Veterinary Ophthalmology Research Articles

Sub-Tenon's anesthesia in equine cataract surgery and vitrectomy: a retrospective case series (2018-2022).

A retrospective data analysis was performed on 17 eyes from 13 horses which underwent a sub-Tenon's injection to facilitate phacoemulsification or pars plana vitrectomy under general anesthesia between 2018 and 2022. All procedures were performed by the same veterinary ophthalmologist. Seven eyes received a sub-Tenon's dose of 7 ml lidocaine (XylocainÒ, 2 % lidocaine hydrochloride, Germany, Aspen Germany GmbH), and 10 eyes received 7 ml mepivacaine (MepinaestÒ purum 2 %, mepivacaine hydrochloride, Switzerland, Gebro Pharma GmbH). Statistical analysis compared onset and duration of globe centralization and pupil mydriasis between the two groups. Intraoperative and postoperative complications were also assessed. Mepivacaine had a significantly later onset of action regarding globe centration and mydriasis (8,9 minutes vs. 6 minutes), but also a significantly longer duration of globe centration than lidocaine (31,5 minutes vs. 15,6 minutes). There were no statistically relevant differences between solutions regarding duration of pupil dilation (40,4 minutes for 2 % lidocaine vs. 69,2 minutes for 2 % mepivacaine). Chemosis occurred in all 17 eyes. Surgical complications included corneal epithelial defects (5), retinal detachment (5), lens opacification (5), temporary blindness during recovery (3) and glaucoma (2). Sub-Tenon's anesthesia is a feasible alternative to systemic neuromuscular blockade and retrobulbar block anesthesia for surgical procedures on the equine globe. A controlled prospective in vivo study is needed to further evaluate effects and risks.

Interexaminer agreement of gonioscopy examinations in dogs using the European College of Veterinary Ophthalmologists Hereditary Eye Diseases grading scheme.

Prospective observational study with preregistered study protocol to assess interexaminer agreement using the 2022 European College of Veterinary Ophthalmologists Hereditary Eye Disease (ECVO-HED) gonioscopy grading scheme. Sixty client-owned dogs presented for gonioscopy as part of the required certification process prior to breeding. Two ECVO diplomates with comparable clinical experience performed gonioscopy with a Koeppe gonioscopy lens and slit-lamp biomicroscope at 10x magnification on all eyes in a randomized fashion. One hundred and eighteen of 120 eyes (60 dogs) were included. In 110/118 eyes (93%), both examiners provided the same breeding recommendation (yes/no). This translated into an agreement on the final breeding recommendation in 58/60 dogs (97%). Examiners disagreed on pectinate ligament abnormality (PLA) grading in 19/118 eyes and iridocorneal angle width (ICAW) grading in 9/118 eyes. PLA grading disagreement was mostly observed between neighboring grades. Disagreement between PLA and ICAW grading sometimes occurred within the same eye accounting for an observed disagreement in iridocorneal angle abnormality (ICAA) grading in 19/118 eyes in total. Cohen's kappa was Κ = 0.62 (95% TI 0.34-0.89), whereas maximum kappa was maxΚ = 0.82 (95% TI 0.59-1). Mixed model analysis suggested no significant examiner influence on breeding recommendations (OR 0.17; 95% CI 0.02-1.12, p = .09). Although examiners disagreed on ICAA grading in 19/118 eyes, this resulted in a different breeding recommendation (yes/no) in eight eyes and in two dogs only. Therefore, the use of the 2022 ECVO-HED gonioscopy grading scheme seems to result in examiners providing the same breeding recommendations in most cases.

Reconstruction of deep and perforating corneal defects in dogs-A review (Part II/III): Biomaterials and keratoprosthesis.

The surgical reconstruction of severe corneal ulcers is a common and crucial component of the clinical practice of veterinary ophthalmology. Numerous surgical techniques are used in dogs for corneal reconstruction, and these techniques may be categorized by the material used to repair the corneal lesion. The first part of the present review described procedures that utilize autogenous ocular tissues, homologous donor tissues, and heterologous donor tissues. In this second part of the review, the categories of biomaterials and keratoprosthetics will be summarized. Biomaterials that are reported for use in dogs include amniotic membrane, porcine urinary bladder acellular matrix, porcine small intestinal submucosa, acellular porcine corneal stroma, and other miscellaneous soft tissue and cartilage grafts (e.g., preserved equine renal capsule, autologous omentum, autologous buccal mucosa membrane, bovine pericardium, and homologous peritoneum). Descriptions of keratoprosthesis surgery in dogs are currently limited, but the use of artificial corneal transplants hold promise for dogs with severe, vision-compromising corneal disease that is not amenable to other reconstruction techniques. This review describes the results of experimental studies evaluating these graft materials in dogs, and it will summarize the findings and outcomes of the clinical articles published in each material category. Reporting inconsistencies and areas where additional research is required will be highlighted to help guide future studies in this area. A major aim of this review is to help identify potential subjects that could be evaluated in future investigations and that might lead to refinements in clinical practice.

Reconstruction of deep and perforating corneal defects in dogs-A review (Part III/III): The use of corneal sutures and reporting of ocular discomfort.

The surgical reconstruction of severe corneal disease is a common and crucial component of the clinical practice of veterinary ophthalmology. The first part of the present review described procedures that utilize autogenous ocular tissues, homologous donor tissues, and heterologous donor tissues in dogs, while the second part reviewed the use of biomaterials and keratoprosthetics in this species. This third part is dedicated to the review of the use of corneal sutures including suture type and suture pattern in corneal reconstruction of small animals including dogs and cats. The review also focused on the way studies report postoperative ocular discomfort/pain and how this is treated. Lastly, the author briefly presents the simple but effective techniques available to bury corneal knots for corneal reconstructive surgery in small animal patients, such as the "tugging" and "deep-superficial-superficial-deep" methods for simple interrupted sutures, and the adaptation of the latter for simple continuous sutures.

Anatomical structure of the orbits of the European beaver (Castor fiber)

Understanding the specifics of the orbit of each species is a fundamental and crucial step in developing veterinary ophthalmology. This article describes the bone structure, foramina piercing the bones, and the shape of the orbit in the European beaver (Castor fiber). Additionally, a morphometric analysis of the orbit was conducted, measuring its height, width, and depth, and the orbital index was calculated. A total of 27 skulls of this species were used for the study. It was shown that the average length and depth of the orbit were greater in females, while the average width was comparable in both sexes. Males, however, had a higher average orbital index. The observed regularities, assessed with a T-test, showed statistically significant differences between individuals. These results are the first step towards developing reference values for the discussed dimensions for this species, which will allow for the assessment of the correctness of the orbit structure of the European beaver.

Diagnosis of ophthalmologic diseases in canines based on images using neural networks for image segmentation

The primary challenge in diagnosing ocular diseases in canines based on images lies in developing an accurate and reliable machine learning method capable of effectively segmenting and diagnosing these conditions through image analysis. Addressing this challenge, the study focuses on developing and rigorously evaluating a machine learning model for diagnosing ocular diseases in canines, employing the U-Net neural network architecture as a foundational element of this investigation.Through this extensive evaluation, the authors identified a model that exhibited good reliability, achieving prediction scores with an Intersection over Union (IoU) exceeding 80 %, as measured by the Jaccard index. The research methodology encompassed a systematic exploration of various neural network backbones (VGG, ResNet, Inception, EfficientNet) and the U-Net model, combined with an extensive model selection process and an in-depth analysis of a custom training dataset consisting of historical images of different medical symptoms and diseases in dog eyes.The results indicate a fairly high degree of accuracy in the segmentation and diagnosis of ocular diseases in canines, demonstrating the model's effectiveness in real-world applications. In conclusion, this potentially makes a significant contribution to the field by utilizing advanced machine-learning techniques to develop image-based diagnostic routines in veterinary ophthalmology. This model's successful development and validation offer a promising new tool for veterinarians and pet owners, enhancing early disease detection and improving health outcomes for canine patients.

Mesenchymal stem cell therapy in veterinary ophthalmology: clinical evidence and prospects.

Mesenchymal stem cell (MSC) therapy presents a promising strategy for treating various ocular conditions in veterinary medicine. This review explores the therapeutic potential of MSCs in managing corneal ulcers, immune-mediated keratitis, chronic superficial keratitis, keratoconjunctivitis sicca, retinal degeneration, and ocular burns in feline, equine, and canine patients. Studies have demonstrated the immunomodulatory and regenerative properties of MSCs, highlighting their ability to mitigate inflammation and promote tissue regeneration. Experimental studies have shown the potential of MSC therapy in reducing corneal opacity and vascularization, indicating significant therapeutic advantages. Delivery methods play a crucial role in optimizing the therapeutic efficacy of MSCs in ocular diseases. Various delivery methods, such as intravitreal injection, subconjunctival injection, topical administration, and scaffold-mediated delivery, are being explored to optimize MSC delivery to the target ocular tissues. Clinical trials have shown significant improvements in clinical signs following MSC therapy, underscoring its efficacy in treating ocular diseases. Additionally, tissue engineering approaches incorporating MSCs, growth factors, and scaffolds offer innovative strategies for corneal regeneration and tissue repair. Despite challenges such as standardization of protocols and long-term safety assessment, ongoing research endeavours seek to unlock the full therapeutic potential of MSC therapy in ocular diseases. Future prospects in MSC therapy involve exploring scaffold and hydrogel-based approaches and cell-free therapies leveraging the bioactive molecules released by MSCs. Continued research and development efforts are essential to unlock the full therapeutic potential of MSCs and realize their transformative impact on ocular diseases in veterinary patients.

Training Veterinary Ophthalmology Residents on Cataract Surgery (Part A: Diplomate's Survey).

Training Veterinary Ophthalmology Residents on Cataract Surgery (Part A: Diplomate's Survey).

Advances in veterinary ophthalmology: Acellular protein matrix from tilapia skin (Oreochromis Niloticus) in the recovery of corneal ulcers in dogs and cats

The acellular protein matrix from tilapia skin has excellent biomechanical properties, lack of immunogenicity and high biocompatibility in vitro and in vivo. Therefore, it provides an environment conducive to cell regeneration, specifically in more invasive and delicate applications, such as the recovery of corneal ulcers in dogs and cats. The objective of this literature review is to present the use of the scaffold as a new approach in veterinary ophthalmology in the treatment of corneal injuries in relation to conventional methods. When applied to corneal ulcers, the biomaterial acts as a tissue scaffold, facilitating cell migration, promoting angiogenesis and minimizing the inflammatory response; thus, significantly accelerating the healing process. It also improves corneal transparency, reduces recovery time and reduces post-treatment complications. Clinical trials involving dogs and cats have had significant success, demonstrating the applicability and effectiveness of this innovation in the context of veterinary ophthalmology. This study highlights both the effectiveness of the tilapia skin scaffold and emphasizes its potential to transform clinical practice by providing a sustainable, affordable and pioneering approach to treating corneal ulcers in small animals.

Synthetic and Natural Biomaterials in Veterinary Medicine and Ophthalmology: A Review of Clinical Cases and Experimental Studies.

In recent years, there has been a growing interest in 3D printing technology within the field of bioengineering. This technology offers the ability to create devices with intricate macro- and micro-geometries, as well as specific models. It has particularly gained attention for its potential in personalized medicine, allowing for the production of organ or tissue models tailored to individual patient needs. Further, 3D printing has opened up possibilities to manufacture structures that can substitute, complement, or enhance damaged or dysfunctional organic parts. To apply 3D printing in the medical field, researchers have studied various materials known as biomaterials, each with distinct chemical and physical characteristics. These materials fall into two main categories: hard and soft materials. Each biomaterial needs to possess specific characteristics that are compatible with biological systems, ensuring long-term stability and biocompatibility. In this paper, we aim to review some of the materials used in the biomedical field, with a particular focus on those utilized in veterinary medicine and ophthalmology. We will discuss the significant findings from recent scientific research, focusing on the biocompatibility, structure, applicability, and in vitro and in vivo biological characteristics of two hard and four soft materials. Additionally, we will present the current state and prospects of veterinary ophthalmology.

Annual Scientific Meeting of the European College of Veterinary Ophthalmologists, Amsterdam, The Netherlands, May 30 - June 2, 2024.

Annual Scientific Meeting of the European College of Veterinary Ophthalmologists, Amsterdam, The Netherlands, May 30 - June 2, 2024.

The argument for two-handed cataract surgery in veterinary ophthalmology.

Despite access to contemporary phacoemulsification technology and the strong shift to two-handed nucleofractis techniques in human medicine, a one-handed, single incision approach has persisted among Diplomates of the American College of Veterinary Ophthalmologists. The perpetuation of techniques such as bowl-sculpting one-handed phacoemulsification in veterinary medicine is multifactorial; it is likely associated with the lack of two-handed training in residency programs, the challenges of learning on complex cases, the ease of teaching one-handed versus two-handed techniques to a resident, and the lack of specific instrumentation available designed for larger lens size, among other factors. Additionally, variation in globe and palpebral fissure size in veterinary patients complicates the training of cataract surgery. Finally, many mentors or mentors' mentors, were trained alongside previous generations of MD surgeons who performed bowl sculpting techniques during the transition from extracapsular cataract extraction to phacoemulsification, and understandably, are not comfortable teaching a two-handed technique consistently. The authors have observed an unwillingness to convert from one-handed to two-handed technique in the post-residency career for most veterinary ophthalmologists; this could be due to the high expectations becoming a specialist, especially when the stakes are as high as in phacoemulsification. Therefore, the authors advocate for hands-on training in multiple nucleofractis techniques, including two-handed methods during residency training. Simply put, if residents are not trained and comfortable with two-handed techniques by the end of residency, they are less likely to make further changes later in their career. In this article, we aim to explore the proposed rates of one-handed versus two-handed mentors currently teaching veterinary phacoemulsification, the history of cataract surgery, and to discuss the benefits of two-handed nucleofractis techniques. The authors will also illustrate and provide videos as well as some tools for veterinary ophthalmologists wishing to learn two-handed techniques.

Investigating the Bactericidal Activity of an Ocular Solution Containing EDTA, Tris, and Polysorbate 80 and Its Impact on the In Vitro Efficacy of Neomycin Sulfate against Staphylococcus aureus: A Preliminary Study.

In the current context of emerging and spreading antimicrobial resistance in human and animal infections, new strategies need to be developed to improve the efficacy of commonly prescribed antibiotics and preserve more critical compounds for multi-drug-resistant infections. This preliminary study aimed at evaluating the benefits of an eye cleaning solution containing 0.1% EDTA, 0.02% Tris, and 0.1% Polysorbate 80 in veterinary ophthalmology. A first in vitro study was performed to assess the bactericidal activity of the test solution against Staphylococcus aureus and Pseudomonas aeruginosa strains. A second in vitro study evaluated the impact of the test solution on the antimicrobial activity of neomycin against Staphylococcus aureus. The test solution alone did not show bactericidal activity against Staphylococcus aureus and Pseudomonas aeruginosa. The test solution seemed to increase the activity of Neomycin Sulfate against Staphylococcus aureus. These findings warrant further research to better characterize the impact on the bactericidal activity of antimicrobials used in veterinary ocular surface infections of the solution containing 0.1% EDTA, 0.02% Tris, and 0.1% Polysorbate 80 as well as of each individual ingredient for a thorough understanding of how this test solution could provide a new strategy to address the growing antimicrobial resistance issue worldwide.

Partial incision blunt scissors lamellar keratectomy under topical anesthesia for the treatment of presumed calcific corneal degeneration in dogs.

The aim of the study was to investigate clinical features of lamellar keratectomy for presumed calcific corneal degeneration in a population of geriatric dogs using blunt scissors dissection under topical anesthesia. Retrospective analysis of dogs with clinically diagnosed calcific degeneration treated by keratectomy under topical anesthesia between 2015 and 2021 at two veterinary ophthalmology practices was performed. Descriptive data regarding signalment, concurrent systemic and ocular disease, complications, healing time, and recurrence were collected. Kaplan-Meier survival analysis was performed to calculate 1-year recurrence probability. Sixty-five eyes in 57 dogs met inclusion criteria. All 54 eyes with follow-up healed within a median of 14 days (7-74), including 17 with complicating factors of infection or deep stromal ulceration. Globe rupture occurred intraoperatively in three eyes (4.6%), for which subsequent conjunctival graft was performed. Calculated 1-year recurrence probability from 47 eyes followed long term was 25%. Multivariate Cox proportional hazard modeling showed a significant association between documented systemic disease and time to recurrence (p = .035), irrespective of topical EDTA use (p = .432). Median follow-up time available for all cases was 249 days. Blunt lamellar dissection with corneal scissors can be performed in dogs under topical anesthesia, yielding healing times and recurrence comparable to previously reported treatments for calcific corneal degeneration. Globe rupture is an inherent risk of both the disease and procedure and occurred in 4.6% of treated eyes. This approach expands non-anesthetic treatment options for affected patients but should only be performed with advanced microsurgical training and client counseling on individual risk and benefit.

Abstracts: Annual Meeting of the European College of Veterinary Ophthalmologists, Rhodes, Greece, May 18-21, 2023.

Abstracts: Annual Meeting of the European College of Veterinary Ophthalmologists, Rhodes, Greece, May 18-21, 2023.

Prevalence and antibiotic resistance in bacterial isolates of dogs with ulcerative keratitis in São Paulo State, Brazil.

Identify microorganisms present in canine eyes affected by ulcerative keratitis and assess its resistance profile to available antimicrobial drugs. Samples were collected from 88 canine eyes that exhibited ulcerative keratitis. They were identified using MALDI-TOF and subjected to antimicrobial susceptibility testing by disk diffusion. Among the assessed subjects, brachycephalic dogs accounted for 74.48% (50/83) of the evaluated canines. Among the 88 evaluated eyes, 90.9% (80/88) showed positive cultures, with 11.33% (10/88) of the samples isolating more than one species of bacteria. Of all bacterial isolates identified (90), Gram-positive bacteria accounted for 63.33% (57/90), while Gram-negative bacteria constituted 36.66% (33/90), with predominance of Staphylococcus spp. at 35.55% (32/90) being, Staphylococcus pseudintermedius at 68.75% (22/32), and Pseudomonas aeruginosa at 15.55% (14/90), respectively. Staphylococcus spp. exhibited resistance to penicillin (89.29%), sulfadiazine and trimethoprim (60.71%), and tetracycline (67.86%), while doxycycline (88.89%), cefotaxime (85.71%), chloramphenicol (82.14%), gentamicin, and moxifloxacin (78.57%) showed the highest sensitivity rates. Pseudomonas aeruginosa displayed sensitivity (100%) to gentamicin and imipenem, and resistance (8.33%) to norfloxacin, ciprofloxacin, and cefepime. Similarly, the Enterobacteriaceae family showed higher sensitivity to amikacin and gentamicin (88.89%), imipenem (88.24%), and levofloxacin (87.5%), with pronounced resistance to amoxicillin-clavulanate (50%) and cefazolin (47.06%). This highlights multiresistance in 23.33% (21/90) of the isolates. The most isolated species in canine ulcerative keratitis are S. pseudintermedius and P. aeruginosa. However, other species were also isolated, demonstrating diversity in ocular microbiota infection. There is a high-rate multidrug resistance associated with canine ulcerative keratitis. Nevertheless, these strains exhibited sensitivity to antimicrobials commonly used in veterinary ophthalmology.

Evaluation of photoactivated chromophore for keratitis-corneal cross-linking (PACK-CXL) in feline infectious keratitis-patient demographics, treatment protocols, risk factors, and treatment outcome: a retrospective study.

To describe patient demographics and treatment protocols in a population of feline patients undergoing photoactivated chromophore for keratitis-corneal cross-linking (PACK-CXL) as an adjunctive treatment for infectious keratitis. Furthermore, to determine the proportion of PACK-CXL treatment success in the population studied, explore risk factors for treatment failure, and provide recommendations for future PACK-CXL clinical studies. Records from four veterinary ophthalmology practices were reviewed to identify eligible patients and extract data. Recorded variables included patient-related factors, ocular examination findings, PACK-CXL protocol parameters, and treatment outcome. Records for 153 cats (154 eyes) were included. Median age in the treatment success group was 8 years (interquartile range (IQR) 4-12), with a median ulcer depth of 30% (IQR 30-40). Median age in the treatment failure group was 10.5 years (IQR 4.75-12) with a median ulcer depth of 45.9% (IQR 30-75). Persian cats were the most represented brachycephalic breed (52 out of 64 cats). Modified PACK-CXL protocols were used, including fast energy delivery (134 eyes), and increased fluence (52 eyes). The overall proportion of success was 88% (95% CI 84-93), which was variable between clinics. Eighty-two of 89 mesocephalic cat eyes (92%), and 54 of 65 brachycephalic cat eyes (83%) were classified as treatment successes. PACK-CXL appeared to be a useful, adjunctive therapeutic modality for the treatment of infectious keratitis in the feline patient population presented here. Brachycephalic cats, older cats, and those with deeper ulcers may be at increased risk for treatment failure.

Techniques for subretinal injections in animals.

Subretinal injections are not commonly performed during clinical treatment of animals but are frequently used in laboratory animal models to assess therapeutic efficacy and safety of gene and cell therapy products. Veterinary ophthalmologists are often employed to perform the injections in the laboratory animal setting, due to knowledge of comparative ocular anatomy between species and familiarity with operating on non-human eyes. Understanding the different approaches used for subretinal injection in each species and potential complications that may be encountered is vital to achieving successful and reproducible results. This manuscript provides a summary of different approaches to subretinal injections in the most common animal model species, along with information from published literature and experience of the authors to educate novice or experienced surgeons tasked with performing these injections for the first time.

Schirmer tear test-1 with open or closed eyelids: An evaluation in brachycephalic and nonbrachycephalic dogs.

Assess aqueous tear production when measured with the dogs' eyelids open or closed. Thirty healthy dogs (15 Shih Tzus, 15 Labrador retrievers) were recruited. With the order of testing randomized for each dog, two sessions (separated by 30 min) of STT-1 testing were performed with the dogs' eyelids closed or open. Schirmer strip wetness (every 10 s for 60 s) and number of time(s) the strip dislodged during testing were recorded in each eye. Preferred STT-1 method was surveyed via a global Listserv of the veterinary ophthalmology community. STT-1 values were significantly higher in closed versus open eyes in Shih Tzus (18.6 ± 2.7 mm/min vs. 16.3 ± 2.5 mm/min; p = .002) and Labrador retrievers (21.6 ± 2.9 mm/min vs. 17.8 ± 3.2 mm/min, p < .001), findings that were also significant at times <60 s for either breed (p ≤ .004). Schirmer strips dislodged from six dogs with open eyelids and no dogs with closed eyelids. Maximal STT-1 difference with closed versusopen eyelids was 13 mm/min in Labrador retrievers and 7 mm/min in Shih Tzus. Survey results from 275 veterinarians showed STT-1 performed with "closed eyelids" (38.5%), "open eyelids" (26.9%), or "never paid attention, sometimes closed, sometimes open" (34.6%). Eyelids status (closed or open) during STT-1 testing had a significant impact on aqueous tear secretion in brachycephalic and nonbrachycephalic dogs, highlighting the importance of consistency when repeating STT-1 in a canine patient. STT-1 differences are likely due to sustained reflex tearing throughout the test duration when the dogs' eyelids are closed.

Poster Abstracts: 53rd Annual Meeting of the American College of Veterinary Ophthalmologists, Palm Springs, CA, USA October 26-29, 2022.

Poster Abstracts: 53rd Annual Meeting of the American College of Veterinary Ophthalmologists, Palm Springs, CA, USA October 26-29, 2022.