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Glaucoma W orkup R eview: from A to OCT

Glaucoma W orkup R eview: 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)

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Glaucoma W orkup R eview: from A to OCT

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  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 http://www.nei.nih.gov/eyedata/glaucoma.asp#1

  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: http://www.hopkinsmedicine.org/wilmer/glaucoma_center_excellence/book/chapter_what_is_glaucoma.html

  6. Optic Neuropathy? http://www.cehjournal.org/article/the-optic-nerve-head-in-glaucoma/

  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. What is Tonometry? • The measurement of intraocular pressure (IOP) recorded in mmHg • Normal IOP – 10-20 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

  10. Diurnal Variation http://www.eyecalcs.com/DWAN/pages/v3/v3c046.html

  11. How is Tonometry MeasuredDigital Palpation

  12. Tonometry InstrumentsIndentation – iCare& Tonopen http://www.icaretonometer.com/rebound-technology/ Good 38 sec video

  13. Tonometry InstrumentsNon-Contact Tonometry • Advantages • No anesthesia • *No contact • Ease of use • Quick • Disadvantages • Patients 'love' to hate this test • Accuracy?

  14. Tonometry Instruments GoldmannApplanation Tonometry • Gold standard • Accurate • Inexpensive • easy to use • Disadvantages • Anesthesia • still dependent on corneal properties

  15. 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

  16. Pachymetry

  17. 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

  18. 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.)

  19. 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

  20. 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

  21. 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...

  22. 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)

  23. Gonioscopy

  24. Gonioscopy.org Video Clip Can’t See That Stupid Line • Normal angle • Pigmented Angle http://www.academy.org.uk/tutorials/gongrade.jpg

  25. Anterior Segment OCT http://www.iovs.org/content/52/5/2095/F1.expansion.html

  26. GonioscopyTake home • Helps diagnose and determine type of glaucoma • Check out gonioscopy.org

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

  28. Optic Neuropathy? http://www.cehjournal.org/article/the-optic-nerve-head-in-glaucoma/

  29. 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

  30. 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

  31. Normal OCT

  32. OCT Optic DiscDiagnosing 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***

  33. OCT optic discExample

  34. OCT Optic DiscMonitoring Glaucoma http://www.healio.com/ophthalmology/journals/osli/2011-7-42-4-supplemental/%7Bde06c09a-2d95-42f4-b403-2fc1fa6a3550%7D/clinical-use-of-oct-in-assessing-glaucoma-progression • Average NFL • Symmetry • Progression Analysis

  35. 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

  36. PerimetryAutomated Visual Field • Automated Perimetry for Glaucoma • Types of tests used • 30-2, 24-2, and 10-2 • Strategies used • SITA Standard, SITA Fast

  37. 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

  38. 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

  39. 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

  40. 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

  41. Automated PerimetryGlaucoma VF Types • Types • Nasal Step • Arcuate • Paracentral • Severity • Mild to Very Severe http://www.medrounds.org/glaucoma-guide/2006/02/section-1-c-understanding-vision-loss.html

  42. Visual FieldDiagnosing 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)

  43. Normal Visual Field

  44. Visual Field - Glaucoma

  45. Visual Field - Monitoring Progression

  46. Visual Field/OCT Integration

  47. Visual Field/OCT Integration

  48. Glaucoma Workup Review • The End! Questions?

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