SAM Exam 5 -Ophthalmology

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Reflex Testing

• PLR: CN II (A) + III (E)

  • Direct: Pupil constricts in the same eye exposed to light

  • Consensual: Pupil constricts in the opposite eye

• Dazzle: CN II + VII + brainstem

  • Indicates intact retina

  • Useful even when the animal is blind

• Menace: CN II (A)+ VII (E) + retina + brainstem + cortex

  • Do not use a closed hand

  • Normal: blink or avoidance movement, Positive at 20/400

  • Absent: puppies or cortical blindness

• Corneal: CN V (A) + VII (E) + VII (E)

  • Use a wisp of cotton to touch corneal center

  • Normal: globe retraction + blink

• Palpebral: CN V (A) + CN VII (E) + brainstem

  • Test with brisk touch at medial/lateral canthus

• Swinging Light: Detects Marcus-Gunn pupil (RAPD)

  • Pupil dilates when light swings to affected eye

Visual Field Testing

• Light Maze Test (Photopic)

  • Why: Evaluates cone function (day vision).

  • How: Performed under normal room lighting.

  • Results: 

    • Normal: Moves confidently, avoids obstacles.

    • Abnormal: Hesitant, bumps into objects

• Dark Maze Test (Scotopic)

  • Why: Evaluates rod function (night vision)

  • How: Performed in dim or dark lighting.

  • Results:

    • Normal: Navigates well, minimal hesitation.

    • Abnormal: Disoriented, collides with obstacles 

• Cotton Ball Test: Drop a cotton ball silently → check visual tracking

  • good for dogs, cats often ignore

tear Tests

• Schirmer Tear Test (STT)

  • Why: Measures tear production

  • Results: 

    • Normal: >15 mm/min

    • Abnormal: <15 mm/min = KCS

• Tear Break-Up Time (TBUT)

  • Why: Evaluates tear film stability, quality of tears

  • How: Apply fluorescein dye to cornea and measure time until tear film breaks (dry)

  • Results: 

    • Normal: >20 seconds

    • Abnormal: <10 seconds

Nasolacrimal Testing

• Irrigation Test

  • Why: Confirms nasolacrimal duct patency

  • How: Cannulate punctum and flush with saline or fluorescein solution

    • Rx: topical anesthesia

    • Antegrade: all species.

    • Retrograde: large animals.

  • Results: 

    • Patent: Fluid exiting opposite punctum or nose 

    • Obx: Reflux through same punctum

• Jones Test

  • Use: Confirms flow of Nasolacrimal System

    •  but not full patency

  • How: Fluorescein stain

Ocular Stains

• Rose Bengal Stain

  • Why: Detects devitalized or stressed epithelial cells

    • KCS, viral keratitis, or fungal keratitis

  • How: use topical anesthetic before application

    • Causes mild irritation

  • Results: Positive = Stains damaged cells and mucin-deficient areas

• Fluorescein stain

  • Why: detects ulcers, TBUT, nasolacrimal drainage, Seidel’s test, tear break up time

  • Normal dog/cat: 15-25mm

  • Cat: <5-10mm = issues

  • Result: 

    • Positive: corneal ulcer

      • exposed corneal stroma

    • Negative: intact epithelium or Descemet’s membrane

Topical Ocular Anesthetics

• Rx: Proparacaine 0.5%

• Onset: rapid onset 15-20 sec

• DOA: 15-20 min

• Prolonged use: 

  • Decreased effectiveness

  • Delayed corneal healing

  • Corneal erosions and keratitis

Tonometry

• When: Any red/cloudy or painful/blind eye, Breeds that are

  predisposed, history of glaucoma in the opposite eye, any medically controlled glaucoma cases, abnormal pupils!!

• Why: IOP, glaucoma, uveitis

  • Only one

  • Pressure on inner cornea = pressure on retina

• Tools: 

  • Indentation (Schiotz): Requires anesthesia, less precise, unreliable - indention

  • Applanation (Tono-Pen): requires anesthesia Measures corneal flattening, accurate and practical, 6 readings with 3 touches -  applanation

  • Rebound (TonoVet): No anesthesia required, ideal for horses - rebound

• Results: 

  • Normal: 10-25 mmHg

  • High: glaucoma, >40mmHg

  • Low: uveitis <10mm

Ophthalmoscopy

• Indirect: wide field, image is inverted and reversed

  • general retinal evaluation

    • Use magnifying glass

• Direct: limited field, upright, magnified image

  • localized retina or optic nerve lesions

    • otoscope only

• PanOptic: wide field, detailed image

  • small animals

Anterior and Posterior Eye Visualization

• Ultrasound

  • Why: when the posterior segment cannot be visualized - blood or cataracts

    • Lens, vitreous, retina, optic nerve, and uveal tract

  • Detects: Lens luxation, Retinal detachment, tumors, uveal cysts, hemorrhage, cataracts 

• Brightoscopy (Slit lamp)

  • Use: examination of the anterior eye structures

    • Adnexa, eyelids, Conjunctiva, cornea, anterior chamber, Iris,  lens, anterior vitreous

Electroretinogram

• Why: distinguishes retinal from optic nerve blindness

  • Past cataract Sx, SARDS, unkown blindness 

• Tools:

  • Scotopic ERG: Tests rod function (dark-adapted)

  • Photopic ERG: Tests cone function (light-adapted)

• Results:

  • Cataract with normal ERG:  intact retina

  • Cataract with flat ERG: retinal degeneration

Layers of the Cornea

• Cornea Epithelium “english muffin” non-keratinized!

  • Fxn: mechanical barrier to imbibition of fluid by the stroma

  • Anatomy: Anchoring fibrils for attachment

    • lipophilic: fluorescein not absorbed

  • Healing: 

    • Cell turnover 7 days, ulcers should heal 48-72h hours!!

    • Damage = focal stromal edema in area of the ulcer

• Stroma “dry sponge” No blood vessels

  • Anatomy: 90% of total corneal thickness, Hydrophilic = absorbs stain/fluid if there is break in epithelium,

  • CN V trigeminal for outer 3rd innervation - superficial ulcers are more painful then deep ones

    • Diffuse edema can look blue and cloudy

• Descemet’s membrane

  • Fxn: BM of endothelium

  • Anatomy: Does not retain fluorescein, Elastic

    • rim of ulcer will stain but not the center - almost rupture: Emergency

• Endothelium: no blood vessels, NO undergo mitosis!

  • Fxn: physical barrier and metabolic pump to prevent stromal edema
    Healing: cellular enlargement and migration, no regeneration, lose with age!!

    • Damage = diffuse edema(blue eyes)

    • Look like honeycombs

Diagnostic tests for corneal abnormalities

• Examination

  • Finoff

  • Biomicroscopy

• Culture/Cytology

• Schirmer tear test

• Fluorescein dye

• Biopsy

Dermoid (Choristoma)

• Et: congenital corneal condition 

• Cs: Normal tissue in abnormal location

• Sig: Dachshund, Dalmatian, Doberman, GSD, Saint Bernard

• Tx: Superficial keratectomy - #64 beaver blade

Superficial Corneal Ulcers

• Cs: Extreme pain, focal edema

• CN 5 trigeminal nerve supplies outer 1/3 of cornea 

• EXAM #1: Look for eyelid abnormalities, location/size of ulcer, FB, hair, infectious causes 

• Tx: Heal within 48-72 hours if cause removed

  • If not healed after 5 days: cause persists, infection present, indolent ulcer present, FHV-1

Indolent Ulcer

• Et: Recurrent epithelial erosion, failure of BM epithelial attachment

• Sig: Old, boxers

• Cs: Superficial, mild pain, loose epithelial borders,  focal edema, mid aged/older dogs

  • Chronic

• Tx: Client education, debridement, keratotomy (100%), tetracycline(topical), diamond burr (93%)

  • Recheck every 7-14 days, long term treatment

Feline Herpesvirus

• Et + Sig: 3 stages

  • Ophthalmia neonatorum: kittens <4 weeks

    • Symblepharon – fuses in utero 

  • Adolescent cats: ocular + respiratory

  • Adult cats: ocular only

• Cs: Dendritic(classic) or punctate superficial ulcers, conjunctivitis, keratitis

• Dt: History, based on response to therapy + Cs

  • PCR unreliable and expensive

• Tx: Cidofovir(eye drops), Famciclovir (do not compound),l-lysine

  • Do not taper dose

  • ± Topical mucinomimetic (tear mucus supplement)

  • Recurrent flare ups w/ stress

Mid-Stromal Corneal Ulcer

• Et: Often with anterior uveitis

• Cs: focal edema, pain

• Tx: Medically managed, Neomycin–bacitracin–polymyxin, Levofloxacin, Gatifloxacin, atropine (<4x daily), fluxin (horse)

  • Managed medically

  • No topical corticosteroids

Deep Descemetocele Ulcer

• Cs: Perforation imminent, focal edema, pain

• Dt: Fluorescein negative centrally

• Tx: Conjunctival flap or corneal-conjunctival transposition

  • Surgery + medical therapy

  • Do not use third eyelid flap

Melting Keratomalacic Ulcer

• Deep ulcer - surgery often indicated, debride melting portion

  • Superficial Keratectomy w/ conjunctival graph 

• Et: Enzymatic corneal destruction

  • Involves PMNs, keratocytes, and bacteria

    • Pseudomonas, β-Strep

• Cs: focal edema, pain

  • Extremely rapid progression

• Tx: q 1-2h ofloxacin, levofloxacin, gatifloxacin, serum, tetracycline, debridement

  • Aggressive: Anticollagenase + antibiotics + surgery

Corneal Edema

• Anterior uveitis. glaucoma 

• Endothelial dystrophy - breed related, age

• Anterior lens luxation

• CHECK PRESSURE

Loss of Corneal Transparency

• Edema

  • Focal: due to corneal ulcer

  • Diffuse: due to endothelial damage

    • Et: Anterior uveitis, Glaucoma, Endothelial dystrophy, Anterior lens luxation

    • Dt: IOP

    • Tx: Hyperosmotic therapy, Conjunctival graft, Fresh corneal transplant

• Pigmentation

  • Chronic superficial irritation

  • Vascularization

  • Sequestrum or melanoma

• Scarring

  • Et: History of previous ulcer or trauma

  • Cs: vascularization, absence of pain

• Infiltrate

  • Cellular: inflammatory or neoplastic

  • Non-cellular: crystalline (cholesterol, mineral)

Corneal Sequestration

• Et: Associated with herpes keratitis, topical steroids, grid keratotomy

• Sig: cats

• Cs: Brown-black corneal lesion, pain, may spontaneously slough, often vascularized 

• Dt: Fluorescein negative

• Tx: Superficial keratectomy

  • Post-op antibiotics, atropine, artificial tears following sx

• This dz could happen w/ steroids and grid keratotomy

Melanoma

• Corneal Epibulbar (limbal):

  • Benign pigmentation

  • Excisional biopsy if enlarging

• Eyelid: dogs, horses, benign 

• Conjunctival

  • Dogs: benign 

  • Cats: Melignant 

• Intraocular: 

  • Canine: benign, Labs, GSDs

  • Feline: malignant, high mitotic index

Nodular Granulomatous Episclerokeratitis (NGEK)

• immune mediated 

• Et: Non-neoplastic inflammation mass at temporal limbus (1 or both eyes) - Lateral canthus

  • Lymphocytes, plasma cells, histiocytes

• Sig: Cocker Spaniels, Collies

• Cs: Loss of Corneal Transparency

• Tx: topical Dexamethasone, cyclosporine, tacrolimus, systemic: very rare - azathioprine, cyclosporin

Chronic Superficial Keratitis (Pannus)

• “degenerative pannus”

• Et: Immune mediated

• Sig: GSD, Greyhounds

• Cs: progressive corneal vascularization and pigmentation beginning at inferior-temporal limbus - will progress over entire cornea

  • starts in lateral canthus then progresses

• Tx: topical dexamethasone, Cyclosporine, tacrolimus, Reduce UV exposure: doogles

Eosinophilic Keratitis

• Cats, lateral limbus 

• Et: Limbal orientation of mast cells and eosinophils (one or both)

• Cs: Loss of Corneal Transparency

• Tx: Topical Cyclosporine, corticosteroids(herpes risk), Oral: Ovaban® (megestrol acetate, Cats) #1 but best to be topical

  • 7d then taper to lowest dose

  • Ovaban side effects: DM, weight gain, cancer, behavior changes

Corneal Dystrophy and Degeneration 

• Non-cellular corneal infiltrates

  • Crystalline materials: cholesterol or mineral 

• Dystrophy

  • Cs: Non-painful, Non-vascularized, Bilateral, Loss of Corneal Transparency

  • Tx: No treatment needed, steroids make it worse 

• Degeneration

  • Et: Secondary to inflam, cushings, hypothyroid, hypercalcemia, DM, steroid use

  • Cs: Loss of Corneal Transparency, deposits/crystals in eye 

Corneal Trauma

• Sharp: leaks, deflates, reparable 

  • Ex: cat claws 

• Blunt: explodes, compresses

  • Ex: Horses

• Poor Prognosis Indicators

  • Limbus involvement

  • Significant hyphema (blood in front of eye)

  • Lens perforation

    • US if poor visibility of virtuous

  • Large Uveal prolapse - remove eye

  • No consensual PLR

• Chemical Injuries 

  • Et: Soaps (mild), Acids (severe), Alkalis(critical/worst)

    • Severity = duration and concentration

  • Tx: irrigate sterile eyewash

• Lacerations/perforations:

  • Perforating: punctures, pupil mis-shaped : double layer

    • Remember: corneas don’t bleed only: iris or lens

    • Non-perforating: flap - cut it off or suture back on

Adnexa

• “Everything but the globe”

• Extraocular muscles

• Eyelids

  • Eyelids protect and serve the cornea.

  • Corneal diameter averages 16 mm.

  • Meibomian glands - sebaceous glands

• Lacrimal system

  • Efferent + Parasympathetic: CN VII.

  • Afferent: CN V

  • 2 puncta: except rabbits (only one).

  • Tear production + drainage: 2 canaliculi → nasolacrimal duct → nasal vestibule.

• Conjunctiva

  • Goblet cells: Produce mucin component of tear film

  • Palpebral: lines inner eyelid

  • Bulbar: covers sclera

• Third eyelid (nictitating membrane)

  • Reflection (fold) of conjunctiva.

  • Has T cartilaginous support

  • Responsible for 50% of aqueous tear film production.

Macroblepharon

• Long eye lids

• Et: Abnormally large eyelid opening (palpebral fissure).

• Cs: cause of nearly all entropion and ectropion cases

• Dt: maximum canthus-to-canthi distance measurement under GA 

  • Normal = 24-26 mm

• Tx: Permanent Lateral Canthoplasty

  • surgical shortening improves corneal protection

    • Look where the canthus collapses & notching at the fold .

  • Ends should be tucked away from the cornea.

    • Double layer closure, second layer cruciate 

Entropion

• Et: Inward rolling of the eyelid margin

  • Cats: lateral canthal, unilateral

  • Sm dogs: medial canthal 

• Cs: corneal irritation

• Tx:

  • **Modified Hotz-Celsus Procedure: Permanent

    • Incision made approximately 2 mm from eyelid margin(hairline)

    • Small elliptical section of skin is removed

    • 6-0 Surgilene in simple interrupted pattern(start in the middle)

  • Permanent Lateral Canthoplasty: lateral canthal entropion

    • Ends should be tucked away from the cornea

  • Permanent Medial Canthoplasty: Medial Canthal Entropion Pugs

    • Excision of caruncular tissue, reduces eyelid length medially

• 1st Q - How old is the dog? fix them while you can

  • remove the caruncle 

Advanced Cosmetic Surgical Eyelid Procedures

• Brow Sling - shar pei

  • Used when excessive skin or drooping brow causes eyelid malposition

  • Lifts upper eyelid region and corrects sag

• Rhytidectomy (Facelift/forehead Technique)

  • Tightens periocular skin to reposition eyelids

Ectropion

• Et: Macroblepharon

• Cs: Outward rolling of eyelid margin

• Tx: Lateral canthoplasty, Wedge excision

  • “KISS” — Keep It Simple, Stupid

Abnormal eyelid hair emergence

• Distichia - tx if bothering pet

  • Et: Hairs emerging from Meibomian gland openings

  • Tx: kill the follicle, Epilation (temp), cryosurgery, Electroepilation, CO₂ laser

• Ectopic Cilia - always need tx

  • Et: Hairs emerging from palpebral conjunctiva

  • Cs: irritating to the cornea

  • Tx: surgical removal or ablation

Eyelid Agenesis

• Et: Lack of upper eyelid development

  • Usually superior-temporal

  • Often bilateral

• Tx: Lip-to-lid transposition, Rotational grafts

Eyelid Neoplasia

• Dog: Histiocytoma, BCT, Melanoma, Adenoma, MCT, GCT

  • Common, benign

• Cat: SCC, MCT, Fibrosarcoma

  • Aggressive

• Horse: Sarcoid, SCC, Melanoma, MCT, Lymphosarcoma, BCT, Papilloma - ASK age and purpose of the horse

  • SCC: older horses, locally aggressive, low metastasis rate

  • Sarcoid: younger horses 

  • Intralesional chemo - medial canthus 

• Tx: Benign neglect(dogs), excisional biopsy, Cryosurgery, CO₂ laser, Chemo, Radiation

  • Can remove 1/3 of the eye lid @ 6/12 o’clock for equal closure

  • double layer closure, 2nd layer w/ cruciate (identical on both sides)  

Eyelid Reconstruction

• H-plasty

  • Used for larger excisions

  • Preserve as much conjunctiva as possible

  • Incisions diverge

• Z-plasty

  • Lateral canthal reconstruction

  • Repositions tension lines

  • Common in feline eyelid tumor repairs

• Axial pattern flap

  • Cutaneous artery and vein for blood supply

  • Medial canthal reconstruction

Blepharitis

• Et: Juvenile pyoderma, Herpes, Chalazion (Meibomian gland blockage), Pyogranulomatous inflam

• Tx: systemic antibiotics, steroids, compress

  • Approach as derm condition

Eyelid Lacerations and resection

• Two layer closure, 2nd layer cruciate 

• Conjunctiva: 5-0 to 6-0 absorbable, horizontal mattress

• Skin: 5-0 to 6-0 nonabsorbable, cruciate at margin + simple interrupted

• Avoid excessive debridement

• Never amputate an eyelid pedicle!!!

Nictitating Membrane

• Reflection of conjunctiva

• Cartilagenous support

  • “T” cartilage

• Gland of the nictitans

  • Aqueous portion of tear film

Clinical signs of conjunctivitis

• Conjunctival hyperemia

• Chemosis

• Lymphoid follicles

• ocular discharge

• Dx: Complete ophthalmic examination

  • Schirmer Tear Test

  • Cytology

  • Biopsy

  • Culture and sensitivity

  • Vital stains

3rd eyelid Follicular Conjunctivitis

• Et: non-specific inflammatory response

  • seasonal

• Sig: young dogs

• Cs: Conjunctival hyperemia (redness), Chemosis (swelling), Lymphoid follicle formation, Ocular discharge

• Tx: steroids

  • May resolve with age

Allergic Conjunctivitis

• diagnosis of Exclusion

• Et: non-specific inflammatory response

  • Seasonal or atopy/skin allergies

• Sig: young dogs, rare in cats

• Cs: Conjunctival hyperemia (redness), Chemosis (swelling), Lymphoid follicle formation, Bulbar conjunctival follicles , Epiphora (tearing), Mucoid discharge

• Dt: Diagnosis of exclusion

• Tx: antihistamines, anti-inflammatorys

Chlamydophila felis

• Et: zoonotic

• Sig: cats

• Cs: conjunctivitis

• Dt: elementary bodies in conjunctival epithelial cells (cytology)

• Tx: Tetracycline, Erythromycin,  macrolides

Parasitic conjunctivitis

• Et: non-specific inflammatory response

  • Thelazia, Onchocerca, or Habronema

• Sig: horses

• Cs: Conjunctival hyperemia (redness), Chemosis (swelling), Lymphoid follicle formation, Ocular discharge

Eosinophilic Keratitis + Conjunctivitis

• Et: non-specific inflammatory response

  • Seasonal, IM

• Sig: horses

• Cs: Conjunctival hyperemia (redness), Chemosis (swelling), Lymphoid follicle formation, Ocular discharge

• Dt: cytology

• Tx: Superficial keratectomy, diamond burr debridement

Scroll Cartilage

• Et: Curved or everted cartilage of the third eyelid

• Tx: Thermal cautery

Prolapsed Gland of the Third Eyelid

• Cs: Cherry Eye

• Tx: Surgically replace (Morgan Pocket or anchoring), benign neglect, remove

  • all KCS risk: Monitor STT for life

Third Eyelid Neoplasia

• Adenocarcinoma 

  • Dog

• Papilloma

• SCC

  • Equine: Excisional biopsy, Cryosurgery

• Lymphosarcoma

Inflammation of the Nictitans (Plasmoma)

• Et: Chronic IM inflam of the third eyelid

• Tx: steroids, immunomodulators

keratoconjunctivitis sicca

• Et: IM, Cherry eye Sx, Irradiation, drugs, DM, hypothyroid, facial denervation or palsy,

  • Qualitative: Goblet cell loss or dysfunction and decreased Mucin Production

  • Quantitative: Decreased Aqueous Production

• Sig: small dogs and brachycephalic breeds

• Cs: Discomfort, Mucopurulent discharge, Blindness, conjunctivitis 

  • Ulceration, Vascularization, Pigmentation, Keratinization, SCC

• Dt: 

  • Quantitative: STT <15 mm/min

  • Qualitative: TBUT <10 seconds

• Tx: Lacrimogenics, tear supplements, anti-inflammatories, Parotid Duct Transposition

  • Lacrimogenics: Cyclosporine A, Optimmune, Tacrolimus → Tear stim

  • PDT: Reroutes parotid salivary duct to the conjunctival fornix

  • Treat before STT values drop severely, do not wait

Tear Overproduction

• Et: Usually secondary to irritation or pain

  • Tear Outflow Abnormalities

• Cs: May result in epiphora (overflow tears)

Congenital Nasolacrimal Abnormalities

• Missing lower punctum: dogs

• Dacryops: congenital duct malformation

• Imperforate nasal meatus: equine, camelids

• Medial trichiasis: misdirected hair causing drainage interference

Imperforate Punctum

• Et: involves inferior punctum of nasolacrimal system 

  • Tear Outflow Abnormalities

• Sig: Cocker Spaniels

• Tx: irrigate superior punctum and surgically open inferior punctum

Atresia of Nasal Opening

• Et: Tear Outflow Abnormalities

• Sig: equines and camelids

• Dt: lack of fluorescein exit from nostril after ocular application

• Tx:

  • Pass catheter to nasal vestibule

  • Incise nasal mucosa to expose punctum

  • Leave silicone tubing in place 6 weeks post-surgery

Acquired Nasolacrimal Obstruction

• Et: Dacryocystitis, FB

  • Tear Outflow Abnormalities

• Tx: flushing, imaging, surgical repair

Structures of the Vascular Tunic

• Iris

  • Regulates the amount of light entering the posterior portions of the eye

  • Blood Aqueous Barrier

• Ciliary body

  • Located posterior to iris

  • Source of aqueous humor, Lenticular zonules(holds the lens in place)

  • Blood Aqueous Barrier

• Choroid: posterior portion of eye

  • Provides nutrition:

    • Outer portions (rods & cones) of retina in dog, cat, cow

    • All of retina in horse

  • Tremendous blood flow → cools retina

    • The eye has the highest blood flow (by weight) of any organ

  • Contains Tapetum

Muscles of the Eye

• Sphincter Muscle

  • Smooth muscle in Mammals

  • Striated muscle in Birds

  • Miosis = constriction

  • CN III parasympathetic control

• Dilator Muscle

  • Smooth muscle in Mammals

  • Striated & smooth in Birds

  • Sympathetic control

  • Mydriasis = Dilation of pupil

Horner’s Syndrome

• Et: Denervation of sympathetic nerve supply to eye

  • 1st order: CNS neoplasia, trauma, inflammation

  • 2nd order: spinal cord, thoracic mass, cervical mass/trauma, iatrogenic

  • 3rd order: otitis, guttural pouch disease, endocrine disorder, orbital disease, idiopathic

• Cs: Miosis, Ptosis, Enophthalmos, Prolapse of third eyelid, Ocular hyperemia

  • Unilateral sweating  →  Horses

• Dt: 

  • PE: Radiographs, Otic exam, CT of tympanic bulla, Guttural pouch endoscopy

  • Phenylephrine Response: 

    • Rapid, strong response → 3rd order lesion

    • No response = likely 2nd order lesion

Persistent Pupillary Membranes

• Et: Remnants of fetal iridal vascular arcades

  • Originate from collarette zone of iris

  • Attach to cornea, iris, or lens

• Sig: Basenji

• Tx: None

• Different from Synechia: pupils edge

Heterochromia

• Et: genetic

  • Alone = no significance

  • May associate with ocular/systemic abnormalities

  • white coat / deafness in cats

• Sig: blue merle, appaloosa, Siamese, harlequin

• Cs: colour variation within or between irides, iris stroma lacks pigment - multi colored blue eyes

Coloboma

• Sig: Notch defect in iris

  • usually inferonasal

• Dt: Differentiate from iris atrophy(Swiss cheese/spiderweb eyes)

• Rottweilers

Iris Cyst

• Et: Cystic accumulation of aqueous humor within posterior iris or ciliary body epithelium

  • Acquired lesion

  • Can maintain attached or floating around 

• Dt: Transilluminates

• Tx: Neglect, laser ablation

Anterior Uveitis

• Prostaglandins play a huge role!!

  • Rule out other ocular/systemic causes #1 ~ 50% have systemic dz

• Et: idiopathic, Corneal ulceration, lens induced, trama, cancer, IM, bacteremia, viremia, septicemia

  • Dogs systemic: Tick dz, fungal dz, ICH, Brucella, Uveo-dermatologic syndrome (depigmenting), HW

• Cats: FeLV, FIP, Toxo(2 titers), FIV, Crypto, Bartonella, Lymphosarcoma (#1 tumor), Melanoma(primary tumor)

• Cs: Miosis, Flare(sunrays), Redness, Photophobia, Pain, Keratic precipitates, Hypotony

• Dt: histo/culture, US, CBC, IgG + IgM titer 

  • Remember coinfections

• Tx: Stop the inflammation #1, Antimicrobials, Immunotherapy, Chemo, Atropine(no more then x4), steroids, NSAIDs

  • Systemic or topical

Posterior Uveitis

• Systemic dz!

• Et: Bacteremia, septicemia, mycotic infections, disseminated neoplasia

  • High choroidal blood flow → predisposed to blood-borne disease

• Cs: edema, exudate, granulomatous/non-granulomatous, hemorrhage, neoplasia, retinal thinning, depigmentation, vascular loss

• Dt: color change on fundic exam, histo/culture, US, CBC, blind eye=vitreocentesis

• Tx: NSAID, steroids(if know cause), immunosuppressives

  • Requires systemic meds

Hyphema

• Blood filled sac

• Et: Blood in anterior chamber

  • Coagulopathies/vascular disorders, Trauma, Neoplasia, Hypertension, Anterior uveitis

• Dt: IOP #1, US #2

• Tx: Treat underlying cause(if known), Cage Rest

  • Do not drain hemorrhage!

Lipid Aqueous

• Fat inside the eye, tomato soup w/ milk

• Et: systemic lipemia - dont feed fatty foods

  • No ocular abnormality required

• Cs: Flare appears milky, non-painful

Iris Atrophy

• Et: Swiss cheese / spiderweb eye

  • Primary: dogs, Poodles

  • Secondary: Uveitis, glaucoma

• Cs: abnormal PLR

  • Affects iris sphincter

• Tx: none, make sure this is the dz

Intraocular Tumors

• Et: Primary = happy, 2ndary = pissed off 

  • Melanoma: Primary, threatens the eye

    • Canine: benign

    • Feline: malignanthigh mitotic index, flat yellow

  • Ciliary Adenoma: Primary, remove eye!

  • Feline Spindle Cell Sarcoma: Primary, remove eye!!

    • highly malignant, metastasizes via optic nerve, post-traumatic, uveitis

  • Secondary:most  common Lymphosarcoma, sarcoma, carcinoma

• Cs: Hemorrhage, Uveitis, Lens displacement/luxation, Cataract, Glaucoma, Retinal detachment

• Tx: 

  • Primary: enucleation if symptomatic

  • Secondary: Treat prime disease, enucleation

    • Eye = bystander

Aqueous Production

• Production: Ciliary body

  • Involves carbonic anhydrase, ATP, glucose, and local environment

  • Inhibited pharmacologically by carbonic anhydrase inhibitors (CAIs)

• Outflow Pathway: Ciliary epithelium → between iris and lens → pupil → anterior chamber → Iridocorneal angle → trabecular meshwork → scleral venous plexus

Pharmacologic Effects on Aqueous Outflow

• Pilocarpine:

  • Contracts ciliary muscle → ↓ resistance → ↓ IOP

  • Contraindicated in uveitis

• Atropine:

  • Paralyzes ciliary muscle → ↓ outflow → ↑ IOP

  • Contraindicated in glaucoma

Glaucoma

• Genetic or 2ndary

  • prime: bilateral w/in 2y, 2nd: unilateral besides: lens luxation terriers

• Increase in IOP w/ decreased outflow - no atropine!

• Cs: Redness, Corneal edema, Engorged episcleral vessels, Dilated pupil, absent PLR**, Corneal striae, Retinal degeneration, Cupped disc, Buphthalmos, Pain

  • Chronic = Not an emergency – vision loss irreversible

  • Acute = Emergency– vision loss reversible

• Dt: increased IOP >40 mmHg !!

• Rx: 

  • Acute: Carbonic anhydrase inhibitors (Methazolamide/Dorzolamide/Brinzolamide/Cosopt), Prostaglandins (Latanoprost) #1!!!, passive paracentesis

  • Horse: timolol, cosopt

  • Chronic: eyes blind! Evisceration with prosthesis, Enucleation

• Sx: 

  • Acute: Laser surgery (vision saved)(TransScleral CycloPhotocoagulation)

  • Chronic: Intravitreal Injection of Cidofovir or Gentamicin, enucleation(most common), prosthesis

Lens Anatomy

• Embryo: Originates from surface ectoderm

• Path: Lens is not perceived as part of self

  • Exposure to lens proteins results in inflammatory response → Lens-induced uveitis

• Physio: 

  • Avascular: depends on aqueous humor for nutrients and waste removal, issue = cataract

  • Growth: anaerobic glycolysis (hexokinase), continues to grow throughout life(compact/dense)

• Composition: 35% protein, 65% water

  • Capsule:anterior(Y) thick / posterior (thin)

  • Epithelium: anterior

  • Cortex: anterior/posterior

  • Nucleus: central

  • Zonules: 360°, Anterior “Y” suture + 50–70 μm, Posterior 2–4 μm

Lenticular Sclerosis

• Normal w/ aging

• Et:  increased central density

  • Normal senile chage

• Sig: All dogs and cats >6 years old

• Cs: Bilateral, symmetrical, transparent

  • Surgically Harder Lens

• Dt: Does not prevent fundus/retina exam

• Tx: no treatment required

Cataracts

• loss of transparency, Irreversible! Ghost eyes

  • Will NEVER interfere w/ afferent arm PLR!!**

• Et: Hereditary, Metabolic, Inflam, Traumatic, Toxic, Nutritional, Radiation, Electric, DM

• Equatorial: #1, very progressive, worst place!!

  • Hypermature: cant see in/out, no menace!

  • Undergoing liquefaction in all or part of the lens: dries out

    • Lens proteins exposed → immune response → Lens-induced uveitis

• Sig:<6 years (developmental)

  • >6–9 years (senile)

• Dt: US, Electroretinogram

  • Retinal detachment: Immature < Mature < Hypermature

  • PLR unaffected 

• Tx: Early Referral

  • None: highest failure 

  • Rx: Anti-inflammatory treatment

  • Sx: #1,  Phacoemulsification + IOL (Artificial lens)

Lens Luxation

• Et: genetic, trauma, glaucoma, uveitis

• Sig: Terries (primary)

• Cs: Iridodonesis (iris tremor), Phacodonesis (lens wobble), Aphakic crescent, Corneal edema

  • Anterior luxations: painful, epiphora, blepharospasm, redness

  • Posterior luxations: may have no overt signs

• Dt: IOP

• Tx: 

  • Anterior luxation: w/in 24h: Sx(acute, 1mary), artificial lens

    • Best treatment  = referral 

    • No latanoprost! 

  • Posterior luxation: Sx, miotic agents (latanoprost!!/pilocarpine, manage IOP

Orbit Anatomy

• Carnivors: Incomplete, Forward placed globe

• Herbivour: Complete, Laterally placed globe

• Extraocular muscles: (LR₆SO₄)³

  • 4 rectus muscles → CN6

  • 2 oblique muscles→ CN4

  • Retractor muscle → CN3

  • Levator muscle → CN3

• Glands:

  • Lacrimal gland

  • Zygomatic salivary gland(floor of orbit)

  • Gland of the 3rd eyelid

  • Harderian gland (cow, pig, rabbit)

• Abnormalities: Exophthalmos, Enophthalmos, Strabismus(lazy)

  • Intraconal: bug eyes

  • extraconal: sideways eyes

• PE: retropulsion of both eyes!

Orbital Abscess and Cellulitis

• Acute

• Et: Possible extension from adjacent tissues (mouth, sinus, salivary gland)

• Cs: sudden onset: Painful opening mouth, exophthalmos, elevated 3rd eyelid, fever, LN enlargement, leukocytosis, swelling behind last upper molar in mouth

  • acute

• Tx: Systemic antibiotics, Soft food, Corneal protection, Surgical drainage

  • Do not probe or irrigate!!

Orbital Myositis

• Et: IM

• Sig: Usually bilateral exophthalmos

• Cs: Exophthalmos, 3rd eyelid elevation, difficulty opening mouth, swollen muscles of mastication and extraocular muscles

• Tx: immunosuppression steroids (Prednisolone, Azathioprine)

Orbital Neoplasia

• Chronic 

• Et: malignant >90% dog/cats

  • Dog Primary: osteosarcoma

    • Secondary: adenocarcinoma

  • Feline Primary: osteoma

    • Secondary: SCC

• Cs: Exophthalmos, Globe indentation, unilateral, Slow progression, Less painful opening mouth

• Dt: FNA, biopsy, US, Rads, CT, MRI

• Tx: enucleation, exenteration, radiation, chemo

• Px: grave

Proptosis

• Et: Incomplete orbit in dogs and cats

• Sig: squish face

• Cs: Acute exophthalmos with eyelid entrapment behind the globe, severe chemosis, subconjunctival hemorrhage, blindness, keratitis/corneal ulcer, hyphema, rectus muscle avulsion (shortest muscle), periorbital trauma

  • sequela: Lateral or dorsolateral strabismus, Neurotrophic keratitis, Lagophthalmos, KCS), Blindness (optic nerve atrophy), Phthisis bulbi

• Tx: good prognosis <2 EOM tear, pupils miotic. replace #1 or enucleate (can enucleate later, Water-soluble lubricant on cornea, Lavage, Warm compresses, Antibiotics, NSAID 

  • 50% of replaced canine globes are blind

  • No topical steroids

  • No cats regain vision

Retina Anatomy

• Nerve fiber layer

• Ganglion cells

• Inner + Outer plexiform

• Inner + Outer nuclear

• Photoreceptors

  • Rods: Night vision, Motion

  • Cones: Day vision, Color

• Retinal pigment epithelium

Pathways in the Eye

• Light:

  • Light → Vitreous → Retina → Choroid/Sclera

• Afferent PLR CN II

  • Retina → Optic nerve → Chiasm → Optic tract → Pretectal nucleus → Edinger–Westphal nucleus → CN III → Ciliary ganglion → Pupil constrictor

• Efferent PLR CN III

  • Edinger–Westphal nucleus → CN III → ciliary ganglion → short ciliary nerves

• Vision

  • Retina → Optic nerve → Chiasm → Optic tract → Lateral geniculate → Optic radiation → Visual cortex

Progressive Retinal Atrophy

• Et: Breed-specific, inherited, progressive disease

• Cs: Tapetal hyperreflection, Pale optic disc, Vascular attenuation, Dilated pupils, slow/incomplete PLR, Night blindness (nyctalopia), total blindness

Retinal Detachment

• Et: Hypertension, Inflam, Fungi, Crypto, Cataracts, Congenital, Breed-associated, Trauma, Uveo-Dermatologic Syndrome, Lymphoma

• Sig: Akita, Samoyed, Siberian Husky, Bichon Frise, Shih Tzu

• Cs: acute blindness, pupils fixed and dilated, Veil of tissue posterior to lens

• Dt: Complete systemic exam mandatory

• Tx: Amlodipine, Enalapril, Diode laser barrier retinopexy

Retinal Dysplasia

• Et: Developmental abnormality of retinal differentiation/proliferation

• Sig: dogs

• Forms: 

  • Folds → mild

  • Geographic → moderate

  • Complete → severe, non-attachment, blindness)

• Tx: None, do not be bred

Sudden Acquired Retinal Degeneration Syndrome (SARDS)

• Et: unknown

  • mild Cushing’s or hepatic disease

• Cs: Acute blindness, “Swiss cheese retina” seen within 3 weeks, PU/PD, polyphagia, weight gain

• Dt: 

  • Labs: Elevated ALP, cholesterol, or liver enzymes

  • Fundus exam: Initially normal fundus → after 2–3 months  generalized retinal degeneration

  • ERG: differentiate from optic neuritis or cortical blindness

• Tx: none

Enrofloxacin Toxicity

• Et: Occurs at therapeutic doses

• Sig: cats

• Cs: Acute blindness

  • Irreversible

Micropapilla and Optic Nerve Hypoplasia

• Et: Congenital optic nerve abnormality, smaller optic nerve in a visual eye

• Sig: GSD, Min Poodle

• Cs: blindness

• Tx: None

Coloboma

• Et: Congenital pit or defect in optic nerve and sclera

• Sig: Collie Eye Anomaly

• Cs: non-vision-threatening

  • Must differentiate from chronic glaucoma

• Tx: Affected animals should not be bred

Papilledema

• Et: Non-inflammatory optic nerve swelling

  • Elevated CSF pressure

  • Mass lesions compressing optic nerve

• Cs: Not always vision-impairing

Papillitis or Optic Neuritis

• Et: Inflammation of optic nerve 

  • intraocular or retrobulbar

• Cs: Decreased or absent PLR, sudden vision loss, hyperemic optic disc, peripapillary hemorrhage, retinal detachment

• Dt: ERG

  • differentiates from SARDS

Optic Nerve Atrophy and Degeneration

• Et: Secondary to Inflam, Trauma, Chronic glaucoma

• Cs: Gray, flat optic nerve, vascular attenuation, glaucoma, peripapillary hyperreflectivity

Optic Nerve CNII 

• Use: vision, sensory

  • Afferent: PLR, Dazzle, Vision

• Dz: Blindness, Mydriasis, Absent PLR + Dazzle reflex + menace response

• Dt: Optic Nerve Exam, Maze Test

Oculomotor Nerve CN III

• Motor Fxn: (LR₆SO₄)³

  • Dorsal, ventral, medial rectus muscles

  • Ventral oblique muscle

  • Levator palpebrae (elevates upper eyelid)

• Parasympathetic Fxn:

  • Ciliary body muscle

  • Iris constrictor muscle

• Dz: Down and out” strabismus, Dilated pupil

Trochlear Nerve CN IV

• Motor Fxn: 

  • Superior oblique muscle

  • Rotates dorsomedially, deviates ventrally

• Dz: Strabismus (“out and up”), star gazing

  • PEM

Trigeminal Nerve CN V

• Branches: Ophthalmic, Maxillary, Mandibular

• Sensory Fxn: Cornea and eyelid sensation

• Afferent: palpebral reflex, oculocardiac reflex → bradycardia

• Dz: Masseter muscle atrophy / enophthalmos, Neurotrophic keratitis, Decreased tears, Decreased blink on touch

Abducens Nerve CN VI

• Motor Fxn: (LR₆SO₄)³

  • Lateral rectus

  • Retractor bulbi

• Dz: Medial strabismus, Reduced ocular motility, Inability to retract globe

Facial Nerve CN VII

• Motor Fxn: 

  • Muscles of facial expression

  • Orbicularis oculi

  • Efferent for palpebral reflex

• Parasympathetic Fxn: Lacrimal gland

• Dz: Facial paralysis, KCS, Lagophthalmos, Ptosis, Facial asymmetry

Vestibulocochlear Nerve CN VIII

• Sensory Fxn: Afferent for ocular position

• Dz: Abnormal globe motility, Nystagmus

  • Peripheral: horizontal or rotary, fast phase away from lesion

  • Central: vertical or variable, can be overridden