Len disease (other than cataracts) Flashcards by M C

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.

Poor prognosis

How well did you know this?

Not at all

Perfectly

What are common causes of septic lens implantation syndrome?

Cat scratch (#1) or phacoemulsification

How well did you know this?

Not at all

Perfectly

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)

How well did you know this?

Not at all

Perfectly

What is the difference between phacolytic and phacoclastic uveitis? Include CAUSE and SEVERITY.

Phacoclastic uveitis:

traumatic lens capsule rupture
sudden exposure of T cells to protein
severe, requires surgery (phaco) to avoid loss of globe

Phacolytic uveitis:

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

How well did you know this?

Not at all

Perfectly

What is the main issue with microphakia?

May increase risk of luxation

How well did you know this?

Not at all

Perfectly

What 2 conditions is microphakia possibly associated with?

Spherophakia

2. Microphthalmos (small globe)

How well did you know this?

Not at all

Perfectly

What is lenticonus?

A cone-shaped defect on one aspect of the lens (like a pimple on the lens)

How well did you know this?

Not at all

Perfectly

Where on the lens does lenticonus usually occur?

The posterior pole of the lens

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

What breeds have an inherited increased likelihood to lens luxation?

Border Collie

Terriers: Cairn, Jack Russell, Lakeland, Manchester, Miniature Bull, Norfolk, Norwich, Scottish, Skye, Sealyham, Smoothhaired Fox, Westie, Tibetan, Wirehaired Fox

How well did you know this?

Not at all

Perfectly

Lens luxation and glaucoma– explain chicken or egg?

Glaucoma –> buphthalmia –> stretch zonules –> luxation

Luxation –> secondary glaucoma

How well did you know this?

Not at all

Perfectly

How can luxation or subluxation lead to glaucoma? (4 ways)

Entrapment of lens in anterior chamber (angle closure and/or pupil block)
Synechiae with iris bombe (pupil block)
Anterior vitreous prolapse (pupil block)
Inflammation within anterior segment, causing low-grade trauma to iris and ciliary body –> release of melanin –> inflammation and glaucoma

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

In the dog, how can anterior lens luxation present (in regard to cornea)?

Corneal edema

How well did you know this?

Not at all

Perfectly

What age do you start to see the ring formed in the lens indicating earliest nuclear sclerosis?

6 years

How well did you know this?

Not at all

Perfectly

How much of the lens is affected with lenticular sclerosis?

The nucleus only… hence also being called nuclear sclerosis

How well did you know this?

Not at all

Perfectly

What are the common signs that a dog is having difficulty seeing from lenticular sclerosis?

Hesitating going DOWN stairs
Hesitating going into a dark room
Bobbing head when food is dropped

How well did you know this?

Not at all

Perfectly

What are 6 causes of SECONDARY lens luxation in dogs?

Glaucoma
Chronic uveitis
Trauma
Age
Neoplasia
Hypermature cataract as they shrink

How well did you know this?

Not at all

Perfectly

Aphakia causes what change in vision (in D)?

+15D (THICK glasses)

How well did you know this?

Not at all

Perfectly

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)

How well did you know this?

Not at all

Perfectly

What is pseudophakia

An implanted intraocular lens

How well did you know this?

Not at all

Perfectly

Where does the lens sit (structure)

Patellar fossa or hyaloid fossa (depression in vitreous)

How well did you know this?

Not at all

Perfectly

What is pathognomic for lens subluxation

Aphakic crescent

How well did you know this?

Not at all

Perfectly

When are mydriatic agents appropriate for lens luxation (3)?

Couching procedure
Pupillary block
Post-lensectomy to prevent synechiae, improve comfort, and stabilize lens-ocular barrier

How well did you know this?

Not at all

Perfectly

What tends to cause lens luxation in cats?

Inflammation

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?

Equator

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)

2 main ways to get phacoclastic uveitis?

1. diabetics | 2. corneal laceration with lens involvement

What part of the lens capsule is thinnest? Why?

Posterior lens capsule: no epithelium to add to it, so made during development and not contributed to after birth

What happens to the shape of the lens when you want to see near objects?

It gets rounder

What is your vision like if you are aphakic?

Extremely hyperopic (far-sighted)

What is a PCO?

Posterior capsular opacity

What gene is associated with primary lens luxation?

ADAMTS17

Can a perforating trauma (cat claw) lead to lens luxation?

How to cataracts lead to lens luxation? (2 ways)

Zonules may stretch/break if 1) becomes intumescent or 2) crenated (with resorption)

What sign, associated with the posterior segment, can indicate early zonule disruption?

Vitreous through pupil into anterior chamber

Explain syneresis associated with lens luxation

Increased movement of lens causes anterior vitreous cortex to separate from central vitreous, damages vitreous, which liquifies

What are 3 ways lens luxation can lead to glaucoma, OTHER THAN the lens itself sitting in the anterior chamber blocking the drainage angle

1. No barrier to vitreous going into anterior chamber 2. Lens in posterior chamber may push iris into drainage angle from behind 3. As zonule fibers tear, reduced centripetal pressure on ciliary body, so there is collapse of ciliary cleft and impeded outflow

How does lens luxation lead to uveitis? (2 ways)

1. lens touching structures (esp cornea) | 2. if lens becomes cataractous and leads to LIU

Corneal edema secondary to lens luxation-- permanent?

It can be if enough damage is done to endothelial cells

Why can retinal detachment occur with lens luxation?

Vitreous moves anteriorly (this can happen with posterior luxations, too!!), and pull sensory neuroretina off

What is the main issue with extraction of a luxated lens?

Glaucoma

What is one was to help prevent the primary post-op complication seen with lens extraction?

Partial anterior vitrectomy

If intracapsular lens removal is performed, and there is sulcus lens replacement, what is the likelihood of vision post-op?

14/20 eyes

Why is IOL placement recommended with lens removal?

To act as a barrier to vitreous, plus better vision

What does sedation do to help couching?

Reduces globe tension from extra ocular mm

In a patient with unilateral lens lux, what 2 things should be looked for/performed in the contralateral eye?

1. Biomicroscopy to look for evidence of lens luxation | 2. Gonioscopy

Len disease (other than cataracts) Flashcards

(61 cards)