Lens And Vitreous Flashcards
What do you call the suspensory ligaments connecting the ciliary body the the lens equator
Lens zonules
What is nuclear sclerosis?
New lens cells/fibers are produced through life, with age central lens fibers become compressed
What do you call the loss of accommodative power as nucleus hardens?
Presbyopia
How does the lens appear with nuclear sclerosis and how does it differ from a cataract?
Visible accentuation of lens nucleus
Bluish-gray, pearly haze
If there is any light passing through, its a nuclear sclerosis and not a cataract
- does not cause a clinically apparent blindness
- tapetal reflection visible through sclerotic lens
- fundus visible through sclerotic lens
What is a cataract?
Any opacity of the lens or its capsule
May interfere with vision
- tapetal reflection and fundus not visible through cataract but may be visible around cataract
What are the possible locations of cataracts??
Anterior or posterior capsular
Anterior or posterior subcapsular
Anterior or posterior cordial
Equatorial
Nuclear
How can you determine the location of a cataract?
Oblique examination = shine a brigh focal light along the visual axis and examine from oblique angle
Parallax
=anterior opacities move in same direction as eye
=posterior opacities move in opposite direction of the eye
=nuclear opacities appear to remain stationary
What are the stages of maturation of a cataract?
Incipient
Immature (incomplete)
Mature (complete)
Hypermature (resorting)
Intumescent (may be complete incomplete) - most often with DM and rapidly progressing cataracts
What stage is this cataract?
Small opacity
Tapetal reflection visible
Does not significantly interfere with vision
Incipient
What stage of cataract is this?
Tapetal reflection still visible
Variable effect on vision
Incomplete
Stage this cataract
100% of lens affected
Tapetal reflection is not visible
Eye is blind
Compete cataract
Stage this cataract
Lens decreases in volume and same size capsule
Capsule wrinkling
Deep anterior chamber
Tapetal reflection may return
Resorbing
Categorize the cataract
Increased lens size, shallow anterior chamber, separation clefts at Y-suture
Intumescent
What is the most common etiology of cataracts in dogs?
Inherited
What is the most common cause of cataracts in cats and horses?
Inflammatory (eg concurrent/previous uveitis)
What is the most common cause of a metabolic cataract?
Diabetes mellitus =. Hyperglycemia
Sorbitol accumulation in the lens draws in water and causes structural changes in the lens
What is the pathophysiology of diabetic cataracts?
Glucose shunted to an alternative pathway
Dogs have high levels of aldose reductase to make sorbitol
Sorbitol build up in lens and pulls in water
What can cause a nutritional cataract?
Puppies and kittens fed milk replacements — maybe due to amino acid deficiency
Characteristic perinuclear opacity — usually
Prevented by using milk of dam for the first week of life
Supplant with high quality milk replacer
What is an endogenous toxic cataract?
Degenerating photoreceptors release toxic substances into vitreous. —> seen in various degenerative retinal diseases like progressive retinal atrophy
T/F: most senile cataracts do not impair vision
True
What causes senile cataracts?
Photoodiative injury (UV light)
What are possible sequela of cataracts?
Visual impairment
Lens-induced uveitis
Glaucoma
Retinal detachments
What are the two forms of lens-induced uveitis?
Phacoclastic: severe form associated with traumatic tears of the lens capsule
Phacolytic: milder form associated with leakage of lens proteins from cataract (more common)
What type of lens induced uveitis should you suspect in any red eye with a cataract?
Phacolytic
— results from exposure of immunologically isolated lens protein to the immune system
Lens induced uveitis is treated how?
Topical steroid or NSAID
What is the treatment for cataracts?
Medical disssolution agents like N-acteylcarnoisne have no proven benefit
Anti-inflammatories - Diclofenac, flurbiprofen, or ketorolac
To treat lens induced uveitis
Surgical— phacoemlsification
High frequency vibrations emulsify cataract and remove it by aspiration through a small corneal incision
What do you call the presence of an articular intraocular lens post surgery?
Pseudophakia
What do you call absence of lens ?
Aphakia
What do you call displacement of themes form its normal position in the patellar fossa?
Luxation/subluxation
Occurs as result to loss of zonular ligament support
Primary inherited disorder causing lens luxation is common in what breeds?
Terriers
Abnormal degeneration of zonular ligaments
What is the most common cause of lens luxation in cats?
Chronic uveitis
Treatment for lens luxation?
Emergency — referral for intracapsular lens extraction
Decrease IOP prior to referral
- mannitol
- carbonic anhydrase inhibitors (dorzolamide)
NO Miotics or mydratics!
What is the medical treatment for lens luxation ?
Dilate the pupil with mydratic
Allow lens to fall behind the pupil
Trap the lens posteriorly with miotic —>latanoprost (BID)
Occasionally the lens can be pushed into the posterior segment through the pupil = couching
T/F: asteroid hyalosis sis when there are suspended lipid/calcium bodies in the vitreous which is a normal age related change
True
What are causes of vitreous hemorrhage?
Vasculopathies Coagulopathies Retinal detachment Trauma Intraocular tumors Congenital abnormalities Severe inflammation
What is vitreo-retinal dysplasia?
Liquefied vitreous preciouses to retinal tearing and detachment
—severe forms of rental dysplasia
—giant rentinal tears and detachments
