The blind eye Flashcards
Define blephar
pertaining to eyelid
Define dacryo
pertaining to NLS
Define Kerat
pertaining to cornea
Define Irido
pertaining to iris
Define cyclo
pertaining to ciliary body
define phac
pertaining to lens
Define hyalo
Pertaining to the vitreous
What are the most important layers/cells in the retina?
10 different layers, in path of light:
Ganglion cells (form optic nerve)
Cells in inner retina
Photoreceptors (cones/rods) in outer retina
RPE = Retinal Pigment Epithelium, outer-most layer
Describe RPE
Retinal Pigment Epithelium
The only non-neural layer of the retina
It is a nurturing layer (to rods/cones).
What are rods for?
low light levels - night vision
What are cones for?
high light levels and colour vision
What layer does Retina Pigmentosa affect?
RPE
What is the path of a neural stimulus of light?
Optic nn (L and R) –> optic chiasm (decussation of fibres, 66% in cats, 75% dogs) –> optic tract (L and R) –> Optic radiaiton –> cerebral cortex
What are the 2 broad causes of blindness?
Problem with path travelled by light OR problem with the path travelled by neural stimulus
Outline eyelid disease
severe drooping of upper eyelids/skin –> blindness
Especially sniffer dogs/spaniels/ heavy foreheads and ears
Tx - eyelid dz
'Stades' procedure (upper eyelid) - minor cases Reduction of palpebral aperture Face lift (rhitydectomy) - severe cases
What are the 2 types of corneal disease that can cause blindness?
Chronic and acute pathology
Describe chronic corneal problems –> blindness
scarring, visualisation, pigment deposition
- KCS
- LPI/pannus (dogs)
- EK (cats)
- Sequestra (dead piece of cornea, usually cats)
Outline acute disease –> corneal scarring
Ulcerative:
KCS-related
Traumatic
Progression of ulcers through melting (inflammation, infxn)
What eye problem affects 90% pugs?
Pigmentary keratitis, a corneal problem
Outline Pigmentary Keratitis
Pigmnt and chronic corneal irritation
- Especially pugs with entropion
- Can be blinding in
What is PPM?
Persistent Pupillary Membranes
= failure of regression of foetal BVs in AC
- congenital
- strands arise at collarette (thickest region of iris, separates pupillary portion from ciliary portion) and span either: iris to iris, iris to cornea (–> leukoma, slowly progressive) or iris to lens (–> cataract, usually progressive)
What is symblepharon?
Adhesions of conjunctiva onto itself and cornea
What animal does symblepharon affect?
Kittens affected with ‘cat flu’ (FHV-1, caliciviurs, bordatella)
- -> corneal epithelial cell depletion (FHV-1)
- -> advancement of conjunctiva over cornea
- -> permanent focal or diffuse scar
- risk of FHV-1 recurrence later in life
What is the uvea made of?
it is a mesh of BVs, three parts:
- Iris
- ciliary body
- choroid
Function - choroid
feeds the outer retina which lies on top of it.
2 main features of uveitis. Name 4 others
- Inflammation –> leakage of plasma/blood
- Muscle contraction
- endothelial damage (–> corneal oedema)
- iris adhesions (to lens in pupillary zone = posterior synechiae or to cornea in ciliary zone = peripheral synechiae and closure of the ICA)
- Development of PIFMs –> can clog ICA (grow like ivy within the eye)
- Low IOP (one way to differentiate from glaucoma)
What are 3 infiltrations in uveitis
- turbid aqueous humor (flare)/ ventral AC (KPs)
- hypopion (WBC accumulation ventrally)
- hyphema (blood, small amount or entire AC)
- clots (in AC and/or vitreous)
What is the problem with mm contraction in uveitis?
- Pain (iris and CB mm spasm)
- Photophobia / miosis
What ocular problems (2) does hypertension in cats lead to?
hyphema or retinal detachment
What is the significance of uveitis? 5
- clogged/closed ICA –> secondary glaucoma
- posterior synechiae –> clouds pupil and visual axis
- secondary cataracts = cats, horses, less commonly dogs
- retinal detachment = leaks into space between layers 1 and 2
T/F: there is an intimate relationship between uveitis and cataracts
True :
- uveitis can lead to secondary cataracts (slowly progressive, can become mature. In cats, sometimes horses/dogs, can lead to lens luxation)
- Cataracts in their own right lead to a phacolytic uveitis (leakage of lens proteins (crystallines) into aqueous humor and loss of immune tolerance to this naturally encapsulation protein
What is phacoCLASTIC uveitis?
= Inflammation secondary to rupture of the lens capsule and release of lens proteins.
How is lens-induced uveitis classified?
- phacoLYTIC uveitis (non-granulomatous), secondary to lens leakage of denatured lens proteins from an intact capsule, usually during maturation or cataracts (think ‘phacoLEAKY’ because leaks proteins)
- phacoCLASTIC uveitis is Inflammation secondary to rupture of the lens capsule and release of lens proteins.
In which species does recurring uveitis occur most commonly?
horses and cats, can happen in any species though
Outline recurring uveitis
Primary insult (horses - leptospira, cats - Toxo, viruses) –> BOB breakdown –> anamnestic response triggered by epitopes and self-antigens. Most recurring uveitis are consdiered idiopathic
What is ERU?
= Equine Recurrent Uveitis, ‘ periodic ophthalmia’ and ‘moon blindness’
What can happen with chronic recurrent uveitis? 2
Cataracts and glaucoma
Tx principle - uveitis
Treat the cause if known/ possible/ apllicable
Which anti-inflammatories can be used to tx uveitis?
- TOPICAL - affect ulcer healing and diabetes, but effective. e.g. prednisolone acetate or dexamethasone phosphate, NSAIDS (don’t affect diabetic control, may not be as effective)
- SYSTEMIC - don’t affect ulcer healing if avascular, effective.
Name NSAIDs for topical uveitis tx
Ketorolac and Diclofenac etc.
Name systemic anti-inflammatories for uveitis tx
= for posterior uveitis, severe anterior uveitis, if not use topical
- STEROID: prednisolone tablets
- NSAIDs: meloxicam, carprofen, flunixin meglumine
What does the dose and length of tx depend on for uveitis tx?
- Dz prognosis
- CS severity
- initial response to tx
- topical tx starts with high frequency of application (4-6 times usually)
- recommended anti-inflammatory dose for systemic steroids/ NSAIDs
- severe immune-mediated dz may require immunosuppressive doses
Outline the use of a topical steroid in a diabetic post-cataract sx
- affects the pituitary-hypothalamic-adrenocortical axis BUT - high doses usually not necessary - taper off occurs promptly -many diabetics undergo cataract sx
Describe systemic hypertension in cats
- an uveal vasculopathy that can lead to blindness
- hyphema in AC and in vitreous
- retinal detachment (bullous)
- other end-organ diseases/ systemic problems
How can FIP/ FeLV/ FIV/ Toxo cause uveal vasculopathies that could lead to blindness?
Protein in AC, +/- lesions in the fundus +/- systemic dz
Where can material be located that is hazy in front o the pupil? 2
- cornea (no BVs)
- AC
How can fungal problems lead to uveal vasculopathies that can lead to blindness?
affects whole uvea, especially fundus.
- may affect RespT too
- Cripto in cats
How does leishmaniasis affect the eye? 3
–> panuveitis, keratitis and KCS (Mediterranean)
What is uveodermatological syndrome in dogs?
= aka VKH-lie syndrome
- severe anterior and posterior uveitis
- severe skin lesions (depigmentation, loss of hair and multiple skin lesions)
- immune-mediated dz against melanin precursors
- strong inflammation affects multiple areas where there is pigment
What does the CS fixed dilated pupil scream?
glaucoma due to chronic uveitis
What does coria refer to?
the pupil
Define isocoria
uneven sized pupil
Define dyscoria
an oddly shaped pupil
What is a cataracts and where can it be?
= an opacity in the lens that blocks the passage of light, ranges in size from dot to whole lens,
- any shape (punctate, linear, stellate etc)
- location (nuclear, cortical or equatorial)
- Ddx nuclear sclerosis
Describe congenital nuclear cataracts
causes usually unknown, most are non-progressive, rarely cause uveitis
Describe congenital PPM cataracts
- Most progress, mature cataract, and lens-induced uveitis
- PPMs arise from the iris colarette, an imaginary circle between the iridal part and the ciliary parts of the iris
What are the acquired types of cataracts?
- inherited
- DM (v. common in diabetic dogs)
- perforation trauma (blunt trauma doesn’t readily cause cataracts but can)
- age related (usually slowly progressive)
- hypocalcemia (rare in dogs, e.g. hypoparathyroid)
- rabbits and cats (associated with E.cuniculi)
- GPRA (end stage cases)
Describe diabetic cataracts
- rapid progression
- lens induced uveitis (conjunctival/episcleral hyperemia and low IOP)
- may lead to secondary glaucoma if unchecked (PIFMs)
- often show ‘water clefts’ on the anterior suture lines where lens material has dissolved.
What does a perinuclear cataracts look like?
Circular
Name 2 types of congenital vitreous problems
- persistent hyaloid vasculature
- failure of regression of foetal vasculature
- can –> cataracts and spontaneous haemorrhage
- rule out with eye ultrasound
Name 2 acquired vitreous problems
- syneresis (liquefaction)
- asteroid hyalosis (particular matter)
Describe syneresis
= an acquired vitreous problem, aka liquefaction
- may lead to retinal detachment in Shih-Tzus
- seen spontaneously with age and/or inflammation
Describe asteroid hyalosis
= particulate matter, calcium and cholesterol crystals fills the vitreous
- seen spontaneously, with age and/or inflammation
- often seen with syneresis in ultrasound
- if optically dense it will interfere with sight
Outline congenital retina dysplasia
- Inherited - cavalier, springer, others
- Malformed retina
- forms: mild/folds, multifocal and generalised (latter may –> retinal detachment)
- breeding advice recommended
- no tx
What is Collie Eye Anomalie?
= a choroidal hypoplasia in collies and shetland/sheepdogs lateral to the optic disc. It may be associated with a coloboma of the optic nerve head which may –> retinal detachment.
- Otherwise but usually associated with blindness
- breeding advice recommended
- no tx
Name 5 acute acquired retinal problems
- SARD = Sudden Acquired Retinal Detachment Syndrome
- IMR = Immune-mediated retinopathy
- GME = Granulomatous meningoencephalitis
- RDt = Bullous retinal detachment
- Toxic retinopathy
Describe SARD
= acute acquired retinal problem - sudden onset - bilateral \+/- PU/PD, cushings biochem - fundus looks normal - flat ERG due to sudden photoreceptor death - no (safe) tx
Describe IMR
= acute acquired retinal problem
- similar to SARD but not Cushing’s biochem
- ERG may be flat or not
- no tx (steroids if early but this is rarely seen)
What is GME and what are the forms?
= acute acquired retinal problem
- grized and optic nerve forms
- optic nerve head may or may not show haemorrhage
- ERG normal
- tx = steroids
What does bullous retinal detachment affect?
- cats with systemic hypertension
- rare form in dogs called ‘steroid-responsive RDt’
What causes toxic retinopathy?
- cats with oral enrofloxacin
- high risk at doses >5mg/kg but never a zero risk
- not thought to happen with other fluoroquinolones
- no tx (reversal of signs possible if tx withdrawn right away)
In which animals is GPRA seen?
many dogs and occasionally in some cats
What is the end-result of GPRA?
Pan-retinal degeneration:
no pain, gradual loss of vision, night blind to day blind, no tx, all other dx may look like GPRA given time
List 2 chronic acquired retinal problems
- GPRA
- retinal atrophy
Name 3 CS of retinal atrophy
- hyperreflectivity of the tapetum
- marked attenuation of the retinal vasculature
- (late stage - cataracts)
Does GPRA hurt a lot?
No - it is progressive
Name 2 dz that can make cats acutely blind
- hyphema
- retinal detachment
