Harminder S Dua

Dysfunctional Tear Syndrome A Delphi Approach to Treatment Recommendations

Purpose: To develop current treatment recommendations for dry eye disease from consensus of expert advice. Methods: Of 25 preselected international specialists on dry eye, 17 agreed to participate in a modified, 2-round Delphi panel approach. Based on available literature and standards of care, a survey was presented to each panelist. A two-thirds majority was used for consensus building from responses obtained. Treatment algorithms were created. Treatment recommendations for different types and severity levels of dry eye disease were the main outcome. Results: A new term for dry eye disease was proposed: dysfunctional tear syndrome (DTS). Treatment recommendations were based primarily on patient symptoms and signs. Available diagnostic tests were considered of secondary importance in guiding therapy. Development of algorithms was based on the presence or absence of lid margin disease and disturbances of tear distribution and clearance. Disease severity was considered the most important factor for treatment decision-making and was categorized into 4 levels. Severity was assessed on the basis of tear substitute requirements, symptoms of ocular discomfort, and visual disturbance. Clinical signs present in lids, tear film, conjunctiva, and cornea were also used for categorization of severity. Consensus was reached on treatment algorithms for DTS with and without concurrent lid disease. Conclusion: Panelist opinion relied on symptoms and signs (not tests) for selection of treatment strategies. Therapy is chosen to match disease severity and presence versus absence of lid margin disease or tear distribution and clearance disturbances.

Amniotic membrane transplantation for ocular surface reconstruction.

AIMS To evaluate the efficacy of amniotic membrane transplantation (AMT) for ocular surface reconstruction. METHODS 10 consecutive patients who underwent AMT were included. The indications were: group A, cases with persistent epithelial defect after corneal abscess (n=1), radiation (n=1), or chemical burn (n=3); group B, cases with epithelial defect and severe stromal thinning and impending or recent perforation, due to chemical burn (two patients, three eyes) or corneal abscess (n=2); group C, to promote corneal epithelium healing and prevent scarring after symblepharon surgery with extensive corneo-conjunctival adhesion (n=1). Under sterile conditions amniotic membrane was prepared from a fresh placenta of a seronegative pregnant woman and stored at −70°C. This technique involved the use of amniotic membrane to cover the entire cornea and perilimbal area in groups A and B, and the epithelial defect only in group C. RESULTS The cornea healed satisfactorily in four of five patients in group A, but the epithelial defect recurred in one of these patients. After AMT three patients underwent limbal transplantation and one penetrating keratoplasty and cataract extraction. In group B amniotic membrane transplantation was not helpful, and all cases underwent an urgent tectonic corneal graft. Surgery successfully released the symblepharon, promoted epithelialisation and prevented adhesions in the case of group C. CONCLUSION AMT was effective to promote corneal healing in patients with persistent epithelial defect, and appeared to be helpful after surgery to release corneo-conjunctival adhesion. Most cases required further surgery for visual and ocular surface rehabilitation. Amniotic membrane used as a patch was not effective to prevent tectonic corneal graft in cases with severe stromal thinning and impending or recent perforation.

Limbal epithelial crypts: a novel anatomical structure and a putative limbal stem cell niche

Background/aims: There is substantial evidence that mammalian epithelial stem cells are located within well defined niches. Although the corneoscleral limbus is acknowledged as the site of corneal epithelial stem cells no anatomical niche for such cells has yet been described. The authors undertook to re-evaluate the microanatomy of the limbus in order to identify possible sites that may represent a stem cell niche. Methods: Systematic serial 5–7 μm sections of human corneoscleral segments obtained from cadaver donors, were examined. The sections were stained with haematoxylin and eosin or toludine blue. Sections with specific areas of interest were further examined immunohistologically for the corneal epithelial marker cytokeratin 14 and the “stem cell” marker ABCG2 transporter protein. Results: Distinct anatomical extensions from the peripheral aspect of the limbal palisades were identified. These consist of a solid cord of cells extending peripherally or circumferentially. The cells stained positive for CK14 and ABCG2. Conclusions: A novel anatomical structure has been identified at the human limbus, which demonstrates characteristics of being a stem cell niche. The authors have termed this structure the limbal epithelial crypt.

Amniotic membrane transplantation

In 1910 Davis was the first to report the use of fetal membranes as surgical material in skin transplantation.1Since then the use of amniotic membrane in surgery has been expanded.1-9 It is now utilised as a biological dressing for burned skin, skin wounds, and chronic ulcers of the leg,9-16 as an adjunctive tissue in surgical reconstruction of artificial vagina,9 17-19 and for repairing omphaloceles.9 20 It has also been used to prevent tissue adhesion in surgical procedures of the abdomen, head, and pelvis.9 21 22 In the 1940s several authors reported the beneficial role of amniotic membrane in treating a variety of ocular surface disorders.5-7 23 However, its use was abandoned for decades until recently, when it was reintroduced to ophthalmologists. Several studies have addressed this subject and the scope of the application of amniotic membrane transplantation (AMT) in the management of ocular surface disorders is ever increasing. Certain characteristics make the amniotic membrane ideally suited to its application in ocular surface reconstruction. It can be easily obtained and its availability is nearly unlimited. The tissue can be preserved at −80°C for several months, allowing sufficient time to plan surgery or consider a trial of other options. Amniotic membrane does not express HLA-A, B, or DR antigens and hence immunological rejection after its transplantation does not occur.24-26It is also believed to have antimicrobial properties, reducing the risks of postoperative infection.27 Antifibroblastic activity28-30 and cell migration/growth promoting activity31-33 have also been demonstrated with regard to the amniotic membrane. The purpose of this paper is to review the characteristics of amniotic membrane that make it potentially useful to treat ocular surface abnormalities and to discuss the current indications, the surgical technique, and the outcome of AMT. Mammalian embryos lie …

Concise review: evidence for CD34 as a common marker for diverse progenitors.

CD34 is a transmembrane phosphoglycoprotein, first identified on hematopoietic stem and progenitor cells. Clinically, it is associated with the selection and enrichment of hematopoietic stem cells for bone marrow transplants. Due to these historical and clinical associations, CD34 expression is almost ubiquitously related to hematopoietic cells, and it is a common misconception that CD34‐positive (CD34+) cells in nonhematopoietic samples represent hematopoietic contamination. The prevailing school of thought states that multipotent mesenchymal stromal cells (MSC) do not express CD34. However, strong evidence demonstrates CD34 is expressed not only by MSC but by a multitude of other nonhematopoietic cell types including muscle satellite cells, corneal keratocytes, interstitial cells, epithelial progenitors, and vascular endothelial progenitors. In many cases, the CD34+ cells represent a small proportion of the total cell population and also indicate a distinct subset of cells with enhanced progenitor activity. Herein, we explore common traits between cells that express CD34, including associated markers, morphology and differentiation potential. We endeavor to highlight key similarities between CD34+ cells, with a focus on progenitor activity. A common function of CD34 has yet to be elucidated, but by analyzing and understanding links between CD34+ cells, we hope to be able to offer an insight into the overlapping properties of cells that express CD34. Stem Cells 2014;32:1380–1389

Human corneal anatomy redefined: a novel pre-Descemet's layer (Dua's layer).

PURPOSE To define and characterize a novel pre-Descemets layer in the human cornea. DESIGN Clinical and experimental study. PARTICIPANTS We included 31 human donor sclerocorneal discs, including 6 controls (mean age, 77.7 years). METHODS Air was injected into the stroma of donor whole globes (n = 4) and sclerocorneal discs (n = 21) as in the clinical deep anterior lamellar keratoplasty procedure with the big bubble (BB) technique. The following experiments were performed: (1) creation of BB followed by peeling of the Descemets membrane (DM); (2) peeling off of the DM followed by creation of the BB, and (3) creation of the BB and continued inflation until the bubble popped to measure the popping pressure. Tissue obtained from these experiments was subjected to histologic examination. MAIN OUTCOME MEASURES Demonstration of a novel pre-Descemets layer (Duas layer) in the human cornea. RESULTS Three types of BB were obtained. Type-1, is a well-circumscribed, central dome-shaped elevation up to 8.5 mm in diameter (n = 14). Type-2, is a thin-walled, large BB of maximum 10.5 mm diameter, which always started at the periphery, enlarging centrally to form a large BB (n = 5), and a mixed type (n = 3). With type-1 BB, unlike type-2 BB, it was possible to peel off DM completely without deflating the BB, indicating the presence of an additional layer of tissue. A type-1 BB could be created after first peeling off the DM (n = 5), confirming that DM was not essential to create a type-1 BB. The popping pressure was 1.45 bar and 0.6 bar for type-1 BB and type-2 BB, respectively. Histology confirmed that the cleavage occurred beyond the last row of keratocytes. This layer was acellular, measured 10.15 ± 3.6 microns composed of 5 to 8 lamellae of predominantly type-1 collagen bundles arranged in transverse, longitudinal, and oblique directions. CONCLUSIONS There exists a novel, well-defined, acellular, strong layer in the pre-Descemets cornea. This separates along the last row of keratocytes in most cases performed with the BB technique. Its recognition will have considerable impact on posterior corneal surgery and the understanding of corneal biomechanics and posterior corneal pathology such as acute hydrops, Descematocele and pre-Descemets dystrophies. FINANCIAL DISCLOSURE(S) The authors have no proprietary or commercial interest in any materials discussed in this article.

Amniotic membrane use in ophthalmology.

Purpose of review The purpose of this review is to describe the most recent and relevant clinical and experimental data about the use of amniotic membrane in ophthalmology. Recent findings The amniotic membrane is a biologic tissue that has been used as a graft for corneal and conjunctival reconstruction in a variety of ocular surface diseases. It is avascular and possesses antiangiogenetic, antiscarring and antiinflammatory properties. It is not a substitute but rather a substrate upon which cells can migrate and regenerate, forming new and healthy tissue. The amniotic membrane can also be used as a biologic patch, as a bandage, to treat acute inflammatory disorders. With the development of cell therapy, amniotic membrane can be also used as a carrier of limbal stem cells or their progeny, cultivated in vitro. Summary Amniotic membrane use in ophthalmic surgery has been shown to provide an alternative for corneal and conjunctival reconstruction in many clinically challenging situations; however, there is still a lack of scientific evidence based on randomized comparative studies to prove that its use is better than other alternative therapies for ocular surface reconstruction.

Stem cell differentiation and the effects of deficiency

AbstractStem cells have several unique attributes, the key features being their potency and plasticity. They have the ability to give rise to multiple cell lineages and to transdifferentiate into totally different cell type(s) when relocated to a novel stem cell niche. Most self-renewing tissues are served by stem cells. At the ocular surface, the corneo-scleral limbus is believed to provide the niche for corneal epithelial stem cells. A large body of circumstantial evidence, both clinical and basic, supports this view. However, specific identification of limbal stem cells has proved elusive. Cytokeratin markers, vimentin, epidermal growth factor receptors, p63, and others have been used to identify epithelial cell populations at the limbus, which could harbour putative stem cells. In contrast, none of the known haematopoietic stem cell markers namely, CD34 and CD133, stain any specific subset of corneal or limbal epithelial cells. Singly or collectively, none of these markers point to any unique cell(s) that could be regarded as stem cells, supporting the notion that the corneal epithelium is served by ‘committed progenitors’ rather than by stem cells. Disease or destruction of the corneo-scleral limbus is associated with consequential events that eventually lead to visual impairment or blindness. Conjunctivalisation and vascularisation of the corneal surface and persistent or recurring epithelial defects are hallmarks of limbal deficiency.

Autologous limbal transplantation in patients with unilateral corneal stem cell deficiency

AIM To describe a surgical technique for autologous limbal stem cell transplantation and the outcome of a series of patients with unilateral stem cell deficiency. METHODS A report of six consecutive patients who underwent autologous limbal stem cell transplantation is presented. The primary diagnosis included alkali burn (n=3), conjunctival intraepithelial neoplasia (CIN) (n=1), recurrent pterygium (n=1), and contact lens induced keratopathy (n=1). The autologous transplanted tissue consisted of peripheral cornea, limbus, and conjunctiva obtained from the contralateral eye. Three of the above patients underwent penetrating keratoplasty in association with auto-limbal transplantation. A significant modification to established techniques was the close monitoring of conjunctival epithelial migration in the immediate postoperative period. If conjunctival epithelium threatened to migrate on to the corneal surface, it was mechanically removed at the slit lamp and prevented from crossing the limbus. This was required in three patients. RESULTS The mean follow up was 18.8 months. The outcome was satisfactory in all cases: a stable corneal surface was restored and there was a substantial improvement in vision and symptoms. One patient had a primary failure of the corneal allograft associated with glaucoma, and 6 months later developed a retinal detachment. No complications were noted in the donor eye with the exception of one patient who developed filamentary keratitis along the edge of the donor site. CONCLUSION Autologous limbal transplantation with corneal, limbal, and conjunctival carriers was found to be useful for ocular surface reconstruction, over a mid-term follow up, in patients with unilateral stem cell deficiency. Close monitoring of the migration of conjunctival epithelium in the immediate postoperative period, and preventing it from crossing the limbus, ensured that the corneal surface was re-epithelialised exclusively from epithelial cells derived from the transplanted limbal tissue. This approach should improve the success of this procedure.

Infliximab in the treatment of refractory posterior uveitis.

PURPOSE To determine the efficacy and safety of infliximab in the treatment of refractory posterior uveitis. DESIGN Noncomparative interventional case series. PARTICIPANTS Five patients with posterior uveitis were treated: 3 had Behçets syndrome, and 2 had idiopathic posterior uveitis. INTERVENTIONS Patients with sight-threatening uveitis refractory to other immunosuppressive agents were treated with infliximab. MAIN OUTCOME MEASURES Intraocular inflammation, by using binocular indirect ophthalmoscopy score, retinal vasculitis, and visual acuity. Adverse effects of infliximab were documented. RESULTS Within 2 weeks of the first infusion of infliximab, 4 of 5 patients showed marked improvement in vitreous haze and visual acuity. By the 6-month follow-up, the same four patients had achieved remission of posterior uveitis and had successfully withdrawn all other immunosuppressive therapy. Further infusions of infliximab were required in 3 patients. One patient developed ocular and systemic tuberculosis, which responded to antituberculous treatment. CONCLUSIONS Infliximab is effective in the treatment of sight-threatening refractory posterior uveitis. However, patients should be thoroughly screened for tuberculosis before treatment and followed up closely during and after therapy with infliximab.