Glaucoma optic disc changes

glaucoma

1. GLAUCOMA OPTIC DISC CHANGES PRESENTED BY- PRAGATI JAIN

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

3. 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

4. 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

5. 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

6. 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 OD Fibres closer to ONH lie superficial in retina.

7. 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

8. 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

9. Asymmetry of cups - 0.2 in both eyes suspicion.

10. Vertical enlargement of cup- Vertical CDR > horizontal CDR Loss of axons occur more in superior and inferior regions so NRR thinning at vertical poles

11. Focal atrophy and polar notching Inferotemporal region,sometimes superotemporally Small discrete defect due to loss of neural rim tissue

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

13. Sharpened rim- NRR is lost adjacent to edge of the disc No visible neural rim is seen

14. ` Bayonetting sign- double angulation of blood vessel When retinal vessels cross the sharpened rim,it will bend sharply at the edge of the disc

15. 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

16. Overpass cupping- Vessels initially bridge the deepened cup and later collapse into it

17. 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

18. 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

19. 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

20. Barring of circumlinear vessels- Space b/w NRR and superficial blood vessels Vessels appear to be barred from margin of the cup

21. Tortousity of retinal vessels- As response to chronic ischaemia Collaterals b/w 2 veins at the disc may also be seen

22. Advanced glaucomatous cupping- Loss of all neuroretinal tissue Total cupping seen as white disc Bending of vessels at margin of disc Bean pot cupping

23. 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

24. 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

25. 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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