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Optic atrophy
- 3. • Primary opticatrophy • Secondary optic atrophy • Consecutive optic atrophy Based on ophthalmoscopic appearance
- 4. Primary optic atrophyoccurs without any antecedent swelling of the optic nerve head The essence of primary optic atrophy is loss of optic nerve fibres with minimal disturbance in optic nerve microanatomy It may be caused by lesions affecting the visual pathways at any point from retrolaminar portion of the optic nerve to the lateral geniculate body Lesions anterior to the optic chiasm result in unilateral optic atrophy Lesions involving the chiasm and the optic tract will cause bilateral changes
- 5. Flat white disc(chalky white) with clearly delineated margins Reduction in the number of small blood vessels on the disc surface Attenuation of peripapillary blood vessels and thinning of retinal nerve fibre layer Atrophy can be diffuse or sectoral depending on the level of lesion Temporal pallor indicates atrophy of the papillomacular bundle Band atrophy is caused by involvement of fibres entering optic disc either nasally or temporally, occurs due to lesion of the chiasm or optic tract. It gives nasal as well as temporal pallor
- 6. Reduction in opticnerve diameter Reduction in the number of axons Minimal gliotic changes Reduction in the number and size of blood vessels Thickening of connective tissue septa
- 7. Optic neuritis Compression bytumours and aneurysms Hereditary optic neuropathies Toxic and nutritional optic neuropathies • Show early temporal pallor due to affection of papillomacular fibres Trauma
- 9. Signs vary accordingto the cause and its course Slightly or moderately raised white or greyish disc with poorly delineated margins due to gliosis Obscuration of the lamina cribrosa Reduction in the number of small blood vessels on the disc surface Peripapillary circumferential retinochoroidal folds (Paton lines) specially temporal to the disc Sheathing of arterioles and venous tortuosity may be present
- 10. Loss of fibres Gliosisof optic nerve head and peripapillary vasculature Glial cell proliferation on the surface and edges of the disc Astrocytes are seen throughout the optic nerve head and in heaps anterior to the disc
- 11. Chronic papilledema Anterior ischaemicoptic neuropathy Papillitis Intraocular inflammatory causes of marked disc swelling are sometimes considered to cause secondary rather than consecutive optic atrophy
- 16. Diffuse enlargement an beanpot like cupping of the optic disc cup This kind of optic atrophy is described classically with ischaemic lesions of the optic nerve head
- 17. Ascending Primary diseaseprocess that causes that causes death of ganglion cells or their axons which leads to degenerative changes along the optic nerve head , chiasm, tracts and lateral geniculate body Retinitis pigmentosa, Leber’s hereditary optic neuropathy Descending It results from a disease process which primarily behind the optic nerve head with degenerative changes with the degenerative changes proceeding downstream all the way to retinal ganglion cell Seen with compressive lesions, inflammatory diseases and some cases of toxic, metabolic and nutritional optic atrophy Usually transsynaptic degeneration does not occur, however, in children and young adults descending atrophy has been noted following visual cortex lesions
- 18. Presence of opticdisc pallor • Normally 10 blood vessels are seen passing across the optic nerve margins • Kestenbaum’s capillary drop down test – from 10 to 7 or less Loss of small blood vessel • There maybe narrowing of blood vessels over the optic disc • May be associated with gliosis of blood vessels over the optic disc head Changes in the blood vessels over the optic disc • Over the optic nerve head and peripapillary retinaGliotic changes
- 19. Morphological appearance ofthe disc may vary according to the different aetiologies It depends on extent and severity of optic nerve damage Accordingly it maybe subclassified as • Mild, moderate or severe • Diffuse or sectoral • Total or partial
- 20. In AION thereis characteristic superior and inferior disc pallor In chiasmal lesion, decussating fibres from the nasal retina are involved, it tends to produce a bow tie pattern of ischaemic optic neuropathy. It also involves the temporal retina of both sides but spares superior and inferior retinas Patients with optic neuritis tend to produce temporal pallor of the involved optic discs
- 21. Thinning of opticnerve secondary to loss of parenchyma Decrease in number of axon cylinders Loss of ensheathing myelin Widening of pial septa, increase in subarachnoid space and dura becoming redundant Variable degree of gliosis can be noted Fragmentation and engulfment of myelin by phagocytes may occur along with remyelination Loss of retinal ganglion cell layers LGB may or may not show signs of atrophy
- 22. Optic disc hypoplasia Opticdisc coloboma Optic disc pit Tilted discs Optic disc drussens Morning glory syndrome
- 23. Healthy optic discis yellow-pink in colour, due to total internal reflection through the axonal fibres and reflection from surface capillaries The temporal quadrant is normally lighter than the others Degenerated axons lose this optical property, hence the disc appears pale Pallor is also contributed to the loss of pial capillaries which supply optic disc
- 25. Axonal degeneration canbe anterograde or retrograde depending on the location of the inciting factor Microscopic examination shows excavation of the cup and baring of the lamina cribrosa Thinning of axons, gliosis and widening of subarachnoid space In vivo microscopic evaluation of optic nerve head can be done by OCT
- 26. Reduced visual acuity(normal to PL neg) Colour vision is affected more in optic nerve disorders than those with retinal disorders RAPD detected by Levantin’s swinging flashlight Contrast sensitivity is measured by Pelli-Robson contrast sensitivity chart or Cambridge low-contrast grating test Pulfrich phenomenon – illusion of horizontally oscillating object appear to be moving in elliptical orbit
- 28. Based on • Modeof onset • Distribution of optic disc pallor • Visual field examination • Imaging and electrophysiology
- 30. Specific patterns discussedbefore • In AION there is characteristic superior and inferior disc pallor • In chiasmal lesion it tends to produce a bow tie pattern • Patients with optic neuritis tend to produce temporal pallor of the involved optic discs • Marked attenuation of blood vessels with presence of retinal pigmentary changes is suggestive of consecutive optic atrophy
- 31. • Generalised reductionof sensitivity, centrocaecal scotomaOptic neuritis • Superior or inferior altitudinal field defectsAION • Bitemporal hemianopia • Total monocular field loss in one eye and quadrantanopia in the other eye Chiasmal tumours • Homonymous hemianopia Tumours of posterior visual pathway and visual cortex
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- 33. Prolongation of P100onVEP It maybe possible to detect inter eye differences in latencies P100 prolongation returns to normal in only 30% patients
- 34. Most other neuropathiesshow reduction in the amplitude No specific P100 pattern Therefore role of electrodiagnosis is getting limited in the diagnosis
- 35. History taking Optic nervehead evaluation Visual testing Colour vision Contrast sensitivity Visual field analysis Neuro imaging
- 36. Systemic • Diabetes • Hypertension •Hyperlipidaemia • Abnormal carotid circulation • Hyperhomocysteinemia Other investigations • Carotid doppler USG • VDRL/TPHA • SerumVitB12 • ANA • Sarcoidosis work up • APLA • TORCH panel Ophthalmic investigations
- 39. Primary optic atrophy Optic neuritis Intracranialmass Trauma Hereditary Toxic Secondary optic atrophy Papilledema AION Papillitis Consecutive optic atrophy Retinitis pigmentosa Healed vasculitis Excessive pan retinal photocoagulation
- 40. Feature Primary SecondaryConsecutive Colour Chalky white Dirty white (grey) Waxy pallor Cup Shallow Filled up Normal Vessels Normal Normal/attenuated Grossly thinned out Margin Well defined Blurred Well defined