glaucoma ch23
DESCRIPTION
aTRANSCRIPT
Glaucoma
Chapter 23
Role of Technician in Glaucoma
Case historyPerforming pretestingAid in treatmentPreoperative & postoperative care
Glaucoma
76 million worldwide with glaucomaMany more undiagnosed!
Elevated intraocular pressureOptic nerve cuppingVisual field loss
Primary angle-closure glaucoma
~10% of all glc patients5-10% of elderly populationMore common in women because of
shallower ACNormal except anatomically have shallow
angle
Primary angle-closure glaucoma
Which of the following would have a more shallow angle because of typical eye anatomy associated with this condition?MyopiaHyperopiaAstigmatism
Primary angle closure glaucoma
Crowding in the angleIncreases with age
Why? What structure inside the eye physically changes/grows with age?
Less than 20 degrees in width is said to constitute narrow angle glaucoma
How does it happen?
Would dilation or constriction of the pupil cause more crowding in the angle?
What process can’t happen if there’s a bunch of iris tissue crowded into the angle?
How does it happen?
Dilation causes the iris to “bunch up” in the angle
Aqueous humor cannot drainPressure builds up
How does it happen
Usually begins in conditions that dilate the pupilsCan even happen because of dilation during an
eye examination!Medications could cause it
Can become fully developed in 30-60min
Pain
This can be very painfulPatient may be nauseous and vomitCornea clouds up & patient cannot see
Clinical Manifestations
Eyelid, conjunctiva, corneal edemaCornea appears hazy & opaque
IOP is HIGHCan be 50-60mm Hg or higher
Most people have had warning signs, but may not have understood themAche, blur, haloes, rainbowsHaloes usually inner blue-violet & outer yellow-
red ring
Diagnosis
Narrow angle identified in eye exam
Even though pressure may be normal at exam, definitely have to identify narrow angles!
Gonioscopy – the only true way to properly assess the narrowness of the angle
Gonioscopy
Can differentiate between open-angle and narrow-angle glc
TypesGoniolensTwo to four-mirror
lenses
Gonioscopy
What we see through a gonio lens
Ciliary body bandgrayish
Scleral spurWhite line
Trabecular meshworkPigmented
Schwalbe’s line
Gonio view
Treatment
Laser iridotomyDo it bilaterally
50-70% will have attack in other eye!
Allows AC to deepen
Treatment
Must lower pressure first before attempting iridotomy
POAG
Chronic, progressive, bilateralUsually shows up after age 40, but
diagnosed earlier now with our better screening methods
Usually caused by decreased outflow
POAG
Diagnosis usually by results of three conditions1. increased IOP2. optic nerve cupping3. visual field defects
Ocular Hypertension
Have high IOP but no VF or ONH changes
This means they can tolerate higher than normal IOP without damage
But they are a glaucoma suspect because of this, although most will never need meds to treat this
Secondary Glaucoma
Caused by some other factorLens changes/dislocationsScar tissueSynechiaIritisTumorTraumaSteroid use – chronic & high-dose
Congenital Glaucoma
RareInfant may be very light sensitive and tear
a lotCorneal haziness & enlarged
(buphthalmos)
Tonometry
Measure of intraocular pressureMany different ways
Indentation (Schiotz) tonometry
Not used much anymore
Third world countriesAnestheticRests on cornea &
indents itMore indentation =
softer cornea=lower IOP
Applanation Tonometry
Cornea flattenedMore accurateThe standard of measurement
Goldmann Applanation Tonometry
Disadvantage-not portable
Need significant training to accurately perform
Anesthetic + fluorescein + blue light = green reflection
Goldmann Applanation Tonometry
See page 438 for incorrect flourescein bands
IOP
Pressure varies during the dayUsually highest early am (diurnal
variation)
Perkins hand-held applanation tonometerSame principle as
GoldmannIt’s rather bulky
Non-contact Tonometer“Airpuff”Principle of how long it
takes the puff of air to exactly flatten cornea
Takes less time to flatten a soft eye (lower IOP)
Not as accurateCan use with contact
lenses
Tonopen
Portable, hand-held, lightweight
Applanation technique
Optic Disk Evaluation
Cupping + pallor (color-pale)
Center depression is the cup
The fibers around the edges are the rim
Glaucoma cupping - asymmetric
Heidelberg Retina Tomograph
3-D topographic map of ONH
GDx VCC
Looks at the nerve fiber layer
Printout give color-coded picture showing thickness of NFL
Optical Coherence Tomographer OCTCross section of
retinaCan show macular
thickness, retinal NFL thickness and view optic nerve
Compare values over time
Visual Field
Usually VF defects correspond to appearance of damage to optic disk
Visual Field Defects
Enlarged blind spotNerve fiber bundle defectBjerrum’s scotomaNasal depression or nasal step
Last place is central vision
Types of Perimetry
KineticMove object from
nonseeing area to a seeing area
Goldmann
Static Uses stationary test
objects presented randomly
Threshold static perimetryChange intensity of
lightHumphrey
Treatment
No cure but can be controlled in many casesCompliance
Reduction of IOP is principal goal
Treatment
Eye dropsMany types & newer formulationsSide effects
Eyedrops
MioticsPilocarpineCan interfere with vision
SympathomimeticsPropine
Beta blockersTimoptic (timolol)Still used a lot
Eyedrops
Carbonic anhydrase inhibitorsOral – closed angleDrops now available
ProstaglandinsLumigan, xalatan
Alpha agonistsalphagan
Eyedrops
HyperosmoticAngle closure & surgeryMany side effects
Compliance
20-40% of patients miss dosagesDon’t feel “sick” so don’t take medsCostPick meds with fewer doses per day
Other treatments
Argon laser trabeculoplasty (ALT)Laser holes into trabecular meshwork
Selective laser trabeculoplasty (SLT)Less thermal than ALT so less scarring
Excimer laser trabeculostomy (ELT)Least damage Waiting FDA approval
Surgery
Create an opening between anterior chamber and subconjunctival space
With or without implant (tube shunt)Post-op care is criticalHypotony, wound leak, fluid shifts,
infection