Flashcards in Len disease (other than cataracts) Deck (42):
What is septic lens implantation syndrome? What is the prognosis?
Penetrating injury leading to introduction of bacteria (or rarely fungi) into the eye, leading to a slowly progressive or delayed-onset endophalmitis, lens capsule rupture, and lenticular abscessation. This causes uveitis and secondary glaucoma.
What are common causes of septic lens implantation syndrome?
Cat scratch (#1) or phacoemulsification
What species has septic lens implantation syndrome been described in? What is the one breed that has been associated with the disease and when?
Described in dogs and cats; labrador is only known associated breed (with phacoemulsification)
What is the difference between phacolytic and phacoclastic uveitis? Include CAUSE and SEVERITY.
- traumatic lens capsule rupture
- sudden exposure of T cells to protein
- severe, requires surgery (phaco) to avoid loss of globe
- a MILD lymphocytic-plasmocytic uveitis (phacoLYtic is is LESS severe)
- secondary to release of lens protein through an intact lens capsule (as in RAPIDLY DEVELOPING or HYPERMATURE CATARACT)
- low dose of proteins cause T cell tolerance
- presumptive Dx based on observation of cataract
What is the main issue with microphakia?
May increase risk of luxation
What 2 conditions is microphakia possibly associated with?
2. Microphthalmos (small globe)
What is lenticonus?
A cone-shaped defect on one aspect of the lens (like a pimple on the lens)
Where on the lens does lenticonus usually occur?
The posterior pole of the lens
Although lenticonus is usually not a big deal, what is one thing that can happen that is very bad?
Posterior capsule is malformed = can get rupture of lens capsule = phacoclastic uveitis
What breeds have an inherited increased likelihood to lens luxation?
Terriers: Cairn, Jack Russell, Lakeland, Manchester, Miniature Bull, Norfolk, Norwich, Scottish, Skye, Sealyham, Smoothhaired Fox, Westie, Tibetan, Wirehaired Fox
Lens luxation and glaucoma-- explain chicken or egg?
Glaucoma --> buphthalmia --> stretch zonules --> luxation
Luxation --> secondary glaucoma
How can luxation or subluxation lead to glaucoma? (4 ways)
1. Entrapment of lens in anterior chamber (angle closure and/or pupil block)
2. Synechiae with iris bombe (pupil block)
3. Anterior vitreous prolapse (pupil block)
4. Inflammation within anterior segment, causing low-grade trauma to iris and ciliary body --> release of melanin --> inflammation and glaucoma
What is the issue with lens removal when in the posterior segment?
It can adhere to retina and pulling it out can detach the retina
In the dog, how can anterior lens luxation present (in regard to cornea)?
What age do you start to see the ring formed in the lens indicating earliest nuclear sclerosis?
How much of the lens is affected with lenticular sclerosis?
The nucleus only... hence also being called nuclear sclerosis
What are the common signs that a dog is having difficulty seeing from lenticular sclerosis?
1. Hesitating going DOWN stairs
2. Hesitating going into a dark room
3. Bobbing head when food is dropped
What are 6 causes of SECONDARY lens luxation in dogs?
2. Chronic uveitis
6. Hypermature cataract as they shrink
Aphakia causes what change in vision (in D)?
+15D (THICK glasses)
If you have a glaucomatous eye secondary to a lens luxation, what should you NOT do in terms of treatment?
Give dilating agents (lens may move anteriorly OR dilation may close drainage angles, precipitating glaucomatous crisis)
What is pseudophakia
An implanted intraocular lens
Where does the lens sit (structure)
Patellar fossa or hyaloid fossa (depression in vitreous)
What is pathognomic for lens subluxation
When are mydriatic agents appropriate for lens luxation (3)?
1. Couching procedure
2. Pupillary block
3. Post-lensectomy to prevent synechiae, improve comfort, and stabilize lens-ocular barrier
What tends to cause lens luxation in cats?
What work-up is recommended if there is a lens luxation in a cat?
Look for infectious causes (to help r/o uveitis as a cause)- FeLV/FIV, FIP, Toxo, etc
Why does retinal detachment sometimes follow lens luxation [NOTE: not bc of vitreous prolapse]
When partially luxated, lens pulls on zonules at focal spots = can detach retina
What meds are appropriate with a lens luxation and secondary glaucoma? [specifically, for the glaucoma]
Carbon anhydrase inhibitors and beta blockers
What drugs are appropriate for subluxated lenses?
Miotics-- helps stabilize the lens and can keep it from luxating completely for 1-2+ years
What 3 sequelae are common with luxated lenses? (and with lensectomy)
1. Glaucoma [also lensectomy]
2. Retinal detachment [also lensectomy]
3 Uveitis (from lens moving around)
How is the vitreous affected by lens luxation?
It tends to degenerate due to lens motion against it, and then prolapses into anterior chamber
Why is anterior lens luxation NOT as uncomfortable in cats as it is to dogs? (note SIZE of lens)
Canine lens is 0.5 mL (anterior chamber 0.4 mL) vs feline lens 0.3 mL and anterior chamber 0.6mL
In Jack Russels that are homozygous for the gene that causes lens luxation, what is the likelihood and age for bilateral lens luxation?
Both lenses usually luxate by 4-8 years of age
Does a couching procedure usually work?
Usually not long-term
What is the difference between phacoclastic uveitis and septic lens implantation syndrome?
SLIS involves bacterial cause setting off the uveitis and NOT the release of lens proteins. Phacoclastic uveitis is sterile.
Where in a lens will a lens coloboma be seen?
What causes lens coloboma?
Focal area where the zonules aren't applying tension
What causes spherophakia?
Diffuse lack of zonular tension
What is persistent tunica vasculosa lentis?
Congenital problem where the capillary network of the posterior and lateral lens persists
Does persistent tunica vasculosa lentis cause vision problems?
NO-- it is a very thin, mesh like membrane
What is persistent tunica vasculosa lentis a form of?
Persistent hyperplastic primary vitreous (PHPV)