Optic Atrophy and Neuroretinitis

By Mutahir ShahResident M Phil VS Pakistan Institute of Community OphthalmologyOptic Atrophy and Neuroretinitis

Optic Atrophy:-Introduction Optic atrophy refers to the late stage changes that take place in the optic nerve resulting from axonal degeneration in the pathway between the retina and the lateral geniculate body, manifesting with disturbance in visual function and in the appearance of the optic nerve head. 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.

Primary Optic Atrophy Primary optic atrophy Primary 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 white disc with clearly delineated margins (Fig. 19.7A). 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). 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.

Optic atrophy. (A) Primary due to compression; (B) primary due to nutritional neuropathy note predominantly temporal pallor;

Important causes Optic neuritis. Compression by tumours and aneurysms. Hereditary optic neuropathies. Toxic and nutritional optic neuropathies; these may give temporal pallor, particularly in early/milder cases when the papillomacular fibres are preferentially affected (Fig. 19.7B). Trauma.

Secondary optic atrophy

Secondary 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 white or greyish disc with poorly delineated margins due to gliosis (Fig. C). 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 C), sheathing of arterioles and venous tortuosity may be present.

secondary due to chronic papilloedema note prominent Paton lines

CausesInclude chronic papilloedema, anterior ischaemic optic neuropathy papillitis. Intraocular inflammatory causes of marked disc swelling are sometimes considered to cause secondary rather than consecutive atrophy

Consecutive optic atrophy Consecutive optic atrophy is caused by disease of the inner retina or its blood supply. The cause is usually obvious on fundus examination, e.g. extensive retinal photocoagulation, retinitis pigmentosa or prior central retinal artery occlusion. The disc appears waxy, with reasonably preserved architecture

consecutive due to vasculitis

NeuroretinitisNeuroretinitis refers to the combination of optic neuritis and signs of retinal, usually macular, inflammation. Cat-scratch fever is responsible for 60% of cases. About 25% of cases are idiopathic (Leber idiopathic stellate neuroretinitis). Other notable causes include syphilis, Lyme disease, mumps and leptospirosis.

Diagnosis Symptoms. Painless unilateral visual impairment, usually gradually worsening over about a week. Signs VA is impaired to a variable degree. Signs of optic nerve dysfunction are usually mild or absent, as visual loss is largely due to macular involvement. Papillitis associated with peripapillary and macular oedema (Fig. 19.12A). A macular star (Fig. 19.12B) typically appears as disc swelling settles; the macular star resolves with a return to normal or near-normal visual acuity over 612 months.Venous engorgement and splinter haemorrhages may be present in severe case. Fellow eye involvement occasionally develops.

Progression of neuroretinitis. (A) Severe papillitis; (B) later stage in a different patient showing macular star

Investigation and TreatmentOptical coherence tomography (OCT) demonstrates sub- and intraretinal fluid to a variable extent. Fluorescein angiography (FA) shows diffuse leakage from superficial disc vessels. Blood tests may include serology for Bartonella and other causes according to clinical suspicionTreatment This is specific to the cause, and often consists of antibiotics. Recurrent idiopathic cases may require treatment with steroids and/or other immunosuppressants.

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