Lecture 2 1/28/25 Flashcards
What are the characteristics of ophthalmic solutions?
-safer when ocular integrity is questionable
-shorter contact time; does not last as long
What are the characteristics of ophthalmic ointments?
-cause severe uveitis if they enter the globe; should not be used when ocular integrity is compromised
-longer contact time; longer lasting
What are the characteristics of ophthalmic antimicrobial pharmacology?
-choose antibiotics based on C&S when possible
-base drug choice on cytology while waiting on C&S
-topical formulations can be prepared from IV preparations
-fortified concentrations can be made
-oral antibiotics may be indicated in perforations, eyelid disease, nasolacrimal disease, and vitreal infections
What are the components of triple antibiotic?
-neomycin
-polymyxin B
-bacitracin
Why is triple antibiotic routinely used for prophylaxis?
the combined drugs have a range that covers both gram + and gram - bacteria while rarely having resistance
What are the characteristics of aminoglycosides?
-covers gram - bacteria
-tobramycin is best choice; not toxic to corneal epithelium
What are the characteristics of chloramphenicol?
-covers gram +, some gram -, and mycoplasma
-does NOT cover pseudomonas
-penetrates deep into cornea even when cornea is intact
-not commonly used due to risk of causing aplastic anemia
What are the characteristics of cephalosporins?
-covers gram + and gram -
-low efficacy against pseudomonas
-can be mixed from pre-op cefazolin into an eye drop
What are the characteristics of fluoroquinolones?
-broad gram + and gram - spectrum, including mycoplasma and chlamydia
-reserved for severe infections; not for prophylaxis
-good penetration of intact epithelium
When is oxytetracycline/terramycin used?
indolent ulcers in dogs
What are the characteristics of serum as an anticollagenase agent?
-contains alpha macroglobulins that decrease matrix metalloproteinase activity; stops ulcer progression
-serum can be harvested from a healthy donor dog and frozen for a few months at a time
-important to not use cat serum for cats without running tests for infectious dz
Why must artificial tear gels and ointments be used in dogs instead of drops?
-drops have too brief of an effect to be useful
-ointments last the longest, while gels are less oily
What are the characteristics of atropine?
-onset of action is 1-2 hours in normal eyes
-duration of action is several days to several weeks in normal eyes
-uveitis prolongs onset of action and decreases duration of action
-should be avoided in glaucoma patients
-can cause decreased tear production
What is the action of atropine?
-paralyzes ciliary muscle to decrease pain
-paralyzes iris sphincter muscle to dilate pupil
What are the characteristics of tropicamide?
-routinely used for ophthalmic examinations
-onset of action of 10-20 minutes
-duration of action of 6-12 hours
-may not work in eyes with uveitis
-more safely used in glaucoma patients
What are the characteristics of proparacaine?
-topical anesthetic
-begins working almost immediately and lasts for about 20 minutes
-cannot be prescribed for home use; epithelial toxic
-should not be applied prior to a schirmer’s tear test
What is corneal ulceration?
lesion of the cornea that is a result of the loss of corneal epithelium +/- loss of stroma
How can loss of stroma be determined when looking at a corneal ulcer?
the ulcer will have a “scooped out” appearance
What are the four things that must be assessed about an ulcer?
-cause (most important part of evaluation)
-ulcer depth
-presence/absence of infection and matrix metalloproteinases
-rate of progression
What are the clinical signs associated with corneal ulcers?
-blepharospasm/squinting
-epiphora/excessive tearing
-corneal edema
-corneal vascularization
What causes pain from corneal ulcers?
-the cornea itself due to damaged nerve endings
-the ciliary body
What are the characteristics of fluorescein stain?
-diagnostic modality of choice for corneal ulcers
-fluorescein is hydrophilic and is taken up by the stroma
-descemet’s membrane and the epithelium are lipophilic and do not take up stain
-ulcer will appear green; color is accentuated by a cobalt blue light filter
What are the causes of corneal ulcers?
-trauma
-eyelash abnormalities
-eyelid abnormalities
-foreign bodies
-keratoconjunctivitis sicca/dry eye
-indolent ulceration
What is most important regarding treatment of ulcers that result from trauma?
-want to prevent infection in newly formed ulcers; treat with triple antibiotic ointment
-use atropine drops in clinic to prevent pain
How can an ulcer be determined to be chronic?
the presence of blood vessel formation within the cornea/surrounding the ulcer
What are ectopic cilia?
cilia originating from the tarsal gland that emanate from palpebral conjunctiva
What is the treatment for ectopic cilia?
excise cilia en bloc from conjunctiva using a derm punch; monitor patient at future appointments for growth of more cilia
What is entropion?
in turning of the eyelid margin, which results in hairs rubbing the cornea
What are the types of entropion?
-conformational
-spastic
-cicatricial
What are the characteristics of conformational entropion?
-due to disproportionate size of orbit and globe position
-common in shar peis, rottweilers, chows, and bulldogs
-does not correct with topical anesthesia
What is involutional entropion?
an acquired conformational entropion that occurs secondary to loss of orbital tissue
What are the characteristics of spastic entropion?
-secondary to ocular pain (such as with ulcers)
-pain causes animal to retract globe; allows eyelids to roll in
-corrects with topical anesthesia
What are the characteristics of cicatricial entropion?
-occurs when chronically spastic tissue scars and rolls in
-scar formation from trauma or severe skin disease can also be causatory
-does not correct with topical anesthesia
What are the characteristics of puppy entropion?
-occurs in puppies of breeds that often suffer from entropion
-permanent surgical correction is not done until dogs are older to prevent too much tissue from being removed
-temporary vertical mattress tacking sutures are placed to roll out the eyelids
-temp. sutures may help the eyelids develop a more normal position and reduce the need for permanent correction surgery
What is the modified holz celsus procedure?
corrective procedure from entropion that involves removing a crescent-shaped area of skin; suturing the incision pulls the eyelids out and places them in a normal position
