glaucoma ch23

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