Opthamology Flashcards
What is entropion? What breeds is it common in?
Common in young dogs, retrievers, pointers, setters and larger breeds. Lid margins roll inwards causing hairs or lashes to irritate and potentially abrade the cornea. The pathophysiology is complex and involves the relationship between the eyelid and the counterpressure from the globe, tone of the orbicularis muscle and size of the palpebral fissure. The most common site is the lateral lower lid. Pain with lacrimation and blepharospasm are always present.
Describe the anatomy of the canine eyelids?
3 layers - outer layer of normal skin, middle layer of muscle, fibrous connective tissue and glands, inner layer of palpebral conjunctiva. The orbicularis oculi muscle encircles the lid margin and closes the eye. The tarsal (meibomian) glands run at right angles to the lid margin. Dog only has lashes on the upper lid, close to lid margin.
What is the treatment of entropion?
Surgery. Excisional correction not always required in younger patients where there is still considerable anticipated growth. Vertical mattress sutures or vertically oriented surgical staples left in place for a few weeks may be all that is required in the younger patient. For simple anatomical entropion the hots celsus technique is straightforward and effective.
What is atonic entropion/trichiasis?
Loss of tone in the skin of the upper eyelid, combined with an excessive amount of head skin, can result in the lateral upper lid drooping to the extent that hairs and cilia impinge on the cornea, causing discomfort and corneal damage. It is best treated with a stades procedure.
What occurs in a stades procedure?
The skin adjacent to the lid margin is excised and the area left to granulate. Owners should be warned that the post operative appearance is unsightly for a couple of weeks but the final cosmetic result is good.
What are breed related medial canthal abnormalities?
Entropion of the medial lower lid may compress the lower punctum and caniliculis. Caruncular trichiasis and deep medial canthal grooves caused by tight medial canthal ligaments exacerbate the effects of entropion. Common in brachycephalics and toy breeds such as min and toy poodle. The cornea is unaffected and the problem is usually cosmetic rather than painful.
What is ectropion?
The lower lid turns outward, creating a gap between lid and cornea and exposing the conjunctiva. Usually requires no attention. With conjunctivitis or keratitis from chronic exposure, the problem is dealt with by wedge excision bordering the lateral canthus.
What is Diamond eye?
the lids take a diamond shape with a lateral upper lid entropion and mid lover lid ectropion. Diamond eye is the result of a combination of inadequate support from lateral canthal ligament, excessive skin and a large palpebral fissure.
How can excess facial skin be a problem for eyelids?
Cocker spaniel, clumber spaniel etc have excess facial skin that droops downwards causing upper lid entropion or extreme ptosis and lower lid ectropion. In the chow chow and sharpei entropion may be associated with the deposition of subcutaneous fat in the skin folds in the middle age. A face lift procedure or a modified stades procedure may be required. Referral is highly recommended.
What is lagopthalmos?
Macropalpebral fissure with lagopthalmos occurs in brachycephalic breeds, predisposing affected animals to chronic keratitis and progressive pigmentary infiltration. Conformational lagopthalmost may be complicated by low tear production, medial canthal entropion or irritation from lacrimal caruncle or nasal fold hairs.
What is Distichiasis?
A common condition where abnormally positioned cilia emerge from the lid margin usually at or close to the tarsal gland openings. Most dogs show no clinical signs. Dogs with evidence of discomfort (lacrimation, increased blink rate) should be referred for treatment.
What is conjunctival cilia?
A single hair emerging though the palpebral conjunctival a few millimetres from the lid margin at right angles to the cornea. This is a painful condition. There is often a shallow vertically oriented ulcer opposite the emerging cilia. Treatment is by excision of a wedge of tissue containing the cilium.
What is trichiasis?
Perioocular hairs growing in a normal location may be directed abnormally towards the ocular surface, which may cause conjunctivitis and keratitis. Trichiasis results from entropion and can be associated with nasal folds, medial canthus and caruncle.
What is blepharitis?
Inflammation of the eyelids.
What is meiobomianitis ?
Infection of the meiobomian (tarsal glands). unilateral or bilateral thickening/hyperaemia of the lid margins with swolen and inflamed tarsal glands visible when everting the lid. Treat with hot compress, topical & systemic antibiotics
What are external hordeolum?
Single or multiple abscesses caused by suppurative infection of glands of Zeiss or Moll. Focal abscesses may be opened by scalpel incision.
What is a Chalazion?
Obstruction of tarsal gland secretions by a blocked duct can cause the gland to rupture, liberating its content within the eyelid substance, visible through the palpebral conjunctiva as a firm spherical yellow lipgranuloma. If occular surface irritation is present then treat by incising into the lesion with a blade, under general anaesthesia and curretting out the contents, followed by topical antibiotics for 7-10days.
Describe Eyelid Neoplasia In the dog?
Most lid tumours occur in old dogs and are benign in behaviour. Tarsal gland adenomas are most common, followed by melanomas. May abrade the cornea or bleed and should be removed if causing problems.
What is the third eyelid?
A large fold of conjunctiva supported internally by a T shaped cartilage. The base of the cartilage is surrounded by the nictitans gland, which produces about 30-40% of the aqueous component of the PTF. It is important in the distribution of the tear film. Movement of the TEL of the cat can be both active and passive.
What is a prolapse of the nictitans gland?
Dorsal prolapse of the nictitans gland appears acutely as a smooth pink swelling at the medial canthus (cherry eye). Thought to result from a weakness in the connective tissue attachment between the gland and the periorbital tissue. Although the gland may be excised there is an unacceptably high post operative risk of dry eye. Surgical replacement should therefore be attempted.
What is scrolling of the third eyelid?
Also known as eversion or kinking of the cartilage. Usually giant breeds. The straight stem of the cartilage kinks forcing the membrane to fold outwards so that the leading edge no longer contacts the cornea. Treatment is by excising the kinked portion of the cartilage from the deep surface of the membrane.
What is plasma cell infiltration of the third eyelid?
A condition affecting the GSD and collie types, with bilateral depigmentation of the membrane, a pink/red fleshy infiltrate and a rough irregular surface. The infiltrate consists of plasma cells and lymphocytes and is often concurrent with chronic superficial keratitis. Treatment is with Topical corticosteroids. Topical cyclosporine may also be used.
What may cause third eyelid protrusion?
Retrobulbar space occupying lesions with exopthalmost e.g extraconal abscess or tumour. Retraction of the globe - active or passive with enopthalmos, reduction in globe size, reduction in orbital contents e.g dehydration, cachexia, masticatory muscle atrophy, alteration to nervous control e.g horners syndrome, tetanus.
What is the conjunctiva?
A thin mucous membrane which extends from the lid margins where it is continuous with the epidermis to the limbus where it meets the corneal epithelium. It lines the inner surface of the upper and lower lids, reflected forwards at the fornixes as the bulbar conjunctiva over the globe.
What is conjunctivitis?
The whole conjunctiva becomes diffusely reddened with a variable amount of discharge. In significant bacterial infections the discharge has a typically purulent yellow green appearance. The majority of bacterial conjunctivitis in the dog are secondary to causes such as an eyelid mass, eyelid irregularity or foreign body. Infection most commonly with staphylococcus. Fusidic acid has good activity against G+ve bacteria and need only be applied once or twice daily.
What is opthalmia neonatorum?
Infection within the conjunctival sac before the eyelids are opened (usually at 10-14 days) will cause swelling of the eyelids, sometimes with a small amount of pus escaping at the medial canthus. This must be treated promptly to avoid corneal ulceration and penetration. The lids should be opened along their line of fusion digitally or with blunt ended scissors. The surface should be irrigated with sterile saline and the infection treated with broad spec topical antibiotic ointment.
how does distemper affect the eyes?
A purulent occular discharge may accompany the other signs of the disease. Treatment is symptomatic, check tear production as the virus attacks the lacrimal gland, possibly leading to corneal damage. A chorioretinitis may also be present.
What is follicular conjunctivitis?
Hypertrophy of the lymphoid follicles scattered on the bulbar suface of the nictitans and the conjunctival fonixes occurs with chronic antigenic stimulation. Most cases respond to treatment with saline irrigation and symptomatic use of topical steroids.
How can allergy affect the eyes?
Conjunctiva and lids may be involved in local allergic reactions or generalised atopy. The finding of a single eosinophil on cytology is Diagnostic of allergic process.Immediate hypersensitivity reactions are occasionally encountered with rapid and dramatic chemosis.
Describe chronic conojunctivitis
A low to medium grade mucupurulent chronic conjunctivitis seen as a generalised problem in association with marginal tear production, seborrhea, pyoderma, otitis externa, ectropion etc. Treatment is symptomatic with a view to contol.
What is keratoconjunctivitis sicca (dry eye)?
A common condition in the dog resulting from a deficiency in the aqueous potion of the tear film produced by the lacrimal and nictitans glands. May be immune mediated, endocrine disease, Drug induced (sulphadiazine), viral adenitis.
How is the schirmer I tear test used to diagnose keratoconjunctivitis sicca?
Schime tear test strips are sterile, individually wrapped filter paper stips. The paper is placed in the conjunctival sac of the lower lid so that the notch is at the liid margin. >15mm is normal. The mean normal STT is around 21mm in the dog. values of 13-15mm should be interpreted on the basis of the occular surface appearance and level of discomfort.
How is dry eye managed with tear stimulation?
Topical 0.2% cyclosporine ointment either alone or in conjunction with tea replacement. Tacrolimus and pimecolimus also used.
What is a fluoescein drainage test?
Fluorescein instilled into both eyes - especially if unilateral problem as normal eye acts as a positive control. External nares observed for the passage of fluorescein. dye usually seen within 4 minutes.
What is nasolacrimal cannulation?
The upper punctum is cannulated with a lacrimal cannula and a syringe containing 5ml of saline attached. Saline should appear at the lower punctum when the upper punctum is flushed or at the nares when the lower punctum is occluded by gentle digital pressure. Do not use force when injecting as this can rupture the caniliculi.
What is dacryocystorhinogaphy ?
0.5-1.0ml positive contrast used to delineate the nasolacrimal system.
What is congenital imperforate puncta?
Produces epiphora in young animals from about 8 weeks of age. The duct system is present but the punctum is occluded by a thin covering of conjunctiva. The diagnosis is made by direct visualisation confirmed by flushing, the saline will form a bleb at the site of occlusion. The covering membrane can simply be surgically excised.
What is dacryocysitis?
Inflamation of the lacrimal sac (usually plus inflammation of the duct and canaliculi.) Most often due to a foreign body such as a grass seed. Flushing the system from the upper punctum may allow foreign body to be gasped at the lower punctum.
Describe the 5 layers of the cornea
Anterior outer epithelium. - non keatinised, stratified squamous epithelium with a rapid turnover of cells. Basement membrane produced by deepest layer of epithelial cells. Connective tissue stroma - composed of collagen lamellae, separated by ground substance and fiboblasts. Descemets membrane - the basement membrane of the underlying endothelium. Endothelium - deepest layer, important forr maintaining corneal dehydration.
What do opacities in the cornea take the form of ?
Oedema Cells - infiltrating the cornea or deposited on the endothelium Blood vessels Pigment Disorganised collagen Lipid
What is corneal dermoid?
A congenital mass of hairy skin on the cornea, usually at the lateral limbus. The hairs on the dermoid can irritate the corneal surface.
What is pigmentary kerratitis?
pigment may be carried in from the limbus along with new blood vessels in response to a variety of chronic corneal insults damaging the Occular surface.
What is chronic superficial kerratoconjunctivitis (pannus)
A chronic superficial vascular keatitis occuring mostly in GSD, geyhound, collie types. A rough fleshy looking infiltrate of inflammatory tissues, pigment and vessels advances across the cornea. The corneal epithelium is intact. Visual loss can occr. Immunosuppression with topical steroids.
Describe Age related corneal endothelial degeneration?
Bilateally but asymmetrical degenerative condition of the corneal endothelium occurring as a senile change in old dogs. The Loss of endothelial cells causes failure of the endothelial pump mechanism resulting in steamy blue appearance of stromal oedema.
What is corneal degeneation?
Occurs when deposition of lipid is seen in association with inflammation and vascularisation. Lipid may be produced in situ or circulating lipid may enter the cornea. Lesions consist of cholesterol, phospholipids, fatty acids and calcium.
What is corneal dystrophy?
Primary, bilateral and inherited disorder characterised by well demarcated central or paracentral white grey crystalline opacites, composed of cholesteol, phospholipids and fatty acids unde mafnigication show a fibreglass like quality.
What is lipid keratopathy?
uuni or bilateral occular manifestation of systemic disease characterised by peripheral or central crystalline opacities and a clear peri limbal zone. Corneal vascularisation may develop with chronicity.
What is corneal arrcus?
Bilateral peripheral lipid deposition which is uncommon, is un variably associated with plasma hyperlipoproteinaemia and the underlying cause should be determined.
What is corneal ulceration?
The Corneal epithelium provides a protective barrier which is resistant to bacterial colonisation and prevents water entering the cornea. Loss of full thickness of the epithelium exposes the underlying stroma. Most often as a result of mechanical trauma. Successful bacterial colonisation may occur and there may be further stromal loss and full thickness corneal perforation.
How does normal healing of corneal ulcers occur?
Healing of epithelial defects is usually rapid achieved by the migration of adjacent basal epithelial cells to cover the defect which then replicate to restore the full epithelial thickness. The stromal defects of deeper ulcers are initially filled by a fibrin clot. Activated keratocytes at the wound edges secrete collagen, aided by invading fibroblasts. This new collagen tends to be disorganised.
What are the clinical signs of corneal ulceration?
Discomfort - usually marked. Lack of pain indicates abnormal corneal sensation, conjunctival hyperaemia, variable amounts of localised corneal oedema and irregularity of the surface contour. Neovascularisation and cellular infiltration of the cornea is common with chronic ulcers.
What are the causes of corneal ulcers?
External trauma, hair/lash trauma, entropion and ectopic cilia, infection, bacterial colonisation secondary to trauma, rarely fungal, tear film abnomalities, exposure keratopathy.
What is exposure keratopathy?
The central corneal damage resulting from inadequate protection of the conea by the eyelids and third eyelid which may be compounded by inadequacy of the pre ocular tear film. Causes are varied and include 1) Prominent globe with poor lid closure - brachycephalics. 2) Facial nerve paralysis - not usually a problem fo breeds that can retract their globes sufficiency to spread the tear film but brachycephalics cannot do this. 3) Trigeminal nerve paralysis - absent corneal sensation results in a severe keratitis affecting the area of the cornea exposed between the lids.
What are superficial under run ulcers (SCCED)
Ulcer healing will be severely compromised if the edges of the epithelium fail to adhere to the underlying stroma. This creates a flap or Underrun edge at the ulcer margin which may be recognisable by pentorch examination
How are mid stromal ulcers managed?
Can be managed medically with broad spectrum topical antibiotics every 2-6 hours such as neomycinbacitracin/polymixin. Treat accompanying reflex uveitis with atropine as needed to dilate the pupil and anti collagenase 3-4 x daily.
How is a deep ulcer managed?
Cytology and culture should be performed. The edge of the ulcer is swabbed then gently scraped using the blunt end of a scalpel blade. Followed by surgery to support the conea. Treat empirically with a topical fluoroquinolone.
