Week 6 - Optho Flashcards
What are the afferent and efferent parts of the PLR?
A: CNII
E: CNIII
What are the afferent and efferent parts of the menace response?
-remember - NOT a reflex
-A: CNII
-E: CNVII and obicularis oculi
What are the afferent and efferent parts of the Palpebral reflex?
A: CNV
E: CNVII and obicularis oculi
What is the Pupillary Light Reflex?
A reflex to a bright light stimulus
- Direct PLR – stimulated eye constricts
- Consensual PLR – non-stimulated eye constricts
–Less strong than the direct PLR
–Domestic animals only (absent in birds)
What are the tips for PLR?
-perform under bring and dim conditions
-false negatives
–high sympathetic tone - STRESS
–iris atrophy - difficult for sphincter to constrict
–posterior synechiae (wont see PLR bc of mechanical reasons)
-will be present at birth
-intact WITH BLINDNESS
-consensual PLR - useful for opaque ocular media
What is the Menace Response?
- A learned response to a threatening gesture - absent at birth
–Absent in young animals (<3 months in cats & dogs)
–learned around 3-4 months - CNs II, VII, cortex & cerebellum
-CRUDE test of vision
-could better test vision with maze tests, cones, anything on a string for a cat
What are tips for a menace response?
-check each eye separately
-cover opposite eye while testing
-avoid touching vibrissae or creating air currents
-perform PALPEBRAL reflex immediately prior - increases patient’s awareness
-inconsistent or absent in patients that are:
–stoic
–depressed
–stressed
Palpebral & Corneal Reflexes are reflexes following touch of:
- Periocular skin (palpebral)
–Stimulate both medial & lateral canthi
–Perform prior to the menace response - Cornea (corneal)b- if you suspect trigeminal nerve paralysis
- CNs V & VII
Neuro-opthalmic functions are (3)
- Eyelid closure
*Orbicularis oculi muscle
* CN VII - Eyelid opening
* Levator palpebrae superioris
* CN III - Sensory innervation to cornea & eyelids
* CN V
- PLR regulates light entry
- Eyelid opening and closure
- Eye motility
- Protection of the globe
- Sympathetic innervation:
–Regulates amount light entering eye
–Position of the globe
–Position upper eyelid (Müller’s muscle)
General signs of neuro-opthalmic dz
- Abnormal pupil size or reactivity
- Abnormal globe position
- Abnormal eyelid position (ex. ptosis - eyelid drooping)
*Inability to close eyelids → Corneal disease - Third eyelid protrusion
What is Horner’s Syndrome?
- Compromise of sympathetic innervation to the eye and its related structures
-route involves 3 neurons
1st neuron - starts in midbrain, goes to spinal cord T1-T3
SYNAPSE
2nd neuron - goes back thru mediastinum/chest to tympanic bullae
SYNAPSE in cranial cervical ganglia with trigeminal nerve
3rd neuron - goes to eye
With Horner’s Syndrome, what anatomical structures does it innervate? (what are the Postganglionic sympathetics?)
What are the normal results/sympathetic function of the anatomical structures, in reference to Horner’s syndrome?
- Smooth muscle periorbita
- Müller’s muscles of eyelids
- Iris dilator - stimulates
- Iris sphincter - inhibits
- Slight protrusion of globe
- Retraction of third eyelid
- Opening palpebral fissure
- Pupil dilation
CS of Horner’s Syndrome
- Miosis
- Ptosis
- Enophthalmos
- Protruded third eyelid (result of enopthalmos)
not painful, but could be suspected by owners
What CAUSES Horner’s Syndrome?
- Idiopathic- the #1 “cause”
- Head, neck, or chest trauma
- Head, neck or chest neoplasia
- Chronic otitis media
- Ear cleaning
- Retrobulbar disease
- Metabolic disease
–Diabetes mellitus
–Hypothyroidism
How do you DIAGNOSE Horner’s Syndrome?
- Clinical signs
- Complete physical exam
–Otic exam - Pharmacologic testing
–Allows localization pre- or post-ganglionic lesion
–Direct sympathomimetic (1% phenylephrine) - Radiography
- Advanced imaging
- Blood work
What is the idea of denervation hypersensitivity in terms of pharmacological testing for Horner’s Syndome?
s-after denervation, there is increased sensitivity of muscle to neurotransmitters – so more receptors are made!
Pharmacologic testing:
* Direct-acting sympathomimetic
–1% Phenylephrine (acts like eps)
- Post-ganglionic lesion
–Dilate pupil w/in 20 min
–dilates quickly bc hypersensitive to the syndrome - Pre-ganglionic lesion
–Dilation takes significantly longer
How do you TREAT Horner’s Syndrome?
-address underlying cause if present
-topical phenyl epinephrine can relieve signs but is short acting
What is the PROGNOSIS Horner’s Syndrome?
-depends on underlying cause
-most postganglionic cases resolve in <6 months
What is Facial Nerve Paralysis?
- Orbicularis oculi innervated by CN VII
- Loss of function results in the inability to close the eyelids (obicularis oculi CLOSES the eyelid)
- Lacrimal nerve runs with CN VII – concurrent decrease in tear production
CS of Facial Nerve Paralysis
- Widened palpebral fissure due to drooping lower lid
- Increase visible sclera, especially ventrolaterally
- Drooping of ear and lip
- Nose “pulled” toward normal side
- Loss of palpebral and corneal reflexes
- Inability to blink results in secondary exposure keratitis
- Ulceration and infection are common
What CAUSES Facial Nerve Paralysis?
- Idiopathic (Cockers, Boxers)
- Iatrogenic (surgery to head or neck)
- Otitis media/interna
- Neuromuscular disease
- Intracranial disease (neoplasia)
- Hypothyroidism
- Trauma to head or neck (HBC, etc.)
How do you DIAGNOSE Facial Nerve Paralysis?
- Clinical signs
- Complete physical exam
- Otic exam
- Neurologic exam
- Radiography
- Advanced imaging
- Bloodwork
How do you TREAT Facial Nerve Paralysis? ** watch mediasite
- Address underlying cause if present
- Exposure keratitis may require:
–Temporary tarsorrhaphy (EXAM)
–Frequent lubrication
–Corneal ulcer management
How do you TREAT Facial Nerve Paralysis? ** watch mediasite
- Address underlying cause if present
- Exposure keratitis may require:
–Temporary tarsorrhaphy (EXAM)
–Frequent lubrication
–Corneal ulcer management
What is the Prognosis for Facial Nerve Paralysis?
- Depends on underlying cause
- Guarded with idiopathic cases (<33% recover)
–Relapses may occur
What is Ophthalmoplegia? WATCH MEDIASITE
- Compromise of CN III innervation
What are the 6 ocular/periocular muscles are innervated by CNIII?
- Iris sphincter
- Dorsal rectus
- Medial rectus
- Ventral rectus
- Ventral oblique
- Levator palpebrae superioris
(Dorsal, medial, vental rectus / Levator palpebrae superioris / Iris sphincter / Ventral oblique)
CS for Internal & external ophthalmoplegia
- Visual
- Mydriasis (internal ophthalmoplegia)
- Ventrolateral strabismus (external ophthalmoplegia)
- Ptosis (external ophthalmoplegia)
If a dogs R eye is affected with ophthalmoplegia, what would your neuro-optho exam look like?
- Mydriasis OD
- Negative direct PLR OD, positive consensual OD>OS
*positive direct OS, negative consensual OS>OD - Ventrolateral strabismus, ptosis OD
- Positive dazzle, menace, and palpebral OU
What is Internal ophthalmoplegia? remember – you either have external+internal OR just internal ophthalmoplegia
- CN III parasympathetic fibers located superficially and medially relative to CN III motor fibers → mydriasis with no ptosis or strabismus
Neuro-ophthalmic exam
* Mydriasis OS
* Negative direct PLR OS, positive consensual OS>OD
* Positive direct OD, negative consensual OD>OS
* Positive dazzle, menace, and palpebral OU
NO issues strabismus or ptosis
What CAUSES ophthalmoplegia?
- Space occupying lesions in the cavernous sinus or orbital fissure
What CAUSES ophthalmoplegia?
- Space occupying lesions in the cavernous sinus or orbital fissure
How do you DIAGNOSE ophthalmoplegia? and TREAT ophthalmoplegia?
- Diagnosis
–Advanced imaging, usually MRI - Treatment & prognosis
–Variable dependent on cause
What are 2 avascular ocular tissues?
-cornea (epithelium/stroma)
-lens
What are some vascular ocular tissues?
- Adnexa Conjunctiva
- Sclera
- Uvea (iris, CB, choroid)
-anterior uvea
-posterior uvea - Retina
- Eyelids
- Optic nerve
There are two way of thinking about the eye, in terms of drug delivery. What are they?
- Avascular/Vascular
- Front/Back
When there is __________ in adjacent structures, the aqueous humor and vitreous humor can benefit from SYSTEMIC DRUGS because ____________
-inflammation
-b/c they have access to the leaky Blood Vessels from the inflamed adjacent structures
System drugs will reach avascular/vascular structures?
VASCULAR
Which structures are part of the back half of the eye?
-orbit
-posterior uvea
-retina
-optic nerve
-vitreous
Systemic/Topical drugs will reach the back half of the eye?
SYSTEMIC, topical drugs will never reach the back half of the eye
Which structures are part of the front half of the eye?
-adnexa
-conjunctiva
-corneal stroma
-aqueous
-anterior uvea
Systemic/Topical drugs will reach the front half of the eye?
SOME topical
some topical WILL penetrate the epithelium, stroma, and DM/endothelium. other topicals WILL NOT penetrate the epithelium.
What are some examples of Parasympatholytics? Will they penetrate or bounce from the surface of the eye?
PENETRATE
-Atropine ophthalmic solution/ointment
-Tropicamide ophthalmic solution
Advantages: Mydriasis for diagnostic (tropicamide) or therapeutic (atropine) purposes, cycloplegia, blood-aqueous barrier stabilization
Limitations: Increases IOP, decreases tear production, hypersalivation (cats)
What are some Glaucoma drugs? Can they penetrate the surface of the eye?
ALL PENETRATE
-Latanoprost
-Dorzolamide
-Timolol
a. Prostaglandin analogues (Latanoprost, travoprost or bimatoprost ophthalmic solutions)
Advantages: Potent IOP reducer, increase uveascleral aq. humor outflow
Limitations: Contraindicated with anterior lens luxation, ineffective in cats, mildly inflammatory, causes intense miosis
b. Carbonic anhydrase inhibitors (Dorzolamide or brinzolamide ophthalmic solutions) - DECREASES aq humor production
Advantages: Useful in cases with concurrent uveitis or anterior lens luxation, effective in cats
Limitations: Less potent than prostaglandin analogues
c. Sympatholytic agents (Timolol or betaxolol ophthalmic solution)
Advantages: Decreases IOP in cats, GLAUCOMA PROPHYLAXIS in dogs, DECREASES aq. humor production
Limitations: Decreases heart rate, less potent than other drugs for glaucoma (dogs), avoid in patients with respiratory or cardiac disease
What are some Topical Antibiotics used for the eyes? Do they penetrate the cornea epithelium or no?
- Triple Antibiotic (BNP) - NO PENETRATION
- Aminoglycosides (Tobramycin, Gentamicin) - NO PENETRATION
- Tetracycline (Terramycin) - NO PENETRATION
- Macrolide (Erythromycin) - NO PENETRATION
- Fluoroquinolones (Ciprofloxacin, Ofloxacin) - YES, CAN PENETRATE
- Cephalosporin (Cefazolin) - NO PENETRATION
What are the pros and cons to Triple Antibiotics?
Triple antibiotic combinations (Neomycin-polymixin-bacitracin ophthalmic ointment; Neomycin-polymixin-gramicidin ophthalmic solution)
Advantages: Good choice to prevent infection of UNCOMPLICATED ulcers, wide spectrum of activity, bactericidal
Limitations: Poor corneal penetration, ineffective against Chlamydophila and Mycoplasma spp., rarely associated with anaphylaxis in cats (polymyxin)
What are the pros and cons to Aminoglycosides?
Aminoglycosides (Gentamicin ophthalmic ointment/solution; Tobramycin ophthalmic solution; Amikacin from parenteral formulation)
Advantages: Bactericidal, good gram-negative spectrum
Limitations: Poor corneal penetration, narrow gram-positive spectrum (not good against gram +)
What are the pros and cons to Tetracylines?
Tetracyclines (Oxytetracycline-polymixin B ophthalmic ointment)
Advantages: Wide spectrum of activity, bactericidal (polymixin B), effective against Chlamydophila and Mycoplasma spp. in cats
Limitations: Bacteriostatic (oxytetracycline), poor corneal penetration, rarely associated with anaphylaxis in cats (polymyxin b)
What are pros and cons to Macrolides?
Macrolides (Erythromycin ophthalmic ointment)
Advantages: Good gram-positive spectrum, effective against Chlamydophila and Mycoplasma spp. in cats
Limitations: Poor gram-negative spectrum, poor corneal penetration.
What are pros and cons to Fluoroquinolones?
Fluoroquinolones (Ofloxacin or moxifloxacin ophthalmic solutions, Ciprofloxacin ophthalmic solution/ointment)
Advantages: Good choice for INFECTED ulcers, bactericidal, wide spectrum of activity, excellent corneal penetration
Limitations: Indiscriminate prophylactic use could lead to resistance
What are pros and cons to Cephalosporins?
Cephalosporins (Cefazolin from parental formulation)
Advantages: Good gram-positive spectrum
Limitations: Poor gram-negative spectrum, poor corneal penetration, must be formulated by a compounding pharmacy or at the veterinary clinic – IV or IM, no topical
What are some Corticosteroids that can be used in the eye? Do they penetrate or no?
- Hydrocortisone - NO PENETRATION
- Dexamethasone - YES, CAN PENETRATE
- Prednisolone - YES, CAN PENETRATE
DON’T USE WITH ULCERS
What are pros and cons to Hydrocortisone?
Neomycin-polymixin-bacitracin-hydrocortisone (Ophthalmic ointment/suspension)
Advantages: May be useful for mild conjunctivitis cases in dogs
Limitations: Poor corneal penetration, delays corneal wound healing and hould be avoided with corneal ulceration or infection, rarely associated with anaphylaxis in cats (polymyxin)
What are pros and cons to Dexamethasone?
Neomycin-polymixin-dexamethasone (Ophthalmic ointment/suspension)
Advantages: Good corneal penetration, potent anti-inflammatory, decreases corneal vascularization and melanosis
Limitations: Delays corneal wound healing and should be avoided with corneal ulceration or infection, less potent than prednisolone, frequent/long-term administration may disrupt diabetes mellitus management or cause reversible adrenocortical suppression, rarely associated with anaphylaxis in cats
What are pros and cons to Prednisolone?
Prednisolone acetate (Ophthalmic suspension)
Advantages: Good corneal penetration, potent anti-inflammatory, decreases corneal vascularization and melanosis
Limitations: Delays corneal wound healing and should be avoided with corneal ulceration or infection, more potent than dexamethasone, frequent/long-term administration may disrupt diabetes mellitus management or cause reversible adrenocortical suppression
Ointment or drops?
- Client preference
- Animal preference
- Cost
- Availability
- Wound healing?
- Contact time
- Ruptured globes
–Solutions - Presurgical
–Solutions - Atropine (cats)
–Ointments
One drop or two drops?
- Always one drop
- Least to most viscous (do solutions then ointments)
- Always leave > 5 mins between drops
