Ocular Anatomy and Pharmacology Flashcards
Which animals have a complete orbital ring?
Horse Ox Sheep Cattle Goat
Which animals have an incomplete ocular ring?
Pig
Dog
Cat
What are the bones that comprise the orbital anatomy (species dependent)? (7)
Frontal Temporal Zygomatic Maxillary Lacrimal Sphenoid Palatine
What bone does a dog’s orbit “lack” and what structure takes its place?
Temporal
Supraorbital ligament
What foramina are present in a dog’s orbit? (4)
Ethmoidal
Optic
Orbital fissure
Alar
What bones does a horse’s orbit “lack?”
Maxillary and palatine
What are the foramina present in a horse’s orbit? (5)
Ethmoidal Optic Orbital fissure Rostral alar Supraorbital
What are the four rectus muscles, two oblique muscles, and other muscle attached to the eye?
Superior/dorsal
Inferior/ventral
Medial
Lateral
Superior/dorsal
Inferior/ventral
Retractor bulbi
What muscles does CN3 innervate?
Dorsal, medial, ventral rectus
Ventral oblique
What muscles does CN4 innervate?
Dorsal oblique
What muscles does CN6 innervate?
Lateral rectus
Retractor bulbi
What are the three locations of conjunctiva?
Bulbar Palpebral Third eyelid - Anterior - Posterior
What are the functions of the conjunctiva?
Tear film Reduce friction of blinking Anatomic barrier Immunity Others
What are the areas of the lacrimal system?
Orbital lacrimal gland Gland of the third eyelid Nasolacrimal duct - 2 punctae - Punctum -> cannaliculus -> Lacrimal sac -> duct -> nose
What are the three tunics of the eye?
Fibrous
Vascular
Sensory
What are the parts of the fibrous layer of the eye and what do they do?
Cornea and sclera
Support and protection; provides shape to the eye
What are the parts of the vascular layer of the eye and what do they do?
Uveal tract (pigmented) - Iris, ciliary body, choroid
Provide nutrients, oxygen Removes waste products Aqueous humor production Lens accomodation Pupil shape
What are the muscles of the iris?
Sphincter muscle to constrict pupil
Dilator muscle to open pupil
What are the parts and functions of the ciliary body?
Anchor fibers that support lens Produce aqueous humor Contain muscles that alter lens shape - Accomodation - Near vs. distance vision
Where does the trabecular pathway exit the pupil into the cornea?
Iridocorneal angle
What happens if an animal has a closed iridocorneal angle?
Increased risk of glaucoma dt increased IOP
What is the sensory layer of the eye and what does it do?
Retina
Highly developed structure
Needs precise arrangement for optimal function
Species differences
How many layers does the retina have?
10
What are the structures present in the lens?
Lens capsule Anterior lens epithelium Lens fibers - Cortex - Nucleus Lens proteins Water
*Fibers added throughout life
What structures support the lens and how do they function?
Zonules
Vitreous
Iris
Help focus light on the retina
Free of nerves and blood vessels
What structures comprise the fundus?
Vitreous Retina - Vessels - Tapetum - Non-tapetum Optic disc
What retinal vascular pattern do dogs and cats have and what does that mean?
Holngiotic
The entirety of the retina is perfused by retinal vessels
What vascular pattern do horses have and what does it mean?
Paurangiotic
Tiny vessels only extend into retina a few mm, poorly vascularized
What vascular pattern do birds have and what does it mean?
Anangiotic
Blood supply comes from the choroid
What vascular pattern do rabbits have and what does it mean?
Merangiotic
Retinal vessels only medially and laterally from optic nerve
What is the order in which eye drops should be applied?
Watery
Oily
Gels
Ointments
- Wait 5 minutes between drops
- Only administer 1 drop at a time
- Ocular surface holds 10-25uL
What areas of the eye are accessed via topical administration?
Eyelids Conjunctiva Cornea - Epithelium is main site of resistance to drug penetration - Fat-water-fat sandwich Iris Anterior uvea
Sobconjunctival injection facts
Max volumes - SA: .25mL - LA: 1.0mL 27g or 25g needle Bulbar conjunctiva Used alone or along with topical therapy
What areas of the eye does subconjunctival injection reach?
Cornea
Anterior uvea
Anterior vitreous
Sclera
Most typically utilized for corticosteroid delivery Duration of subconjunctival injection - Prednisone 24-48h - Triamcinolone 2-3wk - Methylprednisolone 3-4wk - Betamethasone 3-4wk
Retrobulbar injection facts
Performed for local anesthesia Typically used in large animals Options: - Caudal to dorsal orbital rim - Peterson block - 4 point block Lidocaine is most common
Ocular implant facts
Sustained release of drug to ocular tissues Vet med = cyclosporine implant Most common uses: - Episcleral cyclosporine implant - Dry eye diseases - Immune-mediated keratitis - Suprachoroidal implant - Equine recurrent uveitis
Systemic administration facts
Generally does not penetrate the anterior segment as well as topical or subconjunctival medications
Blood-ocular barrier prevents access to eye
Provides treatment for
- Retina
- Optic nerve
- Vitreous
Often required for eyelid diseases
Subpalpebral lavage facts
- Medication administration system through eyelid
- Input medications in system at animal’s shoulder
- Medication “pushed” up to eye by flushing with air
- Commercial kit available from Mila International
- Allows frequent medication administration
- Only aqueous based medications should be used
- Not for creams or ointments
- Wait 5 min between meds
- Most commonly used in horses
- Minimizes risks
- Less risk for eye trauma from syringe or ointment tube
- No pressure on eye for administration
- Well tolerated by animal - less stressful
- Minimal placement side effects
CRI pump facts
Attaches to subpalpebral lavage catheter
Automated delivery system
Preset to specific rate (1-7d to give 10mL)
Commercially available
NOT RECOMMENDED FOR USE AT THIS TIME
What is the triple Abx combination and why is it effective?
Neomycin
Polymyxin
Bacitracin - ointment
Gramicidin - sol’n
Inexpensive and broad spectrum
T/F: Triple Abx are very effective in cats
False; DO NOT USE IN CATS
