Opthalmology Flashcards
1
Q
Primary Glaucoma in Dogs
A
- Primary glaucoma in dogs is associated with an inherited malformation and malfunction in the ICA.
- Over time, the capacity for AH outflow is reduced and IOP increases.
- Primary glaucoma is strongly breed related, and some of the most commonly affected dog breeds are the beagle, basset hound, Boston terrier, cocker spaniel, and shar-pei.
- Other breeds that are commonly affected include the Siberian husky, Samoyed, Labrador retriever, and toy poodle. Mixed-breed dogs are also affected by primary glaucoma
2
Q
Equine Corneal Ulcers
A
- Corneal ulceration is a very common disease of the equine eye and can have sight threatening consequences.
- Aggressive treatment is always indicated, as even apparently mild ulcers can progress quickly, causing serious complication
- Clinical Signs Include:
ocular pain manifested as blepharospasms, increased lacrimation and photophobia. Corneal oedema, scleral injection and conjunctivitis are also often present.
- Signs of infection may include: necrotic edges, a cratered base, severe manifestations of pain and inflammation.
possible causes:
- trauma
- exposure keratitis
- FB’s
- fungal/bacterial infections
3
Q
Fluorescein Stain
A
- Fluorescein is an orange stain that is applied to the cornea to reveal corneal lesions.
- Once the stain is applied to the eye, the excess is rinsed off, and the remainder turns fluorescent green.
- The stain adheres to any areas where the surface layer of the cornea (the epithelium) is missing and where the underlying layer (corneal collagen or stroma) has been exposed.
- This test outlines the extent of any ulceration and permits more accurate assessment of the size, depth and type of ulcer.
- A fluorescein stain is indicated anytime a dog has a red or painful eye, or if any corneal irregularities or trauma to the eye are noted
4
Q
Melting Corneal Ulcers
A
- These ulcers are most frequently seen in dogs, but also occur sporadically in cats.
- Corneal trauma is the most frequently suspected initiating cause with regards to subsequent bacterial infection.
- Chemical injury, particularly alkali burns to the cornea, can also result in melting ulcer development.
- Matrix metalloproteases (MMPs) are enzymes usually responsible for the removal of dead cells and debris from the ocular surface.
- However, in melting ulcers, the number of these protease and collagenase enzymes becomes excessive, and can result in rapid destruction of the corneal stroma
- The bacteria most frequently responsible for these enzymes, and thus associated with these ulcers, are Pseudomonas aeruginosa, Staphylococcus species and Streptococcus species
5
Q
Oculocardiac Reflex
A
- The Oculocardiac reflex, also known as Aschner phenomenon, Aschner reflex, or Aschner–Dagnini reflex, is a decrease in pulse rate associated with traction applied to extraocular muscles and/or compression of the eyeball
6
Q
Brachycephalic Ocular Syndrome
A
- Because of their extreme brachycephalic (short) head shape and its consequences on the anatomy (shape and positioning) of the eyes and surrounding tissues, Shih tzus are prone to several eye conditions that tend to lead to chronic irritation and pain.
- It seems likely that prevalence of these diseases will be lower in those with less extremely abnormal head shapes (compared with more typical canine head shape)
- Brachycephalic ocular disease is the name given to a syndrome seen in brachycephelic animals that often combines lesions of the eyelid, conjunctiva (the tissues lining the eyeballs and eyelids) and cornea (the tissue forming the clear front surface to the eyeball)
- Dogs affected by this syndrome may show various conformational abnormalities of the eye including exophthalmos, macropalpebral fissure, and lagophthalmia (inability to close the eyelids completely)
7
Q
Anterior Lens Luxation in Dogs
A
- Medical Emergency!
- Primary lens luxation usually affects middle-aged terriers or Shar-Peis.
- It is associated with zonular defects due to a genetic mutation in ADAMTS17.
- Secondary lens luxation can occur in dogs because of hypermature cataracts, chronic anterior uveitis, chronic glaucoma, and microphakia
8
Q
Presentation of Lens Luxation in Dogs
A
Anterior lens luxation often presents with:
- elevated intraocular pressure (IOP)
- concomitant diffuse corneal edema
- blepharospasm
- tearing
- episcleral and conjunctival hyperemia
The elevated IOP often results from pupillary blockage, with vitreous adherent to the posterior lens capsule and/or secondary iridocorneal angle closure.
Applanation tonometry should be directed away from the lens because IOPs measured from the central cornea may yield erroneously high measurements.
Direct examination of the posterior segment is often not possible because of corneal edema, and B-scan ultrasonography may be used to evaluate the integrity of the retina and vitreous
9
Q
Lens Luxation in Cats
(and Horses)
A
- In cats and horses, the most common cause of lens luxation is chronic anterior uveitis
- lens luxation occurs when there is breakdown of the supporting lens zonules. In cats, lens luxation usually occurs secondary to other intraocular disease, in particular uveitis.
- often bilateral and in older cats
- Anterior lens luxation is associated with corneal damage and secondary glaucoma
- Cats tend to have a cornea with increased depth and therefore have less obstruction and resulting glaucoma with lens luxation
10
Q
Treatment for Lens Luxation
A
- lowering IOP with systemic carbonic anhydrase inhibitors (or mannitol, but not as preferred)
NOTE: topical prostaglandin analogs are contraindicated with anterior lens luxation because the intense miosis that occurs can trap the vitreous attached to the posterior lens and further increase IOP
- If the eye has the potential for vision (typically assessed with a dazzle reflex and consensual PLR), then lens removal, typically by intracapsular lens extraction, should be performed as soon as possible; eyes that are blind should be enucleated because this condition will result in a chronically painful globe.
- If surgery is declined, transpupillary aqueous humor flow may be reestablished with dilation with 1% atropine and/or 10% phenylephrine, and the dog’s head can be positioned so the lens can move back to the vitreous chamber
- Postoperative treatment consists of topical and systemic corticosteroids and antibiotics and topical antiglaucoma medications.
- IOP is closely monitored in the postoperative period, and additional antiglaucoma medications are prescribed as necessary
11
Q
IOP with glaucoma vs. uveitis
A
- get increase in IOP with glaucoma
- get decrease with uveitis
- can cancel eachother out in some cases so you need to look for indications for uveitis if pressures are normal (ex: aqueous flare)
- can use carbonic anhydrase inhibitors to bring down the pressure a bit and it won’t be excessive if you suspect glaucoma being involved
12
Q
Pthisis Bulbi
A
- is the final stage of a severe inflammation or trauma of the eye.
- Clinically the globe is hypotense, with a loss of intraocular architecture
- Phthisis bulbi represents an ocular end-stage disease of various causes and is defined by atrophy, shrinkage, and disorganization of the eyeball and intraocular contents
- Typical clinical symptoms and signs include chronic ocular hypotension (5 mmHg), a shrunken globe, pseudoenophthalmos, intraocular tissue fibrosis and scarring, vision loss, and recurrent episodes of intraocular irritation and pain
13
Q
Intravitreal Low Dose Gentamicin
A
- Treatment of recurrent or persistent uveitis in horses
14
Q
Goniodysgenesis
A
- Goniodysgenesis, also known as mesodermal dysgenesis, is an abnormality of the anterior chamber of the eye, and it has been associated with glaucoma and blindness
- Often associated with primary glaucoma
15
Q
Extraocular Myositis
(EOM)
A
- describes a primary inflammatory process affecting the extra ocular muscles in dogs.
- Clinical symptoms include acute‐onset, bilateral, symmetrical exophthalmos. Young, large‐breed dogs are commonly affected, notably the Golden Retriever.
- Clinical findings, notably exophthalmos secondary to swelling of the extraocular muscles help in the diagnosis of EOM.
- Treatment encompasses systemic immunosuppressive therapy, typically comprising corticosteroids, azathioprine, and/or cyclosporine.
- Therapy can frequently be tapered once symptoms are controlled; however, long‐term treatment may be required.
16
Q
Macroblepharon
A
- Abnormally Large Eyelid Opening
- Often seen in brachycephalic and some bloodhound breeds
- may lead to exposure keratopathy syndrome
17
Q
Propacaraine HCl
A
- Proparacaine HCl is a local anesthetic used primarily by ophthalmologists during examinations or diagnostic tests for dogs and cats. Proparacaine basically numbs the eye.
- When applied topically, proparacaine has a rapid onset of action and its effects last for at least 15 minutes. It does not penetrate the eye well, but is absorbed across mucous membranes such as the conjunctiva.
- Although it is related chemically to other anesthetic agents, such as lidocaine, bupivacaine, novocaine and cocaine, it is considered too toxic to be produced in injectable form
18
Q
“Cherry Eye”
A
- “Cherry eye,” as it is commonly referred to, is a prolapsed gland of the nictitans. It occurs after a tear gland in a dog’s third eyelid becomes inflamed. While it is usually not extremely painful, sometimes a dog will rub at it as if it were itchy
- Surgery is nearly always necessary if needing treatment. The gland will need to be sewn back into a pocket inside the third eyelid.
- Unfortunately, it’s fairly common for the gland to pop back out after surgery and it can take a few attempts to cure it completely. Some dogs may need to visit a specialist eye hospital.
- In the past, surgery was performed to remove the gland. This is not advised anymore – the gland is important for producing tears and if it’s removed a condition called dry eye can develop
- Can do an anchoring (more invasive) technique or Morgans Pocket technique (less invasive)
- or both if needed!
19
Q
3 forms of Retinal Detachment
(pathophysiologies)
A
- Rhegmatogenous - more related to age, cataracts, traction from inflammatory debris, vitreal degeneration, trauma or retinal degeneration –> vitreous fluid moves into the subretinal space –> resulting in detachment - most often associated with cataracts and cataract/lens Sx
- Exudative - Fluid accumulates in the subretinal space because of breakdown of the blood retinal barrier. Subretinal fluid may beserous hemorrhagic, or exudative. Can be granulomatous in patients with blastomycosis –> common causes: hematogenous/systemic pathogenic factors. Vasculitis. Hypertension, hyperviscosity
- Traction - usually by fibrous or fibrovascular tissue; detaches retina and/or may cause serous detachment with or without hemorrhage
20
Q
Progressive Retinal Atrophy
(PRA)
A
- Progressive retinal atrophy (PRA), is a group of degenerative diseases that affect the photoreceptor cells of the retina.
- With this disease, the cells deteriorate over time, eventually leading to blindness in the affected dog
21
Q
Function of the Retina
A
- The retina is a light sensitive layer of cells at the back of the eye that contains cells called photoreceptors.
- When light enters the eyes, it is focused by the lens onto the retina, where it is converted into electrical signals that are sent to the brain for processing and interpretation.
- The two main photoreceptor cells of the retina are the rod cells and the cone cells.
- The dog’s eyes contain many more rods than cones.
- Rod cells are responsible for vision in low light conditions and for detecting and following movement.
- Cone cells are responsible for detecting color. Cone cells do not work very well in low light
22
Q
2 different forms of PRA
A
- There are two main forms of PRA recognized in dogs, an early onset or inherited form, also called retinal dysplasia, which is typically diagnosed in puppies around 2-3 months of age, and a late onset form that is detected in adult dogs, usually between the ages of 3-9 years.
- It is common for the late onset form to be called PRA and the early onset form to be called retinal dysplasia
27
Q
Pourfour du Petit Syndrome
A
- Pourfour du Petit syndrome is a rare dysautonomic disorder characterized by mydriasis, eyelid retraction, and hyperhidrosis and is caused by irritative stimulation of the sympathetic cervical chain
- opposite to Horners presentation
- can often be seen in cats
28
Q
Diffuse Eye Melanoma
A
- often seen in cats
- Intraocular melanomas are rare, but the diffuse iris (iridal) melanoma – referred to as ‘diffuse’ because it has the ability to spread – is the most common primary intraocular (inside the eye) tumor in cats.
- Diffuse iris melanomas develop from the melanocytes of the iris.
- Iris surface as well as architecture are changed
- Often start as “freckles” on the iris surface
- They are often malignant (cancerous) - about 60%
32
Q
Causes of Superficial Corneal Ulceration in Dogs
A
34
Q
Treatment for Uncomplicated Superficial Corneal Ulcer
(5)
A
35
Q
Histopath Section of Normal Canine Cornea
(4)
A
36
Q
Complicated Corneal Ulcers
A
- Involve the corneal stroma, and/or
- Have some depth to them, and/or
- Persist longer than 1 week, and/or
- Are infected (often shown by white cell infiltrate), and/or
- Are malacic (melting)
37
Q
Causes of Complicated Corneal Ulceration in Dogs
(3)
A
38
Q
Treatment of Complicated Corneal Ulcer
A
- Aggressive - may be advisable to use a 2nd generation fluoroquinolone (ex: ofloxacin or suprafloxacin) or even rocking it up to a 4th generation fluoroquinolone
39
Q
2 methods to provide structural support for deep ulcer or descmetocele
A
- Conjunctival graft being the most common
- no matter the case: prognosis is fair (may take several weeks to heal), scarring may or may not affect the vision in the long run
40
Q
What structures is the Uvea comprised of?
(3)
A
posterior uveitis can also be “choroditis”
42
Q
What may present of Opthalmic Exam with Anterior Uveitis
(9)
A
- aqueous flare is a pathopneumonic sign
- corneal oedema may be due to breakdown or dysfuction of the corneal epithelial cells
- keratic precipitates- dark brown dots (inflammatory cells settled on the corneal epithelium)
- may see posterior synechiae in more severe cases (bottom corner pic, also shows iridal thickening)
44
Q
Causes of Anterior Uveitis
A
- Intraocular causes not as common as idiopathic
- cataract cause less common in cats, more common in dogs
- most common intraocular tumor in cats is: diffuse iris melanoma
- Neoplastic: secondary neoplasia that arrive into the eye. lymphoma by far the most common
45
Q
Infectious Causes of Feline Anterior Uveitis
(4F’s, T and B)
A
47
Q
Treatment for Feline anterior uveitis
A
- be careful not to use atropine if IOP is high! May push the eye into secondary glaucoma
- when using steroids, be careful not to cause a recrudenscence or flare up of a latent Feline Herpes Virus (FHV) - need to monitor closely! Prophylactic anti-viral therapy can be useful in this case as well
49
Q
What type of ulcer is PATHOGNOMONIC for FHV-1 infections in adult cats?
A
- Dendritic ulcer
other signs in adult cats may include: conjunctival hyperemia, chemosis, seromucoid to mucoid discharge, chronic interstitial keratitis
