BISMILLAHIR RAHMANIR RAHIM

Optic AtrophyChairperson: Prof. Dr. Syed Abul Kalam

Azad

Presented by: Dr. Wahid Karim

DO Resident,

DMCH.

DefinitionOptic atrophy 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 body.

Types or Classification

It can be classified in several ways, including by whether axonal death is initiated in the retina(anterograde) or more centrally (retrograde), and by cause. Optic ‘atrophy’ is not true atrophy, a term that strictly refers to involutional change secondary to lack of use. It is due to loss of vascularity owing to obliteration of of the disc capillaries.

Types or classification A. Aetiolgical: (i) Primary, (ii) Secondary, (iii) Consecutive. B. Pathological: (i) Ascending: From optic nerve to brain.

Ascending or anterograde optic atrophy (Wallerian degeneration): Follows damage to ganglion cells or nerve fibre layer due to diseases of the retina or optic disc. In it the nerve fibre degeneration progresses (ascends) from the eyeball towards the geniculation body. (ii) Descending or retrograde optic atrophy: proceeds from the region of the optic tract, chiasma or posterior portion of the optic nerve towards the optic disc. Damage beyond lateral geniculate nucleus (LGN), i.e., optic radiations and occipital cortex does not cause optic atrophy as the second order neurons (axons of ganglion cells) synapse in LGN.

C. Extent: (i) partial, (ii) Total.D. Cliniclal/Ophthalmological: (i) Primary, (ii) secondary, (iii)

Cavernous or Glaucomatous, (iv) consecutive: It is ascending type.

Pathogenesis

The process consists of increased interstitial connective tissues with atrophy & disappearance of some nerve fibers & their myelin sheath.

Primary Optic atrophyPrimary optic atrophy occurs without antecedent swelling of the optic nerve head. It may be caused by lesions affecting the visual pathways at any point 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.

Signs:Flat chalky white disc with clearly delineated margins.Reduction in the number of small blood vessels on the disc surface.Attenuation of peripapillary blood vessels and thinning of the retinal nerve fibre layer (RNFL).

Stippling of Lamina Cribrosa.The atrophy may be diffuse or sectoral depending on the

cause and level of the lesion. Temporal pallor of the optic nerve head may indicate atrophy of fibres of the papillomacular bundle, and is classically seen following demyelinating optic neuritis. Band atrophy is a similar phenomenon caused by involvement of the fibres entering the optic disc nasally and temporally; it occurs in lesions of the optic chiasm or tract and gives nasal as well as temporal pallor.

Important causesOptic neuritis.Compression by tumours and aneurysms.Hereditary optic neuropathies.Toxic and nutritional optic neuropathies.Trauma or hemorrhage. Multiple sclerosis (most common cause).Tabes dorsalis (classical cause).Leber’s optic atrophy.

Secondary Optic AtrophySecondary optic atrophy is preceded by long-standing swelling of the optic nerve head.Signs vary according to the cause and its course.Slightly or moderately raised dirty white or greyish disc with poorly delineated margins due to gliosis. Optic disc is full of connective tissues.Obscuration of the lamina cribrosa.Reduction in the number of small blood vessels on the disc surface.Peripapillary circumferential retinochoroidal folds, especially temporal to the disc (Paton lines), sheathing of arterioles and venous tortuosity may be present.Causes include:Chronic papilloedema, Anterior ischaemic optic neuropathy. Papillitis.Neuro-retinis.

Consecutive optic atrophyConsecutive optic atrophy is caused by disease of the inner retina or its blood supply. The cause is usually obvious on fundus examination. Causes are:Extensive retinal photocoagulation, Retinitis pigmentosa Central retinal artery occlusion.Diabetc Retinopathy.Extensive Retino-choroiditis.Pathological myopia etc.

Clinical Featurs (i) Waxy pale of disc. (ii) Edge: Less Sharply formed. (iii) Laminar dot sign in Lamina cribrosa. (iv) Cup: Sometimes large optic cup. (v) Retinal blood vessels: Markedly contracted, Chorioretinal changes occur.

Glaucomatous optic atroophy It is specific for glaucoma: I.Characterized by deep and wide cupping of optic disc & nasal shifting of flood vessels. Pale colour of disc Increased cup: Disc ratio. II.Disappearance of optic nerve fibre layer with out increasing connective tissue. III.So that, large cavernous lacunae forms are found.

Fig. Optic atrophy. (A) Primary due to compression; (B) primary due to nutritional neuropathy – note predominantly temporal pallor; (C) secondary due to chronic papilloedema – note prominent Paton lines (D) consecutive due to vasculitis

Fig. Glaucomatous optic atrophy

Differences between clinical features of primary, secondary & consecutive optic atrophies

Feature Primary Secondary Consecutive

APPEARANCE Chalky white Dirty grey white

Waxy pallor

MARGINS Well defined Ill defined Well defined

LAMINA CRIBROSA

Well seen Obscured Well seen

VESSELS Normal Peripapillary sheathing

Attenuation

SURROUNDING RETINA

Healthy Hyaline bodies/ drusen

Pathology seen

Total Optic atrophyClinical Features: (i) Pupil dilated, fixed, non-

reacting (Bilateral. (ii) Consecutive consensual reaction

exaggerated (unilateral).Vision: No perception of light (NPL).

Partial Optic atrophy Clinical features: (i)Vision: Reduced to counting finger (CF) 5';7'(ii)Conscentric contraction of visual field with or

without scotoma. That means tubular vision. Most forms of partial optic atrophy , involve a loss

of temporal fibres including the papillomacular bundles. This results in ‘temporal pallor’. But this should be confirmed by special investigations, since, temporal side is normally pale, because the retinal vessels emerge from the nasal side, and the temporal side is normally less vascular.

Differential DiagnosisOptic atrophy versus other causes of optic disc pallor:• Pallor of optic disc in partial optic atrophy must be

differentiated from other causes of pallor disc which may be non-pathological or pathological.

o Non-pathological pallor of optic disc: it is seen in Axial myopia. Infants. Elderly people with sclerotic changes. Temporal pallor is associated with large physiologic cup. o Pathological pallor of optic disc other than optic

atrophy: this includes Hypoplasia. Congenital pit. Coloboma.

Investigations:• Field of vision: In partial optic atrophy, the

central vision is depressed with concentric contraction of the visual field, according to the cause.

• Pupil may be semidilated & direct light reflex is very sluggish or absent. Swinging flash light test depicts Marcus Gun Pupil (RAPD).

• Fluorescein angiography of the optic nerve head.• Visual Evoke response (VEK) is useful specially

in children.• Total neurological evaluations like, X-ray of

skull, CT Scan, MRI of brain and optic nerve etc.

Treatment Treatment of underlying cause may help in preserving some vision in patients with partial optic atrophy. However, once complete atrophy has set in, the vision cannot be recovered. Treatment is according to cause. However, high dose of vitamin B1, B6, B12 is given. Hydroxocobalamine (vitamin-B12) 1000 µg is administered for atrophy due to toxic optic neuritis.

Miscellaneous hereditary optic atrophies

This heterogeneous group of rare disorders are characterized primarily by bilateral optic atrophy. There is no effective treatment, though some measures should be taken. Dominant optic atrophy (Kjer type optic atrophy, optic atrophy type 1)Inheritance is autosomal dominant (AD); this is the most common hereditary optic atrophy with an incidence of around 1 : 50 000; it is frequently due to a mutation in the OPA1 gene on chromosome, which causes mitochondrial dysfunction.

Presentation is typically, though not always, in childhood with insidious visual loss. There is usually a family history, but the course may be variable even within the same family.

Optic atrophy may be subtle and temporal, or diffuse. There may be enlargement of the cup.

Prognosis is variable (final VA 6/12–6/60) with considerable differences within and between families. Very slow progression over decades is typical.

Systemic abnormalities. Twenty per cent develop sensorineural hearing loss; other features are less common.

Behr syndromeInheritance is AR; heterozygotes may have

mild features.Presentation is in early childhood with

reduced vision.Optic atrophy is diffuse.Prognosis is variable, with moderate to

severe visual loss and nystagmus.Systemic abnormalities include spastic gait,

ataxia and mental handicap.

Wolfram syndromeWolfram syndrome is also referred to as DIDMOAD (diabetes insipidus, diabetes mellitus, optic atrophy and deafness).Inheritance. Three genetic forms are recognized, caused by a variety of mutations in WFS1, which gives Wolfram syndrome 1, CISD2 – Wolfram syndrome 2 – and probably a form caused by a mitochondrial DNA mutation, with inheritance being AR, AD or via the maternal mitochondrial line.

Presentation is usually between the ages of 5 and 21 years; diabetes mellitus is typically the first manifestation, followed by visual problems.

Optic atrophy is diffuse and severe and may be associated with disc cupping.

Prognosis is typically poor (final VA is <6/60).Systemic abnormalities (apart from DIDMOAD)

are highly variable, presumably in part due to genetic heterogeneity, and may include anosmia, ataxia, seizures, mental handicap, short stature, endocrine abnormalities and elevated CSF protein. Life expectancy is usually substantially reduced.

Fig. Hereditary optic atrophy. (A) Bilateral temporal disc pallor;

Fig. (B) bilateral diffuse pallor

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