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

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Presentation on theme: "Glaucoma Workup Review: from A to OCT Dr. Nathan Rains Eye Center of Northern Colorado."— 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: ok/chapter_what_is_glaucoma.html

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

9

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  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? Pachymetry – WHY?

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  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 Pachymetry Pearls

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 Normal angle  Pigmented 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 ophtalmologiste/oct_ou_tomographie_en_coherence_optique.html

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 supplemental/%7Bde06c09a-2d95-42f4-b403-2fc1fa6a3550%7D/clinical-use-of-oct- in-assessing-glaucoma-progression

37 Retinal Nerve Fiber Layer Anatomy Carl Zeiss Webinar Photo – Effective Perimetry  Fibers  Make an arc  Do NOT cross horizontal axis  Temporal raphe  Defects on nerve are opposite on fields

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?  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  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

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, 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

43 Automated Perimetry Glaucoma VF Types  Types  Nasal Step  Arcuate  Paracentral  Severity  Mild to Very Severe understanding-vision-loss.html

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

50 Glaucoma Workup Review  The End! Questions?


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