BCSC 10. Glaucoma Flashcards
Critical risk factors for progression of POAG
DECREASED PERFUSION PRESSURE, thin cornea, increasing age. Intracranial pressure not studied. Low ICP implicated in low-tension glaucoma.
Inheritance of axenfeld-rieger syndrome
AUTOSOMAL DOMINANT
Outflow facility is measured by
tonography
Measures aqueous humor formation rate
fluorophotometry
Measures episcleral venous pressure
venomanometry
Must be calculated using goldman equation and parameters IOP, aqueous humor flow rate, outflow facility, and episcleral venous pressure
Uveoscleral outflow rate
Rate of aqueous humor formation during sleep
decreases 50%. Normal 2-3uL/min
Tonometer uses Imbert-Fick principle for measurement of IOP
Goldmann and Perkins tonometer - use same measurement tip, balances surface tension of tear film with rigidity of cornea to approximate dry infinitely flexible thin walled sphere for eyes with corneal thickness of 520 um
Imbert-Fick principle
relates pressure inside a dry, thin-walled sphere to the force required to flatten a specific area
Force goldmann applanation tonometer measures
Force necessary to flatten an area of the cornea of 3.06 mm in diameter
How was a visual field defect defined on standard automated perimetry in the OHTS
presence of a Pattern Standard Deviation (PSD) with P < 5% or presence of a Glaucoma Hemifield Test (GHT) with a result outside normal limits. Had to be present in 3 consecutive visual field tests
Mutations in which gene are associated with pseudoexfoliation syndrome?
LOXL1 mutation at 15q24 (Scandanavians like lox)
Gene mutation in primary congenital glaucoma
CYP1B1
Gene mutation in iridogoniodysgenesis
FOXC1
Gene mutation in Rieger syndrome
PITX2
m/c cause of glaucoma associated with primary or metastatic tumors of the ciliary body
DIRECT INVASION of the anterior chamber angle
Glaucoma caused by leakage of lens protein through the capsule of a mature or hypermature cataract
Phacolytic glaucoma - phagocytizing macrophages obstruct TM
Glaucoma caused when lens cortex particles obstruct TM following disruption of lens capsule with cataract extraction or trauma
Lens particle glaucoma
Glaucoma caused by large intumescent lens induces angle-closure (ACG)
Phacomorphic glaucoma
Displacement of lens from its normal anatomical position
Ectopia lentis
WDR36
Adult POAG
OPTN
NTG, adult POAG
TIGR/MYOC
JOAG and adult POAG
Inheritance of Congenital glaucoma
Recessive
Goldmann equation
Po = (F-U)/C+Pv Po = IOP in mm Hg F = rate of aqueous formation in uL/min U = rate of aqueous humor drainage through pressure insensitive uveoscleral pathway (uL/min) C = outflow facility Pv = episcleral venous pressure in mm Hg
Resistance to outflow (R) is equal to
inverse of facility of outflow
Aqueous humor composition
XS Hydrogen, chloride, ascorbate, deficit of bicarb, protein free (1/200-1/500).
GF, enzymes: carbonic anhydrase, lysozyme, diamine oxidase, plasminogen activator, dopamine beta-hydroxylase, phospholipase A2, prostaglandins, cyclic adenosine monophosphate, catecholamines, steroid hormones, hyaluronic acid
Bilateral angle closure glaucoma in eyes with normal axial length
Uveal effusions due to systemic medication - m/c topiramate
Laser iridotomy useful for
pupillary block (phacomorphic glaucoma)
Patients with appositional angle closure or areas of peripheral anterior synechiae with relative pupillary block are at risk for chronic angle closure developing should have this treatment
laser iridotomy
Elevation of IOP independent of pupillary block may occur despite a patent iridotomy
Plateau iris syndrome
Type of glaucoma unlikely to resolve after cataract extraction
Eye with angle recession and phacodenesis after blunt trauma
Abnormal spherical shape of lens induces pupillary block
microspherophakia
Finding in congenital glaucoma can continue to change and indicate progression even though IOP appears to be controlled
AXIAL LENGTH
After successful surgery for congenital glaucoma, how many years should child be monitored
Lifetime
Post-op complications in congenital glaucoma
amblyopia, strabismus, corneal decompensation, cataracts
Glaucoma medication contraindicated in toddlers
Brimonidine - systemic hypotension and apnea in children younger than 2 years old. Relative contraindication in older children
Class of ocular hypotensive agents associated with the development of apnea in infants and young children
alpha 2-Selective adrenergic agonists reported to cause systemic hypotension, apnea, CNS depression, bradycardia. May cross blood-brain barrier. Avoid in nursing mothers.
Only topical ocular hypotensive beta-blocker that is relatively beta-1 selective
Betaxolol
Nonselective beta-adrenergic antagonists (beta-blockers) topical ocular hypotensive agents
Timolol, carteolol, levobunolol (may result in bronchospasm)
Conditions associated with increased risk of suprachoroidal hemorrhagw
High myopia, aphakia or pseudophakia, hypotony, prior vitrectomy, advanced age, systemic hypertension, anticoagulant therapy, h/o suprachoroidal hemorrhage in fellow eye.
Fluorouracil Filtering Surgery Study found that risk of suprachoroidal hemorrhage was strongly associated with
(1) level of preoperative IOP and (2) magnitude of IOP reduction. Reduce IOP as much as possible before filtering surgery and decreasing magnitude of immediate IOP reduction through releasable sutures or laser suture lysis can reduce risk.
5 years after laser trabeculoplasty, what percentage of treated patients are expected to maintain lower IOP
50%
Best candidate for a trabeculectomy with mitomycin C
Patient with previous failed trabeculectomy without antifibrotics
Patient with neovascular glaucoma is candidate for which GL procedure
Tube shunt (trabeculectomy success rate lowered with inflammation)
Patient with active uveitis or neovascular glaucoma is good candidate for which GL tx
Tube shunt (trabeculectomy success rate lowered with inflammation)
Risk factor for bleb related infections
contact lens wear
Patient with most success with laser trabeculoplasty (LTP)
IOP needs to be lowered but patient can’t tolerate multiple medications. Contraindicated in uveitic glaucoma.
LTP less effective in which patients
Less effective in aphakic and pseudophakic than in phakic patients. Small central island of vision is at risk of vision loss if significant IOP spike
Consider tube shunt in following clinical settings
Failed trabeculectomy with antifibrotics Active uveitis Neovascular glaucoma Inadequate conjunctiva Aphakia CL use
