CLINICAL METHODS IN DIAGNOSIS OF POAG OPTIC DISC 1.2-1.4 million axons/ 5000 loss/year 10%...

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CLINICAL METHODS IN DIAGNOSIS OF POAG OPTIC DISC 1.2-1.4 million axons/ 5000 loss/year 10% Magnocellular 90% Parvo- SIZE AND SHAPE DD: 1.5mm Surface: 2.1-2.8mm2 (π/4xHDxVD) AGE: no change after 3-10 years RACE: African>Asian>Mexican>Caucasian REFRACTIVE ERROR:independent [–5-+5DS] Positive correlation to rim and cup size

Transcript of CLINICAL METHODS IN DIAGNOSIS OF POAG OPTIC DISC 1.2-1.4 million axons/ 5000 loss/year 10%...

CLINICAL METHODS IN DIAGNOSIS OF POAG

OPTIC DISC

1.2-1.4 million axons/ 5000 loss/year10% Magnocellular90% Parvo-

SIZE AND SHAPE

DD: 1.5mm

Surface: 2.1-2.8mm2 (π/4xHDxVD)

AGE: no change after 3-10 years

RACE: African>Asian>Mexican>Caucasian

REFRACTIVE ERROR:independent [–5-+5DS]

Positive correlation to rim and cup size

Vertically oval (VDmax>HDmin by 10%)

Abnoral shape or tilted: corneal astigmatism- amblyopia

RIM SIZE AND SHAPE

Related to disc size (+)

ISNT rule (vert. oval disc/ Horizontal oval cup)

Positive correlation to ret. arteriole diameter

IT-ST-HT- IN-SN (predilection, mainly DIFFUSE loss)

ST: sharp border cup-rim

IT: some sloping (but NFL normal)

Pallor: ? Non-glaucomatous (increased cup size)

OPTIC DISC CUP

Increases with disc size

Horizontally oval

Depth: with disc size (deepest: JPOAG, Shallowest: high myopic type of POAG)- negative correlation to PPA

CD RATIO

H>V hence H/V>1.0 but in early to medium G <1.0

Normal range:0.0-0.9

Independent of optic media magnification

HCD/VCD: independent of cup and disc size

RNFL

Ganglion cells axons+astrocytes+ Muller cell processes

Visibility: unevenly distributed/ with age IT>ST>SN>IN>S>I>HT>HN

Correlates with rim thickness, retinal artery caliber and foveolar location

Sandwich arrangment

Red –free/ wide beam

Achromatic white light

Clinical examination

Direct ophthalmoscope

Indirect ophthalmoscope

Slit lamp

•Red-free•No stereo-

•Young children•Uncooperative•High myopes•Opacities

90D

78D

60D

FCL

DISC CHANGES IN POAG

GENERALIZED• Large cup• Cup asymmetry• Progressive in cup size• SaucerisationFOCAL

• Notching

•Vertical elongation•Cupping of rim margin•Regional pallor

•Splinter haemorrhage( specificity, early-med advanced, IT-ST, Progression, NTG)

LESS SPECIFIC

•Exposed lamina cribrosa•Nasal displacement•Baring of circumlinear vessels/ constriction of arterioles•PP crescent (spatial correlation with NRR loss)•Shunt vessels of optic disc (advanced stage)RNFL CHANGES•Focal defects wedge shaped (disc border-broad base to temporal raphe)20%, always pathologic but not pathognomonicv: from early to medium advanced G and very advanced Associated with notching, haem, PPA in that sector/NTG50% loss of thickness: visible

• Diffuse (commoner, more difficult to see)Sequence of sectors regarding RNFL visibilityRetinal vessels( clearer- sharper)

RECORDING OF FINDINGS

1. CD ratio: poor description

2. NRR: colour, contour, width

3. Diagram

4. PHOTO (stereo+ magnification)

AQUEOUS HUMOUR DYNAMICSGOLDMAN EQUATION: IOP= (F/C)+P

PRODUCTION

Rate: 2-3 μl/min (1% turnover/min)

Pigmented+non-pigmented cells

•Active transport (70%)

•Ultrafiltration (20%)•Osmosis (10%)OUTFLOW

0.22-0.28 μl/min /mmHg

•Trabecular (90%)

•Uveoscleral (10%)

EPISCLERAL VENOUS PRESSURE

10mmHg

IOP

Mean 16mmHg SD:3mmHg (10-22mmHg)

Non Gaussian distribution, skew to R (>40y)

•Diurnal variation/ Seasonal (W>S)

•Heart beat/ respiration

•Exercise/ Posture

•Fluid intake

•Medication (systemic, topical, alcohol, caffeine, cannabis))

•Age

•F>M after 40y

•Genetically influenced

IOP MEASUREMENT

1. Applanation tonometry (Imbert-fick: P= F/A)

Goldmann, Perkins

Airpuff (overestimate)

Tonopen (scar, oedema)

2. Indentation: Schiotz

3. Digital pressure

SOURCES OF ERROR

• Squeezing

•Valsalva•Pressure on globe•Tight collars•Calibration•EOM force to restricted globe FL: IOP and vice versa corneal astigmatism• corneal oedema•scar •CL •Central corneal thickness (LASIK, PRK)• Post scleral buckling