Ophthalmic examination in horses Flashcards
How would you carry out distant direct ophthalmoscopy in a horse?
- Lens set on “0”
- Arms length
- Opacities appear as dark silhouette against bright tapetum
How are different magnifications used to examine the eye?
0 focuses on the retina
0 to -3D: Fundus
+2D to +6D: vitreous
+7D to +8D: Lens
+10D: cornea
Before carrying out the opthalmic exam what can be visually assessed?
- Observe the head from the front
- Angle of the eyes is raising or dropping
- Lids
- Eyelashes
- Any discharge
Which ocular reflexes can be assessed in horses?
PLR: direct and indirect
Dazzle reflex
Menace response
Palpebral reflex
Corneal reflex
When should ocular reflexes be carried out in an exam?
Before sedation
Which nerve blocks can be used to allow better examination of the eye?
Auriculopalpebral - horse can still blink but cant hold the eye closed
Frontal - used to desensitise the upper eyelid
Is dry eye common or uncommon in horses?
Uncommon
Which part of the eye does fluorescein stain?
Corneal stroma when there is damage to the epithelium
How does a superficial ulcer stain?
Sharp edges
No epithelial under-run
No stain migration
How does an indolent ulcer stain?
Epithelial under-run present
How does steep stromal ulceration stain?
Very intense staining with stain migration occurring (5-15 minutes)
Name the normal anatomical structure found in the margin of the iris in horses
Granula iridica
Name the structure found on the medial and lateral sides of the iris
Insertion of the pectinate ligament - drainage angle of the eye
How does a descemetocele stain?
Walls of ulcer stain intensely with stain migration occurring (5-15 minutes). Central ulcer transparent and takes up no stain
When is the seidel test used?
E.g. thorn in the eye – this test can be used once the thorn is removed to assess the depth of damage
When is rose bengal stain used?
- Assessing tear film quality
- Assessing margins of conjunctival and corneal neoplasia (SCC)
- Fungal ulcers
Why would you use a mydriatic in an ophthalmic exam?
To dilate the pupil for ease of exam
NOT atropine for just an exam
How is the pressure inside the eye measured?
Tonometry
