Disorders of Optic Nerve and Gaze Palsies MCQs

Retinal hemorrhages, cotton wool spots, hard exudates and disc edema may be seen in many retinal vascular pathologies. Features characterisitic of each are as follows: Diabetic Retinopathy: Hard exudates and micro-aneurysms involving posterior pole. Malignant Hypertension: Changes centred around disc +/- exudative retinal detachment CRVO: Disc edema plus tortuous veins plus hemorrhages in all 4 quadrants CRAO: Retinal pallor plus cherry red spot at macula Reference: Parson's diseases of the Eye-Chap 18 - Diseases of the Optic Nerve

Capillary hemangioma of the retina is associated with cerebellar and other central nervous system hemangiomas as part of the Von Hippel-Lindau syndrome. Choroidal hemangiomas are seen in Sturge-Weber syndrome. Racemous angiomas of the retina and cavernous hemangiomas of the retina most commonly occur as isolated entities. Reference: Kanski, 8th Edition, Page no. 506.

Posterior ischemic Optic neuropathy This entity shares the features of AION except for the site of involvement. Posterior optic nerve ischaemia is believed to occur due to disorders affecting the small pial vessels which supply the intraorbital portion of the optic nerve away from the eyeball. Reference: Parson's diseases of the Eye-Chap 18 - Diseases of the Optic Nerve

Internuclear ophthalmoplegia: In this condition there is lesion of the medial longitudinal bundle. It is the pathway by which various ocular motor nuclei are linked. Internuclear ophthalmoplegia is characterized by: defective action of medial rectus on the side of lesion, horizontal nystagmus of the opposite eye. Reference: A k Khurana, 5th edition, Pg: 333.

Clinical signs include a variable degree of decreased visual acuity, decreased colour vision, abnormal contrast sensitivity, decreased stereoacuity and visual field defects which could be central, centrocaecal, arcuate, sectorial, altitudinal focal pattern defects or a generalized nonspecific depression in retinal sensitivity. Perimetry shows visual function depression over the entire field but is more marked in the central 20° with varied patterns of field defects. Reference: Parson's diseases of the Eye-Chap 18 - Diseases of the Optic Nerve

By definition, papilloedema is disc oedema due to increased intracranial pressure. An intracranial tumour in any position may induce it. In general, those tumours which tend to produce internal hydrocephalus are most likely to cause papilloedema. The site of the tumour is more important than its nature, size or rate of growth. Other intracranial causes include a brain abscess, thrombosis of the cavernous sinus or other intracranial veins, aneurysm, subarachnoid haemorrhage, pseudotumour cerebri andhydrocephalus. Malignant hypertension can also cause papilloedema, usually by raising the intracranial tension, but may produce signs of disc oedema in the absence of raised intracranial pressure as seen in grade IV hypertensive retinopathy. Reference: Parson's diseases of the Eye 23rd edition-Chap 18 - Diseases of the Optic Nerve

In optic neuritis due to inflammation (papillitis), the appearance of the disc is often ophthalmoscopically indistinguishable from that in papilloedema. The swelling is usually moderate (2-3 D), shelving off gradually into the surrounding retina. Vision in papilledema is normal, but in papillitis it is lost Vitreous opacities are usual, although they may be very fine. The visual symptoms are usually marked in papillitis. The acute depression of central vision, presence of a definite afferent pupillary defect or a relative afferent pupillary defect and the absence of signs of an intracranial space-occupying lesion form the most important differentiating features. Involvement in papillitis is usually unilateral whereas in papilledema it is bilateral. Reference: Parson's diseases of the Eye-Chap 18 - Diseases of the Optic Nerve

Ans. B. Chronic progressive external ophthalmoplegia The most commonidentifiableetiologies are ischemia, aneurysm, tumor and trauma, some 20% remain unexplained.