Gross anatomy and morphometric evaluation of the canine lacrimal and third eyelid glands

Morphology and Histology of the Orbital Region and Eye of the Asiatic Black Bear (Ursus thibetanus)—Similarities and Differences within the Caniformia Suborder

In this study, we present first data concerning the morphological observations of the orbital region, eye tunics, upper and lower eyelids, superficial gland of the third eyelid with the third eyelid, and lacrimal gland in captive adult male Asiatic black bear. The following research methods were used in the work: the eyeball morphometry, the orbital region description, macroscopic description, morphometric and histological analysis of the eye tunics and selected the accessory organs of the eye (Fontana–Masson, hematoxylin & eosin (H&E), Methyl-green-pyronin Y (MGP Y), Movat pentachrome, and picro-Mallory trichrome) as well as histochemical examination (PAS, AB pH 1.0, AB pH 2.5, AB pH 2.5/PAS and HDI). The eyeball of the Asiatic black bear was a spherical shape, while the periorbita was funnel/conical-shaped and the eye socket was of the open type. The cornea was absent of the Bowman’s membrane similar to all domestic dogs and some wild dogs. There were palisades of Vogt in the corneal limbus epithelium similar to the Canidae. Degenerative choroidal tapetum lucidum similar to ranch mink (Mustelidae) has been found. The pupil was big and round in shape. The ciliary muscle, dilatator and sphincter muscle were well developed, similar to the pinnipeds. The lens was biconvex round, similar to the Canidae. The retina was composed similarly to the diurnal terrestrial carnivores. In both eyelids were observed very well-developed tarsal glands, ciliary glands and sebaceous glands. The orbital zone in the eyelids was characterized by lymphoid follicles, diffuse lymphocytes and specialized high endothelial venules. In the anterior palpebral margin of the upper eyelid, soft and short eyelashes were observed, while in the lower eyelids they were absent. The third eyelid was T-shaped and composed of the hyaline tissue, and it contained CALT, similar to that in Canidae. The superficial gland of the third eyelid was a multilobar alveolar branched complex with seromucous nature, while the lacrimal gland was also a multilobar acinar branched complex gland, but producing a mucous–serous secretion. The results of our research indicate that the features of the anatomy of the eye and orbital region in Asiatic black bear are also typical of the Ursidae family. Moreover, a detailed analysis of the morphological eye region may be useful in comparative studies and veterinary diagnostics in this bear species.

Anatomy of the nasolacrimal duct in Persian cats determined by computed tomographic dacryocystography

OBJECTIVE

This study sought to describe the anatomical characteristics of the nasolacrimal duct of Persian cats as observed by computed tomographic dacryocystography.

ANIMAL STUDIED

Ten cats weighing 3-6 kg (three live cats and seven cadaveric specimens).

PROCEDURES

The animals were submitted to bilateral computed tomographic dacryocystography, totaling 20 nasolacrimal ducts. Dorsal, sagittal, and transverse planes were studied. Two additional skulls were also dissected following latex injection into the nasolacrimal duct. The length and width of the nasolacrimal duct and lacrimal canaliculi, and the distance between the nasolacrimal duct and the root of the upper canine tooth at the point of closest proximity were measured.

RESULTS

The nasolacrimal duct followed a convoluted course, particularly in the middle and rostral portions. Duct stenosis (width reduction equal to or >75%) and dilations (width increase equal to or >50%) were also detected, particularly in the rostral portion. Nasolacrimal duct length and width ranged from 1.3 to 1.5 cm and 1.5 to 2.3 mm, respectively. Mean lacrimal canaliculus length and width corresponded to 3.1 mm and 0.4 mm, respectively. Mean distance from the nasolacrimal duct to the canine tooth was 2.4 mm. The root of this tooth interfered with the course of the nasolacrimal duct.

CONCLUSION

This study provided anatomical information for clinical assessment of the nasolacrimal drainage system in Persian cats.

Breed and conformational predispositions for prolapsed nictitating membrane gland (PNMG) in dogs in the UK: A VetCompass study

Background

Prolapsed nictitating membrane gland (PNMG) is the most common disorder of the third eyelid in dogs. However, the epidemiology of PNMG in the wider dog population remains understudied.

Methods

Using de-identified clinical data from the VetCompass Programme, this cohort study aimed to report the prevalence, demographic and breed-related risk factors of PNMG in dogs attending UK primary care veterinary practices in 2016.

Results

There were 1,802 PNMG cases identified from 905,543 dogs, yielding an annual prevalence of 0.20% (95% confidence interval (CI) 0.19–0.21). The median age at first diagnosis was 0.63 years (IQR 0.33–1.98, range 0.11–18.00). Dogs aged under 1 year had 10.82 times the odds (95% CI 9.17–12.76) compared with dogs aged from 2 to under 4 years. Neutered animals had higher odds than entire animals within both sexes. Breeds with the highest odds of PNMG compared with crossbred dogs included Neapolitan Mastiff (odds ratio (OR) 34.26, 95%CI 15.92–73.75), English Bulldog (OR 24.08, 95% CI 20.62–28.13), Cane Corso (OR 14.66, 95% CI 8.18–26.28), Lhasa Apso (OR 12.37, 95% CI 10.26–14.92) and American Cocker Spaniel (OR 11.57, 95% CI 5.59–23.96). Purebred dogs had 1.43 times the odds (95% CI 1.26–1.63) of PNMG compared with crossbreed dogs. Breeds with brachycephalic skull conformation had 6.71 times the odds (95%CI 5.89–7.64) compared with breeds with mesocephalic skull conformation. Insured dogs had 1.89 times the odds (95% CI 1.65–2.16) compared with uninsured dogs.

Conclusions

This study reports the largest cohort of primary-care PNMG cases assembled to date. The results showing young age at diagnosis along with the breed, purebred and brachycephalic skull conformation predispositions suggest a hereditary involvement in PNMG development. These results may help to guide breeding strategies to reduce the prevalence of PNMG and improve welfare in predisposed individuals.

Epithelial lacrimal gland tumors in dogs and cats: Is the human WHO classification appropriate for animals?

Lacrimal gland tumors (LGTs) in dogs and cats are rare neoplasms that can affect either the nictitans (NLG) or the main lacrimal gland (MLG). A consistent classification scheme for canine and feline LGTs is lacking; however, the importance of a classification scheme for LGTs has been emphasized in the human literature, and an update to the World Health Organization (WHO) classification has recently been published. The aim of this study was to investigate the occurrence of different subtypes of canine and feline LGTs in accordance with the human WHO classification system. Epithelial LGTs (n = 46 tumors; 38 dogs, 8 cats) were reviewed and immunophenotyping for p63, CK14, SMA, calponin, CKAE1/AE3, and CK19 was performed. Consistent with previous literature reports, lacrimal carcinomas outnumbered adenomas in dogs and cats. Based on the WHO classification of human LGTs, the most common subtypes identified in dogs were pleomorphic, ductal, adenoid cystic, and epithelial-myoepithelial carcinoma. In cats, a lower number of subtypes was observed, and adenocarcinoma "not otherwise specified" (NOS) was the most frequent diagnosis. An uncommon case of feline epithelial-myoepithelial carcinoma was also observed. The application of the human WHO-LGT classification scheme to canine and feline tumors increased the diversity of diagnoses and allowed for the identification of numerous subtypes. Further studies to identify possible correlations between pathological subtypes and prognosis are warranted.

Anatomical study of the eye arterial blood supply in adult river buffalo (Bubalus bubalis)

Obtaining information about the eye arterial supply in the buffalo can be a criterion for ocular diseases diagnosis and give a morphological basis for even more researches on the related clinical surgery of this animal. The aim of the present study was to describe the course and branches of the arteries supplying the eye in the adult river buffalo (Bubalus bubalis). In this study, the heads of eight buffaloes were prepared from the public slaughterhouse and dissected to study the eye arterial supply. This research results showed that the eye blood supply in the buffalo originates from the external ophthalmic, internal ophthalmic, superficial temporal and malar arteries. The external ophthalmic artery was given rise to branches to take part in the ophthalmic rete mirabile formation and also given off lacrimal, external ethmoidal, supraorbital and ciliary arteries as well as muscular branches to supply the eye ball and extra-ocular muscles. The internal ophthalmic artery was one of the sources of lateral posterior long ciliary artery. The superficial temporal artery was detached off some branches to supply the lateral angle of inferior and superior eyelids as well as lacrimal branch to supply lacrimal gland. The malar artery was originated from the infra-orbital artery and its branches were supplied the medial angle of inferior, superior and third eyelids. There were no obvious differences between buffalo and yak regarding arteries supplying the eyes. However, there were minor differences between buffalo and oxen, sheep and goat and there were obvious differences between buffalo and camel and giraffe.

Anatomical and morphometric evaluation of the orbit, eye tunics, eyelids and orbital glands of the captive females of the South African painted dog (Lycaon pictus pictus Temminck, 1820) (Caniformia: Canidae)

In this study, we present the first data concerning the anatomical, morphometrical, histological and histochemical study of the orbit, eye tunics, eyelids and orbital glands in South African Painted Dogs (Lycaon pictus pictus). The study was performed using eyeball morphometry, analysis of the bony orbit including its morphometry, macroscopic study, morphometry, histological examination of the eye tunics and chosen accessory organs of the eye and histochemical analysis. The orbit was funnel shaped and was open-type. There was a single ethmoid opening for the ethmoid nerve on the orbital lamina. The pupil was round, while the ciliary body occupied a relatively wide zone. The iris was brown and retina had a pigmented area. The cellular tapetum lucidum was semi-circular and milky and was composed of 14–17 layers of tapetal cells arranged in a bricklike structure. In the lower eyelid, there was a single conjunctival lymph nodule aggregate. One or two additional large conjunctval folds were observed within the posterior surface of the upper eyelids. The superficial gland of the third eyelid had a serous nature. The third eyelid was T-shaped and was composed of hyaline tissue. Two to three conjunctival lymph nodul aggregates were present within the bulbar conjunctiva of the third eyelid. The lacrimal gland produced a sero-mucous secretion. A detailed anatomic analysis of the eye area in the captive South African Painted Dogs females showed the similarities (especially in the histological examination of the eyetunics and orbital glands) as well as the differences between the Painted dog and the other representatives of Canidae. The differences included the shape and size od the orbita with comparison to the domestic dog. Such differences in the orbit measurements are most likely associated with the skull type, which are defined in relation to domestic dogs. The presented results significantly expand the existing knowledge on comparative anatomy in the orbit, eye and chosen accessory organs in wild Canidae.

An eye on the dog as the scientist's best friend for translational research in ophthalmology: Focus on the ocular surface

Preclinical animal studies provide valuable opportunities to better understand human diseases and contribute to major advances in medicine. This review provides a comprehensive overview of ocular parameters in humans and selected animals, with a focus on the ocular surface, detailing species differences in ocular surface anatomy, physiology, tear film dynamics and tear film composition. We describe major pitfalls that tremendously limit the translational potential of traditional laboratory animals (i.e., rabbits, mice, and rats) in ophthalmic research, and highlight the benefits of integrating companion dogs with clinical analogues to human diseases into preclinical pharmacology studies. This One Health approach can help accelerate and improve the framework in which ophthalmic research is translated to the human clinic. Studies can be conducted in canine subjects with naturally occurring or noninvasively induced ocular surface disorders (e.g., dry eye disease, conjunctivitis), reviewed herein, and tear fluid can be easily retrieved from canine eyes for various bioanalytical purposes. In this review, we discuss common tear collection methods, including capillary tubes and Schirmer tear strips, and provide guidelines for tear sampling and extraction to improve the reliability of analyte quantification (drugs, proteins, others).

Anatomical, histological and computed tomography comparisons of the eye and adnexa of crab-eating fox (Cerdocyon thous) to domestic dogs

An understanding of species' morphological and physiological parameters is crucial to developing conservation strategies for wild animals kept in human care. Detailed information is lacking for crab-eating fox (Cerdocyon thous) eyes and adnexa. Therefore, the aim of this study was to describe anatomical, histological and computed tomography (CT) features of the eye and adnexa in crab-eating fox, compared to domestic dogs. CT of the eye and adnexa of one live animal and a frozen specimen was performed for anatomical identification. In addition, the heads of five animals of each species were fixed in 10% buffered formalin for gross anatomical description of the eye and adnexa using topographic dissection and exenteration techniques. All steps were photographed and features such as location, shape, and distances and relationships between structures were described. For histological evaluation, two eyes of each species were fixed in 10% buffered formalin, processed by routine paraffin inclusion technique and stained with hematoxylin and eosin. The CT scan was difficult to evaluate, mainly that of the frozen head, which did not provide good definition of the soft tissues; nevertheless, it demonstrated the potential for structure visualization and description. The gross anatomical and histological evaluations showed the presence of eyelashes on the upper eyelid and of upper and lower lacrimal points, an incomplete orbit with supraorbital ligament, slightly exposed sclera with discretely pigmented limbus and pigmentation throughout the conjunctiva, and a slit-shaped pupil. Hematoxylin and eosin staining demonstrated structural similarities between the crab-eating fox and domestic dog. Thus, the possibility of using the domestic dog as a study model for the preventive and therapeutic management of wild dogs kept in human care is demonstrated.

Ultrastructural morphology of goblet cells of the conjunctiva of dogs

OBJECTIVE

To describe the morphology of goblet cells of the eyelid conjunctiva in dogs using transmission and scanning electron microscopy.

ANIMAL STUDIED

Ten dogs, both male and female of different breeds, with no ocular changes were examined (20 eyes).

PROCEDURES

Ten samples of conjunctiva were collected and processed for scanning and transmission electron microscopy (SEM and TEM), while another 10 samples were stained with Schiff's periodic stain (SPA) and alcian blue, pH 2.5, and analyzed using light microscopy.

RESULTS

Scanning electron microscopy revealed several points of mucus extrusion in the free apical portion of the goblet cells as well as a wide distribution of lymphoid follicles and macrophages intermingling with the microvilli of palpebral epithelium cells. TEM revealed normal goblet cells that were predominantly oval with wide cytoplasm of different diameters, and large vesicles with heterogeneous granules and free edges, suggesting the release of mucus content onto the conjunctival surface. Cytoplasmic organelles, such as the Golgi apparatus, endoplasmic reticulum, and a high number of mitochondria were also observed. All the samples were positive for SPA and alcian blue staining.

CONCLUSION

This is the first study to evaluate the goblet cells of the eyelid conjunctiva in healthy dogs using electron microscopy techniques. These results are useful for comparing the palpebral conjunctiva of dogs without ocular changes to palpebral conjunctiva of dogs and other species with ocular changes.