Esmeralda Delgado

The ocular surface represents a unique microbial ecosystem continuously exposed to environmental microorganisms; however, the fungal component of the healthy equine ocular microbiome remains poorly characterized. This study aimed to characterize the ocular surface mycobiome of 12 clinically healthy Purebred Lusitano horses from three geographical regions in Portugal kept in two housing systems using Oxford Nanopore long-read sequencing and conventional fungal culture. Sequencing revealed a highly diverse fungal community with marked inter-individual variability. The most abundant genera were Wallemia, Podosphaera, Debaromyces, Aspergillus, Filobasidium, Kurtzmaniella, Metschnikowia, Malassezia and Spathaspora. Patterns of fungal community composition suggested that local environmental conditions may contribute to the observed inter-individual variability. Genera commonly associated with equine fungal keratitis, including Aspergillus, Fusarium and Penicillium, were detected in healthy horses irrespective of housing system. Overall, the healthy equine ocular surface was characterized by a diverse mycobiome dominated by environmentally associated fungi. There findings provide a baseline for future studies investigating ocular microbial dysbiosis, environmental determinants of fungal community structure, and equine ocular health.

Objective: To investigate the bacterial spectrum and antimicrobial susceptibility patterns of isolates obtained from canine corneal ulcers, assessing possible associations with breed, season, and multidrug resistance. Methods: A retrospective review was conducted on corneal ulcers from 112 dogs between May 2021 and June 2024 at a specialized veterinary ophthalmology clinic in Berlin, Germany. Bacteriological cultures and antimicrobial susceptibility tests (ASTs) were analyzed according to the Clinical and Laboratory Standards Institute (CLSI). Results: Brachycephalic breeds represented 79.5% of affected dogs. Positive bacterial growth was obtained in 79.5% (89/112) of samples, yielding 107 isolates. Gram‐positive organisms predominated (72.2%), mainly Staphylococcus pseudintermedius (27.8%) and β‐hemolytic Streptococcus (19.4%). Among 100 isolates tested, 59% were resistant to penicillins, while 71% were susceptible to aminoglycosides and fluoroquinolones, 73% to amoxicillin–clavulanate, and 78% to tetracyclines. Multidrug resistance (MDR) occurred in 27% of isolates. Conclusions: Staphylococcus pseudintermedius and β‐hemolytic Streptococcus were the main bacterial agents associated with infected canine corneal ulcers. The relatively high frequency of MDR isolates emphasizes the need for culture‐based therapy and ongoing regional surveillance to guide empirical antibiotic use.

Topical ophthalmic drug delivery targeting the posterior segment of the eye has become a key area of interest due to its non-invasive nature, safety, ease of application, patient compliance, and cost-effectiveness. However, achievement of effective drug bioavailability in the posterior ocular segment is a significant challenge due to unique ocular barriers, including precorneal factors and anatomical barriers, like the cornea, the conjunctiva, and the sclera. Successful ocular drug delivery systems require increased precorneal residence time and improved corneal penetration to enhance intraocular bioavailability. A promising strategy to overcome these barriers is incorporating drug penetration enhancers (DPEs) into formulations. These compounds facilitate drug delivery by improving permeability across otherwise impermeable or poorly permeable membranes. At the ocular level, they act through three primary mechanisms: breaking tear film stability by interfering with the mucous layer; disrupting membrane components such as phospholipids and proteins; and loosening epithelial cellular junctions. DPEs offer significant potential to improve bioavailability and therapeutic outcomes, particularly for drugs targeting the posterior segment of the eye. This review is focused on analyzing the current literature regarding the use of penetration enhancers in topical ocular drug delivery, highlighting their mechanisms of action and potential to revolutionize ophthalmic treatments.

Retinal diseases are characterized by progressive damage to retinal cells, leading to irreversible vision loss. Among these, glaucoma stands out as a multifactorial neurodegenerative disease involving elevated intraocular pressure, retinal ganglion cell apoptosis, and optic nerve damage, ultimately resulting in blindness in both humans and dogs. Stem cell-based therapies have emerged as a promising therapeutic option for such conditions due to their regenerative and neuroprotective potential. These therapies, particularly those based on mesenchymal stem cells, offer the potential to repair and protect retinal tissues through the bioactive molecules (growth factors, cytokines, chemokines) secreted, their secretome. However, research in this field, especially on the use of umbilical cord mesenchymal stem cells’ secretome, remains sparse. Most clinical trials focus on human glaucomatous patients, leaving a significant gap in veterinary patients’ application, especially in dogs, with additional research being needed to determine its usefulness in canine glaucoma treatment. Future studies should aim to evaluate these therapies across both human and veterinary contexts, broadening treatment possibilities for glaucoma.

Retinal diseases are characterized by progressive damage to retinal cells, leading to irreversible vision loss. Among these, glaucoma stands out as a multifactorial neurodegenerative disease involving elevated intraocular pressure, retinal ganglion cell apoptosis, and optic nerve damage, ultimately resulting in blindness in both humans and dogs. Stem cell-based therapies have emerged as a promising therapeutic option for such conditions due to their regenerative and neuroprotective potential. These therapies, particularly those based on mesenchymal stem cells, offer the potential to repair and protect retinal tissues through the bioactive molecules (growth factors, cytokines, chemokines) secreted, their secretome. However, research in this field, especially on the use of umbilical cord mesenchymal stem cells’ secretome, remains sparse. Most clinical trials focus on human glaucomatous patients, leaving a significant gap in veterinary patients’ application, especially in dogs, additional research being needed to determine its usefulness in canine glaucoma treatment. Future studies should aim to evaluate these therapies across both human and veterinary contexts, broadening treatment possibilities for glaucoma.

In humans, allergic conjunctivitis is a well described disease. In contrast, allergic conjunctivitis has not received much attention from the veterinary community so far. Canine allergic conjunctivitis (cAC) is one of the possible manifestations associated with canine atopic dermatitis (cAD), being often underdiagnosed and undertreated. Our aim is to contribute to disease characterization and clinical stagingfor cAC severity. A retrospective observational study including 122 dogs that underwent a complete ophthalmological and dermatological examinations and diagnosed with allergic conjunctivitis was conducted. A total of six ophthalmic clinical signs were considered for disease characterization and clinical staging: conjunctival hyperemia, chemosis, ocular pruritus, epiphora, seromucoid to mucopurulent discharge and keratitis, classified from 0 (absent) to 3 (severe). Scores comprised between 1–5 were considered mild, 6–10 moderate and 11–18 severe. The majority of dogs (64%) presented with moderate cAC followed by 24% of mild stages and only 12% of severe presentations. The severity of allergic conjunctivitis was not correlated to sex or age at the time of diagnosis and all presented with a bilateral form of the disease. Chemosis (84%), hyperemia (83%) and ocular pruritus (79%) was observed in 55% of the cases. Seromucoid to mucopurulent discharge (62%) and epiphora (69%) were less frequent, with keratitis being the least encountered clinical sign (15%). The degree of keratitis showed a positive correlation with both severity and chronicity of cAC (rho = 0.21–0.29, p ≤ 0.02)). Severity of cAD and cAD were not significantly correlated (p-value = 0.4). The triad hyperemia, chemosis and ocular pruritus, already known in human medicine to be a reliable way of diagnosing human allergic conjunctivitis, also proved to be important in cAC Mild forms of the disease may pass unnoticed, ocular pruritus being hard to assess in canine patients.The proposed standardized diagnostic approach and novel grading scheme for cAC may be of value for both veterinary ophthalmologists and dermatologists, as well as general practitioners.

The present work investigates the effects of chitosan-hyaluronic acid-epoetin beta (CS/HA-EPOβ) nanoparticles after topical ocular administration in a rat glaucoma model. Wistar Hannover rats (n = 24) were submitted to a complete ophthalmological examination and electroretinography, followed by glaucoma induction in their right eye on day 1 of the study. Treatment group (T) received CS/HA-EPOβ nanocarriers (n = 12), while the control group (C) received only empty ones. Electroretinography was repeated on day 3 (n = 24) and before euthanasia on day 7 (n = 8), 14 (n = 8), and 21 (n = 8), followed by bilateral enucleation and histological assessment. The animals showed good tolerance to the nanoformulation. Maximum IOP values on the right eye occurred shortly after glaucoma induction (T = 62.6 ± 8.3 mmHg; C = 63.6 ± 7.9 mmHg). Animals from the treated group presented a tendency for faster recovery of retinal electrical activity (p > 0.05). EPOβ was detected on the retina of all treated eyes using immunofluorescence. Control animals presented with thinner retinas compared to the treated ones (p < 0.05). Therefore, topical ocular administration of CS/HA-EPOβ nanoparticles enabled EPOβ delivery to the retina of glaucomatous rats and promoted an earlier retinal recovery, confirming EPOβ’s neuroprotective effects. The encouraging results of this preclinical study pave the way for new strategies for topical ocular administration of neuroprotective compounds.

Neuroprotection in glaucoma using epoetin beta (EPOβ) has yielded promising results. Our team has developed chitosan-hyaluronic acid nanoparticles (CS/HA) designed to carry EPOβ into the ocular globe, improving the drug’s mucoadhesion and retention time on the ocular surface to increase its bioavailability. In the present in vivo study, we explored the possibility of delivering EPOβ to the eye through subconjunctival administration of chitosan-hyaluronic acid-EPOβ (CS/HA-EPOβ) nanoparticles. Healthy Wistar Hannover rats (n = 21) were split into 7 groups and underwent complete ophthalmological examinations, including electroretinography and microhematocrit evaluations before and after the subconjunctival administrations. CS/HA-EPOβ nanoparticles were administered to the right eye (OD), and the contralateral eye (OS) served as control. At selected timepoints, animals from each group (n = 3) were euthanized, and both eyes were enucleated for histological evaluation (immunofluorescence and HE). No adverse ocular signs, no changes in the microhematocrits (≈45%), and no deviations in the electroretinographies in both photopic and scotopic exams were observed after the administrations (p < 0.05). Intraocular pressure remained in the physiological range during the assays (11–22 mmHg). EPOβ was detected in the retina by immunofluorescence 12 h after the subconjunctival administration and remained detectable until day 21. We concluded that CS/HA nanoparticles could efficiently deliver EPOβ into the retina, and this alternative was considered biologically safe. This nanoformulation could be a promising tool for treating retinopathies, namely optic nerve degeneration associated with glaucoma.

A 6‐year‐old male Yorkshire terrier presented due to sudden onset exophthalmos of the left eye. Ocular signs included conjunctival haemorrhage and third eyelid protusion. Physical examination revealed decreased ocular retropulsion and pain on opening the mouth. Skull CT demonstrated the presence of a retrobulbar mass. Transoral drainage of the retrobulbar space disclosed blood, but subsequently to this procedure profuse bleeding occurred from the incision site, while haematocrit levels decreased significantly. Coagulation tests showed a deficiency on the VIII and XII clotting factors, compatible with haemophilia A. As a consequence of exophthalmos, a severe exposure keratitis took place that rapidly evolved to perforation. After fresh frozen plasma administration, a transconjunctival enucleation was performed. Although uncommon, retrobulbar haematoma resulting from haemostatic defects should be included in the differential diagnosis of exophthalmos in dogs.