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Glaucoma Screening
1. Glaucoma Screening
Nicholas J. Silvestros, OD
Clinical Instructor
Department of Ophthalmology and Vision Sciences
Washington University St. Louis
School of Medicine
2. Causes of Visual Impairment in
the World
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3. Glaucoma
• 2nd most common cause of blindness in U.S.
• Single most common cause of blindness in
African Americans
• African Americans 4x more likely to have glaucoma
and 6x more likely to be blind from it
• If detected early and treated, blindness can be
prevented
• In early stages, most patients asymptomatic
• Peripheral vision can be lost before patient notices
visual impairment
5. Aqueous Flow
• Ciliary body
• Produces aqueous
(fluid in the eye)
• Trabecular
meshwork
• Drains aqueous
fluid out of eye
6. Aqueous Humor Formation
• Involves the combination of 2 known
processes:
• Active transport (secretion)
• 80% of Aqueous
• Passive transport (ultrafiltration and diffusion)
• 20% of Aqueous
• Affected by topical glaucoma medications: beta-
blockers, sympathomimetics and carbonic
anhydrase inhibitors
9. Aqueous Humor Trivia
• Nourishes lens, cornea, vitreous
• Decreases production with:
• Sleep
• Age
• Some systemic hypotensive agents
• Decrease outflow with:
• Age
10. Intraocular Pressure
• IOP:
• Range 11 mmHg to 21 mmHG
• 21 considered upper limit of normal
• IOP varies time of day, heart beat, BP,
respiration
• Tendency for higher AM and lower evening
• Lower during laying/sleeping
• Diurnal variation:
• 2-6 mm Hg normal
• >10 mm Hg suggestive of glaucoma
11. Intraocular Pressure
• IOP:
• IOP varies time of day, heart beat, BP,
respiration
• Tendency for higher AM and lower evening
• Lower during laying/sleeping
• Age (increases with age)
• Caffeine (transiently increases in IOP)
• Alcohol (transiently in IOP)
• Cannibis (mild in IOP)
12. Intraocular Pressure Trivia
• IOP:
• No absolutes
• A “normal” IOP reading may be misleading and
additional reading at different times of the day may
be required
• IOP is a risk factor and does not eliminate glaucoma
if a “normal” reading is recorded
• Must be compared with all other risk factors and
clinical data
13. Measurement of IOP
• Applanation Tonometry:
• Measures the force necessary to flatten an area
of cornea 3.06 mm diameter
• Central part of cornea flattened while variable
force records pressure
• Central Corneal Thickness:
• >540 micrometers produce falsely high IOP
readings by TA
• <540 micrometers produce falsely low IOP reading
by TA
15. Measurement of IOP
• Applanation Tonometry:
• Goldmann tonometer
• Most popular tonometer and accurate tonometer
• Tono-Pen tonometer
• Hand held portable tonometer
• Over estimates low IOP and underestimates high
IOP
16. Measurement of IOP
• Non-Contact Tonometry:
• Air-Puff tonometer
• Goldmann principles with air instead of prism
time required to flatten cornea relates directly to level of
IOP
• Does not require topical anesthetic
• Useful for screenings
• Disadvantage – accurate low to mid IOP range
20. Falsely elevated IOP readings
• Elevated:
• Squeezing of the eyelids
• Breath holding or valsalva maneuvers
• External pressure on the globe
• Thick or scarred corneas
• Marked astigmatism
• Lower:
• Thin corneas
• Marked astigmatism
21. Optic Nerve Head
• 1.2 million axons
• Declines with age
• Cell bodies are the ganglion cells
• Magnocellular (M) cells 10%
• Large diameter (dim illumination)
• Parvocellular (P) cells 90%
• Small diameter axons (color, fine detail)
22. Optic Nerve Head
• Scleral Canal
• Lamina Cribrosa
• Optic Cup
• Neuroretinal Rim
• Size of ON:
• AA>Asians>Hispanics>Whites
24. Optic Nerve Head
• Cup-Disc Ratio
• Fraction of vertical and horizontal meridians
• C/D=0.3/0.3
• Normal is 0.3 or less
• Ratio greater than 0.7 regarded suspicious
• Asymmetry between two eyes of 0.2 or more
regarded suspicious
• Cup size is needed to evaluate progression not
initial diagnosis
25. Optic nerve appearance in glaucoma
• Glaucoma nerve damage ranges from
localized to diffuse
• Localized easier to recognize with notching
• Description of nerve important
• Neuralretinal rim tissue
• Thickness
• Symmetry
• Color
• Notching
• Hemorrhage disc margin
Cataract leading cause of visual impairment in the world. ARMD leading cause of irreversible blindness in Caucasians and glaucoma is the leading cause of blindness in AA and Hispanics in the U.S.
Let’s now look at the anatomy of the eye to better understand the diseases and age-related changes which occur in the eye.
Glaucoma is a problem with drainage of aqueous through the TM resulting in increased IOP and….damage to the optic nerve.
AH formed by the inner nonpigmented
TM (uveoscleral, corneosclera, juxtacanalicular), schlemm’s canal, collector channels,aquous veins, episclearal or conj veins, santerior ciliary and superior ophthalmic veins and cavernous sinus
Let’s now look at the anatomy of the eye to better understand the diseases and age-related changes which occur in the eye.
Rate of formation and outflow facility decline with age!
Rate of formation and outflow facility decline with age!
Rate of formation and outflow facility decline with age!
Rate of formation and outflow facility decline with age!
Perkins- portable Golmann Non-contact – air puff
Perkins- portable Golmann Non-contact – air puff
Perkins- portable Golmann Non-contact – air puff
Perkins- portable Golmann Non-contact – air puff
Let’s now look at the anatomy of the eye to better understand the diseases and age-related changes which occur in the eye.
Let’s now look at the anatomy of the eye to better understand the diseases and age-related changes which occur in the eye.
Let’s now look at the anatomy of the eye to better understand the diseases and age-related changes which occur in the eye.
Digital external pressure by examiner Restricted myopathy (thyroid) – >6 mm Hg elevation in IOP in upgaze
So normal on is slightly vertically oval
Hopewell – c/d OS
So normal on is slightly vertically oval
Let’s now look at the anatomy of the eye to better understand the diseases and age-related changes which occur in the eye.
Let’s now look at the anatomy of the eye to better understand the diseases and age-related changes which occur in the eye.
Let’s now look at the anatomy of the eye to better understand the diseases and age-related changes which occur in the eye.
Nerve fiber layers affecting peripheral vision damaged early
Let’s now look at the anatomy of the eye to better understand the diseases and age-related changes which occur in the eye.
Let’s now look at the anatomy of the eye to better understand the diseases and age-related changes which occur in the eye.
