1887

The lacrimal system

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Abstract

The lacrimal system has two components: the secretory and excretory systems. This chapter looks at canine and feline conditions.

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Figures

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10.1 Lacrimal secretory and excretory systems. (Illustration by Roser Tetas Pont)
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10.2 Normal tear film. The corneal epithelial cells have microplicae and microvilli, which increase the surface area for tear binding. Glycocalyx expressed by the epithelial cells interacts with tear film mucins and promotes retention of tears on the cornea (‘wettability’). Secretory mucins are dispersed in the tear film and soluble antimicrobial proteins are also suspended in the aqueous portion of the tear film. A thin lipid layer over the surface of the tear film reduces evaporation. (Illustration by Roser Tetas Pont) Normal tear film of an adult Staffordshire Bull Terrier. Note the tear meniscus and crisp corneal reflections (Purkinje image).
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10.3 Schirmer tear testing (22 mm wetting) in an adult Boxer.
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10.5 West Highland White Terrier with severe KCS (STT = 0 mm/minute). Note the classic appearance of a tacky mucopurulent discharge adherent to the corneal surface and corneal neovascularization. Appearance of the eye 4 weeks after the initiation of topical ciclosporin therapy (STT = 18 mm/minute). Note that a single branching superficial corneal blood vessel remains.
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10.6 Normal right eye of a dog with unilateral KCS. Neurogenic KCS secondary to otitis media in the left eye. Note the disrupted corneal reflex, conjunctival swelling and third eyelid protrusion.
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10.7 Dry nares associated with lack of lateral nasal gland function (also under parasympathetic control via the facial nerve) in a Toy Poodle with neurogenic KCS. These cases often present with unilateral dried mucoid material completely occluding the ipsilateral nares.
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10.8 Terrier crossbred dog under general anaesthesia. All animals should have their eyes lubricated when under general anaesthesia and during the recovery period.
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10.9 Severe corneal pigmentation, keratinization and fibrosis in a Cavalier King Charles Spaniel with bilateral KCS that was inadequately treated. The eye was blind.
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10.10 Descemetocele with mucopurulent adherent discharge in a dog with acute onset KCS.
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10.11 KCS in an adult Persian can with feline herpesvirus-1. Note the tacky adherent mucoid discharge. The pupil has been dilated for fundus examination.
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10.12 Lipogranulomatous conjunctivitis in an elderly white Domestic Shorthaired cat. The cat has been treated for pinnal and nasal planum squamous cell carcinoma. It was postulated that actinic damage had occluded the meibomian gland openings, resulting in the condition (which was present bilaterally). The TFBUT was <2 seconds in both eyes.
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10.13 Canine nasolacrimal duct relative to the bones of the skull. (Illustration by Roser Tetas Pont)
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10.14 Normal passage of fluorescein, which appeared at the ipsilateral nostril within 30 seconds of application to the conjunctival sac.
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10.15 Lacrimal probes placed in the upper and lower lacrimal puncta to demonstrate their location. Upper lacrimal punctum cannulated with a 22 gauge cannula attached to a 10 ml syringe filled with sterile saline in a 3-year-old Labrador Retriever. Initially, the lower punctum should be observed for the exit of saline and then occluded by digital pressure and the nostril observed for the flow of saline from the nasal punctum.
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10.16 Chronic dacryocystitis associated with disintegration of a foreign body in a Labrador Retriever. The foreign body was inadvertently flushed down the nasolacrimal duct. Repeated irrigation failed to restore patency of the duct and the dog was referred to a specialist. Dacryocystorhinography demonstrated the abnormal region in the narrowest part of the intraosseous portion of the nasolacrimal duct (arrowed). Patency was restored and maintained by cannulating the entire nasolacrimal system using a feline urinary catheter; the restriction in the nasolacrimal duct was appreciable as the catheter was passed. The catheter (6 gauge) was sutured in place to maintain patency. The condition resolved completely within 2 weeks and the catheter was removed.
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10.17 Dacryocystitis in a young Golden Retriever secondary to a foreign body in the lacrimal sac (subsequently removed surgically). Mucopurulent discharge emanating from the lower lacrimal punctum (arrowed).
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10.18 A 9-month-old Labrador Retriever with bilateral lower lacrimal punctal atresia. The upper punctum has been cannulated and flushed with saline. Patency was re-established using a snip technique to open the conjunctiva overlying the lower canaliculus. A snip of conjunctival tissue overlying the punctum was excised. Following snipping the conjunctiva, the lower canaliculus is exposed. A small amount of haemorrhage is present.
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10.19 A 2-year-old Labrador Retriever bitch with chronic epiphora due to a nasolacrimal cyst. Sagittal T2-weighted MR image showing a hyperintense signal from the fluid-filled cyst. Transverse T2-weighted MR image. The cyst is lying within the maxillary bone at the level of the upper right fourth premolar, immediately rostral to the maxillary recess and lateral to the nasal turbinates. The nasolacrimal duct is visible proximal and distal to the cyst. Rhinoscopy was performed but the cyst was not identified. A maxillary bone flap was created to expose the nasolacrimal duct cyst and the medial and rostral walls were resected. The nasolacrimal duct was then cannulated and flushed directly into the nasal cavity. Cannulation with nylon suture material resulted in the suture material entering the nasal cavity.
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10.20 A young Tibetan Terrier with a grass seed awn lodged in the upper lacrimal punctum. The foreign body was removed under topical anaesthesia and the superficial corneal ulcer (located at approximately 11 o’clock in the superionasal cornea) healed uneventfully with the application of a topical antibiotic solution for 1 week.
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10.21 Lower canaliculus repair. The upper punctum is cannulated and viscoelastic containing air bubbles is injected to facilitate identification of the incised canaliculus margin. The lower punctum is then cannulated with silastic tubing. The silastic tubing is advanced into the lacerated canaliculus. The canaliculus is meticulously aligned and figure-of-eight sutures placed in the eyelid margin. The subconjunctival tissues are closed. The skin laceration is closed routinely and the end of the silastic tubing is sutured to the lower eyelid skin to improve retention. (Illustration by Roser Tetas Pont)
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10.22 British Shorthaired cat with tight medial canthal ligaments, medial entropion and epiphora.
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10.23 Domestic Shorthaired cat with an acquired blockage of the upper and lower puncta as a result of extensive symblepharon formation (due to FHV-1 infection). The ventral fornix has been obliterated by the extensive adhesions and the dorsal fornix was also compromised.

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