Presentation on theme: "Glaucoma Workup Review: from A to OCT"— Presentation transcript:
1 Glaucoma Workup Review: from A to OCT Dr. Nathan RainsEye Center of Northern Colorado
2 What is Glaucoma? 3 million Americans have glaucoma One of the leading causes of adult blindnessNo symptoms until extensive peripheral vision loss (for most types of glaucoma)“sneak thief of sight”Chronic condition, no cure, just controlControl is lower eye pressures byEye drops, laser surgeries, or medical surgeries
7 Goals of Glaucoma Testing The ultimate goal of glaucoma testing is three fold:To Diagnose Glaucoma (probably the hardest step)Is the test RELIABLEIs the test REPEATABLETo Determine its SeveritySuspect, mild, moderate, severeInitiate treatment, set appropriate target pressures, etc.To Monitor Progression
10 What is Tonometry?The measurement of intraocular pressure (IOP) recorded in mmHgNormal IOP – mmHg (avg ~ 16mmHg)Ocular hypertension - >20-22mmHgDiurnal fluctuations – 4-6 mmHgPressure is highest at night, in the supine position (3 am)Difference between eyes – 2-3 mmHg>4-6 is suspiciousOnly treatable measure of glaucomaAll medicine and surgery is geared to this one task, lower IOPTested at every examination and followup care
13 Tonometry Instruments Indentation – iCare & Tonopen Good 38 sec video
14 Tonometry Instruments Non-Contact Tonometry AdvantagesNo anesthesia*No contactEase of useQuickDisadvantagesPatients 'love' to hate this testAccuracy?
15 Tonometry Instruments Goldmann Applanation Tonometry Gold standardAccurateInexpensiveeasy to useDisadvantagesAnesthesiastill dependent on corneal properties
16 Tonometry Instruments Take homesDigitalbasic, only detects extremely high pressuresIndentationportable, cheap, supineNon-contact tonometryexpensive machine, touchless, quick, patient discomfortApplanationgold standard, inexpensive, easy to use, less variability
18 What is Pachymetry?The measurement of corneal thickness, in microns (um)Average CENTRAL corneal thickness ~ 555 umIn glaucoma, used as a risk factor in the development of glaucomaOcular Hypertensive Treatment Study (OHTS)CCT <555, high riskCCT no increased riskCCT >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? TheoryThe thicker the cornea, the artificially high readingThe thinner the cornea, the artificially low readingIOP correction table?1975 studyEvery 100um adjust by 7mmHg17 other studies, all different IOP per 100um adjustment… no consensusReasonThickness 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 factorNo universal agreement on IOP correction table to useSo, 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 RELIABLEIs the test REPEATABLETo Determine its SeveritySuspect, mild, moderate, severeInitiate treatment, set appropriate target pressures, etc.To Monitor Progression
23 What is Glaucoma? By Type Primary Open Angle GlaucomaAcute Angle Closure GlaucomaPseudoexfoliative GlaucomaPigmentary GlaucomaNormal/Low Tension GlaucomaNeovascular GlaucomaCongenital GlaucomaTraumatic GlaucomaSecondary GlaucomaAnd more… over 60 types...
24 GonioscopyObtain a view of the drainage angle formed between the eye’s cornea and irisAids in diagnosis and monitoring of glaucomaPerformed under slit lamp, with a gonio lensUsed in laser treatment of the angle (SLT – selective laser trabeculoplasty)
31 Optical Coherence Tomography Non-invasive, high resolution, imaging technologyTime Domain vs Spectral DomainTD – 400 scans per sec, 10umSD – 20,000-40,000 per sec, 3um3-D reconstructionsAWESOME!Scan typesRetinal (macular)Optic Disc
32 OCT Optic Disc Scans the optic disc using a 6mm cube Obtains Retinal Nerve Fiber Layer ThicknessColor codes a thickness map‘hour glass’ appearanceRed (350um), to blue (0um)Normative tableRNFL thicknessSymmetryC/D ratioEtc.RNFL TSNIT MapQuadrant and Clock Hour RNFL thickness chart
34 OCT Optic Disc Diagnosing Glaucoma Average RNFLSymmetry>20um difference is statistically significantQuadrant RNFL layoutInferior and Superior are the greatest indicatorsClock Hour RNFL layoutInferior temp and/or superior temp thinLastly – does it correlate with the visual field***structural loss precedes VF loss***
36 OCT Optic Disc Monitoring Glaucoma Average NFLSymmetryProgression Analysis
37 Retinal Nerve Fiber Layer Anatomy FibersMake an arcDo NOT cross horizontal axisTemporal rapheDefects on nerve areopposite on fieldsCarl Zeiss Webinar Photo – Effective Perimetry
38 Perimetry Automated Visual Field Automated Perimetry for GlaucomaTypes of tests used30-2, 24-2, and 10-2Strategies usedSITA Standard, SITA Fast
39 Visual Field Types: 30-2, 24-2, 10-2 1st number refers to the degrees AROUND fixationEx: 10-2 – 10 degrees around the fovea (20 degrees total)2nd number refers to the protocolProtocol 1 – points directly on the horiz and vert axisProtocol 2 – points directly above and below axisEasier to interpret and used exclusively nowPoints tested30-2 – 6 degrees apart, total points 76, ~8 min per eye24-2 – 6 degrees apart, total points 54, ~5 min per eye10-2 – 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 variableSimilar results30-2 advantagesMore degrees of field testedMay help detect/monitor neurological defects, ie. Idiopathic intracranial hypertension
41 SITA Standard vs SITA Fast Best threshold testBetter for early detection in glaucomaMore reliable, more sensitiveSITA FastFast(er)Can be used for screening purposesMore Variable, less sensitive (underestimates) scotomas
42 When to use 10-2 in Glaucoma? Previously, used exclusively in severe peripheral field loss24-2 not providing enough information to monitor progression, so 10-2 replaces 24-2Recently, published in the JAMA Ophthalmology, January 2014, VF testing was found to detect early glaucomatous defects missed on 24-2Of 22 eyes tested as normal on 24-2 testing, 22.7% were abnormal in 10-2 testingMay use 10-2 in addition to 24-2
43 Automated Perimetry Glaucoma VF Types Nasal StepArcuateParacentralSeverityMild to Very Severe
44 Visual Field Diagnosing Glaucoma ReliabilityFixation losses, false positive, false negatives, etc.RepeatabilityWhen there’s a defect, is it repeatable?Three consecutive fields to reliably confirm glaucoma*Global IndicesGHT – glaucoma hemifield testMD – Mean DeviationPSD – Pattern Standard DeviationVFI – Visual Field Index (percentage)*Keltner et al. for the Ocular Hypertenstion Treatment Study Group, Arch Ophthalmol 123:1201 (2005)
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