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Diseases

Ophthalmologic Diseases

Developmental Diseases

Eyelid Agenesis: absence of palpebral margin, lateral canthus and upper eyelid

Persistant Pupillary Membranes: remnants of iris tissue (iris to iris, iris to cornea or iris to lens)

Congenital or Primary Glaucoma: failure to form iridocorneal angle

Nuclear Cataract

Retinal Detachment

Optic Nerve Coloboma: hold in optic nerve head (primary lesion in Collie Eye Anomaly)

Orbital Diseases

Congenital:

Microphthalmia: small ocular globe + intraocular anomalies, blindness if severe

Tx: enucleation if severe

Strabismus: bilateral divergence of ocular globe due to abnormal extraocular muscles or innervation to those muscles, blindness if severe

Tx: challenging, referral

Physiological exophthalmos: shallow orbit in brachycephalic breeds causing inadequate blink, predisposed to proptosis

Tx: canthoplasty to shorten palpebral fissure

Exophthalmia:

Proptosis and orbital abscess/cellulitis

Eosinophilic myositis and extraocular myositis:

C/S: bilateral exophthalmos in large breed dogs, painful mastication/opening mouth (if acute) or muscle atrophy (if chronic), variable 3rd eyelid prolapse

Dx: muscle biopsy

Tx: prednisone 1-2mg/kg BID, weaning dose

Px: guarded, relapse frequent

Orbital neoplasia:

C/S: progressive exophthalmos, non-painful opening mouth

Px: guarded to poor, mostly malignant

Dx: imaging (orbital u/s, CT, MRI)

Tx: exenteration, orbitotomy, orbitectomy or radiation if non-surgical

Enophthalmia:

Loss of orbital tissue mass:

Causes: dehydration/general malaise, age related muscle tone loss, cachexia/weight loss, chronic myositis, facial fractures

Horner’s syndrome:

Sympathetic denervation from central, pre-ganglionic, post-ganglionic lesion

C/S: ptosis, protrusion of nictitans membrane, miosis

Dx:

Ocular pain:

Causes: corneal ulcers, uveitis, glaucoma

Eyelid and Lacrimal Diseases

Upper and Lower Eyelid Diseases:

Tight medial canthal syndrome: tight eyelids leaving no room for lacrimal lake (Bracycephalic breeds, poodles)

Tx: sx difficult, better to leave alone; facial staining can be decreased with oral tetracycline or metronidazole

Medial trichiasis: hairs from caruncle on cornea in medial canthus wicking tears on to face

Tx: surgery (referral)

Trichiasis: correctly placed hairs touching cornea, associated with entropion

Distichiasis: cilia originating from meibomian gland, problematic in dogs with coarse hair

Tx: removal of cilia, risk of regrowth and eyelid margin scarring

Ectopic cilia: cilia originating from palpebral conjunctiva, usually at 12 o’clock position

Tx: removal of cilia en-bloc using chalazion clamp

Entropion: inward rolling of eyelid with secondary trichiasis

Tx: temporary tacking sutures (growing puppy), modified or standard Hotz-Celsus

Ectropion: outward rolling of eyelid

Tx: wedge resection

Blepharitis: inflammation of upper/lower eyelids, younger dogs more predisposed

Causes:

Chalazion: impaction of meibomian gland (sty), yellow nodule at eyelid margin

Tx: curettage if warm compress ineffective

Hordoleum: infection of glands of Zeis or Moll, abscess at eyelid margin

Tx: drainage, warm compress and systemic abx

Juvenile cellulitis: multiple nodules/abscesses at eyelid margin

Tx: prednisone 0.5mg/kg and cephalexin for minimum 3 weeks

Allergic

Parasitic: scabies, demodex (Dx: skin scraping)

Immune-mediated: pemphigus, lupus (Dx: skin biopsy)

Neoplasia:

Meibomian gland adenoma

Tx: wedge resection (if <1/3) or blepharoplasty (if >1/3)

Third Eyelid Diseases:

Prolapsed gland of the third eyelid

Tx: anchoring or Morgan pocket technique

Everted or scrolled cartilage

Tx: surgery or thermal cauterization

Follicular conjunctivitis: hyperemia and hypertrophy of follicles on bulbar conjunctiva due to chronic antigenic stimulation (smoke, dust, etc) or hyperimmune system in young dogs

Tx: debride follicles with cotton-tip applicator and topical abx-steroid TID for 2 weeks (wean down)

Neoplasia:

Gland of third eyelid: adenocarcinoma

Conjunctiva: melanoma, hemangioma/hemangiosarcoma

Lymphoid follicles: lymphoma

Lacrimal Diseases:

Keratoconjunctivitis sicca (KCS)

Causes: immune-mediated (most common), neurogenic (parasympathetic innervation to gland via CN VII and corneal sensory innervation via CN V), infectious (FVH, CDV), drug-induced (atropine, sulphonamide, opioid), endocrinopathy (DM, Cushing’s, Hypothyroid), general anesthesia, stress, dehydration, cachexia

Dx: STT (suspicious 10-15mm/min, very suspicious <5mm/min)

Tx:

Tear stimulant: cyclosporine (first line), tacrolimus, pilocarpine (neurogenic) PO 1 drop per 5kg BID on food (start low and work up q2 weeks)

Tear supplement: eye gel > lube, topical abx (BNP or tobramycin if ulcer, fusidic acid if no ulcer), topical steroid or NSAID with caution

Parotid gland transposition

Epiphora

Causes:

Imperforated puncta: congenital (Cocker Spaniels)

Tx: incision of membrane overlying puncta

Obstruction of nasolacrimal system: infection, foreign body or neoplasia

Dx: CT (or skull radiographs) with contrast

Tx: flush duct with heavy sedation, referral sx to create new duct

Conjunctival and Scleral Diseases

Conjunctivitis

C/S: branching of BVs (conjunctival hyperemia), chemosis, ocular discharge

Causes: KCS, ulcer, intraocular disease, infectious

Bacterial: BNP, fusidic acid, bactericidal abx if severe/immunocompromised (cytology or culture if no improvement)

Viral (CDV, adenovirus): topical abx for secondary bacterial infection

Allergic: eosinophils on cytology, topical steroid-abx +/- atopy treatment

Follicular conjunctivitis

C/S: lymphoid hyperplasia, conjunctival hyperemia, discharge

Causes: young dogs, chronic antigenic stimulation (irritation or environmental)

Tx: topical steroid-abx TID, wean until resolution (may take weeks-months) +/- debride

Conjunctival hemorrhage: blood trapped between conjunctiva and sclera

Causes: trauma, coagulopathy, systemic hypertension

Tx: treat underlying problem

Conjunctival masses:

Dermoid (congenital): mass of pigmented tissue with hair (Dachshunds, Dalmatian, Dobes)

Tx: surgical removal (referral)

Neoplasia:

Benign: papilloma, hemangioma, MCT

Malignant (primary or metastatic): hemangiosarcoma, melanoma, lymphosarcoma

Tx: sx with adjunct therapy (radiation, laser, cryotherapy)

Ddx: conjunctival blister/hemorrhage if clear borders

Scleritis: immune-mediated (Cocker spaniels, Golden retrievers) +/- uveitis

Tx: steroid (topical + systemic) or cyclosporine (topical + systemic)

Px: goal is control not cure

Scleral masses:

Nodular granulomatous episcleritis (NGE): raised mass +/- cornea, limbus, conjunctiva

Dx: biopsy (fibrocytes, histiocytes, plasma cells, lymphocytes)

Tx: oral steroids (Tetracycline 500mg and Niacinamide 500mg PO TID for >1 month, if improved BID until 2 weeks beyond clinical resolution), referral sx if no improvement

Corneal Diseases

Ulcerative keratitis:

Corneal ulcers:

Causes: trauma (foreign body, eyelash, eyelid, lagophthalmos (incomplete blink), buphthalmia (enlargement of eyeball), KCS, infectious

1) Simple: acute, superficial, miotic pupil (NO infiltrate, vascularization or pigmentation)

Tx: bactericidal abx QID +/- atropine BID up to 3 days (verify STT), recheck in 3-5d

2) Complex: acute/chronic, variable depth (YES infiltrate, edema, vascularization +/- melting)

Tx: debride, flush, bactericidal abx q2-4h, serum q1-2h, atropine BID up to 3 days, systemic abx, recheck in 24h (referral for keratectomy, conjunctival graft)

3) Recurrent: chronic, superficial, loose epithelial edge (halo at ulcer border), NO infection

Tx: debride, grid keratotomy, bactericidal abx QID, atropine BID up to 3 days, contact lens for 3 days, recheck in 7 days (50% improvement) + 2 weeks (85% improvement)

Non-ulcerative keratitis:

Pigmentary keratitis: pigmentation from melanocytes in corneal epithelium

Causes: chronic irritation, KCS, pugs

Tx: medial canthoplasty in pugs, lifelong lubrication, topical steroid, topical cyclosporine 0.2%

Chronic superficial keratitis (Pannus): neovascularization with plasma cell infiltrate and pigmentation, typically at lateral limbus

Causes: immune-mediated, aggravated by UV, German Shepherds + Greyhounds (2-5y)

Dx: corneal cytology (single plasma cell = diagnosis)

Tx (control not cure): steroid, cyclosporine 0.2% BID lifelong, goggles if tolerates

Corneal dystrophy vs degeneration: hyper-reflective crystalline infiltrate (cholesterol, lipid, calcium)

Corneal dystrophy:

Inherited (Shelties), bilateral/symmetrical/central cornea, primary, NO vascularization

Tx: not necessary

Corneal degeneration:

Acquired (spontaneous), unilateral/asymmetrical/anywhere on cornea, secondary (endocrinopathy, hypercalcemia, hyperlipidemia), YES vascularization +/- ulcer

Tx: may require keratectomy

Endothelial dystrophy: abnormal endothelial cells leading to corneal edema, epithelial bullae resulting in corneal ulcers (Boston Terrier, Chihuahua, Dachshund, 7-9y)

Tx: topical hypertonic saline 5% QID lifelong, thermokeratoplasty/conjunctival graft/transplant (referral)

Corneal masses:

Dermoid (congenital): pigmented tissue with hair follicles

Tx: keratectomy to create ulcer to heal by second intention

Neoplasia: hemangioma/hemangiosarcoma, limbal melanocytoma

Tx: surgery + adjunct therapy (cryotherapy, radiation)

Glaucoma

Pathophysiology

Impaired drainage of aqueous humour at iridocorneal angle or pupillary block → increased pressure in anterior chamber → compression leads to ischemia + hypoxia → cell death of retinal ganglion cells + optic nerve → blindness

Types:

Congenital: <6 mo, unilateral, rapid buphthalmia (sclera still growing + elastic)

Px: grave, often req enucleation

Primary: bilateral, asynchronous, hot breeds (Cocker, Boston, Basset, Poodle, Sharpei, Husky, Samoyed), iridocorneal angle closed/narrow/open or abnormal (goniodysgenesis)

Elevated IOP for 24-72h can lead to permanent blindness

Secondary:

1) Anterior lens luxation (Terriers)

2) Severe uveitis (iris bombe) - inflammation causes iris to bulge forward, stick to anterior lens capsule causing pupillary block

3) Membrane overlaying iridocorneal angle

Pre-iridofibrovascular membrane (PIFM) or corneal endothelial overgrowth

4) Intraocular neoplasia

C/S:

Acute (hours-day)

Red eye (conjunctivitis, episcleritis), diffuse corneal edema, dilated fixed pupil, pain

Chronic (weeks-months)

Buphthalmia, keratitis, corneal striae (breaks in Descemet’s membrane), diffuse corneal edema, fixed dilated pupil, +/- lens luxation, retinal atrophy, vision loss (black rim around optic nerve)

Dx: IOP (TonoVet mean reading 10-25mmHg)

Medications:

Osmotic Diuretics

10 minute onset, 1-5 hour DOA (peak 1 hour)

20% Mannitol 1-2mg/kg IV over 20-30 mins and withhold water for 2-3 hours

Glycerin 1-2g/kg PO (frequently causes vomiting)

Contraindications: DM, renal failure, cardiomyopathy, dehydration, uveitis

Carbonic Anhydrase Inhibitors (CAI)

2 hour onset, 6-8 hour DOA

Topical Brinzolamide 1% TID, Dorzolamide 2% TID (AE rare)

Methazolamide 2.5-5mg/kg PO BID (AE: metabolic acidosis, hyperK)

Contraindications: renal failure, cardiomyopathy, dehydration

Beta Blockers (BB)

2 hour onset, 10-12 hour DOA

Topical Timolol or Betaxolol 0.5% BID (can combine with CAI eg. Cosopt BID to TID)

Contraindications: cardiomyopathy, asthma (especially cats)

Prostaglandin Analogues (PA)

30-45 minute onset, 20 hour DOA (peak 1-1.5h)

Topical Latanoprost 0.005% or Travaprost 0.004% SID to BID (AE: intense miosis)

Contraindications: uveitis, (anterior) lens luxation

Parasympathomimetics

Sympathomimetics

Initial Tx:

Primary glaucoma - 1 drop of each CAI, BB, PA

Reduces IOP within 30-45 minutes, if no response consider mannitol

Secondary glaucoma

Lens - Mannitol 1g/kg IV over 20-30 min + withhold water for 2-3h + start CAI

Repeat if no change (>30mmHg 1 hour post injection)

Anterior lens luxation - extraction (visual) or enucleation/evisceration (blind)

Posterior lens luxation - PA + topical corticosteroid

Uveitis - CAI, BB + corticosteroid (topical or systemic), NOT topical NSAID

Intraocular neoplasia - enucleation, mets work up

Aqueocentesis (salvage procedure, controversial) - 30 gauge 1/2 inch needle at lateral limbus letting 1-3 drops of aqueous drip out of hub, avoiding iris and lens

Reperfusion injury = consequence of therapy

Anectodal use of systemic Ca channel blockers (Amlodipine PO for 1 week) or corticosteroids (Dexamethasone 0.1mg/kg IV to reduce oxidative stress

Maintenance Tx (Primary Glaucoma):

Affected Eye: topical CAI TID +/- BB +/- PA

“Good” Eye: topical CAI + steroid to delay onset of glaucoma

Acute attack: measure IOP q1h until <25mmHg then q4-6h for 24h then weekly then monthly

Surgical Tx:

Blind: enucleation vs evisceration vs chemical ablation (gentamicin + dexamethasone)

Visual: laser photocoagulation of ciliary bodies, anterior chamber shunt (referral)

Uveal Diseases

Conjunctivitis

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