Glaucoma (Plummer) Flashcards
1
Q
Pertinent structures
A
- Ciliary body
- Iridocorneal angle (ICA)
- Retina and optic nerve
2
Q
Gonioscopy
A
- special lens to visualize drainage angle
3
Q
Aqueous production
A
- Active secretion by the non-pigmented ciliary epithelium
- carbonic anhydrase
- Ultrafiltration of plasma
4
Q
Glaucoma def
A
- Group of diseases characterized by altered aqueous humor dynamics
- Elevation of IOP incompatible with health of optic nerve and eye
- CS
- edema of cornea
- depression of optic disc
5
Q
Types of glaucoma
A
- Primary
- congenital
- open angle
- closed angle
- Secondary
- inflammatory
- lens lux
- mechanical/neoplastic
6
Q
Congenital Glaucoma
A
- Usually due to a developmental defect
- failure of rarefaction of drainage apparatus
- May produce profound buphthalmia
- May be inherited
- Usually a ‘fluke’ of development
7
Q
Primary open angle glaucoma
A
- Hereditary disorder in beagle, and others
- Most common form in people
- Normal drainage angle and pectinate muscles but slow increase in IOP…..?
- Open angle will progress to closed angle
8
Q
Primary closed angle glaucoma
A
- most common form in veterinary patients
9
Q
One part of body not covered by epithelial lining
A
- Iris has no anterior epithelium
- makes it sticky: prone to synechia
10
Q
Lens lux is a cause of
A
- cause of secondary glaucoma
11
Q
Glaucoma
DX
A
- Clinical signs
- mydriasis
- scleral injection
- corneal edema
- Index of suspicion
- Tonometry
12
Q
Acute presentation of glaucoma
A
- Ocular pain
- epiphora
- blepharospasm
- ‘headache’
- Increased IOP
- Mydriasis
- Corneal edema
- Episcleral injection
- Visual loss or disturbance
13
Q
Chronic presentation
A
- Permanent vision loss
- optic disc cupping
- retinal degeneration
- Buphthalmia
- Permanent corneal edema
- Striate keratopathy
- Haab’s striae
- Recurrent corneal ulcerations
- Lens lux/sublux
- cataract formation
14
Q
Equine Glaucomas
A
- Mostly secondary to
- uveitis
- ERU
- Primary in the appaloosa
- Tend to maintain vision longer than dogs
15
Q
Feline Glaucomas
A
- Mostly secondary to
- uveitis
- Intraocular neoplasia
- aquous misdirection
- POAG in Siamese and Burmese
16
Q
Tonometry
A
- Via applanation or rebound
- Normal canine and feline IOP
- 15-25
- ideal target is low teens
- can vary with eye/orbit conformation
- brachycephalics higher
- Normal equine IOP
- 23.3 +/- 6.9 mmHg
- must be taken with head held up
- down head can inc up to 87%
*digital tonomotry is not reliable
17
Q
Visual implications of early glaucoma
A
- Narrowing field of vision (peripheral loss)
- chronic and progressive
18
Q
Treatment of glaucoma
A
- Goals of therapy
- treat primary cause
- lower IOP
- decrease prod AqH
- inc outflow of AqH
- Neuroprotection
- Medical
- topical
- systemic
- Surgical
19
Q
Glaucoma
Medical Therapy
A
- Classes of drugs
- Hyperosmotic agents
- Topicals: chronic therapy
- systemics: emergency therapy
- Cholinergic agonists
- a2 adrenergic agonists
- B adrenergic antagonists***
- used a lot
- dec prod of AqH by a small amount
- treat normal eye as well as abnormal eye
- synergism
- Carbonic anhydrase inhibitors***
- Dorzolamide: made at UF (bigger than gatorade)
- Prostaglandin analogues
- cause inc in outflow of aqueous humor
- causes profound miosis: worry about lens luxation
- Hyperosmotic agents
20
Q
Parasympathomimetics
A
- do not use as primary tx for glaucoma
- can use as adjunct I think
- burns
- pH too low
- lowers intraocular pressure by causing profound myosis and uveitis
21
Q
The majority of AqH produced by
A
- Carbonic anhydrase in ciliary epithelium
22
Q
Prophylactic therapy
A
- Essentially all POAG and PCAG are bilateral
- Need to treat normotensive eye to delay onset of ocular hypertension
- b-blocker
- prostaglandin
- miotic
- Mean time to develop glaucoma is 6 mos
- Medical Tx can delay to a mean of 30 mos
23
Q
Glaucoma
Surgical treatment
A
- Gonioshunts***
- Cycloablation***
- Cryotherapy: old school causes lots inflammation
- Laser photocoagulation
- transscleral
- Endoscopic
- Other techniques to inc outflow
- iridenclesis
- cyclodialysis
- corneoscleral trephination/posterior sclerotomy + peripheral iridectomy
24
Q
‘Safe’ IOP
A
- Once optic nerve is damaged, remaining axons more sensitive to further insult
- Lowering IOP to less than normal may be protective of ONH
- Sensitivity of optic nerve to an IOP may change
25
Salvage procedure for glaucoma
* Once vision is lost
* comfort first priority
* enucleation
* evisceration with intraocular prosthesis
* pharmacologic ablation: if not blind will cause blindness
26
Glaucoma take home
* Glaucoma painful and potentially blinding
* Recognize clinical signs
* Is an emergency
* get pressure down ASAP
* mannitol
* Topical prostaglandin
* referral
* Goals of therapy
* maintain vision as long as possible
* keep pressures low enough for comfort
* treat normal eye if primary glaucoma