Boston Type I Keratoprosthesis Research Articles

Clinical Outcomes of Boston Type-I Keratoprosthesis Implantation: A 4-year Retrospective Study in South Korea

Purpose: To evaluate the long-term results of Boston type-I keratoprosthesis implantation in Korea.Methods: Medical records of six patients (six eyes) who underwent Boston type-I keratoprosthesis implantation between August 2018 and November 2019 were retrospectively reviewed for more than 36 months.Results: The mean follow-up period was 44.3 ± 7.0 months. Best corrected visual acuity (BCVA) improved significantly for all six eyes, from 2.33 ± 0.51 logarithm of the minimum angle of resolution (logMAR) to 0.67 ± 0.59 logMAR. The vision recovered immediately after the surgery in all patients. Retroprosthetic membrane developed in three of the patients, but the visual acuity remained unchanged. Anatomical success was achieved in all six eyes after Boston type-I keratoprosthesis implantation.Conclusions: The long-term analysis of Boston type-I keratoprosthesis implantation showed a faster recovery and improved visual acuity compared with conventional penetrating keratoplasty. Without the use of systemic immunosuppressants, all six eyes showed long-term survival of the Boston keratoprosthesis. Boston type-I keratoprosthesis implantation may be used in patients with recurrent graft failure after keratoplasty. This was the first study investigating the long-term results of Boston keratoprosthesis implantation in Korean patients.

Keratoprostheses: Last Hope for the Most Severe Corneal Diseases

Corneal blindness affects over 8 million adults and 1.5 million children worldwide, making it one of the top 5 causes of blindness. Depending on the recipient's corneal condition corneal transplantation may not be a viable treatment option. In such seemingly no-alternative situations, keratoprosthesis implantation can be an option in some patients. In terms of numbers, two types of keratoprostheses are currently used: 1. Keratoprostheses with biological haptics made of tooth or tibia bone. 2. The Boston type I-keratoprosthesis. Both types have optics made of PMMA. The most common complication is the formation of an optically disturbing retroprosthetic membrane behind the optic, which can usually be removed with YAG laser. Causes of blindness after keratoprosthesis implantation are glaucoma, endophthalmitis and retinal detachment. The extrusion rate of the Boston type I-keratoprosthesis seems to be higher than after keratoprosthesis implantation with biological haptic. Autoimmunological corneal diseases have increased extrusion rates and higher rates of endophthalmitis when compared to non-autoimmunological diseases. Visual outcomes after keratoprosthesis implantation are potentially very good and usually limited by extracorneal concomitant diseases. Advances in glaucoma diagnostic (OCT, implantation of intraocular pressure sensors), standard glaucoma prophylaxis by medication or surgery, modern retinal surgery and better treatment options in case of extrusion improve the prognosis of keratoprosthesis surgery. Still, the ideal technique for permanent anchoring of artifical optics in biological tissue has yet to be developed.

Patient-Reported Vision-Related Quality of Life After Boston Type I Keratoprosthesis.

To determine patient-reported vision-related quality of life (VR-QoL) after Boston type I keratoprosthesis (BKPro) and its determinants. A cross-sectional study including consecutive consenting BKPro patients was conducted. The French National Eye Institute Visual Function Questionnaire-25 measured postoperative VR-QoL. Medical charts were retrospectively reviewed for demographics, ocular comorbidities, indication for surgery, postoperative visual acuity (VA), and complications. Univariate analyses were used to identify VR-QoL determinants. Multivariate linear regression was additionally performed for patients operated unilaterally, using VR-QoL as the dependent variable and age, sex, and postoperative VA as covariates. P < 0.05 indicated statistical significance. Sixty-three patients, aged 63 ± 13 years, with a mean follow-up of 54 ± 19 months, were included. VR-QoL was measured 53 ± 18 months postoperatively. "Composite" VR-QoL scores in patients with unilateral (n = 51) and bilateral (n = 12) BKPro were 65 ± 23 and 63 ± 19, respectively, and did not significantly differ between the 2 groups (P = 0.71). In patients with unilateral BKPro, VR-QoL was determined by postoperative VA in the better eye, which was the contralateral nonoperated eye in most cases. Achieved vision in the operated eye contributed to VR-QoL when vision in the contralateral nonoperated eye was poorer. In the bilateral BKPro group, VR-QoL was determined by postoperative VA in the better eye and the number of ongoing complications. Five-year VR-QoL scores were lower in BKPro patients compared with healthy cohorts reported in the literature and were similar after unilateral and bilateral BKPro surgery. The main determinant of postoperative VR-QoL was postoperative vision in the better eye.

Boston Type I Keratoprosthesis: Antibacterial Resistance and Microbiota Evaluation of Soft Contact Lenses

To evaluate microbiota colonizing soft contact lenses (CL) in eyes with Boston type I keratoprosthesis (BKPro), and determine the prevalence of resistance to fourth-generation fluoroquinolone (FQ). Prospective, observational study. Patients with BKPro using CL as routine who were in postoperative follow-up in the Department of Ophthalmology of the Federal University of Sao Paulo, and volunteered to participate in the study. All patients were under a prophylactic scheme of topical 0.5% moxifloxacin 3 times a day and topical 5% povidone-iodine (PI) at the time of CL exchange. Patients on scheduled replacement scheme of CL had their lenses removed and sent for microbiological analysis. Standard culture methods were used for microorganism identification and susceptibility to different antibiotics was tested. Main outcome measure was prevalence of resistance to fourth-generation FQ. Among the 19 eyes, 12 eyes (63%) had at least 1 positive bacterial culture. The most prevalent isolates were Staphylococcus epidermidis and other coagulase-negative staphylococci. Actinomyces viscosus was isolated in 1 CL. Fungal cultures were all negative. Of the 12 eyes with culture bacterial growth, resistance to fourth-generation FQ (0.5% moxifloxacin) was identified in 6 different eyes (50%). None presented infectious complications. FQ-resistant bacteria were isolated in some patients. Although our prophylactic antibiotic regimen has been efficient in preventing bacterial infection, this analysis demonstrated that prophylaxis with PI and low FQ dose might increase resistance to antibiotics. Investigations in this field may help to outline future changes of prophylactic guidelines and therapeutic strategies.

AB088. Quality of life and visual function in patients with Boston type I keratoprosthesis

Background: To determine patient-reported vision-related quality of life (VR-QoL) following Boston type I keratoprosthesis (BI-KPro) surgery and its association with postoperative best-corrected visual acuity (BCVA).

The Role of the Back Plate in Angle Anatomy with the Boston Type I Keratoprosthesis.

To quantitatively evaluate the angle anatomy in eyes with the Boston type I keratoprosthesis (B-KPro) differing in the back plate (BP) material and size using anterior segment optical coherence tomography. B-KPro eyes with poly(methyl methacrylate) (PMMA) (7.0 and 8.5 mm) and titanium (7.0, 8.5, and 9.5 mm) BPs were imaged with anterior segment optical coherence tomography. The angle opening distance at 500 μm from the scleral spur (AOD500), trabecular iris surface area at 500 μm from the scleral spur (TISA500), and trabecular iris angle at 500 μm from the scleral spur (TIA500) were measured. Among the visible quadrants, the average, the temporal, the widest, and the narrowest angle of each eye were included in the analysis. Average time between B-KPro implantation and imaging was 7.5 ± 1.4 years for a PMMA BP and 2.4 ± 2.3 years for a titanium BP (P < 0.0001). We analyzed 17 B-KPro eyes with PMMA BPs and 24 B-KPro eyes with titanium BPs. The average AOD500 (394.1 ± 226.9 vs. 454.5 ± 255.6 μm, P = 0.44), average TIA500 (26.2 ± 14.2 vs. 29.8 ± 13.9 degrees, P = 0.43), and average TISA500 (0.15 ± 0.08 vs. 0.17 ± 0.10 μm, P = 0.52) were not statistically different between eyes with PMMA and titanium BPs, nor were the temporal, the narrowest, and the widest angle measurements of each eye (all P > 0.05). Similarly, no significant differences were found between the angle measurements of B-KPro eyes with a titanium BP diameter of 8.5 or 9.5 mm (all P > 0.05). We successfully visualized the angle anatomy in 66.1% of the imaged eyes, including all BPs studied. Neither the material nor the size of the B-KPro BP had a significant impact on the angle anatomy.

Corneal Melt after Boston Keratoprosthesis: Clinical Presentation, Management, Outcomes and Risk Factor Analysis

ABSTRACTPurpose: To determine the presentation, risk factors, and outcomes of keratolysis after Boston type I keratoprosthesis (B-KPro).Methods: Retrospective chart review.Results: A total of 16 (14%) of the 110 eyes (96 patients) which underwent B-KPro implantation developed keratolysis at an average 20 ± 11 months. Retroprosthetic membrane (RPM), infectious keratitis, and corneal dellen were identified in 31%, 25%, and 13% of corneal melts, respectively. Five eyes had keratolysis without a readily identifiable cause. RPM (odds-ratio, OR = 4.4, p = 0.02) and infectious keratitis (OR = 17.6, p<0.0005) were confirmed as significant risk factors. Retinal detachment (p = 0.001) and choroidal detachment (p = 0.003) were more common in eyes with keratolysis. Management included B-KPro removal or exchange (n = 7), amniotic membrane transplantation (n = 1), tectonic corneal transplantation (n = 2), medical treatment (n = 4), and observation (n = 2).Conclusions: The risk of keratolysis following B-Kpro increases with the development of RPM and infectious keratitis. Patients with keratolysis had higher complication rates and should receive rigorous monitoring.

Long-term outcomes of Boston typeIkeratoprosthesis for Chinese severe corneal blindness

Background Corneal blindness is associated with the change of corneal structure, and conventional keratoplasty cannot regain vision in these eyes.Keratoprosthesis is well used for patients unsuitable for standard keratoplasty.Boston type Ⅰ keratoprosthesis is one of the most commonly employed in the world, but it has not been well used in China. Objective This study was to evaluate the long-term outcome and safety of Boston type Ⅰ keratoprosthesis in China. Methods A pilot study was carried out for a descriptive prospective clinical trial under the approval of Ethic Committee of Henan Provincial People's Hospital and Henan Eye Institute.Sixteen eyes of 15 patients with severe corneal blindness which were not suitable for usual management were recruited, with the gender being males and ages of (50.4±13.0) years.The causes of blindness included thermal and chemical injury in 8 eyes of 7 patients, herpes simplex keratitis in 3 eyes of 3 patients, Stevens-Johnson syndrome in 1 eye of 1 patient, mechanical trauma in 2 eyes of 2 patients and infectious keratitis in 2 eyes of 2 patients.Fourteen of the 16 eyes received therapeutic keratoplasty once or more before, and 7 eyes had glaucoma history, pseudophakia was in 5 eyes and aphakia was in 4 eyes.The best corrected visual acuity (BCVA) is 0.05 in 1 eye, finger counting in 7 eyes and hand motion in 8 eyes.Implantation of Boston type Ⅰ keratoprosthesis was performed on the 16 eyes and followed-up for (47.5±23.8) months (ranged from 19 throughout 84 months) after obtaining of written informed consent from each patient.The postoperative BCVA, postoperative complication and eye numbers of keratoprosthesis in site were recorded. Results The surgeries of Boston type Ⅰ keratoprosthesis or combination procedures, such as lens or intraocular lens (IOL) extraction, iridectomy, cyclitic membrane removal and vitrectomy were successful in all the eyes.One month after surgery, the postoperative BCVA was obviously improved in 14 eyes, with the BCVA≥1.0 in 3 eyes, 0.5≤BCVA<1.0 in 4 eyes and 0.1≤BCVA<0.5 in 7 eyes, the vision was unchanged in 2 eyes due to end-stage glaucoma before operation.BCVA remained ≥0.1 in 9 eyes at the end of following-up duration.Postoperative complications included retromembrane proliferation in 7 eyes, corneal melting in 6 eyes and glaucoma in 4 eyes.Severe postoperative complications were fungal keratitis, endophthalmitis and device extrusion respectively and keratoprosthesis prolapse, so penetrating keratoplasty was carried out to replace the keratoprosthesis.Implanted Boston type Ⅰ keratoprosthesis was in site in 13 eyes at the end of following-up. Conclusions The Boston typeⅠkeratoprosthesis might be a viable method to provide visual recovery for the eyes with severe corneal blindness unsuitable for standard keratoplasty.It is mandatory for long-term follow-up and prevention and management of postoperative complications. Key words: Corneal transplantation; Corneal diseases/surgery; Prosthesis implantation; Treatment outcome; Postoperative complications; Visual acuity; Chinese; Prospective studies

Boston Keratoprosthesis: Outcomes and Complications: A Report by the American Academy of Ophthalmology

To review the published literature on safety and outcomes of the Boston type I keratoprosthesis (BI-KPro) for the surgical treatment of corneal opacification not amenable to human cadaveric corneal transplantation. Searches of peer-reviewed literature were conducted in PubMed and the Cochrane Library in December 2012, July 2013, and January 2014 without date restrictions. The searches were limited to studies published in English and yielded 587 citations. The abstracts of these articles were reviewed, 48 articles were selected for possible clinical relevance, and 22 were determined to be relevant for the assessment objectives. Nine studies were rated as level II evidence and 13 studies were rated as level III evidence. Excluded were level III evidence, case reports, review articles, letters, editorials, and case series with fewer than 25 eyes. In 9 articles, a best-corrected Snellen visual acuity (BCSVA) of 20/200 or better occurred in 45% to 89% of eyes. Five articles described a BCSVA of 20/50 or better in 43% to 69% of eyes, and 4 articles found a BCSVA of 20/40 or better in 11% to 39% of eyes. Retention rates of the BI-KPro ranged from 65% to 100%. Reasons for loss of vision after BI-KPro implantation most commonly included corneal melts resulting from exposure keratopathy, endophthalmitis, and infectious keratitis or corneal ulceration. The 2 most common complications after surgery were retroprosthetic membrane formation (range, 1.0%-65.0%; mean ± standard deviation [SD], 30.0±19.0%) and elevated intraocular pressure (range, 2.4%-64.0%; mean ± SD, 27.5±18.1%). The 2 most common posterior segment complications were endophthalmitis (range, 0%-12.5%; mean ± SD, 4.6±4.6%) and vitritis (range, 0%-14.5%; mean ± SD, 5.6±4.7%). The reviewed articles on BI-KPro use suggest that the device improves vision in cases of severe corneal opacification that were not amenable to corneal transplantation using human cadaveric keratoplasty techniques. A number of severe anterior and posterior segment complications can develop as follow-up continues, making ongoing close observation paramount for patients undergoing this surgery. These complications include infection, device extrusion, and permanent vision loss.

Endophthalmitis in Boston keratoprosthesis: case series and review of literature.

To report the clinical and microbiological characteristics of infectious endophthalmitis after Boston type I keratoprosthesis (B-K-Pro) implantation. Retrospective analysis of 136 eyes that received a B-K-Pro type 1 between 1999 and 2012 was performed. Five eyes with a diagnosis of exogenous endophthalmitis after B-K-pro type 1 were identified and information about demographic data, indication for K-Pro, post-operative bandage contact lens use, post-operative prophylactic antibiotic use, timing and clinical presentation of endophthalmitis, gram stain and culture results of intraocular fluid and preoperative and post-operative visual acuity were collected. The incidence of endophthalmitis was 3.67% (5 of 136 eyes) and average time to develop endophthalmitis was 5.62 months (range 2 days to 8 months). Mean patient age was 31.4 years (5 to 65 years). The surgical indications included corneal injury due to chemical burns (n = 2), multiple failed grafts secondary to microbial keratitis (n = 2) and congenital glaucoma with congenital herpetic keratitis (n = 1). Post-Boston K-Pro, the visual acuity ranged from light perception (LP) to 20/50. K-pro was explanted in 4 patients. There was bacterial and fungal growth in two patients each and one vitreous did not grow anything. All the eyes were phthisical at last visit. Infectious endophthalmitis after K-Pro implantation in our study had a higher incidence, early onset and extremely poor visual outcome compared with post-cataract surgery endophthalmitis, as reported in literature. Not only bacterial but also fungal infections are an important etiology for infectious endophthalmitis in these cases.

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.