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Boston keratoprosthesis type 1 device leak
CASE SERIES
Boston keratoprosthesis type 1 device leak Kinda Najem, MD,*,† Mikael Sebag, MD, FRCSC,*,† Mona Harissi-Dagher, MD, FRCSC*,† ABSTRACT ● RÉ SUMÉ Objective: To report a leak at the cornea–anterior front plate interface of the Boston keratoprosthesis type 1 (KPro) leading to hypotony. Design: Retrospective interventional case series. Participants: Three patients (3 eyes) who experienced development of hypotony after Boston KPro type 1 implantation surgery at the Centre Hospitalier de l’Université de Montréal. Methods: Medical records of the 3 patients at our institution were reviewed with regard to preoperative and postoperative best corrected visual acuity (BCVA), digital intraocular pressure (IOP), time to diagnosis of hypotony, related complications, and the need for medical and surgical treatment. Results: Pre-KPro BCVA ranged from counting fingers to light perception and improved to a mean of 20/100 in the operated eye. The incidence rate of leaks after KPro type 1 implantation was 2.7% (3 patients). The hypotony was noted at a mean of 13.7 months postoperatively. All patients had uveitis and vitritis preceding choroidal and retinal detachments, and required vitreoretinal surgeries for repair. In all patients, an objective leak through the cornea–anterior front plate interface of the KPro was seen intraoperatively by the vitreoretinal surgeon. Mean BCVA in these patients stabilized at 20/300 after the complication resolved, with a mean IOP of 10 mm Hg. Conclusions: Leak next to the KPro stem can occur after several months and can lead to significant visual loss. Prompt recognition and team management of this complication are required. Objet : Compte-rendu d’une fuite de Keratoprothèse Boston de type 1 (KPro) dans l’interface de la cornée avec la plaque antérieure, menant à une hypotonie. Nature : Rétrospective d’une série de cas d’intervention. Participants : Trois patients (trois yeux) qui avaient développé une hypotonie à la suite d’une chirurgie d’implantation de KPro Boston de type 1 au Centre hospitalier de l’Université de Montréal. Méthodes : Les dossiers médicaux des trois patients de notre centre institutionnel, avant et après la chirurgie, ont été examinés concernant la meilleure correction d’acuité visuelle (MCAV), la pression intraoculaire (PIO) digitale, le temps nécessaire pour diagnostiquer l’hypotonie, les complications relatives et le besoin de traitements médicaux et chirurgicaux. Résultats : La MAVC pré-KPro s’est échelonnée du compte des doigts à la perception de la lumière et s’est améliorée à 20/100 en moyenne dans l’oeil opéré. L’incidence des fuites après l’implantation de KPro de type 1 était de 2,7 % (3 patients). L’hypotonie a été remarquée en moyenne 13,7 mois après l’opération. Les patients avaient tous eu une uvéite et une vitréite précédant des décollements choroïdiens et rétiniens et requis des chirurgies vitréorétiniennes de réparation. Chez tous les patients, la fuite objective par l’interface de la cornée avec la plaque antérieure de la cornée de KPro a été examinée pendant l’opération par le chirurgien vitréorétinien. La moyenne de MAVC de ces patients s’est stabilisée à 20/300 après la résolution des complications, avec une moyenne de PIO de 10 mmHg. Conclusions : Une fuite adjacente à la tige du KPro peut se produire après plusieurs mois et mener à une importante perte de vision. La rapidité de la reconnaissance et celle de l’équipe de traitement s’imposent.
The Boston keratoprosthesis type 1 (KPro; Massachusetts Eye and Ear Infirmary, Boston, Mass.) has become a successful treatment for corneal blinding pathologies1; however, complications can occur. The purpose of this study is to report 3 cases who experienced a leak at the cornea–anterior front plate interface of the KPro leading to ocular hypotony.
METHODS In this retrospective, interventional case series, the medical records of 3 patients (3 eyes) who experienced From the *Department of Ophthalmology, Centre Hospitalier de l’Université de Montréal, Hôpital Notre-Dame; and †Department of Ophthalmology, Université de Montréal, Montréal, Que.
hypotony after Boston KPro type 1 surgery at the Centre Hospitalier de l’Université de Montréal (CHUM) were studied. Study approval was granted by the CHUM ethics committee. Informed consent was obtained from each patient for the collection and analysis of preoperative, intraoperative, and postoperative parameters. Preoperative assessment, operative protocol, and progress notes were reviewed with respect to patient demographics, ophthalmic diagnoses, preoperative and postoperative best corrected visual acuities (BCVAs), digital intraocular pressure (IOP), and postoperative complications. Hypotony and its related complications were Can J Ophthalmol 2014;49:106–108 0008-4182/14/$-see front matter & 2014 Canadian Ophthalmological Society. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jcjo.2013.08.005
Originally received Feb. 19, 2013. Final revision Aug. 4, 2013. Accepted Aug. 23, 2013 Correspondence to Kinda Najem, MD, Department of Ophthalmology, Centre Hospitalier de l’Université de Montréal, Hôpital Notre-Dame, 1560 Sherbrooke Street East, Montréal QC H2L 4M1; kinda.najem@ gmail.com
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CAN J OPHTHALMOL — VOL. 49, NO. 1, FEBRUARY 2014
Boston keratoprosthesis type 1 device leak—Najem et al. Table 1—Patient demographics: preoperative and postoperative clinical features Patient no.
Age, y Sex
Preoperative BCVA
Preoperative diagnosis in operated eye
Time to diagnosis of hypotony, mo
HSV keratitis, 2 failed PK, OAG, white cataract Aniridia, glaucoma, cataract Aniridia glaucoma 1 failed PK aphakia
12
1
53
M
LP
2
63
M
LP
3
71
M
CF
Postoperative complications Anterior uveitis, vitritis, hypotony, CD, funnel RRD, PVR, RPM, ERM, leak through KPro Anterior uveitis, vitritis, hypotony, CD, RRD, leak through KPro RPM and YAG membranotomy 3, hypotony, hemorrhagic CD, RRD, vitritis, ERM, hypotony, leak through KPro
18 11
BCVA after PPV
BCVA at last follow-up
20/150
HM
20/100
20/300
20/100
20/150
BCVA, best corrected visual acuity; PPV, pars plana vitrectomy; M, male; HSV, herpes simplex virus; PK, penetrating keratoplasty; OAG, open-angle glaucoma; CD, choroidal detachment; RRD, rhegmatogenous retinal detachment; RPM, retroprosthetic membrane; ERM, epiretinal membrane; KPro, Boston keratoprosthesis type 1; HM, hand motion; LP, light perception; CF, counting fingers; PVR, proliferative vitreoretinopathy.
studied, and time of occurrence of this complication postKPro implantation was noted.
RESULTS Patient demographics and preoperative and postoperative clinical features are summarized in Table 1. The incidence rate of leak after KPro type 1 implantation was 2.7%. All patients were men with a mean age of 62.3 years. Two had a preoperative diagnosis of aniridia, and 1 patient had a history of unsuccessful penetrating
keratoplasties secondary to herpes simplex virus (HSV) keratitis. Preoperative BCVA ranged from counting fingers to light perception and improved to a mean of 20/100 (range 20/100 to 20/150) postoperatively. Several postoperative complications, listed in Table 1, were noted. Although the first postoperative months were uneventful, a relentless inflammation, either as anterior uveitis and/or vitritis, persisted despite treatment with oral prednisone and corticosteroid drops. The patient with a history of HSV was treated preoperatively and postoperatively with prophylactic acyclovir. Posterior segment complications ensued in all cases. Hypotony was
Fig. 1 — Optical coherence tomography images of Patient 3 showing abnormal thinning around the Boston keratoprosthesis type 1 (KPro) stem. A, Three months after surgery: no thinning seen around the KPro stem. B, Six months after surgery: white arrow shows the abnormal thinning around the KPro stem. (Pictures taken at Ophthalmology Department, Hoˆpital NotreDame, Montreal, Que.) CAN J OPHTHALMOL — VOL. 49, NO. 1, FEBRUARY 2014
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Boston keratoprosthesis type 1 device leak—Najem et al. diagnosed at a mean of 13.7 months postoperatively (range 11–18 months). Seidel test was negative on clinical examination. Digital IOP was approximately r5 mm Hg. All patients required pars plana vitrectomy (PPV) with silicone oil exchange for repair. In all patients, an objective leak through the cornea–anterior front plate interface of the KPro was seen intraoperatively by the vitreoretinal surgeon (M.S.) as fluid exiting the eye at the interface under an infusion pressure of 25 mm Hg. In 1 patient, the leak was no longer evident in the post-PPV period and IOP increased. In the second patient, a repeat KPro was required in the affected eye to stop the persistent leak. In the third patient, the persistent leak was repaired with glue. Mean BCVA in these patients stabilized at 20/300 (range 20/150 to hand motion) after the leak was repaired with a mean IOP of 10 mm Hg (range 5–15 mm Hg).
DISCUSSION In our study, all leaks were at the corneal–anterior front plate interface. Detection of a lower range of normal levels of IOP at an earlier stage in the postoperative follow-up may be hindered by the inaccuracy of digital palpation.2,3 Lower pressure may have been an ongoing process that was detected only when frank hypotony and further complications became apparent. All patients manifested chronic and unrelenting inflammation around the time hypotony was diagnosed. None of our patients had ciliary body membranes to explain their hypotony. The leak was confirmed in all patients during PPV. Although Seidel was checked, no leak was documented before PPV. However, it is well-known that once IOP is very low, the leak may stop or become imperceptible on examination. It is a fact that there is no biointegration between the Boston KPro and the surrounding corneal tissue. Hence this potential space between the 2 adjoining surfaces may allow leakage from the KPro stem–corneal interface. Garcia et al.4 showed evidence of subclinical levels of thinning and desiccation present as a gap between the KPro-donor cornea interface on optical coherence tomography (OCT) imagery in 2 patients. No evidence of leakage was demonstrated when mild pressures were applied on the device.4 In our study, 1 patient had abnormal corneal thinning on OCT images and could have been more susceptible to the infusion pressures of PPV, leading to a potential leak (Fig. 1). No anomalies of the corneal carrier or the device were found in the other 2 patients. Wound remodeling may play a role in corneal thinning, increasing the vulnerability of the stem–corneal
108
junction to leaks. The wound remodeling may be macroscopic as in Patient 3. This thinning may also be microscopic, hence delaying the diagnosis until more overt complications occur. In fact, in Patient 2, the leak became apparent only during PPV where the higher infusion pressure revealed the wound junction weakness. Recent studies reporting on hypotony after Boston keratoprosthesis5,6 suggest a possible association between hypotony and the presence of retroprosthetic membrane. Retroprosthetic membranes were present in Patients 1 and 3, and may have predisposed to the leak in these 2 cases as well. Finally, although Patients 2 and 3 have aniridia, aniridic fibrosis syndrome,7 by definition, was not diagnosed because intraocular inflammation was present and no membranes were found extending into the retina. In conclusion, a leak is possible and can lead to devastating visual consequences after KPro implantation. Chronic inflammation, retroprosthetic membranes, and consequent wound remodeling may be the main culprits explaining the leaks in our patients. Appropriate and timely management with glaucoma and retina specialists can restore or stabilize visual acuity. Lifelong follow-up is of utmost importance in KPro patients because blinding and severe complications can occur long after surgery.
Disclosure: The authors have no proprietary or commercial interest in any materials discussed in this article.
REFERENCES 1. Hicks CR, Fitton JH, Chirila TV, Crawford GJ, Constable IJ. Keratoprostheses: advancing toward a true artificial cornea. Surv Ophthalmol. 1997;42:175-89. 2. Banitt M. Evaluation and management of glaucoma after keratoprosthesis. Curr Opin Ophthalmol. 2011;22:133-6. 3. Chew HF, Ayres BD, Hammersmith KM, et al. Boston keratoprosthesis outcomes and complications. Cornea. 2009;28:989-96. 4. Garcia JP Jr, Ritterband DC, Buxton DF, De la Cruz J. Evaluation of the stability of Boston type I keratoprosthesis-donor cornea interface using anterior segment optical coherence tomography. Cornea. 2010;29:1031-5. 5. Dokey A, Ramulu PY, Utine CA, et al. Chronic hypotony associated with the Boston type I keratoprosthesis. Am J Ophthalmol. 2012;154:266-71. 6. Sivaraman KR, Hou JH, Allemann N, de la Cruz J, Cortina MS. Retroprosthetic membrane and risk of sterile keratolysis in patients with type I Boston keratoprosthesis. Am J Ophthalmol. 2013;155:814-22. 7. Tsai JH, Freeman JM, Chan CC, et al. A progressive anterior fibrosis syndrome in patients with postsurgical congenital aniridia. Am J Ophthalmol. 2005;140:1075-9.
CAN J OPHTHALMOL — VOL. 49, NO. 1, FEBRUARY 2014
Boston keratoprosthesis type 1 device leak Kinda Najem, MD,*,† Mikael Sebag, MD, FRCSC,*,† Mona Harissi-Dagher, MD, FRCSC*,† ABSTRACT ● RÉ SUMÉ Objective: To report a leak at the cornea–anterior front plate interface of the Boston keratoprosthesis type 1 (KPro) leading to hypotony. Design: Retrospective interventional case series. Participants: Three patients (3 eyes) who experienced development of hypotony after Boston KPro type 1 implantation surgery at the Centre Hospitalier de l’Université de Montréal. Methods: Medical records of the 3 patients at our institution were reviewed with regard to preoperative and postoperative best corrected visual acuity (BCVA), digital intraocular pressure (IOP), time to diagnosis of hypotony, related complications, and the need for medical and surgical treatment. Results: Pre-KPro BCVA ranged from counting fingers to light perception and improved to a mean of 20/100 in the operated eye. The incidence rate of leaks after KPro type 1 implantation was 2.7% (3 patients). The hypotony was noted at a mean of 13.7 months postoperatively. All patients had uveitis and vitritis preceding choroidal and retinal detachments, and required vitreoretinal surgeries for repair. In all patients, an objective leak through the cornea–anterior front plate interface of the KPro was seen intraoperatively by the vitreoretinal surgeon. Mean BCVA in these patients stabilized at 20/300 after the complication resolved, with a mean IOP of 10 mm Hg. Conclusions: Leak next to the KPro stem can occur after several months and can lead to significant visual loss. Prompt recognition and team management of this complication are required. Objet : Compte-rendu d’une fuite de Keratoprothèse Boston de type 1 (KPro) dans l’interface de la cornée avec la plaque antérieure, menant à une hypotonie. Nature : Rétrospective d’une série de cas d’intervention. Participants : Trois patients (trois yeux) qui avaient développé une hypotonie à la suite d’une chirurgie d’implantation de KPro Boston de type 1 au Centre hospitalier de l’Université de Montréal. Méthodes : Les dossiers médicaux des trois patients de notre centre institutionnel, avant et après la chirurgie, ont été examinés concernant la meilleure correction d’acuité visuelle (MCAV), la pression intraoculaire (PIO) digitale, le temps nécessaire pour diagnostiquer l’hypotonie, les complications relatives et le besoin de traitements médicaux et chirurgicaux. Résultats : La MAVC pré-KPro s’est échelonnée du compte des doigts à la perception de la lumière et s’est améliorée à 20/100 en moyenne dans l’oeil opéré. L’incidence des fuites après l’implantation de KPro de type 1 était de 2,7 % (3 patients). L’hypotonie a été remarquée en moyenne 13,7 mois après l’opération. Les patients avaient tous eu une uvéite et une vitréite précédant des décollements choroïdiens et rétiniens et requis des chirurgies vitréorétiniennes de réparation. Chez tous les patients, la fuite objective par l’interface de la cornée avec la plaque antérieure de la cornée de KPro a été examinée pendant l’opération par le chirurgien vitréorétinien. La moyenne de MAVC de ces patients s’est stabilisée à 20/300 après la résolution des complications, avec une moyenne de PIO de 10 mmHg. Conclusions : Une fuite adjacente à la tige du KPro peut se produire après plusieurs mois et mener à une importante perte de vision. La rapidité de la reconnaissance et celle de l’équipe de traitement s’imposent.
The Boston keratoprosthesis type 1 (KPro; Massachusetts Eye and Ear Infirmary, Boston, Mass.) has become a successful treatment for corneal blinding pathologies1; however, complications can occur. The purpose of this study is to report 3 cases who experienced a leak at the cornea–anterior front plate interface of the KPro leading to ocular hypotony.
METHODS In this retrospective, interventional case series, the medical records of 3 patients (3 eyes) who experienced From the *Department of Ophthalmology, Centre Hospitalier de l’Université de Montréal, Hôpital Notre-Dame; and †Department of Ophthalmology, Université de Montréal, Montréal, Que.
hypotony after Boston KPro type 1 surgery at the Centre Hospitalier de l’Université de Montréal (CHUM) were studied. Study approval was granted by the CHUM ethics committee. Informed consent was obtained from each patient for the collection and analysis of preoperative, intraoperative, and postoperative parameters. Preoperative assessment, operative protocol, and progress notes were reviewed with respect to patient demographics, ophthalmic diagnoses, preoperative and postoperative best corrected visual acuities (BCVAs), digital intraocular pressure (IOP), and postoperative complications. Hypotony and its related complications were Can J Ophthalmol 2014;49:106–108 0008-4182/14/$-see front matter & 2014 Canadian Ophthalmological Society. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jcjo.2013.08.005
Originally received Feb. 19, 2013. Final revision Aug. 4, 2013. Accepted Aug. 23, 2013 Correspondence to Kinda Najem, MD, Department of Ophthalmology, Centre Hospitalier de l’Université de Montréal, Hôpital Notre-Dame, 1560 Sherbrooke Street East, Montréal QC H2L 4M1; kinda.najem@ gmail.com
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CAN J OPHTHALMOL — VOL. 49, NO. 1, FEBRUARY 2014
Boston keratoprosthesis type 1 device leak—Najem et al. Table 1—Patient demographics: preoperative and postoperative clinical features Patient no.
Age, y Sex
Preoperative BCVA
Preoperative diagnosis in operated eye
Time to diagnosis of hypotony, mo
HSV keratitis, 2 failed PK, OAG, white cataract Aniridia, glaucoma, cataract Aniridia glaucoma 1 failed PK aphakia
12
1
53
M
LP
2
63
M
LP
3
71
M
CF
Postoperative complications Anterior uveitis, vitritis, hypotony, CD, funnel RRD, PVR, RPM, ERM, leak through KPro Anterior uveitis, vitritis, hypotony, CD, RRD, leak through KPro RPM and YAG membranotomy 3, hypotony, hemorrhagic CD, RRD, vitritis, ERM, hypotony, leak through KPro
18 11
BCVA after PPV
BCVA at last follow-up
20/150
HM
20/100
20/300
20/100
20/150
BCVA, best corrected visual acuity; PPV, pars plana vitrectomy; M, male; HSV, herpes simplex virus; PK, penetrating keratoplasty; OAG, open-angle glaucoma; CD, choroidal detachment; RRD, rhegmatogenous retinal detachment; RPM, retroprosthetic membrane; ERM, epiretinal membrane; KPro, Boston keratoprosthesis type 1; HM, hand motion; LP, light perception; CF, counting fingers; PVR, proliferative vitreoretinopathy.
studied, and time of occurrence of this complication postKPro implantation was noted.
RESULTS Patient demographics and preoperative and postoperative clinical features are summarized in Table 1. The incidence rate of leak after KPro type 1 implantation was 2.7%. All patients were men with a mean age of 62.3 years. Two had a preoperative diagnosis of aniridia, and 1 patient had a history of unsuccessful penetrating
keratoplasties secondary to herpes simplex virus (HSV) keratitis. Preoperative BCVA ranged from counting fingers to light perception and improved to a mean of 20/100 (range 20/100 to 20/150) postoperatively. Several postoperative complications, listed in Table 1, were noted. Although the first postoperative months were uneventful, a relentless inflammation, either as anterior uveitis and/or vitritis, persisted despite treatment with oral prednisone and corticosteroid drops. The patient with a history of HSV was treated preoperatively and postoperatively with prophylactic acyclovir. Posterior segment complications ensued in all cases. Hypotony was
Fig. 1 — Optical coherence tomography images of Patient 3 showing abnormal thinning around the Boston keratoprosthesis type 1 (KPro) stem. A, Three months after surgery: no thinning seen around the KPro stem. B, Six months after surgery: white arrow shows the abnormal thinning around the KPro stem. (Pictures taken at Ophthalmology Department, Hoˆpital NotreDame, Montreal, Que.) CAN J OPHTHALMOL — VOL. 49, NO. 1, FEBRUARY 2014
107
Boston keratoprosthesis type 1 device leak—Najem et al. diagnosed at a mean of 13.7 months postoperatively (range 11–18 months). Seidel test was negative on clinical examination. Digital IOP was approximately r5 mm Hg. All patients required pars plana vitrectomy (PPV) with silicone oil exchange for repair. In all patients, an objective leak through the cornea–anterior front plate interface of the KPro was seen intraoperatively by the vitreoretinal surgeon (M.S.) as fluid exiting the eye at the interface under an infusion pressure of 25 mm Hg. In 1 patient, the leak was no longer evident in the post-PPV period and IOP increased. In the second patient, a repeat KPro was required in the affected eye to stop the persistent leak. In the third patient, the persistent leak was repaired with glue. Mean BCVA in these patients stabilized at 20/300 (range 20/150 to hand motion) after the leak was repaired with a mean IOP of 10 mm Hg (range 5–15 mm Hg).
DISCUSSION In our study, all leaks were at the corneal–anterior front plate interface. Detection of a lower range of normal levels of IOP at an earlier stage in the postoperative follow-up may be hindered by the inaccuracy of digital palpation.2,3 Lower pressure may have been an ongoing process that was detected only when frank hypotony and further complications became apparent. All patients manifested chronic and unrelenting inflammation around the time hypotony was diagnosed. None of our patients had ciliary body membranes to explain their hypotony. The leak was confirmed in all patients during PPV. Although Seidel was checked, no leak was documented before PPV. However, it is well-known that once IOP is very low, the leak may stop or become imperceptible on examination. It is a fact that there is no biointegration between the Boston KPro and the surrounding corneal tissue. Hence this potential space between the 2 adjoining surfaces may allow leakage from the KPro stem–corneal interface. Garcia et al.4 showed evidence of subclinical levels of thinning and desiccation present as a gap between the KPro-donor cornea interface on optical coherence tomography (OCT) imagery in 2 patients. No evidence of leakage was demonstrated when mild pressures were applied on the device.4 In our study, 1 patient had abnormal corneal thinning on OCT images and could have been more susceptible to the infusion pressures of PPV, leading to a potential leak (Fig. 1). No anomalies of the corneal carrier or the device were found in the other 2 patients. Wound remodeling may play a role in corneal thinning, increasing the vulnerability of the stem–corneal
108
junction to leaks. The wound remodeling may be macroscopic as in Patient 3. This thinning may also be microscopic, hence delaying the diagnosis until more overt complications occur. In fact, in Patient 2, the leak became apparent only during PPV where the higher infusion pressure revealed the wound junction weakness. Recent studies reporting on hypotony after Boston keratoprosthesis5,6 suggest a possible association between hypotony and the presence of retroprosthetic membrane. Retroprosthetic membranes were present in Patients 1 and 3, and may have predisposed to the leak in these 2 cases as well. Finally, although Patients 2 and 3 have aniridia, aniridic fibrosis syndrome,7 by definition, was not diagnosed because intraocular inflammation was present and no membranes were found extending into the retina. In conclusion, a leak is possible and can lead to devastating visual consequences after KPro implantation. Chronic inflammation, retroprosthetic membranes, and consequent wound remodeling may be the main culprits explaining the leaks in our patients. Appropriate and timely management with glaucoma and retina specialists can restore or stabilize visual acuity. Lifelong follow-up is of utmost importance in KPro patients because blinding and severe complications can occur long after surgery.
Disclosure: The authors have no proprietary or commercial interest in any materials discussed in this article.
REFERENCES 1. Hicks CR, Fitton JH, Chirila TV, Crawford GJ, Constable IJ. Keratoprostheses: advancing toward a true artificial cornea. Surv Ophthalmol. 1997;42:175-89. 2. Banitt M. Evaluation and management of glaucoma after keratoprosthesis. Curr Opin Ophthalmol. 2011;22:133-6. 3. Chew HF, Ayres BD, Hammersmith KM, et al. Boston keratoprosthesis outcomes and complications. Cornea. 2009;28:989-96. 4. Garcia JP Jr, Ritterband DC, Buxton DF, De la Cruz J. Evaluation of the stability of Boston type I keratoprosthesis-donor cornea interface using anterior segment optical coherence tomography. Cornea. 2010;29:1031-5. 5. Dokey A, Ramulu PY, Utine CA, et al. Chronic hypotony associated with the Boston type I keratoprosthesis. Am J Ophthalmol. 2012;154:266-71. 6. Sivaraman KR, Hou JH, Allemann N, de la Cruz J, Cortina MS. Retroprosthetic membrane and risk of sterile keratolysis in patients with type I Boston keratoprosthesis. Am J Ophthalmol. 2013;155:814-22. 7. Tsai JH, Freeman JM, Chan CC, et al. A progressive anterior fibrosis syndrome in patients with postsurgical congenital aniridia. Am J Ophthalmol. 2005;140:1075-9.
CAN J OPHTHALMOL — VOL. 49, NO. 1, FEBRUARY 2014