Diseases of the Eye Casey Conway Jeannie Stall , R.V.T. & ??? Credits : Clip Art graphics/Google images

The Eye CDCA has great picture of a cross section.(hint) Most highly developed of all senses Most pets can live quality lives with a vision loss Proper diagnosis, quick treatment – Essential! 3 main categories of eye diseases: Accessory structures The globe The retina and the neural pathways

Anatomy Credits: ukvetsonline Image credit: ukvetsonline.com

Diseases of the Accessory Structures Eyelids, conjunctiva, tear ducts, third eyelid, lacrimal glands Red eyes, blepharospasm (squinting), ocular discharge Common causes: Trauma & infection Conjunctivitis/Epiphora(overflow of tears)/ KCS (Keratoconjunctivitis sicca)/Cherry Eye Keratoconjunctivitis sicca – “Dry Eye “

Conjunctivitis Inflammation of the conjunctiva Rarely a primary dz process Canine: can be non-infectious or infectious Feline : is primarily infectious FHV – seen w/ Upper Resp. Tract symptoms Calicivirus Chlamydia psittaci Mycoplasmas Feline Herpes Virus

Conjunctivitis cont’d Clinical signs Chemosis (swelling) Hyperemia (redness) Ocular discharge +/- signs of URT dz Dx PE (thorough exam of conjunctiva/foreign body) Schirmer Tear Test, conj. scraping (cytology, c & s) Tx: Resolve underlying systemic dz. Topical antibiotic ointments/drops Nonsteroidal oint/drops may be needed Keep eyes clean and clear Prevent eye issues – riding out car window!

Epiphora Overflow of tears Clinical Signs Overproduction (pain or irritation) Faulty drainage: (lacrimal duct blocked by swelling or trauma) Clinical Signs Watering of the eye Wet facial hair Secondary bacterial infection of facial skin Discoloration of the facial hair

Epiphora cont’d……. Dx: Tx: Eye exam Fluorescein dye Dacryocystorhinography ( Radiography of nasolacrimal duct ) Tx: Resolve primary cause of pain & irritation / Flush lacrimal ducts / Surgery / Topical abx/ Trim hairs

Eyelid Diseases At the base of each eyelash is a sebaceous gland Hordeolum: Meibomian gland abscess, usually caused by a staph. infection Chalazion: When inflammation involves meibomian glands & granulation occurs Eyelid neoplasms : Older animals/ most are benign (cat usually malignant), Squamous cell carcinoma most common tumor The eyelid sebaceous gland is also known as : Meibomian or tarsal gland . A “Chalazion “ is a plugged or blocked meibomian gland .

Blepharitis: Swelling of the eyelids Causes: Clinical signs Allergens Nutritional Deficiencies Viral Dermatitis from any cause Clinical signs Generalized swelling of lid Periocular pruritis (itchy eyes) Periocular alopecia ( hairloss) Rubbing of the eyes

Blepharitis Cont. Dx: Tx: warm compresses Eye exam Skin scrape Fungal culture Bacterial cultures Tx: warm compresses Express hordeolum(staph infection) Surg. removal of chalazion (granulation tissue) Topical abx or systemic abx Corticosteroids ( Prednisolone) Antifungals ( Conofite or Tresaderm)

Blepharitis

Entropion Eyelids roll in against the cornea Common in dogs, not in cats 3 main forms: Congenital: breeds have large orbits with deep-set eyes, inadequate lid support, lid droops over the lower orbital rim and inverts – Collies, Great Danes, Irish Setters, Dobes, Goldens, Rotts, Weim (primary lid deformities, poor ocular muscle development) Acquired nonspastic: surgical or traumatic – scarring of the lid with contraction – lid turns inward Acquired spastic – most common in cats – secondary to painful corneal lesions, conj. inflam. or both

Entropion

Entropion Clinical Signs Rolling inward of the lid margin(s) Epiphora (tear overflow) Chemosis ( conjunctiva swelling ) Swelling Conjunctivitis Blepharospasm(eyelid muscle spasm) Pain +/- corneal ulceration Photophobia

Entropion Con’t…… Dx: Tx: Surgical correction Observe lids interaction with globe Eye exam while awake Tx: Surgical correction

Ectropion: Eyelids that roll outward, exposing the cornea Excessive lid droops outward Natural breed characteristic for: Basset hounds, bloodhounds, cocker span, clumber span, Eng. bulldogs, St. Bernards – usually asymptomatic All breeds: Secondary to muscular dz in senile dogs/ Dogs w/ surgical overcorrection of entropion Clinical signs Lid eversion Conjunctivitis Epiphora Keratitis Purulent exudate

Ectropion Cont. Dx: Observe lids Interaction with globe Eye exam while awake Tx: Surgical correction advised if clinical signs present

“Cherry Eye” or Hypertrophy of Nictitans Gland Third eyelid: Protective structure/Spreads pre-corneal tear film Covers eye to protect from injury/ Produces ~50% of lacrimal fluid Prolapse of 3rd eyelid/gland: “passive forward displacement when eye withdrawn into orbit” Hypertrophy of gland ONLY occurs in K9’s Etiology: Unknown cause Breeds: Basset, beagle, Boston, cocker

Cherry Eye Usually seen in young dogs (< 2 yrs. old) -usually neoplasia if seen in old K9’s & cats Medial canthus is filled with red, swollen, third eyelid, resembles a small cherry Clinical signs Reddened enlargement of tissue in the medial canthus of the eye Mild irritation Usually no pain Epiphora ( tears) +/- conj. irritation

Cherry Eye continued….. Dx: Tx: W/O sx., corneal damage can occur & Clinical signs Predisposed breed Rule out tumor (usually older dogs & cats) Tx: Surgical replacement of the gland, Tuck sutured Avoid excision – predisposes to KCS – only excise in cases of neoplasia W/O sx., corneal damage can occur & may affect vision

Cherry Eye

Glaucoma: In healthy eye: Aqueous fluid production =‘s aq. fluid amt. leaving eye, so IOP(intraocular pressure) remains fairly constant More aqueous fluid produced than leaves = glaucoma Normal k9/fel IOP range: 12-22 mm Hg w/ Tono-pen Most K9’s have decreased outflow, not increased prod. Primary – inherited defect (cocker, basset, chow) Secondary –drainage angle obstruction secondary to another dz.– ie: Neoplasia, uveitis, lens luxation, hemorrhage IOP = Intra ocular pressure

Glaucoma cont’d Acute – elevated IOP (> 60 mm Hg ) can produce blindness within hours Clin. signs: Ocular pain, vascular congestion, diffuse corneal edema, dilated pupil, sluggish or unresp to light, +/- blind Chronic – painful, blind eye which is unresponsive to med. therapy. Make pet comfy w/salvage procedures Clin. Signs: Enlarged lobe, corneal striae, optic disk cupping, pain, blindness Dx: IOP > 30 mm Hg,/ clin. signs/ r/o luxated lens Tx: Acute – true emergency – decrease IOP rapidly, sx Chronic – sx – enucleation Bilateral disease – even if one eye is asymptomatic

Corneal Ulcers Ulcerative Keratitis Cornea:Window of the eye- has 4 layers Epithelium Stroma Descemet’s membrane Endothelium Full-thickness loss of corneal epithelium exposing stroma Etiology: Trauma, chemicals, foreign body, prev. dz. ie: KCS/ Herpes in cats, conformation issues, distichiasis (tiny, inwardly –facing meibomian gland hairs) Clinical signs Pain Epiphora Blepharospasm Conjunctival hyperemia

Corneal Ulcers Dx: Fluorescein dye- absorbed by stroma, not by epithelium (green uptake of dye) WARN client about fluorescent green dye !! Tx: Topical Atropine Topical abx Sx Meds. w/ cortisone slow healing & makes condition worse Frequent re-evaluations needed to monitor progress/healing Warn clients as orange dye turns green & exits via tear ducts/nose, causes green nasal discharge. When animal licks at it, gets a fluorescent green tongue!!

Pannus: Chronic Superficial Keratitis Superficial corneal vascularization & infiltration of granulation tissue (lymphocytes & plasma cells) Progressive, bilateral, degenerative, can result in blindness Cause – immune-mediated, animals at > 5000 ft most susceptible (G.shep, B. Terv, B. Collie, Greyh, SibHusky) C/S: breed predisposed with opaque lesion – pink or tan Dx: corneal scraping – infiltrate, eye exam Tx: Antiinflam. for life of patient, +/- subconj. inj., cryosurgery, superficial keratectomy No cure Treatment to maintain regression of lesion is life-long

Pannus

“KCS”: Keratoconjunctivitis Sicca Loss of both lacrimal glands Viral inf., drug-related toxicities, Imm-mediated dz, inflamm, breed predisp., congenital abn Most cases idiopathic, older >7 yr. – neutered Clinical signs Recurrent conjunctivitis Corneal ulcers Keratitis Cornea & conj. appear dull, dry, & irregular Ocular discharge Blepharospasm Crusty nares a.k.a. “ Dry eye”

KCS cont’d ….. Dx: Tx: Failure to treat will result in blindness Schirmer Tear Test <15mm/min on repeat testing (k9 15- 25, fel 11-23) NOTE: Perform this test 1st 2nd: Fluorescein dye –assess ulcer presence Tx: Stimulate tear prod. w/meds (cyclosporine) Topical art. tears Surgery if medical tx are unsuccessful (parotid duct transposition) Failure to treat will result in blindness

Cataracts : Most common dz. involving the lens An opacity of the lens sufficient enough to cause a reduction in visual function – aging cells w/in lens become dehydrated & overlap each other, producing a central change in the reflection of light- lens may appear grey and opaque Freq. cause of blindness in dog, occas. seen in cat Etiology: Inherited, secondary to diabetes mel., hypocalcemia, trauma, nutritional deficiency, electric shock, uveitis, or lens luxation (Photo Credits: dog-health-handbook.com )

Cataracts cont’d Clinical signs Dx: Progressive loss of vision Opaque pupillary opening Signs related to systemic dz. (diabetes mellitus or hypocalcemia) Dx: Complete eye exam/Assess via obstacle course/ Lack of menace /Failure to track visual responses Photo Credits: petdig.com

Cataracts cont’d…….. Pupillary light response is usually normal Tx: Sx removal Tx of any other dz

Anterior Uveitis Inflammation of the uvea (iris, ciliary body, choriod) Trauma, extension of local infx, foreign body, neoplasm, thermal trauma, parasites, protozoa (bact, viral, mycotic dz – hematogenous spread) C/S: epiphora, photophobia, blepharospasm, +/- vision defects, corneal edema, chemosis, prolapsed 3rd eyelid, pain, change in iris color Dx: c/s, hx, labs, x-ray, ultrasound, tonometry Tx: I.D. & elim. cause, control inflamm w/topical steroids (w/o tx, vision will eventually be lost)

Progressive Retinal Atrophy Group of hereditary retinal disorders seen in many breeds of dogs (can occur in cats, but not as frequently) Toy poodles, min poodles, goldens, Irish sett, cockers, min sch, collies, samoyed, gordon sett, Norw. Elkhound C/S: defective night vision, slowly progressive loss of day vision, cataract formation Dx: labs, eye exam of retina No Tx. currently exists

Horses Entropion Conjunctivitis – Summer/ dry, dusty condition /flies Corneal ulcers Cataracts – Sx. prognosis is good in foals Many blind horses can still be ridden safely, if owner doesn’t exceed horse’s ability & comfort level … (or the owner’s !)

“Moon Blindness” Periodic Opthalmia, Recurrent Uveitis Comes & goes/ exact cause undetermined Many animals have high Lepto antibody titer Signs: cloudy eye, blepharospasm, excessive tears Dx: visualization of protein flare in fluid of anterior chamber, affected eye may be smaller, corneal stain, Lepto titer Tx: topical corticosteroids, atropine, banamine or Subconjunctival long-acting steroid injections

Sheep and Goats Entropion – most common ocular abnormality in neonatal lambs Infectious Conjunctivitis (Pinkeye) – responds well to medication – herd management Cataracts – most common lens abnormality in sheep and goats