Microvascularization of the Third Eyelid in Dogs

The third eyelid protects the eye, contribute to the aqueous portion of the pre‐ocular film and its distribution over the corneal surface, as well as removal of foreign material from the anterior surface of the eye. It is rather vulnerable during fights and clinicians often have to perform surgery for third eyelid neoplasia. In dogs, this lid has a triangular shape, being widest at its free margin. It is vascularized by branches of the malar artery. Being of such importance as an adnexa of the eye, the authors concentrated their attention on its vascularization, which is not well defined. Methods: Scanning Electronic Microscopy of vascular corrosion casts and intact tissue. Observations: It was quite interesting to notice the presence of two patterns of vascularization inside the third eyelid. One can say that there are two segmental levels of vessels. In one of these there is a predominance of arteries and veins, while in the other a meshwork of third order arteries, capillaries and post‐capillary venules are present. In fact, the branch of the malar artery that reaches the base of the third eyelid divides into smaller branches that cross almost the complete length of the lid giving only a few collateral vessels, in a monopodical way, and only near the free margin of the lid is possible to observe dicothomical ramifications that became rather anastomotic (being anastomoses of type I and II are present) and contribute to the microvascular meshwork. This microvascular net is drained by post‐capillary venules and veins that empty as a brush into bigger veins that occupy the same segmental level as the third eyelid artery. Remarks: This uncommon angioarchitecture is probably an adaptation to the fact that in the medial canthus of the eye this lid has a smaller space and the way of obtaining an efficient vascularization is by going straight to the top of the lid.     

The Arterial Supply to the Eye of the Bactrian Camel (Camelus bactrianus)

The arterial supply to the eye of the bactrian camel (Camelus bactrianus) was studied by gross dissection. The supply came from the external ophthalmic, external ethmoidal and malar and maxillary tubercular arteries, ophthalmic rete mirabile, and the rostral epidural rete mirabile. The external ophthalmic artery gave rise to branches to supply the dorsal oblique muscle, lacrimal gland, superior and inferior eyelids, and the lateral angle of the eye, and to take part in the formation of the rostral epidural rete and the ophthalmic rete mirabile. The external ethmoidal artery detached off some branches to supply the ventral and medial dorsal rectus oblique muscles, the conjunctiva of the superior eyelid and the fat body of the orbit. The branches of the malar artery supplied the inferior, superior and third eyelids, ventral oblique muscle, and the medial angle of the eye. The ophthalmic rete mirabile gave off many branches to supply the rectus muscles of the eye, dorsal oblique and retractor oculi muscles, levator muscle of the superior eyelid, and the choroid.     

The arterial supply of the eye of the yak (Bos Grunniens)

The heads and necks of 10 yaks were dissected to study the arterial supply to the eye of the yak in the Qinghai-Tibetan Plateau. The supply came from the internal ophthalmic, external eight ophthalmic, superficial temporal and malar arteries. The internal ophthalmic was one of sources of the posterior long ciliary artery. The external ophthalmic artery gave rise to branches to supply the dorsal oblique muscle and otherwise, and to take part in the formation of the ophthalmic rete mirabile. The ophthalmic rete mirabile gave off many branches to supply the rectus muscles of the eye and otherwise. The malar artery was one of the branches derived from the infraorbital artery, and its branches supplied the inferior, superior and third eyelids and otherwise. The superficial temporal artery detached off some branches to supply the lateral angle of the eye and otherwise, and anastomosed with the lacrimal artery of the ophthalmic rete mirabile.     

Tissue distribution of dexamethasone in canine ocular compartments following topical application of dexamethasone-21-isonicotinate and oxytetracycline HCl

Objective  To study the dexamethasone (DXM) concentration at different time points in various compartments of the canine eye following topical application of DXM-21-isonicotinate and oxytetracycline hydrochloride
Animals studied  Thirty dogs to be euthanized for reasons not related to this study were selected and their ocular health status evaluated. Selected animals were treated with DXM-oxytetracycline ointment and euthanized after 6, 11 or 16 h.
Procedure  The concentration of DXM was determined in the following compartments of the eye: third eyelid, cornea, aqueous humor, iris, lens, vitreous body and choroid/retina. The DXM concentration in the eye was measured by radioimmunoassay. The applied amount of DXM was 0.04 mg in 0.2 mL ointment. Dogs were treated once with Corti Biciron^® eye ointment (DXM-21-isonicotinate and oxytetracycline hydrochloride, S & K Pharma, Perl, Germany) and were euthanized 6, 11 and 16 h after treatment.
Results  At 6 h following topical application the mean DXM concentration was highest in the anterior structures of the eye (third eyelid: 18 ng/g, cornea: 36 ng/g). The concentration in the posterior structures was below detection level. A decreased DXM concentration in the anterior structures was measured 11 and 16 h after treatment.
Conclusion  It could be demonstrated that therapeutically relevant concentrations of DXM after a single topical administration are only achieved in anterior structures of the eye. A dosing interval of 6–11 h is recommended to achieve therapeutic drug concentration in those structures. The posterior structures of the eye are not reached by topical administration.     

Leishmaniasis in Canis familiaris – a Report About Microvascular and Cellular Architecture of the Infected Spleen

Leishmaniases are a globally widespread group of parasitic diseases from the group of anthropozoonoses. They are caused by an intracellular protozoan parasite that causes a wide spectrum of diseases in humans and dogs worldwide. In fact, the dog is considered one of the most important reservoir. The spleen is one of the several haematopoietic and immunocompetent organs involved. As this organ is a blood filter, the authors looked for the expression of this infection over the microvascular environment and modifications of the spleen cell population related to immunological responses to this parasitic condition.
Tools:  Scanning electronic microscopy over intact tissue and corrosion casts, transmission electronic microscopy, histology and immunohistochemistry (MAC 387 and CD3).
Results:  Our results show three important modifications concerning the microvascular architecture of the spleen when compared to the normal pattern. A striking scarcity of the sinusoidal system sheath that surrounds the central arteries of the white pulp, a huge development of pulp venules and veins, differentiation of typical features of high endothelial venular cells.
Remarks:  According to our results it seems that independent of the virulence of the parasite involved and the kind of immunity prevalent in a particular host, the spleen develops blood dynamic conditions that allows a sluggish blood flow so that cells involved in immunological processes can proliferate and differentiate and it also contributes to the trapping of lymphocytes to the area through the differentiation of typical characteristics of HEV endothelial cells.     

Microvasculature of the hamster eye: scanning electron microscopy of vascular corrosion casts

The architecture of the retina, choroid and anterior eye segment was investigated in 12 Syrian hamsters using scanning electron micrographs of methylmethacrylate corrosion casts. The hamster eye receives its primary blood supply from the long posterior ciliary artery, which directly enters the optic nerve head, and divides into three branches: the central retinal artery and medial and lateral long posterior ciliary arteries. In the retina the central retinal artery divides into six radiating branches. Retinal arterioles form a slender and long course to capillaries. Retinal capillaries are extremely thin in diameter and form a sparse capillary network. The choroid is supplied by the long posterior ciliary arteries. Choroidal arterioles exhibit a thick and short course to the choriocapillaris. The choriocapillaris is thick and sinusoid-like, forming a dense network in the choroid. The ciliary body, iris and bulbar conjunctiva are supplied by the anterior ciliary arteries, which are branches of the long posterior ciliary arteries. Capillaries supplying the anterior margin of the ciliary process are large in diameter with an irregular bore, forming a thoroughfare channel draining blood in the ciliary arterioles into the pars plana vessels. Blood from the retina is drained by the central retinal veins. Venules from the anterior eye segment empty into the vortex veins via the pars plana vessels. Venous blood from the choroid is drained only by vortex veins via the choroidal veins. The functional significance of the vascular architecture and species differences are discussed.     

Reconstruction of the lower eyelid by third eyelid lateral advancement and local transposition cutaneous flap after "en bloc" resection of squamous cell carcinoma in 5 cats

OBJECTIVE: To describe a novel technique for blepharoplasty to cover a tissue defect involving >/=50% of the lower eyelid. STUDY DESIGN: Prospective clinical study. ANIMALS: Five cats with lower eyelid squamous cell carcinoma (SCC). METHODS: En bloc resection of SCC by removing >/=50% of the lower lid with either the medial or lateral canthus was performed without other adjunctive treatment for SCC. The lid defect was reconstructed with a transposition skin flap derived from the frontal (medial defect) or temporal (lateral defect) region. The third eyelid was advanced laterally without dissection from its insertion; its outer conjunctival layer was removed, and the skin flap was sutured with single interrupted sutures dorsally over the nictitating membrane, ventrally to the cutaneous edge of the surgical wound and medially or laterally (depending on the canthus removed) to the skin of the remaining lower lid. RESULTS: Satisfactory cosmetic and functional results were achieved and the Schirmer tear tests were normal. In 2 cats, the skin flap needed monthly hair trimming to avoid corneal lesions. CONCLUSIONS: After en bloc resection of SCC involving >/=50% of the lower eyelid, reconstruction can be achieved by relocation of the third eyelid and use of a cutaneous transposition flap sutured to the scarified external surface of the third eyelid. Eyelid apposition and lacrimal function were preserved. CLINICAL RELEVANCE: Blepharoplasty using a cutaneous transposition flap sutured to the scarified surface of a relocated third eyelid should be considered for reconstruction of lower eyelid defects with >/=50% tissue loss of the lid margin.     

Intranictitans tacking for replacement of prolapsed gland of the third eyelid in dogs

Objective  To evaluate a new procedure for fixation of prolapsed nictitans glands to the cartilage of the nictitans that will not interfere with the mobility of the nictitating membrane.
Methods  A prospective clinical trial utilizing a nonabsorbable suture to anchor the prolapsed gland to the cartilage of the third eyelid was undertaken. Fifteen eyes of 10 dogs were included in the study. A 4-0 nylon suture was passed from the anterior surface of the third eyelid through the base of the cartilage to the posterior aspect and then tunneled circumferentially beneath the conjunctiva over and around the prolapsed gland. The suture was then passed through the cartilage again to the anterior face of the third eyelid. The gland was replaced into its normal position as the suture was slowly tightened and then tied on the anterior aspect of the nictitans.
Results  Over a period of several weeks, the glands reduced in size and took on a normal appearance. All glands but one remained in place for the length of follow-up, which ranged from 2 weeks to 33 months.
Conclusions  This procedure results in acceptable cosmetic effects with the return of the gland to its normal position posterior to the nictitating membrane. The advantage of this technique over traditional tacking to the orbital rim is that the third eyelid retains its normal mobility and, thus, its protective functions. The procedure once mastered is very quick and can be performed in less time than many of the traditional replacement techniques.     

Scanning electron microscopy of vascular corrosion casts and histologic examination of pulmonary microvasculature in dogs with dirofilariosis

OBJECTIVE: To characterize structural changes in pulmonary vessels of dogs with dirofilariosis. ANIMALS: 8 dogs with dirofilariosis and 2 unaffected control dogs. PROCEDURE: Pulmonary artery pressure was measured in affected dogs, and dogs then were euthanatized. Scanning electron microscopy was used to examine vascular corrosion casts of pulmonary vasculature. Tissue sections of pulmonary vasculature were evaluated by use of histologic examination. RESULTS: Pulmonary artery pressure was higher in dogs with severely affected pulmonary vessels. In tissue sections, dilatation, as well as lesions in the tunica intima and proliferative lesions resulting in constriction or obstruction, were frequently observed in branches of the pulmonary artery. Numerous dilated bronchial arteries were observed around affected pulmonary arteries. Hyperplastic venous sphincters were observed in small pulmonary veins and venules. In corrosion casts, affected pulmonary lobar arteries had dilatation, pruning, abnormal tapering, constriction, and obstruction. In small arteries and arterioles, surface structures representing aneurisms and edema were seen. Bronchial arteries were well developed and extremely dilated, and they formed numerous anastomoses with pulmonary arteries at all levels, from the pulmonary trunk to peripheral vessels. Capillaries in the lungs were dilated with little structural change. Small pulmonary veins and venules had irregular annular constrictions that were caused by hyperplastic smooth muscle cells of venous sphincters. CONCLUSIONS AND CLINICAL RELEVANCE: Scanning electron microscopy of microvascular casts delineated links between the bronchial and pulmonary circulations in dogs with dirofilariosis. Results of scanning electron microscopy provided a structural explanation for the development of pulmonary circulatory disturbances and pulmonary hypertension in dogs affected by dirofilariosis.     

Collagen fiber arrangement in canine hepatic venules

Cell-maceration/scanning electron microscopy, serial sections and scanning electron microscopy of vascular resin casts were employed to demonstrate the arrangement of collagen fibers in the terminal hepatic venules, involving the central, intercalated and collecting veins in dog liver. In cell-maceration specimens, each collagen fiber was observed to run in various directions, forming a sheath with a compact meshwork of collagen fibers. The collagenous meshwork in the hepatic venules was looser than those of the terminal portal venules and hepatic arterioles. Some collagen fibers formed bundles with an elongated spiral arrangement encircling the wall of the terminal hepatic venules. In resin casts, these venules were observed as a twisted configuration caused by spiral collagen bundles. A helical modification of such connective tissue bundles might provide a mechanically stable vascular structure and permit reversible changes in linear and circumferential vascular dimensions at the terminal tributaries of veins. Round or oval pores with diameters of approximately 9 microns were also observed in the sheath of collagen fibers. These pores, together with the relatively loose collagenous meshwork in the hepatic venules, might play a role in lymphocyte migration from these venules into the surrounding tissue and provide high permeability to the venule walls. No such helical configuration and pores were observed in either the portal venules or the hepatic arterioles.     

Microvascular anatomy of the pig eye: scanning electron microscopy of vascular corrosion casts

The microvasculature of the eye of 10 pigs was investigated using scanning electron micrographs of corrosion casts. The ciliary body, iris and bulbar conjunctiva were supplied by the iridociliary ring artery via the long posterior ciliary artery. Capillaries of the ciliary process were of large diameter (23.2-27.5 microm) with an irregular bore, forming a thoroughfare channel draining blood in the ciliary arterioles into the pars plana venous vessels. Arterioles and venules in the iris exhibited a zigzag or spiral features. The third palpebra was supplied by the anterior ciliary artery. The capillary bed of the third palpebra was dense and was formed by many rows of fine hair-pin loops. Capillaries in the bulbar conjunctiva formed a sparse network disposing approximately parallel to the epithelium and formed a well-developed venous plexus, draining into the vortex veins. Retinal arterioles formed a slender and long course to capillaries. Retinal capillaries were extremely thin (3.0-4.0 microm in diameter). The choroid was supplied by the short posterior ciliary arteries. Choroidal arterioles exhibited a thick and short course to the choriocapillaris. The choriocapillaris was flat and sinusoid-like (8.9-13.9 microm in diameter), forming a dense sheet-like network. Blood from the choroid emptied into the episcleral vein via the vortex vein. Blood from the retina was drained by the posterior ciliary veins. The functional significance of this vascular architecture was discussed.     

The vascularization of the epididymis of the boar with special reference to perfusion fixation

Vasculature of the epididymis was investigated by means of corrosion casts. In the boar, epididymal arteries form a complex network around their stem vessel, the testicular artery. Proper perfusion fixation or complete casting therefore require direct injection into one of these branches. To reach the distal cauda, cannulation of the deferential artery is further needed. Connections between all of these feeding vessels occur at the level of the vascular cone. A prominent anastomosis between an epididymal branch and the testicular artery is regularly observed under the caput epididymis. Epididymal veins drain to a large extent into the pampiniform plexus. Unlike the situation in other species, vascularization of testis and epididymis are closely associated in the boar.     

Microvascular architecture of the near-term uterine caruncles in water buffaloes (Bubalus bubalis)

The present investigation was carried out on five near-term pregnant water buffaloes for studying the microvascular architecture of the uterine caruncles. The vascular casts were obtained by injection of 4:1 mixture of mercox and methylmethacrylate through the branches of the uterine arteries. After complete polymerization of the plastic, corrosion was conducted in 20% potassium hydroxide, then the vessel casts were immersed in distilled water, cut into small pieces, sputter coated with gold, and examined by using a scanning electron microscope. The buffalo uterine caruncle is highly vascularized through two slightly convoluted arteries and a single less tortuous vein. The arteries branch into several stem arteries at the base of the uterine caruncle, which follow nearly straight course in the primary septa towards the fetal side. During the courses of these stem arteries arterioles of variable diameters arise. The arterioles run in the secondary and tertiary septae and at this location arterioles and venules are connected through a voluminous capillary complex. The latter consists of capillaries of greatly variable diameters with vigorous coiling and sinusoidally dilated zones. From the capillary complexes the blood is driven through postcapillary venules back to the tertiary, secondary and primary septa, respectively, and then converge into stem veins which leave the caruncles through the branches of the uterine vein.     

Feline entropion: a case series of 50 affected animals (2003–2008)

Aim  To evaluate the signalment, clinical signs, and etiopathogenesis of entropion in 50 cats.
Methods  Signalment and history of 50 cases of entropion in cats presented to a referral ophthalmology clinic. Animals were examined with direct and indirect ophthalmoscopy and slit-lamp biomicroscopy. Animals were treated surgically with a Hotz-Celsus procedure and results of surgery were evaluated between 4 and 22 weeks.
Results  Sixteen cats were young (mean age 4.1 ± 3.6 years) with pre-existing irritative ocular surface conditions such as conjunctivitis, corneal ulceration or sequestrum. Twenty-six cats were relatively older (mean age 11.3 ± 2.2 years) with involutional entropion with or without enophthalmos, presumed to result from a reduction in orbital tissue. Five cats were Persians with entropion associated with brachycephalic facial anatomy, whereas three were entire young adult male Maine Coones with in-turning associated with excessive facial 'jowl' tissue. Surgical treatment was curative in the majority of cases after one surgery although an increased amount of eyelid tissue was required to be removed for correction compared with similar surgery in the dog.
Discussion  This study has shown that entropion in cats may be caused in young animals as a result of continued blepharospasm related to irritative causes such as conjunctivitis or corneal ulceration or in older animals with lid laxity or globe enophthalmos. Lid in-turning was also seen in Persian and Maine Coone breeds.     

Arterial vascularization of the uropygial glands (gl. uropygialis) in the Japanese quail (Coturnix coturnix japonica) and silver polish (Gallus gallus domesticus)

This study focused on the morphological characteristics of the uropygial glands of the Japanese quail and silver polish, particularly the arterial nourishment. With this respect, coloured-latex injected animals were dissected and their glands and related arteries were observed. The gland in the Japanese quail was relatively longer than that in the silver polish. The first caudal segmental arteries in the Japanese quail were specialized as the uropygial gland artery while the fourth caudal segmental ones were continued as the uropygial gland artery in the silver polish. Branches from the second and third caudal segmental arteries and skin also contributed bilaterally to the vascularization of the gland in the Japanese quail. Observing the more complex arterial structure in the Japanese quail suggests more active uropygial gland in this species, when compared with the silver polish.     

Study of the distribution of retinal blood vessels in buffaloes (Bos bubalis)

The distribution of retinal blood vessels in the eye of buffalo was studied macroscopically and microscopically in twenty-two eyes of healthy animals. After macroscopic observation, 12 of 22 eyes were used for histological study. Ten eyes were stained with hematoxylin and eosin and two eyes with PAS stain. The present findings revealed that the eye of the buffalo was characterized by the complex network of retinal blood vessels (holangiotic or euangiotic). The central retinal artery and vein pierced the eye through the optic disc and gave off several branches. There were four pairs of primary vessels that were named dorsal, ventral, nasal and temporal retinal arteries and veins. The veins anastmosed with each other at the optic disc to form a somewhat circle. Three patterns of the distribution of blood vessels were described. The distribution of the arteries and veins was the same.     

Entropion correction by fornix-based suture placement: use of the Quickert-Rathbun technique in ten dogs

The objective of this study was to evaluate fornix-based suture placement as a method for entropion correction in the dog. Lower eyelid entropion with resultant trichiasis was corrected in 10 dogs using fornix-based suture placement similar to that employed in the Quickert-Rathbun technique used in man. A double-ended suture was placed originating at the deepest extent of the fornix and exiting the lid 1-2 mm from the eyelid margin. Degree of correction was assessed visually immediately after surgery and at re-examination with a follow-up period of up to 6 months. Fornix-based suture placement led to immediate eversion of the eyelid in each case and thus amelioration of the trichiasis in all dogs. In two cases eyelid eversion initially appeared over-corrected and in two cases exposure of conjunctival tissue was evident initially at the palpebral margin. In all cases, however, such complications were transient with long-term results giving an acceptable apposition between ocular surface and eyelid margin in all adult dogs. In three juvenile dogs on which the technique was used, further surgical treatment was required as the puppies grew. Fornix-based suture placement is a novel approach to entropion correction in the dog which yields acceptable results in the majority of suitable cases without recourse to incisional surgery.     

Amniotic membrane transplantation for the reconstruction of the ocular surface in three cases

This paper describes the use of amniotic membrane in the reconstructive surgical repair of generalized keratomalacia, ankyloblepharon, and after fibrous histiocytoma removal in two dogs and a cat. Case 1 was an 11-year-old female Yorkshire terrier with severe bullous keratomalacia in the left eye (OS). A frozen canine amniotic membrane graft and a third eyelid flap were applied. At day 80 postoperatively, only a mild scar and corneal vascularization were present. Case 2 was a 4-year-old female Siamese cat with symblepharon of both eyes after rhinotracheitis. Resection of the conjunctiva and frozen canine amniotic membrane transplant were performed. One month later, there was a little corneal scarring and corneal vascularization. Case 3 was a 6-year-old female terrier with a scleral and corneal mass at the 11-12 o'clock position (OS). Resection of the mass and amniotic membrane transplantation were performed. The mass was a fibrous histiocytoma localized to the sclera and cornea. This eye healed with mild conjunctivalization and no pigmentation. Amniotic membrane transplantation can be used as a method of reconstruction of the ocular surface with good repair of the cornea and minimal scarring in small animals.     

Bilateral third eyelid ectopic cilia in an adult horse

A 15‐year‐old Cob mare presented with a 4‐month history of chronic epiphora and intermittent blepharospasm in the right eye. On ophthalmic examination, two translucent aberrant hairs were identified at the third eyelid margin corresponding to an area of corneal fibrosis and neovascularization. Partial excision of the third eyelid was performed, and histopathology confirmed ectopic hair follicles. Two weeks later, clinical signs recurred in the same eye. Examination revealed another pair of aberrant hairs on the bulbar surface of the third eyelid near its leading edge. This portion of the third eyelid was also excised, and histopathology confirmed two additional ectopic hair follicles. Eight months later, the horse developed similar clinical signs in the left eye. Ophthalmic examination showed a single aberrant translucent hair at the third eyelid margin associated with focal fibrosis and neovascularization of the ventromedial cornea. Partial excision of the third eyelid was performed, and histopathology confirmed an ectopic hair follicle within the third eyelid conjunctiva. Excision was curative at 4 years postoperatively with no further recurrence in either eye.     

Surgical management and outcome of lower eyelid entropion in 124 cats

Objectives To evaluate the success rate of various surgical techniques for the management of lower eyelid entropion in cats. Design Retrospective study. Animals studied One hundred and twenty‐four cats with surgical correction of lower eyelid entropion of 200 eyes over a 13 year period. Methods Records of 124 cats were reviewed for signalment, type of entropion, surgical procedure performed and post‐operative result. Results Combinations of the Hotz‐Celsus (HC), lateral canthal closure and full thickness wedge resection techniques were used to treat 64 bilateral and 60 unilateral cases of lower lid entropion. Twenty‐three cats were under a year of age, 52 cats were aged between 2 and 8 years and 49 were over 8 years old. The overall success rate for a single surgical procedure (which may consist of multiple techniques) to correct lower eyelid entropion was 96.0% per eye. The remaining 4.0% had the entropion resolved with a second surgery. A combined HC and lateral canthal closure had a 99.21% success rate of resolving lower lid entropion. Geriatric cats were the most likely age group to develop corneal sequestra; 37% of cats in this group presented with entropion and corneal sequestra concurrently. Seventeen percent of cats that presented with unilateral entropion and did not have prophylactic surgery on the fellow eye went on to develop entropion in the fellow eye. Conclusions A combined HC and lateral canthal closure was the most effective surgical technique in managing lower eyelid entropion of cats in our study. Prophylactic lateral canthal closure in the unaffected eye is recommended.