1. Glaucoma Workup Review: from A to OCT
Dr. Nathan Rains
Eye Center of Northern Colorado

2. 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

3. What is Glaucoma? Prevalence

4. 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

5. Optic Neuropathy?
Pic 1:

6. Optic Neuropathy?

7. 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

8. Glaucoma Testing Tonometry Pachymetry Gonioscopy Tomography Perimetry
*Biomicroscopy
*Photography
*Corneal Hysteresis
*Ganglion Cell Complex

10. What is Tonometry?
The measurement of intraocular pressure (IOP) recorded in mmHg
Normal IOP – mmHg (avg ~ 16mmHg)
Ocular hypertension - >20-22mmHg
Diurnal fluctuations – 4-6 mmHg
Pressure is highest at night, in the supine position (3 am)
Difference between eyes – 2-3 mmHg
>4-6 is suspicious
Only treatable measure of glaucoma
All medicine and surgery is geared to this one task, lower IOP
Tested at every examination and followup care

11. Diurnal Variation

12. How is Tonometry Measured Digital Palpation

13. Tonometry Instruments Indentation – iCare & Tonopen
Good 38 sec video

14. Tonometry Instruments Non-Contact Tonometry
Advantages
No anesthesia
*No contact
Ease of use
Quick
Disadvantages
Patients 'love' to hate this test
Accuracy?

15. Tonometry Instruments Goldmann Applanation Tonometry
Gold standard
Accurate
Inexpensive
easy to use
Disadvantages
Anesthesia
still dependent on corneal properties

16. Tonometry Instruments
Take homes
Digital
basic, only detects extremely high pressures
Indentation
portable, cheap, supine
Non-contact tonometry
expensive machine, touchless, quick, patient discomfort
Applanation
gold standard, inexpensive, easy to use, less variability

17. Pachymetry

18. 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 no increased risk
CCT >585 low risk

19. Pachymetry – WHY? Concept of applanation tonometry
the cornea is flattened of known size, and the goldmann device is machine is calibrated based on a corneal thickness assumption of 520 um
- So, what if the cornea is thicker, or thinner? What are the pressures? How do they differ?

20. 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.)

21. Pachymetry Pearls Center of cornea Used as a RISK factor
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

22. 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

23. 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...

24. 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)

25. Gonioscopy

26. Gonioscopy.org Video Clip
Can’t See That Stupid Line
Normal angle
Pigmented Angle

27. Anterior Segment OCT

28. Gonioscopy Take home Helps diagnose and determine type of glaucoma
Check out gonioscopy.org

29. Glaucoma Testing Tonometry Pachymetry Gonioscopy Tomography Perimetry
*Biomicroscopy
*Photography
*Corneal Hysteresis
*Ganglion Cell Complex

30. Optic Neuropathy?

31. 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

32. 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

33. Normal OCT

34. OCT Optic Disc Diagnosing Glaucoma
Average RNFL
Symmetry
>20um difference is statistically significant
Quadrant RNFL layout
Inferior and Superior are the greatest indicators
Clock Hour RNFL layout
Inferior temp and/or superior temp thin
Lastly – does it correlate with the visual field
***structural loss precedes VF loss***

35. OCT optic disc Example

36. OCT Optic Disc Monitoring Glaucoma
Average NFL
Symmetry
Progression Analysis

37. 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

38. 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

39. Visual Field Types: 30-2, 24-2, 10-2
1st number refers to the degrees AROUND fixation
Ex: 10-2 – 10 degrees around the fovea (20 degrees total)
2nd number refers to the protocol
Protocol 1 – points directly on the horiz and vert axis
Protocol 2 – points directly above and below axis
Easier to interpret and used exclusively now
Points 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

40. 30-2 vs 24-2? 30-2 advantages 24-2 advantages
Faster time (~5 min per eye)
Less variable
Similar results
30-2 advantages
More degrees of field tested
May help detect/monitor neurological defects, ie. Idiopathic intracranial hypertension

41. SITA Standard vs SITA Fast
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

42. 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, 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

43. Automated Perimetry Glaucoma VF Types
Nasal Step
Arcuate
Paracentral
Severity
Mild to Very Severe

44. 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)

45. Normal Visual Field

46. Visual Field - Glaucoma

47. Visual Field - Monitoring Progression

48. Visual Field/OCT Integration

49. Visual Field/OCT Integration

50. Glaucoma Workup Review
The End! Questions?