Transcript Glaucoma Workup Review: From A to OCT By: Nathan Rains, OD

Glaucoma Workup
Review: from A to
OCT
Dr. Nathan Rains
Eye Center of Northern Colorado
What is Glaucoma?

3 million Americans have glaucoma

One of the leading causes of adult blindness

No symptoms until extensive peripheral vision loss (for
most types of glaucoma)


“sneak thief of sight”
Chronic condition, no cure, just control

Control is lower eye pressures by

Eye drops, laser surgeries, or medical surgeries
What is Glaucoma?
Prevalence
http://www.nei.nih.gov/eyedata/glaucoma.asp#1
What is Glaucoma?
Definition
... optic neuropathy with associated visual function loss,
with intraocular pressure (IOP) being one of the primary
risk factors...

American Academy of Ophthalmology
Optic Neuropathy?
Pic 1:
http://www.hopkinsmedicine.org/wilmer/glaucoma_center_excellence/bo
ok/chapter_what_is_glaucoma.html
Optic Neuropathy?
http://www.cehjournal.org/article/the-optic-nerve-head-in-glaucoma/
Goals of Glaucoma Testing

The ultimate goal of glaucoma testing is three
fold:



To Diagnose Glaucoma (probably the hardest step)

Is the test RELIABLE

Is the test REPEATABLE
To Determine its Severity

Suspect, mild, moderate, severe

Initiate treatment, set appropriate target pressures, etc.
To Monitor Progression
Glaucoma Testing

Tonometry

Pachymetry

Gonioscopy

Tomography

Perimetry

*Biomicroscopy

*Photography

*Corneal Hysteresis

*Ganglion Cell Complex
What is Tonometry?

The measurement of intraocular pressure (IOP) recorded
in mmHg

Normal IOP – 10-20 mmHg (avg ~ 16mmHg)


Diurnal fluctuations – 4-6 mmHg


>4-6 is suspicious
Only treatable measure of glaucoma


Pressure is highest at night, in the supine position (3 am)
Difference between eyes – 2-3 mmHg


Ocular hypertension - >20-22mmHg
All medicine and surgery is geared to this one task, lower IOP
Tested at every examination and followup care
Diurnal Variation
http://www.eyecalcs.com/DWAN/pages/v3/v3c046.html
How is Tonometry Measured
Digital Palpation
Tonometry Instruments
Indentation – iCare & Tonopen
http://www.icaretonometer.com/rebound-technology/
Good 38 sec video
Tonometry Instruments
Non-Contact Tonometry


Advantages

No anesthesia

*No contact

Ease of use

Quick
Disadvantages

Patients 'love' to hate this test

Accuracy?
Tonometry Instruments
Goldmann Applanation Tonometry


Gold standard

Accurate

Inexpensive

easy to use
Disadvantages

Anesthesia

still dependent on corneal properties
Tonometry Instruments
Take homes

Digital


Indentation


portable, cheap, supine
Non-contact tonometry


basic, only detects extremely high pressures
expensive machine, touchless, quick, patient discomfort
Applanation

gold standard, inexpensive, easy to use, less variability
Pachymetry
What is Pachymetry?

The measurement of corneal thickness, in
microns (um)

Average CENTRAL corneal thickness ~ 555 um

In glaucoma, used as a risk factor in the
development of glaucoma

Ocular Hypertensive Treatment Study (OHTS)

CCT <555, high risk

CCT 555-585 no increased risk

CCT >585 low risk
Pachymetry and IOP
correction table?


Theory

The thicker the cornea, the artificially high reading

The thinner the cornea, the artificially low reading
IOP correction table?

1975 study

Every 100um adjust by 7mmHg

17 other studies, all different IOP per 100um
adjustment… no consensus

Reason

Thickness of cornea is only one part of it:

Corneal properties (steep/flat, hysteresis
(stiffness), etc.)
Pachymetry Pearls

Center of cornea

Compare symmetry (>30, repeat)

LASIK/PRK?

Diseased Corneas?

Fuchs, keratoconus?

Used as a RISK factor

No universal agreement on IOP correction table to
use

So, we do NOT adjust IOP measurement
Goals of Glaucoma Testing

The ultimate goal of glaucoma testing is three
fold:



To Diagnose Glaucoma (probably the hardest step)

Is the test RELIABLE

Is the test REPEATABLE
To Determine its Severity

Suspect, mild, moderate, severe

Initiate treatment, set appropriate target pressures, etc.
To Monitor Progression
What is Glaucoma?
By Type

Primary Open Angle Glaucoma

Acute Angle Closure Glaucoma

Pseudoexfoliative Glaucoma

Pigmentary Glaucoma

Normal/Low Tension Glaucoma

Neovascular Glaucoma

Congenital Glaucoma

Traumatic Glaucoma

Secondary Glaucoma

And more… over 60 types...
Gonioscopy

Obtain a view of the
drainage angle formed
between the eye’s
cornea and iris

Aids in diagnosis and
monitoring of glaucoma

Performed under slit
lamp, with a gonio lens

Used in laser treatment
of the angle (SLT –
selective laser
trabeculoplasty)
Gonioscopy
Gonioscopy.org Video Clip
Can’t See That Stupid Line

Normal angle

Pigmented Angle
http://www.academy.org.uk/tutorials/gongrade.jpg
Anterior Segment OCT
http://www.iovs.org/content/52/5/2095/F1.expansion.html
Gonioscopy
Take home

Helps diagnose and determine type of glaucoma

Check out gonioscopy.org
Glaucoma Testing

Tonometry

Pachymetry

Gonioscopy

Tomography

Perimetry

*Biomicroscopy

*Photography

*Corneal Hysteresis

*Ganglion Cell Complex
Optic Neuropathy?
http://www.cehjournal.org/article/the-optic-nerve-head-in-glaucoma/
Optical Coherence
Tomography

Non-invasive, high resolution, imaging technology

Time Domain vs Spectral Domain


TD – 400 scans per sec, 10um

SD – 20,000-40,000 per sec, 3um

3-D reconstructions

AWESOME!
Scan types

Retinal (macular)

Optic Disc
http://www.docvadis.fr/aobeffroi/page/l_oeil_et_les_examens/les_machines_utilisees_par_l_
ophtalmologiste/oct_ou_tomographie_en_coherence_optique.html
OCT Optic Disc

Scans the optic disc using a 6mm cube

Obtains Retinal Nerve Fiber Layer Thickness

Color codes a thickness map

‘hour glass’ appearance


Red (350um), to blue (0um)
Normative table

RNFL thickness

Symmetry

C/D ratio

Etc.

RNFL TSNIT Map

Quadrant and Clock Hour RNFL thickness chart
Normal OCT
OCT Optic Disc
Diagnosing Glaucoma

Average RNFL

Symmetry


Quadrant RNFL layout


Inferior and Superior are the greatest indicators
Clock Hour RNFL layout


>20um difference is statistically significant
Inferior temp and/or superior temp thin
Lastly – does it correlate with the visual field

***structural loss precedes VF loss***
OCT optic disc
Example
OCT Optic Disc
Monitoring Glaucoma

Average NFL

Symmetry

Progression Analysis
http://www.healio.com/ophthalmology/journals/osli/2011-7-42-4supplemental/%7Bde06c09a-2d95-42f4-b403-2fc1fa6a3550%7D/clinical-use-of-octin-assessing-glaucoma-progression
Retinal Nerve Fiber Layer
Anatomy

Fibers

Make an arc

Do NOT cross horizontal axis


Temporal raphe
Defects on nerve are
opposite on fields
Carl Zeiss Webinar Photo – Effective Perimetry
Perimetry
Automated Visual Field

Automated Perimetry for Glaucoma

Types of tests used


30-2, 24-2, and 10-2
Strategies used

SITA Standard, SITA Fast
Visual Field

Types: 30-2, 24-2, 10-2
 1st number refers to the degrees AROUND
fixation

 2nd
Ex: 10-2 – 10 degrees around the fovea (20 degrees total)
number refers to the protocol

Protocol 1 – points directly on the horiz and vert axis

Protocol 2 – points directly above and below axis

 Points
Easier to interpret and used exclusively now
tested
30-2 – 6 degrees apart, total points 76, ~8 min per eye
24-2 – 6 degrees apart, total points 54, ~5 min per eye
10-2 – 2 degrees apart, total points 54
30-2 vs 24-2?
 24-2
advantages
 Faster
time (~5 min per eye)
 Less variable
 Similar results
 30-2
advantages
 More
 May
degrees of field tested
help detect/monitor
neurological defects, ie. Idiopathic
intracranial hypertension
SITA Standard vs SITA Fast


SITA Standard

Best threshold test

Better for early detection in glaucoma

More reliable, more sensitive
SITA Fast

Fast(er)

Can be used for screening purposes

More Variable, less sensitive (underestimates) scotomas
When to use 10-2 in Glaucoma?
 Previously,
used exclusively in severe
peripheral field loss
 24-2
not providing enough information to
monitor progression, so 10-2 replaces 24-2
 Recently,
published in the JAMA
Ophthalmology, January 2014, 10-2
VF testing was found to detect early
glaucomatous defects missed on 24-2
 Of
22 eyes tested as normal on 24-2 testing,
22.7% were abnormal in 10-2 testing
 May use 10-2 in addition to 24-2
Automated Perimetry
Glaucoma VF Types


Types

Nasal Step

Arcuate

Paracentral
Severity

Mild to Very Severe
http://www.medrounds.org/glaucoma-guide/2006/02/section-1-cunderstanding-vision-loss.html
Visual Field
Diagnosing Glaucoma

Reliability


Fixation losses, false positive, false negatives, etc.
Repeatability

When there’s a defect, is it repeatable?


Three consecutive fields to reliably confirm glaucoma*
Global Indices

GHT – glaucoma hemifield test

MD – Mean Deviation

PSD – Pattern Standard Deviation

VFI – Visual Field Index (percentage)
*Keltner et al. for the Ocular Hypertenstion Treatment Study Group,
Arch Ophthalmol 123:1201 (2005)
Normal Visual Field
Visual Field - Glaucoma
Visual Field - Monitoring
Progression
Visual Field/OCT Integration
Visual Field/OCT Integration
Glaucoma Workup Review

The End! Questions?