Flashcards in Iris Deck (54):
How can you differentiate persistent pupillary membranes from anterior synechiae?
PPMs are thin, delicate, and regular from the iris collarette (synechiae are more random and thicker)
What is the treatment for PPMs
No treatment is needed
Red discoloration of the iris is called what? And indicated what?
Rubeosis iridis; CHRONIC inflammation (i.e. long enough that there is neovascularization)
What breed is known for esotropia (cross-eyes)?
Why is esotropia seen in Siamese cats?
- In the normal animal, "midline" of the retina is more temporal; this midline determines what nerve fibers will go to which side of the brain (the nasal part crosses to the other side).
- Siamese have an extra portion of fibers that cross
- These input from these fibers doesn't make sense, so is suppressed
- Siamese are thought to have cross-eyes because it places the nasal retina more frontal, which makes up for the lost crossed temporal fibers
Where do PPMs originate from?
If the iris attaches to the cornea, and the cornea turns white on the endothelium only, what is the white spot called?
What does PIFM stand for?
Pre-iridal fibrovascular membrane
What species have been shown to develop PIFMs?
Horses > dogs > cats > cattle
Other than the iris, where else do PIFMs form?
Optic disc, retina, lens... basically anywhere in the eye
What is the cause of PIFMs? 6 primary causes, which lead to the release of what?
Angiogenic proteins (predominantly VEGF)
Occurs secondary to
- severe/prolonged anterior uveitis
- retinal detachment
- neoplasms (ciliary epithelial, uveal melanoma)
- chronic glaucoma
- idiopathic ocular hemorrhage
What 3 breeds should be looked at prior to dilation for CERF exam to r/o PPMs?
Pembroke Welsh Corgi, Basenji, Mastiff
What breed should be looked at prior to dilation for CERF exam to r/o iris coloboma? What color is it usually seen in>
Merle Australian shepherd
What breed should be looked at prior to dilation for CERF exam to r/o iris hypoplasia/sphincter dysplasia?
What 3 forms of PPMs are most clinically significant?
Iris to cornea, iris to lens, or sheets of tissue can all cause significant vision loss
(iris to iris is usually not a big deal)
How common are PPMs in horses?
VERY common (like, every horse) -- think they are usually pupil-pupil?
In horses, most abscesses of the iris are produced by what?
How long will 1% atropine dilate a an eye if it is normal? Tropicamide?
If you have synechiae in a horse that have formed and you need to break them down and atropine alone isn't working, what can you add?
What does atropine do to the iris, and what does phenylephrine do?
Atropine = inhibits the constrictor muscle
Phenylephrine = causes contraction of the dilator muscle
After fibrin formation, how quickly can synechiae form in the equine eye?
What are 2 causes of iridodonesis?
Aphakia or lens luxation
PIFMs in horses are associated with what 2 disease processes?
What is a PIFM in the iris called?
How can PIFMs lead to hyphema?
They are very thin, fragile vessels that can break?
What is the main sequela to PIFM that is bad? How does that happen?
Glaucoma; form membrane over iridocorneal angle
What has to be present for PIFMs to form?
Some sort of ocular disease
4 causes of iris color change?
1) Neoplasia- Melanoma, LSA
4 causes of iris atrophy?
4. Secondary to glaucoma
What does iris atrophy have to be distinguished from and HOW do you do so?
Iris hypoplasia-- which is usually SYMMETRIC btwn eyes and the 6 o'clock position may be more affected (due to fetal fissures closing)
What iris tumor is associated with blue-eyed dogs?
Uveal Spindle Cell Tumor of Blue-Eyed Dogs
What breed is most associated with Uveal Spindle Cell Tumor of Blue-Eyed Dogs
Siberian Husky (and its mixes)
Is Uveal Spindle Cell Tumor of Blue-Eyed Dogs benign or malignant?
Other than vessels, how else can PIFMs manifest?
As fibrous bands (manifesting as ectropion uvea or synechiae, or fibrous bands elsewhere)--note these are pre-iridial FIBROvascular membranes
What can help prevent the formation of PIFMs?
What is ectropion uveae?
When the pigmented epithelium of the iris (usually on the posterior aspect) is pulled over onto the anterior aspect
What is the treatment for ectropion uveae?
Benign-- none needed
What causes a reverse-D pupil in cats? 2 differentials?
Loss of innervation to one side of the pupil (usually lateral, hence "reverse" D)
r/o FeLV since that can affect the nerves
How is pilocarpine used with reverse-D pupils in cats?
Helps r/o synechiae (NOTE: if nerve injury, pilocarpine will STILL cause constriction!)
Does asymmetric nasal or malar short ciliary nerve injury occur in animals other than the cat? If so, which ones?
NO... just the cat!
Where is a "typical" iris coloboma? Why?
6 o'clock; incomplete fusion of optic cup anteriorly
Raised, reddish-brown mass on iris of cat. 2 DDx?
1. Neoplasia -- do CXR, AUS first
2. Granuloma/Abscess (we are unsure what they are)-- PMN and MPs on cytology [try to r/o neoplasia before stick needle in eye!)
How are iris abscess/granulomas in cats treated? (Medically? Surgically?)
ABx (chloramphenicol) and steroids
CANT do surgery b/c involve major arterial circle of the iris = would likely lead to blindness
What is typical of the SIGNALMENT for iris granuloma/abscess in cats?
Usually very YOUNG cats
Risk of reoccurrence with iris granuloma/abscess in cats?
How do you aspirate an iris mass?
Under anesthesia, use 25-27G needle thru limbus, bevel up, and don't hit the lens or vessels of iris (hard to hit vessels b/c of orientation to iris)
What masses of the iris don't exfoliate well? (2 types)
Spindle cell and sarcomas
If you have an iris tear while aspirating an iris mass, what can you do?
Want to ideally get pressure up in eye (usually low post-aspiration) to apply pressure-- use dilute, preservative-free epinephrine
What causes iris bombe?
Adhesions that trap the aqueous and push the iris forward
Who is more likely to require treatment for their iris cysts-- cats or dogs?
Why are iris cysts a bigger issue in cats?
They tend to stay on the posterior surface of the iris and push it forward, leading to secondary glaucoma
How can you diagnose iris atrophy just based on visual appearance? (3 ways)
1. The edge will be scalloped
2. Thinning of the tissue on retroillumination
3. Early cases may have loss of stroma that exposes the posterior pigmented epithelium, so there are darker areas in the pupillary margin
How does iris atrophy affect the PLR?
It may be slow to absent