GLAUCOMA OPTIC DISC CHANGES

PRESENTED BY- PRAGATI JAIN

• Chronic progressive optic neuropathy caused by group of ocular conditions which lead to damage of optic nerve with loss of visual function.

Definitions• ONH-distal portion of optic nerve,extends from retinal

surface to myelinated portion of optic nerve.

• Composed of the nerve fibres which originates in the Ganglionic cell layer of retina & converge upon the nerve head from all points in the fundus.

• Relation between ONH and glaucoma was first described by von Graefe in 1857

• Physiological cup-represents partial or complete absence of axons

Pallor of cup results from exposure of lamina cribrosa and lack of glial tissue in the centre

• NRR-tissue b/w cup and disc margin I>S>N>T• Normal CDR is 0.3 :1 2% have CDR 0.7:1

Lamina cribrosa- porous region of sclera and also a specialized

extracellular matrix that consists of fenestrated sheets of connective tissue and occasional elastic fibres lined by astrocytes

• Peripapillary area-RNFL seen as striations in light reflex from bundles of nerve fibres.

Distribution of retinal nerve fibre-

Arrangement of nerve fibres within ONH-From peripheral part of retina lie deep in retina & occupy

most superficial part of ODFibres closer to ONH lie superficial in retina.

Pathogenesis of ONH changes in glaucoma

• Mechanical effect-raised IOP forces lamina cribrosa backwards and squeezes nerve fibres within ,disturb axoplasmic flow

• Vascular effect-ischaemic atrophy of nerve fibre

ONH Signs Suggestive Of Glaucoma• Size of cup in relation to size of ONH-Small disc with deep cup

Medium disc with deep cup

Meduim disc with large cup

Large disc with large cup

• Asymmetry of cups-

0.2 in both eyes suspicion.

• Vertical enlargement of cup-

Vertical CDR > horizontal CDR

Loss of axons occur more in superior and inferior regions so NRR thinning at vertical poles

• Focal atrophy and polar notching

Inferotemporal region,sometimes superotemporally

Small discrete defect due to loss of neural rim tissue

• Sharpened nasal margins-

As focal defect enlarges and deepens it may develop sharp nasal margins adjacent to major blood vessels.

• Sharpened rim-

NRR is lost adjacent to edge of the disc

No visible neural rim is seen

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• Bayonetting sign-double angulation of blood vessel

When retinal vessels cross the sharpened rim,it will bend sharply at the edge of the disc

• Laminar dot sign/shadow sign

As loss of axon progresses the normal colour is replaced by greyish hue.

Deepening of cup

s/o Advanced damage

• Overpass cupping-

Vessels initially bridge the deepened cup and later collapse into it

• Pallor areas on the disc-

Kinking of vessels at cup margin

Colour cup- extent of central pallor

Contour cup- site at which vessel change their contour

Enlargement of cup may progress ahead of pallor

Pathognomic of glaucomatous optic atrophy

• Saucerization-Diffuse shallow cupping extends disc margin with retention of

central pale cup

Focal saucerization –more localized shallow sloping cup

Early s/o glaucoma

• Tinted hollow-

Retention of normal NRR colour in area of focal saucerization

• Splinter haemorrhage or Drance heamorrhage-At disk margin,extends from NRR onto retina

m/c inferotemporally

Significant early finding,risk factor for development and progression

Precedes RNFL changes and field defects

• Barring of circumlinear vessels-

Space b/w NRR and superficial blood vessels

Vessels appear to be barred from margin of the cup

• Tortousity of retinal vessels-As response to chronic ischaemia

• Collaterals b/w 2 veins at the disc may also be seen

• Advanced glaucomatous cupping-Loss of all neuroretinal tissue Total cupping seen as white disc Bending of vessels at margin of discBean pot cupping

• RNFL defect precedes detectable OD and visual field changes

• It can be a. localized wedge shaped defect b. diffuse defect that are larger and have indistinct

borders

• More evident following disc haemorrhage

• Red free light are used to see the defects

• Peripappillary pigmentary disturbances

• Scleral lip/peripappillary halo-even white rim that marks disc margin,anterior extension of sclera b/w choroid and optic nerve

• Zone beta

• Zone alpha

• Alpha zone-irregular hypo or hyper pigmented zone associated with chorioretinal thinning.

• Beta zone-represents loss of RPE and choriocapilaries leaving intact choroidal vasculature.

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