optic disc evaluation in glaucoma
DESCRIPTION
Optic Disc Evaluation IN Glaucoma. Dr Deepak Megur DOMS FRCS Ed Glaucoma & Cataract Services Megur Eye Care Centre Bidar 585401. What is Glaucoma…?. Glaucoma =Optic neuropathy. The evaluation of the appearance of the optic disc is central to the diagnosis and management of Glaucoma - PowerPoint PPT PresentationTRANSCRIPT
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Optic Disc Evaluation IN Glaucoma
Dr Deepak Megur DOMS FRCS EdGlaucoma & Cataract Services
Megur Eye Care CentreBidar 585401
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What is Glaucoma…?
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Glaucoma =Optic neuropathy
• The evaluation of the appearance of the optic disc is central to the diagnosis and management of Glaucoma
• Optic Disc Evaluation:– Why..?– How..?– What to look for..?
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The 4 goals of optic disc evaluation
• Distinguishing between the healthy and the sick =Diagnosing.
• Quantifying the amount of damage: Healthy,Mild,Moderate,Advanced Disease
• Monitoring Change,for better or for worse• Quantitating the rate of change
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1.5 mm3 mm
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Optic Disc Evaluation ..
• Slit lamp biomicroscopy : Ideal– Stereoscopic View –Cupping– Measuring the optic disc size
• Direct Ophthalmoscopy– Good Magnification
• Indirect Ophthalmoscopy– Overall View
• Optic disc Photoghraphy.– Documentation,Monitoring for progression.
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The 7 parameters to look for…1)Disc: Size and Shape
2)Neuroretinal Rim (NRR): Size,Shape,Pallor ISNT rule
3)Cup: Size and Shape in relation to the optic disc size,-Vertical C/ D Ratio, Cup depth / Excavation
4) Optic Disc Hemorrhage: Presence & Location
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The 7 parameters to look for…
5) Nerve Fibre Layer Defect: focal & diffuse
6) Para Papillary Atrophy; Size,location & Configuration
7) Retinal Arterial Attenuation: focal & diffuse
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All these variables can be measured semiquantitavively by ophthalmoscopy without applying
sophisticated techniques
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1)Optic Disc: Size & Shape
• Determining the size of the disc =Crucial– Helps to differentiate Physiological cupping from
Pathological.• Large discs have big physiological cups.• Small Discs have small cups or no cups
• Measurement of Vertical Disc diameter :– Length of the vertical beam of slit lamp light– Multiplied by correction factor of the condensing lens– Volk 60 D= X 1– Volk 90D= X 1.5
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Cup: Size, Shape, location in relation to the disc size
• Optic Cup= Excavation in the optic nerve head– Stereoscopic evaluation
• In normal eyes= Areas of optic disc & Optic cup are corelated
• Large optic discs=Large cup• Small optic disc =Small cup or no cup• Early & moderate glaucomatous damage in
small disc may be missed because of the erroneously low cup disc ratios
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Large Disc=Large Cup
3mm
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1.5 mm3 mm
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Early & moderate glaucomatous damage in small disc may be missed because of the erroneously low cup disc ratios
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Vertical Cup Disc Ratio
• Vertically oval optic disc• Horizontally oval optic cup• In normal eyes: Horizontal CD ratio > than
vertical CD ratio• In Glaucomatous eyes: Vertical CD ratio >
than the horizontal CD ratio
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Vertical CD ratio
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The Neuroretinal Rim
• Size, Shape, Pallor.• The ISNT rule:
I>S>N>T
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• Thinning of the NRR• Pallor of NRR• Notching:
– A notch is a localized defect in the Neuroretinal rim on the cup side of the rim
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The Neurretinal rim loss in Glaucoma
• Usual sequence of NRR loss in Glaucoma:– Inferotemporal– Superotemporal– Horizontal temporal– Inferonasal– Superonasal
• In contrast,in the non glaucomatous optic nerve damage, the NRR is not always affected and hence contour of NRR is maintained.
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NRR , the “ISNT Rule”
I>S>N>T
I>S>N>T
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I<S<N>T
I<S>N>T
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I<=S>n>TI>S>N>T
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Optic Disc Hemorrhage• Splinter or Flame shaped
hemorrhages • At the margin of the disc• Hallmark of
Glaucomatous optic nerve damage
• 4 to 7 % of eyes with galucoma
• Found in early & moderately advanced Glaucoma and rare in very advanced stage
• Located usually in the inferotemporal & superotemporal disc margins
• Associated with localized RNFL defect and neuroretinal rim notches .
• Suggests Progression. • More common in NTG
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Optic Disc Hemorrhage
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Optic Disc Hemorrhage
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Retinal Nerve Fibre Layer Defect
• RNFL contains retinal ganglion cells axons covered by astrocytes and bundled by processes of muller cells
• Seen as bright fine striations fanning off from the disc to the periphery.
• Dilated pupil, green light, clear optical media aids the evaluation of RNFL
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Retinal Nerve Fibre Layer Defect
• Localized RNFL defects:– Can be detected before visual field defect has
developed– Focal type of NTG– Early to medium advanced Glaucomatous damage
• Diffuse loss of RNFL:– More difficult to detect– Peripapillary retinal vessels appear bare– Underlying Choroidal vessels more clearly seen.
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Diffuse RNFL loss
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Parapapillary Chorioretinal atrophy
• 2 zones– Central Beta zone– Peripheral alpha zone
• Beta zone occurs more often in glaucomatous eyes than in normal eyes.
• Helps to differentiate various subtypes of POAG
• Helps to differentiate from nonglaucomatous optic nerve damage
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Parapapillary Chorioretinal atrophy
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Retinal Artery attenuation
• Diffuse narrowing:– Decreasing NRR– Increased RNFL loss– Increased Visual field
defects
• Focal Attenuation– More common in NTG– Degree of narrowing
increases with amount of damage.
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Diffuse Retinal arterial attenuation
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Pre Perimetric Diagnosis of Glaucomatous Optic Nerve damage
• Most important Variables– Shape of the NRR– Size of the cup in relation to the optic disc– Diffuse or focal RNFL defects– Disc Hemorrhages
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Pre Perimetric, Very Early
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Early Damage
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Moderate
One pole of the disc is damaged
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Advanced
Both the poles affected
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Advanced…
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Disc Damage Likelihood Scale
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Optic Disc PhotographsOptic Disc Drawings
Documentation of disc damage:Monitoring change for
progressionRate of change
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Thank You