A comparison between dehydrated and cryopreserved heterologous corneal grafts for penetrating keratoplasty in dogs and cats.

OBJECTIVE: To compare the efficacy of dehydrated and cryopreserved heterologous corneal grafts in the management of full-thickness corneal defects in cats and dogs. ANIMALS STUDIED: Sixty-five cats (81 eyes) and 42 dogs (51 eyes) with full-thickness corneal defects of different origin. MATERIALS AND METHODS: This prospective randomized trial included 132 animal eyes (81 feline and 51 canine) with different full-thickness corneal defects. Penetrating keratoplasty with cryopreserved and dehydrated corneal grafts was performed in 57 and 75 eyes, respectively. Follow-up lasted for 6 months. RESULTS: Optically clear cornea with mild scarring was achieved in 40.4% of cases (23/57 eyes) after cryopreserved and in 42.7% of cases (32/75 eyes) after dehydrated corneal grafting. Moderate scarring after cryopreserved and dehydrated corneal grafting was observed in 35.1% of cases (20/57 eyes) and 37.3% of cases (28/75 eyes), respectively. Severe scarring and corneal opacities with severe vision loss after cryopreserved and dehydrated corneal grafting developed in 22.8% of cases (13/57 eyes) and 18.7% of cases (14/75 eyes), respectively. In two groups of animals combined, the affected eyes were salvaged and visual function improvement of varying degree was achieved in 78.0% of cases (103/132 eyes). Transplant rejection warranted enucleation in 1.75% of cases (1/57 eyes) and 1.3% of cases (1/75 eyes) after cryopreserved and dehydrated corneal grafting, respectively. CONCLUSIONS: No statistically significant differences in clinical outcomes of penetrating keratoplasty with cryopreserved and dehydrated corneal grafts were observed. Dehydrated cornea may be considered a viable alternative to cryopreserved grafts for the management of full-thickness corneal defects.

Penetrating Keratoplasty in Dogs using Acellular Porcine Corneal Stroma (BioCorneaVet™): A prospective pilot study of five cases.

OBJECTIVE: This prospective pilot study was conducted to evaluate the outcome of a commercially available corneal stroma substitute, Acellular Porcine Corneal Stroma (APCS), in dogs undergoing penetrating keratoplasty (PK) to restore corneal integrity after having deep ulcers. METHOD: Five dogs (1 eye in each dog) underwent a PK using APCS (BioCorneaVet™) as a graft. The surgical procedure and peri- and postoperative treatment were standardized. All cases required a minimum 6 months follow-up. Ease of keratoprosthetic tissue handling, graft survival, anterior chamber stability, corneal opacity, neovascularization and re-epithelialization were noted. Presence of secondary uveitis was investigated. RESULTS: BioCorneaVet™ was easy to handle and, at all-time points, provided adequate tectonic support. Graft survival was achieved in all 5 cases. A minimum follow-up period of 10 months was available for the five eyes (22 months maximum). Degree and area of corneal graft opacity progressively improved resulting in minimal to moderate loss of transparency in all cases but one, where it was severe. Neovascularization degree was most severe 0.5-1 month after surgery and fully resolved 4-6 months post-surgery. Re-epithelialization was complete in the majority of grafts in 1 month. Secondary uveitis was not detected at any time in 4 of 5 dogs. CONCLUSION: BioCorneaVet™ seems to be an effective graft for PK in the dog. In this case series, APCS was convenient to handle during surgery and provided excellent tectonic support. The material showed good tissue biocompatibility and resulted in the majority of cases in minimal to moderate graft opacity, that ameliorates with time.

Modified penetrating keratoplasty with Acell® bioscaffold implant in seven horses with deep full-thickness corneal stromal abscess.

OBJECTIVE: To describe and evaluate a modified penetrating keratoplasty technique utilizing ACell® for management of equine deep stromal or full-thickness corneal stromal abscesses (SA). METHODS: Cases presenting to the University of Georgia Ophthalmology service for surgical management of SA necessitating penetrating keratoplasty (PK) were included in the study population. Surgery entailed the use of an ACell® disk sutured within the deep level of a stepped full-thickness corneal incision with an overlying conjunctival pedicle flap placed in the superficial step incision. Patients were evaluated for success as defined by a comfortable, visual outcome. RESULTS: Surgery was performed in seven horses. Conjunctival flap incorporation and globe retention occurred in all patients. Functional vision was maintained in six of seven eyes (85.7%) at last follow-up examination (mean of 87.6 days [range 41-251 days]). Mean size of ACell® implant was six millimeters (range 4-8 mm). Postoperative complications included moderate to severe anterior uveitis (n = 2), diffuse keratitis (n = 1), incipient cataract formation (n = 3), and anterior and posterior synechiae (n = 1). CONCLUSIONS: This technique is a viable option for treatment of equine SA requiring PK. The use of bioscaffold implant is an alternative to frozen and fresh donor cornea transplantation.

Corneal grafting for the treatment of full-thickness corneal defects in dogs: a review of 50 cases.

OBJECTIVE: To describe corneal grafting for the treatment of full-thickness corneal defects in dogs and to determine its effectiveness in preserving vision. METHODS: A review of the medical records of dogs that underwent corneal grafting following corneal perforations (≥3 mm) at the VTH-UAB from 2002 to 2012 was carried out. RESULTS: Fifty dogs of different breed, age and gender were included. Brachycephalic breeds were overrepresented (37/50;74%). All cases were unilateral, with euryblepharon being the most common concurrent ocular abnormality (20/50;40%). Full-thickness penetrating keratoplasties (FTPK) were performed in 21/50 eyes (42%) and lamellar keratoplasties (LK) in 29/50 eyes (58%). Frozen grafts (FroG) were used in 43/50 eyes (86%) and fresh homologous grafts (FreHoG) in 7/50 (14%). Of the former group, 26 were homologous (FroHoG:60%) and 17 heterologous (FroHeG:40%). A combination of topical medication (antibiotics, corticosteroids, cycloplegics, and 0.2% cyclosporine A) and systemic mycophenolate mofetil was administered. Median follow-up time was 200 days. Postsurgical complications included wound dehiscence (6/50;12%) and glaucoma (4/50;8%). Clinical signs of graft rejection were diagnosed as follows: FroHoG (13/26;50%), FroHeG (11/17;65%), FreHoG (4/7;57%), FTPK (12/21;57%), and LK (16/29;55%). Medical treatment successfully controlled graft rejection in 11/28 eyes (39%). Good anatomical outcome was achieved in 86% (43/50), of which 95% (41/43) were visual at last examination, with moderate opacification to complete transparency of the graft present in 48.2%. CONCLUSIONS: Corneal grafting is an effective surgical treatment for full-thickness corneal defects in dogs. If graft rejection is present, additional medical or surgical therapy may be necessary, achieving a highly satisfactory visual outcome.

A new surgical technique to treat corneal perforations using amniotic membrane and surgical adhesive / Nova técnica cirúrgica para tratamento de perfuração de córnea utilizando membrana amniótica e adesivo cirúrgico

The objectives of this study were to compare surgical techniques and the effects of using n-butyl 2-cyanoacrylate and bovine amniotic membrane to repair perforated lesions in corneas. Penetrating keratoplasty was performed in sixty New Zealand White rabbits under general anesthesia. Group 1 (G1) was treated with n-butyl 2-cyanoacrylate, group 2 (G2) received a fragment of amniotic membrane through the anterior chamber and application of n-butyl 2-cyanoacrylate over the lesion, group 3 (G3) was treated with the same technique as G2 with the addition of an amniotic membrane bandage covering the cornea and sutured in the limbus region, and group 4 (G4) was treated with an amniotic membrane sutured to the lesion and an amniotic membrane bandage sutured in the limbus region. Clinical, histological and histomorphometric examinations of the corneas were performed. The membrane acted as a barrier for aqueous humor in G2 and G3, thereby keeping the surface dry for adhesive application; it also prevented the adhesive from contacting intraocular structures. The groups treated with amniotic membrane and surgical adhesive showed better results than the groups treated with either material alone. Thus, the combination of the membrane with the adhesive is recommended for this type of lesion...

Os objetivos deste estudo foram comparar técnicas cirúrgicas e efeitos do n-butil 2-cianoacrilato e da membrana amniótica bovina na reparação de lesões perfuradas em córneas. Sessenta coelhos da raça Nova Zelândia Branca foram submetidos à ceratoplastia penetrante sob anestesia geral. O grupo 1 (G1) foi tratado com n-butil 2-cianoacrilato; o grupo 2 (G2) recebeu um fragmento de membrana amniótica pela câmara anterior e aplicação de n-butil 2-cianoacrilato sobre a lesão; o grupo 3 (G3) foi tratado com a mesma técnica aplicada ao G2, adicionando-se uma bandagem de membrana amniótica cobrindo a córnea e suturada à região do limbo; e o grupo 4 (G4) foi tratado com membrana amniótica suturada nas bordas da lesão e bandagem de membrana amniótica suturada na região do limbo. Foram realizados exames clínico, histológico e histomorfométrico. A membrana atuou como barreira contra o extravasamento do humor aquoso nos grupos 2 e 3, manteve a superfície seca para posterior aplicação do adesivo e impediu o contato do adesivo com as estruturas intraoculares. Os grupos tratados com o adesivo associado à membrana amniótica demonstraram melhores resultados do que aqueles tratados com cada material isoladamente. Assim, a combinação da membrana com o adesivo é indicada neste tipo de lesão...

Comparison of the pig and feline models for full thickness corneal transplantation.

PURPOSE: The goal of this study was to report on the advantages and limitations of the pig and feline models for experimental in vivo corneal transplantation. METHODS: Ten healthy domestic pigs and ten healthy cats were used. Full thickness penetrating keratoplasty was performed using autologous (eight cases), allogeneic (seven cases) or human xenogeneic (three cases) tissue. In two other cases, the inflammatory response to partial thickness trephination (without transplantation) was evaluated. Eyes were assessed daily before and after surgery by slit-lamp, pachymetry, and tonometry. A transparency score ranging from 0 (opaque graft) to 4 (clear graft) was used, based on the slit-lamp examination. Optical coherence tomography, histology, and electron microscopy were performed postmortem. RESULTS: In the pig, the mean (±SD) transparency score for the eight full thickness grafts was 0.88 ± 0.99, ranging from 0 to 3. In the feline model, the mean transparency score for the seven uncomplicated grafts was 3.93 ± 0.19, ranging from 3.5 to 4. Both negative controls without endothelium remained opaque at all time. Intraoperative tendency for iris incarceration into the wound, rapid corneal swelling, suture cheese wiring, and postoperative intraocular inflammation were the main factors jeopardizing the functional success of the corneal transplant in the pig model. CONCLUSION: Suboptimal functional results were obtained after full thickness corneal transplantation in the pig model, while in the feline model, the same protocol yielded uneventful surgeries and clear transplants, with functional results similar to those achieved in human subjects.

Penetrating keratoscleroplasty and bimodal grafting for treatment of limbal melanocytoma in a dog.

A 6-year-old, male neutered, German Shepherd dog presented for evaluation of a dark limbal mass OS. Based on the signalment and clinical findings, a presumptive diagnosis of limbal melanocytoma was made. Additionally, OU demonstrated corneal changes consistent with chronic superficial keratitis. Full thickness en bloc resection of the limbal mass was followed with reconstruction and grafting using both frozen cornea and bulbar conjunctiva. Nitrous oxide cryotherapy was utilized as an adjunctive modality for residual neoplastic cell destruction. Histopathologic evaluation confirmed the presumptive diagnosis. At 18 months postoperatively, there was no evidence of recurrence of the limbal melanocytoma. The dog was treated long-term with both topical steroid and tacrolimus 0.03% for control of the chronic superficial keratitis.

Heterologous penetrating keratoplasty for treatment of a corneal sequestrum in a cat.

A corneal sequestrum was diagnosed in an 8-year-old, neutered male Burmese cat. A heterologous penetrating keratoplasty (PK) (fresh canine corneal tissue) was performed to restore a clear visual axis. A heterograft was selected in order to decrease the risk of viral transmission as a screened donor was not available. One month postoperatively the graft was vascularized and opaque. The owner failed to return for recheck examinations until 16 months postoperatively at which time only a faint central nebula remained.

Acute bullous keratopathy in a domestic shorthair.

A 14-year-old cat was presented for corneal rupture of the right eye and bulla formation of the left cornea. It was diagnosed with acute bullous keratopathy, based on clinical and histopathologic examination. This is a rare condition of unknown origin in cats; it was treated successfully with bilateral conjunctival pedicle grafts.

Penetrating keratoplasty in a California Brown Pelican.

Fresh homologous penetrating keratoplasty (PK) was performed on the left cornea of a young adult female California Brown Pelican (Pelecanus occidentalis) for the treatment of vision-threatening corneal scarring and granulation tissue. The procedure appeared to be highly successful based on short-term clinical follow-up and histopathology results. However, the patient died from unrelated causes before long-term follow-up could be obtained.

Surgical correction of a corneal perforation in an alpaca (Lama pacos).

Likely because of trauma, an adult alpaca (Lama pacos) sustained a corneal perforation with a prolapsed iris. Because of the severity of the lesion, a pedicle conjunctival graft was performed. The structural integrity of the cornea was reestablished, and 10 mo postoperatively, the affected eye appeared to have good vision and only a small corneal scar remained.

Surgery of the cornea.

Corneal surgery is a common and essential part of veterinary ophthalmology and ranges from simple linear keratotomy for indolent ulcers to penetrating keratoplasty for restoration of optical clarity. Success in corneal surgery relies on an understanding of corneal anatomy, physiology and wound healing, meticulous attention to detail, microsurgical equipment and techniques, and use of appropriate preoperative, intraoperative, and postoperative medications. Surgical management of corneal disease is indicated for corneal ulceration, excision of a mass lesion, reconstructive procedures, therapeutic indications, optical restoration, and cosmetic purposes.

Penetrating keratoplasty for treatment of recurrent squamous cell carcinoma of the cornea in a horse.

Squamous cell carcinoma involving the cornea and conjunctiva of the left eye in a 14-year-old horse was treated by superficial keratectomy in combination with beta-radiation and radiofrequency hyperthermia. The tumor recurred 4 months later in the central cornea at the edge of the previous keratectomy site. Penetrating keratoplasty was performed in an effort to remove the tumor and retain a visual eye. The eye was visual 13 months after surgery. Mild fibrosis and vascularization were observed in the area of the penetrating keratoplasty.