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OPTIC ATROPHY

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OPTIC ATROPHY

OPTIC ATROPHYAnatomyAfferent fibres. The optic nerve carries approximately 1.2 million afferent nerve fibres which originate in the retinal ganglion cells. Most of these synapse in the lateral geniculate body, although some reach other centres, notably the pretectal nuclei in the midbrain. Nearly one-third of the fibres subserve the central 5 of the visual field. Within the optic nerve itself the nerve fibres are divided into about 600 bundles, each containing 2000 fibres, by fibrous septae derived from the pia mater

Surrounding sheaths a The innermost sheath is the delicate vascular pia mater. b The outer sheath comprises the arachnoid mater and the tougher dura mater which is continuous with the sclera; optic nerve fenestration involves incision of this outer sheath. The subarachnoid space is continuous with the cerebral subarachnoid space and contains cerebrospinal fluid (CSF).

DEFINITION:It refers to degeneration of the optic nerve, which occurs as an end result of any pathologic process that damages axons in the anterior visual system i.e from retinal ganglion cells to the lateral geniculate bodyCLASSIFICATION:Primary versus secondary optic atrophyOphthalmoscopic classificationAscending versus descending optic atrophy

PRIMARY VERSUS SECONDARY:PRIMARY OPTIC ATROPHY: - it refers to simple degeneration of the nerve fibres without any complicating process within the eye eg: syplilitic optic atrophy of tabes dorsalis. Tabetic optic atrophy:Tabes degeneration was due to chronic inflammation of the pia which caused a secondary degeneration of the nerve fibres commencing in the optic nerve near the chiasma.slowly progressive and prognosis is badBut with antisyphilitic treatment disease is rare.

SECONDARY OPTIC ATROPHY: -it occurs following any pathologic process which produces optic neuritis or papilloedema

OPHTHALMOSCOPIC CLASSIFICATIONClassified based on ophthalmoscopic appearance as followsPrimary (simple) optic atrophyConsecutive optic atrophyGlaucomatous optic atrophyPost - neuritic optic atrophyVascular (ischaemic) optic atrophy

ASCENDING VERSUS DESCENDING OPTIC ATROPHYAscending atrophy follows damage to ganglion cells or nerve fibre layer due to disease of the retina or optic disc.In it nerve fibre degeneration progresses (ascends) from the eyeball towards the geniculate bodyDescending or retrograde optic atrophy proceeds from the region of the optic tract, chiasma or posterior portion of the optic nerve towards the optic disc.ETIOLOGICAL CLASSIFICATION:CONSECUTIVE ATROPHY: -secondary to retinal disease and destruction of ganglion cells post inflammatory: diffuse chorioretinitis degenerative: primary pigmentary and systemic degeneration

PRESSURE AND TRACTION ATROPHY: - glaucomatous - postpapilledema, due to swelling and pressure at disc -arterial, sclerosed and frequently calcified artery pressing upon nerve - aneurysms of internal carotid - bony pressure at optic foramen (osteitis deformans,oxycepaly) - tumors (optic nerve sheaths, orbit, cranium) - imflammatory adhesions (basal arachnoiditis) -swelling in nerve (neurofibromatous degeneration of v.recklinghausn disease)CIRCULATORY ATROPHY: - occlusion of central retinal artery - post haemorrhagic - arteriosclerotic, producing ischemic degeneration

POST INFLAMMATORY ATROPHY: Optic neuritis, perineuritis disseminated sclerosis neuromyelitis optica herpes zoster tabes

TOXIC ATROPHY: Endogenous toxins: diabetes, anemia, malignant tumors, hyperthyroidismExogenous toxins: tobacco, alcohol, arsenic, leadTRAUMATIC ATROPHY: mechanical injury secondary to fracture of skullATROPHY OF UNKNOWN ORIGIN: lebers diseasePATHOLOGICAL FEATURES:ACUTE NECROSIS: -occurs following acute trauma or surgical division of nerve - at site of injury axons are destroyed and medullary sheaths fragmented - degeneration of all elements of nerve - then there is proliferation of astrocytes and development of neuroglial scar formation.

SECONDARY DEGENERATION: - following lesions of optic nerve there is destruction of nerve fibres and development of optic atrophy -it may be ascending or decending atrophyREGENERATION OF OPTIC NERVE: - fibres grow from both ends of nerve provided ganglion cells of retina are intact. - no successful union of regenerating fibres due to absence of neurilemma sheaths. - after several weeks these fibres which grow into scar tissue degenerate.

Degeneration of optic nerve fibres is associated with attempted but unsuccessful regeneration which is characterised by proliferation of astrocytes and glial tissue.Ophthalmoscopic appearance of the atropic disc depends upon balance between loss of nerve tissue and gliosisFollowing three situations may occur:Degeneration of the nerve fibres may be associated with excessive gliosis. Occurs in consecutive and post-neuritic optic atrophy2)Degeneration and gliosis may be orderly and the proliferating astrocytes arrange themselves in longitudinal columns replacing the nerve fibres (columnar gliosis)occurs in primary optic atrophy

Degeneration of the optic nerve fibres may be associated with negligible gliosis - occurs due to progressive decrease in blood supply - such pathological changes are known as cavernous optic atrophy - occurs in glaucomatous and ischaemic (vascular) optic atrophy ETIOLOGY:PRIMARY (SIMPLE) OPTIC ATROPHY: -occurs due to lesions proximal to the optic disc without antecedent papilloedema. -It may be caused by lesions affecting the visual pathways from the retrolaminar portion of the optic nerve to the lateral geniculate body. - Lesions anterior to the optic chiasm result in unilateral optic atrophy, whereas those involving the chiasm and optic tract will cause bilateral changes. Causes: 1. multiple sclerosis 2. retrobulbar neuritis(idiopathic) 3. lebers and other hereditary optic atrophies 4. intracranial tumors (pressing directly on anterior visual pathway) 5. traumatic severance or avulsion of the optic nerve 6. toxic amblyopia (chronic retrobulbar neuritis)7. tabes dorsalisCONSECUTIVE OPTIC ATROPHY:occurs following destruction of ganglion cells secondary to degenerative or inflammatory lesions of the choroid and /or retina.Causes: 1) diffuse chorioretinitis 2) retinal pigmentary dystrophies (retinitis pigmentosa) 3) pathological myopia 4) occlusion of central retina 5) old vasculitis 6) retinal necrosis 7) excessive retinal photocoagulation.

POSTNEURITIC OPTIC ATROPHY: - it is also known as secondary optic atrophy 1 -develops as a sequelae to long standing papilloedema or papillitis - Causes include chronic papilloedema, anterior ischaemic optic neuropathy and papillitis.

GLAUCOMATOUS OPTIC ATROPHY: results from the effect of long standing raised intraocular pressure

VASCULAR (ISCHAEMIC) OPTIC ATROPHY: results from the conditions (other than glaucoma) producing disc ischaemia.Causes : 1) giant cell arteritis 2) severe haemorrhage 3) severe anaemia 4) quinine poisoningCLINICAL FEATURES:LOSS OF VISION : -sudden or gradual(depend on cause) - partial or total (depending on degree of atrophy) -ophthalmic signs cannot be correlated with amount of visionPUPIL: semidilated and direct light reflex is very sluggish or absent marcus gunn pupil on swinging flash light testVISUAL FIELD:- vary with the distribution of the fibres that have been damaged - field loss is peripheral in systemic infections, central in focal optic neuritis and eccentric when nerve or tracts compressedOPHTHALMOSCOPIC APPEARANCE: -varies with the type of optic atrophy - pallor of the disc and decrease in no of small blood vessels (kastenbaum index) - pallor not due to atrophy of nerve fibres but to loss of vasculature

PRIMARY OPTIC ATROPHY: -disc is chalky white or white with bluish hue -edges sharply outlined -slight recession of entire optic disc in total atrophy and the temporal side of disc in total optic atrophy -lamina cribrosa is clearly seen at the bottom of the physiological cup -major retinal vessels and surrounding retina normal

-Reduction in the number of small blood vessels on the disc surface (Kestenbaum sign). -Attenuation of peripapillary blood vessels and thinning of the retinal nerve fibre layer. -The atrophy may be diffuse or sectoral depending on the cause and level of the lesion. -Temporal pallor may indicate atrophy of fibres from the papillomacular bundle, which enters the optic nerve head on the temporal side. - Band atrophy caused by involvement of the fibres entering the optic disc nasally and temporally with sparing of the superior and inferior portions occurs in lesions of the optic chiasm or tract

POST-NEURITIC OPTIC ATROPHY:-optic disc dirty white in colour-due to gliosis edges are blurred, physiological cup obliterated and lamina cribrosa not visible- retinal vessels are attenuated and perivascular sheathing present - hyaline bodies (drusen) may be present on or about the disc

CONSECUTIVE OPTIC ATROPHY: -disc appears yellow waxy -edges are not so sharply defined as in optic atrophy -retinal vessels are attenuated

GLAUCOMATOUS OPTIC ATROPHY:-deep and wide cupping of the optic disc and nasal shift of the blood vesselsISCHAEMIC OPTIC ATROPHY: - pallor of optic disc associated with marked attenuation of the vessels

DIFFERENTIAL DIAGNOSIS:Pallor of the optic disc does not signify optic atrophy unless there is dmonstrable defect in vision or in the visual field.

PATHOLOGICAL PALLOR OF OPTIC DISC: hypoplasia congenital pit colobomaNON-PATHOLOGICAL PALLOR OF OPTIC DISC: axial myopia infants elderly people with sclerotic changes temporal pallor associated with large physiological cupPROGNOSTIC FACTORS:Atrophic cupping: -if present and involves entire disc, visual acuity is decreased and indicates bad prognosisAttenuation of arteries: - is a sign of bad prognosis - but transient narrowing (angiospasm) does not indicate poor prognosisPapilledema combined with pallor of the discs: - indicates poor prognosis for visionGlaucoma and optic atrophy: - when glaucoma advanced to stage of glaucomatous atrophy , poor prognosis seen wheather ocular tension lowered or not

Optic atrophy and intracranial tumors, brain abscess, arachnoiditis: - pallor of disc and visual field defects does not indicate poor prognosis - in such cases if there is absence of atrophic cupping and if retinal vessels are not narrowed, operative treatment results in good improvement

Optic atrophy and the demyelinizing diseases : -occurs in disseminated sclerosis, encephalomyelitides and neuromyelitis optica - prognosis is good in these conditions

Parenchymatous optic atrophy : - is seen in tabes dorsalis - normal fundus with pallor of disc - bad prognosis

TREATMENT:In case of partial optic atrophy underlying cause when treated helps in preserving some vision.Once complete atrophy sets in, vision cannot be recovered.THANK YOU