Tectonic Support Research Articles

Hybrid technique of tuck-in Tenon's patch graft and tissue adhesives and bandage contact lens (TABCL) for large corneal perforation in microbial keratitis.

We describe the hybrid technique of tuck-in Tenon's patch graft (TPG) and tissue adhesive bandaged contact lens (TABCL) for large corneal perforations (>5 mm) with intact surrounding stroma. Management of large corneal perforation is often challenging, and urgent availability of donor cornea might be difficult; Tenon patch alone does not provide tectonic support; hence, this hybrid technique can be used safely in large perforations. This involves freshening the perforation edges, creating a 3600 stromal pocket, harvesting a Tenon's graft 1 mm oversized, tucking into the pocket, and suturing. Then areas of leakage were noted, and only those areas were supplemented with minimal cyanoacrylate glue (CG) at the graft edges. This technique was used in two eyes, one with a large corneal perforation and intact surrounding stroma and the other with 4 mm corneal fistula post healed keratitis with a failed primary TPG alone, and led to epithelialization and a smooth corneal surface at 6 weeks. The advantages include autologous tissue, cost-effective, easily available, minimal post-operative inflammation, vascularization, and surface irregularity.

A Case of Corneal Melt and Perforation Associated with Rheumatoid Arthritis Managed by Corneal Patch Graft

Corneal melt is a rare yet severe complication of Peripheral Ulcerative Keratitis (PUK), observed in patients with Rheumatoid Arthritis (RA). The mortality rate associated with corneal melt is high, warranting aggressive treatment. A 50-year-old female, a known case of RA for 20 years, presented with complaints of blurred vision, watering, irritation, and photophobia in both eyes for the last year, with worsening symptoms in the Right Eye (RE) for the past 15 days. She was diagnosed elsewhere in a private hospital with RE corneal melt and perforation and inferior corneal thinning in the Left Eye (LE), with an ulcer defect. She underwent corneal perforation suturing in the RE before reaching the present facility. On examination, a sutured corneal perforation was present in the RE, and corneal thinning and melt were seen para-centrally and inferiorly in the LE. Surgical treatment with RE corneal patch graft repair was performed. The patient was given oral methotrexate and prednisolone for aggressive systemic control of RA and to ensure the survival of the patch graft. The vision in the RE improved following the procedure, maintaining the tectonic integrity of the cornea. On follow-up, aleucomatous opacity was noted in the RE patch graft tissue. Corneal thinning in the LE was treated topically with artificial tears and antibiotic eyedrops, which eventually healed, forming macular corneal opacity. Overall, corneal patch graft repair enabled the maintenance of tectonic support and corneal integrity, as well as vision improvement in the patient with RA presenting with the complication of corneal melt and perforation.

Our experience of gamma-irradiated sterile cornea allograft surgery

Background: Gamma-irradiated sterile cornea (GISC) is a non-immunogenic, cross-linked, sterile patch graft in which the donor keratocytes and endothelial cells are eliminated. It can serve as a graft to cover glaucoma drainage devices, as a graft tissue for frank or impending corneal perforations in tectonic keratoplasty, as a graft tissue in lamellar keratoplasty, and as a carrier tissue for keratoprosthesis. The authors present their experience in treating severe ulcers with microperforations using GISC. Methods: In 2021, eight patients with corneal ulcers unresponsive to medical treatment were chosen to be candidates for VisionGraft® (Corneagen) GISC transplantation and underwent successful corneal surgery. Results: In 6 out of the 8 patients, the patch graft successfully restored tectonic support until optical keratoplasty could be performed if decision was made to improve visual acuity later. The remaining 2 grafts did not epithelialize after surgery and developed sterile corneal melt. Conclusion: This case series supports the use of VisionGraft® GISC as a graft for restoring the anatomy of the eyeball in the setting of corneal perforation.

Long-term outcome of limbal-sparing lamellar keratoplasty in keratoglobus: A retrospective case series

We report six eyes of five patients with keratoglobus who underwent limbal-sparing lamellar keratoplasty (LSLK) with 7 years of follow-up. In two patients’ three eyes, it was congenital and the rest had acquired keratoglobus from pellucid marginal degeneration combined with keratoconus. In LSLK, the peripheral corneal epithelium is dissected to include the stem cells and reflected along with conjunctival peritomy. The host cornea is de-epithelialized, stromal irregularities dissected, and then a corneoscleral graft denuded of Descemet’s membrane is anchored to a scleral ledge fashioned. Postoperatively, all received adequate tectonic support, and except for one posttrauma eye, the rest improved visually.

Lamellar keratoplasty using decellularised porcine cornea as an acellular scaffold graft for surgical management of deep corneal ulcer in a dog

Corneal ulcers are one of the most common eye affection in domestic animals, especially dogs. In preclinical studies, porcine corneas were used regularly as an animal model due to its relative similarity to human cornea and its availability in great numbers from slaughter houses. In the present study, decellularised porcine cornea was used for corneal grafting as an acellular scaffold graft material in a case presented with deep corneal ulcer. The efficiency of the graft material was analysed on the day of presentation, days 7, 14, 21 and 60 post grafting, based on corneal clarity, oedema, neovascularisation, pigmentation, visual function and scar tissue formation. Decellularised porcine corneas were found to be very convenient to handle during surgery, provided good tectonic support, had good tissue biocompatibility and produced only mild to moderate graft opacity.

Spatio-temporal variability and controlling factors for postglacial denudation rates in the Dora Baltea catchment (western Italian Alps)

Abstract. Disentangling the influence of lithology from the respective roles of climate, topography and tectonic forcing on catchment denudation is often challenging in mountainous landscapes due to the diversity of geomorphic processes in action and of spatial and temporal scales involved. The Dora Baltea catchment (western Italian Alps) is an ideal setting for such investigation, since its large drainage system, extending from the Mont Blanc Massif to the Po Plain, cuts across different major lithotectonic units of the western Alps, whereas this region has experienced relatively homogeneous climatic conditions and glacial history throughout the Quaternary. We acquired new 10Be-derived catchment-wide denudation rates from 18 river-sand samples collected both along the main Dora Baltea river and at the outlet of its main tributaries. The inferred denudation rates vary between 0.2 and 0.9 mm yr−1, consistent with previously published values across the European Alps. Spatial variability in denudation rates was statistically compared with topographic, environmental and geological metrics. 10Be-derived denudation rates do not correlate with modern precipitation and rock geodetic uplift. We find, rather, that catchment topography, in turn conditioned by bedrock structures and erodibility (lithotectonic origin) and glacial overprint, is the main driver of 10Be-derived denudation patterns. We calculated the highest denudation rate for the Mont Blanc Massif, whose granitoid rocks and long-term tectonic uplift support high elevations, steep slopes and high relief and thus favour intense glacial and periglacial processes and recurring rockfall events. Finally, our results, in agreement with modern sediment budgets, demonstrate that the high sediment input from the Mont Blanc catchment dominates the Dora Baltea sediment flux, explaining the constant low 10Be concentrations measured along the Dora Baltea course even downstream the multiple junctions with tributary catchments.

Lamellar Keratoplasty Using Acellular Bioengineering Cornea (BioCorneaVetTM) for the Treatment of Feline Corneal Sequestrum: A Retrospective Study of 62 Eyes (2018-2021).

Simple SummaryCorneal sequestrum is a specific and common corneal disease in cats. Surgery treatment is the recommended option. Acellular bioengineering cornea (ABC) is a popular and effective corneal transplantation material. However, no study has been published to evaluate the effectiveness and outcome of ABC lamellar transplantation for the treatment of feline corneal sequestrum (FCS). The purpose of this retrospective study was to evaluate the surgical effect of ABC lamellar transplantation in the treatment of FCS. All cats were diagnosed with FCS. All eyes received ABC lamellar transplantation for the first time, including 61 cats (62 eyes), aged 6–120 months. The average sequestrum size was 7.98 mm, with a medium of 7.75 mm (range, 4.75–11.75 mm), and the sequestrum thickness included 200 microns for 1 eye (1.61%), 300 microns for 28 eyes (45.16%), 400 microns for 29 eyes (46.77%), and 450 microns for 4 eyes (6.45%). All eyes retained vision after surgical treatment, and there was no recurrence during the follow-up period. This study has several limitations, including incomplete unification and standardization of data collection, some vacancies of follow-up time, inconsistency between then optical coherence tomography(OCT) examination and postoperative photo collection. Despite several limitations, our results show that ABC is easy to obtain and store, and has the choice of different sizes and thicknesses to achieve rapid corneal healing, and satisfactory visual and cosmetic effects in FCS treatment. Acellular bioengineering cornea can be a good alternative for the treatment of FCS.To retrospectively evaluate the effectiveness and outcome of lamellar keratoplasty using acellular bioengineering cornea (BioCorneaVetTM) for the treatment of feline corneal sequestrum (FCS). The medical records of cats diagnosed with FCS that underwent lamellar keratoplasty with BioCorneaVetTM between 2018 and 2021 with a minimum of 3 months of follow-up were reviewed. Follow-up examinations were performed weekly for 3 months, and then optical coherence tomography (OCT) examination was performed on select patients at 0, 3, 6, and 12 months post-operatively. A total of 61 cats (30 left eyes and 32 right eyes) were included. The Persian breed was overrepresented, 48/61 (78.69%). Four different thicknesses of acellular bioengineering cornea were used (200, 300, 400, or 450 microns), and the mean graft size was 8.23 mm (range, 5.00–12.00 mm). Minor complications were composed of partial dehiscence, and protrusion of the graft occurred in 7/62 eyes (11.29%). The median postoperative follow-up was 12.00 months (range, 3–41 months). A good visual outcome was achieved in 60/62 eyes (96.77%), and a mild to moderate corneal opacification occurred in 2/62 (3.23%). No recurrence of corneal sequestrum was observed. From the results, lamellar keratoplasty using acellular bioengineering cornea (BioCorneaVetTM) is an effective treatment for FCS, providing a good tectonic support and natural collagen framework, and resulting in satisfactory visual and cosmetic effects.

Corneal sequestra in cats: 175 eyes from 172 cases (2000-2016).

To report the clinical outcomes of different surgical treatments used to manage feline corneal sequestra in a large number of cases. Medical records of 172 cats affected by feline corneal sequestra and surgically managed by different techniques were retrospectively evaluated. Signalment, surgical technique, visual outcomes, postoperative corneal clarity and recurrence were evaluated. One hundred and seventy-two cats (175 eyes) of different breeds, ages and sex were included in the retrospective case series. The Persian was the most represented breed (123/172; 71.5%), followed by Exotic Shorthair breed (21/172; 12.2%), Domestic shorthair breed (21/172; 12.2%) and a smaller group of other different breeds (7/172). Surgical management included a superficial (84/175 eyes) or deep (91/175 eyes) lamellar keratectomy in association with the following covering techniques (tectonic support and/or protective support): nictitans membrane flap (n=84), conjunctival pedicle graft (n=52), BioSISt graft (n=9), corneoconjunctival transposition (n=7), corneoconjunctival transposition+nictitans membrane flap (n=6), conjunctival free island graft (n=6), BioSISt+conjunctival pedicle graft (n=6), BioSISt+nictitans membrane flap (n=4) and bridge conjunctival graft (n=1). At the end of the retrospective case series, visus was present in all patients and no or mild corneal opacity was detected in 86% (151/175 eyes) of the patients. Sequestra recurred in 20 eyes (20/175; 11.4%) within 2 years. This paper describes the clinical outcomes of a large number of cases of feline corneal sequestra treated with varying surgical techniques and provides useful insight regarding the prognosis and outcomes of these techniques within feline ophthalmology.

Modified Contact Lens Sandwich Technique of Glue for Management of Medium to Large Corneal Perforations in the COVID Era.

The aim of this article is to describe a novel technique of gluing as an interim measure to provide tectonic support in cases of medium-sized to large-sized (3-6 mm) corneal perforations. Five eyes of five patients in which conventional cyanoacrylate glue application was not feasible, and therapeutic keratoplasty could not be performed in view of the unavailability of corneal tissues were included. Surgery to maintain integrity of the globe was performed, and a therapeutic keratoplasty was performed on tissue availability (mean interval of 7.4 days). On follow-up, all patients had a well-formed anterior chamber, and none of them had progression. The contact lens sandwich technique of glue was a feasible, reproducible, and economical technique during times of tissue unavailability such as the present COVID pandemic, in patients with medium to large perforated corneal ulcers.

Tuck-in tenon's patch graft for corneal perforation

Corneal perforation remains to be one of the most dreaded complications of ocular trauma and its prompt diagnosis and management is key to quick recovery. Tuck-in Tenon's patch graft is an extremely viable and handy technique to tackle corneal perforation. The tenon's tissue, being autologous, reduces the chance of rejection while providing good tectonic support. This is a case series of tuck-in Tenon's patch graft done for cases of corneal perforation. Through the case series, we try to put forth our experience with this novel technique.

Autologous corneal graft for the treatment of deep corneal defects in dogs: 15 cases (2014‐2017)

To describe the use of corneal autografts for repair of deep corneal defects in dogs. Retrospective analysis of clinical records of dogs that received autologous corneal grafts. Fifteen dogs (16 eyes) of different breed, age and gender were included. Brachycephalic breeds were overrepresented (10/15 dogs). Defects were unilateral in 14 dogs and bilateral in one dog, extended to at least 80% of the stromal thickness in all eyes, with descemetoceles in four eyes and corneal perforations in five eyes. Most ulcers (13/16 eyes) were located centrally. Corneal autografts were harvested from healthy peripheral cornea of the ipsilateral eye. The thickness of the autograft was limited to a set depth of 0.3 mm. The autograft was sutured into a previously debrided ulcer bed with a continuous or simple interrupted suture pattern using absorbable or non-absorbable suture material. Additional interventions included a partial temporary tarsorrhaphy and bandage contact lenses. Postoperatively patients received topical antibiotics and systemic anti-inflammatory drugs, and 12/15 dogs also received systemic antibiotics. Mean follow-up time was 54 days (2 to 462). In all eyes the donor site healed uneventfully with mild, persistent corneal fibrosis. Postoperative complications included autograft keratomalacia, graft dehiscence and corneal pigmentation. No patient required additional surgery. Good structural and functional outcome was accomplished in 14 of 16 eyes. Autologous corneal grafts provide tectonic support and result in good corneal transparency in selected cases of dogs with deep to perforated corneal ulcerations.

Techniques of noncircular corneal transplantation

The management of peripheral corneal diseases, including Mooren's ulcer, Terrien's marginal degeneration, peripheral ulcerative keratitis and pellucid marginal degeneration is challenging. Circular grafts must either be very large, resulting in the excision of healthy tissue, or eccentric, leading to high levels of astigmatism. This review summarizes the range of noncircular keratoplasty procedures available to surgeons, in addition to their indications, and surgical techniques. Noncircular grafts have been demonstrated to be useful in the management of peripheral corneal diseases. They are effective at providing tectonic support and also facilitate visual rehabilitation. Specifically, they produce favourable postoperative visual and astigmatic outcomes. The evidence relating to these procedures is largely limited to case reports and case series, with no large-scale studies available. Noncircular keratoplasty procedures are useful in the management of peripheral corneal diseases, which is typically difficult. There is a need for larger studies to investigate the relative advantages and disadvantages of these procedures and further characterize their outcomes.

Role of bandage contact lens in corneal disorders: A review

Role of bandage contact lens in corneal disorders: A review - IJOOO- Print ISSN No: - 2581-5024 Online ISSN No:- 2581-5016 Article DOI No:- 10.18231/j.ijooo.2019.060, IP International Journal of Ocular Oncology and Oculoplasty-IP Int J Ocul Oncol Oculoplasty

Long-term clinical outcomes of keratoplasty using gamma-irradiated corneal lenticules

ObjectiveTo report long-term clinical outcomes of gamma-irradiated corneal lenticules in partial and full-thickness keratoplasty.Methods and AnalysisThis multicentre, retrospective case series includes 23 patients who underwent surgery at three centres (India,...

A Multivariate Approach for Mapping Lithospheric Domain Boundaries in East Antarctica

AbstractBeneath the ice of East Antarctica lies a continent that is likely to be as geologically complex as its neighbors in Gondwana. An improved model of the heterogeneous lithosphere is required to progress research on Antarctica's tectonic evolution and support interdisciplinary studies of cryosphere and solid Earth interaction. We make use of multiple data sets, which were updated following the field campaigns and compilations of the International Polar Year of 2007/2008. Seismic tomography results, gravity anomalies, and surface elevation are used in a novel method, which combines spatial multivariate data to map possible boundaries as projected likelihood functions. Six multivariate combinations are tested and compared with sparse geological observations in East Antarctica. The resulting lithospheric domain boundaries contribute to our understanding of the deep continental structure. New boundaries are suggested in the interior, and models agree with likely surface expressions of crustal tectonic boundaries exposed along the coast.

Crescentic Tuck in Lamellar Keratoplasty—A Novel Technique in a Case of Advanced Pellucid Marginal Corneal Degeneration

To describe a new surgical technique "crescentic tuck in lamellar keratoplasty" for the management of advanced pellucid marginal corneal degeneration (PMCD). A 45-year-old man with advanced PMCD and maximal thinning in the inferior juxtalimbal periphery underwent a crescentic lamellar keratoplasty in the right eye. Best-corrected visual acuity was 6/60 with no further improvement because of severe irregular astigmatism. Thinnest pachymetry in the peripheral cornea was 280 μm. Peripheral crescent-shaped lamellar corneal dissection of 3.5-mm width was performed, and an intrastromal pocket was fashioned from 4 to 8 O'clock, extending beyond limbus. A crescent-shaped donor corneal button of 3.5-mm width was denuded of its endothelium and beveled in inferior periphery to create a flange. The flange was tucked into the peripheral scleral pocket. The donor graft was secured to the host bed using 10-0 nylon interrupted sutures. Donor cornea integrated with the host bed over time and best spectacle-corrected visual acuity at 1 year improved to 6/9 with -1.25/-3.5 D × 90°. The simK (simulated keratometry) changed from 41.6/56.3 diopters (D) to 45.1/50.6 D. The astigmatism reduced from 14.6 D to 5.5 D. Crescentic tuck in lamellar keratoplasty provides good apposition of the donor lenticule and tectonic support to the peripheral thin cornea while preserving the peripheral limbal stem cells. Additionally, there is a significant reduction in the astigmatism, resulting in visual improvement.

Cryopreservation (-20°C) of canine corneoscleral tissue: histological, microbiological, and ultrastructural study.

To evaluate microbiological, histological, and ultrastructural characteristics of short-term cryopreserved (STC) canine corneoscleral tissue (<1year) and to compare it with long-term cryopreserved (LTC) tissue (>6years). Thirty-six healthy canine globes. After a decontamination protocol, globes were enucleated and stored at -20°C. Corneoscleral tissue was evaluated at different periods: <1year (20 eyes) and >6years (12 eyes). Four eyes were used as controls. Microbiologic study included direct (blood, McConkey and Sabouraud agars) and enrichment (brain-heart infusion broth) cultures. Cryopreservation artifacts were evaluated by hematoxylin-eosin. Corneoscleral collagen organization and number of normal and dead keratocytes were established by transmission electron microscopy (TEM). Terminal deoxynucleotidyl transferasedUTP nick end labeling (TUNEL) was also used for keratocyte characterization. Corneal microbial growth was observed in 25% of the direct STC cultures, and in 47.4% and 16.7% of the enriched STC and LTC cultures, respectively. Scleral STC direct cultures were 30% positive, while enrichment cultures were positive in 66.7% and 16.7% of the STC and LTC, respectively (P=0.011). Cryopreservation artifacts were higher in LTC tissues (P<0.001). Apoptotic keratocytes were predominant by TEM and TUNEL, in both STC and LTC. Minimal structural differences were detected in collagen organization between STC and LTC. Cryopreservation of canine corneoscleral tissue seems to reduce bacterial contamination over time. Apoptosis is the main way of death of cryopreserved canine keratocytes. Based on the lack of significant structural differences between STC and LTC samples, these cryopreserved tissues could potentially be used for tectonic support for at least 8years without structural or microbiological impediment.

Projecting an Architectural Perspective: Euclidean Propositions and Common Practices at Gonçalves Sena’s Workshop

The projection of architectural perspectives, from the drawing plane to the tectonic support, might be the central problem of quadratura. However, specialized treatises tend to treat it through ideal statements. Highlighting the materialization of abstract reasoning, those demonstrations serve the scientific legitimation of quadratura practice, possibly circumscribed to enlightened scientific and artistic circles, rather than the dissemination of procedures aiming to train people in the projection craftsmanship. This may even be the best-kept secret of the quadratura painters. In this context, this paper is focused on Sena’s quadratura (1754), at the church of Santarem’s Jesuit College, where under Vieira’s statements exposed in his treatise on perspective (Tractado de Prospectiva, Codex 5170, Biblioteca Nacional de Lisboa, 1716), we will disclose procedures based upon common practices of the painter’s workshop concerning the outline and projection of the image.

Cryopreservation (−20 °C) of feline corneoscleral tissue: histologic, microbiologic, and ultrastructural study

To evaluate microbiological, histologic, and ultrastructural characteristics of short-term cryopreserved (STC) feline corneoscleral tissue (<1 year) and to compare it with long-term cryopreserved (LTC) tissue (>7 years). Twenty healthy feline globes were obtained from 2003 to 2013. After a decontamination protocol, globes were enucleated and stored at -20 °C in broad-spectrum antibiotics. Corneoscleral tissue was evaluated at different storage periods: <1 year (10 eyes) and >7 years (8 eyes). Two eyes were used as controls. Microbiologic study included direct (blood, McConkey, and Sabouraud agars) and enrichment (brain-heart infusion broth) cultures. Cryopreservation artifacts were evaluated by hematoxylin-eosin. Corneoscleral collagen organization and number of normal and dead keratocytes were established by transmission electron microscopy. Although microbiologic cultures were positive only in STC [direct (20.8%); enrichment (37.5%)], significant differences between periods were only found in enrichment cultures (P = 0.006). Cryopreservation artifacts were most commonly observed in LTC tissues (P < 0.001). Normal keratocytes were predominant in STC corneas (STC 58.3%, LTC 12.5%) and apoptotic ones in LTC (STC 41.7%, LTC 75%), whereas necrotic keratocytes were only seen in LTC (LTC 12.5%) (P = 0.046). No structural differences were detected in collagen organization between STC and LTC (Pcornea = 0.147; Psclera = 0.362). Cryopreservation of feline corneoscleral tissue seems to reduce bacterial contamination over time. Apoptosis is the main cause of death of cryopreserved feline keratocytes. Based on the lack of significant structural differences between STC and LTC samples, these cryopreserved tissues could potentially be used for tectonic support for at least 10 years without structural or microbiological impediment.

Corneal grafting for the treatment of feline corneal sequestrum: a retrospective study of 18 eyes (13 cats).

To determine the clinical outcome of corneal grafting for the treatment of feline corneal sequestrum (FCS). Domestic cats. A review of the medical records of cats that underwent keratoplasty as a treatment of FCS at the VTH-UAB, from 2002 to 2012, was carried out. Thirteen cats (18 eyes) of different breed, age, and gender were included. Persian cats were overrepresented (12/13;92%). There were nine males and four females, of a mean age of 3.4 years (0.7-7.1). Ipsilateral chronic corneal ulceration was reported as the most common concurrent ocular disease (6/18;33%). Keratoplasty was performed bilaterally in 5 cats (5/13;38%) and unilaterally in 8 (8/13;62%). Lamellar keratoplasty was performed in 17 eyes (17/18;95%) and full-thickness keratoplasty in 1 (1/18;5%). Mean graft size was 8.3 mm (4-11.5). Fresh homologous graft was performed in 2 eyes (2/18;11%) and frozen graft in 16 (16/18;89%). Of the latter group, homologous graft was performed in 6 eyes (6/16;37.5%) and heterologous in 10 (10/16;62.5%). In all the cats, postoperative treatment included topical antibiotics, corticosteroids, cycloplegics, and 0.2% cyclosporine A. Median follow-up time was 18.2 months, and main postoperative complications were diffuse mild epithelial pigment formation (2/18;11%), graft malacia (1/18;5%), and sequestrum recurrence (1/18;5%). Mean epithelial healing time was 19.2 days. Good visual outcome was achieved in all the eyes (100%), the majority of them having faint or mild corneal opacity (15/18;83%). Keratoplasty is an effective surgical treatment for FCS. The donor tissue provides excellent tectonic support to the affected corneas, with good visual and cosmetic outcome.