Exam 4 Flashcards
Lecture 1 Ophthalmic Examination
Squinting: Blepharospasm
Night blindness: Nyctalopia
Design an orderly examination that fulfills the minimum ophthalmic database for a companion animal with a red, cloudy eye
What happens to tear production, IOP, pupils, eye and 3rd eyelid when sedatives are administered?
Why should you decrease the intensity of bright light during exam?
Essential Equipment
-Bright focal light source
-Means of magnification
-Ophthalmoscope for fundus (direct, indirect) examination
-Tonometer
Ancillary Diagnostic Materials
-Sterile culture swabs
-Schirmer tear test strips
-Fluorescein dye test strips
-Proparacaine HCl for topical anesthesia
-Tropicamide (1%) for short duration dilation pupils
-Sterile ophthalmic irrigating solution or saline
Optional Equipment
-Slit lamp biomicroscope
-Cobalt blue filter
-Kimura platinum spatula/cytology brush
-23-25 g nasolacrimal cannula
-Dressing forceps
The basic examination
- Signalment
- List of breed-related ocular abnormalities OFA.org
- Ocular and medical history
- Previous ocular meds or treatments
-Drug-related changes can be recognized
-Reduced likelihood of repeating unsuccessful treatment - Evaluate patient’s temperament before dimming the lights
- Perform exam without sedation if possible. Sedatives = eye sink backward, third eyelid protrudes, pupil constricts, both tear production and IOP decrease.
- Decrease bright light source intensity, painful eye conditions increases sensitivity to light
- Use retroillumination technique to asses clarity of cornea and lens.
- Presence of PLR does not = vision
Minimum Ophthalmic database
- Palpebral reflex
-Menace response
-Direct and consensual pupillary light reflexes
-Dazzle reflex
-Schirmer tear test
-Fluorescein dye test
-Tonometry
Systemic examination
Distance assessment
-Mental status and posture. Blind: head down, move cautiously
-Look for signs of discomfort: squinting, tearing, prominence of 3rd eyelid.
-Ocular discharge if present, character, color.
-Size, position and mobility of eyes.
-Periocular swelling or deviation of the eye’s alignment
-Globe-orbit relationship both eyes compared from above
-Facial or generalized dermatologic disease present?
If no discharge or overt ulcer
-Neuro ophthalmic testing
-PLR: abnormalities such as iris atrophy, adhesions, lens dislocation, elevated IOP, drugs, anxiety. PLR presence does not = vision (central) vs. reflex subcortical. Speed and degree of pupillary constriction Ex: the indirect PLR OS to OD is present or positive.
-Menace response: crude test of vision . Normal response is to close the eye or blinking. Test of afferent tract, retina, optic nerve, optic chasm, optic tracts, lateral geniculate nucleus and optic radiations to visual cortex. CN VII relays information, learned response not reflex.
-Oculocephalic reflexes: Patient’s head taken through various positions and the globe’s position observed, neck flexed, neck extended, normal horizontal nystagmus. Failure indicates dysfunction of central or peripheral vestibular system.
-Dazzle reflex: is a subcortical reaction that complements the PLR and menace response. Shining a bright light to cause a quick squint the eye closed. No vision assessment. Implies functional retina/optic nerve and supports aggressive methods such as surgery to save the eye.
-Maze test: Good to assess vision in dogs, not reliable in cats. Obstacles placed in room or cotton balls dropped to assess visual tracking.
Follow order begin externally and ends with evaluation of the fundus
Red eyed & Cloudy eyed exam
Red eye
Should have tonometry performed prior dilation of the eyes
-Note eyelid discoloration, swelling, or loss of hair
-Inverted or everted margins?
-Extra eyelashes on margin?
-Meibomian glands abnormalities
-Size of eyelids, can animal fully open them?
-Assess third eyelid position
-Assess conjunctiva for increased redness secondary to inflammation or loss of color suggesting anemia
-Check for swelling, hemorrhage, follicle formation, foreign bodies, or tumors
Cloudy eye
Glaucoma and lens instability are contraindications for pupillary dilation
-Check for loss of clarity or contour
-Loss of transparency can occur with edema, white blood cell accumulation, cholesterol or mineral deposits, pigmentation, scarring, or vascularization.
-Blood vessels should be categorized by depth. Superficial arise with chronic surface disease, deep more often indicate IOP disease.
-Superficial vessels: originate in conjunctiva, can be seen crossing the limbus from ciliary vessels in the sclera. They have a short, “paint brush” appearance, encircle the cornea perimeter.
-Changes in corneal contour are most often a consequence of ulceration, pronounced edema, enzymatic destruction, etc.
-Color, depth and clarity of anterior chamber fluid can indicate shifts in position of lens, or change in thickness or iris, or IOP inflammation. INCREASE in aqueous humor PROTEIN or CELLS
-Constricted pupils are indication of inflammation
-Dilated pupils are indication of neurological abnormalities, increased IOP (glaucoma), age-related iris thinning, topical drug effects, and fear.
Clarity of lens
-Cataracts of the lens occur in dogs of any age, less common in cats
-Assessment of the fundus reflex is the simplest means of evaluating the clarity of the lens.
-Direct ophthalmoscope on 0 diopters 12-18 inches from eye and view the light reflected from fundus.
-Normal fundus: regardless of color should be uniform throughout the pupil and free of aberrations
Recommend and Defend the selection of a topical pharmacologic agent routinely used in the ophthalmic examination to dilate the pupil for fundus evaluation and anesthetize the ocular surface for tonometry
1% Tropicamide
-After 2 applications 5 minutes apart produces maximum dilation
-OA: 20 minutes
-DOA: 4-6 hours
Explain why atropine is undesirable as a mydriatic in the ophthalmic exam
Topical Atropine
-Requires 45 minutes to take effect
-Dilation lasts days
Explain the diagnostic importance of the dazzle reflex and menace response in a diseased eye
-Dazzle reflex: is a subcortical reaction that complements the PLR and menace response. Shining a bright light to cause a quick squint the eye closed. No vision assessment. Implies functional retina/optic nerve and supports aggressive methods such as surgery to save the eye.
Predict the undesirable effects of general anesthesia that complicate the ocular examination or alter ancillary test results
-Increased parasympathetic tone
-Reflexes reduced
-Things that can not be assessed accurately: reflexes, responses, vision, pupil size, globe movement and position, Schirmer test (STT) value, etc.
-Globe becomes exophthalmic and rolls ventrally, impossible examination
Describe the technique and diagnostic benefits of retroillumination
-Direct ophthalmoscope on 0 diopters 12-18 inches from eye and view the light reflected from fundus.
-Normal fundus: regardless of color should be uniform throughout the pupil and free of aberrations
-Provides accurate estimate of amount of light reaching the retina and a reasonable prediction of the expected quality of sight.
-Can also compare pupil size/symmetry
-Fundus reflex can also be used to pinpoint a cataract’s location based on the directional movement of the opacity.
-Centrally stationary opacities = located in the nucleus
-Opposite in direction of globe movement = are in posterior lens
Indirect Fundus Exam
-Image upside down and backwards
-At arms length
Predict the PLR, menace response and dazzle reflex in a patient with a facial nerve deficit and a cortically (centrally) blind animal
-No closing of the eyelid
-Centrally blind = no menace response present
Explain why a Schirmer tear test is performed prior to pupillary dilation or fluorescein dye application
-Performed before any diagnostic drops or medication are applied to the eye step 1.
-If the corneal surface is cloudy and the eye is painful, a fluorescein dye test may be performed as step 2.
-Postpone fluorescein dye test if need to examine retina to ensure clear view of fundus
-If IOP glaucoma suspected, then assess pressure as step 3
The Scheirmer test
-Use to assess tear production (normal >15mm/min)
-Notched end of the prepackaged sterile strip is placed over the lower eyelid into conjunctival sac
-Close eyes, wait 1 min
-Normal values >21 +/- 4.2SD mm/min Dogs, Cats >16.2..
Explain Physiologic basis of the fluorescein dye test and what a positive test indicates
Fluorescein dye test
-Use to determine the presence of corneal ulcer and is indicated in any red eye, painful eye with irregular corneal surfaces
-One or two drops of sterile eyewash are applied to the strip
-Dye is applied to the dorsal sclera of the eye. Avoid touching the eye as it can result in a false result area
-Excess stain is irrigated from the eye with sterile saline
-Cobalt blue light is used to detect retention of dye, corneal ulcer retains dye.
Normal hydrophobic epithelium would repel dye = negative result
Positive test, corneal ulcer = hydrophilic stroma retains the dye
-Nasolacrimal duct patency can be tested with dye
-Jones test: let dye come out at nasal duct exit 1-5 minutes
. If not out, check inside the mouth in pharynx
-Flush if blocked, optic anesthetic
Identify a diagnostic test that evaluates tear quality rather than tear quantity and how that test is performed
Tear Film Stability by Measuring Tear Film Break-up Time
-After application of dye, manually blink to distribute dye
-Blue light source 15-20 seconds normal, less abnormal
Tonometry, Cytology
-Measurement of IOP
-Red painful eye
-Screening for glaucoma
-Cocker Spaniel, Basset Hound
-Uveitis and glaucoma
-Normal range 8-25 mmHg
-No more than 20% difference in eyes
-Anesthetized corneal surface
Cytology
-Ophthalmic bacterial culture for rapidly progressing corneal ulcers
-Poorly healing ulcers
-Anesthetic, cytology brush conjunctival surface
Lecture 2
Eyelid disease is common in dogs,
not frequent in cats
Skull conformation, orbital contents, characteristics of the skin, considered desirable facial features in certain breeds, no singular genetic component in eyelid disease
Consequences of Uncorrected eyelid agenesis in the cat
Eyelid Agenesis
-Failure of development of a portion of the eyelid
-Almost exclusively seen in the cat
-Persian breed affected most
Superior temporal eyelid typically affected
-Minor defects may be asymptomatic
-Severe agenesis results in corneal and conjunctival exposure and contact with facial hair, increased lacrimation, secondary corneal disease
Tx
-Cryosurgery: eliminates hairs
-Entropion procedure to evert the adjacent cilia.
-Larger defects a pedicle graft from the lower eyelid or adjacent facial skin is indicated.
Common post-operative complication with grafts is misdirected hairs
-Lip to lid transposition provides more natural mucocutaneous margin, hairless border created
Clinical signs that necessitate treatment of distichiasis
-Abnormality where the eye lash originates from the meibomian gland
-Meibomian glands: secret lipids that form the superficial layer of tear film to protect evaporation of the aqueous phase.
C/S
-Tearing
-Squinting
-Corneal disease: scarring, pigmentation, ulceration
Compare Entropion pathology and surgical correction in dog and cat
Pathology
-Inversion or “in-rolling” of the eyelid margin
-Relatively common in the dog
-Developmental, breed-related disorder commonly
-Cicatricial entropion: chronic inflammatory disease
-Spastic entropion: painful ocular disease FELINE mostly
-Surgery should not be delayed if cornea has been damaged
-Dx: schirmer tear test, fluorescein dye test. 0.5% Proparacaine to eliminate corneal sensation so that anatomical and spastic components can be differentiated. Failure to make distinction can lead to surgical overcorrection
Eyelid tacking
-Temporary correction of anatomical entropion in puppies
-Can be used in older dogs for relief of spastic entropion
-The older the animal is when tacking is performed, the less likely it would resolve the entropion without additional surgery
-Procedure: 2-4 vertical mattress sutures in the affected lid 5-0 nylon 2mm from margin do not place suture through the margin
Tissue excision
-Hotz-Celsus Procedure
-Everting the lid margin by removing the elliptical segment of eyelid skin equal to the degree of inversion.
-Certain details increase surgical success
-Incision 2mm from margin
-#15 blade
-Undercorrection with the need for a second operation is preferable to overcorrection that results in cicatricial entropion
-Rottwilers and Retrievers with upper and lower entropion combined with lateral cantonal laxity required modified technique
-SharPei and Chows challenging due to facial skin folds
-Some cats ha minimal lid laxity, classical Hotz-Celsus procedure usually is effective
Eyelid spasms may persists after surgery, chronic herpetic keratoconjunctivitis
-Injectable collagen filler have been used in recent years to correct mild entropion in young and adult dogs and cats
Ectropion
-Eversion of the eyelid
-Less common to required surgical correction
-Secondary conjunctivitis can be controlled medically with lubrication ointment and intermittent steroids
-V-resection procedure for correction near the lateral canthus. Excise the portion of the eyelid that overlaps the lateral side of the wound.
Macroblepharon
-Breed related exophthalmos
-Risk factor for corneal ulceration in brachycephalic breeds
Most common eyelid neoplasm in dog and cat, describe appropriate course of action
Dogs
-Most are benign, slow-growing, non-irritating: do not need to be excised unless they threaten to compromise the lacrimal punctum
-Most common is the meibomian adenoma
-Mast cell tumors worst prognosis
Cats
-Almost always malignant
-Should be removed at the earliest possible opportunity
-Most common is squamous cell carcinoma
-Mast cell tumors usually benign
Tx
-Complete surgical excision recommended in most cases
-En bloc surgical resection
-Preserve as much of the eyelid margin as possible
-Four-sided technique instead of V or wedge resection
-S full thickness, parallel cuts perpendicular to margin, 1-2mm on either side of the mass, and extend as needed.
-Connect the distal ends with a V-shaped incision adding the “roof” to the sides of the “house”
-Close using two layers
-Submit tissue in 10% formalin for histopath
Cryosurgery
-May be preferred if mass impinges on a lacrimal punctum
-Nitrous oxide probe temp -196C.
-Chalazion forceps to impede blood flow to the site (Chalazia is a non neoplastic enlargement of the meibomian gland caused by blockage of its duct)
-Double-freeze technique and slow thaw
Cryosurgery specially useful for older debilitated patients
-Can be performed with sedation and local anesthesia
Briefly detail surgical repair of full-thickness eyelid laceration involving the middle section of the inferior eyelid, tissue layers and reconstruction plan
-Most lacerations occur perpendicular to the eyelid margin
-Rich vasculature of the eyelid promotes rapid healing
Always assess the entire eye for signs of injury
Avoid excision of flaps that involve the lid margin
-Close all traumatic lacerations in 2 layers
-Start in the apex of the wound
-Oppose the conjunctival edges 6-0 absorbable suture, simple continuous
-Bury the knots to avoid damage to adjacent cornea
-Reappose margin PERFECTLY with a single 6-0 absorbable suture in a figure-of-eight pattern to prevent cosmetic and malfunction defect
-Simple interrupted skin sutures ~2-3 mm apart
-Systemic and topical antibiotic and NSAIDs for 7 days
-E-collar
Anatomical and functional eyelid abnormalities that threaten corneal health in brachycephalic canine breeds
Components of the eyelid
-Skin
-Skeletal and smooth muscle
-Fibrous connective tissue
-Mucous membrane
-Cilia
-Modified sebaceous glands
-Superficial layer
-Deep layer: fibrous tarsus and inner conjunctiva
-Dogs have eyelashes only on the upper eyelid (modification of lid hair often passes for lashes)
-Cats lack eyelashes completely
-Highly vascularized, resistance to microbial infection
-Meibomian glands: 30-40 perpendicular to each eyelid margin opening into marginal furrow
-Upper eyelid more mobile than lower
-Orbicularis oculi muscle major m. responsible for closure. Innervated by the palpebral nerve.
Macroblepharon
-Breed related exolphthalmos
-Corneal ulcerations in brachycephalic
-Exaggerated palpebral fissures
-Prominent eyes combined with excessively large palpebral fissures
-Corneal exposure
-Superficial keratitis (corneal inflammation)
-Recurrent ulcerations
-Crocker spaniels, Bloodhound, St Bernard
-Tx: Excise the lid margin and meibomian glands at the lateral canthus and close the defect in 2 layers as described for lid shortening of entropion. Can be done medially but careful not to damage nasolacrimal puncta and canaliculi in this region. Medial closure has the advantage of resolving concurrent medial entropion medial cantal hairs, and contact by hairs of the facial folds
Blespharitis C/S, treatment plan for Staphylococcal hypersensitivity
-Acute eyelid swelling in a young dog is characteristic of the ocular manifestation of juvenile cellulitis/pyoderma (“puppy strangle”)
-Adult: slowly progressive swelling, peri ocular alopecia, excoriation, meibomian gland distention and conjunctivitis.
Staphylococcus aureus
-Hard to culture
-Bacterial hypersensitivity requires systemic antibiotic and corticosteroid for several weeks
-Relapses are common is therapy discontinued prematurely
-Ddx: dermatophytosis, demodecosis, immune-mediated mucocutaneous disorders such as pemphigus, atopy, food allergy, neoplasia, mycosis (cutaneous lymphoma) and allergic reactions to insect stings and medications
Chalazion
Focal eyelid inflammation is termed HORDEOLUM
-Acute abscess of one or more meibomian glands
-Tx: warm compresses, topical and oral antibiotics, short course of corticosteroids
-Chronic lipid granuloma from blockage of gland
-Tx: incision and curettage of inspissated material through the conjunctival surface
Prolapsed third eyelid gland preferred surgical treatment and technique
Nicitans gland “cherry eye” Prolapse
-Weakness in the fibrous connective tissue anchoring at the gland’s base
Excision of the gland reduces tear production by 30-40%
-Not advisable excision of the gland
Preferred treatment
-Surgical return gland to its normal position
-Simplest technique is the POCKET TECHNIQUE
-Two curvilinear incisions are made through conjunctiva on the posterior surface of the third eyelid using #15 blade
-2-3mm from the free margin and the second 6-7mm toward the base of the third eyelid
-The ends of the two incisions should NOT meet in order to ensure opening/drainage
-6-0 suture to bring the two edges together simple continuous pattern
-Antibiotics for 2 weeks
-No steroids during early healing period
-Activity is restricted
Third eyelid protrusion common causes and Ddx list
Common causes of Protrusion
-Ocular pain
-Reduction in orbital tissue mass due to dehydration or atrophy
-Reduced globe size
-Reduced space-occupying orbital disease
-Facial myositis
-Horner’s syndrome
-Tetanus
-Dysautonomia
Inverted eyelid cartilage identification and post operative complication following repair
Eversion of the Third eyelid Cartilage
-Outward curling of the third eyelid cartilage occurs most often in a young, large and giant breed dogs
-Burmese most commonly affected cat
-Can be misinterpreted as gland prolapse
-Tearing and conjunctivitis present
-Tx: surgical excision of the deformed section of cartilage
-Incision in conjunctiva and dissection
-Round up the edges of cartilage to avoid irritation
-Post operative antibiotic ointment q 8 hr for 5-10 days
Recurrence of defect is unlikely, but prolapse of the nicitans gland may follow correction
-Thermal cautery may be used for mild defects
Pathology and removal of third eyelid justification
Cilia disorders
Distichia
-Hairs that arise from the meibomian gland orifices due to misplaced follicles within the adjacent glands
Their presence does not warrant their removal
-Treatment if tearing, conjunctival irritation or corneal ulceration
-Cryoepilation is the most practical treatment
-Chalazion forceps, nitrous oxide cryoprobe, freeze, thaw, then repeat freeze.
-Topical antibiotic q 8hr for 7-10 days
Ectopic cilia
-Distichia that has erupted through the palpebral conjunctiva of the eyelid
-Discomfort, corneal ulcerations often
-Young classically affected
-Squinting and tearing
-En bloc resection is curative, sparing the margin
Trichiasis
-Normal eyelashes with growth toward the eye
-Contact with ocular surfaces, irritation, ulceration.
-Congenital problem in small breed dogs, brachycephalic
-Cryoepilation is commonly used to destroy the offending follicles
-Surgical eversion of the lid margin can redirect the hairs
-Injectable collagen filler can also be used to restore normal cilia position
Lecture 2 & 4
Diseases of the Posterior Segment (Fundus)
Describe the Salient Features of the normal fundus
Fundus
-Composite picture formed by the optic nerve head (optic disc, optic papilla), sensory retina, retinal pigmented epithelium, choroid, tapetum and sclera, a picture influenced by the animal’s species, breed, age, and coat color.
Sclera
-White to pale yellow
-Visibility depends on the degree of pigmentation in the overlying chorioid and retinal pigmented epithelium as well as the degree of tapetal development
Choroid
-AKA posterior uvea
-Lies adjacent to the sclera
-Normal choroid vessels should be small and uniform size
-Vessels radiate from the optic papilla in spoke-like fashion
-Choroidal vasculature is rarely a complete barrier to visualization of the underlying sclera
-Degree of pigmentation can normally vary. It can be so pigmented that its vasculature is barely discernible or it may be totally devoid of pigment
-Epithelium pigmentation is determined by the same factors that govern coat pigmentation
-GSD masked, while Husky very visible
-In heavily pigmented breeds, melanin lies interspersed between the large vessels of the choroid
Tapetum
-Layer of reflective cells in the dorsal half of the fundus
-Between the retinal pigmented epithelium (RPE) and the choroid
-Reflectivity is dependent on the cell density, greater in the cat than the dog
-Variations that are important are in extent (size) and degree of development
-The overlying RPE is normally devoid of pigment so that the tapetum can be visualized
-Normally the RPE gradually diminishes as it approaches the tapetum
-The tapetum in turn thickens, results in a gradual change in color at its periphery
Retina
-Consists of 10 layers
-Clinical purpose 2 layers
-Outermost RPE and the neurosensory retina
-Gross separation between the two is known as retinal detachment
-RPE is monolayer lies next to the choroid on the ventral area
-Normal variation in RPE determines if the choroid can be seen
-Adjacent and attached to RPE is the semitransparent neurosensory retina, whose contribution to the normal fundus is the most subtle of all layers
Unlike the choroid and RPE, there are no normal variations to the sensory retina per se, variations of the vessels do occur
-Normally in dog 3-5 major retinal venues that radiate superiorly, nasally, and temporally from optic disc, producing venous circle
-The cat has 3 paired retinal vessels never crossing the surface of the optic disc
Optic disc
-Cats: papilla varies little, being unmyelinated and characteristically circular
-Darker in color than canine optic disc
-Canine: marked variations in myelination and assume many shapes. Located within the tapetal fundus as well but may appear in the non-tapetal fundus of toy breeds
List 5 questions one should answer during examination of the fundus
- Can I get all parts of the fundus in focus simultaneously?
- What is the general tapetal “sheen” over the whole fundus?
- Are there any focal areas of unusual coloration within the fundus?
- How do the retinal vessels appear?
- How does the optic disc appear?
Explain the alterations in fundus anatomy responsible for the following variations or pathology
- Visualization of choroidal vessels in the tapetal and non-tapetal fundus
-Choroid thinning or thickening response to disease
-Collie eye anomaly: thinning
-Uvea is vascular tunic of the eye: choroidal thickening accompanies inflammation
-Tapetal fundus discoloration and decreased reflectivity = choroid disease
-Subretinal exudates = inflammation, possible detachment
- Increased tapetal reflectivity
-Suggest thinning/degeneration of the overlying retina
-Decreased light absorption that accompanies retinal detachment/degeneration allows more light to be reflected back to the examiner from the tapetal surface
- Diminished tapetal Reflectivity in active chorioretinitis
-Occurs in active inflammation
-Edema, exudation, retinal detachment
- Retinal detachment
-Sensory retina pathology: thinning or thickening
-Retinal thinning: increased fundus reflectivity, fallow inflammatory, toxic and ischemic disease processes.
-Retinal thickening: layers are folded, occurs in developmental disorders, or it may swell due to an influx of inflammatory cells, tumor cells, or fluid.
-Sensory retina may respond to pathology by detachment form RPE. Occurs secondary to almost any ocular disease
. Hypo-reflectivity in the area of detachment along with forward shift in the location of the retinal vessels
-RPE changes are generally limited to affecting pigmentation
-Increase or decrease in pigmentation are seen in hereditary retinal degenerations and secondary to inflammatory disease process.
-Decreases in RPE pigmentation are readily seen in the non-tapetal fundus
-Retinal blood vessels respond by change in size
-Attenuated vessels Ddx: anemia, hypovolemia, retinal degeneration
-Vascular enlargement less common Ddx: IOP disease, inflammation, hyper viscosity.
-Retinal hemorrhage Ddx: systemic hypertension, anemia (pancytopenia) and clotting disorders
-Hypoxic states: pink, lipemia animals or deeper red vessels
- Optic disc
-Responds by enlargement or decrease in size
-Congenital or acquired changes
-Numerous causes
-Congenital hypoplesia or acquired optic atrophy following inflammatory disease, trauma or retinal degeneration will reduce the size of the papilla.
-Enlarged papilla, neoplasia, inflammation or edema
Summarize and recognize the clinical features (including breed disposition, congenital or adult onset, type of inheritance, presenting history, and likelihood of progression) of the following inherited disorders
- Collie eye anomaly
-Posterior segment abnormalities
-Collie breed 80-85% affected
-Autosomal Recessive
-Shelter, Border Collie, Australian shepherd also have a congenital ocular anomaly similar to that of the Collie, but much low prevalence.
-Diagnosed by 8 weeks of age
-Bilateral ophthalmoscopic lesions, progressive and increasing in severity.
C/S
-Choroidal hypoplasia (pale area temporal to the optic disc)
-Optic nerve and Scleral Colobomas
-Retinal detachment/hemorrhage
Choroidal hypoplasia is the most common lesion encountered
-DNA test available
- Retinal dysplasia
-Embryologic developmental abnormality
-Retinal layers are variably disorganized
-The more severe dysplasia manifests as detachment or non-attachment.
-Inherited from uterine infection (canine herpesvirus, feline panleukopenia)
-Dx by 8 weeks of age
-Many breed affected
Uncommon in the cat
English Springer Spaniel: autosomal recessive trait
-Bedlington, American Cocker Spaniel, etc.
C/S
-Bilateral non-progressive, multifocal lesions appear as round or linear areas of discoloration in the tapetal fundus.
-Lesions appear as hyper-reflective as the tapetum matures
-Centers are pigmented
Functional vision is spared
-Blindness results when retinal tears or detachment accompany severe retinal disorganization
-Cataracts in the Springer possible
-Labradors, multifocal folds within the tapetal fundus.
-Retinal detachment, corneal opacification, cataracts, vitreous degeneration, glaucoma (COL9A3 gene)
-Short limb dwarfism
Samoyed: skeletal dysplasia also present
- Optic nerve hypoplasia
- Generalized PRA (progressive retinal atrophy)
-Inherited retinal degeneration in a variety of breeds 86 breeds reported
C/S
-Initial night blindness (nyctalopia) that progresses to total blindness
-Older animals more common
-Blindness < 1yo: Collie, Irish Otter, Cardigan Welsh corgi
-Slower progression, blindness > 1yo: Gordon setter, Dachshund, Akita, Miniature schnauzer, Norwegian elkhound, Tibetan terrier.
-Late onset, slow progression, Onset >2yo, Blindness 4+ yo: everything else, Golden retriever, Poodle, etc.
Cats
-Abyssinian: early onset, inherited autosomal dominant trait, onset 8-12 weeks old, blindness <1 yo. Also, can be late onset 4-6 yo blindness
-Persian and Siamese also affected.
Identify causes on non-inheritable retinal atrophy in the dog and cat
-Enrofloxacin in cats 5-20 mg/kg dose
-Defect in transport protein causes accumulation of photo reactive fluroquinolones in the retina, exposure to UVA light = destructive free radicals and rapid retinal degeneration.
-Risk: geriatric, hepatic or renal disease cats.
C/S
-Sudden loss of vision
-Dilated pupils
-Effect within a few days
Describe the signalment, ocular signs, treatment and prognosis in a cat with hypertensive retinopathy
-Systemic hypertension in cats
-Systolic BP >180 mmHg
>10 years old
-Sudden or progressive blindness
-Abnormal pupillary light reflex
-Bilateral retinal detachment
-Intra ocular hemorrhage
Dogs
-Hypertensive
-Multifocal retinal hemorrhages
Treatment
-Amlodipine besylate daily
-Can result in retinal re-attachment and return to vision in the cat
Prognosis
-The more chronic detachment the less likely return of vision
-Risk of secondary glaucoma due to hemorrhage
Discuss differential diagnoses for acute vision loss in a middle-aged mixed breed dog with clear eyes, dilated pupils, and poor or absent pupillary reflex
SARD (Sudden acquired retinal degeneration)
-Second most common, PRA is most common
-Not reported in cats
-Signalment: middle to older age. Females over represented.
Dachshunds and Schnauzer most represented breeds
C/S
-Acute vision loss without signs of inflammation or discomfort
-Unexplained mechanism
-Loss of photoreceptor outer segments and abnormalities in the nuclear layer
-No obvious fundic abnormalities initially
-First observed 4-8 weeks after onset of blindness, subtle variation in tapetal reflectivity and retinal vessel segmentation
-PU/PD, polyphagia, weight gain, panting consistent with Hyperadrenocorticism
-Acute vision loss, abnormal pupillary reflex, optic neuritis
-Normal PLR with cortical blindness
Electroretinography for definitive dx
List 3 causes of Chorioretinitis in the dog and cat
Suggestive of systemic disease
-Infectious and/or neoplastic causes
-Prognosis for vision is guarded
- Viral: Distemper, Cat: FIP, FLV, FIV.
- Bacterial: Brucellosis, Borreliosis, Cat: Bartonellosis, Tuberculosis
- Fungal: Cat and dog: Blastomycosis, Cryptococcosis, Histoplasmosis, Coccidioidomycosis, Aspergillosis
- Parasitic: Toxocara canis migrating larvae, Cat: Toxoplasma
- Neoplastic: Lymphosarcoma, multiple myeloma, metastatic neoplasia
-Optic neuritis: appears swollen and indistinct
-Inflammation of the posterior segment
Unless vision is affected or other ocular tissue is concurrently inflamed the eye may appear unremarkable until ophthalmoscopic exam
Describe the funduscopic features that differentiate active from inactive chorioretinitis
Active Chorioretinitis
-Tapetal fundus hazy and gray
-Edema, exudates may obscure tapetal reflection
-Non tapetum area, edema and exudates appear gray or white obscuring RPE and choroid
-Retinal vessels may appear hazy due to perivascular cellular cuffing
-Hemorrhage may be present at various tissue levels
-Retinal detachment may occur secondary to inflammation and or choroidal exudates
Identify 2 congenital disorders of the fundus that could limit vision in a puppy
- Canine Multifocal Retinopathy
-Mastiff, Bullmastiffs, others
-Early onset disease
3-6 months of age onset
-C/S: acute, multifocal, serous retinal and RPE detachment.
-Circular and gray-tan lesion. May regress, remain stationary or progress to degeneration - Acquired retinopathies
-Chorioretinitis or posterior uveitis: Canine distemper virus infection
Describe the near-ophthalmic exam findings characteristic of optic neuritis, its treatment and prognosis for vision
Optic neuritis
-Swollen, indistinct optic disc, poorly defined margins, adjacent retinal hemorrhage and detachment.
-If only the retrobulbar portion is affected, there may not be observable changes in the optic disc itself
-Vision loss is typically acute
-Affected pupils are widely dilated and PLR are absent or often delayed
-Granulomatous Meningoencephalitis association
-Ocular trauma, neoplasia
-Most cases are idiopathic or immune-mediated
-Less common in the cat
Treatment
-In the absence of an etiologic diagnosis: immunosuppressive corticoids for 14 days , tapered gradually until maintenance dose is determined
-Alternatively immunosuppressive agents (azathioprine, cyclosporine) may be substituted
-Prognosis for vision is poor, optic nerve atrophy sequela common
Lecture 5
Disorders of the Lacrimal system
Identify causes of inadequate tear production
Iatrogenic causes
-Etodolac, galliprant, various sulfa drugs, atropine
-Surgical excision of nictitans gland “cherry eye” treatment
Congenital
-Immune mediated disease
Infectious agents
Toxic agents
Neurologic reasons
Inflammatory
Functional Anatomy
-3 layers
-Mucin layer produced by conjunctival goblet cells
-Tear film nourishes cornea and conjunctiva, lysosomes and immunoglobulins, lubrication
-Blinking directs tears to medial canthus, collected in lacrimal lake, capillary action and passive pump mechanism leads to lacrimal puncta
-Drain into a short caniculus, then lacrimal sac, then the nasolacrimal duct.
-Epiphora: tear over production/flow
- Deficiency in tear production
- Tear excess
- Abnormalities within the tear drainage system
Lecture 6 & 7
The cornea & Sclera
Lecture 8
Disease of the anterior uvea
Lecture 9
- describe the anatomical regions of the lens.
- Anterior capsule
- Lens epithelium
- Anterior cortex
- Nucleus
- Posterior cortex
- Posterios capsule
Lecture 10
Diseases of the Orbit
- outline a diagnostic and medical regimen for treatment of acute glaucoma in a dog, including the
mechanisms of drug action and prognosis for successful medical control of intraocular pressure (IOP).
Dx
-Tonometry
-Ophthalmology of retina, optic disc
-Gonioscopy to evaluate gross appearance of iridocorneal angle. Helps differentiate between primary and secondary glaucoma
Primary glaucoma
-No concurrent ocular disease or injury
-Breed-related, inherited
-Bilateral but one eye more affected than the other.
-Second eye affected within 8-12 mts if no treatment
-Identification of the abnormal angle substantiates need for prophylactic therapy of the second eye
Gonioscopic - Iridocorneal angle
- Open angle glaucoma: normal angle; Beagle
- Narrow angle: decreased width of angle; Crocker spaniel
- Pectinate ligament dysplasia (goniodysgenesis): abnormal pectinate formation, characterized by broad sheets of tissue with few flow holes; Basset hound
Secondary Glaucoma
-IOP sequela to other ocular disease or injury
-Causes: lens luxation, trauma, inflammation, neoplasia
Pupillary blockage by lens responsible for IOP increase
-Anterior uveitis produces adhesions of iris to cornea, obstructing flow through the iridocorneal angle
-Tumors invade and cause secondary inflammation, adhesions
Therapy
- Reverse IOP increase
a. Medical: stabilize within 24-48 hours
b. Surgical
c. Combination
Drugs MOA
1. Promotes aqueous outflow (usually with miosis)
2. Dehydrate the vitreous
3. Decrease aqueous production
-Topical less potent but less side effects than systemic
-Dogs tolerate better than cats
-Remission of primary glaucoma, later additional alternate drugs
-Always aim for synergistic action
-Human drugs do not predictably work on dogs or cats
Neuroprotective agents
-Systemic calcium channel blockers (Amlodipine besylate)
-Systemic corticosteroids to combat oxygen free radicals
Prophylactic treatment of second eye is imperative
-Topical Carbonic anhydrase inhibitor (Dorzolamide or Brinzolamide) for prophylactic second eye care
-Topical Demecarium bromide solution combined with SID steroid
Refer immediately to ophthalmologist, do not wait
Primary Narrow Angle Glaucoma, Medical Tx
-2% Dorzolamide topically
-Latanoprost topically
-If no improvement: repeat Latanoprost add mannitol, recheck
-If no improvement: refer
If improved after 2% dorzolamide
-Re-evaluate in 1 hour
-Dorzolamide q8 hrs
-Latanoprost q 12 hrs
-Recheck IOP q 4-6 hors
-If stable: continue both, treat second eye prophylactically, refer for surgical evaluation
