Lecture 16 (Lecture Capture Only) Flashcards
(13 cards)
What are the characteristics of lens luxation?
-lens is held in place by ciliary zonules
-only way lens can luxate is if the zonules break
-broken zonules allow lens to migrate around the eye
-condition is diagnosed by simply observing the lens out of normal anatomic position
What makes a lens luxation anterior?
if the lens is in front of the iris
What makes a lens luxation posterior?
if the lens is behind the iris
Why does an eye with an anterior lens luxation lack direct and consensual PLRs?
an anteriorly luxated lens fits tightly within the anterior chamber and physically traps the pupil, preventing it from moving in response to the light
What are the potential ways that a lens luxation can raise IOP?
-lens occupies a portion of the iridocorneal angle
-lens is trapped between cornea and iris and abrades both tissues
-lens that is tightly pressed against pupil can cause pupillary block and prevent passage of aqueous from the posterior chamber to the anterior chamber
What causes a dog with a lens luxation to also have primary glaucoma?
-lens luxation is associated with a mutation of the ADAMTS17 gene
-primary glaucoma can occur with mutation of the ADAMTS10 gene, which can have a co-localizing mutation when ADAMTS17 is mutated
Why is corneal edema commonly seen in lens luxation cases?
when the lens is trapped in the anterior chamber it rubs on the corneal endothelium and can cause dysfunction leading to edema
Why is aqueous flare NOT often seen in lens luxation cases despite concurrent uveitis?
the lens occupies the entire anterior chamber, which does not leave enough aqueous depth available to observe aqueous flare
What are the types of lens luxation based on cause?
-primary luxation
-secondary luxation caused by glaucoma
-secondary luxation caused by uveitis
How can a primary lens luxation causing secondary glaucoma be distinguished from a primary glaucoma causing secondary lens luxation?
-primary luxations are typically in predisposed breeds, like terriers
-primary luxations are often anterior
-secondary luxations occur in conjunction with buphthalmia
-secondary luxations are often posterior and considered subluxations
What is the age range for primary hereditary terrier luxation?
between 3 and 6 years of age, with a mean of 4.3 years
What is the “couching” technique?
-alternative to intracapsular lens luxation
-involves shoving the lens into the vitreous body by pressing on it through the cornea
-turns an anterior lens luxation into a posterior lens luxation that is tolerated better
-must use a miotic to encourage lens to remain behind iris
What are the characteristics of a sulcus intraocular lens?
-IOL placed right behind the iris in lens luxation patients that undergo lens extraction surgery
-IOL “haptics” end up lodged where the iris and ciliary processes come together in the “ciliary sulcus”
-IOL has to be sutured to sclera to secure it
