest risk of RPM development are those receiving corneal replacement for infectious keratitis and aniridia.

Boston type 1 keratoprosthesis: the New York Eye and Ear experience

The Boston keratoprosthesis has had variable success rates in the past. However, significant modifications to design and management have recently led to successful outcomes. This study was undertaken to evaluate the outcomes of the Boston type 1 keratoprosthesis at our institution. A retrospective chart review was performed of all Boston type 1 keratoprosthesis procedures conducted at a single practice at the New York Eye and Ear Infirmary from December 2006 to August 2010. Outcome measures included visual acuity, retention rates, and complications. In all, 58 eyes of 51 patients who received a Boston type 1 keratoprosthesis were included. The most common indication for the keratoprosthesis was failed penetrating keratoplasty (PK) (81.0%; mean 2.4±1.3 PKs per eye). Glaucoma was the most common comorbidity (75.9%). Pre-operative best corrected visual acuity (BCVA) was <20/400 in 87.9% of eyes. At last follow-up, 43.1% of eyes had a BCVA of 20/200. Retention rate was 87.9% over an average follow-up of 21.5±11.4 months (median 22 months, range 3-47 months). Complications increased with time, with 65.5% of eyes experiencing at least one event by 6 months and 75.9% by 1 year. The most common post-operative complication was retroprosthetic membrane formation (50.0%). The Boston type 1 keratoprosthesis provides visual recovery for eyes with multiple PK failures or with poor prognosis for primary PK, showing excellent retention rates. However, there is a trend towards a decline in visual acuity with time and the development of late complications, highlighting a need for longer-term studies.

The Boston Keratoprosthesis in the Management of Corneal Limbal Stem Cell Deficiency

To report the outcomes of the Boston type I keratoprosthesis (Massachusetts Eye and Ear Infirmary, Boston, MA) in the management of corneal limbal stem cell deficiency (LSCD). A retrospective review of all cases of keratoprosthesis implantation performed by a single surgeon (A.J.A.) between May 1, 2004, and March 31, 2010. Procedures performed for the management of LSCD were identified, and data were collected regarding the patients' ocular history, surgical procedure(s) performed, and postoperative outcomes, including interval visual acuities, retention, complications, and required surgical procedures. The outcome data from patients with LSCD were compared with those of individuals who underwent keratoprosthesis implantation for indications other than LSCD. Twenty-eight keratoprostheses were performed in 23 eyes of 22 patients with LSCD. The most common indications for surgery were chemical injury (7 eyes) and Stevens-Johnson syndrome (6 eyes). Preoperative corrected distance visual acuity (CDVA) was better than counting fingers in 4% of eyes with LSCD and in 9% of eyes without LSCD. Postoperative CDVA was 20/50 or better in 69%, 88%, and 67% of eyes with LSCD at 1, 2, and 3 years after keratoprosthesis implantation, respectively. Each of these percentages is higher than the percentage of eyes without LSCD obtaining CDVA of 20/50 or better at each time point. Whereas the retention failure rate in eyes with LSCD (0.148/eye-year) was higher than the rate in eyes without LSCD (0.114/eye-year), when eyes with Stevens-Johnson syndrome were excluded from the LSCD group, the non-Stevens-Johnson syndrome LSCD retention failure rate (0.056/eye-year) was half that of the non-LSCD group. The most common postoperative complications in eyes with LSCD were persistent corneal epithelial defect (PED) formation (56.5% of eyes) and sterile corneal necrosis (30%), whereas retroprosthetic membrane formation (46%) was the most common postoperative complication in eyes without LSCD, followed by PED formation (23%). The development of a PED was found to be a significant risk factor for sterile corneal stromal necrosis and infectious keratitis. Boston type I keratoprosthesis implantation results in a significant improvement in CDVA in the majority of patients with LSCD, with CDVA of 20/50 or better in more than two-thirds of eyes up to 3 years after surgery. PED formation is the most common postoperative complication in eyes with LSCD and is associated with an increased rate of sterile stromal necrosis and a lower retention rate in eyes undergoing keratoprosthesis implantation for immune-mediated LSCD. These results support the use of the Boston type I keratoprosthesis in managing bilateral, non-immune-mediated LSCD.

AlphaCor artificial cornea: clinical outcome

The purpose of this study was to describe the long-term results of AlphaCor implantations, and to evaluate the main complications and risk factors. Retrospective analysis of preoperative and follow-up data from 15 AlphaCor implantations. Analysis of outcomes, trends, and associations was performed and compared with data from published clinical trials and a literature review. The survival rate of the device at 1, 2, and 3 years was 87%, 58%, and 42%, respectively. Postoperative visual acuity ranged from hand movement to 0.8. The most significant complications were stromal melt (nine cases), optic deposition (three eyes), and retroprosthetic membrane formation (three eyes). The most common device-unrelated complication was trauma (three patients). All complications were managed without loss of the eye. AlphaCor provides a treatment option for patients with corneal blindness in which a donor tissue graft would not succeed.

Titanium back plate for a PMMA keratoprosthesis: clinical outcomes

To compare the rate of retroprosthetic membrane (RPM) formation in Boston Keratoprosthesis (BKPro) with polymethyl methacrylate (PMMA) versus titanium backplates. Retrospective comparative chart review. Multicenter study population: a total of 78 eyes with keratoprosthesis implants with either PMMA or titanium backplates were included in the study. To be included in the study, all subjects had to have completed a minimum of 6-month follow-up period. Incidence of RPM development at 6-month postoperative period was noted across the study population. PMMA and titanium backplates were then compared by their rate of association with subsequent RPM. Twenty-three out of 55 eyes (41.8%) with PMMA backplates and three out of 23 eyes (13.0%) with titanium backplates had developed an RPM at 6months after implantation. The titanium backplates were associated with significantly less RPM formation than PMMA backplates (p = 0.014, Chi-square test). Titanium seems to be associated with less RPM formation than PMMA when used as a material for the BKPro back plate.

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.

Boston keratoprosthesis with titanium back plate

Abstract Purpose Following implantation of a Boston Keratoprosthesis (BKPro), formation of a retroprosthetic membrane (RPM) is an indication of postoperative intraocular inflammation. The purpose of this retroactive study has been to compare BKPro back plates made of titanium with the standard PMMA back plates. Any difference in RPM formation would guide our future choice of material for the device. Methods The design was a retroactive analysis looking at the surgical outcomes after 6 months in patients who had BKPro implants. Pediatric cases were excluded. The indications for having a KPro implant were broadly divided into three categories: autoimmune (n=12), chemical burns (n=11), and others (non‐autoimmune) (n=55). Three types of back plates were studied: 1) threaded (screw‐on) PMMA (n=39), 2) non‐threaded (snap‐on) PMMA (n=16) and 3) non‐threaded titanium back plates (n=23). Main outcome measured was incidence of RPM formation at 6 months after surgery that warranted removal by either YAG laser membranotomy or surgery. Results The percentage of patients who developed RPM was greatest in the threaded PMMA group (46%), followed by the non‐threaded PMMA (31%), although this difference did not achieve statistical significance (p=0.5). The non‐threaded titanium group showed the least RPM formation (13%), which was significantly less than both the threaded PMMA (p=0.002) and the threadless PMMA (p=0.043) groups. Conclusion Titanium KPro back plates induce less RPM than PMMA back plates, threaded or non‐threaded. It seems that the titanium plates in this setting are more tissue friendly and cause less inflammation than PMMA.

Boston type I in pediatric patients

Abstract Purpose To present a retrospective review of keratoprosthetic implantation and retention in patients with congenital corneal opacities. Methods Pediatric patients younger than seven years old, the average age of permanent visual loss from understimulation of the visual cortex, were selected from a single center Boston Type I keratoprosthesis database and categorized by 1) primary diagnosis, 2) short‐term visual outcome, and 3) post‐operative complications. Results Seventeen patients, with an age range of 41 days up to 6 years, were selected from a database of over one hundred and forty patients. Six had a primary diagnosis of sclerocornea and eleven had Peter’s anomaly. Visual outcome after one year improved in fourteen of the patients, with patients who previously could not detect light to subsequently being able to fixate and follow or even read allen cards. The remaining three patients showed no improvement in visual acuity but also no worsening from their baseline condition. In terms of post‐operative complications of the optic, two had retroprosthetic membrane formation, and another patient required replacement of the keratoprosthesis due to phthisis and optic melting. From a retinal standpoint, four patients had retinal detachments. There were no cases of choroidal hemorrhaging or hypotony in these patients. Conclusion Based on visual outcome, the Boston Type I keratoprosthesis is a safe and effective procedure for patients with congenital corneal opacities. With great retention, the artificial cornea is a viable option for prevention of amblyopia. Due to comorbidities such as congenital cataracts, congenital glaucoma, and retinal detachments, it is crucial to have glaucoma and vitreo‐retinal surgeons on hand when managing and implanting keratoprosthesis in a pediatric population.

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.