Ophthalmology Flashcards
Photopic vision is….
Vision under well lit conditions, which provides for color perception, and which functions primarily due to cone cells in the eye.
Scotopic vision is…
Monochromatic vision in very low light, which functions primarily due to rod cells in the eye.
Define buphthalmia:
Enlargement of the eyeball. Usually indicates the presence of congenital glaucoma.
Define microphthalmia:
One or both eyeballs are abnormally small. This condition arises before birth.
Define strabismus:
Abnormal alightment of the eyes, can be medial or lateral.
Define enophthalmos:
Posterior displacement of the eyeball within the orbit due to changes in the volume of the orbit (bone) relative to its contents (the eyeball and orbital fat) or loss of function of the orbitalis muscle.
Define exophthalmos:
Anterior movement of the eyeball so that it sits in an abnormal position in the socket (orbit). Should not be confused with buphthalmia b/c with exophthalmos the size of the eye itself is normal.
The Menace Response involves which 2 cranial nerves?
In: CN II
Out: CN VII
The Dazzle Reflex involves which 2 cranial nerves?
In: CN II
Out: CN VII
How do you perform the Menace Response?
You make a menacing gesture at the dog or cats face and the expected response is that they will blink as you push your hand toward the eye. (Careful not to move wind toward the eyeball).
How do you perform the Dazzle Reflex?
Shine a lot at the animal’s eye and the response is that they should have rapid partial or complete blink in response to bright light or the patient averts its head.
The PLR (Pupillary Light Reflex) involves which 2 cranial nerves?
In: CN II
Out: CN III
How do you perform PLRs?
Shining a light into the animal’s eye the pupil should constrict (the eye that you are shining the light in is a direct PLR if there is constriction), watch the contralateral eye and if there is constriction as well that is your consensual PLR).
In addition to assessing CN’s II and III, PLR’s check the function of what?
Retina, iris sphincter and mid-brain.
[All of these need to be intact to get normal PLRs]
What is the palpebral blink reflex?
Touching the medial or lateral canthus of the eye to elicit a blink reflex in the animal.
The Palpebral Blink Reflex checks what 2 CN’s?
In: CN V
Out: CN VII
In addition to testing CN’s V and VII, the palpebral blink reflex also tests the function of what?
Orbicularis oculi muscle
How do you perform the vestibulo-ocular reflex?
This is also called the Doll’s Eye Reflex.
Move the head side to side and up and down which will create physiologic nystagmus that stops when the movement stops.
Fast phase is in the direction of the head’s motion.
The Vestibulo-ocular Reflex checks what things?
CN III, IV, VI, VIII, and extraocular mm.
What are your 3 basic ophthalmic tests and in which order should you perform them?
- Schirmer tear test (STT)
- Fluorescein stain
- Tonometry (IOP)
What are normal values for a dog and cat for the Schirmer Tear Test?
Dog >15 mm/min
Cat >5 mm/min
What is the purpose of a fluorescein stain test?
To check for corneal ulcers.
Which portion of the eye takes up dye if there is a corneal ulcer present?
Hydrophilic stroma if the cornea is eroded.
This type of tonometer uses applanation:
Tonopen (the most commonly used one in veterinary practice).
