Vision disorders Notes


Osmosis High-Yield Notes

This Osmosis High-Yield Note provides an overview of Vision disorders essentials. All Osmosis Notes are clearly laid-out and contain striking images, tables, and diagrams to help visual learners understand complex topics quickly and efficiently. Find more information about Vision disorders:

Bitemporal hemianopsia

Color blindness

Cortical blindness


Homonymous hemianopsia

NOTES NOTES VISION DISORDERS GENERALLY, WHAT ARE THEY? PATHOLOGY & CAUSES ▪ Vision deficit disorders ▪ Correlate with anatomical lesions along visual pathway ▫ Light → cornea → lens → media → retina → optic nerve → chiasmal decussation → optic radiations (parietal, temporal paths) → primary visual cortex in occipital lobe DIAGNOSIS OTHER DIAGNOSTICS ▪ History ▪ Physical/neurologic examination ▪ Cranial nerve (CN) testing ▫ CN II: visual fields and acuity ▫ CN II/III: pupillary reflex ▫ CN III/IV/VI: ocular movement TREATMENT CAUSES ▪ Mass effect → impingement of structures ▪ Vascular → brain parenchyma infarction along visual pathway SIGNS & SYMPTOMS MEDICATIONS ▪ Vascular: thrombolytics SURGERY ▪ Masses: resection ▪ Impaired vision OSMOSIS.ORG 683
BITEMPORAL HEMIANOPSIA PATHOLOGY & CAUSES ▪ Visional deficit: lateral vision loss ▫ Optic chiasm lesions (commonly) ▪ Pathogenesis: ↑ sellar mass size → presses optic chiasm → impinges decussating visual fibers (most medial) → bitemporal hemianopsia CAUSES ▪ Pituitary enlargement ▫ Hyperplasia (i.e. pregnancy or lactation); adenoma (specific, hormone-secreting pituitary hyperplasia); cyst; abscess ▪ Craniopharyngioma ▪ Meningioma (in sella turcica) ▪ Saccular aneurysm (anterior communicating artery) ▪ Primary malignancy ▫ Germ cell tumor (AKA ectopic pinealoma); chordoma; central nervous system (CNS) lymphoma COMPLICATIONS ▪ ↑ size → further impinges surrounding structures ▫ Cavernous sinus impingement → CN III, IV, VI → diplopia → ophthalmoplegia ▪ Dorsal extension of mass → dorsal midbrain impingement → Parinaud’s syndrome ▫ Upgaze paralysis ▫ Pinealomas (posterior, common) SIGNS & SYMPTOMS ▪ Vision loss ▫ Lateral fields, both eyes (may go unnoticed; chronic, progressive) ▪ Headache ▪ Diplopia 684 OSMOSIS.ORG ▪ Ophthalmoplegia (especially large mass lesions, pinealomas) ▪ Hormonal deficiency/excess (if pituitary growth is functional) DIAGNOSIS DIAGNOSTIC IMAGING MRI ▪ Visualize mass at area of optic chiasm; gadolinium-enhanced images aid elucidating pituitary tissue (↑ gadolinium uptake in pituitary) CT scan ▪ Less diagnostic; may reveal sellar calcification, mass TREATMENT MEDICATIONS ▪ Smaller, hormone-responsive adenomas (prolactinomas → dopamine agonists firstline therapy) SURGERY ▪ Neurosurgery: nasal aperture, posterior nasopharynx, sublabial (upper lip) incision accesses inferior aspect of cerebrum ▫ Fluoroscopic visualization: navigation, pituitary visualization ▪ First-line therapy for all other pituitary adenomas, sellar masses with meaningful visual field impingement/other symptom severity
Chapter 89 Vision Disorders COLOR BLINDNESS PATHOLOGY & CAUSES ▪ Altered color perception ▪ Pathogenesis ▫ Atypical cone type(s) function → altered color hue → limited color discrimination (commonly) ▫ Optic nerve/other retinal lesions (uncommon) CAUSES Congenital ▪ Three cone types (opsins) ▫ Red, green opsins (X-chromosome): most inherited color blindness X-linked recessive → predominantly biologicallymale individuals ▫ Blue opsin (VII-chromosome): blue wavelength deficiency, very rare ▪ Associated with Turner syndrome Acquired ▪ Optic neuropathies ▫ Optic neuritis: persistent color blindness after visual deficit restoration; early multiple sclerosis symptom ▫ Diabetic retinopathy: neoproliferation, microvascular disease → retinal dysfunction (glaucoma) ▪ Bilateral, ventral occipital stroke → cerebral achromatopsia (rare) SIGNS & SYMPTOMS ▪ Limited color discrimination DIAGNOSIS ▪ Family, medication history OTHER DIAGNOSTICS ▪ Ishihara plates: visual stimuli, colors offer wavelength-specific stimulation for three cone types ▫ Inability to perceive numbers/letters on plate → reveal cone type deficit(s) TREATMENT OTHER INTERVENTIONS ▪ No curative therapy ▪ Acquired disease ▫ Glaucoma: regular eye examinations ▫ Diabetes: glycemic control → ↓ microvascular disease; regular eye examinations ▪ Individual education → lifestyle adaptation → proper visual cue interpretation ▫ Unable to perceive red vs. green light difference on traffic signals → location discrimination education → top vs. bottom light interpretation Iatrogenic ▪ Ethambutol → poor red-green discrimination ▪ Digoxin → yellowish hue disturbance ▪ Other ▫ Ibuprofen, quinine, acetaminophen, sildenafil citrate, tobacco COMPLICATIONS ▪ Nyctalopia: limited night vision OSMOSIS.ORG 685
CORTICAL BLINDNESS PATHOLOGY & CAUSES ▪ Acquired blindness: bilateral lesions to visual cortex in occipital lobe Pathogenesis ▪ Vascular occlusion ▫ Bilateral, distal posterior cerebral artery (PCA) occlusion; commonly embolic ▫ Basilar artery occlusion → ↓ blood flow in bilateral distal PCAs ▪ Vascular flow dysregulation → posterior reversible encephalopathy syndrome (PRES) CAUSES ▪ Primary visual cortex lesions (calcarine fissure in occipital lobe) ▫ Neighboring lesions → similar anopsia COMPLICATIONS ▪ Anton–Babinski syndrome (visual anosognosia) ▫ Individual unable to perceive vision → blindness denial ▫ Image confabulation common SIGNS & SYMPTOMS ▪ Inability to perceive visual input ▪ CN testing: II/III preserved pupillary light reflex 686 OSMOSIS.ORG DIAGNOSIS DIAGNOSTIC IMAGING MRI ▪ Some cases, detects cause (e.g. vascular occlusion, infarction) OTHER INTERVENTIONS History, physical examination ▪ Assess non-cortical functions: normal pupillary light reflex ▫ Limited/no visual response with intact pupillary light reflex → blindness neurological not ocular Fundoscopy ▪ Normal TREATMENT MEDICATIONS ▪ Vascular occlusion: thrombolysis ▪ PRES: emergent antihypertensives OTHER INTERVENTIONS ▪ Spontaneous recovery ▫ Visual defects may persist (e.g. prosopagnosia—inability to recognize faces)
Chapter 89 Vision Disorders HEMIANOPSIA PATHOLOGY & CAUSES ▪ Individual loses half of visual field, commonly due to retrochiasmatic lesion of visual tract Pathogenesis ▪ Vascular ▫ Middle cerebral artery (MCA): complete contralateral hemianopia ▫ Unilateral posterior cerebral artery (PCA): contralateral hemianopia with macular sparing ▪ Mass ▫ Visual pathway compression CAUSES ▪ Unilateral optic tract lesion ▪ Large (complete) unilateral optic radiation lesion ▪ Quadrantanopia: sub-complete lesion, corresponds to lesioned optic radiation ▫ Upper outer-quadrant deficit (“pie-inthe-sky” defect) → temporal lobe loop lesion ▫ Lower inferior quadrant deficit → parietal lobe lesion ▪ Large, unilateral primary visual cortex lesion ▫ Macular visual field spared ▪ Bilateral upper/lower visual cortex lesion → altitudinal hemianopia ▫ Upper/lower field visual defect COMPLICATIONS ▪ Vascular/mass effect territory-dependent ▪ PCA distribution ▫ Diplopia, dizziness, balance issues ▪ Anterior cerebral artery (ACA)/MCA distribution ▫ Ipsilateral motor and sensory symptoms ▪ Parietal lobe involvement → contralateral neglect ▫ Lesion to non-dominant lobe → Gerstmann syndrome (finger agnosia, acalculia, agraphia, right-left visualization) ▪ Temporal lobe involvement → seizure SIGNS & SYMPTOMS ▪ Visual field loss ▫ Unilateral hemianopia: contralateral optic tract lesion (homonymous hemianopia); large, contralateral optic radiation lesion ▫ Superior quadrantanopia: contralateral temporal lobe lesion of optic radiation loop ▫ Inferior quadrantanopia: contralateral parietal lobe lesion of optic radiation loop ▪ Neurologic examination ▫ CN II testing: visual field ▫ Motor/sensory testing for concomitant symptoms DIAGNOSIS ▪ History, physical examination DIAGNOSTIC IMAGING MRI ▪ Mass lesions/old stroke (preferred method) CT scan ▪ Mass lesion and acute, hemorrhagic stroke TREATMENT SURGERY ▪ Resection: mass compressing the visual pathway OSMOSIS.ORG 687
OTHER INTERVENTIONS ▪ Peripheral prism spectacles ▫ High-power prism segments in regular spectacle lens → expands visual field up to 30° ▪ Saccadic eye movement training (scanning therapy) ▫ Individual makes compensatory saccadic eye movements to side with lost visibility without moving head → ↑ function, injury prevention HOMONYMOUS HEMIANOPSIA PATHOLOGY & CAUSES ▪ Lesion in optic tract → vision loss in each eye (corresponding halves of visual field) ▪ Pathogenesis ▫ Vascular: large MCA/smaller anterior choroidal artery stroke ▫ Mass effect: tumor, cyst, arteriovenous malformation (AVM) CAUSES DIAGNOSIS ▪ History, physical examination DIAGNOSTIC IMAGING MRI ▪ Mass lesions/old stroke (preferred method) CT scan ▪ Mass lesion/acute, hemorrhagic stroke ▪ Unilateral optic tract lesion SIGNS & SYMPTOMS ▪ Half of visual field lost ▫ Not relieved by monocular vision (vision deficit persists despite closing one eye) TREATMENT SURGERY ▪ Resection: mass compressing the visual pathway OTHER INTERVENTIONS ▪ Peripheral prism spectacles ▪ Saccadic eye movement training (scanning therapy) 688 OSMOSIS.ORG

Osmosis High-Yield Notes

This Osmosis High-Yield Note provides an overview of Vision disorders essentials. All Osmosis Notes are clearly laid-out and contain striking images, tables, and diagrams to help visual learners understand complex topics quickly and efficiently. Find more information about Vision disorders by visiting the associated Learn Page.