Ophthalmology

Question 1

Photopic vision is….

Answer 1

Vision under well lit conditions, which provides for color perception, and which functions primarily due to cone cells in the eye.

Question 2

Scotopic vision is…

Answer 2

Monochromatic vision in very low light, which functions primarily due to rod cells in the eye.

Question 3

Define buphthalmia:

Answer 3

Enlargement of the eyeball. Usually indicates the presence of congenital glaucoma.

Question 4

Define microphthalmia:

Answer 4

One or both eyeballs are abnormally small. This condition arises before birth.

Question 5

Define strabismus:

Answer 5

Abnormal alightment of the eyes, can be medial or lateral.

Question 6

Define enophthalmos:

Answer 6

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.

Question 7

Define exophthalmos:

Answer 7

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.

Question 8

The Menace Response involves which 2 cranial nerves?

Answer 8

In: CN II

Out: CN VII

Question 9

The Dazzle Reflex involves which 2 cranial nerves?

Answer 9

In: CN II

Out: CN VII

Question 10

How do you perform the Menace Response?

Answer 10

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).

Question 11

How do you perform the Dazzle Reflex?

Answer 11

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.

Question 12

The PLR (Pupillary Light Reflex) involves which 2 cranial nerves?

Answer 12

In: CN II

Out: CN III

Question 13

How do you perform PLRs?

Answer 13

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).

Question 14

In addition to assessing CN’s II and III, PLR’s check the function of what?

Answer 14

Retina, iris sphincter and mid-brain.

[All of these need to be intact to get normal PLRs]

Question 15

What is the palpebral blink reflex?

Answer 15

Touching the medial or lateral canthus of the eye to elicit a blink reflex in the animal.

Question 16

The Palpebral Blink Reflex checks what 2 CN’s?

Answer 16

In: CN V

Out: CN VII

Question 17

In addition to testing CN’s V and VII, the palpebral blink reflex also tests the function of what?

Answer 17

Orbicularis oculi muscle

Question 18

How do you perform the vestibulo-ocular reflex?

Answer 18

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.

Question 19

The Vestibulo-ocular Reflex checks what things?

Answer 19

CN III, IV, VI, VIII, and extraocular mm.

Question 20

What are your 3 basic ophthalmic tests and in which order should you perform them?

Answer 20

1. Schirmer tear test (STT)
2. Fluorescein stain
3. Tonometry (IOP)

Question 21

What are normal values for a dog and cat for the Schirmer Tear Test?

Answer 21

Dog >15 mm/min

Cat >5 mm/min

Question 22

What is the purpose of a fluorescein stain test?

Answer 22

To check for corneal ulcers.

Question 23

Which portion of the eye takes up dye if there is a corneal ulcer present?

Answer 23

Hydrophilic stroma if the cornea is eroded.

Question 24

This type of tonometer uses applanation:

Answer 24

Tonopen (the most commonly used one in veterinary practice).

Question 25

This type of tonometer uses indentation:

Answer 25

Schiotz (the oldest type out there and very infrequently used.)

Question 26

This type of tonometer uses rebound:

Answer 26

Tonovet (the latest and the greatest, mostly used in ophthalmology clinics.)

Question 27

What is the normal IOP range for dogs and cats?

Answer 27

10-25 mm Hg

Question 28

What are some causes of elevated IOPs in an animal?

Answer 28

Glaucoma

Restraint

Jugular occlusion

Pushing on the globe

Question 29

What are some causes of low IOP’s in an animal?

Answer 29

Uveitis

Decreased aqueous production

Question 30

When would checking IOPs be contraindicated?

Answer 30

In a patient with a corneal ulcer.

Question 31

You always want to check IOPs before dilating a pupil (mydriasis) why?

Answer 31

Because if you dilate the pupil it can aggravate glaucoma if the animal has that.

Question 32

What are 2 drugs used to dilate the pupil?

Answer 32

0.5% to 1% Tropicamide

1% Atropine

Question 33

What are the differences between Tropicamide and Atropine?

Answer 33

Tropicamide: Rapid acting (within 15-30 minutes), short duration (6-8 hours), well tolerated.

Atropine: Long lasting, not ideal for diagnostics, best for treatment of miosis due to ciliary spasm.

Question 34

In which 2 cases is Tropicamide contraindicated?

Answer 34

1. Glaucoma

and 2. Some Lens Luxations

KNOWWWW!!!

Question 35

Define hyphema:

Answer 35

Blood in the anterior chamber of the eye.

Question 36

Define hypopyon:

Answer 36

Pus in the anterior chamber of the eye.

Question 37

Define distichia:

Answer 37

An eyelash that arises from an abnormal location on the eyelid.

Question 38

Define entropion:

Answer 38

Genetic condition in which a portion of the eyelid is inverted or folded inward.

Question 39

Define ectropion:

Answer 39

A condition in which the eyelid is turned outward away from the eyeball.