A New Approach of Aspheric Intralamellar Keratoprostheses Optic Design made with poly(2-hydroxy ethylmethacrylate) Hydrogel

Keratoprosthesis (KPro) is a surgical procedure largely confined to end-stage corneal blindness correction, where artificial cornea substitutes the native tissue. Though the problem of bio integration was addressed partially by strategic utilization of synthetic polymers and native tissue, major challenges like optical performance and design-associated post-operative complications of KPro were overlooked. Herein, a novel intralamellar KPro design is conceptualized to address these challenges using a light-transparent poly(2-hydroxy ethylmethacrylate) (pHEMA) hydrogel with good shape memory. pHEMA-based optics' theoretically modelled refractive surfaces for both phakic and aphakic conditions were investigated against the standard Navarro model and optimized to new aspheric geometries having high optical functionality utilizing the Zemax OpticStudio software. The optical clear aperture size standardized achieved a 15 % improvement in the illumination field. The introduction of asphericity on the two refractive surfaces of the optic on both models resulted in substantial improvements in the spot spread confinement on the retina, spatial resolution, and Seidel aberration. The design simulation study shows that the developed materials' optical characteristics coupled with newly optimized refractive surface geometries can indeed deliver very high visual performance. Furthermore, the procedure can be adapted to analyze and optimize the optical performance of a KPro, intraocular lens, or contact lens.

Artifacts in OCT Retinal Nerve Fiber Layer Imaging in Patients with Boston Keratoprosthesis Type 1

PURPOSE

To determine the clinical utility of OCT retinal nerve fiber layer (OCT RNFL) imaging for glaucoma evaluation in patients with Boston keratoprosthesis type 1 (KPro) by investigating imaging artifacts.

DESIGN

Case-control study.

SUBJECTS

Patients with KPro and without KPro (controls) matched for age, gender, and glaucoma diagnosis.

METHODS

The most recent Cirrus OCT RNFL scan from 1 eye was categorized as having good signal strength (SS; ≥ 6 out of 10) or poor SS (< 6). Those with good SS were analyzed by 2 independent reviewers for artifacts. Images with good SS and no artifacts affecting the scanning circle were considered useful for glaucoma evaluation.

MAIN OUTCOME MEASURES

The incidence of poor SS and artifacts in OCT RNFL images; patient characteristics associated with useful scans.

RESULTS

Sixty-five patients with KPro and 75 controls were included; 89.2% of KPro patients and 89.3% of control subjects had glaucoma (P = 0.98). Forty percent of KPro patients and 5.3% of controls had poor SS (P < 0.001). The proportion of images with either poor SS or artifacts was similar in KPro (76.9%) vs. controls (72.0%, P = 0.51). The most common artifacts in both groups were missing data (43.6%, 53.2%, respectively, P = 0.32) and motion artifact (25.6%, 19.7%, respectively, P = 0.47). Images were useful for glaucoma evaluation in 43.1% of KPro patients and in 69.3% of controls (P = 0.002). In the KPro group, patients with useful OCT scans, compared with those without, had better visual acuity (0.4 ± 0.3 vs. 0.9 ± 0.7 logarithm of the minimum angle of resolution, P = 0.004), and did not have congenital corneal pathologies (0.0% vs. 24.3%, P = 0.008). A multivariate analysis showed that KPro patients with older age had higher odds of useful OCT images (odds ratio, 1.05; P = 0.03). Among KPro patients with useful OCT scans, retinal nerve fiber layer thickness correlated with observed cup-to-disc ratio (Pearson correlation: r = -0.42, P = 0.03).

CONCLUSIONS

The rate of OCT RNFL images with either poor signal strength or artifacts in the KPro and control population was comparable. In patients with KPro, where intraocular pressure measurements are difficult and glaucoma is highly prevalent and often severe, OCT RNFL imaging can be useful for glaucoma evaluation.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Use of PROSE for long-term ocular surface support in patients with a permanent keratoprosthesis

Purpose

To describe the long-term outcome of the use of a specialized scleral lens known as a prosthetic replacement of the ocular surface ecosystem (PROSE) device to support the ocular surface in patients with a Boston Keratoprosthesis (KPro) Type I. All patients in this series were unable to pursue continuous wear of a bandage soft contact lens (BSCL) - a critical aspect of post KPro implantation management intended to protect the corneal carrier tissue from desiccation and stromal melting.

Observations

Four eyes of four patients with a Boston KPro Type I were included. All four had failed BSCL wear and were instead treated with PROSE device wear. All four patients had underlying diagnoses associated with a diseased ocular surface (Stevens-Johnson Syndrome [one patient], prior failed penetrating keratoplasty associated with herpes zoster-related neurotrophic keratopathy [one patient], and prior failed penetrating keratoplasty associated with severe dry eye disease [two patients]). Causes of failure of BSCL wear included poor retention, discomfort, and poor vision. PROSE device wear was initiated on average seven and a half (range four to 14) months post-KPro implantation. The wear schedule varied and ranged from waking-hour wear only to 24-h wear. The average duration of device wear was 59.3 (range 28-103) months. Two patients exhibited persistent corneal epithelial defect formation with waking-hour wear, which resolved within 10 days with 24-h device wear. All patients exhibited improvement in vision with PROSE compared to baseline, averaging six and a half (range six to eight) lines of improvement in Snellen acuity, and all patients reported increased comfort. There was no incidence of microbial keratitis, KPro device instability, or other complication throughout the duration of device wear.

Conclusions and Importance

This report offers a novel alternate approach to long-term support of the ocular surface in patients with a Boston KPro who fail standard continuous BSCL wear.

[Long-term visual outcomes of Boston type I keratoprosthesis in Canada]

BACKGROUND/PURPOSE

To evaluate long-term visual outcomes of Boston type I keratoprosthesis (KPro) surgery and identify risk factors for visual failure.

METHODS

Single surgeon retrospective cohort study including 85 eyes of 74 patients who underwent KPro implantation to treat severe ocular surface disease, including limbal stem cell deficiency, postinfectious keratitis, aniridia and chemical burns. Procedures were performed at the Centre hospitalier de l'Université de Montréal from October 2008 to May 2012. All patients with at least 5 years of follow-up were included in the analysis, including eyes with repeated KPro. Main outcome measures were visual acuity (VA), visual failure, defined as a sustained VA worse than the preoperative VA, postoperative complications, and device retention.

RESULTS

Mean follow-up was 7.2±1.3 years (±SD). Mean VA was 2.1±0.7 (logarithm of minimal angle resolution) preoperatively and 1.9±1.2 at last follow-up. In total, 2.4% of patients had VA better than 20/200 preoperatively vs. 36.5% at last follow-up. Maintenance of improved postoperative VA was seen in 61.8% of eyes at 7 years. Preoperative factors associated with visual failure were known history of glaucoma (HR=2.7 [1.2 to 5.9], P=0.02) and Stevens-Johnson syndrome (HR=7.3 [2.5 to 21.4], P<0.01). Cumulative 8-year complication rates were 38.8% retroprosthetic membrane formation, 25.9% hypotony, 23.5% new onset glaucoma, 17.6% retinal detachment, 8.2% device extrusion and 5.9% endophthalmitis. The majority (91.8%) of eyes retained the device 8 years after implantation.

CONCLUSION

Nearly two-thirds of patients exhibited improved VA 7 years after KPro implantation. Preoperative risk factors for visual failure were known glaucoma and Stevens-Johnson syndrome.

Successful use of conjunctival flaps to prolong survival of type I keratoprosthesis in severe bilateral chemical burns: two case reports

INTRODUCTION

This report describes the use of conjunctival flaps to enable the survival of type I keratoprosthesis (KPro) in two cases of bilateral severe total limbal stem cell deficiency (LSCD) following chemical burns.

PRESENTATION OF CASE

Two patients had a history of bilateral chemical injury with lime. On examination, the presenting vision was light perception to hand motions and both cases had conjunctivalized ocular surfaces with symblepharon. A modified technique of type I keratoprosthesis was used, where the conjunctivalized corneal pannus was dissected and lifted off as an inferior fornix-based conjunctival flap. This was followed by a standard surgical technique of type I KPro. The flap was then secured over the device and optical opening was made two weeks later. Both the patients had stable ocular surfaces with visual acuity of 20/20 at 2-7 years of follow-up.

DISCUSSION

In patients with total LSCD with adnexal involvement, type I KPro has unsatisfactory long-term survival because of the risk of repeated epithelial breakdowns and stromal ulceration. With the innovative approach described in this report, type I KPro can be successfully used for sustainable visual improvement in the presence of severe ocular surface disease and symblepharon.

CONCLUSION

Conjunctival flaps can be used along with type I KPros to improve long-term survival and give sustainable visual outcomes in cases of bilateral corneal blindness due to advanced ocular surface damage.

[Treatment of ocular mucous membrane pemphigoid]

Ocular mucous membrane pemphigoid is the manifestation of a systemic autoimmune disease. As autoantibodies circulating in the blood cannot be adequately treated by eye drops, systemic immunosuppressive treatment of this autoimmune disease naturally plays the most important role. Ophthalmic topical or even surgical procedures are only used as supportive measures or usually to control ocular complications that have developed. Patients with the typical clinical picture are treated causally with systemic immunosuppression causally, nurturing eye drops, as well as by minimally invasive surgery if complications arise, if possible in an inflammation-free state, in accordance with the guidelines if the diagnosis is positive but also if the biopsy and serology are repeatedly negative after exclusion of all differential diagnoses. Purely topical anti-inflammatory treatment is insufficient to prevent irreversible progression of scarring conjunctivitis. Corresponding treatment recommendations have been formulated in current European as well as German guidelines and are presented here as an overview.

Impact of keratoprosthesis implantation on retinal and visual pathway function assessed by electrophysiological testing

PURPOSE

To investigate the impact of Boston Type I Keratoprosthesis (BI-Kpro) implantation on retinal and visual pathway function, respectively, assessed by full-field electroretinography (ERG) and visually evoked potentials (VEPs).

METHODS

This is a prospective interventional longitudinal study, and patients with BI-Kpro implantation were assessed preoperatively and at 3 and 12 months after surgery. ERG, flash, and pattern-reversal VEPs (15' and 60' checks) along with visual acuity (VA) were performed.

RESULTS

A total of 13 patients (24 to 88 years of age) were included. Mean baseline VA (logMAR) improved from 2.30 to 1.04 at 3 months and to 1.00 at 12 months. Flash VEPs were normal in 6 (46%) patients and in 10 (77%) patients at the 12-month follow-up. PVEP was non-detectable in all patients preoperatively for both check sizes. For 15' check size, 6 (46%) patients showed responses after 3 and 12 months except for 1 patient with normal responses at 12 months with the remaining non-detectable. For 60' checks, 11 (85%) patients had responses 3 months after surgery with only 9 (70%) showing responses at 12 months. Abnormal full-field ERGs were found in all patients preoperatively. Amplitude improvement was found in 10 (77%) patients from baseline to 3 months and in 8 (62%) patients from the 3- to the 12-month follow-up.

CONCLUSIONS

In this small cohort of patients with BI-Kpro implantation, a remarkable improvement on visual function quantitatively assessed by electrophysiological testing was found in the majority of cases. Visual electrophysiological testing can contribute to objectively assess functional outcomes in this population.

3D biomaterial P scaffolds carrying umbilical cord mesenchymal stem cells improve biointegration of keratoprosthesis

Biointegration of a keratoprosthesis (KPro) is critical for the device stability and long-term retention. Biointegration of the KPro device and host tissue takes place between the surrounding corneal graft and the central optic [made by poly (methyl methacrylate) (PMMA)]. Our previous clinical results showed that auricular cartilage reinforcement is able to enhance the KPro biointegration. However, the auricular cartilage is non-renewable and difficult to acquire. In this study, we developed a novel type of biomaterial using a three-dimensional porous polyethylene glycol acrylate scaffold (3D biological P-scaffold) carrier with chondrocytes differentiated from induced human umbilical cord mesenchymal stem cells (hUC-MSCs) and tested in rabbit corneas. The results showed hUC-MSCs bear stem cell properties and coule be induced into chondrocytes, P-scaffold is beneficial to the growth and differentiation of hUC-MSCs both in vivo and in vitro. Besides, after implanting the P-scaffold into the corneal stroma, no serious immune rejection response, such as corneal ulcer or perforation were seen, suggested a good biocompatibility of P-scaffold with the corneal tissue. Moreover, after implanting P-scaffold in together with the differentiated chondrocytes into the rabbit corneal stroma, they significantly increased corneal thickness and strengthened the host cornea, and chondrocytes could stably persist inside the cornea. In summary, the 3D biological P-scaffold carrying differentiated hUC-MSCs could be the preferable material for KPro reinforcement.

Ocular Surface Preparation Before Keratoprosthesis Implantation

INTRODUCTION

This study aimed to evaluate the surgical treatment results for conjunctival limbal autograft (CLAU) and keratolimbal allograft (KLAL) in various types of limbal stem cell deficiency (LSCD) etiologies performed in order to achieve a stable ocular surface prior to KPro implantation.

METHODS

We analyzed the outcomes of the surgical treatment of 43 eyes of 39 patients with LSCD as an initial treatment preparing patients' ocular surface for KPro implantation. The most common causes were ocular trauma (50.7%), mainly alkali burns (77%); autoimmune causes, mainly ocular cicatricial pemphigoid (OCP; 17.4%); infection (15.9%) including Lyell's syndrome/Stevens-Johnson syndrome (LS/SJS; 16%). In all 17 eyes operated on with CLAU, this procedure was performed once. Similarly, one uncomplicated KLAL procedure in one eye was performed in 10 women and 19 men. In another one woman and three men, KLAL was performed in both eyes. In one man with Lyell's syndrome, the KLAL operation was performed three times in one eye. Follow-up was at least 12 months.

RESULTS

Visual acuity (VA) improved in 17 eyes (31%) and remained unchanged in 38 eyes (69%). VA improved from light perception to hand movements in three eyes (16%) from the CLAU group of patients and eight eyes (15%) from the KLAL group; VA improved from hand movements to finger counting in two eyes (12%) post CLAU and two eyes (4%) post KLAL operation. The most common complication of surgical treatment was persistent epithelial defect that was refractory to medical treatment in 32 eyes (58%), 5 eyes post CLAU and 27 post KLAL. Corneal conjunctivalization (19%) and neovascularization (29%) were present on the corneal edge of the graft. Symblephara recurred within 3 months in nine eyes (17.3%) after KLAL, including four eyes that had been chemically burned and five eyes with LS/SJS.

DISCUSSION

Pretreatment with CLAU or KLAL procedures in severely damaged ocular surfaces allows the ocular surface to be prepared for safe KPro implantation with sufficient tissue surroundings with less conjunctivalization and deeper conjunctival fornices.

Clinical study of laminar resorption: Part 2- outcomes, review and proposal for classification

PURPOSE

To analyze and review the clinical features and main outcomes of laminar resorption from the UK osteo-odonto-keratoprosthesis (OOKP) cohort.

METHODS

A retrospective review of case records was undertaken for patients who underwent keratoprostheses between 1996 and 2014 at the Sussex Eye Hospital, Brighton, UK. The main clinical outcomes of resorption, including its clinical signs, complications, treatments, and laminar survival, were evaluated.

RESULTS

Sixty-four patients (25-females, 39-males) were included, and in total, 74 laminae (3-tibial, 11-allografts, 60-autografts) were implanted. The age of the patients ranged from 20 to 91 years. Focal laminar thinning was the first sign of detectable resorption in 50% of autografts and 27% of allografts. All the tibial grafts and 55% of allografts presented with complications of resorption like endophthalmitis and aqueous leakage as the first signs of resorption. The survival of first implanted autografts was 82.4%(±6.3%) at 18 years, which was enhanced to 91.5%(±5.0%) by prophylactic exchanges of critically resorbed laminae with new laminae. Visual acuity survival analysis did not reveal a statistically significant difference between grafts with and without resorption for all graft types (p = 0.825). Patients treated with Alendronic acid and acetazolamide demonstrated trends toward the slower progression of resorption, but this was not statistically significant.

CONCLUSIONS

Focal laminar thinning was the common presenting feature of resorption in autografts. Timely replacement of the resorbed laminae with new laminae should be considered to avoid complications. Alendronic acid supplementation may be considered in high-risk cases of resorption to reduce further progression.

Corneal transplantation outcomes after the extrusion of an intrastromal keratoprosthesis: a pilot study

This short report includes 5 eyes of 5 patients (mean age 63.2 ± 12 years) who underwent a tectonic keratoplasty [deep anterior lamellar keratoplasty (DALK) or penetrating keratoplasty (PK)] in order to rehabilitate the eye after the extrusion of the non-perforating keratoprosthesis (Kpro) KeraKlear (KeraMed, USA). The non-perforating Kpro was extruded after a mean period of 21.4 ± 21.8 months due to melting. In two cases, the keratoplasty was performed the same day of the non-perforating Kpro removal due to a severe melting, while in the other three cases it was performed one to 3 months later. Two eyes received a DALK, but in 3 eyes a macroscopic Descemet membrane perforation forced the conversion into a PK. The mean follow-up period after the keratoplasty was 16.8 ± 6.6 months. No cases of rejection were recorded. All the 5 eyes achieved “anatomical success” (transparent graft, with no signs of infection or inflammation). Two eyes showed limited “functional success” because the achievement of the best visual potential was prevented by the development of glaucomatous optic atrophy during the follow-up period. In conclusion, this short report presents an unexpected success of a keratoplasty performed with a tectonic purpose after the extrusion of the non-perforating Kpro because the corneal graft remained transparent, without neovascularization or scarring during the follow-up period. This initial evidence shows some encouraging results regarding graft survival rate and the achievement of a useful visual rehabilitation with keratoplasty after a non-perforating Kpro failure instead of repeating the Kpro implantation.

Simultaneous Vitreoretinal Surgery and Penetrating Keratoplasty without a Keratoprosthesis or Endoscopy for Vitreoretinal Disease Associated with Corneal Opacity

We evaluated the visual outcome of combined penetrating keratoplasty (PKP) and 25G pars plana vitrectomy (PPV) performed without a temporary keratoprosthesis or endoscopy in a patient with vitreoretinal disease complicated by severe corneal opacity. The patient was a 68-year-old woman who had severe corneal opacity and silicone oil in her left eye after several previous intraocular surgeries for rhegmatogenous retinal detachment and proliferative vitreoretinopathy. We successfully performed a combined surgery of conventional PKP followed by 25G PPV without the use of a keratoprosthesis. At 6 months after surgery, visual acuity had not improved, and the density of corneal endothelial cells of the donor cornea had declined from 3,205 to 1,969 cells/mm². However, corneal transparency remained good, and additional surgery for vitreoretinal disease was not necessary. The combined surgical procedure designed to minimize the number of open-sky steps and to limit vitreoretinal complications thus proved to be safe and achieved stable corneal clarity in a patient with vitreoretinal disease and severe corneal opacity.

Surface modification of corneal prosthesis with nano-hydroxyapatite to enhance in vivo biointegration

The majority of clinical corneal prostheses (KPros) adopt a core-skirt configuration. This configuration is favored owing to the optic core (generally a cylindrical, acrylic-based material, such as PMMA), that not only provides a clear window for the patients' vision, but also confers resistance to biodegradability. The surrounding skirt (typically a biological material, such as corneal tissue) allows for host tissue integration. However, due to poor biointegration between the dissimilar core and skirt materials, it results in a weak adhesion at the interface, giving rise to clinical complications, such as bacterial infections in the tissue-PMMA interface and device extrusion. Here, we physically immobilized nano-hydroxyapatite (nHAp) on a PMMA cylinder via a dip-coating technique, to create a bioactive surface that improved biointegration in vivo. We established that the nHAp coating was safe and stable in the rabbit cornea over five weeks. More importantly, we found that apoptotic, wound healing and inflammatory responses to nHAp-coated PMMA were substantially milder than to non-coated PMMA. More mature collagen, similar to the non-operated cornea, was maintained in the corneal stroma adjacent to the nHAp-coated implant edge. However, around the non-coated cylinder, an abundant new and loose connective tissue formed, similar to bone tissue response to bioinert scaffolds. As a result of superior biointegration, tissue adhesion with nHAp-coated PMMA cylinders was also significantly enhanced compared to non-coated cylinders. This study set a precedent for the future application of the nHAp coating on clinical KPros. STATEMENT OF SIGNIFICANCE: Currently, all clinical corneal prostheses utilize as-manufactured, non-surface modified PMMA optic cylinder. The bioinert cylinder, however, has poor biointegration and adhesion with the surrounding biological tissue, which can give rise to postoperative complications, such as microbial invasion in the tissue-PMMA loose interface and PMMA optic cylinder extrusion. In the current study, we showed that surface modification of the PMMA cylinder with bioactive nano-hydroxyapatite (nHAp) significantly enhanced its biointegration with corneal stromal tissue in vivo. The superior biointegration of the nHAp-coated PMMA was signified by a more attenuated corneal wound healing, inflammatory and fibrotic response, and better tissue apposition, as well as a significantly improved corneal stromal tissue adhesion when compared to the non-coated PMMA.

The Osteo-odonto-keratoprosthesis to restore vision after severe dog bite injury

Purpose

To present our experience in Osteo-odonto-keratoprosthesis (OOKP) as the only option to restore vision after severe ocular dog bite injuries.

Methods

We describe our results in OOKP performed in two patients with previous severe dog bite facial injuries that required exenteration of one eye and facial reconstruction.

Results

Both cases achieved initially successful anatomical and visual outcome; however, one case suffered retinal detachment after one year. Buccal mucosa (BM) ulcerations and tilted lamina were present as a result of extraocular muscles loss, and both were difficult to treat.

Conclusion

OOKP has the capability to restore vision in the most challenging cases of ocular trauma; however, refractory BM ulcerations and tilted lamina could be expected as a result of an ischemic ocular surface and orbital pulleys loss.

Histopathologic Evaluation of Polymer Supports for Pintucci-type Keratoprostheses: An Animal Study

Purpose

To report histopathological findings for different types of polymers proposed as support for a Pintucci-type keratoprosthesis.

Methods

Six polymers, including three types of polyesters (#1-3), one type of polytetrafluoroethylene (PTFE, #4), polyethylene (#5), and expanded polytetrafluoroethylene (ePTFE, #6) were evaluated. Four samples of each material were placed under the orbicularis oculi muscles of 12 rabbits. After five weeks, the samples were removed and evaluated histopathologically. Fibrovascular tissue ingrowths were investigated in terms of tissue penetration depth into the materials (graded as none, mild, moderate, and intense) and fibrovascular ingrowth area at the ultimate level of tissue penetrance. ImageJ software was used to calculate fibrovascular tissue area between the material fibers, and the mean area values were compared between the materials.

Results

Polyester materials #1 and #3 demonstrated intense fibrovascular tissue penetration with a large fibrovascular ingrowth area; no overt tissue ingrowth was observed into material #6. The mean area of penetrated fibrovascular tissues was significantly different between materials (P < 0.001). Materials #2, #4, and #5 showed moderate fibrovascular tissue ingrowth and the area of presented fibrovascular tissue at the paracentral parts of material #4 was significantly smaller than that of materials #1 (P = 0.02) and #3 (P = 0.01).

Conclusion

Two polyester materials that had relatively large pore sizes demonstrated a deep and large area of fibrovascular ingrowth. Given that material #3 is thicker and more consistent than material #1, the former can be used as the appropriate material for supporting the Pintucci-type keratoprosthesis.

Management of dislocated nucleus with corneal opacity by combined deep anterior lamellar keratoplasty, pars- plana vitrectomy and phaco-fragmentation

A 32-year-old man presented with bilateral diminution of vision for 10 years. Visual acuity was light perception in both eyes with inaccurate projection in the oculus dextrus(OD) and accurate projection in the in oculus sinister (OS). Intraocular pressure was 6 and 12 mm Hg in the OD and OS, respectively. Slit-lamp examination revealed the presence of leucomatous corneal opacification with microcornea in oculus uterque (OU). Both eyes had a dislocated nucleus in the vitreous cavity on ultrasound B-scan with advanced cupping in the right eye. Ultrasound biomicroscopy revealed ciliary body atrophy in the OD and preserved ciliary processes (two quadrants) in the OS. In view of a partially preserved ciliary body function and a potential for gaining useful vision, we planned surgical intervention in the left eye. Deep anterior lamellar keratoplasty with pars planavitrectomy (PPV) and phacofragmentation of the nucleus was done. Donor lamellar graft was sutured after completion of PPV and nucleus fragmentation. The patient regained useful ambulatory vision postoperatively with clear corneal graft.

Nd:YAG Laser for Ahmed Tube Shunt Blockage in Patients Implanted with Boston Type I Keratoprosthesis

Introduction

The purpose of this study was to describe the results using the Nd:YAG laser to reopen blocked glaucoma tube shunts in three ocular chemical burn patients with Boston keratoprostesis type I (KPro) implantation.

Methods

The medical records of the three patients at Zhongshan Ophthalmic Centre were reviewed.

Results

Patient 1, who had glaucoma secondary to KPro implantation, had undergone Ahmed glaucoma valve (AGV) implantation to control an elevated intraocular pressure (IOP). One day after surgery, the tube was observed to be embedded in the residual lens capsule. The capsule was opened by one 1.5 mJ laser pulse, with a subsequent drop in the IOP. In patient 2, the AGV and KPro had been implanted simultaneously. One month after surgery, the IOP increased to 35 mmHg, estimated by palpation, and a vitreous gel was seen blocking the tube. A Nd:YAG laser pulse was used to open the occluded tube. In patient 3, the tube was blocked by iris tissue; Nd:YAG laser treatment opened the tube.

Conclusions

The cases described here indicate that Nd:YAG laser treatment seems to be a valuable option for opening an occluded AGV tube in patients with KPro implantation. The correct location of the tube tip, visualized through the KPro optic, is essential for laser treatment.

Electronic supplementary material

The online version of this article (10.1007/s40123-019-0186-6) contains supplementary material, which is available to authorized users.

Vision Rehabilitation with a Native Pintucci-type Keratoprosthesis

Purpose

To report visual rehabilitation with a native Pintucci keratoprosthesis (KPro) after a severe ocular surface chemical burn in a male patient.

Case Report

A 41-year-old man experienced a bilateral severe chemical burn 5 years previously. Earlier penetrating keratoplasty and keratolimbal allografts were unsuccessful in both eyes, and neither of the eyes had vision better than light perception. Both corneas were opaque and conjunctivalized. Because of severe dry eye and total limbal stem cell deficiency, the left eye was considered for a Pintucci-type KPro. In the first stage, the ocular surface was reconstructed with an oral mucus membrane graft, and a KPro was placed under the skin and orbicularis oculi muscle. Three months later, the KPro was removed and implanted in the left eye. During seven months after the KPro implantation, the anatomical position was acceptable, and his best corrected visual acuity was 2/10.

Conclusion

Bearing in mind the successful results of the native Pintucci KPro in this case of severe acid burn, using this type of keratoprosthesis in patients with total limbal stem cell deficiency and severe dry eye is recommended.

Detection of laminar resorption in osteo-odonto-keratoprostheses

PURPOSE

To compare the clinical examination and computerized tomography (CT) scanning methods for the detection of laminar resorption in eyes with osteo-odonto-keratoprosthesis (OOKP).

METHODS

Patients who developed laminar resorption after OOKP surgery and had at least one CT scan of the lamina during the follow-up were included. Case records and CT images and reports were retrospectively reviewed. Each lamina of the eye was regarded as a case. The imaging and clinical data were collected in Microsoft Excel, and statistical analysis was performed on Stata-v14. The agreements and sensitivities of both the methods were compared.

RESULTS

Forty patients out of 64 were found to have laminar resorption. A total of 48 laminae were studied, which had data on the presence or absence of resorption. The sensitivity and specificity of clinical detection of resorption were 87.5% (CI 68%-97%) and 37.5% (CI 8.5%-75.5%), respectively. Whereas, the sensitivity and specificity of CT scan were 81% (CI 61%-93%) and 50% (CI12%-88%), respectively. Both the methods have detected resorption in 21 out of 32 laminae having both the clinical and CT scan data. There is a fair agreement between the two techniques in the identification of thinned laminar sites.

CONCLUSIONS

Clinical detection of laminar resorption in OOKP eyes is equally sensitive to the CT scanning. Resorption can be detected even in its early stages by clinical palpation in experienced hands. Frequent CT scanning is not indicated to detect laminar resorption. Both methods complement each other. Thinned laminar segments should be compared and correlated with both the methods for full evaluation of resorption.

[The Boston keratoprosthesis in the management of corneal blindness: Indications and limitations]

INTRODUCTION

Keratoprostheses offer a therapeutic alternative to patients with bilateral corneal blindness who cannot undergo corneal allograft. The goal of this work was to evaluate the indications and limitations of Boston keratoprosthesis.

MATERIALS AND METHODS

Seven patients underwent unilateral implantation of a Boston type I keratoprosthesis between December 2012 and November 2016. The following data were collected: surgical indication, preoperative visual acuity, postoperative visual acuity at D1, D7, D30, 6 months and 12 months, complications and postoperative treatment.

RESULTS

The mean age of implantation was 58.7±23.4 years. The surgical indications included 1 case of congenital bilateral aniridia, 2 cases of chemical burn and 4 graft decompensations after multiple keratoplasties. Preoperative visual acuity was limited to "light perception" in 6 cases and "hand motion" in one case. A gain in visual acuity was observed in 4 patients, which corresponded to a mean gain of 1.53 logMAR at last follow-up. Postoperative visual acuity averaged 2.33 logMAR. All patients experienced an improvement in their quality of life and independence.

DISCUSSION

Patients should be selected carefully, favoring patients with a remaining functional potential and able to engage in close postoperative follow-up, in order to ensure the best possible treatment success.

CONCLUSION

Boston keratoprosthesis provides improved vision and improved quality of life for patients suffering from bilateral corneal blindness.

Boston keratoprosthesis type 1 for limbal stem cell deficiency after severe chemical corneal injury: A systematic review

PURPOSE

To systematically review the published literature on outcomes of Boston keratoprosthesis type 1 for the treatment of limbal stem cell deficiency secondary to severe chemical corneal injury.

METHODS

Literature searches were conducted in MEDLINE (Ovid), Embase, Web of Science, and the Cochrane Central Register. The main outcome measures assessed were the proportion of eyes with best-corrected visual acuity (BCVA) ≥ 20/200 and the proportion retaining their original keratoprosthesis, both at the last recorded visit.

RESULTS

We identified 9 reports in which outcomes of Boston keratoprosthesis type I implantation after severe chemical injury could be determined, encompassing a total of 106 eyes of 100 patients. There were no randomized controlled studies. The median pre-operative BCVA was hand motion. Vision improved to ≥20/200 in 99/106 (93.4%) eyes after implantation. With a mean follow-up of 24.99 ± 14 months, 68/106 (64.1%) eyes retained BCVA ≥ 20/200 at the last examination. Therefore, 68/99 (68.7%) of those who improved to > 20/200 maintained at least this acuity. The originally implanted device was retained in 88/99 (88.9%) recipients for whom retention was reported. The mean time to failure was 22.36 ± 17.2 months. Glaucomatous optic neuropathy was the most common cause for BCVA <20/200 in eyes that retained the keratoprosthesis (18/27, 66.7%)..

CONCLUSIONS

Implantation of a Boston keratoprosthesis type I in eyes with corneal blindness after severe chemical ocular injury leads to functional vision in the majority of recipients. Evidence was limited by variability in outcome reporting and an absence of controlled studies..

Evaluation of stability and biocompatibility of PHEMA-PMMA keratoprosthesis by penetrating keratoplasty in rabbits

Artificial corneas have been developed as an alternative to natural donor tissue to replace damaged or diseased corneas. This study was conducted to evaluate the stability and biocompatibility of PHEMA-PMMA [poly (2-hydroxyl methacrylate)-poly (methyl methacrylate)] keratoprostheses in rabbits following penetrating keratoplasty. Sixteen male New Zealand White rabbits aged 16 weeks were divided into three groups. Group I and group II contained six rabbits each, while the control group had four rabbits. Experimental surgery was conducted under general anesthesia. The cornea was penetrated using an 8 mm diameter biopsy punch. In group I (core 5 mm & skirt 3 mm) and group II (core 6 mm & skirt 2 mm), the keratoprosthesis was placed into the recipient full thickness bed and sutured into position with double-layer continuous. In the control group, corneal transplantation using normal allogenic corneal tissue was performed with the same suture method. After four and eight weeks, keratoprosthesis devices were evaluated by histopathological analysis of gross lesions. Post-operative complications were observed, such as extrusion and infection in experimental groups. Most corneas were maintained in the defect site by double-layer continuous suture materials for 4 weeks and kept good light transmission. However, most artificial cornea were extruded before 8 weeks. Overall, combined PHEMA and PMMA appears to have sufficient advantages for production of artificial corneas because of its optical transparency, flexibility and other mechanical features. However, the stability and biocompatibility were not sufficient to enable application in humans and animals at the present time using penetrating keratoplasty. Further studies are essential to improve the stability and biocompatibility with or without other types of keratoplasty.

Publication trends in corneal transplantation: a bibliometric analysis

Background

Our aim was to demonstrate the publication trends of corneal transplantation in the last decade.

Methods

All of the keratoplasty research articles, letters, case reports, reviews and meeting abstracts published between January 2006 and December 2015 indexed on the Thomson Reuters Web of Knowledge were evaluated. A bibliometric filter was used to capture keratoplasty related publications by using the key words ‘keratoplasty’, ‘corneal transplantation’ or ‘keratoprosthesis’ in the ‘title’ selection mode.

Results

A total of 2726 publications were evaluated in the present study. Documents related to penetrating keratoplasty only have been decreased, whereas the documents related to endothelial keratoplasty were increased in the last decade. The total keratoplasty publication counts had been increased from the year 2006 to 2015. The average citation count per keratoplasty documents was 9.34.

Conclusions

There is a growing interest to the lamellar keratoplasty techniques especially the endothelial keratoplasty in the last decade.

Erratum to: 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 45 eyes that received a B-K-Pro type 1 between 2009 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 11.1 % (5 of 45 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 from patient selection through postoperative management: a review for the keratoprosthetic surgeon

For the anterior segment surgeon, the implantation of Boston type 1 keratoprosthesis is a multistep process that begins with careful patient selection. Success depends on thorough preoperative evaluation, detailed surgical planning, and frequent postoperative follow-up. New practice patterns have emerged for each of these phases as the international experience with keratoprosthesis grows. This review details special considerations that can improve outcomes and also allow surgeons to consider its use in challenging patient populations at each step.

High-risk corneal allografts: A therapeutic challenge

Corneal transplantation is the most common surgical procedure amongst solid organ transplants with a high survival rate of 86% at 1-year post-grafting. This high success rate has been attributed to the immune privilege of the eye. However, mechanisms originally thought to promote immune privilege, such as the lack of antigen presenting cells and vessels in the cornea, are challenged by recent studies. Nevertheless, the immunological and physiological features of the cornea promoting a relatively weak alloimmune response is likely responsible for the high survival rate in “low-risk” settings. Furthermore, although corneal graft survival in “low-risk” recipients is favourable, the prognosis in “high-risk” recipients for corneal graft is poor. In “high-risk” grafts, the process of indirect allorecognition is accelerated by the enhanced innate and adaptive immune responses due to pre-existing inflammation and neovascularization of the host bed. This leads to the irreversible rejection of the allograft and ultimately graft failure. Many therapeutic measures are being tested in pre-clinical and clinical studies to counter the immunological challenge of “high-risk” recipients. Despite the prevailing dogma, recent data suggest that tissue matching together with use of systemic immunosuppression may increase the likelihood of graft acceptance in “high-risk” recipients. However, immunosuppressive drugs are accompanied with intolerance/side effects and toxicity, and therefore, novel cell-based therapies are in development which target host immune cells and restore immune homeostasis without significant side effect of treatment. In addition, developments in regenerative medicine may be able to solve both important short comings of allotransplantation: (1) graft rejection and ultimate graft failure; and (2) the lack of suitable donor corneas. The advances in technology and research indicate that wider therapeutic choices for patients may be available to address the worldwide problem of corneal blindness in both “low-risk” and “high-risk” hosts.

Biocompatibility of a fish scale-derived artificial cornea: Cytotoxicity, cellular adhesion and phenotype, and in vivo immunogenicity

PURPOSE

To determine whether a fish scale-derived collagen matrix (FSCM) meets the basic criteria to serve as an artificial cornea, as determined with in vitro and in vivo tests.

METHODS

Primary corneal epithelial and stromal cells were obtained from human donor corneas and used to examine the (in)direct cytotoxicity effects of the scaffold. Cytotoxicity was assessed by an MTT assay, while cellular proliferation, corneal cell phenotype and adhesion markers were assessed using an EdU-assay and immunofluorescence. For in vivo-testing, FSCMs were implanted subcutaneously in rats. Ologen(®) Collagen Matrices were used as controls. A second implant was implanted as an immunological challenge. The FSCM was implanted in a corneal pocket of seven New Zealand White rabbits, and compared to sham surgery.

RESULTS

The FSCM was used as a scaffold to grow corneal epithelial and stromal cells, and displayed no cytotoxicity to these cells. Corneal epithelial cells displayed their normal phenotypical markers (CK3/12 and E-cadherin), as well as cell-matrix adhesion molecules: integrin-α6 and β4, laminin 332, and hemi-desmosomes. Corneal stromal cells similarly expressed adhesion molecules (integrin-α6 and β1). A subcutaneous implant of the FSCM in rats did not induce inflammation or sensitization; the response was comparable to the response against the Ologen(®) Collagen Matrix. Implantation of the FSCM in a corneal stromal pocket in rabbits led to a transparent cornea, healthy epithelium, and, on histology, hardly any infiltrating immune cells.

CONCLUSION

The FSCM allows excellent cell growth, is not immunogenic and is well-tolerated in the cornea, and thus meets the basic criteria to serve as a scaffold to reconstitute the cornea.

Boston type 1 keratoprosthesis for failed keratoplasty

The purpose of this study was to evaluate the outcomes of the Boston type 1 keratoprosthesis (Kpro-1) in eyes with failed keratoplasty. A retrospective review was performed of every patient treated with a Kpro-1 at a tertiary eye care center between January 1, 2008 and July 1, 2013. Eyes with a failed keratoplasty originally performed for corneal edema, trauma, or keratoconus were included in the statistical analysis. The main outcome measures were visual outcome, prosthesis retention, and postoperative complications. Twenty-four eyes met the inclusion criteria, including 13 eyes with corneal edema, 8 eyes with trauma, and 3 eyes with keratoconus. After a mean follow-up period of 28.9 months (range 7-63 months), the median best corrected visual acuity (BCVA) was 20/125. The BCVA was ≥ 20/40 in 4 (16.7 %) eyes, ≥ 20/70 in 9 (37.5 %) eyes, and ≥ 20/200 in 14 (58.3 %) eyes. Overall, the postoperative BCVA improved in 17 (70.9 %) eyes, was unchanged in 3 (12.5 %) eyes, and was worse in 4 (16.7 %) eyes. The initial Kpro-1 was retained in 22 (91.7 %) eyes, and was successfully repeated in the other 2 eyes. One or more serious prosthesis- or sight-threatening complications occurred in 8 (33.3 %) eyes. These included 1 case of wound dehiscence leading to prosthesis extrusion, 1 case of fungal keratitis leading to prosthesis extrusion, 4 cases of endophthalmitis, and 5 retinal detachments. The Boston Kpro-1 is associated with an excellent prognosis for prosthesis retention and satisfactory visual improvement in eyes with previous failed keratoplasty.

Outcomes of the Boston keratoprosthesis in jordan

Purpose:

To report the indications, outcomes, and complications of the Boston type I keratoprosthesis (KPro) from the first Jordanian study on the subject.

Materials and Methods:

A retrospective chart review was conducted on 20 eyes of 19 consecutive patients who had Boston type I KPro implantation at King Abdullah University Hospital. Surgeries were performed by the same surgeon (WS) from November 2007 to March 2010. Data collected included age, sex, primary indication, number of previous grafts, preoperative comorbidities, visual acuity before and after surgery, and complications.

Results:

The mean age of the participants was 51.7±19.9 years (range: 10–80 years). The mean follow-up was 18.1±9.5 months (range: 3–6 months). The most common primary corneal pathology was vascularized corneal opacity (40%). Best corrected visual acuity (BCVA) improved significantly in 85% of eyes; 65% had a BCVA of 20/200 or better and 25% had a BCVA of 20/50 or better. The most frequent complication was retroprosthesis membrane (RPM) formation, which occurred in 45% of eyes. Two eyes (10%) had implant extrusion and required further surgery.

Conclusion:

Boston Kpro offers a reasonably safe and effective solution for patients with corneal blindness in whom the prognosis for natural corneal grafting is poor.