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Glaucoma Workup Review: from A to OCT

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Presentation on theme: "Glaucoma Workup Review: from A to OCT"— Presentation transcript:

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 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

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?

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