Practical techniques for eye exams Flashcards
Schirmer tear test
60 seconds in the ventral conjunctival fornix between the lower lid and the third eyelid.
Do not touch the notched end with your fingers
If you like to fold, do it PRIOR to removing from the plastic package.
Always perform on BOTH eyes!
STT, species references..
Canine
18.84 +- 4.47
23.90 +- 5.12
21 +- 4.2
<10 = suspicious for KCS
<5- diagnostic for KCS
STT specie references..
Feline
14.3 +- 4.7
16.92 +- 5.73
Normal cats can have <5-10
Equine STT values
20.6 +- 6.5
24.8 +- 4.8
<10 = diagnostic for KCS
Explain the purpose of the STT.
?
Name the medical condition associated with an abnormally LOW STT
Research appropriate medical management options for the condition.
Recognize appropriate surgical management options for the condition including advantages and disadvantages of the procedure.
Review risk factors for the development of the condition.
Fluorescein test
Technique
- Fluorescein is a water-soluble, ophthalmic dye that is typically impregnated into sterile strips.
- Moisten a strip with a drop of sterile saline
- Allow a drop of dye to then fall upon each eye. In the event that you need to touch the strip to the eye, touch the strip to the sclera so that you do not artificially create what appears to be an area of fluorescein uptake on the surface of the cornea
- Now flush the eye gently with eye wash so as to rinse off the excess.
- If the cornea is intact, the dye will not stick.
- If the cornea is damaged, the fluorescein will adhere to the stromal layer.
- Observing fluorescein uptake is enhanced by using a blue light – either a Wood’s lamp or a filter on your standard direct ophthalmoscope.
- Note: Descemet’s membrane does not uptake fluorescein. Therefore, a clear area at the base of a deep defect in the cornea is a bad sign: it means that the ulcer is deep and in danger of rupturing.
Alternative flur. stain method..
Note: An alternate approach to fluorescein staining is to place the fluorescein strip in a 3cc syringe that is capped at the needle end. You then add sterile saline to the syringe, replace the plunger, and give a gentle shake to the syringe to create a slurry of dye that can then be squirted onto the each eye after the needle has been removed from the syringe.
ID…
desemetocele
Appreciate what a normal fundus looks like for both a dog and cat:
practical techniques paper
Feline fundus - normal-
practical techniques paper
What are the four structures you can ID when performing a fundic exam?
- optic disc
- retina
- tapetum
- retinal and choroidal vasculature
Identify what category of ophthalmic drugs you could use to facilitate the fundic examination by inducing pupillary dilation. Name two drugs that fit into this category, and be able to classify each as either short-acting or long-acting
Category of Ophthalmic Drug: Mydriatics
Two Types of Drugs in this Category:
o Atropine sulfate 1% (long-acting)
o Tropicamide 0.5% or 1% (short-acting)
The more negative (red) the diopter setting
the more DIVERGING power the lens possesses, and you are able to focus more posterior / caudally
The more positive (green) the diopter setting
the more CONVERGING power the lens possesses, and you are able to focus more anterior / cranially
in the eye a distance of 3 diopters equals..
1 mm
Image orientation by direct ophthalmoscope..
upright and more magnified with a smaller field of view
To perform indirect ophthalmoscopy, the clinician begins by
standing at a flexed arm’s length from the patient. The clinician then places a strong light source at eye level alongside his head. With the light source maintaining its position alongside his head, the clinician should direct the light at the patient’s eye to catch the tapetal reflection. Once the tapetal reflection is captured, the clinician must bring the lens in between himself and the patient. For stability, the clinician may rest the hand that is holding the lens against the patient’s brow.
With the lens in place and perpendicular to the light source, the fundic image should be visible albeit inverted.
The clinician may then adjust his view by moving the lens towards and away from the eye until the eyelids and iris disappear from view, allowing the fundic image to fill the lens.
the image orientation that is produced by an indirect ophthalmoscope
The view is upside-down and backwards, less magnified with a larger field of view.
Normal tonometry measurements dog:
Normal, dog: 15-25mmHg
Normal tonometry measurements cat:
Normal, cat: 15-30mmHg
Equine normal tonometry measurments..
12-28 mmHg
TonoPen works via
applanation tonometry: the TonoPen measures the force required to flattan, or applanate a constant area of cornea. Pressure = force / area
(softer blue rubber tip)
TonoVET works via..
TonoVet works via rebound tonometry: a small probe is rapidly propelled from a fixed distance to contact the cornea before returning (rebounding) to the instrument. The rebound characteristics are assessed to determine IOP.
small ball tip
High intraocular pressure?
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Low intraocular pressure?
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Name two antibiotics (or antibiotic combination products) that are used topically as ophthalmic prescription drugs
o Aminoglycosides Tobramycin sulfate 0.3% Gentamicin 0.3% o Triple antibiotic combo NeoPolyBac o Multiple antibiotic + steroid NeoPolyDex NeoPolyBac with Hydrocortisone o Fluoroquinolones Ofloxacin 0.3% o Tetracyclines Oxytetracycline HCl and Polymyxin B Ophthalmic Ointment (containing oxytetracycline 5mg/g; polymyxin B sulfate 10,000 units/g; white petrolatum, and liquid petrolatum.) in 3.5 g ointment tubes --- Terramycin® o Macrolides Erythromycin 0.5%
Aminoglycosides
i. Bactericidal
ii. Concentration-dependent
iii. Interfere with protein synthesis
1. To reach the ribosome, these drugs must first cross the lipopolysaccharide layer (in gram-negative organisms), the bacterial cell wall, and finally the cell membrane.
2. Because of the polarity of these compounds, a specialized active transport process is required.
3. Anaerobic bacteria are generally resistant, because they lack appropriate transport systems
iv. Synergism is common when aminoglycosides and β-lactam antibiotics (penicillins and cephalosporins) are used in combination. The cell-wall injury induced by the β-lactam compounds allows increased uptake of the aminoglycoside by the bacteria because of easier accessibility to the bacterial cell membrane.
Fluoroquinolones
i. Bactericidal
ii. Inhibit nucleic acid synthesis.
1. Bind to the DNA gyrase-DNA complex to induce defects in supercoiling
2. This renders the bacteria unable to multiply and survive.
Macrolides
i. Generally bacteriostatic, but may be bactericidal at high concentrations or if there are a low number of a highly susceptible bacterial organism
ii. Inhibit protein synthesis.
1. Macrolides reversibly bind to 50S subunit of the ribosomes and inhibit transpeptidation and translocation processes
2. This results in premature detachment of incomplete polypeptide chains.
Polymixins
i. Bactericidal
ii. Inhibit cell membrane function.
1. Disrupt the structure of cell membrane phospholipids and increase cell permeability by a detergent-like action, causing cell death.
2. Polymixins have also been shown to neutralize endotoxins.
Tetracyclines
i. Bacteriostatic
ii. Inhibit protein synthesis.
1. Reversibly binds to receptors on the 30S ribosomal subunit of the bacteria
2. This prevents the addition of amino acids to the elongating peptide chain, preventing synthesis of proteins
Identify the circumstance(s) under which the ophthalmic use of corticosteroids is contraindicated and be able to explain why:
a. When a corneal ulcer is present
i. Corticosteroids can impair corneal wound healing by inhibiting epithelial proliferation and migration; suppressing local immune factors; and promoting collagenase enzyme production.
ii. Administering corticosteroids in the face of a corneal ulcer can lead to catastrophic corneal “melting”
Identify the circumstance(s) under which the ophthalmic use of NSAIDS is contraindicated and be able to explain why
a. When a patient has glaucoma or is predisposed to glaucoma
i. Topical NSAIDS in dogs has been shown to increase intraocular pressure by decreasing aqueous outflow through the iridocorneal angle
Name one ophthalmic anti-inflammatory drug and explain when you might prescribe it
a. Flurbiprofen 0.03%
b. Diclofenac 0.1%
c. May be indicated to manage blepharitis, conjunctivitis, keratitis, uveitis, or as prophylaxis for lens-induced uveitis
Name a topical ophthalmic anesthetic used in veterinary medicine and explain when it might be advisable to use this product?
a. Proparicaine HCl 0.5%
b. Prior to certain methods of tonometry, i.e. Tonopen
c. Prior to certain procedures, i.e. grid keratotomy
