ORIGINAL RESEARCH published: 30 September 2021 doi: 10.3389/fmed.2021.749063 Long-Term Anatomical and Functional Survival of Boston Type 1 Keratoprosthesis in Congenital Aniridia Ariann Dyer 1,2† , Alix De Faria 1,2*† , Gemma Julio 1,2 , Juan Álvarez de Toledo 1,2 , Rafael I. Barraquer 1,2,3 and Maria Fideliz de la Paz 1,2‡ 1 Centro de Oftalmología Barraquer, Barcelona, Spain, 2 Institut Universitari Barraquer, Universitat Autònoma de Barcelona, Barcelona, Spain, 3 Department of Medicine, Universitat Internacional de Catalunya, Barcelona, Spain Purpose: To analyze the long-term anatomical survival, functional survival, and complications of Boston type 1 keratoprosthesis (KPro) in the eyes with congenital aniridia-associated keratopathy (AAK). Methods: A retrospective review of 12 eyes with congenital aniridia that underwent a Boston type 1 KPro surgery was conducted. A Kaplan–Meier analysis was performed. Edited by: Anatomical and functional success criteria were KPro retention and a best corrected Stefano Ferrari, Fondazione Banca degli Occhi del visual acuity (BCVA) ≤1.3 LogMAR (≥0.05 decimal) at the end of a follow-up period. Veneto Onlus - FBOV, Italy Postoperative complications were recorded. Reviewed by: Carina Koppen, Results: The mean preoperative BCVA was 2.1 ± 0.9 (range: 3.8–1) LogMAR, and University of Antwerp, Belgium glaucoma was a comorbidity in all the cases. Five years after the surgery, the overall Yoav Nahum, retention rate was 10/12 (83.3%), and 50% had functional success. Only three (25%) Rabin Medical Center, Israel of the 12 cases did not achieve a BCVA ≤1.3 LogMAR. The cumulative probability *Correspondence: Alix De Faria of anatomical success was 92, 79, and 79% after 1, 5, and 10 years, respectively. defariaalix@gmail.com The cumulative probability of functional success was 57 and 46% after 1 and 5 years, † These authors have contributed respectively. The mean anatomical and functional survival time was 10 ± 1.3 (95% IC = equally to this work and share first 7.5–12.3 years) and 3.8 ± 0.9 years (95% IC = 1.8–5.8 years), respectively. The most authorship common postoperative complication was retroprosthetic membrane (RPM) formation in ‡ Senior author 8/16 cases (66%). The mean number of complications per case was 2.4 ± 1.8 (0–6). Specialty section: Conclusions: The Boston type 1 KPro is a viable option for patients with AAK with This article was submitted to good anatomical and functional long-term results. Glaucoma is an important preoperative Ophthalmology, a section of the journal condition that affects functional results. Retroprosthetic membrane formation seems to Frontiers in Medicine have a higher incidence in this condition. Received: 28 July 2021 Keywords: aniridia, Boston type-1 keratoprosthesis, extrusion, retroprosthetic membrane, aniridia associated Accepted: 30 August 2021 keratopathy Published: 30 September 2021 Citation: Dyer A, De Faria A, Julio G, Álvarez de Toledo J, Barraquer RI and de la INTRODUCTION Paz MF (2021) Long-Term Anatomical and Functional Survival of Boston Congenital aniridia is a rare condition that affects 1/64,000 to 96,000 live births Type 1 Keratoprosthesis in Congenital and has a major impact on vision and, therefore, quality of life (1). Classic aniridia Aniridia. Front. Med. 8:749063. is a panocular phenotypically heterogeneous condition (1, 2) that includes the doi: 10.3389/fmed.2021.749063 partial or total absence of an iris, which may be associated with cataracts, foveal Frontiers in Medicine | www.frontiersin.org 1 September 2021 | Volume 8 | Article 749063 Dyer et al. Boston Kpro in Congenital Aniridia and optic nerve hypoplasia, aniridia-associated keratopathy a groove in the optical stem. Finally, the cornea was sutured as in (AAK), and nystagmus (3). It is also associated with mutations a standard PK. If an eye was pseudophakic, the intraocular lens in the PAX6 gene. Mutations in other genes contribute to other (IOL) was left in place; if it was phakic, the lens was removed, aniridia-like phenotypes with aniridia-related comorbidities (3– making the eye aphakic. 5). Postoperative treatment includes the use of a permanent Besides glaucoma, AAK is the most common cause of Proclear R (CooperVision Inc, Scottsville, NY, United States) soft progressive vision loss, and it can present as early as the first contact lens that is 16-mm diameter, and an 8.8-mm base curve decade of life; however, the median age of diagnosis is 33 placed at the end of the surgery, along with wide-spectrum years old (4). Aniridia-associated keratopathy is characterized topical antibiotics (ciprofloxacin 3 mg/ml TID for 1 week and by limbal stem cell deficiency, which causes progressive vancomycin 14 mg/ml BID to be continued for life), prednisolone vascular pannus, corneal conjunctivalization, recurrent epithelial acetate 1% (three to five times per day) with slow taper for 1 erosions, and subepithelial fibrosis, eventually leading to corneal month, and anti-glaucomatous treatment as deemed necessary. opacification (2). Because of limbal cell deficiency, penetrating A fornix rinse with povidone-iodine was performed every month keratoplasty (PK) is usually unsuccessful in the long term, and in all the patients after the 1st month of the surgery. keratolimbal allografts with or without subsequent PK may A retrospective review of the medical records of all patients be a better alternative; however, aggressive long-term systemic with congenital aniridia who underwent Boston type 1 KPro immunosuppression is required (2, 6). implantations from December 2010 to October 2019 was Reported evidence proposes a primary or secondary Boston conducted at the Centro de Oftalmología Barraquer. Three type 1 keratoprosthesis (KPro) to treat debilitating conditions experienced surgeons (AT, RIB, and MdP) implanted the Boston that carry poor prognoses with PK (2). Traditionally, patients type 1 KPro in all the studied eyes. with a KPro have been stratified into three broad categories Gender, age at surgery, visual acuity (VA), aniridia-related according to their preoperative diagnoses: (i) recurrent comorbidities, anatomical retention period, follow-up time, and immunologic rejection (including aniridia), (ii) chemical injury, postoperative complications were recorded and analyzed. The and (iii) autoimmune disease. The first category has a better pre- and postoperative best corrected visual acuity (BCVA) of all prognosis when a KPro is implanted. Additionally, a KPro is the patients were measured and recorded on a decimal scale and considered as a treatment option only after several graft failures then converted into a LogMAR scale for statistical analysis. (7, 8). The main outcomes were graft retention and the BCVA. The objective of this study was to analyze the long-term Secondary outcomes were postoperative complications. anatomical and functional survival and complications of the A Kaplan–Meier survival analysis was performed. Anatomic Boston type 1 KPro in 12 eyes with congenital aniridia. In the success was defined as prosthesis retention during the follow- last KPro study group meeting (2020), it was suggested that up period. Extrusion was considered as the exposure of the back patients with aniridia should be categorized as a separate group plate due to corneal melting that needs surgical resolution such rather than be included in the recurrent immunologic rejection as a lamellar patch or KPro exchange. category, as previously suggested by other authors (1). This is Functional success was defined as BCVA ≤1.3 LogMAR due to the higher incidence of complications in AAK than most (≥0.05 decimal) at the end of the follow-up period. The mean disorders included in this category (1). It is for this reason that time of functional success was the estimated mean time with a this study was conducted. maintained BCVA ≤1.3 LogMAR (≥0.05 decimal). The follow-up period represents the time between the KPro surgery and the last recorded appointment with no signs of MATERIALS AND METHODS extrusion, or the interval of time between the KPro surgery and the first extrusion, which is when it was diagnosed. The follow- This original article includes a retrospective review of 12 eyes up period for the functional survival analysis was the time with a (10 patients) with congenital aniridia that underwent Boston maintained BCVA ≤1.3 LogMAR. type 1 KPro surgeries at the Centro de Oftalmología Barraquer, Barcelona, Spain. RESULTS The subjects provided written informed consent for the surgery and to participate in clinical research projects at Demographic Data the Centro de Oftalmología Barraquer, Barcelona, Spain. The 12 eyes of 10 patients were studied. There were three (30%) Institutional review board approval was obtained for the male and seven (70%) female patients. Nine (90%) of the patients retrospective review of the clinical records of the patients, and were Caucasian, and one (10%) was African. The mean age at this study adhered to the tenets of the Declaration of Helsinki. surgery was 37.1 years (range: 5–63 years). The mean follow-up The surgical technique used for the implantation of the Boston time was 58.7 ± 41.4 months (range: 9–142 months). type 1 KPro has been described widely (9). In summary, an 8.5- to Table 1 shows a list of individual demographic and clinical 9-mm corneal donor button was trephined, and a 3-mm opening preoperative characteristics. The Boston type 1 Kpro was a was created at its center with a punch. The optical stem of the primary indication in seven eyes (58%), and the secondary KPro was placed through the central hole, the back plate was Boston type 1 Kpro was performed in five eyes (42%), which had located in place, and then a titanium locking ring was fixed into undergone previous PKs that, in some cases, had multiple failed Frontiers in Medicine | www.frontiersin.org 2 September 2021 | Volume 8 | Article 749063 Dyer et al. Boston Kpro in Congenital Aniridia TABLE 1 | Demographics and clinical preoperative features in each case. Eye code Age range Gender Preoperative BCVA (LogMar) Previous surgeries Comorbid conditions Additional procedure 1 35 F 2.1 LA, PK, CE+IOL, S N, OSD,G, FH,CC 2 37 F 1.3 CE+IOL,S N, OSD,G, FH,CC IOLR 3 72 M 3.2 CE N, OSD, G,CC 4 5 F 1.3 CE,S OSD,G, FH,CC V 5 6 F 2.3 CE,S OSD,G, FH,CC V 6 35 F 1.7 CE+IOL,GS OSD,G 7 63 F 1 LA, PK,CE+IOL,GS, SIOL N, OSD,G, FH 8 13 M 3.8 PK, CE+IOL,GS N, OSD,G, CC 9 33 F 3.2 LA, CE+IOL, GS N, OSD,G, CC 10 51 M 2.1 PK, CE+IOL N, OSD,G, FH,CC 11 38 F 1.6 LA, CE+IOL, GS, E N, OSD,G, CC 12 57 F 1.5 LA, PK,CE+IOL OSD,G, CC CC, congenital cataract; CE + intraocular lens (IOL), cataract extraction with IOL; CE, cataract extraction; E, epitheliectomy; F, female; FH, foveal hypoplasia; G, glaucoma; GS, glaucoma surgery; IOLR, IOL removal; M, male; N, nystagmus; LA, limbal allograft; OSD, ocular surface disease; PK, penetrating keratoplasty; RD, retinal detachment; S, strabismus; SIOL, suture of the IOL; V, vitrectomy. attempts. Five of the eyes (42%) had previously undergone ocular surface stem-cell treatments (limbal allografts) without success. Most of the patients had poor preoperative visual acuities. The mean preoperative BCVA was 2.1 ± 0.9 LogMAR (range: 3.8– 1 LogMAR). Aniridia-related comorbidities, such as nystagmus, were present in eight of the 12 cases (67%) and foveal hypoplasia was in six of the 12 cases (50%). All of the cases had both ocular surface diseases and glaucoma. Previously operated congenital cataracts were reported in 10 of the 12 cases (83%), and none of our patients suffered retinal detachments before the Boston type 1 KPro surgery. Anatomical Results The overall retention rate of the Boston type 1 KPro 5 years after the surgery was 83.3% (10/12). The mean follow-up for the anatomical survival analysis was 53.6 ± 36.6 months (range: 9– 142 months). The cumulative success rate by the Kaplan–Meier analysis was 92, 79, and 79% after 1, 5, and 10 years, respectively. Figure 1 illustrates these results. The mean anatomical survival time was 119 ± 15 months (95% CI = 90–148 months). Failures appeared in both eyes of the same patient. One of the failures underwent the first extrusion 9 months after the surgery. After that, several tectonic surgeries had to be performed because of continuous extrusions (see Table 2 for individual details). The second eye had its first extrusion after 49 months of follow-up and required a transmucosal Boston type 1 KPro procedure, as described by Camacho et al. (10), because of repeated extrusions that were not solved with tectonic grafts. The functional success was achieved in both cases before the first extrusion and both eyes maintained BCVA <1.3 LogMAR (≥0.05 decimal) during 15 and 55 months respectively after secondary rescue procedures, although visual acuity was progressively decreasing FIGURE 1 | Anatomical and functional survival analysis. in one case. Functional Results BCVA ≤1.3 LogMAR (≥0.05 decimal) throughout The overall rate of functional success 5 years after the entire follow-up period and improved their surgery was 50% (6/12). The eyes maintained a final BCVA with a mean difference of 0.7 ± 0.5 Frontiers in Medicine | www.frontiersin.org 3 September 2021 | Volume 8 | Article 749063 Dyer et al. Boston Kpro in Congenital Aniridia TABLE 2 | Individual data of postoperative complications and procedures. DuetTM , Salt Lake City, UT, United States). Other complications found were retinal detachment (33%), microbial keratitis (8%), Eye code Postoperative complication PostKPro ocular procedures sterile ulceration (8%), and endophthalmitis (8%). The mean 1 GEm, RPMm YM, YC, LTK, GDD, KProE number of complications per case was 2.4 ± 1.8 (range: 0–6). 2 GEm, RPMm YM, LTK, GDD, Table 2 illustrates postoperative individual complications and 3 SU, UIOP TT procedures after Boston type 1 KPro in aniridia. 4 RPMm YM 5 RPM, E PPV 6 - - DISCUSSION 7 RPMm, RD YM, PPV Aniridia-associated keratopathy is a major threat to vision in 8 RD PPV patients with aniridia, and it occurs in up to 90% of cases 9 MK, RPM YM (1, 2, 11). This is the result of limbal stem cell deficiency, which 10 - YC leads to progressive corneal scarring and eventual blindness (1). 11 RPM, RD YM, PPV This condition is very challenging to manage, and conventional 12 SU, RPM, RD PPV PK has been proven to be ineffective because it fails to address GE, graft extrusion; MK, microbial keratitis; SU, sterile ulceration; WD, wound dehiscence; the underlying cause; (2) PK with keratolimbal allografts requires RPM, retroprosthetic membrane; RD, retinal detachment, UIOP, uncontrolled IOP; serious systemic inmunosupression because of its higher than E, endophthalmitis; YM, yttrium-aluminum-garnet (YAG) membranotomy; YC, YAG capsulotomy; LTK, lamellar techtonic keratoplasty; GDD, glaucoma drainage devices; usual rate of immunological rejection (11). A keratoprosthetic KProE, Boston type 1 keratoprosthesis (KPro) exchange; TT, temporal tarsorrhaphy; PPV, implantation has become a treatment option in the past decade pars plana vitrectomy; m, multiple. for severe conditions that have low probabilities of success, and the Boston type 1 KPro is the one that is most commonly used, even as a primary indication (1, 2). LogMAR (range:0.2–1.7 LogMAR), compared with their All the cases in this study had poor preoperative visual acuities preoperative BCVA. (BCVA ≥ 1 LogMAR, 0.09 decimal scale), as seen in previous The mean follow-up for the functional survival analysis was studies on patients with aniridia (1, 2, 6, 11). We found that the 26.5 ± 30.2 months (range:0.5–87 months). Figure 1 illustrates rate of preoperative glaucoma (100%) was slightly higher than the cumulative probability of success by the Kaplan–Meier that described in publications (around 80%) (1, 2). The long analysis, which was 57 and 46% at 1 and 5 years, respectively. follow-up period of this cohort, compared with published studies The mean functional survival time was 46 months (95% CI: evaluating the clinical outcomes of patients with the congenital 22–69 months). aniridia spectrum after implantation with the Boston type 1 Of the six functional failures, three eyes did achieve a BCVA KPro, strengthens the reliability of our results. ≤1.3 LogMAR after the KPro surgery during a period of 6, 9, The KPro overall retention rate of 83.3% is lower than that and 38 months, with a maximum improvement of 2.15, 0.6, found by Rixen et al., Akpek et al., and Bakhtiari et al. (100%), and 0.25 LogMAR, respectively, compared with the preoperative but is similar to that found by Hassanaly et al. (77%) and Shah BCVA. However, other complications, such as uncontrolled et al. (87%) (1, 2, 5, 6, 11). This could possibly be attributed to intraocular pressure (IOP) (in one case) and retinal detachments the longer follow-up period, with one of the extrusions occurring with macular involvement (in two cases), compromised the VA, after 49 months (4 years). This is longer than the median follow- resulting in functional failure. up time published by some authors (2, 6, 11). Another reason Only three cases (25%) never achieved a BCVA ≤ 1.3 could be our strict definition of extrusion; no other authors LogMAR, even though two of these eyes did improve their VA clarified what they considered an extrusion and, in one case, (Figure 2 illustrates the BCVA changes in each case studied). Out anatomical success was considered even after the KPro had to of these three eyes, two started with very low VA (hand movement be changed (5). The probability of retention of the Boston type or light perception) due to aniridia-related comorbidities. The 1 KPro in our study population was 92, 79, and 79% after 1, 5, other eye suffered postoperative endophthalmitis that led to and 10 years, respectively. phthisis bulbi. The failures appeared to be due to corneal melting in both eyes of the same patient (9 months and 49 months after Postoperative Complications surgery). This could be due to an ocular surface/immunological The most common postoperative complications encountered personal predisposition. Several tectonic surgeries had to be were prosthesis extrusion (2/12−17%-, explained in anatomical performed in the first extruded KPro, and the second one results) and retroprosthetic membrane (RPM) formation required a transmucosal Boston type 1 KPro exchange after many (8/12−66%-). In five of the cases (40%), the complication failed tectonic grafts. This surgical technique may be considered occurred before 2 years, and in three (25%) after 2 years. The an alternative in patients with ocular surface/immunological recurrence of RPM was the most frequent complication in diseases (10). Other treatment options include a Boston type each case, occurring up to three times in the same eye. Each 2 KPro, osteo-odonto keratoprosthesis (OOKP), and osteo- case that required it was resolved by membranotomy with keratoprosthesis (OKP); however, these are usually indicated the yttrium-aluminum-garnet (YAG) laser (Lumenis Selecta R in eyes with advanced-stage ocular surface diseases (12, 13). Frontiers in Medicine | www.frontiersin.org 4 September 2021 | Volume 8 | Article 749063 Dyer et al. Boston Kpro in Congenital Aniridia FIGURE 2 | Best corrected visual acuity changes in the sample. There are limited outcome data on the Boston type 2 KPro significantly higher than the RPM formation in all Boston type in the literature (12), and fewer regarding type-2 implants or 1 patients, including other categories (31.7%) (15). They were OOKP in patients with aniridia (12, 13). This could be because able to demonstrate that aniridia increased the hazard of RPM patients with aniridia usually have acceptable tear functions and formation by 3.13 (95% confidence interval 1.1–8.89). Since good lid appositions, making the Boston type 1 KPro a more 2013, the Centro de Oftalmología Barraquer has only been using suitable option. titanium backplates, as they seem to be associated with less RPM All but one case improved their VA after the surgery, which formation than polymethyl methacrylate (PMMA) (16). is similar to other published studies (5, 6, 11). Nevertheless, 50% The frequency of complications and the high need for of the cases achieved ambulatory vision (VA > 0.025 decimal) postoperative procedures in our study group add evidence that (14) and functional success (BCVA ≤ 1.3 LogMAR) at the end there might be a physiopathologic process in these patients of the follow-up period, with this value being the limit for legal that makes them unique compared with non-aniridic cases blindness as defined by the WHO. These patients had vision (1). This could be due to aniridia fibrosis syndrome (5). good enough to see large objects at close range and the ability This suggests that aniridia should be considered a separate to move around in a familiar environment. These results are category in the stratification by the preoperative diagnoses comparable with the 43.5% obtained by Shah et al. after 4.5 years of KPro patients rather than be included in the recurrent of follow-up (1). immunologic rejection category (7). Because of the high rate of The probability of maintained VA over legal blindness limits complications, we recommend not to implant bilateral Boston in our study population was 57 and 46% at 1 and 5 years, type 1 KPro simultaneously. respectively, to our knowledge, this is the first time a Kaplan– A limitation of this study is its retrospective design and limited Meier survival analysis has been performed. In accordance with sample size due to the low incidence of the disease. A quality-of- other authors, we attribute the limitation of achieving greater life questionnaire could have added valuable data to the study. visual acuity in these patients to preexisting aniridia-related However, this study provides valuable information to the existing comorbidities such as foveal hypoplasia, nystagmus, and optic literature, especially related to the long follow-up time. nerve hypoplasia (1, 2, 6). Moreover, the factors that tapered the Based on our results, we conclude that the Boston type 1 KPro VA in our cohort were retinal detachment (33%) with macular is a viable option for the treatment of AAK, with good long- involvement and a high prevalence of preoperative glaucoma term results both anatomically and functionally. Uncontrolled (100%) and its progression. Nearly all publication considered glaucoma is an important condition that affects functional glaucoma as a major cause of visual loss that could have impacted results. Aniridia may be considered a separate category in Boston the visual outcome results (1, 2, 5, 6, 11). Retinal detachment type 1 KPro stratification, but this needs to be validated by was also described by Akpek et al. as the cause of visual future studies. impairment in one of 16 cases and by Hassanaly in 31% of cases (2, 11). Our current surgical technique includes a planned pars plana vitrectomy (PPV) to reduce the risk of postoperative DATA AVAILABILITY STATEMENT retinal detachment. Retroprosthetic membrane formation (66%) was the most The original contributions presented in the study are included common complication in our study. Rudnisky et al. found in the article/supplementary material, further inquiries can be a comparable rate (66.7%) in aniridia cases (15). This was directed to the corresponding author/s. Frontiers in Medicine | www.frontiersin.org 5 September 2021 | Volume 8 | Article 749063 Dyer et al. Boston Kpro in Congenital Aniridia ETHICS STATEMENT manuscript preparation. GJ: data analysis, interpretation, and manuscript preparation. RB: data analysis and Ethical review and approval was not required for the study interpretation. JÁ: data analysis and interpretation. MP: on human participants in accordance with the local legislation research design, data analysis, and interpretation. All and institutional requirements. Written informed consent to authors contributed to the article and approved the participate in this study was provided by the participants’ legal submitted version. guardian/next of kin. AUTHOR CONTRIBUTIONS ACKNOWLEDGMENTS AD and ADF: research design, data acquisition, We thank Raquel Larena for processing the data of research execution, data analysis, interpretation, and the manuscript. REFERENCES aniridia: a retrospective multicenter study. Am J Ophthalmol. (2007) 144:227–32. doi: 10.1016/j.ajo.2007.04.036 1. Shah KJ, Cheung AY, Holland EJ. Intermediate-term and long-term outcomes 12. Lee R, Khoueir Z, Tsikata E, Chodosh J, Dohlman CH, Chen with the boston type 1 keratoprosthesis in Aniridia. Cornea. (2018) 37:11– TC. Long-term visual outcomes and complications of Boston 4. doi: 10.1097/ICO.0000000000001412 keratoprosthesis type II implantation. Ophthalmology. (2017) 2. Hassanaly SI, Talajic JC, Harissi-Dagher M. Outcomes following Boston Type 124:27–35. doi: 10.1016/j.ophtha.2016.07.011 1 Keratoprosthesis implantation in aniridia patients at the University of 13. Iyer G, Srinivasan B, Agarwal S, Talela D, Rishi E, Rishi P, et al. Montreal. Am J Ophthalmol. (2014) 158:1–8. doi: 10.1016/j.ajo.2014.05.009 Keratoprosthesis: current global scenario and a broad Indian perspective. 3. Samant M, Chauhan BK, Lathrop KL, Nischal KK. Congenital aniridia: Indian J Ophthalmol. (2018) 66:620–9. doi: 10.4103/ijo.IJO_22_18 etiology, manifestations and management. Expert Rev Ophthalmol. (2016) 14. Chang YC, Hu DN, Wu WC. Effect of oral 13-cis-retinoic acid treatment on 11:135–44. doi: 10.1586/17469899.2016.1152182 postoperative clinical outcome of eyes with proliferative vitreoretinopathy. 4. Yazdanpanah G, Bohm KJ, Hassan OM, Karas FI, Elhusseiny AM, Am J Ophthalmol. (2008) 146:440–7. doi: 10.1016/j.ajo.2008. Nonpassopon M, et al. Management of congenital aniridia-associated 05.002 keratopathy: long-term outcomes from a tertiary referral center. 15. Rudnisky CJ, Belin MW, Todani A, Al-Arfaj K, Ament JD, Zerbe BJ, et al. Am J Ophthalmol. (2020) 210:8–18. doi: 10.1016/j.ajo.2019.11.003 Risk factors for the development of retroprosthetic membranes with Boston 5. Bakhtiari P, Chan C, Welder JD, De La Cruz J, Holland EJ, Djalilian keratoprosthesis type 1: multicenter study results. Ophthalmology. (2012) AR. Surgical and visual outcomes of the type i Boston Keratoprosthesis 119:951–5. doi: 10.1016/j.ophtha.2011.11.030 for the management of aniridic fibrosis syndrome in congenital aniridia. 16. Todani A, Ciolino JB, Ament JD, Colby KA, Pineda R, Belin Am J Ophthalmol. (2012) 153:967–71.e2. doi: 10.1016/j.ajo.2011.10.027 MW, et al. Titanium back plate for a PMMA keratoprosthesis: 6. Rixen JJ, Cohen AW, Kitzmann AS, Wagoner MD, Goins KM. Treatment clinical outcomes. Graefe’s Arch Clin Exp Ophthalmol. (2011) of aniridia with boston type i keratoprosthesis. Cornea. (2013) 32:947– 249:1515–8. doi: 10.1007/s00417-011-1684-y 50. doi: 10.1097/ICO.0b013e318281724a 7. Belin MW, Güell JL, Grabner G. Suggested guidelines for reporting Conflict of Interest: The authors declare that the research was conducted in the keratoprosthesis results: consensus opinion of the cornea society, Asia Cornea absence of any commercial or financial relationships that could be construed as a Society, EuCornea, PanCornea, and the KPRO study group. Cornea. (2016) potential conflict of interest. 35:143–4. doi: 10.1097/ICO.0000000000000703 8. Kang KB, Karas FI, Rai R, Hallak JA, Kang JJ, de la Cruz J, et al. Five year Publisher’s Note: All claims expressed in this article are solely those of the authors outcomes of Boston type I keratoprosthesis as primary versus secondary penetrating corneal procedure in a matched case control study. PLoS ONE. and do not necessarily represent those of their affiliated organizations, or those of (2018) 13:1–12. doi: 10.1371/journal.pone.0192381 the publisher, the editors and the reviewers. Any product that may be evaluated in 9. de la Paz MF, Salvador-Culla B, Charoenrook V, Temprano J, this article, or claim that may be made by its manufacturer, is not guaranteed or Álvarez de Toledo J, Grabner G, et al. Osteo-odonto-, Tibial endorsed by the publisher. bone and Boston keratoprosthesis in clinically comparable cases of chemical injury and autoimmune disease. Ocul Surf. (2019) Copyright © 2021 Dyer, De Faria, Julio, Álvarez de Toledo, Barraquer and de la Paz. 17:476–83. doi: 10.1016/j.jtos.2019.04.006 This is an open-access article distributed under the terms of the Creative Commons 10. Camacho L, Soldevila A, Fideliz de la Paz M. Transmucosal Boston Attribution License (CC BY). The use, distribution or reproduction in other forums keratoprosthesis type I in a patient with advanced ocular cicatricial is permitted, provided the original author(s) and the copyright owner(s) are credited pemphigoid. Cornea. (2020) 39:1563–5. doi: 10.1097/ICO.0000000000002413 and that the original publication in this journal is cited, in accordance with accepted 11. Akpek EK, Harissi-Dagher M, Petrarca R, Butrus SI, Pineda R, academic practice. No use, distribution or reproduction is permitted which does not Aquavella J V, et al. Outcomes of Boston keratoprosthesis in comply with these terms. Frontiers in Medicine | www.frontiersin.org 6 September 2021 | Volume 8 | Article 749063