Boston Keratoprosthesis Surgery Research Articles

Probing mechanisms and improving management of glaucoma following Boston keratoprosthesis surgery.

Corneal blindness is a leading cause of visual impairment worldwide. The most common treatment is to replace the diseased cornea with standard corneal transplantation. In eyes at high risk of graft failure, the Boston keratoprosthesis type 1 (KPro) can be used to restore vision and is currently the most frequently used artificial cornea in the world. However, glaucoma is a well-known complication of KPro surgery and is the most important threat to vision in KPro-implanted eyes. This chronic disease is influenced by elevated intraocular pressure (IOP) and damages the optic nerve, leading to progressive vision loss. In KPro patients, glaucoma is highly prevalent and extremely challenging to manage, yet its exact cause remains unknown.

Probing mechanisms and improving management of glaucoma following Boston keratoprosthesis surgery

Probing mechanisms and improving management of glaucoma following Boston keratoprosthesis surgery

Long-term results of Boston keratoprosthesis surgery in Polish patients

Abstract Introduction To evaluate the long-term (10 year) outcomes of Boston type 1 keratoprosthesis (BKPro; Massachusetts Eye and Ear Infirmary, Boston, MA) surgery performed in 6 Polish patients. Materials and Methods 6 eyes of 6 patients (1 female and 5 males; mean age 49,5±6,34 years) were qualified for the surgery. Indications for BKPro surgery in the study group included: corneal graft failure (3 patients), chemical ocular burns (2 patients), and post-herpetic keratitis vascularized leucoma (1 patient). Visual acuity, slit-lamp examination with ocular surface assessment, anterior segment optical coherence tomography (AS OCT), fundoscopy, and intraocular digital pressure measurement were performed at each visit. Results Retention of keratoprosthesis was achieved in all patients during the follow-up period. At last recorded visits VA≥0,2 was observed in 3 patients, LP in one patient and NLP in 2 patients. The complications which occurred in our case series were: glaucoma (4 patients preoperatively, 6 patients postoperatively), retroprosthetic membrane formation (1 patient), epimacular membrane formation (2 patients) and severe Meibomian Gland Dysfunction (3 patients). OCT analysis allowed imaging of anterior iris synechiae, AGV tube, protrusion of the BKPro and retroprosthetic membrane not visible on the slit lamp examination. Conclusions BKPro surgery should be considered as a surgery of choice in patients who have high risk of PK failure. OCT plays a role in anterior eye segment monitoring and detection of complications not visible on the slit lamp examination in the follow up period. Implementing the dry eye disease treatment should be recommended in all patients undergoing BKPro surgery.

Vision retention in early versus delayed glaucoma surgical intervention in patients with Boston Keratoprosthesis type 1.

ImportanceThe loss of vision following Boston Keratoprosthesis (BKPro) surgery due to glaucoma occurs at a high frequency as diagnosis and management of glaucoma after this procedure pose challenges.ObjectiveTo compare visual outcomes in patients undergoing Boston Keratoprosthesis surgery with and without prior or concurrent glaucoma surgery.Design, setting, and participantsThis is a retrospective, observational cohort study of patients who underwent Boston Type I Keratoprosthesis surgery. 19 eyes of 18 patients who had undergone BKPro and met the inclusion criteria were identified. Twelve eyes received BKPro with prior or concurrent glaucoma surgery (Group 1), and seven eyes were identified undergoing BKPro surgery without prior or concurrent glaucoma surgery (Group 2).Main outcomes and measuresMain outcome included best corrected visual acuity at each follow up.ResultsIn Group 1, mean best corrected visual acuity (BCVA) within a year of BKPro surgery was 20/100 (range 20/40 to Count Fingers (CF); n = 12) and mean BCVA at 1 year from BKPro surgery was 20/115 (range 20/30 to CF; n = 12). 7 out of 12 patients retained or had improved BCVA at 1 year follow up after BKPro implantation, and 5 out of 12 patients had mild BCVA worsening. In Group 2, the mean BCVA within a year of BKPro surgery was 20/140 (ranging from 20/25 to hand motion vision (HM); n = 7) and mean BCVA at 1 year from BKPro surgery was Count Fingers (range 20/60 to Light Perception (LP); n = 6). 4 out of 6 patients lost significant vision at one year after BKPro.Conclusions and relevanceBKPro patients with early glaucoma surgical intervention retained vision significantly better compared to patients with late or no intervention. Our preliminary findings support the recommendation for concurrent or pre-emptive glaucoma surgical intervention in patients undergoing BKPro implantation.

No Light Perception Outcomes Following Boston Keratoprosthesis Type 1 Surgery

To determine the incidence rate, principal causes, and clinical course of eyes developing no light perception (NLP) visual acuity (VA) following Boston Keratoprosthesis (B-KPro) type 1 surgery. Secondary objectives include determining the incidence rate, relative risk (RR), and survival probability with respect to NLP outcomes among eyes with congenital aniridia. Retrospective, interventional case series. All patients undergoing B-KPro type 1 surgery between October 2008 and June 2016 by a single surgeon at CHUM - Hôpital Notre-Dame. Records of patients having undergone B-KPro implantation were reviewed. Eyes with a final outcome of NLP were further reviewed to determine best recorded postoperative VA, time to NLP onset, clinical course, and principal cause. Descriptive statistics, incidence rates, Kaplan-Meier survival curves, and the RR of NLP outcomes among eyes with aniridia were determined. Statistical significance was defined as P < .05. Records of 119 patients were included, with an average follow-up of 49.1 ± 26.8months postoperatively. Nineteen eyes had a final outcome of NLP, representing 16.0%. The incidence rate of NLP was 0.04 cases per eye-year of follow-up. The most common principal causes were inoperable retinal detachment (n= 7, 36.8%), terminal glaucoma (n= 6, 31.6%), and carrier graft melt-related complications (n= 5, 26.3%). The RR of developing NLP among eyes with aniridia was 3.04 (P= .01). No light perception is a devastating but uncommon outcome of B-KPro surgery. Patients with aniridia seem to be at increased risk. In spite of all available medical and surgical interventions, some eyes may still suffer this outcome.

Periprosthetic Tissue Loss in Patients With Idiopathic Vitreous Inflammation After the Boston Keratoprosthesis.

Idiopathic vitritis is a poorly understood complication after Boston keratoprosthesis surgery with unclear etiology. We sought to determine whether an association exists between periprosthetic corneal tissue loss and the development of idiopathic vitritis in keratoprosthesis recipients. Thirteen Boston type I keratoprosthesis recipient eyes with a history of idiopathic vitritis and 34 type I keratoprosthesis recipient eyes with no history of idiopathic vitritis underwent anterior segment optical coherence tomography (AS-OCT) at a median time postoperatively of 2.4 years versus 1.9 years (range, 0.5-14.2 vs. 0.1-13.6 years), respectively. Areas of corneal graft tissue loss ("gaps") around the keratoprosthesis stem were identified and analyzed by 2 masked observers. The difference in the presence, number, and size of gaps was compared between cases and controls. A periprosthetic gap was identified more commonly in idiopathic vitritis cases than in controls on AS-OCT (11/13, 86% vs. 11/34, 33.3%, P < 0.001). The number of gaps between cases and controls was also significantly different (2.6 ± 1.6 vs. 0.5 ± 0.8, P < 0.001), but not the estimated gap area (0.056 ± 0.049 mm² vs. 0.039 ± 0.025 mm², P = 0.22). A significantly higher proportion of keratoprosthesis recipient eyes with idiopathic vitritis had corneal tissue loss around the keratoprosthesis stem than did controls. Tissue loss could serve as an entry point for debris or bacterial components, triggering idiopathic vitritis. Our study underscores the utility of AS-OCT imaging in the postoperative management of keratoprosthesis patients.

Collagen cross-linking of the Boston keratoprosthesis donor carrier to prevent corneal melting in high-risk patients.

To examine the clinical relevance and pathophysiology of Boston keratoprosthesis (B-KPro)-related corneal keratolysis (cornea melt) and to describe a novel method of preventing corneal melt using ex vivo crosslinked cornea tissue carrier. A review of B-KPro literature was performed to highlight cases of corneal melt. Studies examining the effect of corneal collagen cross-linking (CXL) on the biomechanical properties of corneal tissue are summarized. The use of crosslinked corneal tissue as a carrier to the B-KPro is illustrated with a case. Corneal melting after B-KPro is a relatively rare event, occurring in 3% of eyes during the first 3 years of postoperative follow-up. The risk of post-KPro corneal melting is heightened in eyes with chronic ocular surface inflammation such as eyes with Stevens-Johnson syndrome and mucous membrane pemphigoid. This chronic inflammation results in high tear levels of matrix metalloproteinases, the enzymes responsible for collagenolysis and corneal melt. Crosslinked corneal tissue has been shown to have stiffer biomechanical properties and to be more resistant to degradation by collagenolytic enzymes. We have previously optimized the technique for ex vivo corneal CXL and are currently studying its impact on the prevention of corneal melting after B-KPro surgery in high-risk eyes. Crosslinked carrier tissue was used in a 52-year-old man with familial aniridia and severe post-KPro corneal melt. The patient maintained his visual acuity and showed no evidence of corneal thinning or melt in the first postoperative year. Collagen crosslinking was previously shown to halt the enzymatic degradation of corneal buttons ex vivo. This study demonstrates the safety and potential benefit of using crosslinked corneal grafts as carriers for the B-KPro, especially in eyes at higher risk of postoperative melt.

Very Low Risk of Light-Induced Retinal Damage During Boston Keratoprosthesis Surgery

The aim of this study was to assess the possibility of light damage to the retina by a surgical microscope during implantation of a Boston Keratoprosthesis (B-KPro) in rabbits. The retinal irradiance from a Zeiss OPMI Lumera S7 operating microscope was measured at the working distance (16.5 cm). Light transmittance through an isolated B-KPro was measured. A B-KPro was implanted into 1 eye of 12 rabbits with the optic covered during the procedure. The operated eyes were then continuously exposed to a fixed light intensity under the microscope for 1 hour. Fluorescein angiography was carried out on days 2 and 9 postsurgery, after which the animals were euthanized. Further, we compared the potential of these retinal exposures to well-accepted light safety guidelines applicable to humans. Light transmittance of B-KPro revealed a blockage of short wavelengths (<390 nm) and of long wavelengths (1660-1750 nm) of light. In addition, the surgical microscope filtered a part of the blue, ultraviolet, and infrared wavelengths. Neither fluorescein angiography nor a histological examination showed any morphological retinal changes in our rabbits. Moreover, the retinal exposures were well below the safety limits. Modern surgical microscopes have filters incorporated in them that block the most damaging wavelengths of light. The B-KPro is made of 100% poly(methyl methacrylate), which makes it in itself a blocker of short wavelengths of light. No damage could be demonstrated in the animal study, and the retinal exposures were well below the safety limits. Together, these results suggest that light exposures during B-KPro surgery present a low risk of photochemical damage to the retina.

Very low risk of light‐induced retinal damage during Boston Keratoprosthesis surgery

AbstractPurpose To assess the possibility of light damage to the retina by a surgical microscope during implantation of a Boston Keratoprosthesis (B‐KPro) in rabbits.Methods The retinal irradiance from a Zeiss OPMI Lumera S7 operating microscope was measured at its working distance (16.5 cm). Light transmittance through an isolated B‐KPro (made of PMMA) was measured. A B‐KPro was implanted into one eye of each of 12 rabbits with the optic of the device initially covered during the procedure. Retinoscopy was performed after the implantation, and external additional lenses were used when needed to focus the light on the retina. The operated eyes were then continuously exposed to a fixed light intensity under the microscope for 1 hour. After the exposure, the rabbits were monitored for 9 days and fluorescein angiography (FA) was carried out at days 2 and 9.Results Light transmittance of the B‐KPro revealed blockage of short wavelengths (from 0.001% at 200nm to 42% at 390nm) and of long wavelengths (12‐35% at 1660‐1750nm). In addition, the surgical microscope blocked part of the blue, ultraviolet (UV), and infrared (IR) wavelengths of light. FA showed no leak of dye or other morphological changes. Histological examination with H&amp;E staining showed no morphological retinal changes.Conclusion Our results show that the PMMA of the B‐KPro has a very low transmittance of phototoxic wavelengths of light, mostly UV. In addition, modern surgical microscopes have filters for UV and IR wavelengths of the light spectrum. No morphologic damage to the retina from the light exposure from our microscope could be demonstrated. Thus, there should be very low risk of light damage to the retina during routine B‐KPro surgery.

Use of Trypan Blue Corneal Staining and Centration Ring in Boston Keratoprosthesis Surgery

Use of Trypan Blue Corneal Staining and Centration Ring in Boston Keratoprosthesis Surgery

Use of Trypan Blue Corneal Staining and Centration Ring in Boston Keratoprosthesis Surgery

Purpose: To describe the beneficial use of the John Centration Ring (ASICO, Inc, Westmont, Ill) and trypan blue (Vision Blue; Dutch Ophthalmic International, Exeter, NH) in Boston keratoprosthesis surgery. Surgical Technique: The donor cornea is stained with trypan blue and a central 3.0-mm opening is created using a 3.0-mm disposable trephine that is optimally centered using the John Centration Ring (ASICO, Inc). The donor cornea is then sandwiched between the 2 plates of the Boston keratoprosthesis and locked in place with a titanium ring. After host corneal excision, the assembled Boston keratoprosthesis unit is sutured in place to the recipient corneal rim. Conclusions: Use of the John Centration Ring (ASICO, Inc) greatly facilitates the proper centration of the Boston keratoprosthesis on to the donor cornea before the unit being sutured to the recipient corneal rim. Trypan blue staining of the donor cornea greatly enhances visibility, helps in uniform surface alignment of the donor corneal rim to the peripheral recipient corneal rim, and helps in the uniform suture placement in the donor cornea stained with trypan blue.

Infection control in KPros

Abstract Purpose: To study Boston KPro‐related infections. Methods: Retrospective review of case notes. Results: Since 1990, 350 patients have undergone Boston Keratoprosthesis surgery. An analysis has been made of those affected by bacterial or fungal infections. The results will be presented. Conclusions: Strategies to prevent and treat Boston KPro‐related ocular infections will be presented.