Outcomes of the Boston type 1 and the Aurolab keratoprosthesis in eyes with limbal stem cell deficiency

Boston Keratoprosthesis type 1 (KPro) without contact lens wearing in end-stage corneal disease: The APEC experience

PURPOSE

To report the visual outcomes and survival analysis of keratoprosthesis without contact lens wearing in a tertiary eye care hospital in Mexico City, Asociación Para Evitar La Ceguera (APEC, Coyoacán, México).

DESIGN

Retrospective cohort with survival analysis.

PARTICIPANTS

Twenty-three eyes (22 patients) received KPro type 1 between 2015 and 2020 with a follow-up time of three years.

METHODS

We included analyzed data about past medical history, preoperative diagnosis, best-spectacle visual acuity (BSCVA), postoperative complications and retention rate. Univariate, bivariate and survival analysis were performed and reported.

RESULTS

The mean age was 58 ± 13.5 years (SD). 60.86% were male patients (14 eyes). Twelve-eyes (52%) achieved a BSCVA of 20/200 or better in the first and second year of follow-up. At 3 years, only 35% achieved 20/200 or better (BSCVA). Retention rate of Boston type 1 KPro was 87% (20 eyes) at 3 years follow-up. The most common complication was retroprosthetic membrane (RPM) which occurred in 9 eyes (39.1%), followed by corneal melting in 7 eyes (30.4%).

CONCLUSIONS

We report the results of a retrospective cohort of twenty-three eyes (22 patients) who were implanted with a Boston type 1 KPro without contact lens wearing to treat corneal blindness. BSCVA improved significantly in most patients achieving 20/200 or better at the 2-year follow-up. Retention rate was 87%, with the presence of RPM as the most common complication.

Corneal blindness in the developing world: The role of prevention strategies

Corneal blindness is an important contributor to the burden of global blindness and has a greater prevalence in low-income countries of the developing world where resources and infrastructure are limited. The causes of corneal blindness too are different from high-income countries and include infectious keratitis, ocular trauma, and xerophthalmia. Persons with these indications tend to have unfavourable outcomes after corneal transplantation, limiting their chances of benefitting from this sight-saving procedure. However, most causes of corneal blindness in the developing world are preventable. This highlights the importance of understanding the unique challenges in these regions and the need for targeted interventions. This article discusses various prevention strategies, including primordial, primary, and secondary prevention, aimed at reducing the burden of corneal blindness in low-income countries. These include capacity building, training, and awareness campaigns to reduce the risk factors of ocular trauma, infectious keratitis, and to improve access to first aid. It is also important to promote safe eye practices and tackle nutritional deficiencies through public health interventions and policy changes. Providing the required training to general ophthalmologists in the management of basic corneal surgeries and diseases and enhancing the accessibility of eye care services in rural areas will ensure early treatment and prevent sequelae. Current treatment modalities belong to the tertiary level of prevention and are largely limited to corneal transplantation. In developing nations, there is a scarcity of donor corneal tissue necessitating an urgent expansion of eye banking services. Alternative approaches to corneal transplantation such as 3D printed corneas, cultured stem cells, and biomaterials should also be explored to meet this demand. Thus, there is a need for collaborative efforts between healthcare professionals, policymakers, and communities to implement effective prevention strategies and reduce the prevalence of corneal blindness in the developing world.

Keratoprosthesis in dry eye disease

Bilateral corneal blindness with severe dry eye disease (DED), total limbal stem cell deficiency with underlying corneal stromal scarring and vascularization, combined with adnexal complications secondary to chronic cicatrizing conjunctivitis is a highly complex situation to treat. In such eyes, procedures such as penetrating keratoplasty alone or combined with limbal stem cell transplantation are doomed to fail. In these eyes, keratoprosthesis (Kpro) or an artificial cornea is the most viable option, eliminating corneal blindness even in eyes with autoimmune disorders such as Stevens-Johnson syndrome, ocular mucous membrane pemphigoid, Sjogren's syndrome, and nonautoimmune disorders such as chemical/thermal ocular burns, all of which are complex pathologies. Performing a Kpro in these eyes also eliminates the need for systemic immunosuppression and may provide relatively early visual recovery. In such eyes, the donor cornea around the central cylinder of the Kpro needs to be covered with a second layer of protection to avoid desiccation and progressive stromal melt of the underlying cornea, which is a common complication in eyes with severe DED. In this review, we will focus on Kpro designs that have been developed to survive in eyes with the hostile environment of severe DED. Their outcomes in such eyes will be discussed.

A Review of the Diagnosis and Treatment of Limbal Stem Cell Deficiency

Limbal stem cell deficiency (LSCD) can cause significant corneal vascularization and scarring and often results in serious visual morbidity. An early and accurate diagnosis can help prevent the same with a timely and appropriate intervention. This review aims to provide an understanding of the different diagnostic tools and presents an algorithmic approach to the management based on a comprehensive clinical examination. Although the diagnosis of LSCD usually relies on the clinical findings, they can be subjective and non-specific. In such cases, using an investigative modality offers an objective method of confirming the diagnosis. Several diagnostic tools have been described in literature, each having its own advantages and limitations. Impression cytology and in vivo confocal microscopy (IVCM) aid in the diagnosis of LSCD by detecting the presence of goblet cells. With immunohistochemistry, impression cytology can help in confirming the corneal or conjunctival source of epithelium. Both IVCM and anterior segment optical coherence tomography can help supplement the diagnosis of LSCD by characterizing the corneal and limbal epithelial changes. Once the diagnosis is established, one of various surgical techniques can be adopted for the treatment of LSCD. These surgeries aim to provide a new source of corneal epithelial stem cells and help in restoring the stability of the ocular surface. The choice of procedure depends on several factors including the involvement of the ocular adnexa, presence of systemic co-morbidities, status of the fellow eye and the comfort level of the surgeon. In LSCD with wet ocular surfaces, autologous and allogeneic limbal stem cell transplantation is preferred in unilateral and bilateral cases, respectively. Another approach in bilateral LSCD with wet ocular surfaces is the use of an autologous stem cell source of a different epithelial lineage, like oral or nasal mucosa. In eyes with bilateral LSCD with significant adnexal issues, a keratoprosthesis is the only viable option. This review provides an overview on the diagnosis and treatment of LSCD, which will help the clinician choose the best option amongst all the therapeutic modalities currently available and gives a clinical perspective on customizing the treatment for each individual case.

Drug induced cicatrizing conjunctivitis: A case series with review of etiopathogenesis, diagnosis and management

Drug induced cicatrizing conjunctivitis (DICC) is defined as a disease in which conjunctival cicatrization develops as a response to the chronic use of inciting topical and, rarely, systemic medications. DICC accounts for up to one third of cases of pseudopemphigoid, a large group of cicatrizing conjunctival diseases sharing similar clinical features to those of mucous membrane pemphigoid (MMP) but generally without the morbidity of progressive scarring or the need for systemic immunosuppression. The preservatives in topical anti-glaucoma medications (AGM) are the most frequently implicated inciting causes of DICC although topical antivirals, vasoconstrictors and mydriatics and some systemic drugs have been implicated. The literature review summarizes the classification, epidemiology, etiopathogenesis, histopathology, clinical presentation, diagnosis, management, and treatment outcomes of DICC in the context of a case series of 23 patients (42 eyes) with AGM induced DICC, from India and the UK. In this series all subjects reacted to preserved AGM with one exception, who also reacted to non-preserved AGM. At diagnosis >70% of eyes showed punctal scarring, inflammation, and forniceal shortening. Pemphigoid studies were negative in the 19/23 patients in whom they were carried out. DICC can be classified as non-progressive, progressive with positive pemphigoid immunopathology or progressive with negative pemphigoid immunopathology. It is unclear whether progressive DICC is a stand-alone disease, or concurrent (or drug induced) ocular MMP. Progressive cases should currently be treated as ocular MMP. The diagnosis can be made clinically when there is rapid resolution of symptoms and inflammation, usually within 1-16 weeks, after withdrawal of suspected inciting medications, ideally by temporary substitution of oral carbonic anhydrase inhibitors. If the response to withdrawal is uncertain, or the progression of inflammation and scarring continues then patients must be evaluated to exclude concurrent (or drug induced) MMP, and other potential causes of CC, for which the treatment and prognosis is different. Management, in addition to withdrawing inciting medications, may require short-term treatment of conjunctival inflammation with steroids, treatment of associated corneal disease with contact lenses or surface reconstructive surgery, control of intra-ocular pressure with non-preserved AGM and, in some, surgery for glaucoma or for trichiasis and entropion.

Intermediate-term Visual Outcomes and Complications of Type 1 Boston Keratoprosthesis With and Without Glaucoma Surgery

PURPOSE

Glaucoma is a cause of comorbidity in patients receiving the Boston keratoprosthesis (KPro). The aim of this study was to report the outcomes of the Boston KPro with or without glaucoma surgery.

METHODS

This was a retrospective single-center cohort study. Patients who underwent Boston KPro from March 2009 to February 2019 were included. One eye per patient (the first surgery) was included in this study. Patients were classified into 2 groups: KPro only (group 1) and KPro with any form of glaucoma procedure (group 2). Main outcome measures were Best-corrected visual acuity (BCVA), functional success (BCVA 20/200 or better), anatomical success (retention of KPro at the last follow-up), and complications.

RESULTS

Seventy-one eyes were included: 27 eyes (38%) in group 1 and 44 (62%) in group 2. There was no statistically significant difference in BCVA between groups 1 and 2 at each time point. Of the eyes in group 1, 11% lost light perception vision and 4.5% in group 2 (P = 0.293). There was no difference in anatomical success with 70% in group 1 and 77% in group 2 (P = 0.703) at the last follow-up, with a median failure time of 18 months. The functional success was 48% for group 1 and 50% for group 2 (P = 0.541).

CONCLUSIONS

Eyes undergoing KPro with glaucoma surgery before or at the same time carry a similar functional and anatomical success to eyes without glaucoma surgery.

Current perspectives of limbal-derived stem cells and its application in ocular surface regeneration and limbal stem cell transplantation

Limbal stem cells are involved in replenishing and maintaining the epithelium of the cornea. Damage to the limbus due to chemical/physical injury, infections, or genetic disorders leads to limbal stem cell deficiency (LSCD) with partial or total vision loss. Presently, LSCD is treated by transplanting limbal stem cells from the healthy eye of the recipient, living-related, or cadaveric donors. This review discusses limbal-derived stem cells, the importance of extracellular matrix in stem cell niche maintenance, the historical perspective of treating LSCD, including related advantages and limitations, and our experience of limbal stem cell transplantation over the decades.